Ali Khalid

Evaluation of different detection methods of biofilm formation in the clinical isolates

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.

Current status of vancomycin susceptibility against methicillin resistant Staphylococcus aureus (MRSA) strains: A study at two tertiary care hospitals of Pakistan

Vancomycin has been considered mainstay treatment of infections caused by methicillin-resistant Staphylococcus aureus. The reports of the emergence of vancomycin intermediate and vancomycin resistant S. aureus from various parts of the world have been of great clinical concern. This study was performed to monitor the status of glycopeptide susceptibility against methicillin resistant S. aureus in our set up. All non-duplicate methicillin resistant Staphylococcus aureus (MRSA) isolates recovered during the period of study from various wards of Military Hospital Rawalpindi and PAEC General Hospital Islamabad, were subjected to the detection of minimum inhibitory concentrations of vancomycin using E-strips. Results were analyzed to evaluate the possible presence of vancomycin intermediate and resistant strains in the set up. A total of 276 methicillin-resistant S. aureus isolates were studied. The range of vancomycin minimum inhibitory concentrations (MIC) was 0.19 to 3 ug/mL. MIC 50 came out to be 0.75 ug/mL whereas the MIC 90 was 1.5 ug/ mL. 128 out of 276 (46%) isolates had vancomycin MIC equal to or greater than 1 ug/mL. Majority of the isolates (69%) were from pus samples. No vancomycin resistant or intermediate strain of MRSA was isolated during the study but there were a significant number of isolates having ≥ 1 µg/ml MIC of vancomycin.