Comparison of disk susceptibility test of gram-negative rods with MIC for cefoperazone- sulbactam compination

ABSTRACT

Multi drug resistance [MDR] Acinetobacter to almost all antibiotics has now become a major problem in most hospitals world wide. Cefoperazone /sulbactam and Polymyxin are among the only antibiotics still sensitive against MDR Acinetobacter species. Since Clinical and Laboratory Standards Institute [CLSI] and British Society of Antimicrobial Chemotherapy [BSAC] working party have not included these antibiotics, most clinical laboratories are not performing in-vitro susceptibility against them. We performed a comparative study to find out the sensitivity and specificity of disk diffusion [DD] for in vitro susceptibility test of cefoperazone /subactam with MIC against isolates of Acinetobacter. In-vitro susceptibilities of a total of 42 isolates of Acinetobacter species were performed by MIC [Estrip method] and DD methods. Sensitivity and specificity of the DD was calculated with MIC as standard. Results were analyzed on SPSS version 13.0 and expressed as scattergram. A total of 42 Acinetobacter species were isolated. All were resistant to Cefoperazone alone when checked by DD method. Twenty two were sensitive to Cefoperazone/sulbactam by MIC [< 32/16 Mu g/ml] and 20 were resistant to Cefoperazone/sulbactam [> 32/16 Mu g/ml]. 19 [86%] of sensitive isolates were also sensitive by DD, 18 [86%] of resistant isolates were also resistant by DD. Sensitivity and Specificity of DD were 86% each. Correlation was significant at the 0.01 level [2-tailed]. Among 6/42 discrepancies, 5 were minor and 1 was major. DD method for reporting antimicrobial sensitivity of Acinetobacter species against Cefoperazone/Sulbactam is consistent with MIC with a sensitivity and specificity of 86% each