Tet(M) Mediates Tetracycline Resistance in Methicillin-Resistant Staphylococcus aureus (MRSA) Clinical Isolates from the Private Hospital Sector in KwaZulu-Natal (KZN), South Africa

To elucidate the molecular determinants of tetracycline resistance in clinical methicillin-resistant Staphylococcus aureus (MRSA) isolates from the private health sector in KwaZulu-Natal province (KZN), South Africa (SA). Seventy-five clinical MRSA isolates were collected from the private hospital sector in KZN, SA over a one-year period. Susceptibility to antibiotics (tetracycline, doxycycline, minocycline and tigecycline) were determined and tetracycline resistant strains were screened using polymerase chain reaction (PCR) for the presence of four putative tetracycline resistance determinants (tet(K), tet(L), tet(M) and tet(O)). Efflux inhibitors were used to assess the possibility of efflux-mediated resistance.All isolates were mecA gene positive and susceptible to doxycycline, minocycline and tigecycline. Of note, 47 (62.67%) isolates were resistant to tetracycline. Doxycycline exhibited the largest number of intermediate resistance 20 (26.67%) in all the isolates. The tet(M)gene was found in all 47tetracycline-resistant isolates. No tet(L), tet(K) and tet(O) were detected. Efflux inhibitors did not have any significant effect on the sensitivity of tetracycline-resistant isolates suggesting that efflux played a minor role in tetracycline resistance. In conclusion; Tet(M) mainly mediates tetracycline resistance in MRSA in the private health sector in KZN, SA. This report on the prevalence and molecular determinants of tetracycline resistance is the first study on clinical MRSA isolates from the private health sector in SA