High prevalence of β-lactam and macrolide resistance genes in human oral Capnocytophaga species.

OBJECTIVES

To determine macrolide-lincosamide-streptogramin (MLS) resistance determinants in the Capnocytophaga genus and to describe the prevalence of β-lactam resistance genes in human oral Capnocytophaga species.

METHODS

Forty-eight Capnocytophaga isolates identified by analysis of 16S rRNA sequences were isolated from subgingival samples from 14 haematology patients (HPs), 11 periodontitis patients (PPs) and 17 healthy volunteers (HVs). MICs of β-lactam and MLS antibiotics were obtained for all isolates. blaCfxA, blaCSP-1 (encoding a new class A β-lactamase) and MLS resistance genes [erm(F), erm(B), erm(Q), erm(D), erm(C) and erm(A)] were evaluated using specific PCR and sequencing.

RESULTS

In HVs, which had the lowest prevalence of β-lactamase-producing isolates in comparison with the other groups (16%; P < 0.001), Capnocytophaga ochracea was the prominent species (68%; P < 0.03). In PPs, which had a high prevalence of β-lactamase-positive isolates (82%; P < 0.001), Capnocytophaga sputigena was more frequently identified (64%; P < 0.03). In HPs, 50% of isolates were β-lactamase-positive. The more rarely identified species (15%) Capnocytophaga gingivalis, Capnocytophaga granulosa and Capnocytophaga leadbetteri were isolated only from PPs and/or HPs. All β-lactam-resistant isolates (44%) were PCR-positive for blaCfxA (31%) or blaCSP-1 (12.5%). Interestingly, blaCSP-1 was identified only in a subgroup of the C. sputigena species. Twenty-nine percent of isolates were MLS resistant independently of species identification, β-lactamase production or patient group. The MLS-resistant isolates carried the erm(F) or erm(C) gene (93% and 7%, respectively), previously unknown in the Capnocytophaga genus.

CONCLUSIONS

Our findings illustrate that Capnocytophaga species are important contributors to the β-lactam and MLS resistance gene reservoir in the oral microbiome.