Two birds with one stone: SGI1 can stabilize itself and expel the IncC helper by hijacking the plasmid parABS system.

The SGI1 family integrative mobilizable elements, which are efficient agents in distribution of multidrug resistance in Gammaproteobacteria, have a complex, parasitic relationship with their IncC conjugative helper plasmids. Besides exploiting the transfer apparatus, SGI1 also hijacks IncC plasmid control mechanisms to time its own excision, replication and expression of self-encoded T4SS components, which provides advantages for SGI1 over its helpers in conjugal transfer and stable maintenance. Furthermore, SGI1 destabilizes its helpers in an unknown, replication-dependent way when they are concomitantly present in the same host. Here we report how SGI1 exploits the helper plasmid partitioning system to displace the plasmid and simultaneously increase its own stability. We show that SGI1 carries two copies of sequences mimicking the parS sites of IncC plasmids. These parS-like elements bind the ParB protein encoded by the plasmid and increase SGI1 stability by utilizing the parABS system of the plasmid for its own partitioning, through which SGI1 also destabilizes the helper plasmid. Furthermore, SGI1 expresses a small protein, Sci, which significantly strengthens this plasmid-destabilizing effect, as well as SGI1 maintenance. The plasmid-induced replication of SGI1 results in an increased copy-number of parS-like sequences and Sci expression leading to strong incompatibility with the helper plasmid.

Mobilome-driven partitions of the resistome in Salmonella.

IMPORTANCE: Antimicrobial resistance (AMR) has become a significant global challenge, with an estimated 10 million deaths annually by 2050. The emergence of AMR is mainly attributed to mobile genetic elements (MGEs or mobilomes), which accelerate wide dissemination among pathogens. The interaction between mobilomes and AMR genes (or resistomes) in Salmonella, a primary cause of diarrheal diseases that results in over 90 million cases annually, remains poorly understood. The available fragmented or incomplete genomes remain a significant limitation in investigating the relationship between AMR and MGEs. Here, we collected the most extensive closed Salmonella genomes (n = 1,817) from various sources across 58 countries. Notably, our results demonstrate that resistome transmission between Salmonella lineages follows a specific pattern of MGEs and is influenced by external drivers, including certain socioeconomic factors. Therefore, targeted interventions are urgently needed to mitigate the catastrophic consequences of Salmonella AMR.

Antimicrobial resistance and genomic investigation of non-typhoidal Salmonella isolated from outpatients in Shaoxing city, China.

Human non-typhoidal salmonellosis is among the leading cause of morbidity and mortality worldwide, resulting in huge economic losses and threatening the public health systems. To date, epidemiological characteristics of non-typhoidal Salmonella (NTS) implicated in human salmonellosis in China are still obscure. Herein, we investigate the antimicrobial resistance and genomic features of NTS isolated from outpatients in Shaoxing city in 2020. Eighty-seven Salmonella isolates were recovered and tested against 28 different antimicrobial agents, representing 12 categories. The results showed high resistance to cefazolin (86.21%), streptomycin (81.61%), ampicillin (77.01%), ampicillin-sulbactam (74.71%), doxycycline (72.41%), tetracycline (71.26%), and levofloxacin (70.11%). Moreover, 83.91% of isolates were resistant to ≥3 categories, which were considered multi-drug resistant (MDR). Whole-genome sequencing (WGS) combined with bioinformatic analysis was used to predict serovars, MLST types, plasmid replicons, antimicrobial resistance genes, and virulence genes, in addition to the construction of phylogenomic to determine the epidemiological relatedness between isolates. Fifteen serovars and 16 STs were identified, with the dominance of S. I 4, [5], 12:i:- ST34 (25.29%), S. Enteritidis ST11 (22.99%), and S. Typhimurium ST19. Additionally, 50 resistance genes representing ten categories were detected with a high prevalence of aac(6')-Iaa (100%), bla TEM-1B (65.52%), and tet(A) (52.87%), encoding resistance to aminoglycosides, ß-lactams, and tetracyclines, respectively; in addition to chromosomic mutations affecting gyrA gene. Moreover, we showed the detection of 18 different plasmids with the dominance of IncFIB(S) and IncFII(S) (39.08%). Interestingly, all isolates harbor the typical virulence genes implicated in the virulence mechanisms of Salmonella, while one isolate of S. Jangwani contains the cdtB gene encoding typhoid toxin production. Furthermore, the phylogenomic analysis showed that all isolates of the same serovar are very close to each other and clustered together in the same clade. Together, we showed a high incidence of MDR among the studied isolates which is alarming for public health services and is a major threat to the currently available treatments to deal with human salmonellosis; hence, efforts should be gathered to further introduce WGS in routinely monitoring of AMR Salmonella in the medical field in order to enhance the effectiveness of surveillance systems and to limit the spread of MDR clones.

