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Antimicrobial susceptibility among gram-positive and gram-negative blood-borne pathogens collected between 2012-2016 as part of the Tigecycline Evaluation and Surveillance Trial

Antimicrobial Resistance & Infection Control20187:152

https://doi.org/10.1186/s13756-018-0441-y

  • Received: 7 August 2018
  • Accepted: 20 November 2018
  • Published:

Abstract

Background

Antimicrobial activity of tigecycline and comparator agents was assessedin vitroagainst 27857 isolates source from blood samples collected between 2012 and 2016 as part of the Tigecycline Evaluation and Surveillance Trial (TEST).

Methods

The broth microdilution methods was used to determine  minimum inhibitory concentrations (MIC) of blood-borne isolates according to guildlines of the Clinical and Laboratory Standards Institute (CLSI). Antimicrobial susceptibility breakpoints from CLSI guidelines were used as standards to determine susceptibility against comparator agents, whereas tigecycline breakpoints were provided by the US Food and Drug Administration (FDA).

Results

More than 91% Enterobacteriaceae isolates, belonging to Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacaeandSerratia marcescens, were susceptible to amikacin, meropenem, and tigecycline. Meropenem resistance was observed in 8% ofK.pneumoniae isolates worldwide. Extended-spectrum β-lactamase (ESBL) was produced in 15.9 and 20.9%E.coli and K.pneumoniaeisolates, respectively. MIC90 of tigecycline against Acinetobacter baumannii was 2 μg/ml.  The highest proportion of susceptible A.baumanniiisolates was 70.8% for minocycline. Among P.aeruginose  isolates worldwide, 71.1–94.9% were susceptible to six antibiotics. Almost all Staphylococcus aureusisolates were susceptible to linezolid(100%), vancomycin(100%), and tigecycline (99.9%). The proportion of methicillin-resistant S.aureus (MRSA) was 33.0% among S.aureusisolates worldwide; it was highest in Asia with 46.6%, followed by North America and Latin America with 37.7 and 34.2%, respectively. Vancomycin-resistant (VR) isolates represented 1.4% ofEnterococcus faecalis (VR.E.faecalis) and 27.6% of Enterococcus faecium(VR.E.faecium). Highest percentages of VR.E.faeciumwere found in North America and Latin America, with 61.6 and 58.1% of the isolates, respectively. Production of penicillin-resistant Streptococcus pneumoniae(PRSP) represented 9.0% of S. pneumoniae isolates worldwide; the PRSP proportion was 25.8% in Asia, 13.0% in Africa, and 11.8% in Latin America.

Conclusions

In our study, tigecycline was the only antibiotic that was active against over 90% of all major blood-borne pathogens. A global comparison revealed that antimicrobial resistance was higher in Africa, Asia and Latin America than in Europe and North America.

Keywords

  • Antimicrobial drug resistance
  • Blood
  • Surveillance, tigecycline, Gram-positive bacteria
  • Gram-negative bacteria

Background

Bloodstream infections, acquired in clinics are major cause of mortality in severe disease patients. More attention has been recently paied to bloodstream infections because of the severe effects on health, longer hospital stays, expensive hospitalization costs, and an increase in mortality. In 2013, the incidence of severe sepsis in the United States was approximately 300 cases per 100,000 people associated with a mortality of 20–30% and an expenditure of about $14 billion/year [1].

Importantly, the mortality of bacteremia is directly correlated to the first adequate anti-infectious therapy. In a study on patients of intensive care units (ICU) in Japan,the initiation of an appropriate empirical antimicrobial treatment was associated with a lower 60-day mortality than that of an inappropriate therapy [2]. The selection of an empirical antimicrobial drug therapy should be based on clinical and epidemiological data. Hence, it is important for the clinical treatment of infections to have the information derived from epidemiological data, which differ in scope and focus, i.e., data collected from around the world, different regions,countries, provinces, and hospitals.

The Tigecycline Evaluation and Surveillance Trial (T.E.S.T.), which was initiated in 2004, is a global surveillance study focused on monitoring antimicrobial resistance worldwide. In this study, we report on the antimicrobial susceptibility of Gram-positive bacteria and Gram-negative bacteria isolated from blood specimen collected from around the world between 2012 and 2016.

Methods

Isolate collection

Each participating center was required to contribute at least 135 Gram-negative and 65 Gram-positive isolates per study year (Species and number of isolates: Klebsiella spp.,25; Escherichia coli, 25;Enterobacter spp., 25; Pseudomonas aeruginosa, 20; Acinetobacter spp., 15;Haemophilus influenzae, 15; and Serratia spp., 10; Staphylococcus aureus, 25; Enterococcus spp.,15;Streptococcus pneumoniae,15; and Streptococcus agalactiae,10). Isolates were collected from patients with an infectious disease and identified as the causative agent according to laboratory criteria. One isolate per patient was accepted. All body sites were acceptable for sample collection but the use of urine was limited to not more than 25% of all samples. Stored or duplicate isolates were not acceptable.

Antimicrobial susceptibility testing

Participating centers determined the minimum inhibitory concentrations(MICs) with the broth microdilution assay [3] using MicroScan® panels (Dade MicroScan Inc.,West Sacramento,CA,USA) according to the manufacturer’s instructions. To determine the susceptibility to antimicrobial agents, breakpoints from the Clinical and Laboratory Standards Institute (CLSI) guidelines [4] were used as interpretative standards except for the tigecycline breakpoints, which were obtained from the US Food and Drug Administration(FDA) [5]. The penicillin oral breakpoints (susceptible, ≤0.06 mg/L; resistant,≥2 mg/L) were used for S. pneumoniae.Breakpoint were not available for tigecycline against Acinetobacter baumannii. Methicillin-resistant S.aureus(MRSA) and extended-spectrum β-lactamase(ESBL)-producing E.coli and Klebsiella spp. were identified by the centers according to the CLSI guidelines [4].

The antimicrobials used in this study were listed in Tables 3 and 4. There were an additional four antimicrobials (azithromycin, clarithromycin, erythromycin and clindamycin) included in the panel for testing S.pneumoniae.

