Genomic diversity among Vibrio cholerae O139 strains isolated in Bangladesh and India between 1992 and 1998

Resistance of Vibrio cholera to antibiotics that inhibit cell wall synthesis: A systematic review and meta-analysis

Objective: Cholera is a challenging ancient disease caused by Vibrio cholera (V. cholera). Antibiotics that prevent cell wall synthesis are among the first known antibiotic groups. Due to its high consumption, V. cholera has developed resistance to the majority of antibiotics in this class. Resistance to recommended antibiotics for the treatment of V. cholera has also increased. In light of the decrease in consumption of certain antibiotics in this group that inhibit cell wall synthesis and the implementation of new antibiotics, it is necessary to determine the antibiotic resistance pattern of V. cholera and to employ the most effective treatment antibiotic. Method: An comprehensive systematic search for relevant articles was conducted in PubMed, Web of Science, Scopus, and EMBASE through October 2020. Stata version 17.1 utilized the Metaprop package to execute a Freeman-Tukey double arcsine transformation in order to estimate weighted pooled proportions. Results: A total of 131 articles were included in the meta-analysis. Ampicillin was the most investigated antibiotic. The prevalence of antibiotic resistance was in order aztreonam (0%), cefepime (0%), imipenem (0%), meropenem (3%), fosfomycin (4%), ceftazidime (5%), cephalothin (7%), augmentin (8%), cefalexin (8%), ceftriaxone (9%), cefuroxime (9%), cefotaxime (15%), cefixime (37%), amoxicillin (42%), penicillin (44%), ampicillin (48%), cefoxitin (50%), cefamandole (56%), polymyxin-B (77%), carbenicillin (95%) respectively. Discussion: Aztreonam, cefepime, and imipenem are the most efficient V. cholera cell wall synthesis inhibitors. There has been an increase in resistance to antibiotics such as cephalothin, ceftriaxone, amoxicillin, and meropenem. Over the years, resistance to penicillin, ceftazidime, and cefotaxime, has decreased.

Antimicrobial resistance in Vibrio cholerae O1/O139 clinical isolates: a systematic review and meta-analysis

OBJECTIVES

Vibrio cholerae O1/O139 is responsible for cholera epidemics; that remains a huge public health menace across the globe. Furthermore, an increasing resistance rate among V. cholerae strains has been reported around the world. Therefore, the objective of this meta-analysis was to evaluate the weighted pooled resistance (WPR) rates in clinical V. cholerae O1/O139 isolates based on different years, areas, antimicrobial susceptibility testing, and resistance rates.

RESEARCH DESIGN AND METHODS

: We searched the studies in PubMed, Scopus, Embase, and Web of Science (until January 2020). Statistical analyses were conducted using STATA software (ver. 14.0).

RESULTS

: A total of 139 studies investigating 24062 V. cholerae O1/O139 isolates were analyzed. The majority of the studies originated in Asia (n=102). The WPR rates were as follows: azithromycin 1%, erythromycin 36%, ciprofloxacin 3%, cotrimoxazole 79%, doxycycline 7%, tetracycline 20%. There was increased resistance to cotrimoxazole, ciprofloxacin, and tetracycline during the 1980 to 2020 years.

CONCLUSIONS

: Temporal changes in antibiotic resistance rate found in this study demonstrated the critical continuous surveillance of antibiotic resistance. Also, ciprofloxacin, azithromycin, gentamicin, cephalexin, imipenem, ofloxacin, and norfloxacin were found to be the best antibiotics against V. cholera, with the highest and the lowest effectiveness resistance rate.

Genomic diversities of ctxB, tcpA and rstR alleles of Vibrio cholerae O139 strains isolated from Odisha, India

The genome of Vibrio cholerae O139 strains has undergone cryptic changes since its first emergence in 1992 in South India. This study aimed to determine the presence of genotypic changes marked in ctxB, tcpA and rstR genes located within the CTX prophages among the strains of V. cholerae O139 isolated from 1999 to 2017 in Odisha. Antibiotic susceptibility test was conducted on 59 V. cholerae O139 strains. A conventional PCR assay was done for ctxB gene typing followed by sequencing along with identification of rstR and tcpA gene. Pulsed-field gel electrophoresis (PFGE) was carried out to reveal clonal variations among the V. cholerae O139 strains. Among V. cholerae O139 isolates more than 60% showed resistance to ampicillin, co-trimoxazole, furazolidone, streptomycin, neomycin and nalidixic acid. The ctxB sequencing and rstR allele-specific PCR assay revealed the presence of three genotypes 1, 3 and 4 with at least one copy of CTX Calc φ in addition to CTX ET and CTX Cl prophages in V. cholerae O139 isolates. PFGE analysis revealed 13 pulsotypes with two clades having 60% similarity among V. cholerae O139 strains. The circulating V. cholerae O139 strains in Odisha showed variation in genotypes with multiple clonal expansions over the years.

