Attributable Mortality of Nosocomial Acinetobacter Bacteremia

Acinetobacter infection in the ICU

Acinetobacter is a formidable challenge to managing critically ill patients. This pathogen's ability to rapidly develop antimicrobial resistance to all currently available antimicrobial agents is concerning because increasing data support attributable mortality to these bacteria when associated with hospitalized patients with comorbidities and severe illness. The role of dual therapy is currently unclear and might be associated with increased toxicities without proven synergy or ability to prevent the development of resistance. Infection control and antibiotic control measures might have the greatest impact on these bacteria. Continued efforts are needed to develop new antimicrobial agents against this pathogen and assess the ideal currently available agents.

Antibiotic use in 26 departments of internal medicine in 6 general hospitals in Israel: variability and contributing factors

OBJECTIVES

Increased antibiotic consumption is associated with increased bacterial resistance worldwide. We aimed to analyse antibiotic consumption and potential contributory factors in internal medicine departments in Israel.

METHODS

Data (2003-04) from 26 departments in 6 hospitals were retrieved. Defined daily doses (DDD)/100 bed-days were calculated for total antibiotic use and by antibiotic class. Patterns identified were correlated with 15 patients' and departmental variables by univariate and multivariate analyses.

RESULTS

Total antibiotic consumption differed by a factor of 2.3 (115 DDD/100 bed-days to 49.1 DDD/100 bed-days) between the highest and lowest consuming departments. Antibiotic classes differed by a factor of 22.8 for macrolides, a factor of 20 for piperacillin/tazobactam, a factor of 17 for carbapenems, a factor of 13.3 for quinolones, a factor of 9 for vancomycin, a factor of 6.8 for amoxicillin/clavulanate, a factor of 6.6 for aminoglycosides, a factor of 5.3 for penicillins and a factor of 2.8 for cephalosporins. Even among departments within hospitals, there was a difference of up to 1.5-fold for total use and antibiotic class differences ranged between 2.5- and 7.2-fold for third- and fourth-generation cephalosporins, despite similar Charlson scores and other patient variables. In the multivariate analysis, hospital affiliation and rate of 1 day hospitalization were the only significant variables predicting total antibiotic use, contributing 43% and 7.3%, respectively, to the variance. By antibiotic class, controlling for hospital affiliation, patients with neutropenia, lower respiratory tract infections and assisted ventilation were the most common significant contributors, ranging from 3.5% for quinolones to 7.7% for piperacillin/tazobactam.

CONCLUSIONS

Patterns of antibiotic use vary widely among internal medicine departments in Israel, which cannot be explained by objective parameters related either to patients or wards. Ongoing monitoring and guideline formulation are needed to regulate antibiotic prescription.

Attributable mortality of Acinetobacter baumannii: no longer a controversial issue

There has been controversy regarding the mortality directly attributed to Acinetobacter baumannii infections. Data from six case–control studies have been recently added to the literature regarding the attributable mortality of A. baumannii infections during the past months. The information from these studies, added to the previous knowledge on this issue, provides evidence that A. baumannii infections are indeed associated with increased mortality. In addition, there is relevant evidence from studies examining the effect of inappropriate treatment on mortality; specifically, inappropriate treatment of A. baumannii infections has been associated with excess mortality. We believe that the accumulated data suggest that attributable mortality due to A. baumannii infections should no longer be a controversial issue. The efforts of the scientific community interested in this pathogen should therefore be directed to the development and introduction of new antibiotics effective against multidrug-resistant and pandrug-resistant A. baumannii as well as the implementation of infection control measures that may help us in the control of the increasing problem of A. baumannii infections.

Therapeutic options for Acinetobacter baumannii infections

Acinetobacter baumannii is an important cause of nosocomial infections, mainly in patients in intensive care units. This microorganism, although with slight differences depending on the country, presents resistance to multiple antimicrobial agents, occasionally including resistance to colistin: hence, it can be considered the paradigm of nosocomial multiresistant bacteria. This review analyzes the evolution of antimicrobial resistance and the molecular bases associated with the increase in antimicrobial resistance, as well as the current treatment of Acinetobacter infections. Although controversy remains, the pooled data suggest that infections by A. baumannii may be associated with considerable attributable mortality. Moreover, in cases of pneumonia and bacteraemia, inappropriate treatment is associated with, among other factors, mortality. Therefore, treatment should be carefully considered.

Sequential outbreaks of infections by distinct Acinetobacter baumannii strains in a public teaching hospital in Houston, Texas

Invasive disease due to Acinetobacter baumannii is an increasing problem in health care settings worldwide. Whether certain clones of A. baumannii are more likely to cause invasive disease in hospitalized patients is unknown. We studied all patients at a public teaching hospital in Houston, Texas, from whom the Acinetobacter calcoaceticus-Acinetobacter baumannii complex was isolated over a 14-month period in 2005 to 2006. One hundred seven unique patient isolates were identified, with 87 of the strains classified as being A. baumannii, the majority of which were multidrug resistant. The A. baumannii isolates were comprised of 18 unique pulsed-field types, with strains of clone A and clone B accounting for 66 of the 87 isolates. Epidemiologic analysis showed the predominance of the two A. baumannii clones at distinct time periods, with the remainder of the A. baumannii and non-A. baumannii strains being evenly distributed. Patients from whom clone A strains were isolated were more likely to be bacteremic than were patients with other A. baumannii isolates. Conversely, clone B strains were more likely to be isolated from patients with tertiary peritonitis. Patients from whom clone A was isolated had a significantly higher rate of mortality. Multilocus sequence typing demonstrated that clones A and B are related to each other and to A. baumannii strains previously isolated in Western Europe, sharing five of seven alleles. Taken together, we conclude that the outbreak of the A. calcoaceticus-A. baumannii complex in our institution was due to two distinct A. baumannii clones that were associated with significantly different patient outcomes.