Altered Molecular Attributes and Antimicrobial Resistance Patterns of Vibrio cholerae O1 El Tor Strains Isolated from the Cholera Endemic Regions of India

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 India and 48 from Eastern India were analyzed for a number of biotypic and genotypic features followed by antimicrobial resistance (AMR) profile. A novel PCR was designed to detect a large fragment deletion in the Vibrio seventh pandemic island II (VSP-II) genomic region, which is a significant genetic feature of the V. cholerae strains that has caused Yemen cholera outbreak. All the strains from Western India were belong to the Ogawa serotype, polymyxin B-sensitive, hemolytic, had a deletion in VSP-II (VSP-IIC) region and carried Haitian genetic alleles of ctxB, tcpA and rtxA. Conversely, 14.6% (7/48) of the strains from Eastern India belonged to the Inaba serotype, polymyxin B-resistant, non-hemolytic, harbored VSP-II other than VSP-IIC type, classical ctxB, Haitian tcpA and El Tor rtxA alleles. Resistance to tetracycline and chloramphenicol has been observed in strains from both the regions.

CONCLUSIONS

This study showed hyper-virulent, polymyxin B-sensitive epidemic causing strains in India along with the strains with polymyxin B-resistant and non-hemolytic traits that may spread and cause serious disease outcome in future.

SIGNIFICANCE AND IMPACT OF THE STUDY

The outcomes of this study can help to improve the understanding of the hyper-pathogenic property of recently circulating pandemic V. cholerae strains in India. A special attention is also needed on the monitoring of AMR surveillance because V. cholerae strains are losing susceptibility to many antibiotics used as a second line of defense in the treatment of cholera.

Characterization of diarrheagenic Escherichia coli with special reference to antimicrobial resistance isolated from hospitalised diarrheal patients in Kolkata (2012-2019), India

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 the presence of enteric pathogens. Multiplex-PCR identified the presence of DEC in 7.8% of the samples, in which ETEC was most common (47.7%) followed by EAEC (38.4%) and EPEC (13.9%). About 54% cases were due to sole DEC infections. Majority of the mixed DEC infections was caused by the Vibrio spp. (19.1%) followed by Rotavirus (14.1%) and Campylobacter spp. (8.4%). ETEC and EAEC were associated significantly with diarrhea in children <5 years of age, whereas EPEC and also ETEC were prevalent in patients aged between 5 and 14 years. AMR profile showed high prevalence of multidrug resistance (MDR) among DEC (56.9%) in which 9% were resistant to antibiotics of six different antimicrobial classes. Screening of the AMR conferring genes of DEC showed the presence of bla_CTX-M3 (30.2%) in highest number followed by bla_TEM (27.5%), tetB (18%), sul2 (12.6%), strA (11.8%), aadA1 (9.8%), bla_OXA-1 (9%), dfrA1 (1.6%) and bla_SHV (1.2%).

CONCLUSIONS

These findings highlighted the high prevalence of MDR in major DEC pathotypes that could be considered as the leading etiologic bacterial agent responsible for diarrhea and suggests a significant public health threat.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results of this study can help to improve the understanding of the epidemiology of DEC infections in patients with diarrhea. Monitoring of AMR surveillance needs special attention because the DEC isolates were highly resistant to commonly used antimicrobials in the treatment of diarrhea.

Deciphering the possible role of ctxB7 allele on higher production of cholera toxin by Haitian variant Vibrio cholerae O1

Cholera continues to be an important public health concern in developing countries where proper hygiene and sanitation are compromised. This severe diarrheal disease is caused by the Gram-negative pathogen Vibrio cholerae belonging to serogroups O1 and O139. Cholera toxin (CT) is the prime virulence factor and is directly responsible for the disease manifestation. The ctxB gene encodes cholera toxin B subunit (CTB) whereas the A subunit (CTA) is the product of ctxA gene. Enzymatic action of CT depends on binding of B pentamers to the lipid-based receptor ganglioside GM1. In recent years, emergence of V. cholerae Haitian variant strains with ctxB7 allele and their rapid spread throughout the globe has been linked to various cholera outbreaks in Africa and Asia. These strains produce classical type (WT) CTB except for an additional mutation in the signal sequence region where an asparagine (N) residue replaces a histidine (H) at the 20th amino acid position (H20N) of CTB precursor (pre-CTB). Here we report that Haitian variant V. cholerae O1 strains isolated in Kolkata produced higher amount of CT compared to contemporary O1 El Tor variant strains under in vitro virulence inducing conditions. We observed that the ctxB7 allele, itself plays a pivotal role in higher CT production. Based on our in silico analysis, we hypothesized that higher accumulation of toxin subunits from ctxB7 allele might be attributed to the structural alteration at the CTB signal peptide region of pre-H20N CTB. Overall, this study provides plausible explanation regarding the hypertoxigenic phenotype of the Haitian variant strains which have spread globally, possibly through positive selection for increased pathogenic traits.

