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Vibrio cholerae O139 requires neither capsule nor lipopolysaccharide O side chain to grow inside Acanthamoeba castellanii

Abstract number: P1646

Abd H., Saeed A., Edvinsson B., Weintraub A., Sandström G.

Objectives:Vibrio cholerae O139, the causative agent of cholera, has grown and survived in the aquatic free-living amoeba Acanthamoeba castellanii. The aim of the present study was to examine the ability of the clinical isolate V. cholerae O139 MO10 to grow with each of A. castellanii, A. culbertsoni and A. polyphaga as well as to determine effect of bacterial capsule and LPS O side chain on the intracellular growth of V. cholerae O139 MO10 in A. castellanii.

Methods:Acanthamoeba species and V. cholerae strains were alone and co-cultivated for two weeks. Gentamicin assay was used to kill extracellular V. cholerae as well as to examine ability of amoeba to protect intracellular V. cholerae. Interaction between microorganisms was studied by viable count, mannose assay, electron microscopy and statistical analysis.

Results: The results showed that A. castellanii, A. culbertsoni and A. polyphaga grew in the presence of V. cholerae O139 MO10 and the amoeba number increased ten-fold, 2 times and 4 times after 14 days, respectively.

Growth of the wildtype V. cholerae MO10, V. cholerae MO10-T4 lacking capsule, and V. cholerae Bengal-2R lacking LPS O side chain was enhanced significantly in the presence of A. castellanii (p = 0.00003). Intracellular growth of V. cholerae strains in A. castellanii was not significant; p value of Chi-2 test was 0.999).

The addition of mannose did not affect intracellular growth of V. cholerae MO10 in A. castellanii, which indicated that the mannose did not inhibit adherence of V. cholerae to A. castellanii explaining that V. cholerae cells adhered nonspecifically to A. castellanii and nonspecific adherence plays a role of bacteria attachment to A. castellanii. The number of viable V. cholerae O139 MO10 inside A. castellanii with or without mannose was not significantly different (p = 0.94).

Electron microscopy showed that the intracellular localisation of the bacteria was in vacuoles in the cytoplasm of trophozoites a few hours after co-cultivation. Multiplication of bacterial cells occurred in the cytoplasm of trophozoites one day after co-cultivation and the bacteria were found in the cysts of A. castellanii 6 and 7 days after co-cultivation.

Conclusions: Neither the capsule nor the LPS O side chain of V. cholerae O139 was found to play an important antiphagocytic role against A. castellanii disclosing the intracellular behaviour of V. cholerae as well as the role of Acanthamoebae as environmental hosts for V. cholerae

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Subject:
Location: Barcelona, Spain
Presentation type:
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