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Deletion of pic results in decreased virulence for a clinical isolate of Shigella flexneri 2a from China.

ABSTRACT: BACKGROUND: Shigella is a major pathogen responsible for bacillary dysentery, a severe form of shigellosis. Severity of the disease depends on the virulence of the infecting strain. Shigella pathogenicity is a multi-gene phenomenon, involving the participation of genes on an unstable large virulence plasmid and chromosomal pathogenicity islands. RESULTS: A multiplex PCR (mPCR) assay was developed to detect S. flexneri 2a from rural regions of Zhengding (Hebei Province, China). We isolated and tested 86 strains using our mPCR assay, which targeted the ipaH, ial and set1B genes. A clinical strain of S. flexneri 2a 51 (SF51) containing ipaH and ial, but lacking set1B was found. The virulence of this strain was found to be markedly decreased. Further testing showed that the SF51 strain lacked pic. To investigate the role of pic in S. flexneri 2a infections, a pic knockout mutant (SF301-? pic) and two complementation strains, SF301-? pic/pPic and SF51/pPic, were created. Differences in virulence for SF51, SF301-? pic, SF301-? pic/pPic, SF51/pPic and S. flexneri 2a 301 (SF301) were compared. Compared with SF301, both SF51 and SF301-? pic exhibited lower levels of Hela cell invasion and resulted in reduced keratoconjunctivitis, with low levels of tissue damage seen in murine eye sections. The virulence of SF301-? pic and SF51 was partially recovered in vitro and in vivo through the addition of a complementary pic gene. CONCLUSIONS: The pic gene appears to be involved in an increase in pathogenicity of S. flexneri 2a. This gene assists with bacterial invasion into host cells and alters inflammatory reactions.

SUBMITTER: Zhang J

PROVIDER: S-EPMC3626585 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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Deletion of pic results in decreased virulence for a clinical isolate of Shigella flexneri 2a from China.

Zhang Junqi J Qian Lisheng L Wu Yang Y Cai Xia X Li Xueping X Cheng Xunjia X Qu Di D

BMC microbiology 20130208

<h4>Background</h4>Shigella is a major pathogen responsible for bacillary dysentery, a severe form of shigellosis. Severity of the disease depends on the virulence of the infecting strain. Shigella pathogenicity is a multi-gene phenomenon, involving the participation of genes on an unstable large virulence plasmid and chromosomal pathogenicity islands.<h4>Results</h4>A multiplex PCR (mPCR) assay was developed to detect S. flexneri 2a from rural regions of Zhengding (Hebei Province, China). We is ...[more]

PMID: 23391153

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Project description:Shigella flexneri is an intracellular human pathogen that invades colonic cells and causes bloody diarrhea. S. flexneri evolved from commensal Escherichia coli, and genome comparisons reveal that S. flexneri has lost approximately 20% of its genes through the process of pathoadaptation, including a disproportionate number of genes associated with the turnover of the nucleotide-based second messenger cyclic di-GMP (c-di-GMP); however, the remaining c-di-GMP turnover enzymes are highly conserved. c-di-GMP regulates many behavioral changes in other bacteria in response to changing environmental conditions, including biofilm formation, but this signaling system has not been examined in S. flexneri. In this study, we expressed VCA0956, a constitutively active c-di-GMP synthesizing diguanylate cyclase (DGC) from Vibrio cholerae, in S. flexneri to determine if virulence phenotypes were regulated by c-di-GMP. We found that expressing VCA0956 in S. flexneri increased c-di-GMP levels, and this corresponds with increased biofilm formation and reduced acid resistance, host cell invasion, and plaque size. We examined the impact of VCA0956 expression on the S. flexneri transcriptome and found that genes related to acid resistance were repressed, and this corresponded with decreased survival to acid shock. We also found that individual S. flexneri DGC mutants exhibit reduced biofilm formation and reduced host cell invasion and plaque size, as well as increased resistance to acid shock. This study highlights the importance of c-di-GMP signaling in regulating S. flexneri virulence phenotypes. IMPORTANCE The intracellular human pathogen Shigella causes dysentery, resulting in as many as one million deaths per year. Currently, there is no approved vaccine for the prevention of shigellosis, and the incidence of antimicrobial resistance among Shigella species is on the rise. Here, we explored how the widely conserved c-di-GMP bacterial signaling system alters Shigella behaviors associated with pathogenesis. We found that expressing or removing enzymes associated with c-di-GMP synthesis results in changes in Shigella's ability to form biofilms, invade host cells, form lesions in host cell monolayers, and resist acid stress.

Dataset Information

Deletion of pic results in decreased virulence for a clinical isolate of Shigella flexneri 2a from China.

Publications

Deletion of pic results in decreased virulence for a clinical isolate of Shigella flexneri 2a from China.

Similar Datasets

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