Nontoxigenic Vibrio cholerae Non-O1/O139 Isolate from a Case of Human Gastroenteritis in the U.S. Gulf Coast

Abstract

An occurrence of Vibrio cholerae non-O1/O139 gastroenteritis in the U.S. Gulf Coast is reported here. Genomic analysis revealed that the isolate lacked known virulence factors associated with the clinical outcome of a V. cholerae infection but did contain putative genomic islands and other accessory virulence factors. Many of these factors are widespread among environmental strains of V. cholerae, suggesting that there might be additional virulence factors in non-O1/O139 V. cholerae yet to be determined. Phylogenetic analysis revealed that the isolate belonged to a phyletic lineage of environmental V. cholerae isolates associated with sporadic cases of gastroenteritis in the Western Hemisphere, suggesting a need to monitor non-O1/O139 V. cholerae in the interest of public health. Vibrio spp. are natural inhabitants of marine and estuarine environments, and they cause human infections that most commonly present as gastroenteritis or wound infections and/or septicemia (1, 2). The infection is generally acquired through the consumption of contaminated food or water or by the direct invasion of wounds (3). Vibrio cholerae is the causative agent of cholera, the severe watery diarrheal disease that has the potential to become pandemic. Based on variable somatic (outer membrane) O-antigen composition, more than 200 serogroups of V. cholerae have been recognized to date (4). Of them, toxigenic strains of V. cholerae typically belong to serogroups O1 or O139 and are rare in the United States (5). All other serogroups, notably the non-O1/O139 serogroup, are frequently isolated from environmental sources and have been associated with sporadic cases of gastroenteritis or extraintestinal infections. Although none has caused a pandemic yet (6), these serogroups have reportedly caused epidemics of cholera through the acquisition of genes carried on mobile elements (e.g., O antigens, vibrio pathogenicity island 1 [VPI-1], VPI-2, cholera toxin phage [CTX], and heatstable enterotoxin [NAG-ST]). Human illnesses caused by environmental V. cholerae non-O1/O139 serogroups are reported regularly (7). Over the past few decades, environmental studies have shown that nontoxigenic V. cholerae strains inhabit estuarine waters along the Atlantic and Gulf coasts (8-14). They are most commonly isolated from environmental sources, such as brackish water, oysters, and sewage, and have been reported in many countries, such as Bangladesh, Brazil, Guam, Great Britain, and the United States, even when cholera outbreaks had not been recorded for decades in those countries (2).In the United States, the consumption of raw or undercooked seafood is the leading cause of non-O1/O139 V. cholerae-associated gastroenteritis, with isolated cases reported (8,15). Outbreaks of intestinal illness caused by non-O1/O139 V. cholerae have been reported more commonly than would be expected (16)(17)(18). Since 2000, an average of 44 cases has been reported each year (http:// www.cdc.gov/nationalsurveillance/cholera-vibrio-surveillance .html). The majority of infectio...

A genomic island in Vibrio cholerae with VPI-1 site-specific recombination characteristics contains CRISPR-Cas and type VI secretion modules

“…Previous studies have observed variations in VPI-1 through PCR analysis of V. cholerae strains or BLASTN analysis of V. cholerae genomes for VPI-1 genes. For the most part, the variations identified represent minor gene gain/loss events or sequence changes to known ORFs in VPI-1101112. GI Vch S12 is different in that it shares practically no gene content with VPI-1.…”

“…Most important to pathogenicity of the pandemic strains are genes found on two MGEs, the cholera toxin bacteriophage (CTXϕ) and a GI called the V. cholerae pathogenicity island 1 (VPI-1)89. Although these MGEs are common in pandemic strains, examples of CTXϕ and VPI-1 in non-O1/O139 strains have been documented and are indicative of their mobility across natural populations of V. cholerae and close relatives101112. The CTXϕ contains genes encoding a potent enterotoxin that, when secreted in the human intestinal tract, results in significant loss of fluid that can lead to death within 24 hours if left untreated1.…”

Septicemia secondary toVibrio cholerae(non-O1/non-O139) in wound

“…V. cholerae is an aerobic, Gram-negative bacteria mostly inhabiting saltwater. Based on serotypes and outer membrane O-antigen composition, they are broadly classified into O1, O139, and non-O1/non-O139 1 3…”

Interbacterial competition and anti-predatory behavior of environmentalVibrio choleraestrains

“…These mostly non-O1/non-O139 serogroup strains are thought to frequently associate with zooplankton and shellfish, and V. cholerae uses their chitinous exoskeletons as a source of carbon and nitrogen (Faruque et al, 1998;Cottingham et al, 2003;Kirn et al, 2005). Environmental isolates are typically considered harmless to humans despite reported associations with mild to severe forms of diarrhea (Islam et al, 1992;Singh et al, 2001;Dziejman et al, 2002Dziejman et al, , 2005Onifade et al, 2011;Deshayes et al, 2015;Hasan et al, 2015).…”