The Lake Chad Basin, an Isolated and Persistent Reservoir of Vibrio cholerae O1: A Genomic Insight into the Outbreak in Cameroon, 2010

Growth response of Vibrio cholerae O1 and V. cholerae non O1/non O139 strains to algae extracts from stream water in far north Cameroon

Background and Objectives

Vibrio cholerae O1 or non O1/non O139 is found in water ecosystems where it colonizes phytoplankton and has different lifestyle. This study aimed to investigate the impact of some algae extracts on the survival/growth of both V. cholerae strains.

Materials and Methods

Algae extracts consisting of three fractions, F1 containing chlorophyll-a, F2 containing chlorophyll-b, and F3 containing carotenoids, and raw extract (RAE) were obtained from the algal bloom collected in the Kaliao stream (Maroua, Cameroon). The survival and growth of V. cholerae O1 and V. cholerae non O1/non O139, in microcosms consisting of sterile saline with these extracts and peptone (PEP) respectively added at concentrations of 0.01, 0.05 and 0.1 mg/L, and 50/50 mixtures F1+F2, F2+F3, and F2+PEP at a concentration 0.05 mg/L, were compared during a 24h experiment.

Results

The microcosms F2 and RAE did not support the growth of O1 strain; V. cholerae non O1/non O139 count in all algae extract microcosms ranging from 3.97 log (CFU/mL) to 5.2 log (CFU/mL). In all PEP microcosms, the counts of both strains reached an uncountable value. Microcosms F1+F2 and F2+F3 supported the growth of V. cholerae O1 and V. cholerae non-O1/nonO139 strains.

Conclusion

The algae compounds showed strain-specific effect on the growth of V. cholerae.

Molecular epidemiology of antimicrobial resistance in central africa: A systematic review

Background

In Central Africa, it is difficult to tackle antibiotic resistance, because of a lack of data and information on bacterial resistance, due to the low number of studies carried out in the field. To fill this gap, we carried out a systematic review of the various studies, and devised a molecular epidemiology of antimicrobial resistance from humans, animals and the environmental samples.

Method

A systematic search of all publications from 2005 to 2020 on bacterial resistance in Central Africa (Gabon, Cameroon, Democratic Republic of Congo, Central African Republic, Chad, Republic of Congo, Equatorial Guinea, São Tomé and Príncipe, Angola) was performed on Pubmed, Google scholar and African Journals Online (AJOL). All circulating resistance genes, prevalence and genetic carriers of these resistances were collected. The study area was limited to the nine countries of Central Africa.

Results

A total of 517 studies were identified through a literature search, and 60 studies carried out in eight countries were included. Among all articles included, 43 articles were from humans. Our study revealed not only the circulation of beta-lactamase and carbapenemase genes, but also several other types of resistance genes. To finish, we noticed that some studies reported mobile genetic elements such as integrons, transposons, and plasmids.

Conclusion

The scarcity of data poses difficulties in the implementation of effective strategies against antibiotic resistance, which requires a health policy in a 'One Health' approach.

Foodborne Pathogenic Vibrios: Antimicrobial Resistance

Foodborne illness caused by pathogenic Vibrios is generally associated with the consumption of raw or undercooked seafood. Fish and other seafood can be contaminated with Vibrio species, natural inhabitants of the marine, estuarine, and freshwater environment. Pathogenic Vibrios of major public health concerns are Vibrio cholerae, Vibrio parahaemolyticus, and Vibrio vulnificus. Common symptoms of foodborne Vibrio infection include watery diarrhea, stomach cramping, nausea, vomiting, fever, and chills. Administration of oral or intravenous rehydration salts solution is the mainstay for the management of cholera, and antibiotics are also used to shorten the duration of diarrhea and to limit further transmission of the disease. Currently, doxycycline, azithromycin, or ciprofloxacin are commonly used for V. cholerae, and doxycycline or quinolone are administered for V. parahaemolyticus, whereas doxycycline and a third-generation cephalosporin are recommended for V. vulnificus as initial treatment regimen. The emergence of antimicrobial resistance (AMR) in Vibrios is increasingly common across the globe and a decrease in the effectiveness of commonly available antibiotics poses a global threat to public health. Recent progress in comparative genomic studies suggests that the genomes of the drug-resistant Vibrios harbor mobile genetic elements like plasmids, integrating conjugative elements, superintegron, transposable elements, and insertion sequences, which are the major carriers of genetic determinants encoding antimicrobial resistance. These mobile genetic elements are highly dynamic and could potentially propagate to other bacteria through horizontal gene transfer (HGT). To combat the serious threat of rising AMR, it is crucial to develop strategies for robust surveillance, use of new/novel pharmaceuticals, and prevention of antibiotic misuse.

