Non-typhoidal Salmonella Isolates Research Articles

Temporal association of antimicrobial use in livestock with antimicrobial resistance in non-typhoid Salmonella human infections in the Netherlands, 2008–2019

BackgroundAntimicrobial use (AMU) in livestock contributes to antimicrobial resistance (AMR) among zoonotic pathogens, such as non-typhoid Salmonella (NTS). Since 2009, the Netherlands has made substantial efforts to reduce AMU in livestock. ObjectivesTo assess the association between AMU in livestock and AMR in NTS human isolates. Additionally, associations between AMU in broilers/pigs and AMR in NTS broiler/pig isolates, and between AMR in broilers/pigs and in human NTS isolates were assessed. The focus was on Salmonella Enteritidis (SE) and Salmonella Typhimurium including its monophasic variant (ST/STM). MethodsA national population registry-based study was conducted in the Netherlands from 2008 to 2019. Multivariable logistic regression models were used to assess the associations between livestock AMU and NTS resistance proportion in humans and broilers/pigs, overall as well as per class-specific antimicrobials. Correlation analysis was performed to relate AMR proportions between human and broiler/pig NTS isolates. ResultsFor SE, only a positive association between penicillins use in broilers and resistance to ampicillin among human isolates was significant. For ST/STM, most associations between AMU in livestock and AMR among human isolates were significantly positive, overall and per class-specific antimicrobials, namely for penicillins-ampicillin, tetracyclines-tetracycline and sulfonamides/trimethoprim-sulfamethoxazole/trimethoprim. Significantly positive associations between AMU in broilers/pigs and AMR in broiler/pig ST/STM isolates were also observed, but not between broiler/pig and human AMR levels. ConclusionsSignificant associations were generally found between livestock AMU and AMR in human and broiler/pig ST/STM isolates. However, confounding factors, such as imported meat and travel are of concern. To fully comprehend the impact of livestock AMU on resistance in human NTS isolates, it is imperative to enhance AMR surveillance of NTS.

Antimicrobial Resistance and Zoonotic Potential of Nontyphoidal Salmonella From Household Dogs.

Companion animals, like household dogs, are an overlooked transmission point for zoonotic pathogens such as nontyphoidal Salmonella (NTS). Given the proximity of dogs to humans and the use of critically important antibiotics in companion animal medicine, household dogs represent a risk for the spread of antimicrobial-resistant (AMR) Salmonella. To this end, we aimed to leverage existing biosurveillance infrastructure to investigate AMR and the zoonotic potential of NTS isolated from dogs and humans. We identified all NTS strains isolated from domestic dogs via the Veterinary Laboratory Investigation and Response Network between May 2017 and March 2023 (N = 87), and spatiotemporally matched strains isolated from humans in the NCBI Pathogen Isolate Browser (N = 77). These 164 strains, collected from 17 states in the United States, formed the basis of our analysis. Strains isolated from dogs comprised diverse serovars, with most being clinically relevant to human health. All strains possessed AMR determinants for drug classes deemed critically or highly important by the World Health Organization. We identified sixteen NTS isolates from humans closely related to ≥1 of six dog-associated strains. Collectively, our data emphasize the importance of antimicrobial stewardship and sustained biosurveillance beyond human- and agriculture-associated veterinary medicine, using a One-Health framework that accounts for all transmission points including companion animals.

Serovars, virulence factors, and antimicrobial resistance profile of non-typhoidal Salmonella in the human-dairy interface in Northwest Ethiopia: A one health approach.

