ABSTRACT
Objective: To determine the prevalence of Amp C beta lactamases in urinary isolates of Escherichia coli [E. coli], and to evaluate and compare different phenotypic methods for its detection in a cost effective way
Study Design: Descriptive study
Place and Duration of Study: Department of Microbiology, Combined Military Hospital Lahore Pakistan, from Jan 2016 to Jun 2016
Material and Methods: Modified Three Dimensional Test [M3DT] taken as Gold standard, Modified Hodge Test [MHT] [Cefoxitin], Nitrocephin test and three screening strategies for the detection of Amp C Beta-lactamases were tested on urinary isolates of E. coli collected during a period of 06 months
Results: Modified Hodge Test, was found to be simple, highly specific and sensitive in detecting these enzyme producers. Collectively these tests detected 45.07% of E. coli to be Amp C producers
Conclusion: Each of the three tests can be used as an acceptable phenotypic confirmatory tool when Amp C production in E. coli is suspected
ABSTRACT
Aims: Infections due to metallo-β-lactamase (MBL) producing Gram negative rods are a cause of high mortality and morbidity. Early detection by an economical and accurate method may improve patient outcome. This study was aimed to evaluate the diagnostic accuracy of combined disc method for MBL detection by comparing it with MBL-Etest. Methodology and Results: This cross-sectional, validation study was carried out in the Department of Microbiology, Army Medical College, National University of Sciences and Technology, Rawalpindi, over a period of six months. A total of 52 non-duplicate Gram-negative rods isolated from the routine clinical specimens and found resistant to meropenem/imipenem on Kirby Bauer Disc Diffusion method were subjected to two tests for metallo-β-lactamase detection. One was combined Disc test using imipenem with Ethylene Diamine Tetraacetic Acid (EDTA), where a strain showing an increase in zone of inhibition of combined disc of ≥ 7 mm as compared to imipenem alone, was considered as MBL producer and the other one was MBL-Etest for which results were interpreted as per manufacturer’s guidelines. Combined disc method for MBL detection was found to have a sensitivity, specificity, positive predictive value, negative predictive value and accuracy of 97.5%, 100%, 100%, 92% and 98%. Conclusion, Significance and Impact of study: Combined disc method is an economical and reliable method for metallo-β-lactamase detection which can be used routinely in any laboratory.
ABSTRACT
To find out the frequency and susceptibility pattern of multi-drug resistant [MDR] Pseudomonas aeruginosa in clinical specimens. Cross-sectional observational study. Department of Microbiology, Army Medical College, National University of Sciences and Technology [NUST], Rawalpindi, from January to September 2010. 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. 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. Increasing fequency of infections due to MDR Pseudomonas aeruginosa is an emerging threat in our set up which can be prevented by prescribing antibiotics judiciously and by adopting proper disinfection measures
ABSTRACT
To assess the reliability of Manitol salt agar [MSA] for directly identifying Methicillin Resistant Staphylococcus aureus [MRSA] and Methicillin Resistant Coagulase negative Staphylococci, [MRCoNS] in nasal swabs for screening purposes using cefoxitin and oxacillin disks. Descriptive and Quasi-experimental. The study was done in the two surgical units of Combined Military Hospital, Rawalpindi and all the samples were processed at the Department of Microbiology, Armed forces Institute of Pathology, Rawalpindi during July 2007. A total of eighty four duplicate swabs were taken from the anterior nares of various staff members of the two surgical units and were directly inoculated on Mannitol salt agar with Cefoxitin disc 30 micro g [MSAFOX] and oxacillin disc 1 micro g [MSAOX]. All the samples were simultaneously inoculated on blood and MacConkey agar for conventional testing, using standard conditions, and confirmed as MRSA or MRCoNS by oxacillin disk diffusion technique. The staphylococcal isolates were later confirmed as MRSA/MRCoNS by polymerase chain reaction [PCR] for mec A gene analysis. There were 45 staphylococci which revealed mec A gene [40 MRCoNS and 5 MRSA] by PCR. Both the disks with MSA effectively identified the methicillin resistance. MSA with cefoxitin could identify 40 methicillin resistant staphylococci [35 MRCoNS and 5 MRSA] where as MSA with oxacillin could identify 39 methicillin resistant staphylococci [34 MRCoNS and 4 MRSA]. There was no significant difference between the two disks in sensitivity, specificity, positive and negative predictive values and overall efficacy of the procedures. MSA with cefoxitin 30 micro g and oxacillin 1 micro g appear to be highly accurate, easy to perform and beneficial for quick and reliable detection of methicillin resistant staphylococci from the nasal carriers in a routine microbiology laboratory
Subject(s)
Nose/microbiology , Microbial Sensitivity Tests , Agar , Culture Media , Cefoxitin , Oxacillin , Polymerase Chain ReactionABSTRACT
To compare the accuracy of Mueller-Hinton agar and Isosensitest agar using cefoxitin disc for detecting methicillin resistant Staphylococcus aureus using mecA gene PCR assay as gold standard. Comparative study. Department of Microbiology, Armed Forces Institute of Pathology, Rawalpindi, from May 2006 to January 2007. One hundred clinical isolates of Staphylococcus aureus were evaluated; 64 MRSA [methicillin resistant Staphylococcus aureus] and 36 MSSA [methicillin sensitive Staphylococcus aureus] by mecA PCR assay All the isolates were tested with cefoxitin 30 micro g disc using semi-confluent growth on Mueller-Hinton agar as well as on Iso-sensitest agar in ambient air at 35-37°C after an overnight incubation as per recommendations of Clinical and Laboratory Standard Institute. Following diameters provided the best sensitivity and specificity without substantial overlapping between the zones of resistant and sensitive isolates; Mueller-Hinton agar: R /= 22 mm [sensitivity 97.2% and specificity 100%], and Iso-sensitest agar: R /= 26 mm [sensitivity 100% and specificity 100%]. High accuracy was obtained with cefoxitin disc on both media. Performance of both media was equally convincing for reliable prediction of methicillin resistance in Stapfylococcus aureus by placing cefoxitin 30 micro g disc on either of these in routine susceptibility testing