Higher tolerance of predominant Salmonella serovars circulating in the antibiotic-free feed farms to environmental stresses.

To counteract the dramatic increase in antibiotic-resistant bacterial pathogens, many countries, including China, have banned the use of antibiotic-supplemented feed for farming animals. However, the exact consequences of this policy have not been systematically evaluated. Therefore, Salmonella isolates from farms that ceased using antibiotics 1-5 years ago were compared with isolates from farms that continue to use antimicrobials as growth promotors. Here, we used whole-genome sequencing combined with in-depth phenotypic assays to investigate the ecology, epidemiology, and persistence of multi-drug resistant (MDR) Salmonella from animal farms during the withdrawal of antibiotic growth promotors. Our results showed that the prevalence of Salmonella was significantly lower in antibiotic-free feed (AFF) farms compared to conventional-feed (CF) farms, even though all isolates obtained from AFF farms were MDR (>5 classes) and belonged to well-recognized predominant serovars. The additional phylogenomic analysis combined with principal component analysis showed high similarity between the predominant serovars in AFF and CF farms. This result raised questions regarding the environmental persistence capabilities of MDR strain despite AFF policy. To address this question, a representative panel of 20 isolates was subjected to disadvantageous environmental stress assays. These results showed that the predominant serovars in AFF and CF farms were more tolerant to stress conditions than other serovars. Collectively, our findings suggest that AFF helps eliminate only specific MDR serovars, and future guiding policies would benefit by identifying predominant Salmonella clones in problematic farms to determine the use of AFF and additional targeted interventions.

Bacteriological Survey of Fresh Minced Beef on Sale at Retail Outlets in Scotland in 2019: Three Foodborne Pathogens, Hygiene Process Indicators, and Phenotypic Antimicrobial Resistance.

ABSTRACT: The health and economic burden of foodborne illness is high, with approximately 2.4 million cases occurring annually in the United Kingdom. A survey to understand the baseline microbial quality and prevalence of food-related hazards of fresh beef mince on retail sale could inform risk assessment, management, and communication to ensure the safety of this commodity. In such a survey, a two-stage sampling design was used to reflect variations in population density and the market share of five categories of retail outlets in Scotland. From January to December 2019, 1,009 fresh minced beef samples were collected from 15 geographic areas. The microbial quality of each sample was assessed using aerobic colony count and Escherichia coli count. Samples were cultured for Campylobacter and Salmonella, and PCR was used to detect target genes (stx1 all variants, stx2 a to g, and rfbO157) for Shiga toxin-producing E. coli (STEC). The presence of viable E. coli O157 and STEC in samples with a positive PCR signal was confirmed via culture and isolation. Phenotypic antimicrobial sensitivity patterns of cultured pathogens and 100 E. coli isolates were determined, mostly via disk diffusion. The median aerobic colony count and E. coli counts were 6.4 × 105 (interquartile range, 6.9 × 104 to 9.6 × 106) and <10 CFU/g (interquartile range, <10 to 10) of minced beef, respectively. The prevalence was 0.1% (95% confidence interval [CI], 0 to 0.7%) for Campylobacter, 0.3% (95% CI, 0 to 1%) for Salmonella, 22% (95% CI, 20 to 25%) for PCR-positive STEC, and 4% (95% CI, 2 to 5%) for culture-positive STEC. The evidence for phenotypic antimicrobial resistance detected did not give cause for concern, mainly occurring in a few E. coli isolates as single nonsusceptibilities to first-line active substances. The low prevalence of pathogens and phenotypic antimicrobial resistance is encouraging, but ongoing consumer food safety education is necessary to mitigate the residual public health risk.

Mathematical Modelling Highlights the Potential for Genetic Manipulation as an Adjuvant to Counter Efflux-Mediated MDR in Salmonella.

