Incidence, Virulence Factors, and Clonality among Clinical Strains of Non-O1, Non-O139 Vibrio cholerae Isolates from Hospitalized Diarrheal Patients in Kolkata, India

Abstract

The incidence of Vibrio cholerae non-O1, non-O139 strains from hospitalized patients with acute diarrhea constituted 27.4% (n ‫؍‬ 54) of the total 197 V. cholerae strains isolated from patients in Kolkata, India, in 2003. Of 197 strains, 135 were identified as O1 serotype Ogawa and 2 were identified as O139. In the same time period, six O1 background rough strains that possessed all known virulence factors were identified. Serotype analysis of the non-O1, non-O139 strains placed 42 strains into 19 serogroups, while 12 remained O nontypeable (ONT); the existing serotyping scheme involved antisera to 206 serogroups. Detection of a good number of ONT strains suggested that additional serogroups have arisen that need to be added to the current serotyping scheme. The non-O1, non-O139 strains were nontoxigenic except for an O36 strain (SC124), which regulated expression of cholera toxin as O1 classical strains did. Additionally, strain SC124 carried alleles of tcpA and toxT that were different from those of the O1 counterpart, and these were also found in five clonally related strains belonging to different serogroups. Strains carrying tcpA exhibited higher colonization in an animal model compared to those lacking tcpA. PCR-based analyses revealed remarkable variations in the distribution of other virulence factors, including hlyA, rtxA, Vibrio seventh pandemic island I (VSP-I), VSP-II, and type III secretion system (TTSS). Most strains contained hlyA (87%) and rtxA (81.5%) and secreted cytotoxic factors when grown in vitro. Approximately one-third of the strains (31.5%) contained the TTSS gene cluster, and most of these strains were more motile and hemolytic against rabbit erythrocytes. Partial nucleotide sequence analysis of the TTSS-containing strains revealed silent nucleotide mutations within vcsN2 (type III secretion cytoplasmic ATPase), indicating functional conservation of the TTSS apparatus.In the recorded history of cholera, humans have experienced seven pandemics; the seventh pandemic is still ongoing since its commencement in 1961 (29). Cholera is a waterborne disease that afflicts millions of people every year. The etiological agent of the disease is Vibrio cholerae belonging to serogroups O1 and O139 (4, 29). Members of the O1 serogroup have been further subdivided into Ogawa and Inaba serotypes and El Tor and classical biotypes. The seventh pandemic strains are of the O1 El Tor biotype, which replaced the O1 classical biotype strains that caused previous pandemics (29). The current serotyping scheme of V. cholerae includes 206 serogroups (57). Strains belonging to serogroups other than O1 and O139 are collectively known as non-O1, non-O139 V. cholerae strains and exist in abundance in the aquatic environment. However, recent studies have concluded that considerable incidence of human diarrheal episodes in many countries, including India, is due to V. cholerae non-O1, non-O139 (10,11,27,39,40,48). Studies of diarrheal cases in Thailand between 1993 and 1995 revealed that the prevalence of non-O1, non-O13...

Fatal Diarrheal Disease Caused by <i>Vibrio cholerae</i> O67 in a Patient with Myelodysplastic Syndrome

“…Several studies have reported that some Vibrio cholerae non-O1/non-O139 induce bacteremia in patients with underlying diseases, including hepatic cirrhosis and hematological disorders, which can become serious (6)(7)(8). The number of cases of Vibrio cholerae non-O1/ non-O139-induced bacterial diarrheal disease in developing countries has increased in recent years (2)(3)(4)(5). In Japan, isolation of Vibrio cholerae non-O1/non-O139 has also been reported in various regions of river water as well as fish and shellfish (5).…”

“…Nevertheless, some patients with the same severe diarrhea as that caused by Vibrio cholerae O1 and O139 have been reported, which suggests the presence of intestinal virulence factors other than the cholera toxin (3,8). We herein present a case in which an immunocompromised patient with myelodysplastic syndrome (MDS) who received azacitidine developed Vibrio cholerae non-O1/non-O139-induced bacterial diarrheal disease that resulted in a fatal outcome.…”

“…The other serogroups are known as Vibrio cholerae non-O1 (nontoxigenic Vibrio cholerae) and extensively inhabit the aquatic environment around Southeastern Asia (2,3). Similar to Vibrio cholerae O1 and O139, some Vibrio cholerae non-O1/non-O139 are enteropathogenic and have been reported to cause choleralike epidemics (2)(3)(4). Among afferent infectious diseases, these serogroups are one of the main causative organisms of bacterial diarrheal disease (5).…”

Environmental Factors Influencing Epidemic Cholera

“…A similar role for V. cholerae non-O1/non-O139 strains was identified in a large-scale molecular analysis of strains isolated during a cholera outbreak in Kolkata, India. 44 Interestingly, before the Haiti outbreak of cholera, the public health risk of human pathogens in surface waters of Haiti had not been evaluated and no reportable waterborne diseases were listed. 45 Our recent collaboration with the United States CDC reported V. cholerae non-O1/O139, Vibrio parahaemolyticus, human pathogenic viruses, and Cryptosporidium spp.…”

In Vitro Inhibition of Cholera Toxin Production in <i>Vibrio cholerae</i> by Methanol Extract of Sweet Fennel Seeds and Its Components

“…Although more than 200 O serogroups of V. cholerae have been identified so far, only O1 (El Tor and classical biotypes) and O139 are responsible for cholera epidemics (2). Serogroups other than O1 and O139 (non-O1/non-O139) are associated with sporadic cases of diarrhea (3). A variant of V. cholerae O1 El Tor biotype, possessing some attributes of the classical biotype, has emerged recently and was isolated from hospitalized patients with diarrhea more severe than that caused by typical El Tor strains (4,5).…”