Phenotypic and Genetic Heterogeneity in Vibrio cholerae O139 Isolated from Cholera Cases in Delhi, India during 2001-2006

Incidence of epidemic Vibrio cholerae serogroup O139 has declined in cholera endemic countries. However, sporadic cholera caused by V. cholerae O139 with notable genetic changes is still reported from many regions. In the present study, 42 V. cholerae O139 strains isolated from 2001 to 2006 in Delhi, India, were retrospectively analyzed to understand their phenotype and molecular characteristics. The majority of isolates were resistant to ampicillin, furazolidone and nalidixic acid. Though the integrative conjugative element was detected in all the O139 isolates, the 2004–2006 isolates remained susceptible to co-trimoxazole, chloramphenicol, and streptomycin. Cholera toxin genotype 1 was present in the majority of the O139 isolates while few had type 3 or a novel type 4. In the cholera toxin encoding gene (ctx) restriction fragment length polymorphism, the majority of the isolates harbored three copies of CTX element, of which one was truncated. In this study, the ctx was detected for the first time in the small chromosome of V. cholerae O139 and one isolate harbored 5 copies of CTX element, of which 3 were truncated. The ribotype BII pattern was found in most of the O139 isolates. Three V. cholerae O139 isolated in 2001 had a new ribotype BVIII. Pulsed-field gel electrophoresis analysis revealed clonal variation in 2001 isolates compared to the 2004–2006 isolates. Molecular changes in V. cholerae O139 have to be closely monitored as this information may help in understanding the changing genetic features of this pathogen in relation to the epidemiology of cholera.

Molecular tools in understanding the evolution of Vibrio cholerae

Vibrio cholerae, the etiological agent of cholera, has been a scourge for centuries. Cholera remains a serious health threat for developing countries and has been responsible for millions of deaths globally over the past 200 years. Identification of V. cholerae has been accomplished using a variety of methods, ranging from phenotypic strategies to DNA based molecular typing and currently whole genomic approaches. This array of methods has been adopted in epidemiological investigations, either singly or in the aggregate, and more recently for evolutionary analyses of V. cholerae. Because the new technologies have been developed at an ever increasing pace, this review of the range of fingerprinting strategies, their relative advantages and limitations, and cholera case studies was undertaken. The task was challenging, considering the vast amount of the information available. To assist the study, key references representative of several areas of research are provided with the intent to provide readers with a comprehensive view of recent advances in the molecular epidemiology of V. cholerae. Suggestions for ways to obviate many of the current limitations of typing techniques are also provided. In summary, a comparative report has been prepared that includes the range from traditional typing to whole genomic strategies.

Cholera: a great global concern

Cholera, caused by the infection of toxigenic Vibrio cholerae (V. cholerae) to humans, is a life threatening diarrheal disease with epidemic and pandemic potential. The V. cholerae, both O1 and O139 serogroups, produce a potent enterotoxin (cholera toxin) responsible for the lethal symptoms of the disease. The O1 serogroup has two biotypes (phenotypes), classical and El Tor; each of which has two major serotypes (based on antigenic responses), Ogawa and Inaba and the extremely rare Hikojima. V. cholerae O1 strains interconvert and switch between the Ogawa and Inaba serotypes. Fluid and electrolyte replacement is the mainstay of treatment of cholera patients; the severe cases require antibiotic treatment to reduce the duration of illness and replacement of fluid intake. The antibiotic therapy currently has faced difficulties due to the rapid emergence and spread of multidrug resistant V. cholerae causing several outbreaks in the globe. Currently, cholera has been becoming endemic in an increasing number of geographical areas, reflecting a failure in implementation of control measures. However, the current safe oral vaccines lower the number of resistant infections and could thus represent an effective intervention measure to control antibiotic resistance in cholera. Overall, the priorities for cholera control remain public health interventions through improved drinking water, sanitation, surveillance and access to health care facilities, and further development of safe, effective and appropriate vaccines. Thus, this review describes the facts and phenomena related to the disease cholera, which is still a great threat mainly to the developing countries, and hence a grave global concern too.