Bacteria have developed resistance to antibiotics by various mechanisms, notable amongst these is the use of permeation barriers and the expulsion of antibiotics via efflux pumps. The resistance-nodulation-division (RND) family of efflux pumps is found in Gram-negative bacteria and a major contributor to multidrug resistance (MDR). In particular, Salmonella encodes five RND efflux pump systems: AcrAB, AcrAD, AcrEF, MdsAB and MdtAB which have different substrate ranges including many antibiotics. We produce a spatial partial differential equation (PDE) model governing the diffusion and efflux of antibiotic in Salmonella, via these RND efflux pumps. Using parameter fitting techniques on experimental data, we are able to establish the behaviour of multiple wild-type and efflux mutant Salmonella strains, which enables us to produce efflux profiles for each individual efflux pump system. By combining the model with a gene regulatory network (GRN) model of efflux regulation, we simulate how the bacteria respond to their environment. Finally, performing a parameter sensitivity analysis, we look into various different targets to inhibit the efflux pumps. The model provides an in silico framework with which to test these potential adjuvants to counter MDR.

Clinically healthy household dogs and cats as carriers of multidrug-resistant Salmonella enterica with variable R plasmids.

Introduction. Antimicrobial resistance (AMR) is a One Health issue concerning humans, animals and the environment and a unified One Health approach is required to contain this problematic issue. Dogs and cats are popular pet animals and are known to carry many bacterial pathogens that are of public health importance, including Salmonella. However, data on AMR in companion animals is limited.Gap statement. Scant AMR data from bacteria originating from companion animals limits an accurate assessment of the impacts of pet-animal-related AMR on public health.Purpose. This study aimed to phenotypically and genetically investigate AMR in Salmonella isolated from pet dogs and cats in Thailand.Methodology. Salmonella enterica were isolated from pet dogs (n=159) and cats (n=19) in Thailand between 2016 and 2019. All isolates were serotyped. Phenotypic and genotypic antimicrobial resistance was examined. PCR-based replicon typing, replicon sequence typing and plasmid multilocus sequence typing were conducted to characterize plasmids.Results. Seventy-seven serovars were identified, with serovars Weltevreden (9.6%) and Stockholm (9.0%) the most common. Most of the isolates (34.3%) were multidrug-resistant. The serovar Stockholm was an ESBL-producer and carried the ß-lactamase genes bla TEM-1 and bla CTX-M-55. The plasmid-mediated quinolone resistance (PMQR) gene, qnrS, was also detected (10.1%). Class 1 integrons carrying the dfrA12-aadA2 cassette array were most frequent (45.9%). Five plasmid replicon types as IncA/C (0.6%), N (1.1%), IncFIIA (28.7%), IncHI1 (2.2%), and IncI1 (3.4%) were identified. Based on the pMLST typing scheme (n=9), plasmids were assigned into five different STs including IncA/C-ST6 (n=1), IncH1-ST16 (n=4), IncI1-ST3 (n=1), IncI1-ST60 (n=1) and IncI1-ST136 (n=1). The ST 16 of IncHI1 plasmid was a novel plasmid ST. Subtyping F-type plasmids using the RST scheme (n=9) revealed four different combinations of replicons including S1:A-:B- (n=4), S1:A-:B22 (n=2), S3:A-:B- (n=1) and S-:A-:B47 (n=1).Conclusions. Our findings highlight the role of clinically healthy household dogs and cats as carriers of AMR Salmonella strains with different R plasmid. The implementation of AMR phenotypes instigation and genotypic monitoring and surveillance programmes in companion animals are imperative as integral components of the One Health framework.

Isolation, antimicrobial susceptibility patterns, and risk factors assessment of non-typhoidal Salmonella from apparently healthy and diarrheic dogs.

