Outbreak of cholera in a remote village in western India

Background & objectives: Atypical El Tor strains of Vibrio cholerae are frequently implicated in outbreaks of cholera. It is important to understand genetic variations of such strains which impact clinical and epidemiological outcomes. The present study was carried out to characterize an outbreak of cholera which occurred between July 8 and 13, 2018, in a remote settlement in Nashik district, Maharashtra. Methods: A large number of acute diarrhoea cases were reported in Rahude village, Nashik, Maharashtra since July 8, 2018. Molecular characterization of the isolated strains of V. cholerae was done. Results: 195 cases of cholera were detected from a population of 850 (attack rate 22.9%) with two deaths (Case Fatality Ratio of 1.03). A non-haemolytic polymyxin B sensitive strain of V. cholerae O1 Ogawa was isolated from 5/14 fecal samples. Molecular characterization of the isolates indicated that this strain was an altered El Tor (AET) strain. Deletion of the trinucleotide ‘GTA’ in the rstB gene, a unique feature of classical strains, was observed. Interpretation & conclusions: A cholera outbreak caused by a non-haemolytic polymixin B sensitive AET strain, occurred from July 8 to 13, 2018, in a remote settlement in western India. The molecular characterization of the outbreak strains highlighted an assortment of genetic determinants, stressing the need to monitor the genetic attributes of V. cholerae O1 in outbreaks for better understanding and mapping of clinical and epidemiological changes.

Genetic Characteristics and Relatedness of Imported Vibrio cholerae O1 Biotype El Tor in Korea / 대한임상미생물학회지

BACKGROUND: Cholera is a representative water-borne disease that is caused by V. cholera ctx (+). V. cholera El Tor was previously the primary pathogen, but after the seventh pandemic outbreak, it was replaced by a V. cholera El Tor variant with a classical phenotype and genotype. In this study, we investigated the genotypic and phenotypic characteristics of imported V. cholerae El Tor in Korea. METHODS: Forty-nine V. cholerae O1 El Tor strains isolated from 2004 to 2011 were used in this study. Polymerase chain reaction amplification of the ctxB and rstR genes was used for biotype determination. An antimicrobial susceptibility test was performed for phenotypic analysis, and pulse field gel electrophoresis (PFGE) was used for analysis of genetic relatedness. RESULTS: Classical ctxB genes were found in all of the isolates, while classical, El Tor, and combined rstR genes were found. Twenty strains showed antimicrobial resistance against streptomycin, sulfamethoxazole/trimethoprim, nalidixic acid, and ciprofloxacin. Based on PFGE, all isolates were grouped as cluster B. The country of origin and resistance pattern were highly related, although the time of influx and serogroup were not. CONCLUSION: Isolates of V. cholera El Tor imported since 2004 were hybrids of V. cholera El Tor, which has the classical ctxB gene and is considered to be a CTX prophage. The SXT element plays an important role in antimicrobial resistance. PFGE patterns, which can be used for analysis of imported V. cholera, revealed the relatedness of the resistant isolates.

Hybrid & El Tor variant biotypes of Vibrio cholerae O1 in Thailand.

Background & objectives: El Tor Vibrio cholerae O1 carrying ctxBC trait, so-called El Tor variant that causes more severe symptoms than the prototype El Tor strain, first detected in Bangladesh was later shown to have emerged in India in 1992. Subsequently, similar V. cholerae strains were isolated in other countries in Asia and Africa. Thus, it was of interest to investigate the characteristics of V. cholerae O1 strains isolated chronologically (from 1986 to 2009) in Thailand. Methods: A total of 330 V. cholerae O1 Thailand strains from hospitalized patients with cholera isolated during 1986 to 2009 were subjected to conventional biotyping i.e., susceptibility to polymyxin B, chicken erythrocyte agglutination (CCA) and Voges-Proskauer (VP) test. The presence of ctxA, ctxB, zot, ace, toxR, tcpAC, tcpAE, hlyAC and hlyAE were examined by PCR. Mismatch amplification mutation assay (MAMA) - and conventional- PCRs were used for differentiating ctxB and rstR alleles. Results: All 330 strains carried the El Tor virulence gene signature. Among these, 266 strains were typical El Tor (resistant to 50 units of polymyxin B and positive for CCA and VP test) while 64 had mixed classical and El Tor phenotypes (hybrid biotype). Combined MAMA-PCR and the conventional biotyping methods revealed that 36 strains of 1986-1992 were either typical El Tor, hybrid, El Tor variant or unclassified biotype. The hybrid strains were present during 1986-2004. El Tor variant strains were found in 1992, the same year when the typical El Tor strains disappeared. All 294 strains of 1993-2009 carried ctxBC ; 237 were El Tor variant and 57 were hybrid. Interpretation & conclusions: In Thailand, hybrid V. cholerae O1 (mixed biotypes), was found since 1986. Circulating strains, however, are predominantly El Tor variant (El Tor biotype with ctxBC).