Non-typhoidal Salmonella (NTS) is a zoonotic pathogen that exerts huge public health and economic impacts in the world. The severity of illness is mainly related to the serovars involved, the presence of virulence genes, and antimicrobial resistance (AMR) patterns. However, data are scarce on serovars, virulence genes, and AMR among NTS identified from the human-dairy interface in Northwest Ethiopia. Thus, this study investigated the serovars, common virulence genes, and AMR patterns of NTS isolates in the area. The study was conducted from June 2022 to August 2023 among randomly selected 58 dairy farms. A total of 362 samples were processed to detect NTS using standard bacteriological methods. The presumptive positive colonies were confirmed by Matrix-Assisted Laser Desorption Ionization-Time-of-Flight (MALDi-ToF). Polymerase chain reaction (PCR) was used to detect virulence genes, including invA and spvC. A slide agglutination test according to the White-Kauffmann-Le Minor scheme was employed to identify the serovars of the NTS isolates. The Kirby-Bauer disk diffusion method was used to assess the antimicrobial susceptibility patterns. Of the processed samples (362), 28 (7.7%) NTS isolates were detected. When distributed among samples, the proportions were 11.9%, 10.5%, 10.3%, 5.2%, 4.3%, and 1.7% among cows' feces, dairy farm sewage, pooled raw milk, milk container swabs, milkers' stool, and milkers' hand swab samples, respectively. Six serovars were detected with the dominancy of S. Uganda (39.3%), followed by S. enterica subsp. diarizonae (25.0%) and S. Typhimurium (21.4%). Among the 28 NTS isolates, 100% and 21.4% had the virulence genes invA and spvC, respectively. The susceptibility profile showed that 89.3% of the NTS isolates were resistant to at least one antimicrobial agent and 46.4% were resistant to three or more classes of antimicrobials (multidrug-resistant). Among antimicrobials, isolates were highly resistant to ampicillin (57.1%), followed by tetracycline (42.9%) and chloramphenicol (35.7%). On the other hand, the NTS isolates were 100%, 96.4%, and 96.4% susceptible to ceftriaxone, azithromycin, and norfloxacin, respectively. In conclusion, we detected NTS from humans, dairy cows, raw milk, dairy utensils, and the environment (sewage), showing the potential of the human-dairy farm-environment nexus in the NTS circulation. These further highlight that the interface is a good point of intervention in the control and prevention of NTS infection. The susceptibility profiles of the isolate necessitate interventions including the prudent use of the antimicrobials.

Genotypic Antimicrobial Resistance Profiles of Diarrheagenic Escherichia coli and Nontyphoidal Salmonella Strains Isolated from Children with Diarrhea and Their Exposure Environments in Ethiopia.

Antimicrobial resistance (AMR) poses a significant global threat, particularly in low- and middle-income countries, such as Ethiopia, where surveillance is limited. This study aimed to predict and characterize the AMR profiles of diarrheagenic Escherichia coli (DEC) and nontyphoidal Salmonella (NTS) strains isolated from human, animal, food, and environmental samples using whole genome sequencing. A total of 57 NTS and 50 DEC isolates were sequenced on an Illumina NextSeq 550. The ResFinder and PointFinder tools were employed to identify antimicrobial resistance genes (ARGs) and point mutations. Salmonella serotypes were determined using SeqSero. The analysis identified at least one ARG in every NTS sample and 78% of the DEC isolates, with 22 distinct ARGs in the NTS samples and 40 in the DEC samples. The most prevalent ARGs were aac(6')-Iaa and aph(3')-Ib, which predict aminoglycoside resistance in 100% of NTS and 54% of DEC isolates, respectively. Other commonly identified ARGs include sul2, aph(6)-Id, blaTEM-1B , and tet(A), which confer resistance to folate inhibitors, aminoglycosides, β-lactams, and tetracycline. Some ARGs predicted phenotypic multidrug resistance in both DEC and NTS isolates. All identified β-lactam ARGs, except for blaTEM -1D, conferred resistance to more than three antibiotics. Interestingly, blaCTX- M-15 was found to confer resistance to nine antibiotics, including third-generation cephalosporins, in 18% of DEC and 3.5% of NTS isolates. DEC isolates from children exhibited the highest ARG diversity. Notably, genes such as aph(3″)-Ib, aph(6)-Id, sul2, and tet(A) were detected across all sample types, including water sources, although some ARGs were exclusive to specific sample types. Point mutations mediating AMR were detected in several genes, with mutations associated with nucleotide substitution being the most frequent. This genotypic AMR profiling revealed the presence of widespread drug-resistant NTS and DEC strains in Ethiopia. Robust and sustained AMR surveillance is essential for monitoring the emergence and spread of these resistant pathogens.

Low-cost biosecurity measures are associated with reduced detection of non-Typhoidal Salmonella in Nigerian poultry while inappropriate antibiotic use is widespread

Large-scale poultry production in low- and middle-income countries may be a source of adulterated products (e.g., Salmonella contamination, antibiotic residues) that can be disseminated over wide areas. We employed a cross-sectional survey of 199 randomly selected poultry farms in Lagos State, Nigeria, to estimate the prevalence of non-typhoidal Salmonella (NTS), and biosecurity and antibiotic use practices. Pooled fecal samples were collected from laying chickens and from poultry handlers. Selective culture, biochemical assays, and PCR (invA) were used to isolate and confirm NTS isolates. NTS was detected at 14% of farms (28/199) and from 10% of farm workers (6/60). Multivariate logistic regression analysis indicated that antiseptic foot dips reduced the odds ratio (OR) for detecting NTS in chicken feces [OR: 0.55; 95% confidence interval (CI) 0.07–0.58]. Most farms (94.5%, 188/199) used antibiotics for treatment and prophylaxis, but no farms (0/199) exercised withdrawal before sale of products. Most farms (86.4%, 172/199) reported using antibiotic cocktails that included medically important colistin, ciprofloxacin, chloramphenicol, and gentamicin. Egg production in Lagos State relies heavily on antibiotics and antibiotic residues are likely passed to consumers through poultry products, but there is evidence that low-cost biosecurity controls are effective for limiting the presence of NTS on farms.