Genomic insights into Vibrio cholerae O1 responsible for cholera epidemics in Tanzania between 1993 and 2017

BACKGROUND

Tanzania is one of seven countries with the highest disease burden caused by cholera in Africa. We studied the evolution of Vibrio cholerae O1 isolated in Tanzania during the past three decades.

METHODOLOGY/PRINCIPAL FINDINGS

Genome-wide analysis was performed to characterize V. cholerae O1 responsible for the Tanzanian 2015-2017 outbreak along with strains causing outbreaks in the country for the past three decades. The genomes were further analyzed in a global context of 590 strains of the seventh cholera pandemic (7PET), as well as environmental isolates from Lake Victoria. All Tanzanian cholera outbreaks were caused by the 7PET lineage. The T5 sub-lineage (ctxB3) dominated outbreaks until 1997, followed by the T10 atypical El Tor (ctxB1) up to 2015, which were replaced by the T13 atypical El Tor of the current third wave (ctxB7) causing most cholera outbreaks until 2017 with T13 being phylogenetically related to strains from East African countries, Yemen and Lake Victoria. The strains were less drug resistant with approximate 10-kb deletions found in the SXT element, which encodes resistance to sulfamethoxazole and trimethoprim. Nucleotide deletions were observed in the CTX prophage of some strains, which warrants further virulence studies. Outbreak strains share 90% of core genes with V. cholerae O1 from Lake Victoria with as low as three SNPs difference and a significantly similar accessory genome, composed of genomic islands namely the CTX prophage, Vibrio Pathogenicity Islands; toxin co-regulated pilus biosynthesis proteins and the SXT-ICE element.

CONCLUSION/SIGNIFICANCE

Characterization of V. cholerae O1 from Tanzania reveals genetic diversity of the 7PET lineage composed of T5, T10 and T13 sub-lineages with introductions of new sequence types from neighboring countries. The presence of these sub-lineages in environmental isolates suggests that the African Great Lakes may serve as aquatic reservoirs for survival of V. cholerae O1 favoring continuous human exposure.

VCGIDB: A Database and Web Resource for the Genomic Islands from Vibrio Cholerae

Vibrio cholerae is the causative agent of cholera, which is a severe, life-threatening diarrheal disease. The current seventh pandemic has not been eradicated and the outbreak is still ongoing around the world. The evolution of the pandemic-causing strain has been greatly influenced by lateral gene transfer, and the mechanisms of acquisition of pathogenicity in V. cholerae are mainly involved with genomic islands (GIs). Thus, detecting GIs and their comprehensive information is necessary to understand the continuing resurgence and newly emerging pathogenic V. cholerae strains. In this study, 798 V. cholerae strains were tested using the GI-Scanner algorithm, which was developed to detect candidate GIs and identify them in a comparative genomics approach. The algorithm predicted 435 highly possible genomic islands, and we built a database, called Vibrio cholerae Genomic Island Database (VCGIDB). This database shows advanced results that were acquired from a large genome set using phylogeny-based predictions. Moreover, VCGIDB is a highly expendable database that does not require intensive computation, which enables us to update it with a greater number of genomes using a novel genomic island prediction method. The VCGIDB website allows the user to browse the data and presents the results in a visual manner.

Health facility preparedness for cholera outbreak response in four cholera-prone districts in Cameroon: a cross sectional study

BACKGROUND

The risk of cholera outbreak remains high in Cameroon. This is because of the persistent cholera outbreaks in neighboring countries coupled with the poor hygiene and sanitation conditions in Cameroon. The objective of this study was to assess the readiness of health facilities to respond to cholera outbreak in four cholera-prone districts in Cameroon.

