Substrate profile variation and drug resistance patterns of a — lactamase producing Shigella species isolated from diarrhoeal patients in Lagos, Nigeria

Abstract

The number and trend of antibiotic resistance by Shigella species recovered from food and diarrhoeal stools arc on the increase in Nigeria and has resulted in a high frequency of hospitalisation. Increased cost of disease management, and higher mortality in children. This study exposes 51 a - lactamase producing Shigella isolates from Lagos to some newly introduced drugs in the country. The drugs include 8. - lactam - a -lactamase inhibitor antibiotics, a - lactam substrate hydrolysis and inhibitory effects of clavulanate were also investigated in-vitro. Results obtained revealed that all the isolates showed high level resistance to tetracycline, ampicillin, streptomycin, co-trimoxazole and amoxicillin with an MIC range of 128 - 1024 pg/ml. The isolates were susceptible to piperacillin, tobramycin, aztreonam and ofloxacin (0.03 - 8|.ig/ ml). 18.2 -40.9 % o f S . flexneriand S. dysenteriaeshowed low level resistance to cefuroxime and cefotaxime (MIC = 4 - 16fig/ ml). Among the a-lactam - a - lactamase inhibitors tested, only piperacillin-tazobactam showed 100% resistance. Hydrolysis of a - lactam substrate was found to be species dependent in decreasing order of S. flexneri, S. dysenteriae, S. sonnei and S boydii. An IC50 range of 0.8 -2. 4 mM was also observed in these isolates. Our dat a indicate that the incidence of multidrug resistance is high among a - lactamase producing Shigella isolates in Lagos, Nigeria. While the third generation cephalosporins should be used with cautions, some of the newly introduced drugs have the prospects of being used in the future control and management of shigellosis in the country.