Plasmid-mediated azithromycin resistance in non-typhoidal Salmonella recovered from human infections.

Mechanisms of non-typhoidal Salmonella (NTS) resistance to azithromycin have rarely been reported. Here we investigate the epidemiology and genetic features of 10 azithromycin-resistant NTS isolates. A total of 457 NTS isolates were collected from a tertiary hospital in Guangzhou. We performed antimicrobial susceptibility tests, conjugation experiments, efflux pump expression tests, whole-genome sequencing and bioinformatics analysis to conduct the study. The results showed that 10 NTS isolates (2.8%) were resistant to azithromycin with minimum inhibitory concentration values ranging from 128 to 512 mg/L and exhibited multidrug resistance. The phylogenetic tree revealed that 5 S. London isolates (AR1-AR5) recognized at different times and departments were closely related [3-74 single-nucleotide polymorphisms (SNPs)] and 2 S. Typhimurium isolates (AR7 and AR8) were clones (<3 SNPs) at 3-month intervals. The azithromycin resistance was conferred by mph(A) gene found on different plasmids, including IncFIB, IncHI2, InFII, IncC and IncI plasmids. Among them, IncFIB, InFII and IncHI2 plasmids carried different IS26-class 1 integron (intI1) arrangement patterns that mediated multidrug resistance transmission. Conjugative IncC plasmid encoded resistance to ciprofloxacin, ceftriaxone and azithromycin. Furthermore, phylogenetic analysis demonstrated that mph(A)-positive plasmids closely related to 10 plasmids in this study were mainly discovered from NTS, Escherichia coli, Klebsiella pneumonia and Enterobacter hormaechei. The genetic environment of mph(A) in 10 NTS isolates was IS26-mph(A)-mrx(A)-mphR(A)-IS6100/IS26 that co-arranged with intI1 harbour multidrug-resistant (MDR) gene cassettes on diverse plasmids. These findings highlighted that the dissemination of these plasmids carrying mph(A) and various intI1 MDR gene cassettes would seriously restrict the availability of essential antimicrobial agents for treating NTS infections.

Differences in the prevalence and antimicrobial resistance among non-typhoidal Salmonella serovars isolated from retail chicken meat across the United States of America, 2013–2020

The emergence of antimicrobial-resistant non-typhoidal Salmonella (NTS) in retail chicken meat poses a food safety risk. Data on antimicrobial resistance (AMR) in NTS isolates collected by the National Antimicrobial Resistance Monitoring System for Enteric Bacteria (NARMS) from retail chicken meat across the United States of America between 2013 and 2020 were analyzed. A total of 3,067 samples tested positive for NTS. The most common NTS serovars were S. Kentucky (n = 1,088), S. Infantis (n = 587), S. Enteritidis (n = 475), and S. Typhimurium (n = 424), respectively. A significant increasing trend in the proportion of S. Infantis and a decreasing trend for S. Typhimurium has been observed. High-proportion clusters were detected in the northeast and southeast of the United States of America for S. Typhimurium and in the west coast and southeast for S. Kentucky. Multidrug resistance (resistance to at least three antimicrobial classes) was common in S. Infantis and S. Typhimurium isolates, while S. Enteritidis isolates were mainly pan-susceptible. The predicted probability of resistance to beta-lactam antibiotics (ampicillin and ceftriaxone), sulfonamides (sulfisoxazole), and quinolones (nalidixic acid) were highest in S. Infantis isolates, while S. Kentucky isolates showed the highest probability of resistance to aminoglycosides (streptomycin) and tetracyclines. Differences in the geographical distribution of NTS serovars and variations in their AMR patterns warrant serovar-specific antimicrobial stewardship programs.

Impact of COVID-19-related nonpharmaceutical interventions on diarrheal diseases and zoonotic Salmonella

Non-pharmaceutical interventions (NPIs) have been proven effective in reducing the spread of the coronavirus disease 2019 (COVID-19), but their broader impact on gastrointestinal disorders remains poorly studied. Here, we report an observational analysis and retrospective study that compares the incidence of acute diarrheal diseases in Hangzhou, Zhejiang, China, between 2019 and 2020, with an examination of the antimicrobial resistance and genetic spectrum of non-typhoidal Salmonella (NTS) from 2015 to 2022, before and during the COVID-19 pandemic. Our findings underscore that NPIs related to COVID-19 effectively reduced the incidence of acute diarrhea, with a substantial decrease in most enteric pathogens. Notably, NTS exhibited an unexpected surge. Further genomic investigations of NTS isolates revealed an overall reduction in antimicrobial-resistant (AMR), disinfection-tolerant, and virulent capabilities, but with marked variations detected between human and animal isolates. Additional genome-based analysis confirmed a decrease in the scale of zoonotic transmission in response to NPIs, suggesting particular NTS types may contribute to human infections via alternative pathways. The collective findings manifested that COVID-19-related NPIs had a mixed impact on NTS infections, which may inform AMR NTS mitigation policy.

