Occurrence of neuraminidase and acylneuraminate pyruvate lyase in a strain of vibrio falling into Heiberg's group II isolated from a patient with diarrhea

Biochemical studies on the production of neuraminidase by environmental isolates of Vibrio cholerae non-O1 from Bulgaria

Neuraminidase is a key factor in the infectious process of many viruses and pathogenic bacteria. The neuraminidase enzyme secreted by the etiological agent of cholera — Vibrio cholerae О1 — is well studied in contrast with the one produced by non-O1/non-O139 V. cholerae. Environmental non-O1/non-O139 V. cholerae isolates from Bulgaria were screened for production of neuraminidase. The presence of the neuraminidase gene nanH was detected in 18.5% of the strains. Тhe strain showing highest activity (30 U/mL), V. cholerae non-O1/13, was used to investigate the enzyme production in several media and at different aeration conditions. The highest production of extracellular neuraminidase was observed under microaerophilic conditions, which is possibly related to its role in the infection of intestine epithelium, where the oxygen content is low. On the other hand, this is another advantage of the microbe in such microaerophilic environments as sediments and lake mud. The highest production of intracellular neuraminidase was observed at anaerobic conditions. The ratio of extracellular to intracellular neuraminidase production in V. cholerae was investigated. The temperature optimum of the enzyme was determined to be 50 °C and the pH optimum to be 5.6–5.8.

Neuraminidase production by Vibrio cholerae O1 and other diarrheagenic bacteria

Vibrio cholerae O1 strains belonging to both biotypes (classical and El Tor) and both serotypes (Ogawa and Inaba) produced neuraminidase which was released rather than cell bound. Classical strains made more neuraminidase than did El Tor strains. About one-third of V. cholerae non-O1 strains and one-fourth of Aeromonas hydrophila strains were neuraminidase positive. Strains of enterotoxigenic Escherichia coli, Vibrio parahaemolyticus, and Shigella spp. did not produce detectable neuraminidase.

Neuraminidase activity of NAG vibrios and of some representatives of the intestinal group of bacteria

It was studied 203 strains of NAG vibrios and 71 strains of different enterobacteria for the ability to produce neuraminidase. The most frequent neuraminidase producers were found among the strains isolated from humans (99 strain of 131). There was no correlation between neuraminidase production and other properties of the vibrios. The examined strains of the family Enterobacteriaceae did not produce the enzyme.