Haitian-like genetic traits with creeping MIC of Azithromycin in Vibrio cholerae O1 isolates from Puducherry, India

Introduction. The emergence of novel strains of Vibrio cholerae O1 El Tor biotype has gained attention due to causing several epidemics around the world. Variant strains have evolved as a result of the acquisition of genes that confer extended virulence and pathogenicity.Aim. This study aimed to determine the presence of the most recently emerging Haitian-like genetic traits among the isolates from Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry, Southern India. We also wanted to detect the prevalence of the sulfamethoxazole and trimethoprim (SXT) element, which is an integrating conjugative element (ICE) and the antimicrobial resistance genes present in our isolates.Methodology. Identification of Haitian-specific alleles was done by mismatched amplification mutation assay PCR (MAMA-PCR). The presence of SXT elements was carried out by PCR by detecting int, eex, att-prfC and setR genes. Detection of antibiotic resistance determinant, sul(1,2,3); dfr(A1,18,5) for trimethoprim resistance, tet(A,B,C,D,E,Y,G,M), tet34 for tetracycline resistance and erm(A,B,C), mph(A,B), ere(A,B), msr(A,D) for azithromycin resistance were targeted by PCR. The MIC of tetracycline, ciprofloxacin and azithromycin was determined by the E-test method.Results. Of the 95 isolates, 60 % of the isolates were found to carry Haitian-specific alleles of ctxB, tcpA and rtxA gene, 100 % of the isolates were found to carry SXT elements. All the isolates harboured the four conserved genes of the SXT element, except one which had only eex, att-prfC, setR genes. About 99 % harboured sul2 and dfrA1 genes. No tet and macrolide genes were detected. We observed a progressive increase in the MIC of azithromycin ranging from 0.75 µg ml^-1 to 2 µg ml^-1.Conclusion. None of the isolates were the prototype El Tor biotype. All the isolates were a Haitian variant. The presence of SXT elements across all our isolates and their creeping MIC of azithromycin is a matter of concern. Further testing for other genetic determinants of resistance will be carried out in our future studies.

Vibrio cholerae O6 gastroenteritis in a patient with lupus nephritis - a report from coastal Karnataka, South India

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 toxin co-regulated pilus encoding genes. Toxigenic and non-toxigenic non-O1/non-O139 V. cholerae have caused several diarrhoeal outbreaks in India and other countries. Acute gastroenteritis is the typical clinical sign and symptom of non-O1/non-O139 V. cholerae infection for both periodical and outbreak cases; in contrast, these V. cholerae are rarely associated with extraintestinal infections.

Case presentation

Here, we present a case of a 27-year-old female with underlying kidney disease (lupus nephritis) presenting with loose stools, vomiting and fever. V. cholerae O6 was isolated from a faecal sample, which was positive for hlyA and the type III secretion system. The present case is, to the best of our knowledge, the first such case to be reported from South India.

Conclusion

The V. cholerae O6 associated with autoimmune disease in the present study demonstrates the role of this pathogen in acute gastroenteritis, and if it is left undiagnosed it can lead to septicaemia and other complications. The pathogenic mechanisms of non-O1/non-O139 V. cholerae are multivariate, virulence factors being naturally present in these strains. Therefore, further epidemiological studies are necessary to determine the virulence factors and their pathogenic mechanisms. Non-O1/non-O139 V. cholerae can undoubtedly be the cause of diarrhoea and it would be important to extend bacteriological identification in this line as well as in all cases of gastroenteritis of unknown aetiology.

