Epidemiology
HAIs affect millions of patients worldwide every year. The total annual number of patients with an HAI in European acute care hospitals in 2011–2012 was estimated at 3.2 million, causing 37,000 deaths as a direct consequence, more than 2.5 million Disability Adjusted Life Years (DALYs) and 16 million extra days of hospitalization, with an approximate cost of around €7 billion [14].
The 2016–2017 Point Prevalence Survey (PPS) by the European Centre for Disease Prevention and Control (ECDC) has estimated that 8.9 million distinct HAI episodes occur annually in acute care hospitals and long-term care facilities in Europe [15].
In Italy, a number between 450,000 and 700,000 cases of HAI is estimated to occur every year in hospitalized patients, of which 30% considered preventable [16]. The 2016/2017 Italian PPS2 report on HAIs and antibiotic use in acute care hospitals reported that the prevalence of patients with at least one HAI was 8.03%, whereas when considering the average prevalence of HAIs across hospitals, this estimate becomes 6.5%, indicating that some larger, highly specialized hospitals showed a higher prevalence [17,18,19,20].
Hospital-acquired infection sites
The most frequent types of infection include.
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1.
Catheter-Associated Urinary Tract Infections (CAUTI).
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2.
Surgical Site Infections (SSI).
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3.
Hospital-Acquired Pneumonia (HAP) and Ventilator Associated Pneumonia (VAP).
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4.
Central Line-Associated BloodstreamIinfections (CLABSI).
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5.
Care-related Skin and Soft Tissue Infections (SSTI).
A brief detail of these is given below:
Catheter associated urinary tract infections (CAUTI)
Among hospital-acquired urinary tract infections, 70–80% are attributable to the use of an indwelling urinary catheter. Catheter-Associated Urinary Tract Infections (CAUTI) are the most frequently observed conditions, with an incidence 40% of all HAIs [21].
The duration of catheterization is the most important risk factor for developing CAUTI. Therefore, reducing unnecessary catheter placement and minimizing the duration of catheter stay in situ are the main strategies for prevention of CAUTI. Additional risk factors include female sex, older age, diabetes mellitus, renal failure, and malnutrition [22].
Although the proportion of bacteremic individuals who develop symptomatic infection is low, given the high frequency of indwelling urinary catheter use, CAUTI is one of the most common causes of secondary bloodstream infection. CAUTI is the source of approximately 20% of healthcare-acquired bacteraemia episodes in acute care facilities and more than 50% in long-term care facilities [23].
The estimated cost of HAIs in a Polish Intensive Care Unit (ICU) ranges from EUR 10,035 to 22,411. While in the USA, an estimate of 449,334 healthcare-associated CAUTIs per year, is associated with an additional cost of US$749–10,077-9 per admission in 2007 (or an estimated US$3744 when complicated by blood septicaemia) [24].
Comprehensive recommendations have been published to assist acute care hospitals in implementing and prioritizing their CAUTI prevention efforts [25,26,27].
Surgical site infections (SSI)
Surgical Site Infections (SSIs) are a major complication during hospitalization, occurring in 2–5% of patients subjected to surgery. These are the second most common type of nosocomial infections caused primarily by Staphylococcus aureus resulting in prolonged hospitalization and increased risk of mortality. In most SSIs, the responsible pathogens originate from the patient’s endogenous flora [28].
From the 2017 European Annual Epidemiology Report, the percentage of SSIs ranges from 0.5% to 10.1%, depending on the type of surgical procedure [29].
SSIs are defined as infections occurring up to 30 days after surgery (if no implant is left in place) and affecting either the incision or deep tissue at the operation site. These infections may be superficial involving only skin and subcutaneous tissue of the incision, or deep incisional infections down to the deep soft tissues (fascia and muscle), or infections involving organs and body spaces.
Major patient-related risk factors include advanced age, diabetes mellitus or other chronic diseases, nutritional status, obesity, immunodepression, colonisation with microorganisms (particularly S. aureus). Emergency surgery, type of surgery, length and quality of preoperative stay, skin disinfection, inadequate sterilization of surgical instruments and antimicrobial prophylaxis are procedure-related risk factors [30].
Thus, continuous vigilance is required to minimize the incidence of such infections. This requires a systematic approach, with attention to multiple risk factors to reduce the risk of bacterial contamination and improve patient’s defences [31, 32].
The 2017 Centres for Disease Control and Prevention (CDC) guideline provides new and updated evidence-based recommendations for the prevention of SSI and should be incorporated into comprehensive surgical quality improvement programs to improve patient safety [33, 34].
SSIs are responsible for generating significant costs. In 2017, a French cohort showed an average cost of each SSI treatment of approximately €1814; the same year, the Centres for Disease Control and Prevention guidelines estimated the mean cost caused by SSI treatment at $10,443–$25,546 per SSI. This cost depends on many factors including the patient themselves and the type of surgery [35].
Hospital-acquired pneumonia (HAP) and Ventilator associated pneumonia (VAP)
Hospital-Acquired Pneumonia (HAP) is the second most common infectious complication contracted during hospitalization. The incidence ranges from 5 to 10 cases per 1000 admissions in patients without risk factors, but this estimate may increase can increase 6 to 20-fold in patients admitted to ICU and receiving mechanical ventilation [36].
Ventilator Associated Pneumonia (VAP) is found in 9–27% of mechanically ventilated patients and usually occurs within 48 h after tracheal incubation [37]. The risk of contracting VAP increases proportionally with prolonging duration of both mechanical ventilation and ICU stay. Mortality attributable to VAP ranges from 15 to 50%, with higher mortality rates in surgical patients in the ICU and in patients with average severity scores on admission [38, 39].
