Staphylococcus aureus in Animals and Food: Methicillin Resistance, Prevalence and Population Structure. A Review in the African Continent

Epidemiology of Staphylococcus aureus food isolates: Comparison of conventional methods with whole genome sequencing typing methods

A variety of methods exists for typing bacteria. However, guidelines for the application and interpretation of typing tools in epidemiologic investigations of Staphylococcus aureus are lacking. This study aimed to identify appropriate typing methods for S. aureus population studies and outbreak investigation. We compared pulsed-field gel electrophoresis (PFGE), seven loci multi-locus sequence typing (MLST), core genome MLST (cgMLST), core single nucleotide polymorphism (cSNP), and enterotoxin (se/SE) profiles on 351 S. aureus isolates. The discriminatory power, concordance, and congruence of typing results were assessed. cgMLST, cSNP, and PFGE yielded the highest discrimination value, followed by se/SE typing and MLST. The best concordance of results was found between cgMLST and cSNP, while the best congruence was observed for cgMLST and cSNP with all methods, followed by PFGE with MLST. The strengths and weaknesses of each method are highlighted. For population structure, cgMLST and cSNP performed better than PFGE and MLST in terms of resolution of clusters and in phylogenetic inference. Enterotoxin profiles matched with MLST groups, suggesting the use of se/SE typing to predict MLST results. For the retrospective analysis of 31 outbreaks, all methods performed almost equally to discriminate epidemiologically related strains and can be used to unambiguously distinguish outbreak strains.

"One Health" Perspective on Prevalence of ESKAPE Pathogens in Africa: A Systematic Review and Meta-Analysis

The leading cause of hospital-acquired infections worldwide includes Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp. (ESKAPE) infections. These bacteria are commonly isolated from clinical settings and linked to a number of potentially fatal diseases associated with hospitals. The objective of this study was to review the prevalence of ESKAPE pathogens in Africa. We gathered and systematically reviewed the literature concerning the prevalence of ESKAPE pathogens, published in the English language from January 2014 to February 2024, from three databases (PubMed, Web of Science and ScienceDirect). Our overall results revealed that S. aureus was the most prevalent species (79.5%), followed by A. baumannii (27.6%), K. pneumoniae (24.2%), Enterobacter spp. (20%), P. aeruginosa (9.0%), and E. faecium (5.1%). Moreover, stool samples had the highest Pooled Prevalence Estimates (PPEs) of 44.0%, followed by urine, nasal, and blood samples with 37.3%, 26.9%, and 22.9%, respectively. For the diagnostic method used to identify these ESKAPE pathogens, VITEK-MS had the highest PPE of 55.2%, followed by whole genome sequencing and PCR with 37.1% and 33.2%, respectively. The highest PPE of ESKAPE pathogens was recorded in West Africa with 77.3%, followed by Central/Middle Africa and East Africa with 43.5% and 25.1%, respectively. The overall PPE of ESKAPE pathogens from humans, animals, the environment (water, soil, and surfaces) and food sources was 35.8%, 37.3%, 47.7%, and 34.2%, respectively. Despite their prevalence in nosocomial settings, studies have shown that the ESKAPE pathogens may be isolated from a range of environmental reservoirs, including soil, dumping sites, beach sand, wastewater, food, and fish farms, among others. This wide source of ESKAPE pathogens substrates indicates the need for a multidisciplinary collaborative partnership for epidemiological studies and intervention efforts by the human, veterinary, and environmental health sectors in Africa.

Epidemiology and antibiotic resistance of staphylococci on commercial pig farms in Cape Town, South Africa

Staphylococci are responsible for a wide range of infections in animals. The most common species infecting animals include Staphylococcus aureus, Staphylococcus epidermidis and Staphylococcus intermedius. Recent increases in antibiotic use and antibiotic resistance in animals highlight the need to understand the potential role of commercial livestock as a reservoir of staphylococci and antibiotic resistance genes. Nasal swabs were collected from 143 apparently healthy pigs and 21 pig farm workers, and 45 environmental swabs of feed and water troughs, from two commercial pig farms in the Western Cape, South Africa. Staphylococci were isolated, identified using mass-spectrometry, and antimicrobial susceptibility testing and Illumina whole genome sequencing were performed. One hundred and eighty-five (185) Staphylococcus spp. isolates were obtained, with Mammalicoccus sciuri (n = 57; 31%) being the most common, followed by S. hyicus (n = 40; 22%) and S. aureus (n = 29; 16%). S. epidermidis was predominantly identified in the farm workers (n = 18; 86%). Tetracycline resistance was observed across all species, with rates ranging from 67 to 100%. Majority of M. sciuri isolates (n = 40; 70%) were methicillin resistant, with 78% (n = 31) harbouring mecA. M. sciuri isolates had genes/elements which were associated with SCCmec_type_III (3A) and SCCmec_type_VIII(4A) and were mostly observed in ST61 strains. ST239 strains were associated with SCCmec_type_III(3A). High rates of tetracycline resistance were identified among staphylococci in the pig farms in Western Cape, South Africa. This highlights the need for policy makers to regulate the use of this antibiotic in pig farming.

Susceptibility to postbiotics - enterocins of methicillin-resistant Staphylococcus aureus strains isolated from rabbits

There is a major problem with the rising occurrence of highly virulent and multiply-resistant strains, including methicillin-resistant Staphylococcus aureus (MRSA), because of their difficult treatment. This study aimed to evaluate the antibacterial and antibiofilm effect of new enterocins (Ent) against potential pathogenic MRSA strains isolated from rabbits. Staphylococci were identified with PCR and screened for methicillin/oxacillin/cefoxitin resistance (MR) using the disk diffusion method and the PBP2' Latex Agglutination Test Kit. Enzyme production, hemolysis, DNase activity, slime production, and biofilm formation were tested in MRSA strains. The susceptibility of MRSA to eight partially-purified enterocins (Ent) produced by E. faecium and E. durans strains was checked using agar spot tests. The antibiofilm activity of Ents was tested using a quantitative plate assay. Out of 14 MRSA, PBP testing confirmed MR in 8 strains. The majority of MRSA showed DNase activity and β-hemolysis. Slime production and moderate biofilm formation were observed in all strains. MRSA were susceptible to tested Ents (100-12,800 AU/mL; except Ent4231). The antibiofilm effect of Ents (except Ent4231) was noted in the high range (64.9-97.0%). These results indicate that enterocins offer a promising option for the prevention and treatment of bacterial infections caused by biofilm-forming MRSA.

Effectiveness of cephalosporins in hydrolysis and inhibition of Staphylococcus aureus and Escherichia coli biofilms

IMPORTANCE

Staphylococcus aureus and Escherichia coli contribute to global health challenges by forming biofilms, a key virulence element implicated in the pathogenesis of several infections.

OBJECTIVE

The study examined the efficacy of various generations of cephalosporins against biofilms developed by pathogenic S. aureus and E. coli.

METHODS

The development of biofilms by both bacteria was assessed using petri-plate and microplate methods. Biofilm hydrolysis and inhibition were tested using first to fourth generations of cephalosporins, and the effects were analyzed by crystal violet staining and phase contrast microscopy.

RESULTS

Both bacterial strains exhibited well-developed biofilms in petri-plate and microplate assays. Cefradine (first generation) showed 76.78% hydrolysis of S. aureus biofilm, while significant hydrolysis (59.86%) of E. coli biofilm was observed by cefipime (fourth generation). Similarly, cefuroxime, cefadroxil, cefepime, and cefradine caused 78.8%, 71.63%, 70.63%, and 70.51% inhibition of the S. aureus biofilms, respectively. In the case of E. coli, maximum biofilm inhibition (66.47%) was again shown by cefepime. All generations of cephalosporins were more effective against S. aureus than E. coli, which was confirmed by phase contrast microscopy.

CONCLUSIONS AND RELEVANCE

Cephalosporins exhibit dual capabilities of hydrolyzing and inhibiting S. aureus and E. coli biofilms. First-generation cephalosporins exhibited the highest inhibitory activity against S. aureus, while the third and fourth generations significantly inhibited E. coli biofilms. This study highlights the importance of tailored antibiotic strategies based on the biofilm characteristics of specific bacterial strains.

Staphylococcus aureus Carriage in the Nasotracheal Cavities of White Stork Nestlings (Ciconia ciconia) in Spain: Genetic Diversity, Resistomes and Virulence Factors

The molecular ecology of Staphylococcus aureus in migratory birds (such as white storks) is necessary to understand their relevance in the "One Health" ecosystems. This study determined the nasotracheal carriage rates of S. aureus from white storks in Southern Spain and genetically characterized the within-host diversity. A collection of 67 S. aureus strains, previously obtained from 87 white stork nestlings (52 nasal and 85 tracheal samples) fed by their parents with food foraged in natural and landfill habitats, were tested for their antimicrobial resistance (AMR) phenotypes. Moreover, the AMR genotypes, immune evasion cluster (IEC), virulence genes and the detection of CC398 lineage were studied by PCR. The spa types and multilocus-sequencing-typing (MLST) were also determined by PCR and sequencing. Staphylococcus aureus carriage was found in 31% of storks (36.5%/11.9% in nasal/tracheal samples). All isolates were methicillin-susceptible (MSSA) and 8.8% of them were also susceptible to all tested antibiotics. The AMR phenotype/percentage/genes detected were as follows: penicillin/79.1%/blaZ; erythromycin-clindamycin-inducible/19.1%/ermA, ermT; tetracycline/11.9%/tetK; clindamycin/4.5%/lnuA and ciprofloxacin/4.5%. Twenty-one different spa types, including 2 new ones (t7778-ST15-CC15 and t18009-ST26-CC25), were detected and ascribed to 11 clonal complexes (CCs). MSSA-CC398 (8.2%), MSSA-CC15 (7.1%) and MSSA-ST291 (5.9%) were the most prevalent lineages in storks. Moreover, tst-positive (MSSA-CC22-t223 and MSSA-CC30-t1654), eta-positive (MSSA-CC9-t209) and etb-positive strains (MSSA-CC45-t015) were detected in four storks. The 18.5% of storks harboured distinct MSSA strains (with different lineages and/or AMR genes). Nestlings of storks foraging in landfills (10 CCs) had more diverse S. aureus strains than those of parents foraging in natural habitats (3 CCs). Low level of AMR was demonstrated among S. aureus strains. The predominance of MSSA-CC398 (an emergent clade) and toxigenic MSSA strains in stork nestlings highlight the need for continuous surveillance of S. aureus in wild birds.