Prevalence and dissemination of mcr-9.1-producing non-typhoidal Salmonella strains from diarrhea patients throughout China during 2010–2020

The emergence of mobilized colistin resistance (mcr) genes has raised significant concerns as they pose a public health issue. The prevalence of mcr genes, particularly the newly discovered mcr-9 gene, in non-typhoidal Salmonella (NTS) isolates remains unclear. We characterized mcr-9.1-producing NTS isolates from China. Among 7,106 NTS isolates from diarrhea cases in 32 provinces during 2010–2020, 11 mcr-9.1-producing isolates were identified and were all not resistant to colistin. Five isolates belonged to Salmonella Thompson and sequence type (ST) 26, two belonged to Salmonella Typhimurium and ST34, two belonged to Salmonella Typhimurium and ST36, and two belonged to Salmonella 1,4,[5],12:i:- and ST34. Plasmids harboring mcr-9.1 tended to possess the IncHI2 backbone and were ~ 300 kb long. All mcr-9.1 genes shared the same flanking sequence, rcnR-rcnA-pcoS-IS903-mcr-9.1-wbuC. According to the NCBI data, we found that NTS serves as the primary host of mcr-9.1, although the prevalence of specific serotypes differed between domestic and international settings. Notably, most data came from developed countries, such as the USA. mcr-9.1 tended to be transferred as a gene cassette or to be mobilized by a conjugational plasmid in multiple bacteria across humans, animals, and the environment. Furthermore, mcr-9.1 frequently co-existed and was co-transferred with various genes encoding resistance to first-line drugs, reducing the effectiveness of available therapeutic options. In summary, although mcr-9 does not mediate colistin resistance, it can silently spread with some genes encoding resistance to first-line drugs, and therefore warrants research attention.

Whole-Genome Sequencing Analysis of Non-Typhoidal Salmonella Isolated from Breeder Poultry Farm Sources in China, 2020-2021.

Non-typhoidal salmonellosis is a dangerous foodborne disease that causes enormous economic loss and threatens public health worldwide. The consumption of food, especially poultry or poultry products, contaminated with non-typhoidal Salmonella (NTS) is the main cause of human salmonellosis. To date, no research has identified the molecular epidemiological characteristics of NTS strains isolated from breeder chicken farms in different provinces of China. In our study, we investigated the antimicrobial resistance, phylogenetic relationships, presence of antimicrobial resistance and virulence genes, and plasmids of NTS isolates recovered from breeder chicken farms in five provinces of China between 2020 and 2021 by using a whole-genome sequencing (WGS) approach and phenotypic methods. All sequenced isolates belonged to six serovars with seven sequence types. Nearly half of the isolates (44.87%) showed phenotypic resistance to at least three classes of antimicrobials. Salmonella enterica serotype Kentucky harbored more antimicrobial resistance genes than the others, which was highly consistent with phenotypic resistance. Furthermore, the carried rate of 104 out of 135 detected virulence genes was 100%. Overall, our WGS results highlight the need for the continuous monitoring of, and additional studies on, the antimicrobial resistance of NTS.

The epidemiology of fecal carriage of nontyphoidal Salmonella among healthy children and adults in three sites in Kenya.

Despite the importance of non-Typhoidal Salmonella (NTS) disease in Africa, epidemiologic data on carriage and transmission are few. These data are important to understand the transmission of NTS in Africa and to design control strategies. To estimate the prevalence of stool carriage of NTS in Kenya, we conducted a cross-sectional study in Kilifi, Nairobi, and Siaya, sites with a low, moderate and high incidence of invasive NTS disease, respectively. At each site, we randomly selected 100 participants in each age-group of 0-11 months, 12-59 months, 5-14 years, 15-54 years and ≥55 years. We collected stool, venous blood (for hemoglobin and malaria rapid tests), anthropometric measurements, and administered a questionnaire on Water Access Sanitation and Hygiene (WASH) practices. Stool samples were cultured on selective agar for Salmonella; suspect isolates underwent serotyping and antimicrobial susceptibility testing. Overall, 53 (3.5%) isolates of NTS were cultured from 1497 samples. Age-adjusted prevalence was 13.1% (95%CI 8.8-17.4) in Kilifi, 0.4% (95%CI 0-1.3) in Nairobi, and 0.9% (95%CI 0-2.0) in Siaya. Prevalence was highest among those aged 15-54 years (6.2%). Of 53 isolates; 5 were S. Enteritidis, 1 was S. Typhimurium. No S. Typhi was isolated. None of the risk factors were associated with carriage of NTS. All isolates were susceptible to all antibiotics tested, including ampicillin, chloramphenicol, ciprofloxacin and co-trimoxazole. Prevalence of fecal carriage was high in Kilifi, an area of low incidence of invasive NTS disease and was low in areas of higher incidence in Nairobi and Siaya. The age-prevalence, risk factors, geographical and serotype distribution of NTS in carriage differs from invasive disease.

