Macrolide, lincosamide and tetracycline susceptibility and emm characterisation of invasive Streptococcus pyogenes isolates in Israel

Group A β-haemolytic streptococcus (GAS) causes a variety of infections, including life-threatening illnesses. Although the species is uniformly penicillin susceptible, resistance to other antibiotics is becoming more common. We studied the prevalence of resistance and associated factors in a nationwide, prospective, population-based study of invasive infections in Israel. Isolates were collected in collaboration with 24 hospitals in Israel during 1996–1999. Minimal inhibitory concentrations (MICs) of erythromycin (ERY), clindamycin (CLI) and tetracycline (TET) were determined as well as ERY and TET resistance phenotypes and genotypes. Five hundred isolates were examined: 136 (27.2%) were not susceptible to TET, 10 (2.0%) to ERY and 5 (1%) to CLI. ERY resistance was associated with emm types 12 and 83 (P < 0.001 for both). MICs of TET had a bimodal distribution distinguishing sensitive and resistant populations. Non-susceptibility to TET was mainly due to the presence of tet(M) and was associated with T types 3, 3/13/B3624 and 9 and emm types 9, 33, 64, 73, 74, 76, 77 and 83. TET susceptibility was associated with T types 1, 2 and 11, emm types 1–4, 11, 12, 22, 26 and 75 and the presence of speA and speC. In Israel, resistance of invasive GAS isolates to ERY remains low and is associated with specific T and emm types, as is TET resistance. TET resistance is less frequent than previously reported in Israel and is associated with a lower prevalence of speA and speC.