Quality control

The reference laboratory, International Health Management Associates(IHMA, Schaumburg, IL, USA), was responsible for the coordination of isolate collection, transport, and backup, as well as the administration of a database. Approximately 10–15% of the isolates were randomly selected each year by IHMA to verify isolate identity and MICs.

Results

Isolate collection

Between 2012 and 2016, 27,857 isolates, including 17,237 Gram-negative (61.9%) and 10,620(38.1%) Gram-positive isolates, were recovered from globally collected blood samples. The major Gram-negative bacteria were E. Coli(n = 5352;19.2%), K.pneumoniae (n = 3154;11.3%),E. cloacae(n = 1824;6.6%), P .aeruginosa(n = 1739;6.2%), S.marcescens (n = 1024;3.7%) and A.baumannii (n=749;2.7%). S.aureus (n = 3324;11.9%), S.pneumoniae (n = 1983;7.1%), E.feacalis (n = 1527;5.5%), E.faecium (n = 1000;3.6%) and S.agalactiae (n = 982;3.5%), were the dominating Gram-positive bacteria.

Europe and North America were the regions with the most participating centers and, therefore,contributed more isolates than the other regions. There were 132 and 54 participating centers collecting 17,456(62.7%) and 6785(24.3%) isolates in Europe and North America,respectively (Table 1). From all patients, 71.5% of the subjects were from non-ICUs and, 70.1% received in-patient treatment. The proportion of subjects of 61-80 years of age was 49.1% (Table 2).
Table 1

Participating centers and collected isolate per world region

Regiona

Number of Centers

Percent of centers (%)

Number of isolates

Percent of isolates (%)

Africa

8

3.4

375

1.4

Asia

29

12.1

1989

7.1

Europe

132

55.2

17,456

62.7

North America

54

22.6

6785

24.3

LatinAmerica

16

6.7

1252

4.5

Total

239

100

27,857

100

aAfrica:= Egypt, Morocco, South Africa, Tunisia; Asia: =China, Kuwait, Hong Kong, India, Japan, Jordan, Saudi Arabia, South Korea, Malaysia, Pakistan, Philippines, Singapore, Taiwan, Thailand, Vietnam; Europe:=Austria, Belgium, Croatia, Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Lithuania, Latvia, Netherlands, Poland, Portugal, Romania, Serbia, Spain, Sweden, Switzerland, United Kingdom; Latin America: = Argentina, Brazil, Chile, Colombia, Mexico, Panama, Guatemala,Venezuela; North American: =Canada, United States

Table 2

Distribution of patients according to location and age

Demographic parameter

Number of patients

Percent of patients(%)

Patient location

 ICUa

5419

19.5

 non-ICU

19,907

71.5

 Unknown

2531

9.1

 In-patient

19,520

70.1

 Out-patient

5806

20.8

 Unknown

2531

9.1

Patient age

 0–20 years

2627

9.4

 21–40 years

2471

8.9

 41–60 years

6507

23.4

 61–80 years

10,901

39.1

  ≥ 81 years

4674

16.8

 Unknown

677

2.4

 Total

27,857

100

aICU= intensive care unit

Antimicrobial susceptibilities of isolates

Enterobacteriaceae

Four species of Enterobacteriaceae were isolated from bloodspecimens, E.coli, K.pneumoniae, E.cloacae, andS.marcescens; most of these isolates (99,91,95, and 96%, respectively)were susceptible to amikacin, meropenem, and tigecycline. The most meropenem-resistant isolates were found inK.pneumoniae, with 8% of resistant isolates globally. A lower proportion of resistant isolates was found in E.cloacae, S.marcescens, and E.coli, with only 1.6,1.6, and 0.4% of the isolates, respectively. There were large differences in the occurrence of meropenem-resistantK.pneumoniae, which was highest in Africa (15.4%), followed by Europe, Asia, and Latin America (12.1,10.5, and 8.4%, respectively), and lowest in North America (2%) (Table 3, Fig. 1).
Table 3

Antimicrobial susceptibility among Gram negative isolates including ESBL-producing strains from blood specimens collected between 2012 and 2016

 

Africa

Asia

Europe

North America

Latin America

Global

Global

S%

S%

S%

S%

S%

MIC90(mg/L)

MIC range(mg/L)

S%

R%

MIC90(mg/L)

MIC range(mg/L)

S%

R%

 

E.coli

E.coli, all isolates

E.coli ESBL isolates

N = 47

N = 396

N = 3235

N = 1487

N = 187

N = 5352

N = 852

Amikacin

97.9

97.7

99.5

99.9

98.9

4

0.5–128

99.4

0.2

8

0.5–64

98.4

0.2

Amoxy/clav

48.9

72.0

70.1

78.1

64.7

32

0.25–64

72.1

10.1

32

0.5–64

48.6

14.4

Ampicillin

12.8

18.4

32.8

43.4

26.2

64

0.5–64

34.3

65.0

64

1–64

0.6

99.4

Cefepime

57.5

59.6

82.0

88.8

73.8

16

0.5–64

81.8

13.1

64

0.5–64

13.9

64.7

Ceftazidime

63.8

70.0

86.5

91.6

79.1

8

1–32

86.3

9.4

32

1–32

35.3

42.7

Ceftriaxone

48.9

49.8

78.8

87.4

67.4

64

0.06–64

78.4

21.0

64

0.06–64

0.9

97.8

Levofloxacin

51.1

48.0

64.9

71.6

58.8

16

0.008–16

65.2

31.9

16

0.008–16

16.3

78.9

Meropenem

95.7

98.2

99.9

99.7

97.3

0.06

0.06–32

99.6

0.4

0.12

0.06–16

99.5

0.4

Minocycline

74.5

83.3

85.9

91.3

81.8

8

0.5–32

87.0

7.4

8

0.5–32

86.0

7.3

Pip/taz

80.9

95.0

92.7

97.4

94.4

8

0.06–256

94.1

3.2

16

0.06–256

91.2

4.5

Tigecycline

100

100

99.9

99.9

100

0.25

0.008–16

99.9

0.04

0.5

0.008–2

100

0.0

 

