Isolation, in vitro antimicrobial susceptibility and penicillin tolerance of Arcanobacterium haemolyticum in a Turkish university hospital.

Arcanobacterium haemolyticum (Ah) was isolated from 5 (0.3%) out of 1531 throat cultures of patients with presumed pharyngotonsillitis. The age of the patients who had a positive culture for Ah varied between 6 and 22. The isolation rate of beta-haemolytic streptococci (BHS) was 7.4%, 72.6% of which belonged to Group A, followed by groups G, C and B. None of the throat samples yielded simultaneous growth of Ah and BHS. Antimicrobial susceptibility of Ah isolates to phenoxymethylpenicillin, cephalexin, cefotaxime, vancomycin, erythromycin, azithromycin, doxycycline, ciprofloxacin, and trimethoprim-sulfamethoxazole was tested by the agar dilution method. The isolates were found to be susceptible to all antimicrobials tested except trimethoprim-sulfamethoxazole. Penicillin tolerance could be detected in none of the Ah strains, including the reference strain Ah ATCC 9345. We conclude that Ah should be kept in mind as a potential pathogen causing pharyngitis in adolescents and young adults.