Goutam Chowdhury

• PhD
• Scientist D at Collaborative Research Center of Okayama University for Infectious Diseases in India, National Institute of Cholera and Enteric Diseases

Campylobacter species are the most common pathogens responsible for foodborne gastroenteritis worldwide. India is a region with frequent diarrheal infections and a high level of Campylobacter infection incidence, but the detailed genomic information is limited. This study aimed to characterize 112 isolates of Campylobacter from diarrhea patients at...

Background Traditional and fermented foods are widely consumed by the ethnic population of Northeast India. These foods are not only very nutritious, easily available, and reasonably priced, but also boost immunity and protect from various seasonal infections and have been reported through several investigations. However, pathogens transmitted by t...

Background: Cholera cases have increased globally across the Eastern Mediterranean, Africa, Southeast Asia, and parts of Europe since early 2024. This study aims to identify cholera hotspots and understand the spatial distribution of cholera in Kolkata and surrounding regions, a key cholera reservoir. Additionally, we examine sociodemographic facto...

Campylobacter and invasive non-typhoidal Salmonella (iNTS) are among the most common causative agents of gastroenteritis worldwide. As of now, no single combination licensed vaccine is available for public health use against both iNTS and Campylobacter species. Outer-membrane vesicles (OMVs) are nanoscale proteoliposomes released from the surface o...

Introduction An acute gastrointestinal illness outbreak was reported in a higher educational institution among students and faculties in East Sikkim, India, from January to February 2023. The investigation was conducted to identify the source of the infection and causative pathogens and prevent the spread of the outbreak. Methods We defined a case...

Food and waterborne outbreaks are a neglected public health problem in India. However, it is important to identify the source of infection and the causative pathogen to curb the outbreak quickly and minimize mortality and morbidity. A retrospective descriptive study was conducted with a line list of 130 diarrheal cases. Epidemiological investigatio...

The diagnostic assays currently used to detect Shigella spp. (Shigella) and enterotoxigenic Escherichia coli (ETEC) are complex or elaborate which make them difficult to apply in resource poor settings where these diseases are endemic. The simple and rapid nucleic acid amplification-based assay "Rapid LAMP-based Diagnostic Test (RLDT)" was evaluate...

Campylobacter and non-typhoidal Salmonella (NTS) are among the most common causative agents of gastroenteritis worldwide. As of now, no single combination licensed vaccine is available for public health use against both NTS and Campylobacter species. Outer-membrane vesicles (OMVs) are nanoscale proteoliposomes released from the surface of gram-nega...

Background The primary aim of this study was to investigate the occurrence, characteristics, and antimicrobial resistance patterns of various Shigella serogroups isolated from patients with acute diarrhea of the Infectious Diseases Hospital in Kolkata from 2011–2019. Principal findings During the study period, Shigella isolates were tested for the...

Foodborne gastroenteritis outbreaks owing to Salmonella enterica serovar Weltevreden (Salmonella Weltevreden) represent a significant global public health problem. In the past two decades, Salmonella Weltevreden has emerged as a dominant foodborne pathogen, especially in South-East Asian countries. This report describes a community foodborne outbre...

We isolated a Vibrio fluvialis strain (IDH5335) from a stool sample collected from a patient with diarrhea. In this announcement, we report the complete genomic sequence of this organism, which was obtained by combining Illumina and Oxford Nanopore sequencing data.

Diarrhoeagenic Escherichia coli (DEC) pathotypes are one of the major causative agents of diarrhoea induced childhood morbidity and mortality in developing countries. Licensed vaccines providing broad spectrum protection against DEC mediated infections are not available. Outer membrane vesicles (OMVs) are microvesicles released by gram-negative bac...

The diagnostic assays currently used to detect Shigella spp. (Shigella) and enterotoxigenic Escherichia coli (ETEC) are complex or elaborate which make them difficult to apply in resource poor settings where these diseases are endemic. The simple and rapid nucleic acid amplification-based assay "Rapid LAMP-based Diagnostic Test (RLDT)" was evaluate...

