Comparison of a Standardized Antimicrobial Susceptibility Disc Diffusion Method with Komfo Anokye Teaching Hospital’s Locally Adapted Method.

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APRIL, 2010
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The clinical microbiology laboratory of the Komfo Anokye Teaching Hospital employs a locally adapted method for antimicrobial susceptibility testing. This method is a variant of the British Society for Antimicrobial Chemotherapy (BSAC) standardized disc diffusion method. Antimicrobial susceptibility testing of bacteria isolated at the Komfo Anokye Teaching Hospital (KATH) was performed using the BSAC method. A total of 200 bacterial isolates were cultured from nine different types of specimens. The sites of origin were urine 33%, blood 32%, sputum, pus, wound, ear and aspirated specimens 31.5%, urethral smear 1.5% and cerebrospinal fluid 1.0%. Gram-negative bacteria accounted for 183 (91.5%) isolates; the main species were Escherichia coli (34.5%), Klebsiella pneumoniae (18.5%), Pseudomonas aeruginosa (9.0%), Proteus mirabilis (3.5%), Salmonella typhi (7.0%) and coliforms (19.0%). Gram-positive bacteria contributed 17 (8.5%) of isolates with Staphylococcus aureus 6.5% being the most predominant followed by Streptococcus pneumoniae 2.0%. Escherichia coli showed 100% and 92% resistance to ampicillin and cefuroxime respectively with 36% being susceptible to cefotaxime. Amikacin resistance in Gram-negative bacilli was 18.7%. Staphylococcus aureus strains showed 36% resistance to oxacillin. Streptococcus pneumoniae isolates showed 100% resistance to oxacillin and also to ceftriaxone. Comparison of susceptibility results of both methods showed 49.1% and 35.8% agreement in susceptible and resistant results respectively. As much as 29.9%, 2.8% and 5.1% of susceptibility results of the locally adapted method were reported as very major, major and minor errors respectively against the BSAC. The study recommends that the locally adapted method be revised in relation to current standard practices.
A Thesis Submitted To The Department Of Clinical Microbiology In Partial Fulfilment Of The Requiement For The Award of the Master Of Science Degree in Clinical Microbiology,