Should antibiotic combinations be used to treat ventilator-associated pneumonia?

This review summarizes the rationale for using or not using combinations of antibiotics to treat ventilator-associated pneumonia (VAP). Patients suffering from VAP require empirical antibiotic treatment before the identification of an etiologic agent. Most treatment failures are related to inappropriate initial antibiotic treatment with insufficient coverage of multidrug-resistant (MDR) pathogens. Guidelines require initial (empirical) treatment of VAP with a combination of antibiotics. However, this contributes to overexposure to antibiotics and further emergence of MDR microorganisms. We review the rationale for using combinations of antibiotics to cover MDR gram-negatives. However, clinical data supporting this strategy are limited. In fact, systematic combination therapy may have contributed to the overuse of antibiotics and to the emergence of MDR microorganisms. Nevertheless, combination therapy is our best strategy to treat severe infections due to suspected MDR microorganisms. Optimally, therapeutic strategies should be sufficiently broad to cover relevant pathogens while minimizing the risk for emergence of antimicrobial resistance.     

Antibiotic utilization and outcomes for patients with clinically suspected ventilator-associated pneumonia and negative quantitative BAL culture results

OBJECTIVE: To evaluate antibiotic utilization and clinical outcomes among patients with clinically suspected ventilator-associated pneumonia (VAP) and culture-negative BAL (CNBAL). DESIGN: Prospective observational cohort study. SETTING: A medical ICU from a university-affiliated urban teaching hospital employing a previously described antibiotic discontinuation guideline for the management of VAP. PATIENTS: One hundred one patients with a clinical suspicion of VAP and CNBAL were evaluated between July 2002 and December 2004. INTERVENTIONS: Prospective patient follow-up and data collection. Antibiotic discontinuation was determined by the clinical guideline and not the results of BAL cultures. RESULTS: The average age of the patients was 60.4 +/- 17.9 years and the mean APACHE II score was 23.2 +/- 8.7 (+/- SD). The mean duration of mechanical ventilation prior to clinically suspected VAP was 2.9 +/- 1.9 days. Nineteen patients (18.8%) received antibiotics for other indications prior to BAL. Empiric antibiotic therapy for VAP was begun in 65 patients (64.4%) following BAL. The duration of empiric antibiotic treatment following BAL was 2.1 +/- 0.8 days. None of these patients received antibiotics for > 3 days (median, 2 days; range, 1 to 3 days). Six patients (5.9%) were treated with antibiotics for a secondary episode of VAP or hospital-acquired pneumonia developing at least 72 h after the CNBAL was performed and discontinuation of the empiric antibiotic therapy prescribed for the initially suspected episode of VAP. Overall, 35 patients (34.7%) died during hospitalization. Two deaths occurred in patients with a secondary episode of VAP following CNBAL and discontinuation of empiric antimicrobial therapy. Neither of these two deaths was attributed to VAP. CONCLUSIONS: Although the decision to discontinue antibiotic treatment was based on clinical criteria and not BAL culture results, this study suggests that patients with a clinical suspicion of VAP and CNBAL can have empiric antimicrobial therapy safely discontinued within 72 h or in some cases withheld altogether. Prospective studies are needed to determine the safety of employing CNBAL as the primary criterion for the discontinuation of empirically begun antibiotic treatment for VAP.     

