Emergence of optochin resistance among Streptococcus pneumoniae in Portugal. Microb. Drug Resist

and the PORTUGUESE SURVEILLANCE GROUP FOR THE STUDY OF RESPIRATORY PATHOGENS In most clinical microbiology laboratories optochin susceptibility is used in the screening and identification of Streptococcus pneumoniae. We report the characterization of 32 optochin-resistant S. pneumoniae strains from 10 laboratories that constituted 3.2 % of all isolates recovered in 2005 in 30 laboratories in Portugal. Re-sistant isolates consisted of bile-soluble optochin-susceptible and optochin-resistant subpopulations with iden-tical antimicrobial susceptibility patterns, capsular types and pulsed-field gel electrophoresis (PFGE) profiles. The most frequent serotypes—1, 19A, 11A, 3, 8, and 15A—were all common serotypes present in infection and colonization isolates in the country. The PFGE profiles of the 32 isolates corresponded to those of previ-ously identified clones and confirmed that the emergence of these strains could not be attributed to clonal ex-pansion. Clinical laboratories must be aware that optochin-resistant pneumococci are presently circulating in the community. Because accurate identification of S. pneumoniae is essential for correct diagnosis and ade-quate therapy of patients, we recommend that at least the bile solubility test should be routinely performed in cases of suspected pneumococcal etiology, even if the isolates are optochin-resistant. 23