Dataset Information

Genomic characterization of invasive typhoidal and non-typhoidal Salmonella in southwestern Nigeria.

ABSTRACT:

Background

Salmonellosis causes significant morbidity and mortality in Africa. Information on lineages of invasive Salmonella circulating in Nigeria is sparse.

Methods

Salmonella enterica isolated from blood (n = 60) and cerebrospinal fluid (CSF, n = 3) between 2016 and 2020 from five tertiary hospitals in southwest Nigeria were antimicrobial susceptibility-tested and Illumina-sequenced. Genomes were analysed using publicly-available bioinformatic tools.

Results

Isolates and sequence types (STs) from blood were S. Typhi [ST1, n = 1 and ST2, n = 43] and invasive non-typhoidal Salmonella (iNTS) (S. Enteritidis [ST11, n = 7], S. Durham [ST10, n = 2], S. Rissen [ST8756, n = 2], S. Chester [ST2063, n = 1], S. Dublin [ST10, n = 1], S. Infantis [ST603, n = 1], S. Telelkebir [ST8757, n = 1] and S. Typhimurium [ST313, n = 1]). S. Typhi ST2 (n = 2) and S. Adabraka ST8757 (n = 1) were recovered from CSF. Most S. Typhi belonged to genotype 3.1.1 (n = 44), carried an IncY plasmid, had several antibiotic resistance genes (ARGs) including blaTEM-1 (n = 38), aph(6)-Id (n = 32), tet(A) (n = 33), sul2 (n = 32), dfrA14 (n = 30) as well as quinolone resistance-conferring gyrA_S83Y single-nucleotide polymorphisms (n = 37). All S. Enteritidis harboured aph(3")-Ib, blaTEM-1, catA1, dfrA7, sul1, sul2, tet(B) genes, and a single ARG, qnrB19, was detected in S. Telelkebir. Typhoidal toxins cdtB, pltA and pltB were detected in S. Typhi, Rissen, Chester, and Telelkebir.

Conclusion

Most invasive salmonelloses in southwest Nigeria are vaccine-preventable infections due to multidrug-resistant, West African dominant S. Typhi lineage 3.1.1. Invasive NTS serovars, including some harbouring typhoidal toxin or resistance genes, represented a third of the isolates emphasizing the need for better diagnosis and surveillance.

SUBMITTER: Ikhimiukor OO

PROVIDER: S-EPMC9455843 | biostudies-literature | 2022 Aug

REPOSITORIES: biostudies-literature

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Publications

Genomic characterization of invasive typhoidal and non-typhoidal Salmonella in southwestern Nigeria.

Ikhimiukor Odion O OO Oaikhena Anderson O AO Afolayan Ayorinde O AO Fadeyi Abayomi A Kehinde Aderemi A Ogunleye Veronica O VO Aboderin Aaron O AO Oduyebo Oyinlola O OO Elikwu Charles J CJ Odih Erkison Ewomazino EE Komolafe Ifeoluwa I Argimón Silvia S Egwuenu Abiodun A Adebiyi Ini I Sadare Oluwadamilola A OA Okwor Tochi T Kekre Mihir M Underwood Anthony A Ihekweazu Chikwe C Aanensen David M DM Okeke Iruka N IN

PLoS neglected tropical diseases 20220826 8

<h4>Background</h4>Salmonellosis causes significant morbidity and mortality in Africa. Information on lineages of invasive Salmonella circulating in Nigeria is sparse.<h4>Methods</h4>Salmonella enterica isolated from blood (n = 60) and cerebrospinal fluid (CSF, n = 3) between 2016 and 2020 from five tertiary hospitals in southwest Nigeria were antimicrobial susceptibility-tested and Illumina-sequenced. Genomes were analysed using publicly-available bioinformatic tools.<h4>Results</h4>Isolates an ...[more]