Inhaled Anti-infective Agents: Emphasis on Colistin

The administration of antibiotics by the inhaled route is a widely recognized treatment in patients with cystic fibrosis (CF) and bronchiectasis. Tobramycin solution for inhalation (TOBI) has been available for many years and is licensed in the USA and Europe. While strong data support the use of aerosolized antibiotics for the treatment of respiratory infections in patients with CF or bronchiectasis, only a few clinical studies have examined the role of aerosolized antibiotics in the treatment of pneumonia, including ventilator-associated pneumonia (VAP) in these patients. During the last decade increasing interest has been directed towards alternative treatments to the systemic administration of antimicrobial agents for the treatment of patients with hospital-acquired pneumonia or VAP due to multidrug-resistant (MDR) Gram-negative bacteria. Recent publications demonstrate the clinical benefits from administering inhaled aminoglycosides or polymyxins in patients with hospitalacquired pneumonia or VAP. In addition to antibiotics, antifungals, and antivirals have been administered by inhalation to specific groups of critically ill patients. However, randomized controlled trials dealing with the administration of anti-infective agents via the respiratory tract are necessary in order to validate the efficacy, safety, advantages, and disadvantages of this therapeutic approach for the treatment of nosocomial pneumonia.     

The importance of de-escalating antimicrobial therapy in patients with ventilator-associated pneumonia

The management of ventilator-associated pneumonia (VAP) requires a strategy for antibiotic use that achieves prompt and accurate empirical therapy without overusing antibiotics. Although, efforts at better diagnosis and antibiotic restriction have been attempted, "de-escalation" may be a more useful and effective strategy, and one that can achieve these goals while improving patient outcomes. The centerpiece of this approach is to initiate empirical therapy with a broad-spectrum treatment regimen, based on knowledge of local patterns of microbiology and antimicrobial resistance. Prior to therapy, patients require collection of a lower respiratory tract sample for culture. After 2 to 3 days, the clinical course can be assessed and the culture data reviewed, and in responding patients, efforts can be made to change the initial broad-spectrum therapy. This de-escalation can involve focusing to a more narrow spectrum agent, reducing the number of antibiotics, stopping therapy altogether in patients not likely to have infection, and making efforts to reduce duration of therapy. When this strategy has been used, outcomes such as the frequency of secondary infection, antimicrobial resistance, and mortality have improved. Additional information is needed to apply this approach more widely, especially in patients infected with multidrug-resistant organisms and in those with negative lower respiratory tract cultures.     

Appropriateness and delay to initiate therapy in ventilator-associated pneumonia.

Inappropriate therapy (IT) and delayed initiation of appropriate therapy (DIAT) result in inadequate therapy in patients with ventilator-associated pneumonia (VAP). The aim of the current study was to assess the impact of DIAT in VAP. A total of 76 mechanically ventilated patients with bacteriologically confirmed VAP were prospectively evaluated in the intensive care unit of six hospitals in Buenos Aires, Argentina. Appropriate therapy was defined as coverage of all the identified pathogens by the antimicrobial therapy administered at the time of VAP clinical diagnosis. The clinical pulmonary infection score was measured during the 3 days before, at the onset and during the days which followed the onset of VAP. A total of 24 patients received adequate therapy; mortality was 29.2%. The remaining 52 patients received either IT (n = 16) or DIAT (n = 36); the mortality was 63.5% combined, and 75.0 and 58.3% for IT and DIAT, respectively (statistically significant compared with adequate therapy). Inappropriate therapy and delayed initiation of appropriate therapy increased the mortality of ventilator-associated pneumonia. Patients with inappropriate therapy and/or delayed initiation of appropriate therapy had a more gradual increase in clinical pulmonary infection score than those receiving adequate therapy, and this increase was found to occur prior to the time of the clinical diagnosis. In conclusion, these findings might provide the rationale for a trial of earlier initiation of therapy, based on clinical grounds in an effort to improve the outcome of patients with ventilator-associated pneumonia.     

Diagnosis and treatment of ventilator-associated pneumonia: fiberoptic bronchoscopy with bronchoalveolar lavage is essential

