Antibiotic Resistance in Bacteroides and Prevotella to β-Lactams, Lincosamide and Nitroimidazole: A 20 Year Survey in Lagos, Nigeria

Abstract

The propensity to develop resistance to antibiotics has accounted for the predominance of Bacteroides and Prevotella in infections due to anaerobic bacteria. The observed differences in resistance pattern across geographical boundaries underscored the timeliness for this study to review data on antibiotic susceptibility and resistance markers amongst Bacteroides and Prevotella to β-lactams, lincosamide and nitroimidazole from selected hospitals in Lagos, Nigeria from 1992-2011. Bacteroides, mostly B. fragilis were the sole anaerobic gram negative bacilli in peritonitis following lower abdominal surgery and bloodstream infections, while Prevotella bivia and P. melaninogenica were more frequent in periodontal abscess, pelvic inflammatory disease and chronic suppurative otitis media. The MIC range and MIC90 of the anaerobes for the antibiotics does not indicate changes in group resistance to antibiotics though isolated cases were recorded. While clear cut patterns were not established for other species, 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 β-lactams, all isolates carrying the ermF or nim genes were resistant to the lincosamide (clindamycin) or nitroimidazole (metronidazole) respectively. The presence of antibiotics resistance genes can be used in tracking resistance amongst species of Bacteroides and Prevotella. With emerging new technologies, gene screening may prove more effective and reliable for therapeutic decisions for anaerobic bacterial infections especially since the genes can be screened from the infective exudates. This will eliminate the need for culture and antibiotic susceptibility testing for this group of fastidious microorganisms.