CHARACTERIZATION OF CARBAPENEM RESISTANT ACINETOBACTER BAUMANNII ISOLATED IN A TERTIARY CARE HOSPITAL: EPIDEMIOLOGY AND TREATMENT OUTCOME
Keywords:
Acinetobacter baumannii, Carbapenem resistance, Carbapenemases, Colistin combination, Nil, NDMAbstract
Objective: Carbapenem resistant Acinetobacter baumannii (CR-Ab) has emerged as a major nosocomial pathogen, but optimal treatment regimens are unknown. Our objectives were to determine the epidemiology and outcome of CR-Ab infections at a tertiary care hospital.
Methods: CR-Ab isolates were collected from January to April 2013. MICs were determined and isolates were subjected to screening for carbapenemase production by Modified Hodge test (MHT), metallo-β-lactamase (MBLs) by EDTA disk synergy test and AmpC β-lactamase by AmpC disk test. 15 isolates were subjected to PCR for detection of resistant genes, blaOXA-23, blaVIM and blaNDM. Treatment outcomes of infections were evaluated.
Results: 51 CR-Ab isolates from tracheal aspirate (21), blood (15); tissue/wound/drainage (13) and urine samples (2) were collected. Colistin appeared to be the most effective agent with 98% in vitro activity. MHT showed 98% positivity, MBLs production was detected in 94.1% isolates and 64.7% were positive for AmpC β-lactamase production. All 15 isolates carried blaOXA-23 and blaVIM, of these 3 also carried blaNDM gene. Colistin containing combinations were more commonly used (68.3%). Colistin-noncarbapenem combination showed improved clinical response compared to colistin-carbapenem combination against Acinetobacter isolates carrying blaOXA-23 and blaVIM.
Conclusion: A stringent infection control practice along with antimicrobial stewardship is needed to prevent emergence of Acinetobacter carrying multiple carbapenemase genes along with blaNDM. Various colistin combinations are preferentially used to treat CR-Ab infections. Identification of antimicrobial combinations with proven in vitro activity that encompass local susceptibility patterns as well as molecular mechanisms of resistance is needed to provide better outcome.
Keywords: Acinetobacter baumannii, Carbapenem resistance, Carbapenemases, Colistin combination, metallo-β-lactamase, NDMÂ
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