Characteristics of Haemophilus influenzae type b responsible for meningitis in Poland from 1997 to 2004.

Two hundred forty-five H. influenzae isolates responsible for meningitis in Poland from 1997 to 2004 were studied. Among these, 233 (95.1%) belonged to serotype b (Hib), 2 belonged to serotype f, and 10 were noncapsulated. The relatedness of all isolates was evaluated by pulsed-field gel electrophoresis (PFGE), and selected representatives were evaluated by multilocus sequence typing. Resistance to ampicillin was identified in 34 (14.6%) of the Hib isolates and was associated with the production of beta-lactamase only. Except for four isolates nonsusceptible to chloramphenicol, all isolates were susceptible to cefotaxime, ciprofloxacin, and rifampin. The PFGE analysis divided the Hib isolates into five PFGE types; however, all of them were possibly related. The most common PFGE type, with 25 subtypes, was characteristic for 97.4% of the isolates. The most prevalent PFGE subtype found in our study was also the most common among the Hib isolates responsible for invasive disease in Italy and the Czech Republic and was found among isolates causing lower respiratory tract infections in Poland. The most prevalent sequence types (STs) in the studied group were ST6 and ST92. Four new STs were found: ST188, ST189, ST190, and ST268. Results of this study support the evidence that the genetic structure of encapsulated H. influenzae is clonal. The continuing high number of meningitis cases due to Hib in Poland underlines the need for mass vaccination against Hib in Poland.