PMID: 36026470

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Project description:BackgroundInvasive Non-typhoidal Salmonella (iNTS) are an important cause of bacteraemia in children and HIV-infected adults in sub-Saharan Africa. Previous research has shown that iNTS strains exhibit a pattern of gene loss that resembles that of host adapted serovars such as Salmonella Typhi and Paratyphi A. Salmonella enterica serovar Bovismorbificans was a common serovar in Malawi between 1997 and 2004.MethodologyWe sequenced the genomes of 14 Malawian bacteraemia and four veterinary isolates from the UK, to identify genomic variations and signs of host adaptation in the Malawian strains.Principal findingsWhole genome phylogeny of invasive and veterinary S. Bovismorbificans isolates showed that the isolates are highly related, belonging to the most common international S. Bovismorbificans Sequence Type, ST142, in contrast to the findings for S. Typhimurium, where a distinct Sequence Type, ST313, is associated with invasive disease in sub-Saharan Africa. Although genome degradation through pseudogene formation was observed in ST142 isolates, there were no clear overlaps with the patterns of gene loss seen in iNTS ST313 isolates previously described from Malawi, and no clear distinction between S. Bovismorbificans isolates from Malawi and the UK. The only defining differences between S. Bovismorbificans bacteraemia and veterinary isolates were prophage-related regions and the carriage of a S. Bovismorbificans virulence plasmid (pVIRBov).ConclusionsiNTS S. Bovismorbificans isolates, unlike iNTS S. Typhiumrium isolates, are only distinguished from those circulating elsewhere by differences in the mobile genome. It is likely that these strains have entered a susceptible population and are able to take advantage of this niche. There are tentative signs of convergent evolution to a more human adapted iNTS variant. Considering its importance in causing disease in this region, S. Bovismorbificans may be at the beginning of this process, providing a reference against which to compare changes that may become fixed in future lineages in sub-Saharan Africa.

Project description:Human infection with non-typhoidal Salmonella serovars (NTS) infrequently causes invasive systemic disease and bacteremia. To understand better the nature of invasive NTS (iNTS), we studied the gene content and the pathogenicity of bacteremic strains from twelve serovars (Typhimurium, Enteritidis, Choleraesuis, Dublin, Virchow, Newport, Bredeney, Heidelberg, Montevideo, Schwarzengrund, 9,12:l,v:- and Hadar). Comparative genomic hybridization using a Salmonella enterica microarray revealed a core of 3233 genes present in all of the iNTS strains, which include the Salmonella pathogenicity islands 1-5, 9, 13, 14; five fimbrial operons (bcf, csg, stb, sth, sti); three colonization factors (misL, bapA, sinH); and the invasion gene, pagN. In the iNTS variable genome, we identified 16 novel genomic islets; various NTS virulence factors; and six typhoid-associated virulence genes (tcfA, cdtB, hlyE, taiA, STY1413, STY1360), displaying a wider distribution among NTS than was previously known. Characterization of the bacteremic strains in C3H/HeN mice showed clear differences in disease manifestation. Previously unreported characterization of serovars Schwarzengrund, 9,12:l,v:-, Bredeney and Virchow in the mouse model showed low ability to elicit systemic disease, but a profound and elongated shedding of serovars Schwarzengrund and 9,12:l,v:- (as well as Enteritidis and Heidelberg) due to chronic infection of the mouse. Phenotypic comparison in macrophages and epithelial cell lines demonstrated a remarkable intra-serovar variation, but also showed that S. Typhimurium bacteremic strains tend to present lower intracellular growth than gastroenteritis isolates. Collectively, our data demonstrated a common core of virulence genes, which might be required for invasive salmonellosis, but also an impressive degree of genetic and phenotypic heterogeneity, highlighting that bacteremia is a complex phenotype, which cannot be attributed merely to an enhanced invasion or intracellular growth of a particular strain.

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Dataset Information

Genomic characterization of invasive typhoidal and non-typhoidal Salmonella in southwestern Nigeria.

Background

Methods

Results

Conclusion

Publications

Genomic characterization of invasive typhoidal and non-typhoidal Salmonella in southwestern Nigeria.

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