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. 2011 Jun 10;3(1):9.
doi: 10.1186/1757-4749-3-9.

Molecular basis of virulence in clinical isolates of Escherichia coli and Salmonella species from a tertiary hospital in the Eastern Cape, South Africa

Mary A Bisi-Johnson  1 , Chikwelu L Obi, Sandeep D Vasaikar, Kamaldeen A Baba, Toshio Hattori
Affiliations

Molecular basis of virulence in clinical isolates of Escherichia coli and Salmonella species from a tertiary hospital in the Eastern Cape, South Africa

Mary A Bisi-Johnson et al. Gut Pathog. .

Abstract

Background: Apart from localized gastrointestinal infections, Escherichia coli and Salmonella species are major causes of systemic disease in both humans and animals. Salmonella spp. cause invasive infections such as enteric fever, septicemia, osteomyelitis and meningitis while certain types of E. coli can cause systemic infections, includingpyelonephritis, meningitis and septicemia. These characteristic requires the involvement of a myriad of virulence factors.

Methods: This study investigated the virulence factors of Escherichia coli and Salmonella species in clinical specimens from patients with diarrhoea presenting to health care centres in Oliver R. Tambo District Municipality, Eastern Cape Province, Republic of South Africa. Microbiology analysis involved the use of cultural and molecular techniques.

Results: Out of a total of 315 samples screened, Salmonella isolates were obtained in 119 (37.8%) of cases and these comprised: S. choleraesuis (6%), S. enteritidis (4%), S. eppendorf (1%), S. hadar (1%), S. isangi (8%), S. panama (1%), S. typhi (52%), S. typhimurium (25%) and untyped Salmonella spp. (2%). Among the Salmonella species 87 (73.1%) were invasive. Using molecular diagnostic methods, diarrheagenic E. coli were detected in 90 cases (28.6%): the greater proportion of this were enteroaggregative E. coli (EAEC) 37 (41.1%), enteropathogenic E. coli (EPEC) 21 (23.3%) and enterohemorrhagic E. coli (EHEC) 21 (23.3%). The predominant virulence gene among the diarrheagenic E. coli was EAEC heat-stable enterotoxin astA genes while the virulence genes identified in the Salmonella strains were 15 (12.6%) flic and 105 (88.2%) inv genes. The amino acid identity of the representative genes showed 95-100% similarity to corresponding blast searched sequence.

Conclusions: This study showed the diversity of virulence gene expression in two major enteric pathogens. S. typhi and enteroaggregative E. coli were the predominant enteropathogens in our study area with an indication that EAEC is endemic within our study population. It was observed among other things that some diarrheagenic E. coli isolated from apparently asymptomatic subjects expressed some virulence genes at frequency as high as seen in diarrheagenic cases. This study underlines the importance of understanding the virulence composition and diversity of pathogens for enhanced clinico-epidemiological monitoring and health care delivery.

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Figures

Figure 1
Figure 1
Frequency distribution of the various Salmonella isolates. S = Salmonella.
Figure 2
Figure 2
Frequency distribution of the diarrheagenic E. coli isolates. EPEC = Enteropathogenic Escherichia coli; EHEC = Enterohemorrhagic E. coli: EAEC = Enteroaggregative E. coli: Enterotoxigenic E. coli: EIEC = Enteroinvasive E. coli.
See this image and copyright information in PMC

References

    1. Amar CF, East CL, Gray J, Iturriza-Gomara M, Maclure EA, McLauchlin J. Detection by PCR of eight groups of enteric pathogens in 4,627 faecal samples: re-examination of the English case-control Infectious Intestinal Disease Study (1993-1996) Eur J Clin Microbiol Infect Dis. 2007;26:311–323. doi: 10.1007/s10096-007-0290-8. - DOI - PubMed
    1. Gordon MA. Salmonella infections in immunocompromised adults. J Infect. 2008;56:413–422. doi: 10.1016/j.jinf.2008.03.012. - DOI - PubMed
    1. Falkow S. In: Escherichia coli and Salmonella: cellular and molecular biology. 2. Neidhardt FC, Curtiss R III, Ingraham JL, Lin ECC, Low KB Jr, Magasanik B, Reznikoff WS, Riley M, Schaechter M, Umbarger HE, editor. American Society for Microbiology (ASM) Press, Washington, D.C; 1996. The evolution of pathogenicity in Escherichia, Shigella, and Salmonella; pp. 2723–2729.
    1. Selander RK, Musser JM. In: Molecular Basis of Bacterial Pathogenesis. Iglewski BH, Clark VL, editor. Academic Press, Inc., San Diego, Calif; 1990. Population genetics of bacterial pathogenesis; pp. 11–36.
    1. Finlay BB, Falkow S. Common themes in microbial pathogenicity revisited. Microbiol Mol Biol Rev. 1997;61:136–169. - PMC - PubMed