spa Types and Staphylococcal Enterotoxin Production of Staphylococcus aureus Isolated from Wild Boar

Little is known about the structure of S. aureus population and the enterotoxin gene content in wild boar. In 1025 nasal swabs from wild boars, 121 S. aureus isolates were identified. Staphylococcal enterotoxin (SE) genes were identified in 18 isolates (14.9%). The seb gene was found in 2 S. aureus isolates, sec in 2 isolates, the see and seh genes were found in 4 and 11 isolates, respectively. The production of SEs was evaluated in bacteria grown in microbial broth. Concentration of SEB reached 2.70 µg/ml after 24 h and 4.46 µg/ml at 48 h. SEC was produced at 952.6 ng/ml after 24 h and 7.2 µg/ml at 48 h. SEE reached 124.1 ng/ml after 24 h and 191.6 ng/ml at 48 h of culture. SEH production reached 4.36 µg/ml at 24 h and 5.42 µg/ml at 48 h of culture. Thirty-nine spa types were identified among S. aureus isolates. The most prevalent spa types were t091 and t1181, followed by t4735 and t742, t3380 and t127. Twelve new spa types, i.e., t20572‒t20583 were identified. The wild boar S. aureus population was shown to contain previously identified animal/human-associated spa types and spa types not identified in humans or animals. We also indicate that wildlife animals can be a significant reservoir of see-positive S. aureus.

Zoonotic sources and the spread of antimicrobial resistance from the perspective of low and middle-income countries

BACKGROUND

Antimicrobial resistance is an increasing challenge in low and middle-income countries as it is widespread in these countries and is linked to an increased mortality. Apart from human and environmental factors, animal-related drivers of antimicrobial resistance in low- and middle-income countries have special features that differ from high-income countries. The aim of this narrative review is to address the zoonotic sources and the spread of antimicrobial resistance from the perspective of low- and middle-income countries.

MAIN BODY

Contamination with extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli is highest in poultry (Africa: 8.9-60%, Asia: 53-93%) and there is a risk to import ESBL-producing E. coli through poultry meat in Africa. In aquacultures, the proportion of ESBL-producers among E. coli can be high (27%) but the overall low quality of published studies limit the general conclusion on the impact of aquacultures on human health. ESBL-producing E. coli colonization of wildlife is 1-9% in bats or 2.5-63% birds. Since most of them are migratory animals, they can disperse antimicrobial resistant bacteria over large distances. So-called 'filth flies' are a relevant vector not only of enteric pathogens but also of antimicrobial resistant bacteria in settings where sanitary systems are poor. In Africa, up to 72.5% of 'filth flies' are colonized with ESBL-producing E. coli, mostly conferred by CTX-M (24.4-100%). While methicillin-resistant Staphylococcus aureus plays a minor role in livestock in Africa, it is frequently found in South America in poultry (27%) or pork (37.5-56.5%) but less common in Asia (poultry: 3%, pork: 1-16%).

CONCLUSIONS

Interventions to contain the spread of AMR should be tailored to the needs of low- and middle-income countries. These comprise capacity building of diagnostic facilities, surveillance, infection prevention and control in small-scale farming.

Comparative review of the nasal carriage and genetic characteristics of Staphylococcus aureus in healthy livestock: Insight into zoonotic and anthroponotic clones

Given the central role of livestock in understanding the genomic epidemiology of S. aureus, the present study systematically reviewed and synthesized data on the nasal S. aureus carriage, resistance patterns to critical antimicrobial agents, virulence factors and genetic lineages among healthy livestock. Bibliographical databases were searched for published studies from May 2003 to May 2022 on nasal S. aureus carriage, their phenotypic and genetic characteristics among healthy pigs (A), sheep and goats (B), cattle (C), poultry (D), camels (E) and buffaloes (F). Special focus was given to the prevalence of nasal MRSA, MRSA-CC398, MRSA-CC9, mecC-MRSA, MSSA-CC398, and resistance to linezolid (LZD^R), chloramphenicol (CLO^R) and tetracycline (TET^R) in S. aureus isolates. Of the 5492 studies identified, 146 comprised groups A(83)/B(18)/C(33)/D(4)/E(5)/F(3), and were found eligible. The overall pooled nasal prevalence of MRSA in healthy livestock was 13.8% (95% CI: 13.5-14.1) among a pooled 48,154 livestock population. Specifically, the pooled prevalence in groups A to F were: 16.0% (95% CI: 15.6-16.4), 3.7% (95% CI: 2.9-4.6), 13.6% (95% CI: 12.8-14.4), 5.8% (95% CI: 5.1-6.5), 7.1% (95% CI: 6.1-10.7), and 2.8% (95% CI: 1.5-4.8), respectively. These values varied considerably by continent. Varied pooled prevalences of CC398 lineage with respect to MRSA isolates were obtained, with the highest from pigs and cattle (>70%). Moreover, other classical animal-adapted MRSA as well as MSSA-CC398-t1928 were reported. TET^R-MSSA was lowest in cattle (18.9%) and highest in pigs (80.7%). LZD^R-S. aureus was reported in 8 studies (mediated by optrA and cfr), mainly in pigs (n = 4), while CLO^R-S. aureus was reported in 32 studies. The virulence genes luk-S/F-PV, tst, etd, sea, see were sparsely reported, and only in non-CC398-MRSA lineages. Certain S. aureus clones and critical AMR appeared to have predominance in some livestock, as in the case of pigs that are high nasal carriers of MRSA-CC398 and -CC9, and MSSA-CC398. These findings highlight the need for adequate prevention against the transmission of zoonotic S. aureus lineages to humans.

The European Union Summary Report on Antimicrobial Resistance in zoonotic and indicator bacteria from humans, animals and food in 2020/2021

Antimicrobial resistance (AMR) data on zoonotic and indicator bacteria from humans, animals and food are collected annually by the EU Member States (MSs) and reporting countries, jointly analysed by EFSA and ECDC and presented in a yearly EU Summary Report. This report provides an overview of the main findings of the 2020-2021 harmonised AMR monitoring in Salmonella spp., Campylobacter jejuni and C. coli in humans and food-producing animals (broilers, laying hens and turkeys, fattening pigs and bovines under 1 year of age) and relevant meat thereof. For animals and meat thereof, indicator E. coli data on the occurrence of AMR and presumptive Extended spectrum β-lactamases (ESBL)-/AmpC β-lactamases (AmpC)-/carbapenemases (CP)-producers, as well as the occurrence of methicillin-resistant Staphylococcus aureus are also analysed. In 2021, MSs submitted for the first time AMR data on E. coli isolates from meat sampled at border control posts. Where available, monitoring data from humans, food-producing animals and meat thereof were combined and compared at the EU level, with emphasis on multidrug resistance, complete susceptibility and combined resistance patterns to selected and critically important antimicrobials, as well as Salmonella and E. coli isolates exhibiting ESBL-/AmpC-/carbapenemase phenotypes. Resistance was frequently found to commonly used antimicrobials in Salmonella spp. and Campylobacter isolates from humans and animals. Combined resistance to critically important antimicrobials was mainly observed at low levels except in some Salmonella serotypes and in C. coli in some countries. The reporting of a number of CP-producing E. coli isolates (harbouring bla OXA-48, bla OXA-181, and bla NDM-5 genes) in pigs, bovines and meat thereof by a limited number of MSs (4) in 2021, requests a thorough follow-up. The temporal trend analyses in both key outcome indicators (rate of complete susceptibility and prevalence of ESBL-/AmpC- producers) showed that encouraging progress have been registered in reducing AMR in food-producing animals in several EU MSs over the last years.

Nasotracheal Microbiota of Nestlings of Parent White storks with Different Foraging Habits in Spain

Migratory storks could be vectors of transmission of bacteria of public health concern mediated by the colonization, persistence and excretion of such bacteria. This study aims to determine genera/species diversity, prevalence, and co-colonization indices of bacteria obtained from tracheal (T) and nasal (N) samples from storks in relation to exposure to point sources through foraging. One-hundred and thirty-six samples from 87 nestlings of colonies of parent white storks with different foraging habits (natural habitat and landfills) were obtained (84 T-samples and 52 N-samples) and processed. Morphologically distinct colonies (up to 12/sample) were randomly selected and identified by MALDI-TOF-MS. About 87.2% of the total 806 isolates recovered were identified: 398 from T-samples (56.6%) and 305 from N-samples (43.4%). Among identified isolates, 17 genera and 46 species of Gram-positive and Gram-negative bacteria were detected, Staphylococcus (58.0%) and Enterococcus (20.5%) being the most prevalent genera. S. sciuri was the most prevalent species from T (36.7%) and N (34.4%) cavities of total isolates, followed by E. faecalis (11.1% each from T and N), and S. aureus [T (6.5%), N (13.4%)]. Of N-samples, E. faecium was significantly associated with nestlings of parent storks foraging in landfills (p = 0.018). S. sciuri (p = 0.0034) and M. caseolyticus (p = 0.032) from T-samples were significantly higher among nestlings of parent storks foraging in natural habitats. More than 80% of bacterial species in the T and N cavities showed 1-10% co-colonization indices with one another, but few had ≥ 40% indices. S. sciuri and E. faecalis were the most frequent species identified in the stork nestlings. Moreover, they were highly colonized by other diverse and potentially pathogenic bacteria. Thus, storks could be sentinels of point sources and vehicles of bacterial transmission across the "One Health" ecosystems.