Aim: To characterize extensively drug-resistant Pseudomonas aeruginosa from a patient with diarrhea. Materials & methods: Antimicrobial susceptibility was tested by the disk diffusion method. The P. aeruginosa genome was sequenced to identify virulence, antibiotic resistance and prophages encoding genes. Results: P. aeruginosa had a wide spectrum o...

Many patients with cholera emerge in Kolkata, India throughout the year. Such emergency indicates that cholera toxin-producing Vibrio cholerae O1 (toxigenic V. cholerae O1) are widespread in Kolkata. This suggests that the suitable conditions for replication of toxigenic V. cholerae O1 is provided in Kolkata. In previous studies, we found that the...

Background: Non-typhoidal Salmonella (NTS) is one of the four critical worldwide reasons for diarrhoeal infections and causes a noted zoonotic infection termed non-typhoidal salmonellosis. Non-typhoidal salmonellosis generally causes self-limited gastroenteritis, whereas in immunocompromised conditions can result in invasive infections. Aim and Obj...

Antimicrobial resistance (AMR) in bacteria is an important global health problem affecting humans, animals, and the environment. AMR is considered as one of the major components in the “global one health”. Misuse/overuse of antibiotics in any one of the segments can impact the integrity of the others. In the presence of antibiotic selective pressur...

We examined the stools of 23 patients in Kolkata, who were diagnosed as cholera patients because Vibrio cholerae O1 was detected from their stools by culturing methods, and further explored by metagenomic sequencing analysis. Subsequently, the presence of the gene encoding A subunit of cholera toxin (ctxA) and the cholera toxin (CT) level in these...

Aims: The present study aimed to document the comparative analysis of differential hyper-virulent features of Vibrio cholerae O1 strains isolated during 2018 from cholera endemic regions in Gujarat and Maharashtra (Western India) and West Bengal (Eastern India). Methods and results: A total of 87 V. cholerae O1 clinical strains from Western Indi...

Cholera is a life-threatening infectious disease that remains an important public health issue in several low and middle-income countries. In 1992, a newly identified O139 Vibrio cholerae temporarily displaced the O1 serogroup. No study has been able to answer why the potential eighth cholera pandemic (8CP) causing V. cholerae O139 emerged so succe...

Purpose: The multidrug resistance Enterobacteriaceae cause many serious infections resulting in prolonged hospitalization, increased treatment charges and mortality rate. In this study, we characterized bla NDM-5-positive multidrug resistance commensal Escherichia coli (CE) isolated from diarrheal patients in Kolkata, India. Methods: Three CE st...

Acinetobacter baumannii (A. baumannii) is a leading cause of nosocomial infections as this pathogen has certain attributes that facilitate the subversion of natural defenses of the human body. A. baumannii acquires antibiotic resistance determinants easily and can thrive on both biotic and abiotic surfaces. Different resistance mechanisms or determ...

Aims: This study analyzes the prevalence and antimicrobial resistance (AMR) of major diarrheagenic Escherichia coli (DEC) pathotypes detected in hospitalized diarrheal patients in Kolkata, India, during 2012-2019. Methods and results: A total of 8,891 stool samples were collected from the Infectious Diseases Hospital, Kolkata and screened for th...

Understanding the global burden of enterotoxigenic E. coli (ETEC) and Shigella diarrhea as well as estimating the cost effectiveness of vaccines to control these two significant pathogens have been hindered by the lack of a diagnostic test that is rapid, simple, sensitive, and can be applied to the endemic countries. We previously developed a simpl...

The human gastrointestinal tract (GIT) is one of the most complex environments in the body that is colonized by trillions of microorganisms, including viruses, archaea, bacteria, fungi and parasites. Among these, bacteria are considered to be the major inhabitants. The human gut microbiota plays an important role in healthy individuals and are intr...

Vibrio parahaemolyticus (Vp) is an aquatic Gram-negative bacterium that may infect humans and cause gastroenteritis and wound infections. The first pandemic of Vp associated infection was caused by the serovar O3:K6 and epidemics caused by the other serovars are increasingly reported. The two major virulence factors, thermostable direct hemolysin (...

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...