Persistence and dynamic structures of diverse cephalosporinase genes in nontyphoidal Salmonella in cross-sectional surveillance in Taiwan

Nontyphoidal Salmonella (NTS) is a major foodborne pathogen causing from acute gastroenteritis to bacteraemia, particularly in paediatric and elderly patients. Antimicrobial resistance of NTS, especially resistance to extended-spectrum cephalosporins, has emerged over the past decades. Thirteen NTS isolates resistant to ceftriaxone or cefotaxime were collected from a teaching hospital in Taipei, and another three from a tertiary hospital, in New Taipei City, Taiwan, from September 2018 to December 2019. Ten other archived isolates from 2000 to 2017 were also obtained. Complete genomes of the 26 isolates were obtained. Serovars, sequence types, resistomes, genetic relatedness, and sequence comparison of plasmids were analyzed. Serogroups B, C2 and E were significantly associated with ampicillin resistance. Over 90% of these 26 isolates are susceptible to carbapenems and colistin. Genomic epidemiology of these isolates shows that blaCMY-2-harbouring isolates in different serovars were prevalent over two decades, presumably resulting from highly mobile IncI1 plasmid harbouring blaCMY-2. One type of the IncI1 plasmids contained a mobile element, IS26, which might be involved in the acquisition of antimicrobial resistance genes. Two emerging serovars, S. Goldcoast ST358 harbouring blaCTX-M-55 on IncHI2 plasmids and S. Anatum ST64 harbouring blaDHA-1 on IncA/C2 plasmids persisted in Taiwan, possibly through the clonal spread. Integration of complete or partial plasmid sequences into host chromosomes or multiplications of the antimicrobial resistance genes also appears to be mediated by IS26, in the two emerging clones. The dynamic movement of cephalosporinase genes mediated by IS26 in NTS is of great concern.

Genomic diversity and epidemiological significance of non-typhoidal Salmonella found in retail food collected in Norfolk, UK.

Non-typhoidal Salmonella (NTS) is a major cause of bacterial gastroenteritis. Although many countries have implemented whole genome sequencing (WGS) of NTS, there is limited knowledge on NTS diversity on food and its contribution to human disease. In this study, the aim was to characterise the NTS genomes from retail foods in a particular region of the UK and assess the contribution to human NTS infections. Raw food samples were collected at retail in a repeated cross-sectional design in Norfolk, UK, including chicken (n=311), leafy green (n=311), pork (n=311), prawn (n=279) and salmon (n=157) samples. Up to eight presumptive NTS isolates per positive sample underwent WGS and were compared to publicly available NTS genomes from UK human cases. NTS was isolated from chicken (9.6 %), prawn (2.9 %) and pork (1.3 %) samples and included 14 serovars, of which Salmonella Infantis and Salmonella Enteritidis were the most common. The S. Enteritidis isolates were only isolated from imported chicken. No antimicrobial resistance determinants were found in prawn isolates, whilst 5.1 % of chicken and 0.64 % of pork samples contained multi-drug resistant NTS. The maximum number of pairwise core non-recombinant single nucleotide polymorphisms (SNPs) amongst isolates from the same sample was used to measure diversity and most samples had a median of two SNPs (range: 0-251). NTS isolates that were within five SNPs to clinical UK isolates belonged to specific serovars: S. Enteritidis and S. Infantis (chicken), and S. I 4,[5],12:i- (pork and chicken). Most NTS isolates that were closely related to human-derived isolates were obtained from imported chicken, but further epidemiological data are required to assess definitively the probable source of the human cases. Continued WGS surveillance of Salmonella on retail food involving multiple isolates from each sample is necessary to capture the diversity of Salmonella and determine the relative importance of different sources of human disease.

