Resistant gram-negative infections in a pediatric intensive care unit: a retrospective study in a tertiary care center

Aim:

Healthcare-associated infections cause increased morbidity and mortality in intensive care units. In this study, it was aimed to compare infections with multi-drug resistance and extended drug resistance, while evaluating the characteristics of resistant Gram-negative infections in the pediatric intensive care unit in our university hospital.

Material and Methods:

In this study, pediatric patients who were found to have Gram-negative infections during hsopitalization in the pediatric intensive care unit in our faculty between January 2011 and December 2015, were evaluated retrospectively.

Results:

One thousand thirty patients were internalized in our unit in the study period. The incidence for healthcare-associated infection was found as 17.2% and the incidence density was found as 32.7 per 1000 patient days. The incidence for healthcare-related infection per 1000 device days and the rate for device use were calculated as 66.9 and 0.59, respectively. One hundred thirty Gram-negative infection episodes were found in 79 patients whose median age was 22 (1–205) months. The most common infections included ventilator-related pneumonia (n=78, 60%) and bloodstream infections (n=38, 29.2%). The most common causative agents included Pseudomonas aeruginosa (n=50, 38.5%), Kleibsiella pneumonia (n=32, 24.6%) and Acinetobacter baumannii (n=28, 21.5%). Among A. baumannii isolates, the rates for resistance against piperacillin-tazobactam and meropenem were found as 96.4% and 89.3%, respectively. Empirical use of carbapenems, aminoglycosides, and fluoroquinolones, the presence of total parenteral nutrition and history of Gram-negative bacterial infections prior to pediatric intensive care unit admission were significantly more common among extended-drug Gram-negative bacterial infections. The late mortality rate was found to be higher in presence of extended drug resistance. History of Gram-negative infection was found to be an independent risk factor in terms of extended drug resistance.

Conclusion:

Healthcare-associated infections are an important health problem and it is important for infection control committees of hospitals to determine and apply strategies according to hospital colonization in prevention.

Mutant prevention concentrations of four carbapenems against gram-negative rods

We tested the propensities of four carbapenems to select for resistant Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii mutants by determining the mutant prevention concentrations (MPCs) for 100 clinical strains with various ss-lactam phenotypes. Among the members of the Enterobacteriaceae family and A. baumannii strains, the MPC/MIC ratios were mostly 2 to 4. In contrast, for P. aeruginosa the MPC/MIC ratios were 4 to > or =16. The MPC/MIC ratios for beta-lactamase-positive K. pneumoniae and E. coli isolates were much higher (range, 4 to >16 microg/ml) than those for ss-lactamase-negative strains.

Detecting imipenem resistance in Acinetobacter baumannii by automated systems (BD Phoenix, Microscan WalkAway, Vitek 2); high error rates with Microscan WalkAway

Background

Increasing reports of carbapenem resistant Acinetobacter baumannii infections are of serious concern. Reliable susceptibility testing results remains a critical issue for the clinical outcome. Automated systems are increasingly used for species identification and susceptibility testing. This study was organized to evaluate the accuracies of three widely used automated susceptibility testing methods for testing the imipenem susceptibilities of A. baumannii isolates, by comparing to the validated test methods.

Methods

Selected 112 clinical isolates of A. baumanii collected between January 2003 and May 2006 were tested to confirm imipenem susceptibility results. Strains were tested against imipenem by the reference broth microdilution (BMD), disk diffusion (DD), Etest, BD Phoenix, MicroScan WalkAway and Vitek 2 automated systems. Data were analysed by comparing the results from each test method to those produced by the reference BMD test.

Results

MicroScan performed true identification of all A. baumannii strains while Vitek 2 unidentified one strain, Phoenix unidentified two strains and misidentified two strains. Eighty seven of the strains (78%) were resistant to imipenem by BMD. Etest, Vitek 2 and BD Phoenix produced acceptable error rates when tested against imipenem. Etest showed the best performance with only two minor errors (1.8%). Vitek 2 produced eight minor errors(7.2%). BD Phoenix produced three major errors (2.8%). DD produced two very major errors (1.8%) (slightly higher (0.3%) than the acceptable limit) and three major errors (2.7%). MicroScan showed the worst performance in susceptibility testing with unacceptable error rates; 28 very major (25%) and 50 minor errors (44.6%).

Conclusion

Reporting errors for A. baumannii against imipenem do exist in susceptibility testing systems. We suggest clinical laboratories using MicroScan system for routine use should consider using a second, independent antimicrobial susceptibility testing method to validate imipenem susceptibility. Etest, whereever available, may be used as an easy method to confirm imipenem susceptibility.