Prevalence of antimicrobial resistance genes in Bacteroides spp. and Prevotella spp. Dutch clinical isolates.

OBJECTIVES: The prevalence of resistance genes in two important anaerobic genera, Bacteroides and Prevotella, was assessed by applying PCR specifically directed to genes of interest. METHODS: A total of 101 Bacteroides spp. and 99 Prevotella spp. human clinical isolates were identified using MALDI-TOF MS. The presence of the resistance genes cfxA, cepA, cfiA, tetQ, ermF and nim, was assessed. Prevalence of resistance genes was compared with the phenotypic resistance against amoxicillin, clindamycin, meropenem and metronidazole. RESULTS: Even though the majority of the Bacteroides isolates (95.0%) showed resistance towards amoxicillin, only 52/101 of the isolates harboured one of the resistance genes, accounting for this resistance. Within the genus Prevotella the presence of cfxA (50/99) almost perfectly matched the amoxicillin resistance (48/99). No difference in prevalence of the ermF gene (16/101 and 9/99) and clindamycin resistance (16/101 and 10/99) was observed within Bacteroides and Prevotella, respectively. Two isolates of Prevotella were resistant to metronidazole. One harboured the nim gene. One metronidazole-susceptible isolate of Bacteroides harboured a nim gene. Within the Bacteroides and Prevotella genera, 6/101 strains and 5/99 isolates harboured three different resistance genes, respectively, among them tetQ. TetQ is often located on a conjugative transposon, increasing the chance of horizontal gene transfer between isolates. CONCLUSIONS: An unknown mechanism in Bacteroides non-fragilis isolates causes resistance to ß-lactam antibiotics. The fact that the prevalence of the tetQ gene among Prevotella is increasing and the existence of isolates harbouring three resistance genes are worrisome developments.

Spread of a methicillin-resistant Staphylococcus aureus ST80 strain in the community of the northern Netherlands.

Infections caused by community-acquired methicillin-resistant Staphylococcus aureus (MRSA) are emerging as a major public health problem. In this study, we describe the distribution of 54 Panton-Valentine leucocidin (PVL)-carrying MRSA isolates in the northern Netherlands between 1998 and 2005, of which 43 (80%) consisted of the European PVL-positive strain multi locus sequence type 80 with staphylococcal cassette chromosome mec type IVc (ST80). Individual cases and small clusters of ST80 predominated in the community (74%), but ST80 was also found in nursing homes (16%) and hospitals (9%). Long-term carriership (months to years) and reinfection of patients with ST80 has probably led to the strain spreading in the community and subsequently to further migration to health care environments.