Pet animals as reservoirs for spreading methicillin-resistant Staphylococcus aureus to human health

Methicillin-resistant Staphylococcus aureus (MRSA) is a strain of pathogenic bacteria that is a major problem in the world's health. Due to their frequent interaction with humans, pets are one of the main risk factors for the spread of MRSA. The possibility for zoonotic transmission exists since frequently kept dogs and cats are prone to contract MRSA and act as reservoirs for spreading MRSA. The mouth, nose, and perineum are the primary locations of MRSA colonization, according to the findings of MRSA identification tests conducted on pets. The types of MRSA clones identified in cats and dogs correlated with MRSA clones infecting humans living in the same geographic area. A significant risk factor for the colonization or transmission of MRSA is human-pet contact. An essential step in preventing the spread of MRSA from humans to animals and from animals to humans is to keep hands, clothing, and floor surfaces clean.

Molecular Basis of Methicillin and Vancomycin Resistance in Staphylococcus aureus from Cattle, Sheep Carcasses and Slaughterhouse Workers

Staphylococcus aureus (S. aureus) is a serious infection-causing pathogen in humans and animal. In particular, methicillin-resistant S. aureus (MRSA) is considered one of the major life-threatening pathogens due to its rapid resistance to several antibiotics in clinical practice. MRSA strains have recently been isolated in a number of animals utilized in food production processes, and these species are thought to be the important sources of the spread of infection and disease in both humans and animals. The main objective of the current study was to assess the prevalence of drug-resistant S. aureus, particularly vancomycin-resistant S. aureus (VRSA) and MRSA, by molecular methods. To address this issue, a total of three hundred samples (200 meat samples from cattle and sheep carcasses (100 of each), 50 hand swabs, and 50 stool samples from abattoir workers) were obtained from slaughterhouses in Egypt provinces. In total, 19% S. aureus was isolated by standard culture techniques, and the antibiotic resistance was confirmed genotypically by amplification nucA gen. Characteristic resistance genes were identified by PCR with incidence of 31.5%, 19.3%, 8.7%, and 7% for the mecA, VanA, ermA, and tet L genes, respectively, while the aac6-aph gene was not found in any of the isolates. In this study, the virulence genes responsible for S. aureus' resistance to antibiotics had the highest potential for infection or disease transmission to animal carcasses, slaughterhouse workers, and meat products.

Genetic characterization of Staphylococcus aureus isolated from Norway rats in Boston, Massachusetts

BACKGROUND

Despite the importance of domesticated animals in the generation and transmission of antibiotic-resistant Staphylococcus aureus, the role of wild animals, specifically rodents, in the ecology of S. aureus remains unclear. We recovered and genotyped S. aureus isolates from wild Norway rats (Rattus norvegicus) in Boston, Massachusetts to examine genetic relationships between common human and animal S. aureus isolates in a large US metropolitan area.

METHODS

We collected and necropsied 63 rats from June 2016 to June 2017. Nasal, foot pad, fur, and fecal swabs were collected. Staphylococcus aureus was isolated using culture-based methods and polymerase chain reaction confirmation. S. aureus isolates were spa typed, tested for antibiotic susceptibility, and whole genome sequenced. Assembled sequences were uploaded to the Comprehensive Antibiotic Resistance Database to identify antibiotic resistance elements. A phylogenetic tree was constructed using the neighbor-joining method with the maximum composite likelihood distance in MEGA7.

RESULTS

We recovered 164 Gram-positive bacterial isolates from Norway rats. Nineteen isolates from eight individual rats were confirmed as S. aureus (prevalence: 12.9% (8/63)). All S. aureus isolates were methicillin-susceptible S. aureus (MSSA), pvl-negative, and resistant to penicillin. Two isolates displayed resistance to erythromycin. Four different S. aureus spa types were detected (t933, t10751, t18202, and t189). Thirteen unique antibiotic resistance elements were identified, and all isolates shared genes mepR, mgrA, arlR, and S. aureus norA. Phylogenetic analysis if the 19 S. aureus isolates revealed they were genetically similar to four clades of S. aureus with similar resistance gene profiles isolated from both human- and animal-derived S. aureus, as well as formed a distinct phylogenetic cluster composed only of rat isolates.

CONCLUSIONS

Wild rodents may serve as a reservoir or vector of antibiotic resistance genes in the urban environment with relevance for human and animal health.

Epidemiology and antimicrobial resistance of staphylococci other than Staphylococcus aureus from domestic animals and livestock in Africa: a systematic review

Introduction

Staphylococci other than Staphylococcus aureus (SOSA) in animals are becoming more pathogenic and antibiotic resistant and can potentially disseminate to humans. However, there is little synthesized information regarding SOSA from animals in Africa. This systematic review provides a comprehensive overview of the epidemiology and antimicrobial resistance of SOSA in companion animals (pets) and livestock in Africa.

Method

This systematic review (PROSPERO-CRD42021252303) was conducted according to the PRISMA guidelines, and 75 eligible studies from 13 countries were identified until August 2022. Three electronic databases (Pubmed, Scopus and Web of Science) were employed.

Results

The frequently isolated SOSA were S. epidermidis, S. intermedius, S. pseudintermedius, S. xylosus, S. chromogenes, S. hyicus, M. sciuri, S. hominis, and S. haemolyticus. Thirty (40%) studies performed antibiotic susceptibility testing (AST). Penicillin (58%) and tetracycline (28%) resistance were most common across all SOSA with high rates of resistance to aminoglycosides, fluoroquinolones, and macrolides in some species. Resistance to last-resort antibiotics such as linezolid and fusidic acid were also reported. Limited data on strain typing and molecular resistance mechanisms precluded analysis of the clonal diversity of SOSA on the continent.

Conclusion

The findings of this review indicate that research on livestock-associated SOSA in Africa is lacking in some regions such as Central and Western Africa, furthermore, research on companion animals and more advanced methods for identification and strain typing of SOSA need to be encouraged.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier: CRD42021252303.

Review of pork and pork products as a source for transmission of methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is an opportunistic bacterium that can cause infection in animals and humans. Recently, MRSA from food-producing or farm animals has been identified as livestock-associated MRSA (LA-MRSA). The spread of LA-MRSA is particularly found in pork and pork products because LA-MRSA has been widely known to infect pigs. The most common type of LA-MRSA identified in pork and pork products is the clonal complex LA-MRSA 398 (LA-MRSA CC398). The MRSA strains on the surface of pork carcasses can be spread during the handling and processing of pork and pork products through human hands, cutting tools, and any surface that comes into direct contact with pork. Food infection is the main risk of MRSA in pork and pork products consumed by humans. Antibiotics to treat food infection cases due to MRSA infection include vancomycin and tigecycline. The spread of MRSA in pork and pork products is preventable by appropriately cooking and cooling the pork and pork products at temperatures above 60°C and below 5°C, respectively. It is also necessary to take other preventive measures, such as having a clean meat processing area and disinfecting the equipment used for processing pork and pork products. This review aimed to explain epidemiology, transmission, risk factors, diagnosis, public health consequences, treatment of food poisoning, and preventing the spread of MRSA in pork and pork products.

Antimicrobial Resistance Profile of Common Foodborne Pathogens Recovered from Livestock and Poultry in Bangladesh

Multidrug-resistant (MDR) foodborne pathogens have created a great challenge to the supply and consumption of safe & healthy animal-source foods. The study was conducted to identify the common foodborne pathogens from animal-source foods & by-products with their antimicrobial drug susceptibility and resistance gene profile. The common foodborne pathogens Escherichia coli (E. coli), Salmonella, Streptococcus, Staphylococcus, and Campylobacter species were identified in livestock and poultry food products. The prevalence of foodborne pathogens was found higher in poultry food & by-product compared with livestock (p < 0.05). The antimicrobial drug susceptibility results revealed decreased susceptibility to penicillin, ampicillin, amoxicillin, levofloxacin, ciprofloxacin, tetracycline, neomycin, streptomycin, and sulfamethoxazole-trimethoprim whilst gentamicin was found comparatively more sensitive. Regardless of sources, the overall MDR pattern of E. coli, Salmonella, Staphylococcus, and Streptococcus were found to be 88.33%, 75%, 95%, and 100%, respectively. The genotypic resistance showed a prevalence of blaTEM, blaSHV, blaCMY, tetA, tetB, sul1, aadA1, aac(3)-IV, and ereA resistance genes. The phenotype and genotype resistance patterns of isolated pathogens from livestock and poultry had harmony and good concordance, and sul1 & tetA resistance genes had a higher prevalence. Good agricultural practices along with proper biosecurity may reduce the rampant use of antimicrobial drugs. In addition, proper handling, processing, storage, and transportation of foods may decline the spread of MDR foodborne pathogens in the food chain.

