Objective: The dearth of information on antibiotic susceptibility pattern of anaerobic Gram negative bacilli from Nigeria informed the retrospective assessment of resistance pattern amongst predominant species in the genera Bacteroides and Prevotella to three classes of antibiotics frequently prescribed for mixed aerobic-anaerobic infections.
Methods: We reviewed our data on antibiotic resistance in frequently isolated species of Bacteroides and Prevotella from series of studies spanning 1992 to 2011 from four specialist hospitals in Lagos, Nigeria and evaluated the correlation between presence of resistance genes and the observed resistance trends.
Results: Bacteroides fragilis was consistently the most resistant species with progressively increasing MIC values throughout the study period. B. fragilis resistance increased for amoxicillin-clavulanic acid from 18.2% in 1992-1996 to 31.4% in 2006-2011 and from 27.3% in 1992-1996 to 34.3% in 2006-2011 for cefoxitin. In contrast, decrease susceptibility was obtained against clindamycin (54.5% in 1992-1996 to 22.9% in 2006-2011). Similarly, 22.7% of B. fragilis strains have the cepA and/or cfxA gene in 1992-1996 compared to 32.1% in 2006-2011. While not all isolates with cepA and/or cfxA genes were resistant to the b-lactams, all isolates carrying the ermF or nim genes were resistant to the lincosamide (clindamycin) or nitroimidazole (metronidazole) respectively.
Conclusion: The presence of antibiotics resistance genes correlated with the level of resistance making it possible to track antibiotic resistance by demonstrating the presence of resistance markers.
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