The management of patients suspected of having ventilator-associated pneumonia (VAP) requires a strategy for diagnosis and treatment that is designated to: (1) identify patients with true lung bacterial infection; (2) determine the pathogen(s) responsible for pneumonia; (3) permit early selection of appropriate antimicrobial therapy; and (4) avoid indiscriminate administration of antibiotics. The use of bronchoscopic techniques to obtain bronchoalveolar lavage (BAL) specimens from the affected area in the lung allows definition of a strategy superior to that based exclusively on clinical evaluation. When BAL is performed before introduction of new antibiotics, it enables physicians to identify patients who need immediate treatment and help to select initial antibiotic therapy (with the results of direct examination of BAL liquid) and to withhold, deescalate, and/or optimize treatment (when the results of quantitative cultures are available), in a manner that is safe and well tolerated by patients. This strategy, based on clinical and bacteriological evaluation, prevents resorting to broad-spectrum drug coverage in all patients who develop signs and symptoms suggestive of pneumonia, thus minimizing the emergence of resistant flora, and redirects the search for another infection site.     

When can empiric therapy for intensive care unit-acquired pneumonia be withheld or withdrawn?

Diagnosing ventilator-associated pneumonia (VAP) is difficult, creating important clinical dilemmas for intensive care physicians. Adequate empiric antimicrobial therapy is crucial because VAP is associated with increased morbidity and mortality, especially when initial treatment is inappropriate. Because VAP is the most frequent occurring nosocomial infection, it is, to a large extent, responsible for the high antibiotic consumption in ICUs, which is an important cause for selection and induction of antibiotic resistance. In addition, antibiotics may have adverse effects and their costs should be considered. Therefore, a balance should be found between the obvious necessary therapeutic benefits and the negative effects (selection of resistant pathogens, costs, and adverse effects) of antibiotics in the treatment of VAP. Although guidelines for initial antimicrobial therapy have been established, no such recommendations exist for withholding or withdrawing antimicrobial treatment, and little is known about the optimal duration of therapy.     

慢性阻塞性肺疾病患者呼吸机相关肺炎的病原菌特点与临床分析

目的 探讨慢性阻塞性肺疾病(chronic obstructive pulmonary disease,COPD)患者呼吸机相关肺炎(ventilator-associated pneumonia,VAP)的病原菌分布与临床特点.方法 回顾分析对我院呼吸科及重症监护病房COPD并呼吸衰竭患者行插管机械通气发生VAP的52例患者的下呼吸道分泌物、肺泡灌洗液等标本进行细菌培养和药敏实验,并分析临床特点.结果 COPD并VAP的主要病原菌依次是铜绿假单胞菌(25.6%)、肺炎克雷伯菌(15.8%)、耐甲氧西林金黄色葡萄球菌(15.8%)、鲍曼不动杆菌(13.4%)和大肠埃希菌(8.5%),以革兰阴性杆菌为主.结论 COPD并VAP病原菌对常见抗生素耐药性较高,机械通气术前抗生素应用者,VAP的病原菌高度耐药,病死率较高;抗生素治疗应用降阶梯方法病死率较低;迟发性(4 d后)VAP与早发性(4 d内)VAP病死率差异无统计学意义.     

Value of the serum procalcitonin level to guide antimicrobial therapy for patients with ventilator-associated pneumonia

Procalcitonin's contribution to the diagnosis of nosocomial infection, particularly ventilator-associated pneumonia (VAP), is poor: its levels in patients with microbiologically documented VAP the day infection is diagnosed range from normal to extremely high. Moreover, the results of four studies showed that, despite relatively good specificity, this marker had low sensitivity for the diagnosis of VAP. However, because procalcitonin is well associated with outcome, its kinetics during antimicrobial therapy can be used to customize that treatment duration. Two recent studies showed that a procalcitonin-based strategy (recommending that treating physicians stop antibiotics when the procalcitonin concentration was <0.5 ng/mL, or had decreased by ≥80%) led to less antibiotic consumption by VAP patients, compared with a conventional strategy, with no adverse outcome. Accordingly, for VAP patients, procalcitonin may be used to stop antibiotics as early as day 3 after their initiation, if its concentration is <0.5 ng/mL or has decreased by ≥80%, compared with the first peak concentration.     