K.pneumoniae

K.pneumoniae, all isolates

K.pneumoniae ESBL isolates

N = 52

N = 276

N = 1761

N = 899

N = 166

N = 3154

N = 659

Amikacin

84.6

90.2

96.7

99.4

96.4

8

0.5–128

96.7

1.8

16

0.5–128

95.8

2.7

Amoxy/clav

25.0

66.7

60.8

90.9

59.0

64

0.12–64

69.2

18.8

64

2–64

19.6

40.2

Ampicillin

1.8

2.2

2.6

6.2

1.2

64

0.5–64

3.5

85.1

64

16–64

0

99.9

Cefepime

34.6

66.7

65.0

93.3

57.2

64

0.5–64

72.3

23.4

64

0.5–64

8.4

78.0

Ceftazidime

34.6

69.2

67.0

91.2

68.7

32

1–32

73.6

21.7

32

1–32

18.1

65.0

Ceftriaxone

21.2

62.7

62.5

90.6

54.2

64

0.06–64

69.4

29.8

64

0.06–64

1.8

97.3

Levofloxacin

57.7

76.5

70.8

91.4

80.7

16

0.008–16

77.5

18.7

16

0.03–16

40.5

47.7

Meropenem

84.6

89.5

87.9

98.0

91.6

1

0.06–32

91.1

8.0

8

0.06–32

84.8

11.7

Minocycline

71.2

83.3

78.6

87.5

83.7

16

0.5–32

81.7

11.5

16

0.5–32

70.3

18.2

Pip/taz

55.8

80.8

76.7

94.1

77.1

256

0.06–256

81.7

15.0

256

0.5–256

59.6

29.1

Tigecycline

96.2

93.1

94.4

95.6

97.6

2

0.008–16

94.8

0.7

2

0.008–16

90.4

1.2

 

S.marcescens

 

N = 29

N = 88

N = 591

N = 224

N = 92

N = 1024

 

Amikacin

100.0

96.6

99.0

100.0

85.9

4

0.5–128

97.9

0.9

    

Amoxy/clav

0.0

8.0

3.1

1.3

3.3

64

0.5–64

3.0

92.4

    

Ampicillin

0.0

6.8

6.3

4.0

4.4

64

0.5–64

5.5

87.3

    

Cefepime

89.7

85.2

96.6

98.7

80.4

1

0.5–64

94.4

3.8

    

Ceftazidime

96.6

88.6

96.1

98.2

87.0

2

1–32

95.1

3.8

    

Ceftriaxone

89.7

79.6

85.3

88.0

71.7

4

0.06–64

84.3

11.8

    

Levofloxacin

100.0

94.3

95.8

96.0

89.1

1

0.008–16

95.2

2.9

    

Meropenem

96.6

95.5

99.0

99.1

93.5

0.25

0.06–32

98.1

1.6

    

Minocycline

100.0

88.6

90.4

94.2

88.0

4

0.5–32

91.9

2.3

    

Pip/taz

100.0

89.8

94.1

97.3

90.2

8

0.06–256

94.2

2.4

    

Tigecycline

96.6

95.5

97.0

97.8

93.5

2

0.03–16

96.7

0.3

    
 

E.cloacae

 

N = 47

N = 157

N = 1084

N = 404

N = 132

N = 1824

 

Amikacin

95.7

96.8

99.0

100.0

97.0

4

0.5–128

98.8

0.9

    

Amoxy/clav

2.1

1.9

3.7

3.0

1.5

64

0.12–64

3.2

95.4

    

Ampicillin

4.3

3.2

6.8

4.5

4.6

64

0.5–64

5.8

89.5

    

Cefepime

51.1

76.4

77.2

86.9

74.2

16

0.5–64

78.4

12.0

    

Ceftazidime

51.1

63.1

65.0

74.5

65.9

32

1–32

66.7

29.6

    

Ceftriaxone

40.4

59.2

59.7

70.5

60.6

64

0.06–64

61.6

36.2

    

Levofloxacin

91.5

87.9

85.8

94.6

86.4

4

0.008–16

88.1

9.8

    

Meropenem

100.0

94.3

97.2

99.5

97.7

0.25

0.06–32

97.6

1.6

    

Minocycline

85.1

84.1

86.0

86.9

88.6

8

0.5–32

86.2

8.2

    

Pip/taz

78.7

75.2

76.3

81.7

79.6

128

0.06–256

77.7

11.5

    

Tigecycline

95.7

96.8

95.4

95.5

97.0

2

0.008–16

95.7

0.8

    
 

P.aeruginosa

 

N = 29

N = 150

N = 1081

N = 387

N = 95

N = 1739

    

Amikacin

96.6

95.3

94.3

97.9

88.4

8

0.5–128

94.9

2.7

    

Cefepime

65.5

76.0

75.5

86.3

85.3

16

0.5–64

78.4

9.1

    

Ceftazidime

79.3

77.3

78.8

88.9

82.1

32

1–32

81.1

11.4

    

Levofloxacin

86.2

82.7

72.4

76.5

75.8

16

0.015–16

74.6

19.8

    

Meropenem

75.9

69.3

69.6

75.7

69.5

16

0.06–32

71.1

22.0

    

Pip/taz

82.8

78.0

78.3

86.8

85.3

64

0.12–256

80.7

7.9

    
 

A.baumannii

    

N = 32

N = 123

N = 424

N = 118

N = 52

N = 749

    

Amikacin

31.3

43.1

37.0

74.6

28.9

128

0.5–128

43.1

49.1

    

Cefepime

12.5

27.6

24.1

54.2

15.4

64

0.5–64

28.3

65.7

    

Ceftazidime

15.6

35.0

27.1

50.0

23.1

32

1–32

31.2

64.2

    

Ceftriaxone

9.4

22.8

16.0

31.4

11.5

64

0.06–64

19.0

67.0

    