METHODOLOGY

A cross-sectional study was conducted targeting all health facilities in four health districts, labeled as cholera hotspots in Cameroon in August 2016. Data collection was done by interview with a questionnaire and by observation regarding the availability of resources and materials for surveillance and case management, access to water, hygiene, and sanitation. Data analysis was descriptive with STATA 11.

PRINCIPAL FINDINGS

A total of 134 health facilities were evaluated, most of which (108/134[81%]) were urban facilities. The preparedness regarding surveillance was limited with 13 (50%) health facilities in the Far North and 22(20%) in the Littoral having cholera case definition guide. ORS for Case management was present in 8(31%) health facilities in the Far North and in 94(87%) facilities in the littoral. Less than half of the health facilities had a hand washing protocol and 7(5.1%) did not have any source of drinking water or relied on unimproved sources like lake. A total of 4(3.0%) health facilities, all in the Far North region, did not have a toilet.

CONCLUSIONS

The level of preparedness of health facilities in Cameroon for cholera outbreak response presents a lot of weaknesses. These are present in terms of lack of basic surveillance and case management materials and resources, low access to WaSH. If not addressed now, these facilities might not be able to play their role in case there is an outbreak and might even turn to be transmission milieus.

Surveillance and Genomics of Toxigenic Vibrio cholerae O1 From Fish, Phytoplankton and Water in Lake Victoria, Tanzania

The occurrence of toxigenic Vibrio cholerae O1 during a non- outbreak period in Lake Victoria was studied and genetic characteristics for environmental persistence and relatedness to pandemic strains were assessed. We analyzed 360 samples of carps, phytoplankton and water collected in 2017 during dry and rainy seasons in the Tanzanian basin of Lake Victoria. Samples were tested using PCR (ompW and ctxA) with DNA extracted from bacterial isolates and samples enriched in alkaline peptone water. Isolates were screened with polyvalent antiserum O1 followed by antimicrobial susceptibility testing. Whole genome sequencing and bioinformatics tools were employed to investigate the genomic characteristics of the isolates. More V. cholerae positive samples were recovered by PCR when DNA was obtained from enriched samples than from isolates (69.0% vs. 21.3%, p < 0.05), irrespectively of season. We identified ten V. cholerae O1 among 22 ctxA-positive isolates. Further studies are needed to serotype the remaining ctxA-positive non-O1 strains. Sequenced strains belonged to El Tor atypical biotype of V. cholerae O1 of MLST ST69 harboring the seventh pandemic gene. Major virulence genes, ctxA, ctxB, zot, ace, tcpA, hlyA, rtxA, ompU, toxR, T6SS, alsD, makA and pathogenicity islands VPI-1, VPI-2, VSP-1, and VSP-2 were found in all strains. The strains contained Vibrio polysaccharide biosynthesis enzymes, the mshA gene and two-component response regulator proteins involved in stress response and autoinducers for quorum sensing and biofilm formation. They carried the SXT integrative conjugative element with phenotypic and genotypic resistance to aminoglycoside, sulfamethoxazole, trimethoprim, phenicol, and quinolones. Strains contained a multidrug efflux pump component and were resistant to toxic compounds with copper homeostasis and cobalt-zinc-cadmium resistance proteins. The environmental strains belonged to the third wave of the seventh pandemic and most are genetically closely related to recent outbreak strains from Tanzania, Kenya, and Uganda with as low as three SNPs difference. Some strains have persisted longer in the environment and were more related to older outbreak strains in the region. V. cholerae O1 of outbreak potential seem to persist in Lake Victoria through interactions with fish and phytoplankton supported by the optimum water parameters and intrinsic genetic features enhancing survival in the aquatic environment.

Review of molecular subtyping methodologies used to investigate outbreaks due to multidrug-resistant enteric bacterial pathogens in sub-Saharan Africa

Background

In sub-Saharan Africa, molecular epidemiological investigation of outbreaks caused by antimicrobial-resistant enteric bacterial pathogens have mostly been described for Salmonella species, Vibrio cholerae, Shigella species and Escherichia coli. For these organisms, I reviewed all publications describing the use of molecular subtyping methodologies to investigate outbreaks caused by multidrug-resistant (MDR) enteric bacterial infections.

Objectives

To describe the use of molecular subtyping methodologies to investigate outbreaks caused by MDR enteric bacterial pathogens in sub-Saharan Africa and to describe the current status of molecular subtyping capabilities in the region.

