Detection of tetQ and ermF antibiotic resistance genes in Prevotella and Porphyromonas isolates from clinical specimens and resident microbiota of humans

Gram-negative anaerobes belonging to the genera Fusobacterium, Prevotella a nd Porphyromonas were investigated for the presence of tetQ and ermF, which have been shown to be spread by conjugal elements. One hundred isolates fr om either sites of infection or various body sites in healthy subjects were studied. PCR was used to detect tetQ, and DNA-DNA hybridization studies on EcoRI chromosomal digests were undertaken to detect the presence of tetQ a nd ermF. Antibiotic sensitivity assays were performed on selected isolates to detect tetracycline, erythromycin and penicillin resistance. Twenty Fuso bacterium isolates lacked tetQ, and were tetracycline sensitive. Twenty per cent of Prevotella spp, isolates both from clinical specimens and from hea lthy subjects were found to possess tetQ. Of 20 Porphyromonas isolates test ed, one (Porphyromonas levii) from a case of bacterial vaginosis was shown to possess tetQ in the chromosome. The presence of tetQ was always associat ed with tetracycline resistance. Four isolates of Prevotella melaninogenica and one isolate of Prevotella were ermF-positive, although expression of e rythromycin resistance was not consistently associated with detection of th is gene. Antibiotic resistance phenotypes of Prevotella isolates were shown to be related to specific chromosomal restriction patterns by hybridizatio n studies: tetracycline resistance and tetracycline/erythromycin resistance are conferred by Bacteroides tetracycline-resistant ERL elements, whereas the tetracycline/peniciilin resistance phenotype could be due to spread of elements identified in Prevotella only. Tetracycline/erythromycin-resistant and tetvacycline/erythromycin/penicillin-resistant P. melaninogenica isola tes were found in this study. It appeared that the presence of tetQ and erm F in Bacteroides and Prevotella contributed to the persistence of antibioti c resistance isolates within the host and to potential spread to other orga nisms through conjugal elements.