Levofloxacin

21.9

30.9

23.6

51.7

15.4

16

0.008–16

28.6

61.7

    

Meropenem

25.0

26.8

26.9

60.2

15.4

32

0.06–32

31.2

66.8

    

Minocycline

81.3

73.2

61.8

89.0

90.4

8

0.5–32

70.8

8.8

    

Pip/taz

12.5

26.0

24.5

52.5

13.5

256

0.06–256

27.9

68.2

    

Tigecycline

     

2

0.008–4

      

Abbreviations: S% percentage of susceptible isolates, R% percentage of resistant isolates, MIC minimum inhibitory concentration, Amoxy/clav Amoxicillin/clavulanic acid, Pip/taz Piperacillin/tazobactam

Fig. 1
Fig. 1

Distribution of multi-drug resistant (MDR) bacteria among isolates from blood specimen collected in various international regions. Percent on every column indicates percentage of resistant isolates in each region for each organism. ESBL, extended-spectrum β-lactamase; CARB-NS, cabapanem non-susceptibility; MRSA, methicillin-resistant S. aureus; VR, vancomycin resistant; PRSP, Penicillin-resistant S. pneumoniae

Susceptibility to cephalosporins(ceftriaxone,ceftazidime, and cefepime) was found in 78.4–86.3%, 69.4–73.6%, 61.6–78.4%, and 84.3–95.1% of isolates ofE.coli, K.pneumoniae, E.cloacae, and S.marcescens, respectively. The most cephalosporin-susceptible organism was S.marcescens,whereas K.pneumoniae and E.cloacaewere less susceptible. In the four species of Enterobacteriaceae, E.coli, K.pneumoniae, E.cloacae, and S.marcescens, susceptibility to piperacillin/tazobactam(pip/taz) and amoxicillin/clavulanic acid(amoxy/clav) was found in 94.1%/72.1, 81.7%/69.2, 77.2%/3.2, and 94.2%/3.0% of the isolates, respectively. The in vitro activity of pip/taz was lower against K. pneumoniae and E. cloacae than E. coli and S .marcescens. The activity of amoxy/clav against E. coli and K. pneumoniae was weak as compared to that of pip/taz, and it had almost no effect on E. cloacae and S. marcescens (Table 3).

Minocycline was more active against the four Enterobacteriaceae with a similar susceptibility in 87.0, 81.7, 86.2, and 91.7% of the isolates of E. coli, K .pneumoniae, E .cloacae,and S. marcescens,respectively. The activity of levofloxacin was lowest against E. coli(65.2%) and highest against S. marcescens(95.2%) (Table 3).

ESBL production was found in 15.9% of E. coli and 20.9% of K. pneumoniae isolates. Africa had the highest proportion of ESBL-producers, with 40.4%(19/47) and 55.8%(29/52) of E. coli and K. pneumoniae isolates, respectively, followed by Latin America(23.0%,43/187), Asia(22.7%,90/396), Europe(17.2%,555/3235), and North America(9.8%,145/1487) in E. coli,as well as Latin America(37.4%,62/166), Europe (26.2%,462/1761), Asia (16.3%,45/276), and North America(6.8%,61/899) in K. pneumoniae (Fig. 1).

Susceptibility to amikacin, meropenem, and tigecycline was found in more than 98.4% of ESBL-producing E. coli isolates, as well as in 95.8,84.8 and 90.4% of ESBL-producing K.pneumoniae isolates, respectively. Over than 86% of ESBL-producing E. coli isolates were susceptible to pip/taz and minocycline,but only 59.6–70.3% of ESBL-producing K. pneumoniae. Susceptibility to other antibiotics was observed in less than 50% of Enterobacteriaceae isolates (Table 3).

A. baumannii and P. aeruginosa

Antibiotics exhibited a very poor activity against A. baumannii. The most active antibiotic was minocycline; 70.8% of A. baumannii isolates were susceptible. Susceptibility to meropenem was found in 31.2% of the isolates. The MIC90 of tigecycline was 2 μg/ml (Table 3).

Amikacin was the most active antibiotic in P. aeruginose, i.e., 94.9% susceptible isolates. Susceptibility to ceftazidime and pip/taz was found in over 80% of the isolates. Susceptibility to other antibiotics was confirmed for over 70% of the isolates (Table 3).

S. aureus

Almost all S. aureus isolates were susceptible to linezolid(100%), vancomycin(100%), and tigecycline(99.9%). The isolates were also highly susceptible to minocycline (98.8%). The lowest susceptibility in S. aureus was observed for penicillin; only14.7% of susceptible isolates (Table 4). Moreover, the proportion of MRSA was 33.0% globally; it was highest in Asia with 46.6%, followed by North America(37.7%) and Latin America (34.2%), whereas the MRSA percentage was lower in Africa(32.6%) and Europe(28.9%) (Fig. 1).
Table 4

Antimicrobial susceptibility among Gram-positive isolates including multi-drug resistance(MDR) strains from blood specimens collected between 2012 and 2016

 

Africa

Asia

Europe

North America

Latin America

Global

Global

S%

S%

S%

S%

S%

MIC90(mg/L)

MIC range(mg/L)

S%

R%

MIC90(mg/L)

MIC range(mg/L)

S%

R%

 

S.aureus

S.aureus, all isolates

MRSA

N = 43

N = 298

N = 2008

N = 814

N = 161

N = 3324

N = 1096

Levofloxacin

65.1

57.4

69.3

67.3

77.0

16

0.06–64

68.1

30.2

64

0.06–64

21.9

75.6

Linezolid

100.0

100.0

100.0

100.0

100.0

2

0.5–4

100.0

0.0

2

0.5–4

100.0

0.0

Minocycline

83.7

97.3

99.5

98.3

100.0

0.25

0.25–16

98.8

0.1

0.5

0.25–16

97.5

0.1

Penicillin

2.3

6.0

15.9

16.6

8.1

16

0.06–16

14.7

85.4

16

0.12–16

0.1

99.9

Tigecycline

100

99.7

100.0

100.0

100.0

0.12

0.008–1

99.9

0.0

0.25

0.015–1

99.9

0.0

Vancomycin

100.0

100.0

100.0

100.0

100.0

1

0.12–2

100.0

0.0

1

0.12–2

100.0

0.0

 

