_______________________________________________________________ Healthcare-Associated Infections
shown that S. aureus is common among patients who are in a coma or have diabetes or renal failure; P. aeruginosa is com- mon among patients who have had a prolonged stay in the ICU, have received prior antibiotics or corticosteroids, or who have structural lung disease; and Legionella is usually found in patients who have compromised immune systems [198]. Ventilator-Associated Pneumonia In 2018–2021, the most common pathogens reported with ven- tilator-associated pneumonia in adults were S. aureus (29.6%) and P. aeruginosa (13.4%), followed by K. pneumonia/oxytoca (12.1%), Enterobacter spp. (6.1%), and E. coli (5.2%) [146]. Almost half of all cases of ventilator-associated pneumonia are caused by infection with more than one pathogen [193]. As with other forms of HAI, the percentage of S. aureus resistant to methicillin has decreased in recent years [4; 167]. The percentage of vancomycin-resistant E. faecium has remained stable, but the percentage of vancomycin-resistant E. faecalis decreased from 7% in 2015–2017 to 5.5% in 2018–2021 [146]. In 2018–2021, the rates of resistance among Klebsiella spp. for extended-spectrum cephalosporins, carbapenems, multidrug were 25.8%, 3.3%, and 11.9%, respectively, and the rate of multidrug-resistant E. coli increased to nearly 12% [146]. Prevention The CDC has published guidelines for the prevention of hospital-acquired and ventilator-associated pneumonia, with a focus on strategies to decrease or eliminate modifiable risk factors [27]. These strategies are related to preoperative and postoperative care and measures to reduce the risk of trans- mission of etiologic pathogens. In addition, steps to prevent the spread of influenza virus are essential, especially during influenza season. Hospital-Acquired Pneumonia For many years, preventing postoperative pneumonia has been a part of initiatives to decrease complications among patients who have surgery. The Respiratory Risk Index was developed to classify patients as being at low, medium, or high risk for postoperative respiratory failure [194]. The factors in the index include the complexity of the surgery, the ASA status, and comorbidities. Smoking triples the risk for pulmonary complications after surgery, and smoking cessation for at least 8 weeks before surgery, when possible, is recommended for current smokers [194]. The risk for complications in patients with respiratory disease or congestive heart failure can be ameliorated by opti- mum treatment before surgery (e.g., treatment with steroids for patients with COPD or asthma) [194]. Effective pain management after surgery can also help decrease the risk of pulmonary complications. For postoperative patients who are not mechanically intubated, the ability to cough and clear secretions is important for preventing pulmonary com- plications [194]. The use of incentive spirometry and deep
as the antibiotic sensitivity pattern of resident pathogens will vary from region to region in relation to the type of facility and burden of antimicrobial usage. The selection of initial antibiotic therapy in these cases is based on the patient’s risk factors for infection with a multidrug-resistant organism, such as MRSA, P. aeruginosa , K. pneumoniae , or Acinetobacter . The infectious disease and pulmonary specialty societies (IDSA and American Thoracic Society [ATS]) list the following risk factors for multidrug-resistant pathogens in patients presenting with hospital-acquired or ventilator-associated pneumonia [20]: • Prior intravenous antibiotic use within 90 days • Septic shock at time of ventilator-associated pneumonia • Acute respiratory distress syndrome prior to onset of ventilator-associated pneumonia • High frequency of antibiotic resistance in the community of residence or the hospital unit of residence • Five or more days of hospitalization prior to onset of pneumonia • Home infusion therapy • Chronic dialysis within 30 days • Family member with multidrug-resistant infection • Immunosuppression Approximately 50% of all cases of healthcare-associated pneu- monia develop following surgical procedures, of which cardiac, abdominal, and orthopedic surgery confer the greatest risk. Viral and fungal pathogens are rare causes of hospital-acquired and ventilator-associated pneumonia in immunocompetent adults. Outbreaks of viral pneumonia may occur during influ- enza season, and influenza, parainfluenza, adenovirus, and respiratory syncytial virus (RSV) are involved in about 70% of those cases [20]. During the coronavirus disease (COVID-19) pandemic, SARS-CoV-2 has superseded the usual viral respira- tory pathogens. Candida spp. and Aspergillus fumigatus may cause pneumonia in patients who have had organ transplantation or who have a compromised immune system and neutropenia. Hospital-Acquired Pneumonia Among adults with no previous antibiotic exposure, the most common bacterial causes of hospital-acquired pneumonia are S. aureus , S. pneumoniae , H. influenzae , E. coli , and K. pneu- moniae [20; 193; 194; 198]. Gram-negative bacilli resistant to first-generation cephalosporins also frequently develop in late-onset hospital-acquired pneumonia. When patients who have previously received antibiotics develop late-onset hospital-acquired pneumonia, the likelihood of causation by a multidrug-resistant pathogen, such as P. aeruginosa , A. baumannii , or MRSA, approaches 40% [194]. In a study of more than 3,600 patients admitted to an ICU, Pseudomonas spp. was the cause of pneumonia in 25% of patients; MRSA in 18%; and Acinetobacter spp. in 6% [198]. Other studies have
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