Multiresistant Vibrio cholerae non-O1/non-O139 from waters in South India: resistance patterns and virulence-associated gene profiles

From different aquatic locations in Alleppey district, Kerala, South India a number (n = 36) of multiresistant non-O1, non-O139 V. cholerae strains were isolated. Water samples were filtered through 0.22 mum membrane filters, enriched in alkaline peptone water and plated onto thiosulfate-citrate-bile salts-sucrose (TCBS) agar. The isolates were resistance to cefotaxime (50%), nalidixic acid (44.4%), streptomycin and tetracycline (41.6%), trimethoprim (38.8%), co-trimoxazole (33.3%), furazolidone (27.7%), neomycin and ofloxacin (19.4%), ciprofloxacin, norfloxacin and spectinomycin (16.6%), gentamicin (8.3%) and chloramphenicol (2.7%). To our knowledge, this is the first report from Kerala, South India on the emergence of multiple drug resistance in V. cholerae isolates belonging to serogroup other than O1 and O139. Virulence-associated gene profiling of the isolates by PCR revealed the presence of toxR (100%), rtxA (61.1%), hlyA (50%), mshA (33.3%), tcpA-acfB (13.8%) and st (2.7%) genes. The virulence gene clusters ctxA, ompU, ace, and zot were not detected. This study demonstrates the presence of a wide array of critical virulence factors in diverse strains of Vibrio cholerae non-O1/non-O139. Hence, this serogroup can no longer be ignored as an environmental reservoir of virulence genes.

Genetic analysis of CTX prophages with special reference to ctxB and rstR alleles of Vibrio cholerae O139 strains isolated from Kolkata over a decade

Chronological analysis of 125 Vibrio cholerae O139 strains isolated during 1993-2005 in Kolkata revealed the prevalence of two new genotypes of cholera toxin (CT) and novel combinations of ctxB and rstR alleles resulting in variant CTX prophages. One of the new genotypes of ctxB, which first appeared in 1996 with the re-emerged V. cholerae O139 strains that had CTX Calcutta phage, was designated as genotype 4. In 1998, another new genotype, designated as genotype 5, was detected that prevailed mostly in CTX phages with El Tor rstR. The prototype El Tor CTX phage with genotype 3 gradually disappeared in O139, and since 2002 the predominant CTX prophages in O139 are Calcutta phages with genotype 4 and El Tor phages with genotype 5. Results showed that V. cholerae O139 strains of Kolkata, isolated over a decade, harboured CTX prophages in the large chromosome having no RS1 downstream of CTX prophage. During the course of its intermittent incidence over a decade, five types of O139 strains were detected based on CT genotypes. Such abrupt genetic changes in O139 strains might not favour its continued prevalence in human cases in Kolkata, India.

Phenotypic and genotypic traits and epidemiological implication of Vibrio cholerae O1 and O139 strains in India during 2003

During 2003, Vibrio cholerae O1 Ogawa was the predominant serotype among diarrhoeal patients admitted to different hospitals in India. With the exception of 3 strains from Kolkata, none of 172 strains examined exhibited resistance to tetracycline, but 45.7 % showed reduced susceptibility to ciprofloxacin. Extensive molecular characterization using randomly amplified polymorphic DNA analysis, ribotyping and PFGE revealed that almost all the strains within a serogroup were clonally related. Along with the H pulsotype, a newly described L pulsotype of recently emerged O1 Inaba strains was detected among the O1 Ogawa strains from 2003. The striking similarity in their molecular properties and antibiograms indicated that at least certain clones of recently emerged Inaba strains from 2004 may have evolved from O1 Ogawa strains. This view was further supported by the detection of a nearly identical wbeT region among the O1 Ogawa and recently emerged Inaba strains, the latter differing only by a single point mutation. Since 2003, a hiatus in the isolation of serogroup O139 was observed and these strains share the same PFGE profiles as those isolated during 2000. Organization of tandemly arranged CTXEl, CTXCal and truncated CTXCal (devoid of ctxAB) prophages was unique among the majority of these O139 strains.