The results of a study on the effect of VAP on the prognosis of ICU patients within 90 days and 180 days showed that the 90-day mortality of VAP patients was 33.33% and the 180-day mortality was 37.62%. The 90-day and 180-day mortality rates were higher in the VAP group than in the non-VAP group. The risk of 90-day and 180-day mortalities in VAP patients were 1.465 times (OR = 1.465, 95% CI: 1.188–1.807, P < 0.001) and 1.635 times (OR = 1.635, 95% CI: 1.333–2.005, P < 0.001) higher than those in non-VAP patients, respectively [40].
New international evidence-based guidelines for the prevention of HAP/VAP have recently been published in Europe and America and provide guidance on the most effective treatments and management strategies for adult patients with HAP and VAP [36, 41].
Central line-associated bloodstream infections (CLABSI)
The main source of infections in the circulatory stream are due to the implantation of vascular catheters (Central Line-Associated Bloodstream Infection—CLABSI). Catheters are placed in the central line to deliver fluids and medications, but prolonged use can cause severe bloodstream infections resulting in impaired health, and increased hospitalization and cost of care [42]. CLABSIs account for approximately 20% of nosocomial circulatory infections, with a mortality rate of 12–25% [43].
Host factors that increase the risk of CLABSI are chronic disease, immunocompromised states (organ transplantation, diabetes mellitus), malnutrition, total parenteral nutrition, loss of skin integrity (burns), and prolonged hospitalization prior to catheter insertion. Femoral central venous catheters are associated with the highest risk of CLABSI, followed by internal jugular and subclavian catheters. In addition, catheter type, insertion conditions, catheter care, and operator skill also influence the risk of CLABSI.
Of all HAIs, CLABSIs are associated with a high-cost burden of approximately $46,000 per case [44]. Most cases are preventable with appropriate aseptic techniques, surveillance, and management strategies.
The updated guideline released by the CDC in 2011 along with more recent studies highlight new strategies to reduce the incidence of CLABSI [45–47].
Care-related skin and soft tissue infections (SSTI)
Skin and Soft Tissue Infections (SSTIs) are common in outpatient clinic and emergency department visits and include a wide variety of infections of the various layers of skin, fascia, and muscle. SSTIs usually result from traumatic, surgical, or healthcare-related skin breakdown with secondary infection by microorganisms [48].
The severity of SSTIs ranges from mild and superficial to deeper or potentially fatal necrotizing infections requiring hospitalization or intensive care. Among hospitalized or critically ill patients, several epidemiological studies have shown that about 4.3–10.5% of septic episodes are caused by SSTIs [49, 50].
Using data from the 2000–2004 US Healthcare Cost and Utilization Project National Inpatient Sample, Edelsberg et al. suggested that the majority of hospitalized SSTIs were either “superficial” (58.6%) or “deeper and/or healthcare-associated” (40.1%) infections; the percentage of “often fatal” SSTIs was relatively low (1.3%) [51].
In a large database study of skin-related conditions in the ICU, only 0.4% of all ICU admissions had SSTIs, and about 60% of those were necrotizing fasciitis, a potentially fatal infection [52].
Two other studies, including only “superficial” and “deep and/or healthcare-associated” infections, showed that approximately 2.0–5.8% of patients hospitalized with SSTIs are admitted to the ICU [53, 54].
A large number of expert opinions, guidelines, and recommendations for the management of SSTIs have been published over the past decade, taking into account the initial severity of the patient (whether or not the patient requires ICU admission), the extent of the infection (superficial or deep infection), and risk factors for resistant microorganisms essentially related to healthcare-associated circumstances [55,56,57,58].
Factors influencing the development of HAIs
Numerous factors can increase the risk of contracting a HAI, which, in general, can be divided into three groups: host factors, microorganism-related factors, and environmental factors [59].
Patient-related risk factors include advanced age, multiple underlying comorbidities, chronic conditions such as chronic kidney disease, cardio-respiratory disease, and diabetes mellitus, and all conditions of immunosuppression related to drugs (steroid therapy, chemotherapy, radiation therapy, immunomodulatory therapies) and diseases (HIV infection, onco-hematologic diseases, solid organ or bone marrow transplantation, burns, and malnutrition) [60].
Potentially all microorganisms can cause HAI, but generally bacteria and viruses are the main infectious agents. One of the main risk factors related to microorganisms is certainly antibiotic resistance [61].
Finally, the main environmental risk factors are exposure to invasive procedures that increase the risk of infectious complications due to direct access of microorganisms to normally sterile areas of the body and contamination of the devices themselves at the time of use. Exposure to invasive procedures and/or complex surgeries, length of hospital stay, frequent visits to healthcare facilities, mechanical ventilator support, and a stay in an ICU also increase the likelihood of infectious complications [62].
In conclusion, the risk of HAIs depends on the infection control practices in the facility, the condition and immune status of the patient, and the prevalence of various pathogens in the community.
Mode of transmission
The main route of transmission is by contact. Direct or indirect contact and transmission by droplets fall into this category [63].
Direct contact between a susceptible host and an infected or colonized person can occur during daily care activities, primarily through hands, or through the contact between patients.
Indirect contact occurs through a contaminated intermediate object (instrumentation/surfaces) or through a contaminated common vehicle (food, blood, infusion fluids, disinfectants).
Droplet transmission occurs when droplets containing the pathogens emitted in the act of coughing or sneezing by an infected person are inhaled by a susceptible person who is within a short distance (via droplets) or at a distance (aerosol). Another mode of transmission is by the airborne route, through microorganisms that survive in the air and are transmitted over distance.
