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Objective: To compare the in vitro efficacy of meropenem, colistin and tigecycline against extended spectrum Betalactamase producing Gram negative bacilli by minimal inhibitory concentration., Study Design: Cross-sectional descriptive study., Place and Duration of Study: Department of Microbiology, Army Medical College, National University of Sciences and Technology, Rawalpindi, from June to December 2010., Methodology: Routine clinical specimens were subjected to standard microbiological procedures and the isolates were identified to species level. Extended spectrum β-lactamase producing Gram negative bacilli were detected by Jarlier disc synergy method and confirmed by ceftazidime and ceftazidime-clavulanate Etest. Minimum Inhibitory Concentration (MIC(90)) of meropenem, colistin and tigecycline was determined by Etest (AB BIOMERIUX) and the results were interpreted according to the manufacturer's instructions and Clinical and Laboratory Standards Institute guidelines and Food and Drug Authority recommendations. Results were analyzed by using Statistical Package for the Social Sciences version 20., Results: A total of 52 non-duplicate extended spectrum Beta-lactamase-producing Gram negative bacilli were included in the study. The MIC(90) of tigecycline (0.75 µg/ml) was lowest as compared to the meropenem (2 µg/ml) and colistin (3 µg/ml)., Conclusion: Tigecycline is superior in efficacy against the extended spectrum Beta-lactamase producing Gram negative bacilli as compared to colistin and meropenem.

Multi-drug resistant bacteria are an important cause of mortality and morbidity. In the management of various infections, timely detection and appropriate treatment, in accordance with the culture and sensitivity reports can help improve the treatment outcome. Colistin is a bactericidal antibiotic which is emerging as a reliable solution for treating infections with multi-drug resistant Gram negative bacilli. The aim of this study was to find out the in-vitro efficacy of colistin against multidrug resistant Pseudomonas aeruginosa isolates by minimum inhibitory concentration. This cross sectional, descriptive study was conducted in the Department of Microbiology, Army Medical College, National University of Sciences and Technology, Islamabad from February 2010 to January 2011. Antimicrobial sensitivity testing was done on Pseudomonas aeruginosa isolated from routine clinical specimens received and the strains which appeared resistant to at least one antimicrobial agent in three or more anti-pseudomonal antimicrobial categories were subjected to the Colistin Etest. The MIC endpoint of colistin was read, as per manufacturers instructions (AB Biodisk, Solna, Sweden). The isolates showing MIC of 2μg/ml or less were considered sensitive, those with 4-6μg/ml as intermediate and >μg/ml as resistant. MIC(50) and MIC(90) of colistin against MDR Pseudomonas aeruginosa was determined. A total of 52 MDR Pseudomonas aeruginosa strains were isolated during the period of the study. The highest percentage was isolated from urine (36%) followed by respiratory tract infections (18%) and pus specimens (20%). The highest percentage of these isolates was found to be susceptible to colistin followed by piperacillin-tazobactam and cefoperazone-sulbactam. A total of 36(69%) isolates were sensitive, 10(20%) were intermediate and 6(11%) were resistant to colistin by Kirby Bauer disc diffusion method. MIC(50) was found to be 1.0μg/ml while MIC(90) was 3.0μg/ml. Colistin is a reliable solution in cases of infections with MDR, XDR or PDR Pseudomonas aeruginosa.

Objective: To find out the frequency and susceptibility pattern of multi-drug resistant (MDR) Pseudomonas aeruginosa in clinical specimens., Study Design: Cross-sectional observational study., Place and Duration of Study: Department of Microbiology, Army Medical College, National University of Sciences and Technology (NUST), Rawalpindi, from January to September 2010., Methodology: Routine clinical specimens were subjected to standard microbiological procedures and the isolates were identified to the species level. The antibiotics susceptibility was determined by Kirby Bauer Disc diffusion method and the results were interpreted according to the Clinical and Laboratory Standards Institute (CLSI) guidelines., Results: The frequency of MDR Pseudomonas aeruginosa among all the Pseudomonas aeruginosa strains isolated was found to be 22.7%. These isolates were most sensitive to Colistin followed by Piperacillin-Tazobactam and Cefoperazone-Sulbactum., Conclusion: Increasing fequency of infections due to MDR Pseudomonas aeruginosa is an emerging threat in our set up which an be prevented by prescribing antibiotics judiciously and by adopting proper disinfection measures.

Background: Microorganisms growing in a biofilm are associated with chronic and recurrent human infections and are highly resistant to antimicrobial agents. There are various methods to detect biofilm production like Tissue Culture Plate (TCP), Tube method (TM), Congo Red Agar method (CRA), bioluminescent assay, piezoelectric sensors, and fluorescent microscopic examination., Objective: This study was conducted to compare three methods for the detection of biofilms., Method: The study was carried out at the Department of Microbiology, Army Medical College, National University of Sciences and Technology, Pakistan, from January 2010 to June 2010. A total of 110 clinical isolates were subjected to biofilm detection methods. Isolates were identified by standard microbiological procedures. Biofilm detection was tested by TCP, TM and CRA. Antibiotic susceptibility test of biofilm producing bacteria was performed by using the Kirby-Bauer disc diffusion technique according to CLSI guidelines., Results: The TCP method was considered to be superior to TM and CRA. From the total of 110 clinical isolates, TCP method detected 22.7% as high, 41% moderate and 36.3% as weak or non-biofilm producers. We have observed higher antibiotic resistance in biofilm producing bacteria than non-biofilm producers., Conclusion: We can conclude from our study that the TCP method is a more quantitative and reliable method for the detection of biofilm forming microorganisms as compared to TM and CRA methods, and it can be recommended as a general screening method for detection of biofilm producing bacteria in laboratories.

Objectives: To compare the in vitro activities of vancomycin and linezolid against methicillin resistant Staphyloccus aureus in our set up to help in formulating a better empirical treatment and reduce the emergence of vancomycin resistant Staphylococcus aureus., Methods: The study was conducted over a period of 6 months (1st July 2009-31st Dec 2009). Fifty Methicillin resistant Staphylococcus aureus isolated from the clinical isolates of Military Hospital Rawalpindi were subjected to the determination of Minimum inhibitory concentrations of linezolid and vancomycin using E-strips., Results: All the isolated organisms were uniformly susceptible to both the antibiotics. Vancomycin showed higher minimum inhibitory concentrations (MICs) as compared to linezolid MICs., Conclusion: This study suggests that linezolid and vancomycin have similar in vitro efficacy for methicillin resistant Staphyloccus aureus infections.