Streptococcus pyogenes is sensitive to penicillin Magnus Rasmussen, Lund University 20 March 2014 We read with interest this report describing the bacterial isolates and their resistance in a laboratory in Gabon. We were very surprised that six isolates of Streptococcus pyogenes were reported as non-susceptible to penicillin. The universal susceptibility of S. pyogenes to penicillin is a dogma in bacteriology and infection medicine. Development of resistance to penicillin by this bacterium would have substantial negative consequences for the treatment of many types of streptococcal infections. When an unexpected finding, such as non-susceptibility of S. pyogenes to penicillin, is reported, firm evidence for that claim need to be presented. In the report by Alabi and co-workers it is not clear how species determination of the non-susceptible isolates was performed and therefore it cannot be ruled out that the bacteria belong to another species where non-susceptibility can be expected. Most importantly, however, no confirmatory analysis was performed to support the unexpected results. Not even the minimal inhibitory concentration (MIC) was determined as the authors state that methods for this were not available. We have contacted the authors to obtain the isolates for confirmatory analyses but we were informed that the isolates had not been preserved. We regard the results presented insufficient to conclude that S. pyogenes isolates with penicillin non-susceptibility exist in Gabon as the results presented by Alabi and co-workers might be explained by methodological errors. As outlined in documents by Eucast, a laboratory that encounters S. pyogenes isolates with resistance to penicillin should send such isolates to a reference laboratory for confirmation . Until otherwise proven, S. pyogenes should be regarded as universally sensitive to penicillin. Magnus Rasmussen MD, PhD and Fredrik Kahn MD, PhD Division for Infection Medicine Lund University Sweden Reference 1. EUCAST clinical breakpoints [http://www.eucast.org/clinical_breakpoints/]. Competing interests We have no competing interests to declare.