Ventilator-associated pneumonia

Ventilator-associated pneumonia (VAP) continues to complicate the course of 8 to 28% of patients receiving mechanical ventilation (MV). In contrast to infections of more frequently involved organs (e.g., urinary tract and skin), for which mortality is low, ranging from 1 to 4%, the mortality rate for VAP ranges from 24 to 50% and can reach 76% in some specific settings or when lung infection is caused by high-risk pathogens. The predominant organisms responsible for infection are Staphylococcus aureus, Pseudomonas aeruginosa, and Enterobacteriaceae, but etiologic agents widely differ according to the population of patients in an intensive care unit, duration of hospital stay, and prior antimicrobial therapy. Because appropriate antimicrobial treatment of patients with VAP significantly improves outcome, more rapid identification of infected patients and accurate selection of antimicrobial agents represent important clinical goals. Our personal bias is that using bronchoscopic techniques to obtain protected brush and bronchoalveolar lavage specimens from the affected area in the lung permits physicians to devise a therapeutic strategy that is superior to one based only on clinical evaluation. When fiberoptic bronchoscopy is not available to physicians treating patients clinically suspected of having VAP, we recommend using either a simplified nonbronchoscopic diagnostic procedure or following a strategy in which decisions regarding antibiotic therapy are based on a clinical score constructed from seven variables. Selection of the initial antimicrobial therapy should be based on predominant flora responsible for VAP at each institution, clinical setting, information provided by direct examination of pulmonary secretions, and intrinsic antibacterial activities of antimicrobial agents and their pharmacokinetic characteristics. Further trials will be needed to clarify the optimal duration of treatment and the circumstances in which monotherapy can be safely used.     

Role of serial routine microbiologic culture results in the initial management of ventilator-associated pneumonia.

Results of routine microbiologic cultures of specimens obtained before the onset of ventilator-associated pneumonia (VAP) in intensive care unit (ICU) patients might help to identify the causative microorganisms and thus to select effective initial antimicrobial therapy. To test this hypothesis, we prospectively studied 125 consecutive VAP episodes for which the causative microorganisms were determined using bronchoscopic techniques. Upon entry into the study, each patient's hospital chart was reviewed and culture results of all previously obtained microbiologic specimens were recorded (mean number +/- SD per patient, 45 +/- 38). A total of 220 microorganisms were cultured at significant concentrations (> or = 10(3)/10(4) colony-forming units [cfu]/ml) from bronchoscopic specimens and considered responsible for pneumonia. Of these 220 organisms, only 73 (33%) were recovered before VAP onset, sometimes from multiple sites in the same patient but mainly from prior respiratory secretion cultures (n = 53). Also previously isolated were 342 organisms that were not responsible for VAP, making prospective identifications of the true pathogens difficult. Among the 102 episodes for which prior respiratory secretion culture results had been obtained (mean time before VAP onset, 8 +/- 9 d), all the organisms ultimately responsible for pneumonia were previously recovered from only 36 (35%) of these specimens. Based on these data, the contribution of routine microbiologic specimens in guiding initial antimicrobial therapy decisions for patients with suspected VAP appears limited.     

Diagnosis and treatment of ventilator-associated pneumonia

Ventilator-associated pneumonia (VAP) is the most common nosocomial infection in the ICU. Patients who acquire VAP have higher mortality rates and longer ICU and hospital stays. Because there are other potential causes of fever, leukocytosis, and pulmonary infiltrates, clinical diagnostic criteria are overly sensitive in the diagnosis of VAP. Employing quantitative cultures of bronchopulmonary secretions in the diagnostic algorithm leads to less antibiotic use and probably to lower mortality. With respect to microbiologic diagnosis, it is not clear that the use of a particular sampling method (bronchoscopic or nonbronchoscopic), when quantitatively cultured, is associated with better outcomes. Delayed administration of adequate antibiotic therapy is linked to an increased mortality rate. Hence, the focus of initial antibiotic therapy should be to rapidly provide antibiotic coverage for all likely pathogens and to then narrow or focus the antibiotic spectrum based on the results of quantitative cultures. Eight days of antibiotic therapy appears equivalent to 15 days of therapy except when treating nonlactose-fermenting Gram-negative organisms. In this latter situation, longer treatment durations appear to reduce the risk of recrudescence after discontinuation of antibiotic therapy. A guideline-based approach using the local hospital or ICU antibiogram can increase the likelihood that adequate initial antibiotic therapy is used and reduce the overall use of antibiotics and the associated selection pressure for multidrug-resistant organisms.     

