Genetic characterization and antimicrobial resistance of Staphylococcus aureus isolated from bovine milk in Tunisia

Genotypes and virulence factors in Staphylococcus aureus isolated from dairy cows with subclinical mastitis in Serbia

This study aimed to determine the prevalence of Staphylococcus aureus subclinical mastitis and to genotype the S. aureus isolates using the 16S-23S rRNA intergenic spacer (RS-PCR) method. In addition, the genes responsible for adherence, biofilm formation, host evasion, tissue necrosis, methicillin resistance, and enterotoxin production of S. aureus were investigated. The overall prevalence of S. aureus subclinical mastitis in lactating cows was 5.4% (95% confidence interval, CI=4.7-6.1%). An increased risk of S. aureus intramammary infection was observed on small family farms (odds ratio, OR=4.2, 95% CI=2.6-6.6, P < 0.001) and medium-sized farms (OR=3.5, 95% CI=2.2-5.7, P < 0.001). The RS-PCR analysis revealed 44 genotypes and genotype variants, of which 15 new genotypes and five new variants were detected within small and medium-sized farms. S. aureus isolates of new genotypes and genotype variants carried the clfA gene responsible for adherence at a lower frequency (64.8%) and enterotoxin-producing genes sea (20.4%), seb (14.8%) and sec (14.8%) at a higher frequency than the other known genotypes (P < 0.001), and were confirmed to carry the sej and sep genes. The spa gene was detected in all S. aureus isolates, whereas none harbored bap, ser, or tsst-1 genes. Methicillin-resistant strains of S. aureus (MRSA) were also detected, with a higher prevalence (19.2%) on large farms with more than 50 cows (P < 0.001). Using molecular techniques as diagnostic tools provides a better understanding of intramammary staphylococcal infections' occurrence, spread, and eradication.

Genetic and Phenotypic Characterization of Subclinical Mastitis-Causing Multidrug-Resistant Staphylococcus aureus

The core objective of this study was to genetically and phenotypically characterize subclinical mastitis-causing multidrug-resistant Staphylococcus aureus (MDRSA). In addition, risk factors associated with subclinical mastitis caused by MDRSA were investigated. Bacterial cultures were performed on 2120 mammary quarters, 40 swabs of milk utensils, 5 bulk tank milk samples, and 11 nostril and 11 hand swabs from milkers from five dairy farms. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was conducted for S. aureus identification. Antimicrobial resistance was screened phenotypically using the disk diffusion test in all S. aureus isolates. A biofilm formation assay; detection of genes associated with beta-lactam resistance, efflux pump, and biofilm formation; and pulsed-field gel electrophoresis (PFGE) were performed in all MDRSA isolates. Multi-locus sequence typing (MLST) was carried out in cefoxitin-resistant MDRSA isolates. A total of 188 S. aureus isolates from milk as well as two from milking utensils and one from bulk tank milk were identified. Most of the isolates (92.7%; 177 of 191) showed beta-lactam resistance, and 7% (14 of 191) were MDRSA. Interestingly, 36% (5 of 14) of MDRSA isolates were cefoxitin-resistant, but none carried mecA or mecC genes. Based on PFGE results, it was observed that S. aureus strains were more likely to be unique to a specific herd. Two clonal complexes were identified, CC97 (ST126; commonly livestock-associated) and CC1 (ST7440; usually community-associated). To the best of our knowledge, this is the first report of ST7440 isolated from bovine mastitis in Brazil. The risk factor results underscored the importance of considering parity, stage of lactation, SCC, milk production, and herd size when studying the risk of subclinical mastitis and antimicrobial resistance in S. aureus. Thus, to implement effective strategies to prevent subclinical mastitis in dairy herds and to minimize MDRSA spread, it is important to understand MDRSA strains' distribution and their antimicrobial resistance profile.

High genetic diversity and zoonotic potential of Staphylococcus aureus strains recovered from bovine intramammary infections in Colombians dairy herds

Genotyping of Staphylococcus aureus isolated from mastitis has become a fundamental tool to understand its complex epidemiology and to evaluate spillover events. The aim of this study was to describe the frequency of genotypes of the S. aureus strains isolated from intramammary infections by spa typing technique, and to evaluate the association between genotypes and the ability to form biofilm under in vitro conditions. Sixty-six strains of S. aureus recovered from bovines intramammary infections on 56 dairy herds located in 14 municipalities of the department of Antioquia were characterized. The majority of strains (65/66) were isolated from milk samples collected from dairy cows with subclinical intramammary infections. Nineteen different spa types were found in this study, t521 (19.70%), t267 (15.15%), and t605 (12.12%) being the most frequent. The strains from the t605 spa type showed the highest biofilm production. The high frequency of spa types with zoonotic potential found in this study, identified cattle as an important reservoir of theses clones for people in close proximity, such as milkers and consumers of unpasteurized dairy products.