Vibrio parahaemolyticus is one of the leading causes of diarrhoea and gastroenteritis in human on consumption of raw or insufficiently cooked seafood. This study was aimed at isolating and characterizing the pathogenic and pandemic V. parahaemolyticus from oysters (n = 90) in coastal parts of West Bengal, India; their antibiotic resistance and pote...

Aim: Enterotoxigenic Escherichia coli (ETEC) is one of the most widely recognized diarrheal pathogens in developing countries. Advancement of ETEC vaccine development depends on the antigenic determinants of the ETEC isolates from a particular geographical region. So, the aim here was to comprehend the distribution of virulence determinants of the...

Background Cholera, an acute diarrheal disease is a major public health problem in many developing countries. Several rapid diagnostic tests (RDT) are available for the detection of cholera, but their efficacies are not compared in an endemic setting. In this study, we have compared the specificity and sensitivity of three RDT kits for the detectio...

Phages, such as those infecting Bacteroides spp., have been proven to be reliable indicators of human fecal contamination in microbial source tracking (MST) studies, and the efficacy of these MST markers found to vary geographically. This study reports the application and evaluation of candidate MST methods (phages infecting previously isolated B....

Background: Carbapenem are the last-line antibiotic, defence against Gram-negative extended spectrum ß-lactamases producers (ESBLs). Carbapenem resistance Enterobacteriaceae especially Carbapenem resistant-Klebsiella pneumoniae (CR-KP) is recognized as one of the well-known public health problem, which is increasingly being reported around the worl...

Vibrio cholerae serogroup O1 is responsible for epidemic and pandemic cholera and remains a global public health threat. This organism has been well established as a resident flora of the aquatic environment that alters its phenotypic and genotypic attributes for better adaptation to the environment. To reveal the diversity of clinical isolates of...

The human gut harbours a multifaceted and dynamic population of microorganisms, which affect human homeostasis and health. Robust network among gut microbes plays an important role in human health and disease by influencing immunity, nutrition and pathogenesis. The gut microbes are frequently exposed to antibiotics, which are used to prevent and/or...

It has been well known that Vibrio cholerae inhabit in environmental water. As many patients infected with cholera toxin-producing V. cholerae O1 (toxigenic V. cholerae O1) emerge in Kolkata, India, it has been thought that toxigenic V. cholerae O1 is easily detected in environmental water in Kolkata. However, we could not isolate toxigenic V. chol...

S Non‐O1/non‐O139 nontoxigenic Vibrio cholerae associated with cholera‐like diarrhea has been reported in Kolkata, India. However, the property involved in the pathogenicity of these strains has remained unclear. We examined the character of 25 non‐O1/non‐O139 nontoxigenic V. cholerae isolated during 8 years from 2007 to 2014 in Kolkata. Determinat...

Non-typhoidal Salmonella (NTS) is an important cause of acute gastroenteritis in children. The study was undertaken to determine the isolation rate, serovar prevalence, antimicrobial resistance (AMR) profiles, and molecular subtypes of NTS from a hospital-based diarrheal disease surveillance in Kolkata, India. Rectal swabs were collected from child...

Non-typhoidal salmonellae (NTS) are a major cause of acute diarrhea with characteristic multidrug resistance. In a hospital based study, 81 NTS were isolated and tested for serotypes and antimicrobial resistance (AMR). Salmonella enterica isolates were classified into 7 different typable serovars and 19 (23%) isolates remained untypable. The most c...

It has been regarded that Vibrio cholerae O1 inhabit in environmental water. As many cholera patients emerge in Kolkata, it has been thought that V. cholerae O1 is easily detected in environmental water in Kolkata. However, the detection of V. cholerae O1 is rare, though other V. cholerae (NAG Vibrio) is constantly detected. To clear the reason for...

The self-transferring integrative and conjugative elements (ICEs) are large genomic segments carrying several bacterial adaptive functions including antimicrobial resistance (AMR). SXT/R391 family is one of the ICEs extensively studied in cholera-causing pathogen Vibrio cholerae. The genetic characteristics of ICE-SXT/R391 in V. cholerae are dynami...

The progressive rise in antibiotic resistance among enteric pathogens in developing countries is becoming a big concern. India is one of the largest consumers of antibiotics, and their use is not well regulated. V. fluvialis is increasingly recognized as an emerging diarrheal pathogen of public health importance. Here we report the emergence of azi...