First Genome-Based Characterisation and Staphylococcal Enterotoxin Production Ability of Methicillin-Susceptible and Methicillin-Resistant Staphylococcus aureus Strains Isolated from Ready-to-Eat Foods in Algiers (Algeria)

Staphylococcus aureus is a pathogenic microorganism of humans and animals, able to cause foodborne intoxication due to the production of staphylococcal enterotoxins (SEs) and to resist antibiotic treatment as in the case of methicillin-resistant S. aureus (MRSA). In this study, we performed a genomic characterisation of 12 genetically diverse S. aureus strains isolated from ready-to-eat foods in Algiers (Algeria). Moreover, their ability to produce some classical and new staphylococcal enterotoxins (SEs) was investigated. The 12 S. aureus strains resulted to belong to nine known sequence types (STs) and to the novel ST7199 and ST7200. Furthermore, S. aureus SA46 was assigned to the European clone MRSA-ST80-SCCmec-IV. The 12 strains showed a wide endowment of se and sel (staphylococcal enterotoxin-like toxin) genes (sea, seb, sed, seg, seh, sei, selj, sek, sem, sen, seo, seq, ser, selu2, selw, selx, sey, sel30; ψent1-ψent2), including variants and pseudogenes, and harboured the enterotoxin gene cluster (egc) types 1 and 5. Additionally, they produced various amounts of SEA (64.54-345.02 ng/mL), SEB (2871.28-14739.17 ng/mL), SED (322.70-398.94 ng/mL), SEH (not detectable-239.48 ng/mL), and SER (36,720.10-63,176.06 ng/mL) depending on their genotypes. The genetic determinants related to their phenotypic resistance to β-lactams (blaZ, mecA), ofloxacin (gyrA-S84L), erythromycin (ermB), lincomycin (lmrS), kanamycin (aph(3')-III, ant(6)-I), and tetracyclin (tet(L), tet(38)) were also detected. A plethora of virulence-related genes, including major virulence genes such as the tst gene, determinant for the toxic shock syndrome toxin-1, and the lukF-PV and lukS-PV genes, encoding the panton-valentine leukocidin (PVL), were present in the S. aureus strains, highlighting their pathogenic potential. Furthermore, a phylogenomic reconstruction including worldwide foodborne S. aureus showed a clear clustering based on ST and geographical origin rather than the source of isolation.

Rapid and visual detection of Staphylococcus aureus in milk using a recombinase polymerase amplification-lateral flow assay combined with immunomagnetic separation

AIMS

The aim of this study was to develop a novel approach using lateral flow recombinase polymerase amplification (RPA-LF) combined with immunomagnetic separation (IMS) for the rapid detection of Staphylococcus aureus in milk.

METHODS AND RESULTS

Under optimum conditions, the average capture efficiency values (CEs) for S. aureus strains (10⁴ CFU ml^-1 ) was above 95.0% in PBST and ~80% in milk within 45 min with 0.7 mg immunomagnetic beads. The RPA-LF assay, which comprised DNA amplification via RPA at 39°C for 10 min and visualization of the amplicons through LF strips for 5 min, detected S. aureus within 15 min. The method only detected S. aureus and did not show cross-reaction with other bacteria, exhibiting a high level of specificity. Sensitivity experiments confirmed a detection limit of RPA-LF assay as low as 600 fg reaction^-1 for the S. aureus genome (corresponding to approximately 36 CFU of S. aureus), which was about 16.7-fold more sensitive than that of the conventional PCR method. When RPA-LF was used in combination with IMS to detect S. aureus inoculated into artificially contaminated milk, it exhibited a detection limit of approximately 40 CFU reaction^-1 .

CONCLUSIONS

The newly developed IMS-RPA-LF method enabled detection of S. aureus at levels as low as 40 CFU reaction^-1 in milk samples without culture enrichment for an overall testing time of only 70 min.

SIGNIFICANCE AND IMPACT OF THE STUDY

The newly developed IMS-RPA-LF assay effectively combines sample preparation, amplification, and detection into a single platform. Because of its high sensitivity, specificity, and speed, the IMS-RPA-LF assay will have important implications for the rapid detection of S. aureus in contaminated food.

Comparative genomics of dairy-associated Staphylococcus aureus from selected sub-Saharan African regions reveals milk as reservoir for human-and animal-derived strains and identifies a putative animal-related clade with presumptive novel siderophore

Staphylococcus aureus infection is considered to be a neglected tropical disease with huge impact on human and animal health alike. Dairy production in sub-Saharan Africa (SSA) relies heavily on various animals such as cows, goats, and camels, depending on the region. S. aureus causes mastitis and exhibits high prevalence in raw milk. The population structure including genotypic and phenotypic traits of dairy S. aureus in relation to animal and human isolates is, however, unknown for SSA. In this work, 20 S. aureus dairy isolates from East and West Africa were selected for comparative genomics and phenotypic analysis. Comparing their population structure revealed a large diversity of different origins suggesting milk to be a reservoir for human and animal strains alike. Furthermore, a novel putative siderophore was detected in multiple strains in a distinct animal-clade with strains of global origin. This putative siderophore shares a high genetic identity with that from Streptococcus equi suggesting possible horizontal gene transfer. These findings combined with the virulence genes harbored by these dairy-derived strains such as pvl, human evasion factor scn, various enterotoxin, leucocidin and antibiotic resistance genes, stresses the need for an integrative One Health approach to tackle the problem of S. aureus infections in animals and humans in sub-Saharan Africa.

The Spread of Antibiotic Resistance Genes In Vivo Model

Infections caused by antibiotic-resistant bacteria are a major public health threat. The emergence and spread of antibiotic resistance genes (ARGs) in the environment or clinical setting pose a serious threat to human and animal health worldwide. Horizontal gene transfer (HGT) of ARGs is one of the main reasons for the dissemination of antibiotic resistance in vitro and in vivo environments. There is a consensus on the role of mobile genetic elements (MGEs) in the spread of bacterial resistance. Most drug resistance genes are located on plasmids, and the spread of drug resistance genes among microorganisms through plasmid-mediated conjugation transfer is the most common and effective way for the spread of multidrug resistance. Experimental studies of the processes driving the spread of antibiotic resistance have focused on simple in vitro model systems, but the current in vitro protocols might not correctly reflect the HGT of antibiotic resistance genes in realistic conditions. This calls for better models of how resistance genes transfer and disseminate in vivo. The in vivo model can better mimic the situation that occurs in patients, helping study the situation in more detail. This is crucial to develop innovative strategies to curtail the spread of antibiotic resistance genes in the future. This review aims to give an overview of the mechanisms of the spread of antibiotic resistance genes and then demonstrate the spread of antibiotic resistance genes in the in vivo model. Finally, we discuss the challenges in controlling the spread of antibiotic resistance genes and their potential solutions.

In Vitro Growth-Inhibitory Synergistic Effect of Zinc Pyrithione in Combination with Gentamicin against Bacterial Skin Pathogens of Livestock

Bacterial skin diseases of livestock could be a serious global threat, especially in association with overcoming bacterial resistance. Combinatory action of antimicrobial agents proves to be an effective strategy to overcome the problem of increasing antibiotic resistance of microorganisms. In this study, the in vitro combined effect of zinc pyrithione with gentamicin against bacterial skin pathogens of livestock (Staphylococcus aureus, Streptococcus agalactiae, and Streptococcus dysgalactiae) was evaluated according to the sum of fractional inhibitory concentration indices (FICI) obtained by checkerboard method. The results showed that a combination of zinc pyrithione with gentamicin produced a strong synergistic effect (p < 0.001) against all tested streptococcal strains (with FICI values ranging from 0.20 to 0.42). Compared to that, only three out of eight S. aureus strains were highly susceptible to the combination of antimicrobial agents at single concentration (0.25 µg/mL) of zinc pyrithione with range of FICI 0.35−0.43. These findings suggest that interference between agents tested in this study can be used for the development of future veterinary pharmaceutical preparations for the treatment of bacterial skin infections of livestock.

Antimicrobial Susceptibility Profiles and Molecular Characterisation of Staphylococcus aureus from Pigs and Workers at Farms and Abattoirs in Zambia

Pigs have been shown to be a reservoir for recently emerging livestock-associated Staphylococcus aureus (LA-SA), including methicillin resistant strains in many countries worldwide. However, there is sparse information about LA-SA strains circulating in Zambia. This study investigated the prevalence, phenotypic and genotypic characteristics of S. aureus from pigs and workers at farms and abattoirs handling pigs in Lusaka Province of Zambia. A total of 492 nasal pig swabs, 53 hand and 53 nasal human swabs were collected from farms and abattoirs in selected districts. Standard microbiological methods were used to isolate and determine antimicrobial susceptibility patterns of S. aureus. Polymerase Chain Reaction was used to confirm the species identity and detect antimicrobial resistance and virulence genes of isolates, whereas genetic diversity was evaluated using spa typing. Overall prevalence of S. aureus was 33.1%, 37.8% for pigs and 11.8% for humans. The isolates were resistant to several antibiotics with resistance ranging from 18% to 98% but were all susceptible to vancomycin. Typical LA-SA spa types were detected. The presence of plasmid mediated resistance genes such as tetM (12.8%), other resistance determinants and immune evasion cluster genes among the isolates is of great public health concern. Thus, continuous surveillance of S. aureus using a “One health” approach is warranted to monitor S.aureus infections and spread of antimicrobial resistance.

A 6-Year Update on the Diversity of Methicillin-Resistant Staphylococcus aureus Clones in Africa: A Systematic Review

Background

Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of hospital-associated (HA) and community-associated (CA) infections globally. The multi-drug resistant nature of this pathogen and its capacity to cause outbreaks in hospital and community settings highlight the need for effective interventions, including its surveillance for prevention and control. This study provides an update on the clonal distribution of MRSA in Africa.

Methods

A systematic review was conducted by screening for eligible English, French, and Arabic articles from November 2014 to December 2020, using six electronic databases (PubMed, EBSCOhost, Web of Science, Scopus, African Journals Online, and Google Scholar). Data were retrieved and analyzed according to the Preferred Reporting Items for Systematic Review and Meta-Analysis guidelines (registered at PROSPERO: CRD42021277238). Genotyping data was based primarily on multilocus sequence types (STs) and Staphylococcal Cassette Chromosome mec (SCCmec) types. We utilized the Phyloviz algorithm in the cluster analysis and categorization of the MRSA STs into various clonal complexes (CCs).

