There were 34.2% isolates that met the MDR criteria in our study. The lowest resistance rate among 158 isolates to non-β-lactam agents was still as high as 26.6% (to amikacin). Therefore, therapeutic options for ESBL-producing K. pneumoniae infections will become increasingly limited. In this survey, the most prominent non-ESBL blaSHV was identified to be SHV-11 (28.5%).

Interestingly, a survey in Korea indicated that the incidence of blaSHV-12 was more predominant in K. pneumoniae strains carrying the chromosomal blaSHV-11 (19.3%) than in strains carrying the blaSHV-1 (2.0%) (Lee et al., 2006). SHV-12 is classified as group 2be and sometimes shows high-level resistance to third-generation cephalosporins and resistance to β-lactamase inhibitors (Nüesch-Inderbinen et al., 1997). It is currently not known why this overabundance of SHV-12 had occurred, but the high prevalence of blaSHV-11 in our study certainly warrants Dabrafenib chemical structure click here further surveillance. Two isolates carrying the novel SHV-142 together with CTX-M-14 were detected. Both isolates showed slight MICs increase to gentamicin and ciprofloxacin to isolates harboring CTX-M-14 alone (data not shown). Five isolates coding blaSHV-108 were detected, and they all showed the MDR phenotype (data not shown). The data indicated the isolates co-harboring SHV-108 showed high MIC values to non-β-lactam

antibiotics. This is the first report of the occurrence of SHV-60, SHV-103, and SHV-108 in China. blaTEM-1 was detected in 91 isolates but one encoding TEM-135, which was sporadically reported in Neisseria gonorrhoeae

strains (Ohnishi et al., 2010). In this study, 6 (3.8%) carbapenem-resistant isolates were detected and five of them were with blaKPC-2. Lower breakpoints of the carbapenems do not completely exclude the possibility of resistant KPC isolate Vildagliptin to be called susceptible (Bulik et al., 2010). This suggests that KPC producers have been underestimated in this study. Nine (5.7%) isolates no blaCTX-M/SHV/TEM ESBL was detected (Table 1). These isolates may have produced another ESBL, which was not determined in this study or might have given positive results for ESBL activity. Among 155 isolates, only a small number of isolates showed clonal relationships (> 70% similarity) by the MLST methods. ST-11 and CC11 were the most predominant, present in 19 (12.3%) and 34 (21.9%) isolates, respectively. As for the predominate ESBL, CTX-M-14-producing K. pneumoniae strains of the main STs 37, 5, 505, 11, 23, 1, 22, and 48 were scattered in six geographical areas, exhibiting a multiclonal distribution. ST340 and ST15 as two major CTX-M-15-producing K. pneumoniae epidemic clones were dispersed in three independent areas. Three SHV-12 clones, ST722, ST340, and ST709 were also dispersed in three areas. These data indicate that the predominant ESBL-producing K. pneumoniae isolates from lower respiratory tract might acquire ESBL genes independently.