Molecular serotyping and genotyping of penicillin non-susceptible pneumococci: the introduction of new sequence types (STs), tehran, Iran

Abstract The emergence of penicillin-nonsusceptible Streptococcus pneumoniae (PNSP) isolates can pose significant challenges facing today's health care system. Resistant clonal isolates are disseminated in different regions and countries, and this study was focused on the description of the epidemiological spread of before-mentioned strains. Clinical samples were collected from patients admitted to hospitals affiliated to Tehran University of Medical Sciences (TUMS), Iran. To investigate the molecular characteristics of PNSP isolates, they were subjected to molecular typing using multi-locus sequence typing (MLST). Serotype distributions of S. pneumoniae isolates were also evaluated by multiplex PCR assay. The most prevalent serotypes in the PNSP isolates were 23F, 19F, 14, 3, and 9V. Two isolates were considered as a non-vaccine serotype (NVT). The MLST analysis showed that PNSP isolates belonged to five different clonal complexes (CC180, CC217, CC81, CC63, and CC320) and forty-two percent (5/12) of the STs were novel (12936, 12937, 12938, 12939, and 12940). This study indicates the high level of heterogeneity is present among PNSP isolates. Unexpected high genetic diversity in small populations is indicating consecutive diversification of resistant strains.