The role of Vibrio parahaemolyticus in causing diarrhoeal disease is well known. However, phenotypic and genetic traits of this pathogen isolated from diverse sources have not been investigated in detail. In this study, we have screened samples from diarrhoeal cases (2603), brackish water fish (301) and aquatic environments (115) and identified V....

Background and Objectives Non-typhoidal Salmonellosis, a zoonotic infection associated with acute gastroenteritis is caused by non-typhoidal salmonellae (NTS). The study was carried out to determine the prevalence of NTS serovars and their antimicrobial resistance along with the presence of the virulence gene (invA gene) in poultry samples. Materi...

Background To analyze the molecular epidemiology and to compare between the major methicillin resistant Staphylococcus aureus biotypes for association with patient characteristics who had an implant for closed fracture and developed early post-operative wound infections (POWI) in a tertiary care hospital of India. Methods Pulsed-field gel electrop...

The Infectious Diseases and Beliaghata General Hospital, Kolkata, India witnessed a sudden increase in admissions of diarrhoea cases during the first 2 weeks of August 2015 following heavy rainfall. This prompted us to investigate the event. Cases were recruited through hospital-based surveillance along with the collection of socio-demographic char...

Introduction Vibrio cholerae O1 strains are responsible for pandemics of cholera and major epidemics in the world. All the remaining V. cholerae non-O1/non-O139 strains are less virulent and are responsible for sporadic cases of gastroenteritis. These non-O1/non-O139 serogroups have more than 200 somatic antigens, and mostly lack cholera toxin and...

Salmonella enterica serovar Typhimurium (S. Typhimurium) is a common serovar associated with non-typhoidal salmonellosis globally. However, there is insufficient data on molecular characterization of S. Typhimurium isolates from India. This study was undertaken to determine the antimicrobial resistance (AMR), plasmid, virulence profiles and molecul...

Medical history of patients from whom S. Typhimurium were recovered. (DOCX)

Vibrio cholerae strains producing cholera toxin (CT) and toxin co-regulated pilus (TCP) and belonging to O1 and O139 serogroups are responsible for cholera. However, non-CT producing V. cholerae from non-O1/non-O139 serogroups have been increasingly isolated from diarrheal stools and extra-intestinal infections. In this study, we have developed a m...

Acute diarrheal disease is a major health problem and second most common cause of death in children under five years of age. Conventional diagnostic methods are laborious, time consuming and occasionally inaccurate. We examined SYBR-Green real-time PCR for the detection of ten uncommon bacterial pathogens using fecal specimens from acute diarrheal...

Salmonella enterica subsp. enterica serotype Typhimurium sequence type 313 (ST313) is most commonly associated with invasive nontyphoidal Salmonella disease in Africa among patients with HIV infection and malignancy. Here, we report a draft genome sequence of S. Typhimurium ST313, isolated from an elderly immunosuppressed patient from India with no...

Aims: Development of an effective vaccine against enterotoxigenic Escherichia coli (ETEC) is largely dependent on the conscientious understanding of different virulence associated factors from diverse geographical areas. So, the objective of this study is to elucidate the distribution of enterotoxins, CF and NCVF in clinical ETEC strains isolated...

Purpose: Two natural epidemic biotypes of Vibrio cholerae O1, classical and El Tor, exhibit different patterns of sensitivity against the antimicrobial peptide polymyxin B. This difference in sensitivity has been one of the major markers in biotype classification system for several decades. A recent report regarding the emergence of polymyxin B-se...

A foodborne acute gastroenteritis outbreak due to Shigella sonnei infection occurred in a household after having food in a housewarming party of Pakapol Village, South 24 Parganas District of West Bengal, an Indian state in November 2016. Here we report, the epidemiological and microbiological findings of this outbreak. Thirty-four people attended...

Dendrogram of XbaI-digested pulsed-field gel electrophoresis profiles of the clinical isolates of Shigella dysenteriae isolates. Scale bar indicates degree of similarity.