E.faecalis

E.faecalis, all isolates

VR E.faecalis

N = 26

N = 99

N = 910

N = 406

N = 86

N = 1527

N = 22

Ampicillin

100.0

96.0

98.9

99.8

96.5

1

0.06–32

98.8

1.2

32

0.5–32

86.4

13.6

Levofloxacin

69.2

70.7

68.6

73.4

81.4

64

0.06–64

70.7

28.5

64

0.5–64

13.6

86.4

Linezolid

100.0

97.0

100.0

100.0

97.7

2

0.5–8

99.7

0.1

2

0.5–2

100.0

0.0

Minocycline

30.8

35.4

36.8

35.2

38.4

8

0.25–16

36.3

6.3

8

0.25–8

27.3

0.0

Penicillin

100.0

95.0

98.8

99.8

96.5

4

0.06–16

98.7

1.3

16

2–16

86.4

13.6

Tigecycline

100.0

100.0

99.9

100.0

100.0

0.12

0.008–0.5

100.0

0.0

0.12

0.03–0.12

100.0

0.0

Vancomycin

96.2

98.0

99.0

96.6

98.8

2

0.12–64

98.2

1.4

64

32–64

0.0

100.0

 

E.faecium

E.faecium, all isolates

VR E.faecium

N = 9

N = 89

N = 603

N = 268

N = 31

N = 1000

N = 276

Ampicillin

11.1

12.4

11.1

14.2

6.5

32

0.06–32

11.9

88.1

32

4–32

0.7

99.3

Levofloxacin

22.2

9.0

9.8

12.3

12.9

64

0.06–64

10.6

87.0

64

8–64

0.0

100.0

Linezolid

100.0

100.0

99.7

98.8

100.0

2

0.5–8

99.5

0.2

2

0.5–8

98.9

0.4

Minocycline

88.9

47.2

70.2

59.0

80.7

8

0.25–16

65.6

6.2

8

0.25–16

58.7

6.2

Penicillin

11.1

14.6

13.1

12.7

6.5

16

0.06–16

12.9

87.1

16

4–16

1.5

98.6

Tigecycline

100.0

100.0

99.5

98.9

100.0

0.12

0.008–1

99.4

0.0

0.12

0.008–1

98.9

0.0

Vancomycin

66.7

78.7

87.1

38.1

41.9

64

0.12–64

71.6

27.6

64

32–64

0.0

100.0

 

S.pneumoniae

S.pneumoniae, all isolates

PR S.pneumoniae

N = 23

N = 66

N = 1248

N = 553

N = 93

N = 1983

N = 178

Amoxy/clav

91.3

95.5

98.0

96.2

93.6

1

0.03–16

97.1

1.1

8

0.03–16

68.5

11.8

Azithromycin

69.6

38.1

81.1

63.0

44.6

64

0.03–512

72.7

26.0

128

0.03–512

28.7

69.0

Ceftriaxone

100.0

94.0

98.7

99.0

98.9

0.5

0.03–8

98.6

0.1

2

0.03–8

86.0

1.1

Clarithromycin

69.6

39.7

80.9

63.0

69.6

128

0.015–128

73.9

26.0

128

0.015–128

30.5

69.0

Clindamycin

78.3

61.9

85.3

87.4

79.4

128

0.015–128

84.7

14.8

128

0.015–128

53.5

45.4

Erythromycin

69.6

39.7

80.8

63.6

69.6

64

0.015–128

74.0

25.8

128

0.015–128

29.9

69.0

Levofloxacin

100.0

98.5

99.6

99.6

98.9

1

0.06–16

99.6

0.4

1

0.12–16

99.4

0.6

Linezolid

100.0

100.0

100.0

100.0

100.0

1

0.5–2

100.0

0.0

1

0.5–2

100.0

0.0

Meropenem

81.0

60.6

89.7

87.0

86.0

0.5

0.12–8

87.8

7.1

1

0.12–8

3.4

70.8

Minocycline

73.9

37.9

77.5

83.7

69.9

4

0.25–16

77.5

16.8

8

0.25–16

46.1

45.0

Penicillin

69.6

34.9

70.4

69.8

55.9

1

0.06–16

68.3

9.0

4

2–16

0.0

100.0

Tigecycline

100.0

98.5

99.8

99.5

100.0

0.03

0.008–4

99.7

0.0

0.03

0.008–0.12

100.0

0.0

Vancomycin

100.0

100.0

100.0

100.0

100.0

0.5

0.12–1

100.0

0.0

0.5

0.12–1

100.0

0.0

 

S.agalactiae

 

N = 8

N = 64

N = 505

N = 373

N = 32

N = 982

 

Ampicillin

100.0

100.0

100.0

100.0

100.0

0.12

0.06–0.25

100.0

0.0

    

Ceftriaxone

100.0

100.0

100.0

100.0

100.0

0.12

0.03–0.5

100.0

0.0

    

Levofloxacin

100.0

95.3

98.2

96.5

87.5

1

0.06–64

97.1

2.7

    

Linezolid

100.0

100.0

100.0

100.0

100.0

1

0.5–2

100.0

0.0

    

Meropenem

100.0

100.0

100.0

100.0

100.0

0.12

0.12–0.5

100.0

0.0

    

Minocycline

12.5

20.3

17.8

22.0

50.0

16

0.25–16

20.6

62.7

    

Penicillin

100.0

100.0

100.0

100.0

100.0

0.12

0.06–0.12

100.0

0.0

    

Tigecycline

100.0

96.9

99.8

100.0

100.0

0.06

0.008–4

99.7

0.0

    

Vancomycin

100.0

100.0

100.0

100.0

100.0

0.5

0.12–1

100.0

0.0

    

Abbreviations: S% percentage of susceptible isolates, R% percentage of resistant isolates, MIC minimum inhibitory concentration, Amoxy/clav Amoxicillin/clavulanic acid

E. faecalis and E. faecium

In this study, E. faecalis was susceptible to five (penicillin, ampicillin, tigecycline, linezolid, and vancomycin) out of seven antibiotics at a rate of ≥98%. The susceptibility of E. faecium was 99.4 and 99.5% to tigecycline and linezolid, respectively, but only 12.9 and 11.9% to penicillin and ampicillin, respectively. The susceptibility of E. faecium to vancomycin was 71.6, and 70.7% of E. faecalis and 10.6% of E .faecium isolates were susceptible to levofloxacin. Further, 36.3% of E. faecalis and 65.6% of E.faecium isolates were susceptible to minocycline (Table 4).