Results

We identified 65 studies and 26 publications from 16 of 54 (30%) African countries that provided sufficient genotyping data. MRSA with diverse staphylococcal protein A (spa) and SCCmec types in CC5 and CC8 were reported across the continent. The ST5-IV [2B] and ST8-IV [2B] were dominant clones in Angola and the Democratic Republic of Congo (DRC), respectively. Also, ST88-IV [2B] was widely distributed across the continent, particularly in three Portuguese-speaking countries (Angola, Cape Verde, and São Tomé and Príncipe). The ST80-IV [2B] was described in Algeria and Egypt, while the HA-ST239/ST241-III [3A] was only identified in Egypt, Ghana, Kenya, and South Africa. ST152-MRSA was documented in the DRC, Kenya, Nigeria, and South Africa. Panton-Valentine leukocidin (PVL)-positive MRSA was observed in several CCs across the continent. The median prevalence of PVL-positive MRSA was 33% (ranged from 0 to 77%; n = 15).

Conclusion

We observed an increase in the distribution of ST1, ST22, and ST152, but a decline of ST239/241 in Africa. Data on MRSA clones in Africa is still limited. There is a need to strengthen genomic surveillance capacity based on a "One-Health" strategy to prevent and control MRSA in Africa.

Prevalence, Enterotoxigenic Potential and Antimicrobial Resistance of Staphylococcus aureus and Methicillin-Resistant Staphylococcus aureus (MRSA) Isolated from Algerian Ready to Eat Foods

Staphylococcus aureus causes a foodborne intoxication due to the production of enterotoxins and shows antimicrobial resistance, as in the case of methicillin-resistant strains (MRSA). Herein, we analyzed 207 ready-to-eat foods collected in Algeria, reporting a S. aureus prevalence of 23.2% (48/207) and respective loads of coagulase positive staphylococci (CPS) ranging from 1.00 ± 0.5 to 5.11 ± 0.24 Log CFU/g. The 48 S. aureus isolates were widely characterized by staphylococcal enterotoxin gene (SEg)-typing and 16S-23S rDNA intergenic spacer region (ISR)-PCR, as well as by detecting tst and mecA genes, genetic determinants of toxic shock syndrome toxin-1 and methicillin resistance, respectively. We found that the S. aureus isolates belonged to seven different SEg-types harboring the following combinations of genes: (1) selW, selX; (2) egc (seG, seI, seM, seN, seO), selW, selX; (3) seA, seH, seK, seQ, selW, selX; (4) seB, selW, selX; (5) seD, selJ, seR, selW, selX; (6) seH, selW, selX, selY; and (7) seA, egc, selW, selX, while among these, 2.1% and 4.2% were tst- and mecA- (staphylococcal chromosomal cassette mec-type IV) positive, respectively. Selected strains belonging to the 12 detected ISR-types were resistant towards antimicrobials including benzylpenicillin, ofloxacin, erythromycin, lincomycin, tetracyclin, kanamycin, oxacillin, and cefoxitin; 8.3% (1/12) were confirmed as MRSA and 16.7% (2/12) were multidrug resistant. The present study shows the heterogeneity of the S. aureus population in Algerian ready-to-eat foods as for their toxigenic potential and antimicrobial resistance, shedding the light on the quality and safety related to the consume of ready-to-eat foods in Algeria.

Methicillin-Resistant Staphylococcus aureus from Municipal Abattoirs in Nigeria: Showing Highly Similar Clones and Possible Transmission from Slaughter Animals to Humans

In recent years, methicillin-resistant Staphylococcus aureus (MRSA) has gained interest in veterinary medicine due to its zoonotic potential. Currently, little information is available on the genotypic and virulence characteristics of MRSA isolates detected in Nigerian abattoirs. To better understand the epidemiology of MRSA associated with the abattoir food chain environment in Nigeria, a total of 18 isolates (humans: n = 5, slaughter animals: n = 5, and environment: n = 8), previously spa typed, were recovered and characterized by Staphylococcus cassette chromosome mec (SCCmec) typing, and phenotypic and genotypic antimicrobial susceptibility testing. In addition, 10 of the 18 MRSA strains with a new spa type (t16571) were subjected to multilocus sequence typing. The similarity of strains was analyzed based on the results of the DNA microarray analysis. The 18 MRSA strains harbored two distinct SCCmec types (IVa and V) and belonged to four clonal clusters (CC1, CC7, CC88, and CC152). All MRSA of the new spa type t16571 (n = 10) harbored the SCCmec type IVa. Seven of the MRSA t16571 strains belonged to ST88, while three other strains were assigned to ST3614. The 18 MRSA isolates were categorized into six virulence profiles, and the detection rate for the Panton-Valentine Leukocidin gene was high (33.3%). The antimicrobial susceptibility profiles of the 18 MRSA varied widely between strains, but phenotypic resistance corresponded to relevant resistance genes harbored. The detection of highly similar MRSA strains in slaughter animals, abattoir workers, and the environment underlines the need to use adequate measures at Nigerian abattoirs to prevent further spread and transmission of MRSA to humans or food.

Molecular characteristics and risk factor analysis of Staphylococcus aureus colonization put insight into CC1 colonization in three nursing homes in Shanghai

Research indicates that Staphylococcus aureus colonization in the elderly with predisposing risks is associated with subsequent infection. However, the molecular epidemiology and risk factors for S. aureus colonization among residents and staff in nursing homes (NHs) in China remain unclear. A multicenter study was conducted in three NHs in Shanghai between September 2019 and October 2019. We explored the prevalence, molecular epidemiology, and risk factors for S. aureus colonization. All S. aureus isolates were characterized based on antimicrobial resistance, virulence genes, multilocus sequence typing (MLST), staphylococcus protein A (spa) typing, and staphylococcal cassette chromosome mec (SCCmec) typing. NH records were examined for potential risk factors for S. aureus colonization. S. aureus and methicillin-resistant S. aureus (MRSA) isolates were detected in 109 (100 residents and 9 staff, 19.8%, 109/551) and 28 (24 residents and 4 staff, 5.1%, 28/551) subjects among 496 residents and 55 staff screened, respectively. Compared to methicillin-susceptible S. aureus isolates, all 30 MRSA isolates had higher resistance rates to most antibiotics except minocycline, rifampicin, linezolid, vancomycin, and teicoplanin. Sequence type (ST) 1 (21.3%) was the most common sequence type, and t127 (20.5%) was the most common spa type among 122 S. aureus isolates. SCCmec type I (70%) was the dominant clone among all MRSA isolates. CC1 (26/122, 21.3%) was the predominant complex clone (CC), followed by CC398 (25/122, 20.5%), CC5 (20/122, 16.4%) and CC188 (18/122, 14.8%). Female sex (OR, 1.70; 95% CI, 1.04-2.79; P = 0.036) and invasive devices (OR, 2.19; 95% CI, 1.26-3.81; P = 0.006) were independently associated with S. aureus colonization.

Molecular Characterization of Staphylococcus aureus Isolated from Human and Food Samples in Northern Algeria

Staphylococcus aureus is a commensal resident of the skin and nasal cavities of humans and can cause various infections. Some toxigenic strains can contaminate food matrices and cause foodborne intoxications. The present study aimed to provide relevant information (clonal complex lineages, agr types, virulence and antimicrobial resistance-associated genes) based on DNA microarray analyses as well as the origins and dissemination of several circulating clones of 60 Staphylococcus aureus isolated from food matrices (n = 24), clinical samples (n = 20), and nasal carriers (n = 16) in northern Algeria. Staphylococcus aureus were genotyped into 14 different clonal complexes. Out of 60 S. aureus, 13 and 10 isolates belonged to CC1-MSSA and CC97-MSSA, respectively. The CC 80-MRSA-IV was the predominant S. aureus strain in clinical isolates. The accessory gene regulator allele agr group III was mainly found among clinical isolates (70.4%). Panton–Valentine leukocidin genes lukF/lukS-PV were detected in 13.3% of isolates that all belonged to CC80-MRSA. The lukF/S-hlg, hlgA, and hla genes encoding for hemolysins and leucocidin components were detected in all Staphylococcusaureus isolates. Clinical and food isolates harbored more often the antibiotic resistance genes markers. Seventeen (28.3%) methicillin-resistant Staphylococcus aureus carrying the mecA gene localized on a SCCmec type IV element were identified. The penicillinase operon (blaZ/I/R) was found in 71.7% (43/60) of isolates. Food isolates belonging to CC97-MSSA carried several antibiotic resistance genes (blaZ, ermB, aphA3, sat, tetM, and tetK). The results of this study showed that all clones were found in their typical host, but interestingly, some nasal carriers had isolates assigned to CC705 thought to be absent in humans. The detection of MRSA strains among food isolates should be considered as a potential public health risk. Therefore, controlling the antibiotics prescription for a rational use in human and animal infections is mandatory.

Prevalence of Staphylococcus aureus, Methicillin-Resistant Staphylococcus aureus and Potential Risk Factors in Selected Dairy Farms at the Interface of Animal and Human in Bishoftu, Ethiopia

Background

Staphylococcus aureus (S. aureus) has been reported as the most commonly isolated highly contagious pathogen from human, animals and animal products. Methicillin-resistant Staphylococcus aureus (MRSA) has emerged as a significant pathogen with zoonotic potential that could have devastating consequence for the health and well-being of animals and human.

Methods

A cross-sectional study was conducted from July 2020 to January 2021. A total of 233 samples from cow milk, udder swabs and milkers' hand swabs were collected for culture and identification based on the standard protocol. Antimicrobial susceptibility tests were performed for all isolates by using Kirby Bauer's disk diffusion test. MRSA was detected by cefoxitin disk diffusion test.

Results

S. aureus was isolated from 50 (21.46%) of 233 samples and the prevalence of MRSA was 4%. The highest prevalence was found in cow milk 36 (25.53%) followed by hand swabs 10 (19.23%) and udder swabs 4 (10%). S. aureus prevalence was 58.33%, 30.0%, 21.43%, 17.92%, 15.79% in farm D, C, E, A, B respectively. A large percentage (58.33% and 30%) were from farm D and C. S. aureus isolation rate showed statistically significant association with farm types (p = 0.011) and with previous mastitis exposure (p = 0.001). High level of resistance was observed to penicillin (94%) and ampicillin (92%), but low level resistance to gentamicin (0%), amikacin (0%), ceftriaxone (0%), chloramphenicol (4%), ciprofloxacin and cefoxitin (4%). The overall prevalence of multidrug resistance (MDR) was 10.42%.