BACKGROUND: Dogs are one of the important asymptomatic carriers of antimicrobial resistant and potentially pathogenic strains of Salmonella. They can harbor large bacterial load in the intestines and mesenteric lymph nodes which can be shed in their feces with the possibility of transmission to humans. Therefore, a cross-sectional study was conducted with the objectives of estimating the prevalence of non-typhoidal Salmonella, assessing the risk factors for dog's Salmonella carriage, and profiling the antimicrobial resistance pattern of Salmonella isolates among housed dogs in Harar town, Eastern Ethiopia. A total of 415 rectal swab samples were collected from randomly selected dogs. Samples were examined for non-typhoidal Salmonella using standard bacteriologic culture and biochemical tests. The disk diffusion method (Kirby-Bauer test) was employed to evaluate the isolates for their susceptibility against five antimicrobials. RESULTS: Non-typhoidal Salmonella were isolated from 26 (6.3%) of the rectal swab samples, with significantly higher occurrence in diarrheic (15.2%) than non-diarrheic (5.5%) dogs. The risk of Salmonella harboring was significantly higher in female dogs than in male dogs (OR = 2.5, p = 0.027). Dogs fecal shedding of Salmonella was relatively higher in households who used offal as a main feed type for their dogs (23.1%; 95% CI = 5-53.8) than those who used leftover food (10.1%; 95% CI = 5.7-16.1) and practiced mixed feeding system (17%; 95% CI = 7.6-30.8). Salmonella isolates showed higher resistance to ampicillin (41.7%), while all isolates were fully susceptible to gentamicin. Moreover, 58.3% of Salmonella isolates showed resistance to at least one of the tested antimicrobials. Majorities (72.7%) of the dog owners had no awareness on the risk of zoonotic salmonellosis from dog and all of the respondents use bare hand to clean dog kennel. CONCLUSION: Our study reveals the importance of both diarrheic and apparently healthy housed dogs in the harboring and shedding of antimicrobial resistant non-typhoidal Salmonella. The risk of non-typhoidal Salmonella spread among pet owners is not negligible, especially in households who use offal as main feed type. Therefore, an integrated approach such as: proper dog handling practices; continuous evaluation of antimicrobial resistance; and rational use of antimicrobials in the field of veterinary sector are necessary to tackle the problem.

Isolation and Sequencing of the First Case of Symptomatic MDR Salmonella enterica Subsp. Enterica ST40 in Human in Italy, July 2020.

Strains of drug-resistant nontyphoidal Salmonella spp. are emerging in livestock worldwide. We describe the first case of symptomatic multidrug-resistant (MDR) Salmonella enterica subsp. enterica in human and the genetic mechanisms at the basis of its antibiotic resistance. To control outbreaks, rapid identification and sequencing are necessary. Proactive research and notification are needed to evaluate the routes of transmission from livestock to humans and risk-management strategies of MDR Salmonella strains.

In Vitro Susceptibility of Typhoidal, Nontyphoidal, and Extended-Spectrum-ß-Lactamase-Producing Salmonella to Ceftolozane/Tazobactam.

Both typhoidal and nontyphoidal salmonellae are included in the top 15 drug-resistant threats described by the U.S. Centers for Disease Control and Prevention. There is an urgent need to look for alternative antibiotics for the treatment of Salmonella infections. We used the broth microdilution test to examine the in vitro susceptibilities of typhoidal and nontyphoidal salmonellae, including isolates positive for extended-spectrum ß-lactamase (ESBL), to ceftolozane/tazobactam and six other antibiotics. Of the 313 (52 typhoidal and 261 nontyphoidal) Salmonella isolates tested, 98.7% were susceptible to ceftolozane/tazobactam. Based on the overall MIC50/90 values, Salmonella isolates were more susceptible to ceftolozane/tazobactam (0.25/0.5 mg/L) than all the comparator agents: ampicillin (≥64/≥64 mg/L), levofloxacin (0.25/1 mg/L), azithromycin (4/16 mg/L), ceftriaxone (≤0.25/4 mg/L), chloramphenicol (8/≥64 mg/L), and trimethoprim/sulfamethoxazole (1/≥8 mg/L). Comparison of the activities of the antimicrobial agents against nontyphoidal Salmonella isolates according to their serogroups showed that ceftolozane/tazobactam had the highest activity (100%) against Salmonella serogroup D, G, I, and Q isolates, whereas the lowest activity (85.7%) was observed against serogroup E isolates. All 10 ESBL-producing Salmonella isolates (all nontyphoidal), of which 8 were CTX-M-55 producers and 2 were CTX-M-65 producers, were sensitive to ceftolozane/tazobactam, albeit with MIC50/90 values higher (1/2 mg/L) than those for non-ESBL producers (0.25/0.5 mg/L). In summary, our data indicate that ceftolozane/tazobactam is active against most strains of both typhoidal and nontyphoidal salmonellae and also against ESBL-producing salmonellae.

Microbiota transplantation from younger to older mice could restore lost immunity to effectively clear salmonella infection in Th2-biased BALB/c mice.