不同类型老年吸入性肺炎的病原学、抗生素应用及临床转归

目的 比较老年社区获得性吸入性肺炎(CAP)、医疗相关性吸入性肺炎(HCAP)及医院获得性吸入性肺炎(HAP,包括呼吸机相关性吸入性肺炎)三者病原学、抗生素应用及治疗转归的关系.方法 收集2005年1月一2010年12月北京二炮总医院呼吸科住院的216例老年吸人性肺炎患者病例,分析其病原学结果、抗生素应用的及治疗转归.结果 三种吸入性肺炎的病原学有显著差异,与CAP和HCAP相比,HAP患者G-杆菌的感染比例明显增多(P<0.001);抗生素应用方案有明显差异,CAP组病人未调整抗生素应用比率明显高于HCAP组与HAP组(P<0.001);抗生素应用策略不同,所致死亡率有明显差异,以升阶梯方案为最高,以降阶梯治疗为最低(P=0.03).结论 三种吸入性肺炎在感染病原菌种类、抗生素应用策略及治疗转归上有明显差异,应根据不同类型的老年吸入性肺炎特点合理经验性使用抗菌药物.     

COPD患者呼吸机肺炎的致病菌特点及治疗模式分析

目的探讨慢性阻塞性肺疾病(COPD)患者发生呼吸机相关性肺炎(VAP)的病原菌特点及不同治疗方法的预后,为临床提供治疗依据。方法对67例符合VAP标准的COPD机械通气患者的痰培养病原学、药敏结果、治疗方法及预后进行回顾性分析。结果VAP的病原菌以G-杆菌为多数,铜绿假单胞菌、不动杆菌属为VAP的主要致病菌(35．1％);金黄色葡萄球菌为VAP的主要致病G 球菌。病原菌对常用抗菌药耐药率较高,降阶梯治疗组的病死率(13．3％)明显低于升阶梯治疗组(61．5％)和非阶梯治疗组(33．3％)。结论铜绿假单胞菌、不动杆菌属、金黄色葡萄球菌为COPD患者VAP的主要病原菌,病原菌的耐药率较高,使用降阶梯治疗可降低病死率。     

Variations in etiology of ventilator-associated pneumonia across four treatment sites: implications for antimicrobial prescribing practices.

This retrospective multicenter study compared microorganisms documented by quantitative cultures from bronchoscopic samples in episodes of ventilator-associated pneumonia (VAP) from three different institutions in Barcelona (B), Montevideo (M), and Seville (S). The observations were compared with the findings reported by Trouillet and coworkers (AJRCCM 1998;157:531-539) in Paris (P). The objective was to evaluate whether a classification of etiologies of VAP in four groups, based on the number of ventilation days and previous antimicrobial use, might contribute to establishing generalized guidelines for empirical therapy. Significant variations in etiologies (p < 0.05) were found in all of the microorganisms isolated from VAP episodes across three treatment sites when compared with the reference site (P). In Group 1 (< 7 d and absence of antibiotics), Pseudomonas aeruginosa remained extremely infrequent (3 of 89, 3.3%) in the joint category, whereas the incidence of Acinetobacter baumannii was significantly higher, owing to M findings. On the other hand, one site (B) had a significantly lower incidence of multiresistant pathogens (Methicillin-resistant Staphylococcus aureus [MRSA] and nonfermenters other than P. aeruginosa), even in Group 2 (< 7 d and antibiotics), Group 3 (>/= 7 d and absence of antibiotics), and Group 4 (antibiotics and >/= 7 days). Similar findings were documented when episodes were grouped according to Groups 1 and 3 of the ATS guidelines. We conclude that causes of VAP varied markedly across four treatment sites, resulting in the need for large-scale variations in antimicrobial prescribing practices. Instead of following general recommendations, antimicrobial prescribing practices for VAP should be based on up-to-date information of the pattern of multiresistant isolates from each institution.     