Conclusion

Prevalence of S. aureus in milk showed statistically significant association with respect to previous mastitis exposure and farm types (p = 0.011). High level of resistant to penicillin and ampicillin was observed. Therefore, effective mastitis control programs, best veterinary practice among all farms and use of antibiotics in the farm should be strictly controlled.

First Report of Antimicrobial Susceptibility and Virulence Gene Characterization Associated with Staphylococcus aureus Carriage in Healthy Camels from Tunisia

Simple Summary

The one-humped camel (Camelus dromedarius) is an important livestock species and is present in more than 46 national entities, with 80% of the camel population inhabiting Africa. In these regions, the role of camels in the livestock economy is highly valuable and a part of this camel herd is valorized on national or international markets for meat production, live animal export or milk production. Even if camels are the species that is most adapted to the harsh conditions of arid/semi-arid rangelands, they can be susceptible to a high number of pathogens, including S. aureus. This latter is often associated with asymptomatic carriage but can also be responsible for several diseases, therefore causing considerable economical losses. Continued monitoring and control assume particular importance in containing the spread of the bacterium since it constitutes an important zoonotic disease.

Abstract

A total of 318 nasal and rectal swabs were collected from 159 apparently healthy camels (Camelus dromedarius) randomly selected from five regions in southern and central Tunisia and screened for Staphylococcus aureus carriage. Staphylococcus spp. were recovered from 152 of 159 camels studied (95.6%) and in total 258 swabs (81%) were positive. Among these isolates, 16 were coagulase positive Staphylococcus (CoPS) (6.2%) and were characterized by biochemical and molecular tests as S. aureus. These were isolated from 14 camels (8.8%) with co-carriage in nasal and rectal mucosa by two camels. All S. aureus isolates recovered were methicillin-susceptible Staphylococcus aureus (MSSA) and were characterized by spa typing and PFGE. Three different spa types were recovered: t729, t4013 and a spa type newly registered as t19687, which was the most common. PFGE analysis revealed seven different patterns and these were characterized by MLST, which revealed five different sequence types (ST6, ST88, ST3583 and two new sequences, ST6504 and ST6506). All isolates harbored different virulence genes, including hld, encoding delta hemolysin; lukE–lukD, encoding bicomponent leukotoxin LukE–LukD; the clfB gene, encoding clumping factor B; the laminin gene, encoding laminin-binding protein; and cap8, encoding capsule type 8. Fifteen isolates harbored hemolysin beta (hlb) and fourteen encoded hemolysin alpha (hla) and hemolysin G2 (hlg_v). Adhesin factors, including clfA and fnbB, were detected in five and four isolates respectively. Binding proteins, including collagen (cbp) and elastin-binding protein (ebp), were detected in two S. aureus isolates while fibrinogen-binding protein (fib) was identified in four isolates. This study provides the first set of genotyping data on the population structure and presence of toxin genes of S. aureus strains in Tunisian camels.

Prevalence and Characteristics of Staphylococcus aureus Associated with Meat and Meat Products in African Countries: A Review

Antimicrobial resistance has been increasing globally, which negatively affects food safety, veterinary, and human medicine. Ineffective antibiotics may cause treatment failure, which results in prolonged hospitalisation, increased mortality, and consequently, increased health care costs. Staphylococcus aureus causes a diverse range of infections including septicaemia and endocarditis. However, in food, it mainly causes food poisoning by the production of enterotoxins. With the discovery of methicillin-resistant S. aureus strains that have a separate reservoir in livestock animals, which were termed as livestock-associated methicillin-resistant S. aureus (LA-MRSA) in 2005, it became clear that animals may pose another health risk. Though LA-MRSA is mainly transferred by direct contact, food transmission cannot be excluded. While the current strains are not very pathogenic, mitigation is advisable, as they may acquire new virulence genes, becoming more pathogenic, and may transfer their resistance genes. Control of LA-MRSA poses significant problems, and only Norway has an active mitigation strategy. There is limited information about LA-MRSA, MRSA in general, and other S. aureus infections from African countries. In this review, we discuss the prevalence and characteristics of antimicrobial susceptible and resistant S. aureus (with a focus on MRSA) from meat and meat products in African countries and compare it to the situation in the rest of the world.

Genomic analysis of Staphylococcus aureus from the West African Dwarf (WAD) goat in Nigeria

Background

Staphylococcus aureus can colonize various host species, and human-animal interaction is a significant factor for cross-species transmission. However, data on S. aureus colonization in animals, particularly on ruminants in close contact with humans, is limited. The West African Dwarf (WAD) goat is among the earliest domesticated ruminant associated with rural dwellers and small-holder farmers in sub-Saharan Africa. This study aimed to investigate the population structure, antibiotic resistance, and virulence gene determinants of S. aureus from the WAD goat in Nigeria.

Methods

Nasal samples were obtained from the WAD goat in five markets in Osun State, South-West Nigeria. S. aureus was characterized by antibiotic susceptibility testing, detection of virulence determinants, spa typing, and multilocus sequence typing (MLST). Representative isolates were selected for whole-genome sequencing, biofilm, and cytotoxicity assay.

Results

Of the 726 nasal samples obtained from the WAD goat, 90 S. aureus (12.4%) were recovered. Overall, 86 isolates were methicillin-susceptible, and four were mecA-positive (i.e., methicillin-resistant S. aureus [MRSA]). A diverse S. aureus clonal population was observed (20 sequence types [STs] and 37 spa types), while 35% (13/37) and 40% (8/20) were new spa types and STs, respectively. Eleven MLST clonal complexes (CC) were identified (CC1, CC5, CC8, CC15, CC30, CC45, CC97, CC121, CC133, CC152, CC522). The MRSA isolates were designated as t127-ST852-CC1-SCCmec type VII, t4690-ST152-CC152-SCCmec type Vc, and t8821-ST152-CC152-SCCmec type Vc. Phylogenetic analysis revealed that 60% (54/90) of all isolates were associated with ruminant lineages (i.e., CC133, CC522). Panton-Valentine Leukocidin (PVL)-positive S. aureus was identified in CC1, CC30, CC121, and CC152. For the CC522 isolates, we illustrate their pathogenic potential by the detection of the toxic shock syndrome gene and hemolysins, as well as their strong cytotoxicity and ability to form biofilms.

Conclusions

This is the first detailed investigation on the genomic content of S. aureus from the WAD goat in Nigeria. The S. aureus population of the WAD goat consists mainly of ruminant-associated lineages (e.g., CC133, CC522), interspersed with human-associated clones, including PVL-positive MRSA CC1 and CC152.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13756-021-00987-8.

Biofilm formation and antibiotic resistance in staphylococcus isolated from different objects

Staphylococci have a wide range of pathogenic properties, among which stands increased resistance to antibiotics and the ability to form a biofilm. Being divided into coagulase-positive and coagulase-negative, they have different and, at the same time, common biological properties and may be a source of genetic material for each other. The aim of the study was to examine the properties of staphylococci, isolated from various objects (milk, pigs, companion animals, humans), their resistance to antibiotics, the ability to form a biofilm and the presence of genes, responsible for resistance to methicillin and biofilm formation. In this study we used 89 Staphylococci strains. 18 (20.2 %) strains were coagulase-positive, where 2 (2.2 %) strains, isolated from different animals and humans, had a complete set of phenotypic (plasma coagulation, biofilm formation, resistance to oxacillin and benzylpenicillin) and genotypic (mec A, fem B, ica A, ica D) signs of pathogenicity. Coagulase-negative staphylococci, isolated from various animals and humans, had resistance to oxacillin, benzylpenicillin and the ability to form biofilms, and also had the corresponding genes in their structure (mec A, ica AB, ica D) in 3.3 % of cases. Staphylococci, isolated from different animals and humans, were able to form a biofilm and had the appropriate set of genes (ica D, ica AB) in 5.6 % of cases.

Characterization of Staphylococcus aureus ST3320 clone causing fatal respiratory infection in rabbits

<em>Staphylococcus aureus</em> is a well-known pathogen that infects humans and animals. However, information on the fatal respiratory infection in rabbits caused by<em> S. aureus</em> is still limited. In the present study, a <em>S. aureus</em> isolate designated ND01 was recovered from lung samples of rabbits that died of fatal respiratory infection, and the ND01 was characterised by intranasal infection of rabbits, multi-locus sequencing typing, screening virulence genes and testing antimicrobial susceptibility. Clinical signs of matted forepaws and pathological lesions of haemorrhagic tracheitis and necrotising haemorrhagic pneumonia were observed in the ND01 infected rabbits, which were identical to those of naturally infected ones. The sequence type of the ND01 was defined as ST3320 and the ND01 was further grouped into the clonal complex 398. Notably, the ND01 was <em>pvl-positive</em> <em>S. aureus</em> and carried the human-associated scn gene. Moreover, the ND01 was methicillin-susceptible <em>S. aureus</em> and was susceptible to 6 of 10 tested antibiotics. This study described the characteristics of the ND01 causing fatal respiratory infection in rabbits. The results are helpful to further the understanding of the pathogenicity of S. aureus ST3320 clone in rabbits. The results also highlighted that operators must be on the alert for the colonisation of <em>pvl-positive</em> <em>S. aureus</em> in rabbits and potential transmission events between rabbits and humans.

Pigs as a potential source of emerging livestock-associated Staphylococcus aureus in Africa: a systematic review

OBJECTIVE

To assess the emergence of livestock-associated Staphylococcus aureus including methicillin-resistant S. aureus (MRSA) in the pig and pork production systems in Africa for the past two decades.