1% agarose gel analysis of plasmid DNA profile of S. dysenteriae and S. boydii isolates (A); S. flexneri isolates (B); S. sonnei isolates (C). Marker positions have been indicated on left. Abbreviations: S. dysenteriae, Shigella dysenteriae; S. boydii, Shigella boydii, S. flexneri, Shigella flexneri; S. sonnei, Shigella sonnei.

Dendrogram of XbaI-digested pulsed-field gel electrophoresis profiles of the clinical isolates of Shigella boydii isolates. Scale bar indicates degree of similarity.

To understand the genetic basis of high drug resistance in Shigella, 95 clinical isolates of Shigella spp. (2001–2010) were obtained from the Infectious Diseases Hospital, Kolkata, India. Ninety-three isolates were resistant to three or more antibiotics. Resistance to nalidixic acid, trimethoprim, streptomycin, and co-trimoxazole was most common in...

Objective: Recurrent Clostridium difficile infection (CDI) and the emergence of strains with reduced susceptibility to metronidazole and vancomycinwarrants alternative therapy. Hence, we tested the potential efficacy of the natural compound berberine hydrochloride (BBRHCl) against toxigenicC. difficile.Methods: Three representative polymerase chain...

Clostridium perfringens is one of the most important globally recognised gastroenteric pathogen in humans as well as animals. The present study was aimed to know the similarities/divergence among C. perfringens type A isolates of human and animal origin using the pulsed-field gel electrophoresis (PFGE) as a molecular tool. The enterotoxic isolates...

Wave upon wave of disease The cholera pathogen, Vibrio cholerae , is considered to be ubiquitous in water systems, making the design of eradication measures apparently fruitless. Nevertheless, local and global Vibrio populations remain distinct. Now, Weill et al. and Domman et al. show that a surprising diversity between continents has been establi...

Vibrio cholerae O1 is the etiological agent of the severe diarrheal disease cholera. The bacterium has recently been causing outbreaks in Haiti with catastrophic effects. Numerous mutations have been reported in V. cholerae O1 strains associated with the Haitian outbreak. These mutations encompass among other the genes encoding virulence factors su...

The study was aimed to characterize, and determine antibiogram of C. perfringens type A isolated from the feces of human and animal diarrhoeal cases, as well as healthy animals, meat of pigs and goats, gills and intestine of fish and samples from fish pond. A total of 460 samples, including human diarrhoeal cases (n = 130); diarrhoeal cases of pig...

Cholera is an acute diarrheal disease and a major public health problem in many developing countries in Asia, Africa, and Latin America. Since the Bay of Bengal is considered the epicenter for the seventh cholera pandemic, it is important to understand the genetic dynamism of Vibrio cholerae from Kolkata, as a representative of the Bengal region. W...

Characterization of V. cholerae O1 clinical isolates in Kolkata. (XLSX)

Genetic organization of VSP-IIB and VSP-IIC variants. Arrows represented ORF according to the annotation of V. cholerae N16961. (TIF)

Temporal shift of VSP-II type distribution in Kolkata, India from 2007 to 2014. (TIF)

List of genomes from public databases. (XLSX)

Carbapenems have been used for many years to treat severe nosocomial Enterobacteriaceae infections. The spread of resistance to these drugs among other bacterial families is an emerging problem worldwide, mostly caused by New Delhi metallo-β-lactamase (NDM-1). We screened for the prevalence of NDM-1-expressing enteric pathogens from hospitalized pa...

Vibrio cholerae causes cholera outbreaks in endemic regions where the water quality and sanitation facilities remain poor. Apart from biotype and serotype changes,V. cholerae undergoes phase variation,which results in the generation of two morphologically different variants termed smooth and rugose. In this study,12 rugose (R-VC) and 6 smooth (S-VC...

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 understa...

Vibrio parahaemolyticus is the leading cause of seafood-related gastroenteritis. Here, we report the draft genome sequence of a trh + strain, V. parahaemolyticus K23, isolated from seafood. The sequence will be useful for comparative analysis between environmental and clinical isolates of V. parahaemolyticus .