Whole genome sequencing of Salmonella enterica serovars isolated from humans, animals, and the environment in Lagos, Nigeria

BackgroundSalmonella infections remain an important public health issue worldwide. Some serovars of non-typhoidal Salmonella (NTS) have been associated with bloodstream infections and gastroenteritis, especially in children in Sub-Saharan Africa with circulating S. enterica serovars with drug resistance and virulence genes. This study identified and verified the clonal relationship of Nigerian NTS strains isolated from humans, animals, and the environment.MethodsIn total, 2,522 samples were collected from patients, animals (cattle and poultry), and environmental sources between December 2017 and May 2019. The samples were subjected to a standard microbiological investigation. All the isolates were identified using Microbact 24E, and MALDI-TOF MS. The isolates were serotyped using the Kauffmann-White scheme. Antibiotic susceptibility testing was conducted using the disc diffusion method and the Vitek 2 compact system. Virulence and antimicrobial resistance genes, sequence type, and cluster analysis were investigated using WGS data.ResultsForty-eight (48) NTS isolates (1.9%) were obtained. The prevalence of NTS from clinical sources was 0.9%, while 4% was recorded for animal sources. The serovars identified were S. Cotham (n = 17), S. Give (n = 16), S. Mokola (n = 6), S. Abony (n = 4), S. Typhimurium (n = 4), and S. Senftenberg (n = 1). All 48 Salmonella isolates carried intrinsic and acquired resistant genes such as aac.6…Iaa, mdf(A), qnrB, qnrB19 genes and golT, golS, pcoA, and silP, mediated by plasmid Col440I_1, incFIB.B and incFII. Between 100 and 118 virulence gene markers distributed across several Salmonella pathogenicity islands (SPIs), clusters, prophages, and plasmid operons were found in each isolate. WGS revealed that strains of each Salmonella serovar could be assigned to a single 7-gene MLST cluster, and strains within the clusters were identical strains and closely related as defined by the 0 and 10 cgSNPs and likely shared a common ancestor. The dominant sequence types were S. Give ST516 and S. Cotham ST617.ConclusionWe found identical Salmonella sequence types in human, animal, and environmental samples in the same locality, which demonstrates the great potential of the applied tools to trace back outbreak strains. Strategies to control and prevent the spread of NTS in the context of one’s health are essential to prevent possible outbreaks.

Prevalence ofSalmonellain Stool During the Vaccine Impact on Diarrhea in Africa (VIDA) Study, 2015–2018

Non-typhoidal Salmonella (NTS) is a common cause of gastroenteritis in young children, with limited data on NTS serovars and antimicrobial resistance in Africa. We determined the prevalence of Salmonella spp. and frequency of antimicrobial resistance among serovars identified in stools of 0-59 month-old children with moderate-to-severe diarrhea (MSD) and controls enrolled in the Vaccine Impact on Diarrhea in Africa (VIDA) Study in The Gambia, Mali, and Kenya in 2015-2018, and compared with data from the Global Enteric Multicenter Study (GEMS; 2007-2010) and the GEMS-1A study (2011). Salmonella spp. was detected by quantitative real-time PCR (qPCR) and culture-based methods. Identification of serovars was determined by microbiological methods. By qPCR, the prevalence of Salmonella spp. among MSD cases was 4.0%, 1.6%, and 1.9% and among controls was 4.6%, 2.4%, and 1.6% in The Gambia, Mali, and Kenya, respectively, during VIDA. We observed year-to-year variation in serovar distribution and variation between sites. In Kenya, Salmonella enterica serovar Typhimurium decreased (78.1% to 23.1%; P < .001) among cases and controls from 2007 to 2018, whereas serogroup O:8 increased (8.7% to 38.5%; P = .04). In The Gambia, serogroup O:7 decreased from 2007 to 2018 (36.3% to 0%; P = .001) but S. enterica serovar Enteritidis increased during VIDA (2015 to 2018; 5.9% to 50%; P = .002). Only 4 Salmonella spp. were isolated in Mali during all 3 studies. Multidrug resistance was 33.9% in Kenya and 0.8% in The Gambia across all 3 studies. Ceftriaxone resistance was only observed in Kenya (2.3%); NTS isolates were susceptible to ciprofloxacin at all sites. Understanding variability in serovar distribution will be important for the future deployment of vaccines against salmonellosis in Africa.