Reduction in capsular content and enhanced bacterial susceptibility to serum killing of Vibrio cholerae O139 associated with the 2002 cholera epidemic in Bangladesh

Vibrio cholerae O139 emerged in 1992 as a major cause of epidemic cholera. However, the incidence of disease due to this new serogroup subsequently decreased for almost a decade. In April 2002, there was a dramatic resurgence of V. cholerae O139 in Bangladesh. We compared the phenotypic properties of the bacterial isolates and the immunological responses in patients with disease due to V. cholerae O139 during the 2002 epidemic with those dating to the emergence of this disease in 1993 to 1995. Strains isolated from patients in the two time periods were compared with respect to capsular polysaccharide, their resistance to the bactericidal effect of serum, and their capacity to be used as target strains in complement-mediated vibriocidal assays. Phase-contrast microscopy showed that strains isolated in 2002 had less capsular material than those isolated from 1993 to 1995 (P = <0.001), a finding confirmed by electron microscopic studies. Strains isolated in 2002 were more susceptible to the bactericidal activity of serum compared to strains from 1993 to 1995 (P = 0.013). Compared to results using a standard O139 strain, a modified vibriocidal assay utilizing a 2002 strain, CIRS 134, as the target organism detected higher vibriocidal responses in both O139-infected cholera patients as well as O139 vaccine recipients. The vibriocidal assay utilizing the less encapsulated 2002 strain, CIRS 134, is a more sensitive indicator of adaptive immune responses to recent infection with V. cholerae O139. Consequently, this assay may be useful in studies of both O139-infected patients and recipients of O139 vaccines.

Reemergence of epidemic Vibrio cholerae O139, Bangladesh

During March and April 2002, a resurgence of Vibrio cholerae O139 occurred in Dhaka and adjoining areas of Bangladesh with an estimated 30,000 cases of cholera. Patients infected with O139 strains were much older than those infected with O1 strains (p<0.001). The reemerged O139 strains belong to a single ribotype corresponding to one of two ribotypes that caused the initial O139 outbreak in 1993. Unlike the strains of 1993, the recent strains are susceptible to trimethoprim, sulphamethoxazole, and streptomycin but resistant to nalidixic acid. The new O139 strains carry a copy of the Calcutta type CTX^Calc prophage in addition to the CTX^ET prophage carried by the previous strains. Thus, the O139 strains continue to evolve, and the adult population continues to be more susceptible to O139 cholera, which suggests a lack of adequate immunity against this serogroup. These findings emphasize the need for continuous monitoring of the new epidemic strains.

Amoeba-resisting bacteria and ventilator-associated pneumonia

To evaluate the role of amoeba-associated bacteria as agents of ventilator-associated pneumonia (VAP), we tested the water from an intensive care unit (ICU) every week for 6 months for such bacteria isolates; serum samples and bronchoalveolar lavage samples (BAL) were also obtained from 30 ICU patients. BAL samples were examined for amoeba-associated bacteria DNA by suicide-polymerase chain reaction, and serum samples were tested against ICU amoeba-associated bacteria. A total of 310 amoeba-associated bacteria from 10 species were isolated. Twelve of 30 serum samples seroconverted to one amoeba-associated bacterium isolated in the ICU, mainly Legionella anisa and Bosea massiliensis, the most common isolates from water (p=0.021). Amoeba-associated bacteria DNA was detected in BAL samples from two patients whose samples later seroconverted. Seroconversion was significantly associated with VAP and systemic inflammatory response syndrome, especially in patients for whom no etiologic agent was found by usual microbiologic investigations. Amoeba-associated bacteria might be a cause of VAP in ICUs, especially when microbiologic investigations are negative.

