Characterisation of Nonfermenting Gram Negative Bacilli in Clinical Specimens and Molecular Typing of Drug Resistance.

Jayapriya, S (2010) Characterisation of Nonfermenting Gram Negative Bacilli in Clinical Specimens and Molecular Typing of Drug Resistance. Masters thesis, Madras Medical College, Chennai.


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INTRODUCTION : Nonfermentative Gram negative bacilli (NFGNB) are a group of aerobic, non Spore forming organisms that either do not use carbohydrates as a source of energy or Degrade them through metabolic pathways other than fermentation. These bacteria are ubiquitous in nature particularly in soil and water. Although frequently considered as contaminants, most of the nonfermenting gram negative bacilli have emerged as important nosocomial pathogens causing opportunistic infections in Immmunocompromised hosts. Humidifiers, ventilator machines, dialysate fluids and catheter devices in the hospital environment have provided opportunities for these organisms to establish infection. Non-fermenting Gram negative bacilli cause variety of infections including Urinary tract infections, wound infections, septicemia, pneumonia, osteomyelitis, Meningitis etc. They are being recovered with increasing frequency from clinical specimens. Chronic infection, longer duration of hospitalization and prolonged antibiotic therapy are the predisposing factors for infection with nonfermenters. This group includes organisms from diverse genera like Pseudomonas, Acinetobacter, Stenotrophomonas, Burkholderia, Alcaligenes, Weeksella etc, with Pseudomonas Aeruginosa being the predominant species recovered from clinical specimens. The present study was therefore undertaken to identify the nonfermenters from various clinical specimens, to analyse the risk factors associated with their infections, to Determine the multidrug resistance and to guide initial empiric therapy for infections caused by them. AIMS AND OBJECTIVES : To isolate and speciate the nonfermenters from various clinical specimens. To study the sensitivity patterns of the isolates with common antimicrobials. To detect the incidence of multidrug resistance among nonfermenters. To detect the production of extended spectrum of betalactamases. To detect the acquired resistance to carbapenam antibiotics and production of acquired metallobetalactamases (MBL). To identify the genes responsible for acquired MBL production. To formulate antibiotic therapy for the infections caused by nonfermenters. MATERIALS & METHODS : All statistical analyses were carried out using SPSS for Windows. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated. P values were calculated using the chi-square test. A P value of < 0.05 was considered significant. A total of 156 nonfermenting bacteria isolated from various clinical specimens like pus, urine, blood, bronchoalveolar lavage, endotracheal aspirations, drain tip and cerebrospinal fluids collected from both outpatients and inpatients of Government General Hospital, Chennai were studied. CONCLUSION : Observations from the present study showed the aerobic NFGNB which are usually considered as contaminants are now emerging as important nosocomial pathogens. The various clinical specimens from which they were isolated proved their existence in all sites leading to a range of diseases. Different sensitivity pattern and multidrug resistance exhibited by nonfermenters pose a great problem in treating these infections. ESBL and MBL production by these organisms lead to high morbidity and mortality as we are left with the only option of treating them by potentially toxic agents like Colistin and Polymyxin B. Awareness of their entry into a hospital environment is the first step that clinical microbiologists can take to address this problem. Care in detection, evaluation of effective antibiotic options, judicious use of antibiotics by instituting antibiotic policy of combination therapy and rigorous infection control measures will help to fight against these multidrug resistant nonfermenters in the effective management of patients.

Item Type: Thesis (Masters)
Uncontrolled Keywords: Characterisation ; Nonfermenting Gram Negative Bacilli ; Clinical Specimens ; Molecular Typing of Drug Resistance.
Subjects: MEDICAL > Microbiology
Depositing User: Subramani R
Date Deposited: 03 Aug 2017 02:26
Last Modified: 03 Aug 2017 02:26

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