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| Year:
2015 |
Month:
July
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Volume:
4 |
Issue:
3 |
Page:
55 - 60 |
Phenotypic and Molecular Characterisation of Carbapenemases in Acinetobacter Species in a Tertiary Care Centre in Tamil Nadu, India
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Correspondence
Padmalakshmi Y., Shanthi M., Uma Sekar, Arunagiri K., Pugazhenthen,
Dr. Padmalakshmi Y.,
AP 1048, G-block, 17th Street, Belly Area, Annanagar, Chennai-600040,
India.
E-mail: padmalakshmikailash@gmail.com :
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Introduction: Acinetobacters are significant nosocomial pathogens involved in outbreaks of infection in intensive care unit. Carbapenem resistance in Acinetobacter species is due to a variety of combined mechanisms and is a cause of great concern
Aims: The current study was conducted to determine the antimicrobial susceptibility pattern and prevalence of carbapenemases amongst the Acinetobacter species.
Materials and Methods: The study was conducted in a 1850 bedded university teaching hospital between November 2013 to April 2014. One hundred and fifty seven consecutive Acinetobacter isolates were subjected to Modified Hodge test & inhibitor potentiated disc diffusion test for screening of carbapenemases & metello-beta-lactamases. Antibiotic susceptibility was performed by Kirby-Bauer’s disc diffusion method to detect resistance to various drugs. PCR was performed for detection of genes encoding OXA carbapenemases and metallo-beta-lactamases. Study Design: Laboratory based cross sectional study.
Results: Out of 157 isolates (151 A.baumannii and 6 A. lwoffii), 110 (70%) exhibited carbapenem resistance. MIC50 to imipenem was 32 µg/mL. Modified Hodge test was positive in 90 (57.3%). Metallo-beta-lactamase screening test was positive in 126 (80.2%). All the 90 MHT positive isolates carried different OXA or the MBL genes. Of 126 MBL screen positive isolates VIM, IMP & NDM encoding genes were detected in 69 isolates. Of the total 157 Acinetobacter isolates, blaOXA 23 was detected in 71, blaOXA 24 and blaOXA 58 in 6 each. BlaVIM, blaIMP , blaNDM were detected in 49, 4, 27 Acinetobacter isolates respectively.
Conclusion: BlaOXA 23 was the most common OXA carbapenemase. BlaVIM was the most common metallo-beta-lactamase. Coproduction of OXA and metallo-beta-lactamases (33.7%) is not an uncommon phenomenon. Production of carbapenemase is the most important reason for imipenem resistance in Acinetobacter species in our health care setting. Since the screening tests perform poorly, early detection of the drug resistance genes by molecular methods is necessitated.
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