Vibrio cholerae O139 Bengal: odyssey of a fortuitous variant

Vibrio cholerae O139, the new serogroup associated with epidemic cholera, came into being in the second half of the year 1992 in an explosive fashion and was responsible for several outbreaks in India and other neighbouring countries. This was an unprecedented event in the history of cholera and the genesis of the O139 serogroup was, at that time, thought to be the beginning of the next or the eighth pandemic of cholera. However, with the passage of time, the O1 serogroup of the El Tor biotype again reappeared and displaced the O139 serogroup on the Indian subcontinent, and there was a feeling among cholera workers that the appearance of this new serogroup may have been a one-time event. The resurgence of the O139 serogroup in September 1996 in Calcutta and the coexistence of both the O1 and O139 serogroups in much of the cholera endemic areas in India and elsewhere, suggested that the O139 serogroup has come to stay and is a permanent entity to contend with in the coming years. During the past 10 years, intensive work on all aspects of the O139 serogroup was carried out by cholera researchers around the world. The salient findings on this serogroup over the past 10 years pertinent to its prevalence, clinico-epidemiological features, virulence-associated genes, rapid screening and identification, molecular epidemiology, and vaccine developments have been highlighted.

Molecular characterization of Vibrio cholerae O139 bengal isolated from water and the aquatic plant Eichhornia crassipes in the River Ganga, Varanasi, India

A collection of ten strains of Vibrio cholerae O139, comprising six isolates from Eichhornia crassipes, two from water of the River Ganga, and one each from a well and a hand pump, were characterized. All the strains carried the CTX genetic element (ctxA, zot, and ace) except for the st gene and carried structural and regulatory genes for toxin-coregulated pilus (tcpA, tcpI, and toxR), adherence factor (ompU), and accessory colonization factor (acfB); all produced cholera toxin (CT). These strains were resistant to trimethoprim, sulfamethoxazole, streptomycin, and to the vibriostatic agent pteridine. Results obtained by ribotyping and enterobacterial repetitive intergenic consensus sequence-PCR fingerprint analysis indicate that multiple clones of toxigenic-pathogenic V. cholerae O139 were present in the aquatic environment.

Emergence and evolution of Vibrio cholerae O139

The emergence of Vibrio cholerae O139 Bengal during 1992-1993 was associated with large epidemics of cholera in India and Bangladesh and, initially, with a total displacement of the existing V. cholerae O1 strains. However, the O1 strains reemerged in 1994 and initiated a series of disappearance and reemergence of either of the two serogroups that was associated with temporal genetic and phenotypic changes sustained by the strains. Since the initial emergence of the O139 vibrios, new variants of the pathogen derived from multiple progenitors have been isolated and characterized. The clinical and epidemiological characteristics of these strains have been studied. Rapid genetic reassortment in O139 strains appears to be a response to the changing epidemiology of V. cholerae O1 and also a strategy for persistence in competition with strains of the O1 serogroup. The emergence of V. cholerae O139 has provided a unique opportunity to witness genetic changes in V. cholerae that may be associated with displacement of an existing serogroup by a newly emerging one and, thus, provide new insights into the epidemiology of cholera. The genetic changes and natural selection involving both environmental and host factors are likely to influence profoundly the genetics, epidemiology, and evolution of toxigenic V. cholerae, not only in the Ganges Delta region of India and Bangladesh, but also in other areas of endemic and epidemic cholera.

Characterization of a toxigenic Vibrio cholerae O139 strain belonging to a new ribotype and isolated from a diarrheal patient

We characterized a Vibrio cholerae O139 strain isolated from a diarrheal patient admitted to Taluk Hospital, Cherthala, Alleppey, Kerala, India, on 9 June 2000. The V. cholerae O139 strain possesses the core of the CTX genetic element, colonization toxin-coregulated pilus, the adherence outer membrane protein, and the central regulatory protein encoded by toxR and produces cholera toxin (200 pg/ml). We provide molecular evidence showing that toxigenic V. cholerae O139 strain ALO95 belongs to a distinct genotype characterized by a unique ribotype designated B-VII and has a unique enterobacterial repetitive intergenic consensus sequence PCR fingerprint profile designated E-V.

Escalating association of Vibrio cholerae O139 with cholera outbreaks in India

Between December 1999 and December 2000, teams from the National Institute of Cholera and Enteric Diseases, Calcutta, India, examined eight outbreaks of cholera, which occurred in different parts of the country distant from each other. In two of these outbreaks each, only V. cholerae O1 biotype ElTor or V. cholerae O139 could be isolated, while in the remaining four outbreaks, both O1 and O139 were isolated. The interesting feature is the escalating association of V. cholerae O139 with outbreaks of cholera; two of the most recent outbreaks, one in Calcutta and one in Orissa, were caused exclusively by O139. The O139 strains from the six different outbreaks were genotypically closely related. These trends indicate a shift in the outbreak propensity of V. cholerae O139.

