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  Table of Contents  
Year : 2014  |  Volume : 32  |  Issue : 1  |  Page : 95-96

Prevalence and characterisation of extended spectrum β-lactamases genes in Shigella isolates, in Wenzhou, Southern China

1 Department of Microbiology, Marmara University medical School, Istanbul, Turkey; School of Medical Lab Science, Wenzhou Medical College, Wenzhou, Zhejiang Province, China
2 Department of Clinical Laboratory, The First Affiliated Hospital of Wenzhou Medical College, Wenzhou, Zhejiang Province, China

Date of Submission23-Mar-2013
Date of Acceptance12-Sep-2013
Date of Web Publication4-Jan-2014

Correspondence Address:
T Zhou
Department of Clinical Laboratory, The First Affiliated Hospital of Wenzhou Medical College, Wenzhou, Zhejiang Province, China

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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0255-0857.124348

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How to cite this article:
Cao J, Zhang X, Zhou T, Lu Y, Hou J, Guo M, Wu Q. Prevalence and characterisation of extended spectrum β-lactamases genes in Shigella isolates, in Wenzhou, Southern China. Indian J Med Microbiol 2014;32:95-6

How to cite this URL:
Cao J, Zhang X, Zhou T, Lu Y, Hou J, Guo M, Wu Q. Prevalence and characterisation of extended spectrum β-lactamases genes in Shigella isolates, in Wenzhou, Southern China. Indian J Med Microbiol [serial online] 2014 [cited 2020 Oct 20];32:95-6. Available from:

Dear Editor,

Shigellosis remains a public health concern throughout the world. [1] However, the emergence of multiple-drug-resistant (MDR) strains of Shigella spp. has made the treatment for shigellosis more difficult. [2] Third-generation cephalosporins so far have been commonly used to treat the infections caused by MDR isolates. However, since the first report of SHV-11-type β-lactamases in Shigella dysenteriae from India in 1999, [3] Shigellae species expressing extended-spectrum β-lactamases (ESBLs) have emerged globally, and this has further narrowed the choice of effective antimicrobials. [4] The objectives of the present study were to determine the antibiotic susceptibility patterns, evaluate the distribution of the serotypes of Shigella spp. and investigate the drug-resistant genes of ESBLs in Shigella in Wenzhou, southern China.

A total of 62 non-duplicated Shigella strains (42 Shigella flexneri, 16 Shigella sonnei, 3 Shigella dysenteriae and 1 Shigella boydii) were isolated from stool samples of patients with diarrhoea in six hospitals of Wenzhou from June 2006 to June 2009. Serotypes for Shigella isolates were determined by serum agglutination test by slide agglutination. Eight serotypes were identified, that is S. sonnei (n = 16, 25.8%), S. flexneri serotype f4c (n = 15, 24.2%), S. flexneri serotype f2a (n = 8, 12.9%), S. flexneri serotype f1a/f2b (n = 5, 8.1%), S. flexneri serotype f4a (n = 4, 6.5%), S. flexneri serotype f4b (n = 3, 4.8%) and S. flexneri serotype f1b (n = 2, 3.2%). The predominant serotype was S. flexneri serotype f4. In developing countries, S. flexneri serotype f4 is not a commonly identified serotype, the predominant serotype of S. flexneri is 2a, followed by 1b, 3a, 4a and 6. However, our current study indicates that S. flexneri serotype f4 is common in Zhejiang, China.

Antimicrobial susceptible testing was performed by agar dilution method according to Clinical and Laboratory Standards Institute (CLSI) guidelines (CLSI 2010). Production of ESBLs was determined by double disc synergy and inhibitor-potentiated disc diffusion tests. ESBLs genes were detected by PCR using primers described previously. [5] Both S. flexneri and S. sonnei isolates have high resistance against ampicillin and nalidixic acid and high sensitivity to piperacillin/tazobactam and cefepime. More than 37% of Shigella isolates showed resistance to ceftriaxone or cefotaxime. However, susceptibility to the different antimicrobials appeared to differ depending on the species. The prevalence of ceftriaxone (or cefotaxime) and gentamicin resistance of S. sonnei isolates (12/16, 75%; 12/16, 75%) was significantly higher than that (9/42, 21.4%; 4/42, 9.5%) of S. flexneri isolates (P < 0.005, χ2 = 14.4; P < 0.005, χ2 = 14.92). Twenty-two isolates were positive in phenotypic confirmatory tests. ESBLs genes were detected in 22 of 62 clinical Shigella isolates, which involved the blaCTX-M-14 gene from 12 S. sonnei, 7 S. flexneri and 2 S. dysenteriae, the blaCTX-M-15 gene from 1 S. dysenteriae and 2 S. flexneri, the blaCTX-M-65 gene from 1 S. sonnei and blaSHV-12 gene from 1 S. dysenteriae [Table 1]. Obviously, blaCTX-M-14 was the major ESBLs gene. Conjugation experiments were performed using rifampin-resistant  Escherichia More Details coli C600 as the recipient strain. ESBLs genes were successfully transferred from 15 of 22 ESBL-producing isolates to E. coli C600. The 15 ESBL-producing transconjugants showed 128- to 1024-fold increases in the MIC ceftriaxone and 256- to 1064-fold increases in the MIC cefotaxime relative to those of the recipient. These data provide evidence that ESBLs can be disseminated through horizontal gene transfer to other Shigella pathogens. Pulsed-field gel electrophoresis (PFGE) typing was performed for all the isolates as described previously, [5] and a high genetic homogeneity was observed among nine ESBL-producing S. sonnei isolates. Therefore, more active surveillance is clearly needed to minimise the spread of ESBL-producing Shigella isolates. These data further emphasised the necessity of strict antimicrobial application control in developing nations.

 ~ Acknowledgment Top

We thank Changgui Sun of the 117 Hospital of People's Liberation Army and Yunsong Yu of the First Affiliated Hospital of Zhejiang University for the gifts of Klebsiella pneumoniae Scientific Name Search  ATCC 700603, Escherichia coli EC600 and  Salmonella More Details enterica serotype Braenderup H9812. This study was financially supported by National Natural Science Foundation of China (No. 81171614).

 ~ References Top

1.Kotloff KL, Winickoff JP, Ivanoff B, Clemens JD, Swerdlow DL, Sansonetti PJ, et al. Global burden of Shigella infections: Implications for vaccine development and implementation of control strategies. Bull World Health Organ 1999;77:651-66.  Back to cited text no. 1
2.Niyogi SK. Increasing antimicrobial resistance-an emerging problem in the treatment of shigellosis. Clin Microbiol Infect 2007;13:1141-3.  Back to cited text no. 2
3.Ahamed J, Kundu M. Molecular characterization of the SHV-11 β-lactamase of Shigella dysenteriae. Antimicrob Agents Chemother 1999;43:2081-3.  Back to cited text no. 3
4.Nguyen NT, Ha V, Tran NV, Stabler R, Pham DT, Le TM, et al. The sudden dominance of blaCTX-M harbouring plasmids in Shigella spp. Circulating in southern Vietnam. PLoS Negl Trop Dis 2010;4:e702.  Back to cited text no. 4
5.Zhang R, Zhou HW, Cai JC, Zhang J, Chen GX, Nasu M, et al. Serotypes and extended-spectrum beta-lactamase types of clinical isolates of Shigella spp. from the Zhejiang province of China. Diagn Microbiol Infect Dis 2011;69:98-104.  Back to cited text no. 5


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