TY - JOUR
T1 - Virulence of Cholera Toxin Gene-Positive Vibrio cholerae Non-O1/non-O139 Strains Isolated From Environmental Water in Kolkata, India
AU - Takahashi, Eizo
AU - Ochi, Sadayuki
AU - Mizuno, Tamaki
AU - Morita, Daichi
AU - Morita, Masatomo
AU - Ohnishi, Makoto
AU - Koley, Hemanta
AU - Dutta, Moumita
AU - Chowdhury, Goutam
AU - Mukhopadhyay, Asish K.
AU - Dutta, Shanta
AU - Miyoshi, Shin Ichi
AU - Okamoto, Keinosuke
N1 - Funding Information:
We thank National Institute of Infectious Diseases of Japan for providing 206 O group-specific serum of V. cholerae. Funding. This work was supported by the Japan Initiative for Global Research Network on Infectious Diseases (J-GRID) from the Ministry of Education, Culture, Sports, Science and Technology in Japan and the Japan Agency for Medical Research and Development (AMED) under grant number JP19fm0108002.
Funding Information:
This work was supported by the Japan Initiative for Global Research Network on Infectious Diseases (J-GRID) from the Ministry of Education, Culture, Sports, Science and Technology in Japan and the Japan Agency for Medical Research and Development (AMED) under grant number JP19fm0108002.
Publisher Copyright:
© Copyright © 2021 Takahashi, Ochi, Mizuno, Morita, Morita, Ohnishi, Koley, Dutta, Chowdhury, Mukhopadhyay, Dutta, Miyoshi and Okamoto.
PY - 2021/8/20
Y1 - 2021/8/20
N2 - Cholera toxin (CT)-producing Vibrio cholerae O1 and O139 cause acute diarrheal disease and are proven etiological agents of cholera epidemics and pandemics. On the other hand, V. cholerae non-O1/non-O139 are designated as non-agglutinable (NAG) vibrios and are not associated with epidemic cholera. The majority of NAG vibrios do not possess the gene for CT (ctx). In this study, we isolated three NAG strains (strains No. 1, 2, and 3) with ctx from pond water in Kolkata, India, and examined their pathogenic properties. The enterotoxicity of the three NAG strains in vivo was examined using the rabbit ileal intestinal loop test. Strain No. 1 induced the accumulation of fluid in the loop, and the volume of fluid was reduced by simultaneous administration of anti-CT antiserum into the loop. The volume of fluid in the loop caused by strains No. 2 and 3 was small and undetectable, respectively. Then, we cultured these three strains in liquid medium in vitro at two temperatures, 25°C and 37°C, and examined the amount of CT accumulated in the culture supernatant. CT was accumulated in the culture supernatant of strain No.1 when the strain was cultured at 25°C, but that was low when cultured at 37°C. The CT amount accumulated in the culture supernatants of the No. 2 and No. 3 strains was extremely low at both temperature under culture conditions examined. In order to clarify the virulence properties of these strains, genome sequences of the three strains were analyzed. The analysis showed that there was no noticeable difference among three isolates both in the genes for virulence factors and regulatory genes of ctx. However, vibrio seventh pandemic island-II (VSP-II) was retained in strain No. 1, but not in strains No. 2 or 3. Furthermore, it was revealed that the genotype of the B subunit of CT in strain No. 1 was type 1 and those of strains No. 2 and 3 were type 8. Histopathological examination showed the disappearance of villi in intestinal tissue exposed to strain No. 1. In addition, fluid accumulated in the loop due to the action of strain No. 1 had hemolytic activity. This indicated that strain No. 1 may possesses virulence factors to induce severe syndrome when the strain infects humans, and that some strains of NAG vibrio inhabiting pond water in Kolkata have already acquired virulence, which can cause illness in humans. There is a possibility that these virulent NAG vibrios, which have acquired genes encoding factors involved in virulence of V. cholerae O1, may emerge in various parts of the world and cause epidemics in the future.
AB - Cholera toxin (CT)-producing Vibrio cholerae O1 and O139 cause acute diarrheal disease and are proven etiological agents of cholera epidemics and pandemics. On the other hand, V. cholerae non-O1/non-O139 are designated as non-agglutinable (NAG) vibrios and are not associated with epidemic cholera. The majority of NAG vibrios do not possess the gene for CT (ctx). In this study, we isolated three NAG strains (strains No. 1, 2, and 3) with ctx from pond water in Kolkata, India, and examined their pathogenic properties. The enterotoxicity of the three NAG strains in vivo was examined using the rabbit ileal intestinal loop test. Strain No. 1 induced the accumulation of fluid in the loop, and the volume of fluid was reduced by simultaneous administration of anti-CT antiserum into the loop. The volume of fluid in the loop caused by strains No. 2 and 3 was small and undetectable, respectively. Then, we cultured these three strains in liquid medium in vitro at two temperatures, 25°C and 37°C, and examined the amount of CT accumulated in the culture supernatant. CT was accumulated in the culture supernatant of strain No.1 when the strain was cultured at 25°C, but that was low when cultured at 37°C. The CT amount accumulated in the culture supernatants of the No. 2 and No. 3 strains was extremely low at both temperature under culture conditions examined. In order to clarify the virulence properties of these strains, genome sequences of the three strains were analyzed. The analysis showed that there was no noticeable difference among three isolates both in the genes for virulence factors and regulatory genes of ctx. However, vibrio seventh pandemic island-II (VSP-II) was retained in strain No. 1, but not in strains No. 2 or 3. Furthermore, it was revealed that the genotype of the B subunit of CT in strain No. 1 was type 1 and those of strains No. 2 and 3 were type 8. Histopathological examination showed the disappearance of villi in intestinal tissue exposed to strain No. 1. In addition, fluid accumulated in the loop due to the action of strain No. 1 had hemolytic activity. This indicated that strain No. 1 may possesses virulence factors to induce severe syndrome when the strain infects humans, and that some strains of NAG vibrio inhabiting pond water in Kolkata have already acquired virulence, which can cause illness in humans. There is a possibility that these virulent NAG vibrios, which have acquired genes encoding factors involved in virulence of V. cholerae O1, may emerge in various parts of the world and cause epidemics in the future.
KW - NAG Vibrio
KW - Vibrio cholerae
KW - cholera toxin
KW - environmental water
KW - gene analysis
KW - virulence
UR - http://www.scopus.com/inward/record.url?scp=85114357863&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85114357863&partnerID=8YFLogxK
U2 - 10.3389/fmicb.2021.726273
DO - 10.3389/fmicb.2021.726273
M3 - Article
AN - SCOPUS:85114357863
SN - 1664-302X
VL - 12
JO - Frontiers in Microbiology
JF - Frontiers in Microbiology
M1 - 726273
ER -