METHODS

PubMed and African Journals OnLine were searched for relevant primary studies from 2000 to 2019 using standardized key words. In total, 19 eligible articles were included in this review.

RESULTS

The prevalence of S. aureus including MRSA ranged from 0% to 55% among live pigs and raw pork, and from 9.4% to 30.8% among pig farm and abattoir workers. Risk factors associated with S. aureus carriage among workers were: male gender, working in an abattoir, and medical-related occupation of a household member. S. aureus and MRSA from pigs and pork production systems in Africa are potentially pathogenic with diverse spa types and clonal complexes, with genes encoding antimicrobial resistance, heavy metal resistance, and virulence factors including secreted and enterotoxins, proteases and immune evasion cluster. The typical livestock-associated S. aureus CC398 and mecC genes were reported in two studies.

CONCLUSION

Pigs are a potential source of the emerging livestock-associated S. aureus in Africa. Continued monitoring using a 'One Health' approach is recommended for effective infection prevention and control of these infections in Africa.

Detection of multi-drug resistance and methicillin-resistant Staphylococcus aureus (MRSA) isolates from retail meat in Tamaulipas, Mexico

Purpose

Among the principal microorganisms transmitted to humans by foods of animal origin, Staphylococcus aureus stands out, causing a variety of diseases and with a wide potential for acquiring antimicrobial resistance. This work aimed to determine the prevalence of S. aureus, its multi-drug resistance (MDRSA), and the identification of methicillin-resistant Staphylococcus aureus (MRSA) in retail beef and pork in the state of Tamaulipas, Mexico.

Methods

S. aureus strains isolated from retail meat were characterized by microbiological and molecular methods to determine phenotypic drug-resistance and detect MRSA strains.

Results

Of the 106 samples (54 from beef and 52 from pork) from 11 different cities, we detected a prevalence of S. aureus of 44.3% (47/106). A total of 87 S. aureus strains were identified; these presented 54 resistance patterns to different antimicrobials with a high prevalence of MDRSA (85%) and a low prevalence of MRSA strains (3%).

Conclusion

These results indicate the presence of MDRSA and MRSA in retail beef and pork in Tamaulipas, representing a high risk for consumer health.

Staphylococcus aureus in Intensive Pig Production in South Africa: Antibiotic Resistance, Virulence Determinants, and Clonality

Although Staphylococcus aureus is a major threat to the veterinary, agricultural, and public health sectors because of its zoonotic potential, studies on its molecular characterisation in intensive animal production are rare. We phenotypically and genotypically characterised antibiotic-resistant S. aureus in intensive pig production in South Africa, using the farm-to-fork approach. Samples (n = 461) were collected from the farm, transport vehicles, and the abattoir using the World Health Organisation on Integrated Surveillance of Antimicrobial Resistance (WHO-AGISAR) sampling protocol. Bacteria were isolated using selective media and identified using biochemical tests and polymerase chain reaction (PCR). Phenotypic resistance was determined using the disk diffusion method. Selected resistance and virulence genes were investigated using PCR. Clonality among the isolates was determined using the repetitive element sequence-PCR. In all, 333 presumptive staphylococcal isolates were obtained, with 141/333 (42.3%) identified as staphylococci biochemically. Ninety-seven (97; 68.8%) were confirmed as S. aureus using PCR, 52.6% of which were identified as methicillin-resistant S. aureus (MRSA) through the mecA gene. All the 97 S. aureus isolates (100%) were resistant to at least one of the antibiotics tested, with the highest resistance observed against erythromycin and clindamycin (84.50% each), and the lowest observed against amikacin (2.10%); 82.47% (80/97) were multidrug-resistant with an average multiple antibiotic resistance index of 0.50. Most of the phenotypically resistant isolates carried at least one of the corresponding resistance genes tested, ermC being the most detected. hla was the most detected virulence gene (38.14%) and etb was the least (1.03%). Genetic fingerprinting revealed diverse MRSA isolates along the farm-to-fork continuum, the major REP types consisting of isolates from different sources suggesting a potential transmission along the continuum. Resistance to antibiotics used as growth promoters was evidenced by the high prevalence of MDR isolates with elevated multiple antibiotic resistance indices >0.2, specifically at the farm, indicating exposure to high antibiotic use environments, necessitating antibiotic stewardship and proper infection control measures in pig husbandry and intensive pig production.

The presence of antibiotic-resistant Staphylococcus spp. and Escherichia coli in smallholder pig farms in Uganda

BACKGROUND

The development of antimicrobial resistance is of global concern, and is commonly monitored by the analysis of certain bacteria. The aim of the present study was to study the antibiotic susceptibility in isolates of Staphylococcus spp. and Escherichia (E.) coli obtained from healthy pigs originating from nineteen herds enrolled in a study on herd health management in Lira district, northern Uganda. Skin and nasal swabs were analyzed for the presence of Staphylococcus spp., and selectively cultivated to investigate the presence of methicillin-resistant Staphylococcus (S.) aureus (MRSA), and rectal swabs were analyzed for the presence of E. coli. Antibiotic susceptibility was tested by broth micro-dilution. Information on the antibiotic usage and treatment regimens during the previous year was gathered using structured interviews and longitudinal data.

RESULTS

In Staphylococcus spp., resistance to penicillin (10/19 isolates; 53%), fusidic acid (42%) and tetracycline (37%) were most commonly found. In E. coli, resistance to sulfamethoxazole (46/52 isolates; 88%), tetracycline (54%) and trimethoprim (17%) was most frequent. Methicillin-resistant S. aureus was found in one sample (1/50; 2%). Multi-drug resistant isolates of Staphylococcus spp. and E. coli were found in 54 and 47% of the herds, respectively. At the herd level, no associations could be made between antibiotic resistance and herd size or treatment regimens for either of the bacteria.

CONCLUSION

In conclusion, resistance to important antibiotics frequently used in animals in Uganda was common, and the presence of MRSA was demonstrated, in Ugandan pig herds.

Comparative Genomics of Plasmid-Bearing Staphylococcus aureus Strains Isolated From Various Retail Meats

Food poisoning due to the consumption of Staphylococcus aureus contaminated food is a major health problem worldwide. In this study, we sequenced the genomes of ten plasmid-bearing S. aureus strains isolated from retail beef, chicken, turkey, and pork. The chromosomes of the strains varied in size from 2,654,842 to 2,807,514 bp, and a total of 25 plasmids were identified ranging from 1.4 to 118 kb. Comparative genomic analysis revealed similarities between strains isolated from the same retail meat source, indicating an origin-specific genomic composition. Genes known to modulate attachment, invasion, and toxin production were identified in the 10 genomes. Strains from retail chicken resembled human clinical isolates with respect to virulence factors and genomic islands, and retail turkey and pork isolates shared similarity with S. aureus from livestock. Most chromosomes contained antimicrobial resistance, heavy metal resistance, and stress response genes, and several plasmids contained genes involved in antimicrobial resistance and virulence. In conclusion, the genomes of S. aureus strains isolated from retail meats showed an origin-specific composition and contained virulence and antimicrobial resistance genes similar to those present in human clinical isolates.

Review on Major Food-Borne Zoonotic Bacterial Pathogens

Food-borne microorganisms are major pathogens affecting food safety and cause human illness worldwide as a result of consumption of foodstuff, mainly animal products contaminated with vegetative pathogens or their toxins. Most of these microbes have zoonotic importance resulting in significant impact on both public health and economic sectors. Bacteria are the causative agents of two-thirds of human food-borne diseases worldwide with high burden in developing countries. Hence, the objectives of this review paper are to highlight the background of food-borne bacterial pathogens and to review common major food-borne zoonotic bacterial pathogens. Food animals are the major reservoirs of many food-borne zoonotic bacterial pathogens, and food products of animal origin are the main vehicles of transmission. Meat, dairy products, and eggs are the main ways by which people are exposed to zoonotic bacteria. S. aureus, Salmonella species, Campylobacter species, L. monocytogenes, and E. coli are the major zoonotic bacterial pathogens which are the causative agents of food-borne illness and death in the world associated with consumption of contaminated animal products. Production of toxins and structural virulent factors are responsible for the pathogenesis of these bacteria. These major zoonotic bacteria cause human infections which are characterized mainly by gastrointestinal symptoms including nausea, vomiting, diarrhea, abdominal cramps, and other agent-specific symptoms. Some bacteria may cause severe complications. Conventional (culturing), serological, and molecular techniques are important for detection of these common zoonotic bacteria and their toxins in food. Good hygiene, GMP, sanitation in operating procedures, and implementation of standardized HACCP and pasteurization procedures are effective methods for the control and prevention. Currently, the emergence of multidrug-resistant zoonotic bacteria associated with consumption of contaminated animal products is a great concern for the public health, and there should be coordinated surveillance and monitoring system for food-borne zoonotic bacterial pathogens particularly in developing countries including Ethiopia.

Whole-genome sequence profiling of antibiotic-resistant Staphylococcus aureus isolates from livestock and farm attendants in Ghana

OBJECTIVE

Epidemic methicillin-resistant Staphylococcus aureus (MRSA) clones have been described in Ghana, but so far, no typical livestock-associated MRSA isolates (CC398) have been found. In this study we provide baseline information on antimicrobial resistance, population structure, and virulence gene content of S. aureus isolates from livestock and farm attendants.

METHODS

Nasal samples were collected from cattle, pigs, goats, sheep, and farm attendants from three farms. Staphylococcus aureus was identified by matrix-assisted laser desorption/ionisation time-of-flight and antimicrobial susceptibility testing was performed using VITEK II (Biomerieux, Marcy l'Etoile, France) and interpreted according to EUCAST guidelines. Whole-genome sequencing was performed using the Illumina, San Diego, CA, USA MiSeq Platform.

