Thiriveni, J (2015) Speciation of Acinetobacter Isolates and Detection of Resistance Patterns by Phenotypic and Genotypic Method. Masters thesis, Madras Medical College, Chennai.
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Abstract
INTRODUCTION: The Genus Acinetobacter are a group of Non-fermentative Gram negative bacteria found extensively in natural environment, resulting in colonization and infection. Acinetobacter species are the second most common nonfermenter isolated from clinical specimens. The infections caused by MDR Acinetobacter that are capable of producing various beta lactamases are associated with significant morbidity and mortality. Hence Acinetobacter has been added to the list of significant microbial challenges of current era. AIM AND OBJECTIVES: To determine the prevalent antimicrobial susceptibility pattern and various resistance patterns conferred by beta lactamases among the clinical isolates of Acinetobacter species, both by phenotypic and genotypic method and to correlate the clinical outcome in the patients. MATERIALS AND METHODS: About 175 clinically significant, consecutive, non duplicate Acinetobacter isolates from various clinical specimens were included in this study. The isolates were identified by standard protocols. ESBL production was confirmed by CLSI phenotypic confirmatory method, AmpC production was confirmed by AmpC disc test and carbapenamase production was detected using Modified Hodge test and Imipenem-EDTA combined disc test. Carbapenem resistance gene (OXA-23, blaVIM1 & blaIMP1) was identified by PCR. RESULTS: Acinetobacter baumannii (81.14%) was the most common species isolated followed by A.lwoffii (10.29%), A.calcoaceticus (4.57%) and A.junii (4%). The maximum isolates were from respiratory samples 63(36.00%) and from patients in ICU. There was a significant difference (p value <0.05) between the antimicrobial sensitivity pattern of A.baumannii and other species. MDR in Acinetobacter spp. was found to be 60%. XDR was found to be 11.43% and there were no PDR isolate in this study. 20 isolates (11.43%) were found to be resistant to meropenem. MIC values were between 32μg/ml and 256μg/ml. Modified Hodge test was positive in 9 (45%) isolates and IEDT was positive in 9 (45%) isolates of the 20 meropenem resistant isolates. 61 (34.86%) isolates were found to be ESBL producers and 23 (13.14%) isolates were found to be AmpC producers. OXA-23 was positive in all 20 isolates (100%), blaVIM1 was positive in 9isolates (45%) and blaIMP1 was positive in 7isolates (35%). DISCUSSION: Acinetobacter species are very notorious for their ability to acquire antibiotic resistance because of its potential to respond quickly to the changes in selective environmental pressure. A.baumannii was the most common species isolated and found to be more resistant when compared to other species. MDR Acinetobacter infections were predominant and XDR Acinetobacter infections have also been recorded but no PDR Acinetobacter were isolated in this study. Extended spectrum beta lactamases and AmpC beta lactamases were also detected in a significant number. Carbapenems remain the drug of choice for the MDR acinetobacter infections. But resistance to carbapenems due to production of various beta lactamases is of great concern as they are encoded by genes which are horizontally transmissible. There is difference between phenotypic and genotypic methods in the sensitivity of detection of carbapenamases where genotypic methods are more sensitive and remain the gold standard. CONCLUSION: The high prevalence of Acinetobacter infections emphasizes the need for early detection of various beta lactamases, which would help in selection of appropriate antibiotic regimen and prevention of emergence and dissemination of MDR strains.
| Item Type: | Thesis (Masters) |
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| Uncontrolled Keywords: | Multi drug resistant (MDR) ; Extended drug resistant (XDR) ; Pan drug resistant (PDR) ; Extended spectrum beta lactamase (ESBL) ; Modified Hodge test (MHT) ; Imipenem EDTA combined disc test (IEDT). |
| Subjects: | MEDICAL > Microbiology |
| Depositing User: | Punitha K |
| Date Deposited: | 23 May 2018 02:52 |
| Last Modified: | 27 May 2018 04:41 |
| URI: | http://repository-tnmgrmu.ac.in/id/eprint/8024 |
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