The isolate rates of vancomycin-resistant E. faecalis(VR E. faecalis) and E. faecium(VR E. faecium) were 1.4 and 27.6%, respectively. Most VR E. faecium isolates were collected in North America and Latin America with isolate rate of 61.6 and 58.1%, respectively (Fig. 1). Tigecycline and linezolid were active against 98.9% of VR E. faecium.

S. pneumoniae

No linezolid- or vancomycin-resistant isolates were found in our study. Over than 97% susceptibility was observed for tigecycline, levofloxacin, ceftriaxone, and amoxy/clav. Susceptibility to clindamycin was 84.7%, which was higher than that to macrolides, including erythromycin,clarithromycin and azithromycin with similar susceptibility(72.7–74.0%). Meropenem and minocycline were active in 87.8 and 77.5% of the isolates, respectively (Table 4).

The lowest susceptibility among all antibiotics was observed for penicillin with 68.3% of susceptible isolates. The global rate for penicillin-resistant S. pneumoniae (PRSP) isolates was 9.0% in globally; regionly, it was 25.8% in Asia,13.0% in Africa,11.8% in Latin America, 9.6% in North America and 7.5% in Europe (Fig. 1).The activity of many antibiotics decreased in PRSP. The rate of isolates susceptible to macrolides decreased to 28.7–30.5% and clindamycin, meropenem, and minocycline were reduced to 53.5, 3.4 and 46.1%, respectively. However, 100% susceptibility was observed for linezolid, vancomycin, tigecycline, and levofloxacin (Table 4).

S. agalactiae

The proportion of antimicrobial-susceptibleS. agalactiae isolates was higher than 97%, except for minocycline with 20.6% of susceptible isolates. A susceptibility of 100% was found for penicillin, ampicillin, linezolid, meropenem, and vancomycin (Table 4).

Variations insusceptibility between the major world regions

Antibiotics with a global susceptibility rate of less than 90% were selected and the ones with the lowest susceptibility rate in two regions were marked. The occurrence of each region due to the marked antibiotics reflected the situation of antimicrobial resistance in this region (Table 5). Africa was the region with the most occurrences of marked antibiotics, 38 times and at the proportion of 34.2%, followed by Latin America (27,24.3%) and Asia(26,23.4%). The proportion was less than 12% for Europe and North America.
Table 5

Occurrence of every regions with low susceptibility to antibiotics in major blood-borne pathogens (%)

bacterial

number of antibioticsa × 2

Africa

Asia

Europe

North America

Latin America

E. coli

14

7 (50.0)

4 (28.6)

0 (0.0)

0 (0.0)

3 (14.3)

K .pneumoniae

16

8 (50.0)

0 (0.0)

3 (18.8)

0 (0.0)

5 (31.3)

S. marcescens

6

2 (33.1)

1 (16.7)

0 (0.0)

2 (33.3)

1 (16.7)

E. cloacae

16

5 (31.3)

6 (37.5)

2 (12.5)

0 (0.0)

3 (18.8)

P. aeruginosa

10

1 (10.0)

3 (30.0)

4 (40.0)

0 (0.0)

2 (20.0)

A. baumannii

16

7 (43.8)

1 (6.3)

1 (6.3)

0 (0.0)

7 (43.8)

S. aureus

4

2 (50.0)

2 (50.0)

0 (0.0)

0 (0.0)

0 (0.0)

E. faecalis

4

2 (50.0)

0 (25.0)

1 (25.0)

1 (25.0)

0 (0.0)

E. faecium

11b

2b(18.2)

2 (18.2)

2b(18.2)

2 (18.2)

3 (27.3)

S. pneumoniae

14

2 (14.3)

7 (50.0)

0 (0.0)

2 (14.3)

3 (21.4)

Total

111

38 (34.2)

26 (23.4)

13 (11.7)

7 (6.3)

27 (24.3)

a There were antibiotics with a global susceptibility of less than 90%

b Same susceptibility in Africa and Europe of ampicillin to E. faecium

Discussion

Bacteria isolated from blood are typically the causative agents for a circulatory system infection or a local infection(e.g., the special respiratory system) [6], and they often indicate poor prognosis [7]. Therefore, bacteria isolated from blood are important for physicians and studies on pathogenic bacteria and their resistance to antibiotics have a great practical significance and a high clinical value.

Bacterial species isolated from blood specimens in our study were common pathogens of community-acquired and hospital-acquired bloodstream infection [8, 9]. The patients were mostly from non-ICU departments and had the highest proportion in elderly patients 61–80 years of age. A surveillance program performed for 18 years by a large hospital of Malawi in Africa pathogens from bloodstream infections [8] found that the organisms causing differed with the age. Except for children below 4 years of age, bacterial infections were likely to be caused by Salmonella typhimurium, Salmonella enteritidis,S. pneumoniae, and yeast in adults of less than 60 years old of age. Morbidity in bloodstream infections caused by Enterobacteriaceae(such as E. coli or K. pneumoniae) and S. aureus increased with the age and occurred most frequently in elderly people ≥60 years old of age. In this investigation,the proportion of Enterobacteriaceae and S. aureus was 52.7% and the trend of the occurrence of the infection increased with age; these observations are in agreement with the findings in the study from Africa.

The high activities determined for amikacin, meropenem, and tigecycline against Enterobacteriaceae from blood samples in our study indicated that these antibiotics can be used as the first choice in the empirical treatment of clinical bloodstram infections caused by Enterobacteriaceae.

