Characterization of highly antimicrobial-resistant clinical pneumococcal isolates recovered in a Chinese hospital during 2009–2010

Ninety-one consecutive pneumococcal isolates (primarily from sputum), recovered in Chongqing Southwest Hospital during a 12 month period in 2009-2010 from individuals of all ages with suspected cases of pneumococcal disease, were subjected to PCR-serotyping, Quellung reaction serotyping, antimicrobial-susceptibility testing and multilocus sequence typing (MLST). Although 20 different serotypes were observed, most isolates (69, 75.8 %) were of serotypes included in the pneumococcal 13-valent conjugate vaccine (PCV13), including 33 of the 46 (71.7 %) isolates recovered from individuals less than 5 years of age. The prevalent serotypes were 19F (34 %), 19A (9.9 %), 6B (9.9 %), 23F (7.7 %), 14 (6.6 %) and 6A (4.4 %). PCR-determined serotypes were in agreement with Quellung testing, with the exception of two serotype 33C isolates. Most or all isolates within each PCV13 serotype were represented by one genotype, with the globally disseminated MLST sequence types (STs) ST271, ST320, ST90 and ST81 each accounting for the highly resistant isolates within serotypes 19F, 19A, 6B and 23F, respectively. Sixty-six (72.5 %) isolates were resistant to combinations of β-lactam antibiotics (BLAs). A total of 63 of these 66 (95.5 %) BLA-resistant isolates were of serotypes included in PCV13; however, 3 serogroup 15 isolates were also BLA-resistant. Most isolates (88/91 = 96.7 %) were resistant to erythromycin and clindamycin. The majority of isolates were also resistant to tetracycline (76, 84 %) and to cotrimoxazole (67, 74 %). This work revealed that the majority of antimicrobial-resistant isolates (50/91 = 54.9 %) recovered in this Chinese hospital were represented by four global clones. Serotypes for these as well as more obscure strains were readily determined by using PCR.