Date of Award

Fall 2006

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Ocean & Earth Sciences

Program/Concentration

Occupational and Technical Studies

Committee Director

Fred C. Dobbs

Committee Member

Wayne Hynes

Committee Member

Andrew Gordon

Call Number for Print

Special Collections LD4331.O35 G56 2006

Abstract

Vibrio cholerae serotypes 01 and 0139 are responsible for world-wide epidemics of cholera. These pandemic causing strains must possess genes that encode for the cholera toxin (CTX) and toxin co-regulated pili (TCP) in order to infect their hosts. In this study, 284 isolates of Vibrio cholerae from ballast and coastal waters were serotyped, with 11 % testing positive for serotype 01 and 21 % testing positive for serotype 0139. PCR assays were used to detect the presence of ctxA and tcpA genes in all positive isolates, none of which contained ctxA while 2% of the isolates contained tcpA. The 01 and 0139 isolates were tested using a nitrocefin assay for the presence of 13-lactamase, an enzyme that protects V cholerae from 13-lactam antibiotics. These results were combined with antibiotic-susceptibility profiles and the isolates were divided into 4 different groups defined by their antibiotic characteristics. Finally, the plasmids of 3 isolates were digested using restriction enzymes and compared according to the band sizes produced.

Fifty percent of isolates from ballast tanks were found to be serotype 0139. This result is consistent with current pandemics of cholera which are considered to be caused by this serotype. It is also thought to be the more virulent and robust of the two pandemic serotypes. The dearth of ctxA and tcpA gene sequences, however, is expected in environmental isolates from areas not undergoing a cholera pandemic. Among the isolates collected from coastal areas, those that were serotype 01 were most often found in very near-shore environments while serotype 0139 were most often collected from open water environments, a difference possibly related to their methods of attachment to plankton and other particles. Serotype 0139 exhibited less antibiotic-resistance and was less likely to produce P-lactamase than serotype 01. This result supports data from other studies which determined that serotype 01 is more resistant to P-lactam antibiotics while serotype 0139 is more sensitive to them.

Ballast water management is important for preventing the spread of Vibrio cholerae and possible resulting pandemics. The International Maritime Organization has established some regulations on ballast water but more consideration needs to be given towards bacteria in other ballast tank environments, such as biofilms and sediment, as well as non-01 and non-0139 serotypes of Vibrio cholerae.

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DOI

10.25777/qdv4-wm04

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