Allelic diversity and population structure in Vibrio cholerae O139 Bengal based on nucleotide sequence analysis

Comparative analysis of gene fragments of six housekeeping loci, distributed around the two chromosomes of Vibrio cholerae, has been carried out for a collection of 29 V. cholerae O139 Bengal strains isolated from India during the first epidemic period (1992 to 1993). A toxigenic O1 ElTor strain from the seventh pandemic and an environmental non-O1/non-O139 strain were also included in this study. All loci studied were polymorphic, with a small number of polymorphic sites in the sequenced fragments. The genetic diversity determined for our O139 population is concordant with a previous multilocus enzyme electrophoresis study in which we analyzed the same V. cholerae O139 strains. In both studies we have found a higher genetic diversity than reported previously in other molecular studies. The results of the present work showed that O139 strains clustered in several lineages of the dendrogram generated from the matrix of allelic mismatches between the different genotypes, a finding which does not support the hypothesis previously reported that the O139 serogroup is a unique clone. The statistical analysis performed in the V. cholerae O139 isolates suggested a clonal population structure. Moreover, the application of the Sawyer's test and split decomposition to detect intragenic recombination in the sequenced gene fragments did not indicate the existence of recombination in our O139 population.

Recent developments in cholera

Cholera continues to be an important public health problem among many poorer communities in Africa, Asia and South America, despite the bacteriology and epidemiology of the disease having been described over a century ago. Molecular techniques have enabled current researchers to gain new insights into pathogenicity, into the relationships between environmental and clinical strains, and into new strategies for vaccine development. The description of non-culturable 'dormant' strains in the environment and the effect of environmental factors on toxin gene regulation provide valuable clues to the ecology of the disease. Disease management continues to be based on urgent and appropriate rehydration, and recent community studies emphasize the need for effective local health services to provide this if case fatality rates are to remain low. While antimicrobial agents may play a role in case management and prophylaxis, the increasing prevalence of antimicrobial resistance must be addressed. New vaccine candidates, based on a molecular understanding of pathogenicity, provide scope for improved strategies for disease prevention, though the appropriate public health context for their use has not been determined. This review summarizes activities in these fields of cholera research and considers the continuing global problem of the disease.

Concomitant infection of enterotoxigenic Escherichia coli in an outbreak of cholera caused by Vibrio cholerae O1 and O139 in Ahmedabad, India

In Ahmedabad, a major city in the state of Gujarat, India, an outbreak of acute secretory diarrhea caused by Vibrio cholerae O1 Ogawa El Tor, V. cholerae O139, and multiple serotypes of enterotoxigenic Escherichia coli (ETEC) occurred in January 2000. All of the representative V. cholerae O1 and O139 isolates examined harbored the ctxA gene (encoding the A subunit of cholera toxin) and the El Tor variant of the tcpA gene (encoding toxin-coregulated pilus). ETEC isolates of different serotypes were positive for the elt gene, encoding heat-labile enterotoxin. To further understand the molecular characteristics of the pathogens, representative isolates were examined by ribotyping and pulsed-field gel electrophoresis (PFGE). Ribotyping showed that the isolates of V. cholerae O1 Ogawa exhibited a pattern identical to that of the prevailing clone of O1 in areas where cholera is endemic in India, and all of the O139 isolates were identical to the BII clone of V. cholerae O139. PFGE of the representative O1 Ogawa isolates exhibited an identical pattern, comparable to the H pattern of the new clone of O1 reported in Calcutta, India. PFGE analysis of the V. cholerae O139 isolates showed identical patterns, but these differed from the PFGE patterns of O139 isolates reported during 1992 to 1997 in Calcutta. ETEC isolates showed genetic heterogeneity among isolates belonging to the same serotype, although the identical PFGE pattern was also observed among ETEC isolates of different serotypes. Antibiograms of the isolates were unusual, because all of the O139 isolates were resistant to nalidixic acid. Likewise, all of the E. coli isolates showed resistance to ciprofloxacin, norfloxacin, and nalidixic acid. This is a unique outbreak, and we believe that it is the first in which V. cholerae and ETEC were concomitantly involved.