Methods

A PubMed database literature search (English language only) was performed using the search strings: ‘Africa outbreak MDR’, ‘Africa outbreak multi’, ‘Africa outbreak multidrug’, ‘Africa outbreak multi drug’, ‘Africa outbreak resistance’, ‘Africa outbreak resistant’, ‘Africa outbreak drug’, ‘Africa outbreak antibiotic’, ‘Africa outbreak antimicrobial’. These search strings were used in combination with genus and species names of the organisms listed above. All results were included in the review.

Results

The year 1991 saw one of the first reports describing the use of molecular subtyping methodologies in sub-Saharan Africa; this included the use of plasmid profiling to characterise Salmonella Enteritidis. To date, several methodologies have been used; pulsed-field gel electrophoresis analysis and multilocus sequence typing have been the most commonly used methodologies. Investigations have particularly highlighted the emergence and spread of MDR clones; these include Salmonella Typhi H58 and Salmonella Typhimurium ST313 clones. In recent times, whole-genome sequencing (WGS) analysis approaches have increasingly been used.

Conclusion

Traditional molecular subtyping methodologies are still commonly used and still have their place in investigations; however, WGS approaches have increasingly been used and are slowly gaining a stronghold. African laboratories need to start adapting their molecular surveillance methodologies to include WGS, as it is foreseen that WGS analysis will eventually replace all traditional methodologies.

Epidemiological and molecular forensics of cholera recurrence in Haiti

Cholera has affected Haiti with damping waves of outbreaks since October 2010. However, mechanisms behind disease persistence during lull periods remain poorly understood. By mid 2014, cholera transmission seemed to only persist in the northern part of Haiti. Meanwhile, cholera appeared nearly extinct in the capital, Port-au-Prince, where it eventually exploded in September 2014. This study aimed to determine whether this outbreak was caused by local undetected cases or by re-importation of the disease from the north. Applying an integrated approach between November 2013 and November 2014, we assessed the temporal and spatial dynamics of cholera using routine surveillance data and performed population genetics analyses of 178 Vibrio cholerae O1 clinical isolates. The results suggest that the northern part of the country exhibited a persisting metapopulation pattern with roaming oligoclonal outbreaks that could not be effectively controlled. Conversely, undetected and unaddressed autochthonous low-grade transmission persisted in the Port-au-Prince area, which may have been the source of the acute outbreak in late-2014. Cholera genotyping is a simple but powerful tool to adapt control strategies based on epidemic specificities. In Haiti, these data have already yielded significant progress in cholera surveillance, which is a key component of the strategy to eventually eliminate cholera.

Antimicrobial resistance of Vibrio cholerae from sub-Saharan Africa: A systematic review

Background

The World Health Assembly adopted the Global Action Plan on Antimicrobial Resistance, which includes improving the knowledge base through surveillance and research. Noteworthily, the World Health Organization has advocated a Global Antimicrobial Resistance Surveillance System to address the plan’s surveillance objective, with most African countries enrolling in or after 2017.

Aim

The aim of this article was to review prior data on antimicrobial resistance of Vibrio cholerae from sub-Saharan Africa with a view for future control and intervention strategies.

Methods

We used the Preferred Reporting Items for Systematic Review and Meta-Analysis (or ‘PRISMA’) guidelines to search the PubMed and African Journals Online databases, as well as additional articles provided by the Nigeria Centre for Disease Control, for articles reporting on the antibiotic susceptibility of V. cholerae between January 2000 and December 2017.

Results

We identified 340 publications, of which only 25 (reporting from 16 countries within the sub-Saharan African region) were eligible. The majority (20; 80.0%) of the cholera toxigenic V. cholerae isolates were of the serogroup O1 of the El Tor biotype with Ogawa and Inaba serotypes predominating. Resistance was predominantly documented to trimethoprim-sulphamethoxazole (50% of the studies), ampicillin (43.3% of the studies), chloramphenicol (43.3% of the studies) and streptomycin (30% of the studies). Resistance mechanisms were reported in 40% of the studies.

Conclusion

Our results demonstrate a documented antimicrobial resistance of V. cholerae to multiple antibiotic classes, including cell wall active agents and antimetabolites with evidence of phenotypic/genotypic resistance to fluoroquinolones.