Low in vitro activity was observed for cephalosporin and pip/taz against K. pneumonia. ESBL production was higher in K. pneumoniae than in E. coli (20.9% vs. 15.9%). Meropenem resistance found globally in 8% of K. pneumoniae, far exceeds that in other Enterobacteriaceae. These results indicated that the lower activity of cephalosporins and pip/taz against K. pneumoniae is related to the production of ESBL and carbapenemases.

ESBL was the main reason for E. coli and K. pneumoniae resistance against the third and fourth generation of cephalosporins because of the hydrolytic activity [10]. Production of ESBL monitored by many large disease surveillance organizations. In this study, the production of ESBL in E. coli and K. pneumoniae were 22.7%/16.3%, 23.0%/37.4% and 9.8%/6.8% in Asia, Latin America, and North America, respectively. The data from the 2011–2014 SENTRY surveillance, ESBL in E. coli and K. pneumoniae in Asia-Pacific [11], Latin America [12], and the USA [13] were 60%/47%,37.7%/57.3%, and 11.1%/20.4%, respectively, which was higher than the data in our study. In a meta- analysis from West Africa [14], ESBL in E. coli and K. pneumoniae were11.9 and 24.2%, respectively, which was less than 40.4 and 55.8% in our study. In a report of the TEST study between 2004 and 2013 [15], ESBL of E. coli and K. pneumoniae were 14.0 and 20.4% globally, similar to 15.9 and 20.9%, respectively, in our study. Different procedures implemented by different organizations involved in various surveillance programs lead to disparities in surveillance data specific for each region. It is critical to organize very active surveillance stations and collect accurate data to assess the true status of antimicrobial resistance in a local area.

Carbapenemases cause carbapenem resistance in Enterobacteriaceae [16]. K. pneumoniae carbapenemases(KPC) and metallo-β-lactamases(MBL)are common epidemic carbapenemases. KPC is reportedly prevalent in Latin-America, Europe and the Middle-East and the MBL is also prevalent in Europe and Asia [16]. No article has mentioned an increase of carbapenemases in Africa, but we found the highest rate of non-susceptibility to carbapenem(15.4%) in Africa. The number of participating centers and the collected strains were minimal in Africa(8 centers; 47E. coli and 52 K. pneumoniae isolates) as compared to other regions. There is a high probability that specific data by a single center can lead to a resistance rate increase that is not representative for the entire continent. Another reason was that we could not acquire correct information is the rarity of reports from Africa. To enhance the surveillance of bacterial resistance in developing regions is imperative for future infectious disease management. Non-susceptibility of meropenem against K. pneumoniae was 8.4 and 10.5% in Latin America and Asia, respectively, in our study, which is similar to the results of SENTRY [11, 12]. However, there is a large difference between our data for North America(2.0%) and the SENTRY data for this region (10.8%) [13].

Similar results were obtained on the susceptibility of cephalosporins and pip/taz to E. cloacae comparing our results to the SENTRY report [12]; 61.6–78.4% of cephalosporin-susceptible E. cloacae indicated the prudent use of cephalosporins in E. cloacae bacteremia. The results of our antimicrobial susceptible tests should be used as a reference. For S. marcescens bacteremia, there are several antibiotics available for empirical antibiotic treatment.

High in vitro activity was observed for minocycline against Enterobacteriaceae, but it was lower against ESBL-producing K. pneumoniae. Poor levofloxacin susceptibility exists in E. coli and K. pneumoniae (65.2 and 77.5%, respectively), which is worse in ESBL-producing E. coli and K. pneumoniae(16.3 and 40.5%, respectively),but better in E. cloacae and S. marcescens(88.1 and 95.2%, respectively). Thus, levofloxacin could be used to treat bacteremia caused by E. cloacae or S. marcescens, but not in bacteremia caused by E. coli or K. pneumoniae.

Susceptibility to carbapenem in A.baumannii has also been closely monitored. Consistency has been demonstrated by a 31.2% of susceptibility in this investigation and less than 30% from SENTRY [12] and SMART [17] in Latin America. The clinical effect of carbapenem against A. baumannii is very limited because the epidemic caused by the global emergence of multi-drug resistant(MDR) isolates. The separation rate of MDR A. baumannii between 2004 and 2014 was calculated by Anna et al. [18]. The result was 44.3% globally and up to 60–70% in Latin America, Middle-East, and Africa. Strong resistance is challenging for clinical disease management. The emergence of MDR A. baumannii in bloodstream infections significantly increased the mortality in patients [19]. Only minocycline has a better activity against A. baumannii in our study(70.8% susceptible isolates), which was similar to that in the SENTRY report (79.1%) [20]. The meta-analysis by Lashinskyet al. [21] on several clinical investigations found that the treatment success rate of minocycline single and combination on A. baumannii was 78.2%,verifying the recommendation to use minocycline treatment for an infection caused by A. baumannii.

The susceptibility for six antibiotics by P. aeruginosa were 71.1–94.9% globally, and 66.7–91.7% and 54.4–75.4% in Asia and Latin America, respectively, which was higher than TEST result (63.9–90.2%) of 2004–2013 [15] for all specimen globally collected, and the SENTRY result for Asia-Pacific(66.7–91.7%) [11] and Latin America(54.4–75.4%) [22] in 2011. P. aeruginose isolated from blood may be more susceptible to common antibiotics than the specimens collected from other body sites.

Best in vitro activity was found for linezolid, vancomycin, tigecycline and minocycline against S. aureus. Very poor penicillin-susceptibility was observed for S. aureus, only 14.7%, which was in accordance with several other investigations [15, 23]. The rate of 33.0% MRSA isolates in globally of our study agreed with 40.2% in the TEST report for 2004–2013 [15]. The isolate rates of MRSA in Asia-Pacific [11], Latin America [12], and the USA [13] were 37,44.7, and 53.1% in the SENTRY surveillance report. In a comparison with our study, the rate for the USA was higher than that for North America(37.7%), whereas the Asia-Pacific rate was lower than the Asia rate (46.6%). A meta- analysis on S. aureus in Africa summarized by Matthew [24] found <50% separation of MRSA, which is a smaller difference to our study. Further, 21.2% isolation of MRSA by the EARS-Net surveillance network in Europe is close to 28.9% in our study.

