Aerobic Micro-Organisms In Post-Operative Wound Infections And Their Antimicrobial Susceptibility Patterns
Amrita S, Dept. of Microbiology, A.J.I.M.S, Kuntikana, Mangalore-575004
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Purpose: Post-operative wound infections have been an important cause of morbidity and cost burden for the patients. (1) The objective of this study was to evaluate the antimicrobial susceptibility pattern among the most common bacteria which are associated with post-operative wound infections.
Method: 84 isolates were obtained from 100 pus samples / wound swabs which were collected from clinically suspected post-operative wound infections. The bacteria were cultured on Blood agar, Mac Conkeyâ€™s agar and Nutrient agar, followed by the identification of the isolates based on their cultural characteristics and their reactions in standard biochemical tests. All the isolates were tested for antimicrobial susceptibility by the disk diffusion technique according to the Clinical and Laboratory Standards Institute (CLSI) guidelines on Muller Hinton Agar. The screening for extended spectrum beta lactamase (ESBL) production was done by the phenotypic confirmatory test by using ceftazidime discs in the presence and absence of clavulanic acid.(2),(3),(4)
Result: Staphylococcus aureus was the most frequently isolated pathogenic bacteria from post-operative wounds. A majority of the isolates were resistant to ampicillin and amoxicillin. 1.8 % of the Staphylococcus aureus isolates were methicillin resistant Staphylococcus aureus (MRSA). Most of the gram-negative bacteria which were isolated, ie Escherichia coli, Proteus mirabilis, Klebsiella species and Pseudomonas aeruginosa were sensitive to quinolones and aminoglycosides, but were resistant to cephalosporins (40%). ESBL production was noted in 64.2 % of the isolates which were tested. ESBL production was detected in 60% strains of Escherichia coli and in 75 % strains of Klebsiella species. All the extended spectrum beta lactamase (ESBL) producer isolates were found to be sensitive to the beta-lactam and beta lactamase inhibitor combinations.
Conclusion: This study has shown that a majority of the isolates were gram positive bacteria and that there was an increase in the incidence of ESBL producing Escherichia coli and Klebsiella strains. Tests for the detection of ESBL producing bacteria should be carried out routinely and the use of third generation cephalosporins should be restricted. Hence, there is a need for continuous monitoring to determine the susceptibility pattern of the common isolates which are found in the hospital. To emphasize precise empiric therapy, policies on prescription patterns should be reviewed, which will ensure reduced patient stay, morbidity and cost per day in the hospital.