An experimental study of phage mediated bactericidal selection & emergence of the El Tor Vibrio cholerae.

Background & objectives: Factor causing the elimination of the classical biotype of Vibrio cholerae O1, and its replacement by the El Tor biotype causing the 7th cholera pandemic are unclear. Possible ability of the El Tor strains to adapt better than the classical strains to undefined environmental forces have been largely implicated for the change. Here we describe an environmental bacteriophage designated JSF9 which might have contributed to the range of factors. Methods: Competition assays were conducted in the infant mice model and in microcosms between representative El Tor and classical biotype strains in the absence or in the presence of JSF9 phage. Results: The JSF9 phage was found to kill classical strains and favour enrichment of El Tor strains, when mixtures containing strains of the two biotypes and JSF9 phage were subjected to alternate passage in infant mice and in samples of environmental water. Spontaneous derivatives of the classical biotype strains, as well as transposon mutants which developed resistance to JSF9 phage were found to be defective in colonization in the infant mouse model. Interpretation & conclusions: These results suggest that in addition to other factors, the inherent ability of El Tor biotype strains to evade predation by JSF9 or similar phages which kill classical biotype strains, might have enhanced the emergence of El Tor strains as the predominant pandemic biotype.

A De in the life of cholera.

The 50-year commemoration of S.N. De’s seminal 1959 publication in Nature provides an opportunity to reflect on scientific discovery, recognition, and public health. De’s paper marked the first major conceptual advance in cholera research since 1884, when Robert Koch definitively identified Der Kommabazillus as the aetiological agent of cholera. Unfortunately, Koch reported that systemic toxinosis and multi-organ failure led to severe dehydrating diarrhoea, thereby mistaking cause for effect. As a consequence, while work on other microbial pathogens advanced into the development of vaccines and therapeutics, cholera research languished as scientists injected animals parenterally in decades of futile effort to develop an animal model of diarrhoea. This fundamental misconception in cholera pathogenesis was swept away when S.N. De used ligated loops of rabbit ileum to demonstrate lumenal fluid accumulation in the presence of Vibrio cholerae culture filtrates. After some delay, De’s observation of a diarrhoeagenic exotoxin became the founding principle of modern cholera research, vaccination, and treatment; and a burst of discovery saw V. cholerae transformed into the enteric pathogen best understood at the molecular level. The scientific basis for orally administering vaccines to induce mucosal immunity was established, and the success of oral rehydration, what has been described as one of the 20th century’s most important medical advances, was explained.Nobel laureate Joshua Lederberg wrote of De’s iconoclastic creativity, experimental skill, and observational mastery, and many other leaders in the field concurred. De was nominated for the Nobel Prize in Physiology or Medicine more than once. But despite the passage of half a century from De’s work, cholera remains a frustrating problem: we are clearly missing something. In reviewing the scientific and programmatic impact of S.N. De on cholera, it is clear that a defining victory against the disease is achievable, but only if basic scientific discoveries are relentlessly driven towards progress in public health.

The Survival of Vibrio cholerae in the Natural Environment of Zambia : Fish, the suspicious Gateway of Cholera Outbreak? / 国際保健医療

<b>Preface and Objectives</b><br> Cholera has recently become more serious in African countries. In southern Africa, a serious cholera outbreak was reported in 2008. Here we investigate <i>Vibrio cholerae</i> in aquatic environments, rivers, tube well waters, fish tissues, and aquatic plants in Zambia.<br><b>Methods</b><br> The sampling was conducted on Kafue and Zambezi rivers as well as at public wells. The samples included river water, mud, fish, floating grass, and well water. All samples were enriched in alkaline peptone water (APW) and streaked on thiosulfate citrate bilesalts saccharos (TCBS) Vibrio agar. Some types of colonies were isolated using polymyxin mannose tellurite (PMT) agar. All water samples were analyzed for enterobacteria as well as vibrio contamination. River and shallow tube well water samples were analyzed for <i>E. coli</i>.<br><b>Results</b><br> Samples, including fish tissues, river, and tube well waters, except for the fish intestines, were found to be contaminated with vibrios when cultured on TCBS Vibrio agar.<br> Deep tube well water was not contaminated with vibrios or <i>E. coli. V. cholerae</i> El Tor was not detected through sampling and culturing on PMT agar. <i>E. coli</i> was detected in river and shallow tube well water samples.<br><b>Discussion</b><br> Vibrios were detected in Zambia’s aquatic environments. Cholera outbreak may occur. Vibrio contaminations in fish have been reported from Bangladesh, Laos, Kenya, and India. Fish is a good source of protein to improve person’s nutritional status. However, it must be treated properly so that any contamination of residential areas is avoided. Therefore, people must pay attention to fish.<br><b>Conclusion</b><br> Here several types of <i>V. cholerae</i> were isolated from different aquatic environments. Fish is a nutritious diet, but contaminated Vibrios fish must be treated so that it will not contaminate residential areas. We must investigate the gateway of cholera outbreaks in Zambia.