Ventilator-associated pneumonia due to colistin susceptible-only microorganisms.

Acinetobacter spp. and Pseudomonas aeruginosa are common pathogens of ventilator-associated pneumonia (VAP). The presentation and outcome of VAP due to Acinetobacter spp. and P. aeruginosa susceptible to carbapenems (Carb-S; imipenem and/or meropenem) and to colistin only (Col-S) were compared in the present retrospective study in three intensive care units. A total of 61 episodes of VAP caused by Acinetobacter spp. or P. aeruginosa were studied, of which 30 isolates were Carb-S and 31 were Col-S. Demographics, worsening of renal function and mortality were not different. The univariate analysis showed that a later onset and a previous episode of VAP, prior antimicrobial therapy for >10 days and previous therapy with carbapenems during the present admission were more frequent in patients with Col-S strains. On multivariate analysis, prior antimicrobial therapy for >10 days and a previous episode of VAP remained significantly associated with Col-S VAP. Approximately 41% of the infections caused by Col-S isolates, but none of those due to Carb-S isolates, had received prior carbapenem therapy. Colistin-susceptible ventilator-associated pneumonia episodes can be effectively treated using colistin without significant renal dysfunction. This susceptibility pattern could be suspected in patients with a previous ventilator-associated pneumonia episode or prior antibiotic therapy for >10 days preceding the present ventilator-associated pneumonia episode.     

Neumonía nosocomial

The hospital acquired pneumonia (HAP) is one of the most common infections acquired among hospitalised patients. Within the HAP, the ventilator-associated pneumonia (VAP) is the most common nosocomial infection complication among patients with acute respiratory failure. The VAP and HAP are associated with increased mortality and increased hospital costs. The rise in HAP due to antibiotic-resistant bacteria also causes an increase in the incidence of inappropriate empirical antibiotic therapy, with an associated increased risk of hospital mortality. It is very important to know the most common organisms responsible for these infections in each hospital and each Intensive Care Unit, as well as their antimicrobial susceptibility patterns, in order to reduce the incidence of inappropriate antibiotic therapy and improve the prognosis of patients. Additionally, clinical strategies aimed at the prevention of HAP and VAP should be employed in hospital settings caring for patients at risk for these infections.     

Aerosolized colistin as adjunctive treatment of ventilator-associated pneumonia due to multidrug-resistant Gram-negative bacteria: a prospective study

BACKGROUND: Ventilator-associated pneumonia (VAP) remains the leading cause of death in patients with intensive care unit (ICU) acquired infections associated with an attributable mortality around 30%. Increasing antimicrobial resistance in patients with VAP challenges intensivists to search for alternative therapeutic options. There is scarcity of data in the literature concerning the administration of aerosolized colistin in critically ill patients with VAP due to multidrug-resistant (MDR) Gram-negative pathogens. METHODS: To assess the safety and effectiveness of aerosolized colistin as an adjunctive to the intravenous antimicrobial therapy for the treatment of VAP due to MDR Gram-negative pathogens, we prospectively examined all patients, who received inhaled colistin. RESULTS: Sixty critically ill patients with a mean APACHE II score 16.7, received aerosolized colistin for the treatment of VAP due to MDR pathogens [Acinetobacter baumannii (37/60 cases), Pseudomonas aeruginosa (12/60 cases) and Klebsiella pneumoniae strains (11/60 cases)]. Half of the isolated pathogens were susceptible only to colistin. Mean (+/-SD) daily dosage of aerosolized colistin was 2.2 (+/-0.7) million international units (IU). All patients received 2946 inhalations of colistin and the mean duration of administration was 16.4 days. Fifty-seven patients received concomitant intravenous treatment with colistin or other antimicrobial agents. Bacteriological and clinical response of VAP was observed in 50/60 (83.3%) patients. No adverse effects related to inhaled colistin were recorded. All cause hospital mortality was 25% while mortality attributable to VAP was 16.7%. CONCLUSIONS: Aerosolized colistin may be considered as adjunctive to intravenous treatment in patients with VAP due to MDR Gram-negative bacteria susceptible to colistin in critically ill patients. Although colistin is safe and effective, the best route of administration remains unclear. In addition, controlled comparative studies are needed to establish its effectiveness and safety.     

