The Sequence of pbp2b from Penicillin-Resistant Streptococcus pneumoniae in Thailand
Chanwit Tribuddharat MD, PhD*, Pitimon Polwichai MSc**, Preecha Champreeda BSc, MBA***, Somporn Srifuengfung PhD*
Affiliation : * Department of Microbiology, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand ** National Institute of Health, Department of Medical Sciences, Ministry of Public Health, Nonthaburi, Thailand *** GlaxoSmithKline (Thailand) Ltd, Bangkok, Thailand
Objective : Penicillin resistance in Streptococcus pneumoniae isolates results from altered penicillin-binding proteins (PBPs),
especially PBP2, which has a reduced affinity to penicillin. This study evaluated drug resistance and the gene sequence of the
conserved motif pbp2b of penicillin-resistant isolates in Thailand.
Material and Method: Penicillin-resistant pneumococci with minimum inhibitory concentrations (MIC) for penicillin > 4 μg/
ml and penicillin-susceptible strains were identified from clinical specimens. The pbp2b genes were amplified by polymerase
chain reaction (PCR), and the purified PCR product was cloned into E. coli. The recombinant plasmid clones containing
pbp2b were sequenced and evaluated for mutations corresponding to penicillin and cefotaxime resistance.
Results : Penicillin-susceptible S. pneumoniae isolates were susceptible to 12 other antibiotics tested (range 95-100%) while
penicillin-nonsusceptible isolates were resistant to most antibiotics except amoxicillin/clavulanate and levofloxacin. Sequence
analysis of pbp2b showed a substitution of A for T451 next to the region of the SSN triad in all six resistant isolates tested and
mutations clustered around the KTG triad in two isolates. Using the ClustalW alignment program, Thai isolates differed from
those of European countries, but were more similar to those from Japan than Korea.
Conclusion : Penicillin or cefotaxime resistance in S. pneumoniae in Thailand was due to affinity reduction of PBP2b, similar
to changes found in other Asian isolates.
Keywords : Streptococcus pneumoniae, Pneumococci, Genotype, pbp2b