Cholera outbreak secondary to contaminated pipe water in an urban area, West Bengal, India, 2006.

Outbreaks of cholera are common in West Bengal. In April 2006, Garulia municipality reported a cluster of diarrhea cases. We investigated this cluster to identify the etiological agent, source of transmission and propose control measures. We defined a case of diarrhea as occurrence of >3 loose/watery stools a day among the residents of Garulia since April 2006. We searched for cases of diarrhea in health care facilities and health camp. We conducted a gender- and age-matched case–control study to identify risk factors. We inspected the sanitation and water supply system. We collected rectal swabs from diarrhea patients and water specimens from the affected areas for laboratory investigation. Two hundred and ninetyeight cases of diarrhea were reported to various health care facilities (attack rate: 3.5/1000, no deaths). The attack rate was highest among children (6.4/1000). Vibrio cholerae El Tor O1 Inaba was isolated from two of 7 rectal swabs. The outbreak started on 10 April 2006, peaked on 26 April and lasted till 6 May. Cases clustered in an area distal to leaking water pipelines. Drinking municipal water exclusively was significantly associated with the illness (OR 13, 95% CI=6.5–27). Eight of the 12 water specimens from the affected area had fecal contamination and poor chlorine content. This outbreak was due to a contaminated municipal piped water supply and V. cholera 01 Inaba was possibly the causative organism.

Preliminary clinical experiences on the use of antimicrobials in cholera El Tor

A total of 184 actual and suspected cases of Cholera El Tor were admitted during a 4-month period from August to November, 1969. There were 70 pediatric and 114 adult cases. The mortality rate is 7.1% for children and 1.7% for adults. Bacteriologically positive rectal swabs were obtained in 80%. This study shows that the use of antimicrobials, either trimethoprim-sulfamethoxazole, nalidixic acid or chloramphenicol, significantly reduced the duration in days of positivity of rectal swabs.(Author)

Serological studies in El tor cholera

Three test were utilized, namely agglutination, vibriocidal and the hemolysis-inhibition tests in determining the serological responses of 161 immunized individuals in this study. Three vaccines were given in different dosage regimen - El Tor, mixed El tor and cholera , and classical cholera vaccines. Higher agglutinative and vibriocidal antibody titers were obtained among those immunized with two or three doses of El Tor vaccine than with the other two types of vaccines. The agglutinating antibody response to classical Inaba and Ogawa challenge by those given the El tor vaccine was even higher than those that received classical cholera vaccine. Antibodies to both classical and El Tor strains of cholera vaccine but to a lesser degree than by either the pure El Tor or the mixed vaccine. These differences in percentage with rise in agglutinative titer were found significant by statistical analysisIt was further obseved that the reduction in vibriocidal antibody titer was not as marked as in the agglutinative antibody titer 6 months after primary immunization. It is of special interest and utmost importance to note that the usual single 1 cc. adult dose given as a booster 6 months after the primary immunization failed to produce sufficient agglutinative antibodies and on this basis it is felt that the double regimen should instead be preferred. (Summary)

Experience with the cholera-el tor epidemic in Capiz

Two hundred cases of cholera-El Tor in Capiz province are presented. The epidemiology, clinical picture, complications and treatment are discussed.Emphasis is placed on the treatment outlined. The basic needs of a community are outlined to help combat this epidemic. (Summary)

INDUCEMENT AND MORPHOLOGIC OBSERVATION OF L-FORM OF VIBRIO CHOLERAE, EL TOR BIOTYPE / 微生物学通报

L-forms of Vibrio cholerae, El Tor biotype were induced by penicillin under the condition of liquid and solid media, and observed morphologically. It showed that the typical L-form colonies like oil-fried egg (L-form), granular form (Gform) and fibrous form (F-form) were seen after 3-10-time inducements under the microscope. At the beginning, it was observed that the bodies of bacteria expanded, and then became short-rod, long-chain and finally fibre-like bodies.