Vibrio cholerae is an aerobic, sucrose fermentative Gram-negative bacterium that generally prevails in the environment. Pathogenic V. cholerae is well-known as causative agent of acute diarrhea. Apart from enteric infections, V. cholerae may also cause other diseases. However, their role in causing extraintestinal infections is not fully known as i...

To the Editor: The epidemiology of cholera, especially in Africa and Asia, has periodically changed in subtle ways (1). The recent cholera epidemic in Haiti, a Caribbean country with no cholera cases in decades, affected >500,000 persons, caused ≈8,000 deaths, and brought this illness to the forefront of Haitian public health concerns (2,3). This l...

A carbapenem resistant Salmonella enterica serovar Senftenberg isolate BCH 2406 was isolated from a diarrheal child attending an outpatient unit of B.C. Roy Hospital in Kolkata, India. This isolate was positive for the blaNDM-1 in the PCR assay, which was confirmed by amplicon sequencing. Except for tetracycline, this isolate was resistant to all t...

New β-lactamases with ever-broadening substrate specificity are disseminating rapidly all over the world. In the recent years, extent of resistance of human pathogens to β-lactam antibiotics is increasing due to the emergence of "new" carbapenemase-producers. New Delhi metallo-β-lactamase (NDM) is the latest carbapenemasc, detected for the first ti...

Cholera, a disease caused by Vibrio cholerae O1 and O139 remains an important public health problem globally. In the last decade, Kenya has experienced a steady increase of cholera cases. In 2009 alone, 11,769 cases were reported to the Ministry of Public Health and Sanitation. This study sought to describe the phenotypic characteristics of the iso...

Background: A live oral cholera vaccine VA 1.4 developed from a non-toxigenic Vibrio cholerae O1 El Tor strain using ctxB gene insertion was further developed into a clinical product following cGMP and was evaluated in a double-blind randomized placebo controlled parallel group two arm trial with allocation ratio of 1∶1 for safety and immunogenici...

An outbreak of cholera struck Bihar, an Indian state, in August 2008 following a massive flood. Here we report the phenotypic and genotypic characteristics of Vibrio cholerae strains isolated from patients with diarrhea. Rectal swabs were obtained from patients with diarrhea who were admitted to medical camps or the hospital, and the strains were b...

Vibrio fluvialis is a pathogen commonly found in coastal environs. Considering recent increase in numbers of diarrheal outbreaks and sporadic extraintestinal cases, V. fluvialis has been considered as an emerging pathogen. Though this pathogen can be easily isolated by existing culture methods, its identification is still a challenging problem due...

Abstract Salmonella enterica serovar Weltevreden and Vibrio fluvialis were identified as etiological agents of a foodborne gastroenteritis outbreak after an Iftar feast in North Dumdum. Of the 278 cases admitted to the Infectious Diseases Hospital, Kolkata, 44 stool samples were tested for the enteric pathogens. Six were positive for Salmonella Wel...

Abstract Strains of the enteric pathogen Vibrio parahaemolyticus harboring the thermostable hemolysin (TDH) encoding gene tdh is known to cause epidemic and pandemic diarrhea. In industrialized countries, this pathogen causes sporadic or outbreaks of diarrheal illness associated with consumption of raw or improperly cooked seafood. This report desc...

We identified 281 Vibrio cholerae non-O1, non-O139 strains from patients with diarrhea in Kolkata, India. Cholera-like diarrhea was the major symptom (66.0%); some patients (20.3%) had severe dehydration. These strains lacked the ctxA gene but many had hlyA, rtxA, and rtxC genes. Pulsed-field gel electrophoresis showed no genetic link among strains...

Analysis of 1,180 diarrheal stool samples in Zanzibar detected 247 Vibrio cholerae O1, Ogawa strains in 2009. Phenotypic traits and PCR-based detection of rstR, rtxC, and tcpA alleles showed that they belonged to the El Tor biotype. Genetic analysis of ctxB of these strains revealed that they were classical type, and production of classical cholera...

Cholera is endemic to many countries. Recent major outbreaks of cholera have prompted World Health Organization to recommend oral cholera vaccination as a public-health strategy. Variation in percentage of seroconversion upon cholera vaccination has been recorded across populations. Vaccine-induced responses are influenced by host genetic differenc...