ENVIRONMENTAL GROWTH FACTORS AND IDENTIFICATION OF V. CHOLERAE FROM DIARRHEAL PATIENTS IN BALOCHISTAN

Abstract

Background: Cholera remains a significant public health concern in developing countries such as Pakistan, caused by Vibrio cholerae, a Gram-negative, motile, curved rod-shaped bacterium that thrives in aquatic environments. Although over 200 serogroups have been identified, only O1 and O139 are responsible for epidemic outbreaks.

Objective: This study aimed to evaluate the identification of V. cholerae isolates from diarrheal patients using biochemical and serological methods, alongside assessing the influence of environmental factors, particularly temperature and pH, on their growth.

Methods: from September 2022 to September 2023, 888 stool samples were collected from suspected cholera patients across hospitals in Balochistan. The samples were cultured on thiosulfate-citrate-bile salts-sucrose agar, and colonies suggestive of V. cholerae were further examined by Gram staining, biochemical tests, and serological identification. Additionally, the growth pattern of isolates was tested at varying temperatures (10°C, 15°C, 25°C,  37°C, and above 50°C) and pH levels (4–12) to determine optimal environmental conditions.

Results: Of the total samples, 66 tested positive for V. cholerae. Serotyping confirmed that 55 isolates belonged to serogroup O1 Ogawa, while 11 (8.3%) were identified as non-O1/non-O139 serogroups, showing no agglutination with Inaba, Ogawa, or O139 antisera. Temperature greatly affected bacterial growth, with optimal proliferation at 37°C, moderate growth at 25°C, and no growth at 10°C, 15°C  and 50°C. The organism demonstrated maximum growth in an alkaline environment, particularly between pH 8 and 12, with negligible growth at pH 7, and complete inhibition at pH 5.

Conclusion: The findings confirm that V. cholerae multiplies efficiently in aquatic environments under moderate temperatures and alkaline conditions, facilitating its survival and transmission. Routine laboratory diagnosis employing both culture-based biochemical tests and serological identification is crucial for detecting circulating V. cholerae strains and implementing effective public health interventions in Balochistan.