Genotype and drug resistance analysis of extended-spectrum beta-lactamases-producing Shigella in pediatric patients
Objective To investigate the genotype and drug resistance of extended-spectrum beta-lac-tamases(ESBLs) -producing Shigella in pediatric patients.Methods A total of 59 strains of Shigella were isolated from stool specimens of hospitalized children with shigellosis in Beijing Children's Hospital from January 2004 to December 2008.Phenotypic confirmatory test,which is based on Clinical and Laboratory Standards Institute(CLSI),was used to detect the ESBLs-producing strains.Agar dilution method was used to determine the minimal inhibitory concentration (MIC).PCR amplification was performed for ESBLs producers to determine the genotype.PCR product was sequenced and then analyzed to confirm the subtype of ESBLs.Results Of the 59 isolates,21 (35.6%) strains were identified as ESBLs producers.The 21 strains of ESBLs-producing Shigella all carried the genes of CTX-M as shown by PCR,and CTX-M-1,CTX-M-9 accounted for 6,15,respectively.Among the 21 CTX-M producers,there were 4 strains accompanied by TEM-type and 6 strains accompanied by OXA-type.Nucleotide sequence analysis showed that there were CTX-M-3 (n = 1),CTX-M-15 (n = 2),CTX-M-57(n =3) of the 6 CTX-M-1-producing isolates.The subtypes of CTX-M-9,TEM,OXA were all CTX-M-14,TEM-1,OXA-1,respectively.The sensitive drugs to ESBLs producers were imipenem,meropenem,piperacillin/tazobactam,cefoperazone/sulbactam and cefoxitin,with resistance rate all less than 15%.The resistance to ceftazidime was remarkably variable among different CTX-M producers.Conclusion The prevalence of ESBLsproducing Shigella is in a high level in pediatric patients in this area.The genotypes of ESBLs are all CTX-M.Most of them are CTX-M-14,but some are CTX-M-3,CTX-M-15 and CTX-M-57.Most ESBLs-producing strains are multidrug resistant.Carbopenems should be the first choice for ESBLs producers. 
 
Key words: 
Child; Shigella; β-lactamases; Genotype; Drug resistance