AIMS: The composition, overtly abundance, and diversity of gut microbiota, play a significant role in maintaining physiological homeostasis with age. Reports revealed that the gut microbial profile might be correlated with immunity and metabolism. It is, therefore, tantamount to know if an older individual can achieve the immunity and metabolic profile of a younger individual by receiving the gut microbiome of a younger individual. In the current report, we have studied the effects of cecal microbiota transplantation (CMT) from younger to older mice. MATERIALS AND METHODS: In this study, older BALB/c mice (23 weeks) received CMT from younger BALB/c mice (3 weeks). KEY FINDINGS: CMT recipient mice showed altered expressions of immune and tight junction protein genes in the colon of mice, while the non-CMT recipient mice did not. Older mice were treated with AVNM to make them compatible with CMT. Further data from metabolite studies revealed that AVNM treatment mainly affected the aromatic amino acid biosynthesis pathway while CMT mostly affected the metabolism of different carbohydrates. We repeated the analysis in C57BL/6 mice without any significant effects of CMT. SIGNIFICANCE: Results revealed that mice who received CMT showed more efficient restoration of gut microbiota than non-CMT recipient mice. CMT caused the alleviation of Salmonella infection and efficient recovery of the cecal index in the mice following antibiotics treatment.

First Report: Colistin Resistance Gene mcr-3.1 in Salmonella enterica Serotype Choleraesuis Isolated from Human Blood Sample from Thailand.

This study describes the first finding of Salmonella enterica serotype Choleraesuis (Salmonella Choleraesuis) isolate harboring mobile colistin resistance (mcr)-3.1 obtained from human blood sample. The clinical relevant blood sample was collected during October 2018. The phenotypic identification and antimicrobial susceptibility testing (AST) were studied by using automate microbiology platform (Phoenix M50, BD), and in-depth characterization by whole genome sequencing. The phenotypic identification was reported Salmonella Choleraesuis. AST result demonstrated that this isolate had high minimum inhibitory concentrations (MICs) against colistin, fluoroquinolone, and cephalosporin III and IV, which are first-line antibiotic treatment choices for Gram-negative bacterial pathogen infections. This Salmonella Choleraesuis is harboring mcr-3.1 and presented a diversity carbapenemase including blaTEM and blactx-m-55. Regarding the multilocus sequence typing result, this Salmonella presented ST139 that related to the Choleraesuis variant sensu stricto. Swine is not the host specific for the Salmonella Choleraesuis since it also causes enteric and other diseases in human. Hence, the presence of the mobile plasmid colistin mcr-3.1 resistant gene in human sample is resulting to the public health concerns due to the fact that it is enable to transmit to other hosts and distribute into an environment.

[Analysis on epidemiological characteristics of multidrug-resistant Salmonella Kentucky in Beijing, 2010-2020].

Objective: To investigate the epidemiological, drug resistance and molecular characteristics of Salmonella (S.) Kentucky strains isolated from diarrheal patients in Beijing. Methods: The drug susceptibility of 22 S. Kentucky strains isolated in Beijing during 2010-2020 was tested by using the micro broth dilution method. The multilocus sequence typing (MLST), drug resistance genes and Salmonella genomic island (SGI) identifications of the strains were performed by whole-genome sequencing (WGS).The pulsed field gel electrophoresis (PFGE) was performed to analyze the molecular epidemiological characteristics of the isolates. Results: The 22 strains were highly resistant to 8-22 kinds of antibiotics, especially to ciprofloxacin, cephalosporins and azithromycin, etc., showing a super high level of multidrug resistance and 21 strains were positive for extended-spetrum beta-lactamase (ESBL). The WGS analysis revealed that all the isolates belonged to ST198, carrying SGI1-K. The drug resistance genes tetA, sul1 and qacE were identified in all strains and Quinolone resistance-determining regions (QRDRs) showed 2 mutations in gyrA (S83F, D87 N) and 3 mutations in the parC gene (T57S, S80I, T255S). The resistance genes associated with ß-lactam antibiotics (blaCTX-M-55, blaCTX-M-14b, blaTEM-141, blaTEM-206, blaTEM-209, blaTEM-214, blaTEM-1B), resistance genes associated with aminoglycosides [aac(3)-Id, aac(3)-IId, aac(6')-Iaa, aadA7, aadA17, aph(3')-Ia, aph(3'')-Ib, aph(6)-Id,rmtB] as well as floR, dfrA14, mphA and qnrS1 had significant differences in the strains of different years, which were highly consistent with the drug-resistant phenotype. Furthermore, phylogenetic analysis showed that the similarity of the 22 strains was more than 85%, and the strains were highly homologous to CIP-resistant ST198-X1 circulating in the world. In the process of spread, the drug resistance and PFGE spectrums had changed, two clusters had formed. Conclusions: The S. Kentucky strains isolated in Beijing shared high homology with the multidrug-resistant strain ST198-X1-SGI-1K isolated in the world, which has maintained a low level of spread since 2016, causing sporadic infections and clusters of diarrhea, and has serious resistances to fluoroquinolones, ESBLs and azithromycin. The surveillance for multidrug-resistant S. Kentucky should be strengthened.