Molecular Characterization of Non-typhoidal Salmonella (NTS) Isolated from Salad Vegetables in Terengganu, Malaysia

Salad vegetables are the important sources of vitamins and minerals for human diet. However, salad vegetables are potential vehicles for non-typhoidal Salmonella spp. (NTS) as reported in our previous study. Such contamination posed significant food poisoning risk to consumer. The aims of present study include determination of the virulence genes prevalence in NTS isolates in samples from retail markets and farms. Besides, characterization of NTS isolates was performed to determine their genetic relatedness. Multiplex PCR assay was done to detect the presence of 15 virulence genes in 58 NTS isolates. The genetic relatedness of 33 NTS belonging to S. Weltevreden, S. Albany, S. Hvittingfoss, S. Aberdeen, S. Poona and S. Corvallis were characterized using ERIC-PCR and BOX-PCR typing methods. Results showed the presence of 13 virulence genes (spiA, pagC, msgA, invA, sipB, prgH, spaN, orgA, tolC, sitC, lpfC, sifA and sopB) among all the isolates with 53 (91.38%) isolates carried more than 11 virulence genes, while other five isolates carried the genes in the range of six to nine types. None of the isolates possessed spvB and pefA genes. Major clusters were observed at a genetic distance percentage of 90% for both ERIC- and BOX-PCR with discriminatory index of 0.917 and 0.873, respectively. In terms of source and type of sample, all NTS isolates were found diverse without clear association, thus no specific cluster was found. In summary, this study demonstrated the potential risks of NTS from salad vegetables to cause foodborne diseases and they were commonly found to be related with regard to their specific serovars.

NON-TYPHOIDAL SALMONELLA: A HOSPITAL BASED STUDY FROM SOUTH INDIA

Background &amp; objectives: The objective of this study was to evaluate the prevalence of Non-typhoidal Salmonella and to nd their antibiotic susceptibility pattern in a tertiary care hospital in South India. A signicant global health issue is the steadily rising percentage of Non-typhoidal Salmonella (NTS) infections in people. A descriptive study was conducted at Methods: a tertiary care teaching hospital in South India. Culture and sensitivity of stool samples of clinically suspected patients were done in the Microbiology laboratory from Sree Gokulam Medical College and Research Foundation. All samples were inoculated onto appropriate culture plates. Colonies suspected as Salmonella were identied by standard laboratory methods, initially by manual biochemical tests and by the VITEK-2 automated systems (bioMérieux) and nal serotyping by polyvalent antisera. 3 of the Salmonella isolates were sent to CMC, Vellore, India for serotyping. Antibiotic susceptibility tests were performed by Kirby Bauer's disc diffusion method on Mueller-Hinton agar and results were interpreted as per the CLSI guidelines (2022). Signed informed consent was obtained from all participants. Tests were performed in the clinical Microbiology Laboratory under the Department of Microbiology, Sree Gokulam Medical College and Research Foundation, Venjaramoodu, Trivandrum. Of the 244 mot Results: ion samples, Non-typhoidal Salmonella isolated were from 20 motion samples. The predominant serotype isolated was Salmonella Typhimurium (S. Typhimurium) in 16(80%) followed by Salmonella enteritidis in 3(15%) and Salmonella C2 in 1(5%) isolates. It was noticed by an increasing trend of resistance to Ampicillin, Chloramphenicol, Cephalosporins (Third generation) and Quinolones over this 18 month study. Based on this study, Conclusions: faecal prevalence of NTS (8.20%) were increasing among motion samples. Majority of isolates were from females (75%) with a mean age group belonging to Adults (46-60yrs). Except for Ampicillin and Cotrimoxazole, NTS isolates exhibited high rates of resistance to rst-line antibiotics. The gradual but consistent increase in resistance to Ampicillin, Fluoroquinolones, third generation Cephalosporins may restrict future treatment 1 options. Hence periodic monitoring of NTS infections, serotype distribution and antimicrobial resistance trend is recommended .

Evaluation of Intervention Measures on Controlling the Dissemination of Nontyphoidal Salmonella Disease in Mukuru Informal Settlement, Nairobi County, Kenya.

Nontyphoidal Salmonella is the most common bacterial pathogen causing gastrointestinal infection worldwide. Data is limited on the effectiveness of the intervention measures put in place to help control the dissemination of nontyphoidal Salmonella disease on Mukuru informal settlement in Nairobi County, Kenya. The aim of the study was to determine the effectiveness of the intervention measures put in place to prevent and control the dissemination of nontyphoidal Salmonella disease in Mukuru informal settlement in Nairobi County, Kenya. A cross-sectional study was conducted in patients aged 0-5 years. Nontyphoidal Salmonella (NTS) bacteria was cultured from blood and stool collected from the recruited children who reported at three health facilities with symptoms of diarrhea, fever or vomiting and antimicrobial susceptibility testing of the recovered NTS isolates from the stool and blood samples was performed. A questionnaire was administered to obtain relevant demographic, socio-economic and healthcare utilization information. Fisher’s test was conducted to determine the difference in the susceptibility patterns between the isolated NTS. Out of 191 collected samples, 3 were found to be positive for Salmonella Typhimurium and Salmonella Enteritidis. Both S. Typhimurium and S. Enteritidis isolates were resistant to gentamycin. Salmonella Typhimurium was found also to be resistant to tetracycline drug. Significant differences existed between some of the drugs susceptibility patterns (p= 0.0048). There are still AMR strains circulating in Mukuru informal settlement. There is still need for the Kenyan government to strengthen knowledge and understanding of AMR through supporting surveillance and research.

