Biotyping, capsular typing, and antibiotic resistance pattern of Haemophilus influenzae strains in Iran

The aim of this study was to determine the capsular types of Haemophilus influenzae isolated from clinical specimens by slide agglutination serotyping (SAST) and PCR capsule typing methods. All the isolates were biotyped and their antibiotic resistance patterns also determined. Thirteen isolates of serotype b, 2 of serotype e, 4 of serotype f, and 19 nontypeable (NT) isolates were identified by SAST method in 38 H. influenzae culture-positive samples. Capsule typing by PCR increased the proportion of all invasive cases from 34.2% (by SAST) to 60.5%, and 6 culture-negative samples were identified as invasive H. influenzae (Hib) by this method. The discrepancy rate between SAST and PCR results were 41%. Biotypes I, II, and III were the prevalent biotypes whereas biotypes VI and VII were not found. The majority of capsule type b belonged to biotype II. The isolates were resistant to cotrimoxazole (47.1%) and ampicillin (43.6%). Multidrug resistance was observed in 7 of the isolates.