Using whole-genome sequence data to examine the epidemiology of Salmonella, Escherichia coli and associated antimicrobial resistance in raccoons (Procyon lotor), swine manure pits, and soil samples on swine farms in southern Ontario, Canada.

To better understand the contribution of wildlife to the dissemination of Salmonella and antimicrobial resistance in Salmonella and Escherichia coli, we examined whole-genome sequence data from Salmonella and E. coli isolates collected from raccoons (Procyon lotor) and environmental sources on farms in southern Ontario. All Salmonella and phenotypically resistant E. coli collected from raccoons, soil, and manure pits on five swine farms as part of a previous study were included. We assessed for evidence of potential transmission of these organisms between different sources and farms utilizing a combination of population structure assessments (using core-genome multi-locus sequence typing), direct comparisons of multi-drug resistant isolates, and epidemiological modeling of antimicrobial resistance (AMR) genes and plasmid incompatibility (Inc) types. Univariable logistic regression models were fit to assess the impact of source type, farm location, and sampling year on the occurrence of select resistance genes and Inc types. A total of 159 Salmonella and 96 resistant E. coli isolates were included. A diversity of Salmonella serovars and sequence types were identified, and, in some cases, we found similar or identical Salmonella isolates and resistance genes between raccoons, soil, and swine manure pits. Certain Inc types and resistance genes associated with source type were consistently more likely to be identified in isolates from raccoons than swine manure pits, suggesting that manure pits are not likely a primary source of those particular resistance determinants for raccoons. Overall, our data suggest that transmission of Salmonella and AMR determinants between raccoons and swine manure pits is uncommon, but soil-raccoon transmission appears to be occurring frequently. More comprehensive sampling of farms, and assessment of farms with other livestock species, as well as additional environmental sources (e.g., rivers) may help to further elucidate the movement of resistance genes between these various sources.

A systemic review of literatures on human Salmonella enterica serovars in Nigeria (1999-2018).

INTRODUCTION: Salmonella infections are endemic in Nigeria. There is lack of reliable data on culture-positive Salmonella with national coverage. This systemic review of literatures was undertaken to aggregate data on culture proven cases of human Salmonellae and to determine the prevailing serotypes for disease burden estimations. METHODOLOGY: This involved comprehensive search engines of Pubmed, Google Scholar, Google and Embase for the literatures on culture positive human Salmonellae from 1999-2018. This review documented the prevalence, common Salmonella serotypes. antibiotic resistance and risk factors associated with human Salmonella infections. RESULTS: This study revealed that 21out of 36 States in Nigeria reported Salmonella-associated diseases, spanning the six geopolitical zones. Our study revealed prevalence of 1.9% (2,732/143,756) Salmonella-bacteraemia and 16.3% (1,967/12,081) Salmonella-associated gastroenteritis. Fifty-three 53 Salmonella serotypes were identified. 39 serotypes were associated with Salmonella-bacteraemia and 31 serotypes with Salmonella-gastroenteritis. Salmonella typhi remains the commonest serotype accounting for 85.2% for Salmonella-bacteraemia and 73.1% Salmonella-gastroenteritis. S. typhimurium (3.8%) was mostly implicated invasive non-typhoidal serotype followed S. enteritidis (2.8%) among others. Human Immunodeficiency Virus-infected individuals, malnutrition was among factors predisposing Salmonella infections. Over 60% of the reported Salmonella isolates developed resistance to two or more of 23 antibiotics recorded, mostly ampicillin, cotrimoxazole, tetracycline and amoxicillin. CONCLUSIONS: This study revealed 39 Invasive and 31 non-invasive Salmonella serotypes. Ampicillin, cotrimoxazole, amoxicillin-clavulanate and tetracycline are the most frequently reported antibiotics resisted by Salmonella isolates. This antimicrobial resistance exhibited poses a threat to public health. Data generated from this review would serve as a baseline information for future surveillance studies.