Comparative genomics of Vibrio cholerae O1 isolated from cholera patients in Bangladesh

Whole genome sequencing was utilized to investigate the genomic profile of Vibrio cholerae O1 strains, isolated from symptomatic patients in a low-income urban area of Dhaka, Bangladesh. Comparative genomics using bioinformatics tools were applied to identify major virulence factors, biotype and antimicrobial resistance genes in three V. cholerae O1 strains (VC-1, 2 and 3) isolated from two case patients. A phylogenetic SNP (single nucleotide polymorphism)-based analysis was conducted to infer the relatedness to V. cholerae O1 strains isolated elsewhere. The V. cholerae strains were the El Tor variant carrying ctxB1 (standard classical genotype). SNP-based global phylogeny revealed that the three isolates were strictly clonal and the closest neighbouring genomes were epidemic clones of V. cholerae O1 isolated in 2010 from cholera patients in Pakistan. All strains harboured the integrase gene of the SXT element (int_SXT ), antimicrobial resistance genes for aminoglycosides, phenicol, sulphonamide and trimethoprim except VC-1 that lacked sulphonamide resistance genes. The multilocus sequence typing (MLST) revealed that the strains belonged to sequence type, ST69. The study provides knowledge on current genetic traits of clinical V. cholerae O1 circulating in urban household clusters of Bangladesh which may help in predicting emergence of new pandemic strains in Bangladesh.

SIGNIFICANCE AND IMPACT OF THE STUDY

Vibrio cholerae has frequently experienced genetic changes with rapid evolution of pandemic clones in the Ganges Delta region. Whole genome sequencing can reveal genetic information of current pathogenic V. cholerae in Bangladesh which includes cefotaxime genotypes, virulence factors, altered antimicrobial resistance pattern as well as mobile genetic element compared to global pandemic strains. This study data could be used in planning future surveillance strategies in Ganges Delta region by informing new epidemiology of current outbreak strains.

Analysis of Vibrio seventh pandemic island II and novel genomic islands in relation to attachment sequences among a wide variety of Vibrio cholerae strains

Vibrio cholerae O1 El Tor, the pathogen responsible for the current cholera pandemic, became pathogenic by acquiring virulent factors including Vibrio seventh pandemic islands (VSP)‐I and −II. Diversity of VSP‐II is well recognized; however, studies addressing attachment sequence left (attL) sequences of VSP‐II are few. In this report, a wide variety of V. cholerae strains were analyzed for the structure and distribution of VSP‐II in relation to their attachment sequences. Of 188 V. cholerae strains analyzed, 81% (153/188) strains carried VSP‐II; of these, typical VSP‐II, and a short variant was found in 36% (55/153), and 63% (96/153), respectively. A novel VSP‐II was found in two V. cholerae non‐O1/non‐O139 strains. In addition to the typical 14‐bp attL, six new attL‐like sequences were identified. The 14‐bp attL was associated with VSP‐II in 91% (139/153), whereas the remaining six types were found in 9.2% (14/153) of V. cholerae strains. Of note, six distinct types of the attL‐like sequence were found in the seventh pandemic wave 1 strains; however, only one or two types were found in the wave 2 or 3 strains. Interestingly, 86% (24/28) of V. cholerae seventh pandemic strains harboring a 13‐bp attL‐like sequence were devoid of VSP‐II. Six novel genomic islands using two unique insertion sites to those of VSP‐II were identified in 11 V. cholerae strains in this study. Four of those shared similar gene clusters with VSP‐II, except integrase gene.

Genomic history of the seventh pandemic of cholera in Africa

The seventh cholera pandemic has heavily affected Africa, although the origin and continental spread of the disease remain undefined. We used genomic data from 1070 Vibrio cholerae O1 isolates, across 45 African countries and over a 49-year period, to show that past epidemics were attributable to a single expanded lineage. This lineage was introduced at least 11 times since 1970, into two main regions, West Africa and East/Southern Africa, causing epidemics that lasted up to 28 years. The last five introductions into Africa, all from Asia, involved multidrug-resistant sublineages that replaced antibiotic-susceptible sublineages after 2000. This phylogenetic framework describes the periodicity of lineage introduction and the stable routes of cholera spread, which should inform the rational design of control measures for cholera in Africa.