Clinical analysis of patients requiring long-term mechanical ventilation of over three months: ventilator-associated pneumonia as a primary complication

OBJECTIVE: To evaluate the clinical features, etiology, and prognosis of patients who required long-term mechanical ventilation (LMV) of over three months for respiratory failure following underlying disease, and observation of their clinical course until death. PATIENTS: Thirty-seven patients (27 males, 10 females) treated in the internal and medical intensive care unit at Kawasaki Medical School Kawasaki Hospital over the 16-year period from April 1985 to March 2001 were retrospectively studied. RESULTS: Many of these patients were elderly males with respiratory disease such as pulmonary emphysema or old pulmonary tuberculosis, which had developed into acute respiratory failure resulting in respiratory tract infection and initiation of mechanical ventilation. The survival rates of one year, three years and five years after the start of mechanical ventilation were 60%, 30%, and 16%, retrospectively, and the prognoses were poor. Respiratory tract infection was the most common and serious complication. Specifically, ventilator-associated pneumonia (VAP) was a complication in 21 patients and also the main-cause of death. VAP was observed 2.3 years after the initiation of mechanical ventilation with significant differences in the following risk factors being observed between VAP (+) and VAP (-) groups: chronic obstructive pulmonary disease, duration of mechanical ventilation, prior antibiotics, aspiration of gastric contents and use of histamine-type II receptor antagonist. The causative pathogens of VAP were Pseudomonas aeruginosa and Staphylococcus aureus, which were frequently isolated from tracheal aspirates. All patients with VAP caused by MRSA died shortly after contracting the infection. CONCLUSIONS: This study has demonstrated that appropriate treatment for respiratory tract infections such as VAP and the prevention of nasocomial infection due to MRSA is of paramount importance for patients requiring long-term mechanical ventilation of over three months.     

Epidemiology and microbiology of hospital-acquired pneumonia

Hospital-acquired pneumonia (HAP) is the second most common nosocomial infection in the critically ill patient and is associated with the greatest mortality and increased morbidity and cost of care. The major risk factor for the development of HAP in intensive care is the occurrence of intubation and mechanical ventilation, giving rise to the term ventilator-associated pneumonia (VAP). Incidence of VAP varies in different populations of critically ill patients and generally ranges from 9 to 20%, with an overall rate of 10 to 15 cases per 1,000 ventilator days. The cumulative risk of developing VAP is ~1% per day of mechanical ventilation (MV). The crude mortality rate of VAP is 60% and the estimates of attributable risk range from 27 to 43%. Mortality from VAP is influenced by host factors, the virulence of the pathogens, and the adequacy of initial antimicrobial therapy. The etiologic agents for VAP differ according to the population studied, duration of hospital stay, time after intubation, and prior antimicrobial therapy. Risk factors include nonmodifiable factors like age, chronic obstructive pulmonary disease, severe head trauma, and multiple trauma, and modifiable factors like large volume gastric aspiration, duration of MV, elevated gastric pH, histamine type 2 blocker therapy, ventilator circuit change frequency, self-extubation, and reintubation. The impact that diagnosis using invasive diagnostic techniques may have on the epidemiological characteristics of VAP are unknown, but may potentially reduce problems resulting from misclassification of this entity.