Salmonella from Farm to Table: Isolation, Characterization, and Antimicrobial Resistance of Salmonella from Commercial Broiler Supply Chain and Its Environment.

Antimicrobial resistance (AMR) in poultry production chain is one of the major food safety concerns due to indiscriminate usage of antibiotics and the presence of pathogens such as Salmonella which causes infections in various stages of production. In the present study, 182 samples were collected from commercial broiler supply chain, viz., three hatcheries (n = 29), three commercial broiler farms (CBF; n = 99), and three retail meat shops (RMS; n = 54), and used for isolation and identification of Salmonella using three different selective agar media and a selective enrichment medium followed by PCR confirmation targeting the hilA gene. The overall prevalence of Salmonella was 47/182 (25.82%), and a significantly higher (P < 0.05) prevalence was observed in retail meat shops (46.29%), CBF (19.19%), and hatcheries (10.34%). Comparison of three agar media for isolation of Salmonella revealed that all the media were equally selective. However, PCR amplification of hilA gene fragment was significantly higher (P < 0.01) in selective enrichment culture tetrathionate brilliant green bile broth (TTB) as compared to all solid (agar-based) media. Susceptibility pattern against most frequently used antibiotics revealed that 100% of the isolates were resistant to at least one antibiotic. High resistance was observed for doxycycline (94.34%), followed by cefpodoxime (84.91%), ciprofloxacin (72.64%), gentamicin (65.09%), enrofloxacin (61.32%), colistin sulphate (40.42%), amikacin (34.91%), ampicillin (33.96%), neomycin (33.02), cefotaxime (30.19%), ceftazidime (29.25%), trimethoprim-sulfamethoxazole (23.58%), amoxicillin+clavulanic acid (21.70%), and chloramphenicol (12.26%); 16.98% of the isolates were ex-tended spectrum ß-lactamase (ESBL) producers, and 76.41% were multidrug resistant (MDR). MDR Salmonella were significantly higher (P < 0.01) in RMS (91.66%) followed by CBF (82.75%), whereas no MDR isolates were present in the isolates from hatcheries. The results indicated a higher prevalence of Salmonella and AMR for commonly used antibiotics in the complete broiler supply chain, especially RMS and CBF. Also, this study idicated that TTB enrichment followed by PCR and colony PCR was found to be rapid, specific and time-saving method.

Multidrug Resistance Dynamics in Salmonella in Food Animals in the United States: An Analysis of Genomes from Public Databases.

The number of bacterial genomes deposited each year in public databases is growing exponentially. However, efforts to use these genomes to track trends in antimicrobial resistance (AMR) have been limited thus far. We used 22,102 genomes from public databases to track AMR trends in nontyphoidal Salmonella in food animals in the United States. In 2018, genomes deposited in public databases carried genes conferring resistance, on average, to 2.08 antimicrobial classes in poultry, 1.74 in bovines, and 1.28 in swine. This represents a decline in AMR of over 70% compared to the levels in 2000 in bovines and swine, and an increase of 13% for poultry. Trends in resistance inferred from genomic data showed good agreement with U.S. phenotypic surveillance data (weighted mean absolute difference ± standard deviation, 5.86% ± 8.11%). In 2018, resistance to 3rd-generation cephalosporins in bovines, swine, and poultry decreased to 9.97% on average, whereas in quinolones and 4th-generation cephalosporins, resistance increased to 12.53% and 3.87%, respectively. This was concomitant with a decrease of blaCMY-2 but an increase in blaCTX-M-65 and gyrA D87Y (encoding a change of D to Y at position 87). Core genome single-nucleotide polymorphism (SNP) phylogenies show that resistance to these antimicrobial classes was predominantly associated with Salmonella enterica serovar Infantis and, to a lesser extent, S. enterica serovar Typhimurium and its monophasic variant I 4,[5],12:i:-, whereas quinolone resistance was also associated with S. enterica serovar Dublin. Between 2000 and 2018, trends in serovar prevalence showed a composition shift where S. Typhimurium decreased while S. Infantis increased. Our findings illustrate the growing potential of using genomes in public databases to track AMR in regions where sequencing capacities are currently expanding. IMPORTANCE Next-generation sequencing has led to an exponential increase in the number of genomes deposited in public repositories. This growing volume of information presents opportunities to track the prevalence of genes conferring antimicrobial resistance (AMR), a growing threat to the health of humans and animals. Using 22,102 public genomes, we estimated that the prevalence of multidrug resistance (MDR) in the United States decreased in nontyphoidal Salmonella isolates recovered from bovines and swine between 2000 and 2018, whereas it increased in poultry. These trends are consistent with those detected by national surveillance systems that monitor resistance using phenotypic testing. However, using genomes, we identified that genes conferring resistance to critically important antimicrobials were associated with specific MDR serovars that could be the focus for future interventions. Our analysis illustrates the growing potential of public repositories to monitor AMR trends and shows that similar efforts could soon be carried out in other regions where genomic surveillance is increasing.