In our investigation, the susceptibility to primary drugs was significantly lower in E. faecium than in E. faecalis,except for linezolid, tigecycline and minocycline. High resistance levels are a complication during infection treatment. Resistance to vancomycin was significantly higher in E. faecium (27.6%) than in E. faecalis(1.4%). In VR E. faecium, it increased to 61.6 and 58.1% in North America and Latin America, respectively, which is in accordance with the result for the USA (74.7%)[13] and Latin America(50.3%) [12] in the SENTRY surveillance report.

The global occurrence rate of PRSP was 9.0%, and 25.8,13.0,11.8,7.5, and 9.6% in Asia, Africa, Latin America, Europe, and North America, respectively, which was lower than the TEST data from 2009 to 2012(14.4% globally; and 33.1,32.3,15.1,10.1, and 16.3% in the respective regions) [25]. The difference may be linked to the source specimens used for recovering the isolates. Isolates from blood may be more susceptible than these from other body sites. The same situation may apply to other antibiotics. Susceptilbility to macrolides, clindamycin, meropenem and minocycline was 47.5–47.9, 70.2, 83.4, and 51.7%, respectively, in the TEST study from 2009 to 2012 [25], which was significantly less than these in our study. The resistance is higher against many antibiotics in PRSP as compared to that in S. pneumoniae, which has been verified by other investigations [26]. The highest activity was determined for linezolid, vancomycin, tigecycline, and levofloxacin irrespective of the resistance against penicillin.

Many research groups investigated and monitored the emergence of macrolide resistance in S.agalactiae. A resistance level of even less than 20% is serious for S.agalactiae, which is still susceptible to almost all antibiotics [27, 28]. It is very unfortunate that we did not detect the activity of macrolides in our study. S. agalactiae is fully susceptible to penicillin, which is critical for decolonization management in pregnant women and infections in other patients. However, the resistance to penicillin is emerging. In a study on S.agalactiae isolates from 2012 by Crespo et al. [28], 2% of penicillin-resistant S. agalactiae were detected. The mechanism of penicillin resistance in S.agalactiae is related to changes in penicillin-binding proteins(PBPs) [29], based on an investigation of resistant strains isolated from cattle.

Tigecycline has the highest in vitro activity against bacteria recovered from blood. Susceptibility to tigecycline in Gram-positive bacteria, including MRSA, VR E. faecalis, and PRSP, was above 99.4, except for VR E. faecium (98.9%). In Gram-negative bacteria, the susceptibility was high in E. coli, and more than 95% in S. marcescens and E. cloacae, but lower in K. pneumoniae(94.8%) and ESBL-producing K. pneumoniae(90.4%). Tigecycline was the only antibiotic with over 90% susceptibility in all major pathogens(except for P.aeruginosa because of its natural resistance) isolated from blood. High susceptibility values and the difference in various organisms were similar in the SENTRY report from 2016 [30], indicating the reliability of our results and the stability in the efficacy of tigecycline.

The data in Table 5 show that Africa, Asia and Latin America have a serious problem with antimicrobial resistance. There is a higher probability for the people in these regions that they have acquired an antibiotic-resistant organism if they fall ill with a bloodstream infection. Both difficult clinical management and high mortality increase the hardship. Hence, it is imperative to implement rational usage guidelines for antibacterial agents to reduce the occurrence and control the spread of antimicrobial-resistant bacteria globally and especially in the developing countries.

Conclusion

In our study, tigecycline was the only antibiotic associated with susceptibility in over 90% of all major pathogen isolates collected from blood specimens. In the comparison that included all world regions, the occurrence of antimicrobial-resistant bacteria was higher in Africa, Asia and Latin America than in Europe and North America. Therefore, reinforcement of the surveillance is important in all regions,but it is very critical in developing countries.

Abbreviations

CARB-NS: 

Cabapanem non-susceptibility

CLSI: 

Clinical and Laboratory Standards Institute

ESBL: 

Extended-spectrum β-lactamase

FDA: 

US Food and Drug Administration

ICU: 

Intensive care unit

IHMA: 

International Health Management Associates

KPC: 

K. pneumonia carbapenemases

MBL: 

Metallo-β-lactamases

MDR: 

Multi-drugs resistance

MIC: 

Minimum inhibitory concentration

MRSA: 

Methicillin-resistance S. aureus

PBP: 

Penicillin-binding protein

PRSP: 

Penicillin-resistance S.pneumoniae

TEST: 

Tigecycline Evaluation and Surveillance Trail

VR: 

Vancomycin resistant

Declarations

Acknowledgements

The authors would like to acknowledge and thank all T.E.S.T investigators and laboratories for their participation in the study, as well as the staff at IHMA for the coordination of T.E.S.T. and at Pfizer for the involvement in study design and the decision to submit this article for publication.

Funding

This study was sponsored by Pfizer, Inc., providing funds for designing the study, performing the tests and managing the data.

Availability of data and materials

The dataset supporting the conclusions of this article is available from the corresponding author on reasonable request.

Authors’ contributions

ZZ and MC participated in data collection and interpretation. ZZ wrote the manuscript. YL and PS reviewed the manuscript. YY was involved in the data interpretation and drafting the manuscript. All authors read and approved the final manuscript.

Ethics approval and consent to participate

Not applicable.

Consent for publication

Not applicable.

Competing interests

ZZ, MC and YL declare no competing interests. YY and PS are employees of Pfizer, Inc.

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Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

Authors’ Affiliations

(1)
Shengjing Hospital of China Medical University, Shenyang, China
(2)
Affiliated Hospital of Hebei University, Baoding, China
(3)
Pfizer Investment Co.,Ltd, Shanghai, China

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Copyright

© The Author(s). 2018

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