Physiological characteristics and virulence gene composition of selected serovars of seafood-borne Salmonella enterica.

All serotypes of Salmonella enterica are considered potentially pathogenic. However, the non-typhoidal Salmonella (NTS) serotypes vary considerably in terms of pathogenicity and the severity of infections. Although diverse serotypes of NTS have been reported from tropical seafood, their sources, physiological characteristics, and virulence potentials are not well understood. This study aimed to compare the physiological characteristics of selected serovars of Salmonella from seafood and investigate possible variations in the distribution of known genes within the pathogenicity islands. A series of biochemical tests, including carbohydrate fermentation and amino acid decarboxylation tests were performed to physiologically compare the isolates. The genetic characterization with respect to putative virulence genes was done by screening for genes associated with Salmonella pathogenicity island (SPI) I-V, as well as the toxin- and prophage-associated genes by polymerase chain reaction. Irrespective of serotypes, all the isolates uniformly harbored the five SPIs screened in this study. However, some virulence genes, such as the avrA, sodC, and gogB were not detected in all Salmonella isolates. The biochemical profiles of Salmonella serotypes were highly conserved except for variations in inositol fermentation and citrate utilization. All the isolates of this study were weak biofilm formers on polystyrene surfaces. The pathogenicity profiles of environmental NTS isolates observed in this study suggest that they possess the virulence machinery necessary to cause human infections and therefore, urgent measures to contain Salmonella contamination of seafood are required to ensure the safety of consumers.

Multicenter Surveillance of Antimicrobial Resistance among Gram-Negative Bacteria Isolated from Bloodstream Infections in Ghana

Antimicrobial resistance (AMR) in Gram-negative bacteria-causing bloodstream infections (BSIs), such as Klebsiella pneumoniae and non-typhoidal Salmonella (NTS), is a major public health concern. Nonetheless, AMR surveillance remains scarce in sub-Saharan Africa, where BSI treatment is largely empirical. The aim of the study was to determine the distribution and AMR patterns of BSI-causing NTS, K. pneumoniae, and other Gram-negative bacteria in Ghana. A cross-sectional study was conducted between April and December 2021 at eleven sentinel health facilities across Ghana as part of a pilot study on the feasibility and implementation of the human sector AMR surveillance harmonized protocol in sub-Saharan Africa. Gram-negative bacteria recovered from blood specimens of febrile patients were identified using MALDI-TOF and evaluated for antimicrobial resistance using the BD Phoenix M50 analyzer and Kirby-Bauer disc diffusion. The Department of Medical Microbiology at the University of Ghana served as the reference laboratory. Out of 334 Gram-negative blood isolates, there were 18 (5.4%) NTS, 85 (25.5%) K. pneumoniae, 88 (26.4%) Escherichia coli, 40 (12.0%) Acinetobacter baumannii, 25 (7.5%) Pseudomonas aeruginosa, and 77 (23.1%) other Gram-negative bacteria. As a composite, the isolates displayed high resistance to the antibiotics tested-amoxicillin (89.3%), tetracycline (76.1%), trimethoprim-sulfamethoxazole (71.5%), and chloramphenicol (59.7%). Resistance to third-generation cephalosporins [ceftriaxone (73.7%), cefotaxime (77.8%), and ceftazidime (56.3%)] and fluoroquinolones [ciprofloxacin (55.3%)] was also high; 88% of the isolates were multidrug resistant, and the rate of extended-spectrum beta-lactamase (ESBL) production was 44.6%. Antibiotic resistance in K. pneumoniae followed the pattern of all Gram-negative isolates. Antibiotic resistance was lower in NTS blood isolates, ranging between 16.7-38.9% resistance to the tested antibiotics. Resistance rates of 38.9%, 22.2%, and 27.8% were found for cefotaxime, ceftriaxone, and ceftazidime, respectively, and 27.8% and 23.8% for ciprofloxacin and azithromycin, respectively, which are used in the treatment of invasive NTS. The prevalence of multidrug resistance in NTS isolates was 38.9%. Multicenter AMR surveillance of Gram-negative blood isolates from febrile patients was well-received in Ghana, and the implementation of a harmonized protocol was feasible. High resistance and multidrug resistance to first- or second-choice antibiotics, including penicillins, third-generation cephalosporins, and fluoroquinolones, were found, implying that these antibiotics might have limited effectiveness in BSI treatment in the country. Continuation of AMR surveillance in Gram-negative blood isolates is essential for a better understanding of the extent of AMR in these pathogens and to guide clinical practice and policymaking.