Characterization and Genetic Variation of Vibrio cholerae Isolated from Clinical and Environmental Sources in Thailand

Cholera is still an important public health problem in several countries, including Thailand. In this study, a collection of clinical and environmental V. cholerae serogroup O1, O139, and non-O1/non-O139 strains originating from Thailand (1983 to 2013) was characterized to determine phenotypic and genotypic traits and to investigate the genetic relatedness. Using a combination of conventional methods and whole genome sequencing (WGS), 78 V. cholerae strains were identified. WGS was used to determine the serogroup, biotype, virulence, mobile genetic elements, and antimicrobial resistance genes using online bioinformatics tools. In addition, phenotypic antimicrobial resistance was determined by the minimal inhibitory concentration (MIC) test. The 78 V. cholerae strains belonged to the following serogroups O1: (n = 44), O139 (n = 16) and non-O1/non-O139 (n = 18). Interestingly, we found that the typical El Tor O1 strains were the major cause of clinical cholera during 1983–2000 with two Classical O1 strains detected in 2000. In 2004–2010, the El Tor variant strains revealed genotypes of the Classical biotype possessing either only ctxB or both ctxB and rstR while they harbored tcpA of the El Tor biotype. Thirty O1 and eleven O139 clinical strains carried CTXϕ (Cholera toxin) and tcpA as well four different pathogenic islands (PAIs). Beside non-O1/non-O139, the O1 environmental strains also presented chxA and Type Three Secretion System (TTSS). The in silico MultiLocus Sequence Typing (MLST) discriminated the O1 and O139 clinical strains from other serogroups and environmental strains. ST69 was dominant in the clinical strains belonging to the 7^th pandemic clone. Non-O1/non-O139 and environmental strains showed various novel STs indicating genetic variation. Multidrug-resistant (MDR) strains were observed and conferred resistance to ampicillin, azithromycin, nalidixic acid, sulfamethoxazole, tetracycline, and trimethoprim and harboured variants of the SXT elements.

For the first time since 1986, the presence of V. cholerae O1 Classical was reported causing cholera outbreaks in Thailand. In addition, we found that V. cholerae O1 El Tor variant and O139 were pre-dominating the pathogenic strains in Thailand. Using WGS and bioinformatic tools to analyze both historical and contemporary V. cholerae circulating in Thailand provided a more detailed understanding of the V. cholerae epidemiology, which ultimately could be applied for control measures and management of cholera in Thailand.

Genetic Studies of Vibrio cholerae in South West Cameroon-A Phylogenetic Analysis of Isolates from the 2010-2011 Epidemic

INTRODUCTION

During the cholera outbreak from 2010 to 2011 in Cameroon, 33,192 cases with 1,440 deaths (case fatality ratio 4.34%) were reported to the World Health Organization. Of these, the South West Region reported 3,120 clinical cases. This region is in the Equatorial Monsoon climatic subzone of Cameroon, close to the coast, raising questions as to whether cases were linked with development of environmental reservoirs.

METHODS

In an investigation conducted by the Laboratory for Emerging Infectious Diseases, University of Buea, toxigenic V. cholerae O1 were isolated from diarrheal stool samples from 18 patients, with ages ranging from <3 to 70 years. Coordinates for clinical centers at which cases were identified were obtained using a handheld GPS, and were mapped using ArcGIS. Antibiotic susceptibility testing was performed using the Kirby 'Bauer agar disc diffusion method. The full genomes of these strains were sequenced with the Illumina MiSeq platform. De novo assembly of cholera genomes and multiple sequence alignment were carried out using the bioinformatics pipeline developed in the Emerging Pathogens Institute laboratory at the University of Florida.

RESULTS/DISCUSSION

Genetic comparisons showed that isolates were closely related, with pairwise p-distances ranging from 2.25 to 14.52 10-5 nt substitutions per site, and no statistically significant correlation between the pairwise genetic distances and the geographic distances among sampling locations. Indeed, the phylogeny of the Cameroonian strains displays the typical star-like topology and intermixing of strains from different locations that are characteristic of an exponential outbreak localized around a relatively restricted area with occasional spillover to other parts of the country, likely mediated by direct human contact and human movement. Findings highlight the utility of whole genome sequencing and phylogenetic analysis in understanding transmission patterns at the local level.