Detection of Oxacillinase Genes that confers Carbapenem Resistance in Acinetobacter Baumannii, in Hospital Acquired Infections.

Sudhir, Babji (2009) Detection of Oxacillinase Genes that confers Carbapenem Resistance in Acinetobacter Baumannii, in Hospital Acquired Infections. Masters thesis, Christian Medical College, Vellore.


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INTRODUCTION : Acinetobacter calcoaceticus-baumannii is a non fermenting gram negative bacilli or cocco bacilli belonging to the family Moraxellaceae. It is a ubiquitous organism found in soil, sewage, and dry surfaces. They can be readily isolated from areas of moist skin such as toe webs, groin, and the axilla. The organism can be identified from hospital equipment such as ventilators, curtains, telephones, door handles. It was until recently, dismissed as a non pathogen, contaminating clinical specimens. Of late the organism has been recognized as a nosocomial pathogen and has been, increasingly so, in patients admitted in intensive care units, on mechanical ventilation and on central venous catheters. It has emerged as a leading cause of Ventilator Associated pneumonia (VAP). The organism has low virulence potential, but with the emergence of multidrug and pan drug resistant strains, this organism has emerged as a leading cause of mortality, morbidity, and increased hospital cost and duration of hospitalization. In the year 1984, Acinetobacter spp. was classified in the family Neisseriaceae, but more recently the molecular taxonomic studies have resulted in the reclassification of the organism in the new family of Moraxellaceae in 1991. AIM & OBJECTIVES : Aim: To detect the various genes those encodes for carbapenem resistance in clinical isolates of A.baumannii and ascertain the molecular marker for rapid detection for the same. Objectives: 1. To identify A.baumannii phenotypically. 2. To evaluate OXA-51 for identification of A.baumannii. 3. To determine the gene encoding for carbapenem resistance (OXA-51 and OXA-23). 4. To determine the prevalent antimicrobial susceptibility profile among our study isolates. 5. To determine the susceptibility of carbapenem resistant A.baumannii to Tigecycline by disc diffusion method. 6. To determine the baseline MIC value for drugs of renewed interest (Polymyxins, Sulbactam) against carbapenem resistant nosocomial A.baumannii. 7. To investigate for presence of other resistance genes in representative isolates. 8. To correlate the outcome in patients infected with carbapenem and Tigecycline Resistant strains. 9. To correlate clinically the outcome using Clinical Pulmonary Infection Score (CPIS) and Charlson Co-morbidity Index (CCI). MATERIALS AND METHODS : A total of 100 isolates of Acinetobacter calcoaceticus-baumannii complex were enrolled in this study. The isolates were from various clinical materials sent to the Clinical Microbiology department for bacteriological culture, biochemical identification, and antibiotic susceptibility testing. Isolates included in this study were obtained from blood, sputum, Endo tracheal aspirate, tracheal aspirate, central lines, cerebrospinal fluid, wound swabs, infected tissue. The isolates were collected form patients, who were diagnosed to have nosocomial infections defined as infections developing 48 hours after hospital admission. Samples collected for a period of 1 year, i.e. samples coming during the time period from, December 2006 to December 2007 were included in this study. CONCLUSIONS : Conclusions and summary The total number of nosocomial A.baumannii isolates included in this study was one hundred. 78% of the isolates included in this study were isolated from nosocomial pneumonia. This indicates that A. baumannii is a leading cause of nosocomial pneumonia. The resistance to β-lactam agents was 100%, to amino glycosides and fluoroquinolones was 85% and to the β-lactam +β-lactamase inhibitor combination was 79%. The number of PDR A.baumannii was 57% and MDR A.baumannii was 43%. The number of isolates being resistant to so many anti microbial agents is indeed concerning. Efficacy of the newer drug being advocated as a treatment option for carbapenem resistant A.baumannii - Tigecycline was evaluated in our study isolates. None of the isolates tested, were susceptible to Tigecycline with only seven of the isolates being intermediately susceptible. The lack of standard break points for defining susceptibility or resistance has also partially lead to varied results across the world.

Item Type: Thesis (Masters)
Uncontrolled Keywords: Oxacillinase Genes ; Carbapenem Resistance ; Acinetobacter Baumannii ; Hospital ; Acquired Infections.
Subjects: MEDICAL > Microbiology
Depositing User: Subramani R
Date Deposited: 14 Aug 2017 01:40
Last Modified: 14 Aug 2017 01:40

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