Percentage Destabilization Effect of Some West African Medicinal Plants on the Outer Membrane of Various Bacteria Involved in Infectious Diarrhea.

Previous work stated that Khaya senegalensis, Anacardium ouest L., Pterocarpus erinaceus, Diospyros mespiliformis, Ocimum gratissimum, Manihot esculenta, Vernonia amygdalina Delile, and Daniellia oliveri have a great potential for the fight against infectious diarrhea. However, data on their antibacterial activity on strains of bacteria responsible for infectious diarrhea are not available. This study is aimed at elucidating the mechanism of action of the antibacterial effect of these plants on some bacterial strains responsible for diarrheal infections. The design of the study included first evaluating the degree of sensitivity of Salmonella typhimurium 14028, Escherichia coli ATCC 25922, Shigella spp., and Salmonella spp. strains to aqueous and hydroethanolic extracts of each plant, followed by the determination of minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and antibiotic power (Pa). This screening was completed with the evaluation of the possible mode of action of the extracts by testing the membrane permeability of these bacterial strains. The data collected indicate that the bacterial strains tested were sensitive to the extracts to varying degrees, except Cassia sieberiana DC and Pseudocedrela kotschyi extracts. For the active extracts, inhibition diameters ranged from 18.33 mm to 7 mm. With the exception of Escherichia coli, all strains were sensitive to the aqueous and hydroethanolic extracts of Anacardium occidentale. MICs vary between 3.37 and 25 mg/ml. Membrane permeability test data show that all active extracts affect the bacterial strains tested by attacking the stability of their outer membrane. For all active extracts, the high percentage of membrane destabilization of the bacteria is significantly (p < 0.05) better than that of cefixime used as a reference. Thus, it appears that these extracts can destroy Gram-negative bacteria and increase the fluidity and permeability of their cytoplasmic membrane. The knowledge of the mechanism of action of these extracts is an interesting contribution to the fundamental knowledge on the alternative that medicinal plants represent to antibiotics. These extracts can be used in the management of infectious diarrhea.

Bovine NK-lysin peptides exert potent antimicrobial activity against multidrug-resistant Salmonella outbreak isolates.

Multidrug-resistant (MDR) Salmonella is a threat to public health. Non-antibiotic therapies could serve as important countermeasures to control MDR Salmonella outbreaks. In this study, antimicrobial activity of cationic α-helical bovine NK-lysin-derived antimicrobial peptides was evaluated against MDR Salmonella outbreak isolates. NK2A and NK2B strongly inhibited MDR Salmonella growth while NK1 and NK2C showed minimum-to-no growth inhibition. Scrambled-NK2A, which is devoid of α-helicity but has the same net positive charge as NK2A, also failed to inhibit bacterial growth. Incubation of negatively charged MDR Salmonella with NK2A showed increased Zeta potential, indicating bacterial-peptide electrostatic attraction. Confocal and transmission electron microscopy studies revealed NK2A-mediated damage to MDR Salmonella membranes. LPS inhibited NK2A-mediated growth suppression in a dose-dependent response, suggesting irreversible NK2A-LPS binding. LPS-NK2A binding and bacterial membrane disruption was also confirmed via electron microscopy using gold nanoparticle-NK2A conjugates. Finally, NK2A-loaded polyanhydride nanoparticles showed sustained peptide delivery and anti-bacterial activity. Together, these findings indicate that NK2A α-helicity and positive charge are prerequisites for antimicrobial activity and that MDR Salmonella killing is mediated by direct interaction of NK2A with LPS and the inner membrane, leading to bacterial membrane permeabilization. With further optimization using nano-carriers, NK2A has the potential to become a potent anti-MDR Salmonella agent.