Haitian Variant Vibrio cholerae O1 Strains Manifest Higher Virulence in Animal Models

Vibrio cholerae causes fatal diarrheal disease cholera in humans due to consumption of contaminated water and food. To instigate the disease, the bacterium must evade the host intestinal innate immune system; penetrate the mucus layer of the small intestine, adhere and multiply on the surface of microvilli and produce toxin(s) through the action of virulence associated genes. V. cholerae O1 that has caused a major cholera outbreak in Haiti contained several unique genetic signatures. These novel traits are used to differentiate them from the canonical El Tor strains. Several studies reported the spread of these Haitian variant strains in different parts of the world including Asia and Africa, but there is a paucity of information on the clinical consequence of these genetic changes. To understand the impact of these changes, we undertook a study involving mice and rabbit models to evaluate the pathogenesis. The colonization ability of Haitian variant strain in comparison to canonical El Tor strain was found to be significantly more in both suckling mice and rabbit model. Adult mice also displayed the same results. Besides that, infection patterns of Haitian variant strains showed a completely different picture. Increased mucosal damaging, colonization, and inflammatory changes were observed through hematoxylin-eosin staining and transmission electron microscopy. Fluid accumulation ability was also significantly higher in rabbit model. Our study indicated that these virulence features of the Haitian variant strain may have some association with the severe clinical outcome of the cholera patients in different parts of the world.

Dissemination of newly emerged polymyxin B sensitive Vibrio cholerae O1 containing Haitian-like genetic traits in different parts of India

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-sensitive El Tor V. cholerae O1 in Kolkata has motivated us to track the spread of the strains containing this important trait, along with Haitian-like genetic content, in different parts of India.

METHODOLOGY

We have collected 260 clinical V. cholerae O1 strains from 12 states in India and screened them for polymyxin B susceptibility. Genetic characterization was also performed to study the tcpA, ctxB and rtxA genotypes by allele-specific polymerase chain reaction (PCR) and nucleotide sequencing.

RESULTS

Interestingly, 88.85 % of the isolates were found to be sensitive to polymyxin B. All of the states, with the exception of Assam, had polymyxin B-sensitive V. cholerae strains and complete replacement with this strain was found in eight of the states. However, from 2016 onwards, all the strains tested showed sensitivity to polymyxin B. Allele-specific PCR and sequencing confirmed that all strains possessed Haitian-like genetic traits.

CONCLUSION

Polymyxin B-sensitive strains have begun to spread throughout India and may lead to the revision of the biotype classification. The dissemination of these new variant strains needs to be carefully monitored in different endemic populations through active holistic surveillance to understand their clinical and epidemiological consequences.

Chromosome-specific physical localisation of expressed sequence tag loci in Corchorus olitorius L

Jute (Corchorus spp.), as a natural fibre-producing species, ranks next only to cotton. Inadequate understanding of its genetic architecture is a major lacuna for genetic improvement of this crop in terms of yield and quality. Establishment of a physical map provides a genomic tool that helps in positional cloning of valuable genes. In this report, an attempt was initiated to study association and localisation of single copy expressed sequence tag (EST) loci in the genome of Corchorus olitorius. The chromosome-specific association of EST was determined based on the appearance of an extra signal for a single copy cDNA probe in mitotic interphase nuclei of specific trisomic(s) for fluorescence in situ hybridisation, and validated using a cDNA fragment of the 26S rRNA gene (600 bp) as molecular probe. The probe exhibited three signals in meiotic interphase nuclei of trisomic 5, instead of two as observed in diploids and other trisomics, indicating its association with chromosome 5. Subsequent hybridisation of the same probe on the pachytene chromosomes of diploids confirmed that 26S rRNA occupies the terminal end of the short arm of chromosome 5 in C. olitorius. Subsequently, chromosome-specific association of 63 single copy EST and their physical localisation were determined on chromosomes 2, 4, 5 and 7. The study describes chromosome-specific physical localisation of genes in jute. The approach used here could be a step towards construction of genome-wide physical maps for any recalcitrant plant species like jute.

Fatal haemophagocytic syndrome and hepatitis associated with visceral leishmaniasis

Haemophagocytic syndrome (HPS) secondary to infections occurs due to excessive, non-malignant proliferation of histiocytes, with resultant haemophagocytosis. The syndrome is essentially treatable, provided timely etiological diagnosis is achieved. In this report, we present a rare case of a child who hailed from Uttaranchal and presented with severe hepatitis. Bone marrow examination revealed an unexpected diagnosis of HPS secondary to visceral leishmaniasis. Despite initiating appropriate antileishmanial treatment, the child had a fatal outcome.