RESULTS

In total, 401 nasal swab samples were obtained from 57 farm attendants, 208 pigs, 30 goats, 26 sheep, and 80 cattle. The S. aureus isolates (n = 25) recovered (farm attendants: n = 10; pigs: n = 8; and goats: n = 7) were frequently resistant to penicillin (68%), tetracycline (44%), and ciprofloxacin (32%); two human isolates were MRSA. Twelve isolates (48%) were multidrug resistant (MDR) (>3 classes). Genome sequencing of the isolates revealed ST152-t355, ST9-t1430, and ST133-t8662 as dominant clones among farm attendants, pigs, and goats, respectively. The two MRSA isolates detected belonged to ST8-t334 and ST152-t355. The scn and sak genes associated with human-adaption were detected in 10 isolates; 9 from humans and 1 from a goat. Typing results provided evidence of a single potential transmission event (t861, PVL-, scn+).

CONCLUSION

No MRSA was detected among livestock, perhaps because of low intensive farming; however, the relatively high prevalence of MDR isolates may be a result of inappropriate antibiotic usage in Ghanaian livestock production.

Molecular epidemiology, genetic diversity and antimicrobial resistance of Staphylococcus aureus isolated from chicken and pig carcasses, and carcass handlers

The epidemiology of Staphylococcus aureus in food animals, associated products, and their zoonotic potential in Nigeria are poorly understood. This study aimed to provide data on the prevalence, genetic characteristics and antimicrobial resistance of S. aureus isolated from chicken and pig carcasses, and persons in contact with the carcasses at slaughterhouses in Nigeria. Surface swabs were collected randomly from 600 chicken and 600 pig carcasses. Nasal swabs were collected from 45 workers in chicken slaughterhouses and 45 pig slaughterhouse workers. S. aureus isolates were analyzed by spa typing. They were also examined for presence of the Panton-Valentine Leucocidin (PVL) and mecA genes, as well as for antimicrobial resistance phenotype. Overall, 53 S. aureus isolates were recovered (28 from chicken carcasses, 17 from pig carcasses, 5 from chicken carcass handlers and 3 from pig carcass handlers). Among the isolates, 19 (35.8%) were PVL-positive and 12 (22.6%) carried the mecA gene. The 53 isolates belonged to 19 spa types. The Based Upon Repeat Pattern (BURP) algorithm separated the isolates into 2 spa-clonal complexes (spa-CC) and 9 singletons including 2 novel spa types (t18345 and t18346). The clonal complexes (CC) detected were CC1, CC5, CC8, CC15, CC88 and CC152. CC15-related isolates represented by spa type t084 (32.1%) and CC5 represented by spa type t311 (35.3%) predominated among isolates from chicken carcasses/ handlers, and pig carcasses/ handlers, respectively. Multidrug resistance exhibited by all the CC except CC8, was observed among isolates from chicken carcasses (64.3%), pig carcasses (41.2%), handlers of chicken meat (40.0%) and handlers of pork (33.3%). All the CC showed varying degrees of resistance to tetracycline while CC15 and CC5 exhibited the highest resistance to sulphamethoxazole/trimethoprim and erythromycin, respectively. The predominant antimicrobial resistance pattern observed was penicillin-tetracycline-sulphamethoxazole/trimethoprim (PEN-TET-SXT). In conclusion, food animals processed in Enugu State in Southeast Nigeria are potential vehicles for transmission of PVL-positive multiple-drug resistant S. aureus and methicillin-resistant S. aureus from farm to slaughterhouse and potentially to the human population. Public health intervention programs at pre- and post-slaughter stages should be considered in Nigerian slaughterhouses.

Global priority pathogens: virulence, antimicrobial resistance and prospective treatment options

Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp. and Salmonella spp. are part of a group of pathogens that pose a major threat to human health due to the emergence of multidrug-resistant strains. Moreover, these bacteria have several virulence factors that allow them to successfully colonize their hosts, such as toxins and the ability to produce biofilms, resulting in an urgent need to develop new strategies to fight these pathogens. In this review, we compile the most up-to-date information on the epidemiology, virulence and resistance of these clinically important microorganisms. Additionally, we address new therapeutic alternatives, with a focus on molecules with antivirulence activity, which are considered promising to combat multidrug-resistant bacteria.

The Evolutionary Genomics of Host Specificity in Staphylococcus aureus

Staphylococcus aureus is an important human bacterial pathogen that has a cosmopolitan host range, including livestock, companion and wild animal species. Genomic and epidemiological studies show that S. aureus has jumped between host species many times over its evolutionary history. These jumps have involved the dynamic gain and loss of host-specific adaptive genes, usually located on mobile genetic elements. The same functional elements are often consistently gained in jumps into a particular species. Further sampling of diverse animal species is likely to uncover an even broader host range and greater genetic diversity of S. aureus than is already known, and understanding S. aureus host specificity in these hosts will mitigate the risks of emergent human and livestock strains.

Antimicrobial resistance pattern and virulence profile of S. aureus isolated from household cattle and buffalo with mastitis in Egypt

Methicillin resistant S. aureus from cows with mastitis has received a growing interest worldwide. The present study aimed to provide a detailed description of the resistance and virulence traits of isolates from bovine mastitis samples. A total of 550 quarter milk samples were collected from 140 mastitic household dairy cows and buffalo from five herds at Dakahlia Governorate, Egypt, during 2017 and 2018. Staphylococcus spp. were isolated and differentiated using MALDI-TOF MS. A genotypic characterization was performed for S. aureus isolates using DNA-microarray and staphylococcal protein A (spa) typing. Furthermore, antibiotic resistances were phenotypically confirmed using broth microdilution. Six different clonal lineages (CC1-MRSA, CC5-MRSA, CC45-MRSA, CC97-MSSA, CC50-MSSA and CC1153-MSSA), including seven spa types (t127, t688, t132, t267, t521, t224 and t903) were identified. Spa type t267 was the most dominant among the investigated herds. This is the first report of the occurrence of clonal lineages CC97, CC1, CC45, CC50 and CC1153 from bovine mastitis in Egypt. All MRSA isolates and 33.3 % of MSSA were multi-resistant (i.e. resistant to more than three classes of compounds). Various virulence determinants were also observed including leukocidins, hemolysins, and enterotoxins. The study demonstrates a low diversity of S. aureus isolates recovered from several dairy herds. The findings of the observed virulotypes can be useful for future studies on anti-virulence therapies, immunogenicity and vaccine development.

Genetic characterisation of staphylococci of food-producing animals in Senegal. PVL detection among MSSA

Background

Food-producing animals can be a vehicle for staphylococcal species as well as their virulence and antimicrobial resistance genes. This work aimed to analyse the diversity of staphylococcal species in food-producing animals in Dakar/Senegal, and to determine the antimicrobial resistance phenotype/genotype and virulence factors of recovered isolates. Nasal samples of 149 cows and 199 chickens (348 animals) were collected from one slaughterhouse and a local market respectively, and were inoculated on selective media for staphylococci recovery. For S. aureus isolates, molecular typing (spa-type, MLST) was performed by PCR/sequencing, and the presence of 27 virulence genes (exfoliative and toxic shock toxins, PVL, haemolysins and enterotoxins) as well as the gene scn were analysed by PCR. Susceptibility to twelve antibiotics was studied by disc-diffusion method for all staphylococci; the resistance genes involved were screened by PCR.

Results

Staphylococcus spp. was present in 3 and 26.8% of chicken and cow nasal samples, respectively. Seven S. aureus isolates and forty isolates of other staphylococcal species were identified. S. aureus isolates were recovered from cow (n = 6) and chicken (n = 1) samples, belonging to four genetic lineages: t084/ST15 (n = 1); t10579/ST291 (n = 3); t355, t4690/ST152 (n = 2); and t6618/ST6 (n = 1). All S. aureus were methicillin-susceptible, penicillin-resistant (blaZ), and two of them were also tetracycline-resistant [tet(K)]. All the isolates carried at least one of the virulence genes tested. The PVL genes were detected in three ST15 and ST152 isolates. They all harboured haemolysins encoding genes and lacked the scn gene. The other staphylococci recovered were S. sciuri (n = 16), S. simulans (n = 11), S. hyicus (n = 5), S. haemolyticus (n = 4), S. chromogenes (n = 3), and S. hominis (n = 1); they were all methicillin-susceptible and 27.5% tetracycline-resistant [tet(K) and tet(L)].

Conclusions

A low prevalence of S. aureus was detected among food-producing animals, all susceptible to methicillin. However, the presence of virulence genes (lukF/lukS-PV, eta, tst, sea and see) is worrisome to the extent that they could be transferred to derived food and therefore, to humans.

Comparison of Staphylococcus aureus surface protein extraction methods and immunogenicity

Staphylococcus aureus is the major contagious bovine mastitis pathogen and has no effective vaccine. Strain variation and limited knowledge of common immunogenic antigen/s are among major constraints for developing effective vaccines. S. aureus cell surface proteins that are exposed to the host immune system constitute good vaccine candidates. The objective of this study was to compare two novel S. aureus surface protein extraction methods with biotinylation method and evaluate immune-reactivity of extracted proteins. Surface proteins were extracted from nine genetically distinct S. aureus strains from cases of bovine mastitis. After extraction, bacterial cell integrity was examined by Gram staining and electron microscopy to determine if extraction methods caused damage to cells that may release non-surface proteins. The extracted proteins were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and evaluated for immune-reactivity using western blot. Results showed that all three extraction methods provided multiple protein bands on SDS-PAGE. Western blot result showed several immunoreactive surface proteins, in which some proteins strongly (well-resolved, thick, dark, and intense band) reacted across the nine strains tested. The three methods are valid for the extraction of surface proteins and hexadecane, and cholic acid methods are more feasible than biotinylation since both are easier, cheaper, and have minor effects on the bacterial cell. Strongly immune-reactive surface proteins may serve as potential candidates for a vaccine to control S. aureus mastitis in dairy cows.