Prevalence and molecular characteristics of Staphylococcus aureus in raw milk and milk products in Ethiopia: a systematic review and meta-analysis

Background

Staphylococcus aureus is an important opportunistic pathogen of raw milk and milk products, and the enterotoxins cause food poisoning. Milk and milk products are important reservoirs of enterotoxin-producing S. aureus. The aims of this systematic review were to estimate the pooled prevalence of S. aureus, including methicillin-resistant Staphylococcus aureus (MRSA), and to summarize their molecular characteristics, assess the potential sources of S. aureus contamination in bulk milk and analyse the antimicrobial resistance patterns of the isolates.

Methods

Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we searched publicly available scientific online databases and search engines: PubMed, Research for Life, African Journal Online (AJOL), and Google Scholar. In addition, the reference lists of the identified studies were manually checked for relevant literature. A random effects model using the DerSimonian method was used to compute pooled prevalence estimates, and the data were transformed using variance stabilizing Freeman-Tukey double arcsine transformation.

Results

A total of 38 studies were included in this systematic review. The pooled prevalence of S. aureus was highest in raw cow milk (30.7%), followed by camel milk (19.3%), goat milk (13.6%) and pasteurized milk (3.8%). The pooled prevalence of S. aureus in locally produced soft cheese (ayib) and traditional fermented milk (ergo) was 18.6% and 14.9%, respectively. The pooled prevalence of MRSA in milk and milk products was 0.73%. In this study, 58.9% of S. aureus isolates recovered from milk and milk products harbored at least one type of enterotoxin gene. Raw milk of the three species (cow, goat and camel) showed the highest S. aureus pooled prevalence rate at processing plants (50.3%), followed by milk collection centers (MCCs) (47.1%), selling points (34.5%), farm bulk milk (25.8%), milking buckets (24.8%) and udder milk (20.3%). Water for washing milking utensils (39.3%) was more contaminated than swab samples from farm workers’ nares (31.5%), milkers’ hands (25.9%), MCCs containers (23.8%), bulk tanks (20.4%), udders (15.6%), milking buckets (14.2%) and towels (10%). S. aureus isolates were highly resistant to penicillin G (92%), followed by ampicillin (82%) and amoxicillin (62.6%). The pooled multidrug resistance (MDR) was high (62.1%).

Conclusion

This systematic review revealed a high and increasing level of S. aureus contamination of raw milk from udder to MCCs or processing plants. Enterotoxin genes and MRSA were reported in milk, milk products and samples from farm workers. S. aureus showed resistance to different antimicrobial agents, with β-lactams showing the highest pooled antimicrobial resistance and the level of MDR was high. The results of this study indicated that the consumption of raw milk and milk products may predispose consumers to staphylococcal food poisoning. Application of good hygiene and handling practices across the dairy value chain starting from farm, udder health, milk cooling, heat treatment of milk before drinking and rational use of antibiotics in veterinary medicine can reduce the potential health risks from S. aureus and MRSA contamination of milk and milk products.

Usefulness of molecular typing methods for epidemiological and evolutionary studies of Staphylococcus aureus isolated from bovine intramammary infections

In cattle, Staphylococcus aureus is a major pathogen of increasing importance due to its association with intramammary infections (IMIs), which are a primary cause of antibiotic use on farms and thus of the rise in antibiotic resistance. Methicillin-resistant S. aureus (MRSA), which are frequently isolated from cases of bovine mastitis, represent a public health problem worldwide. Understanding the epidemiology and the evolution of these strains relies on typing methods. Such methods were phenotypic at first, but more recently, molecular methods have been increasingly utilized. Multiple-locus variable number tandem repeat analysis (MLVA), a high-throughput molecular method for determining genetic diversity and the emergence of host- or udder-adapted clones, appears to be the most useful PCR-based method. Despite the difficulties present in reproducibility, interlaboratory reliability, and hard work, it is agreed that pulsed-field gel electrophoresis (PFGE) remains the gold standard, particularly for short-term surveillance. Multilocus sequence typing (MLST) is a good typing method for long-term and global epidemiological investigations, but it is not suitable for outbreak investigations. Staphylococcal protein A (spa) typing is the most widely used method today for first-line typing in the study of molecular evolution, and outbreaks investigations. Staphylococcal cassette chromosome mec (SCCmec) typing has gained popularity for the evolutionary analysis of MRSA strains. Whole-genome sequencing (WGS) and DNA microarrays that represent relatively new DNA-based technologies, provide more information for tracking antibioresistant and virulent outbreak strains. They offer a higher discriminatory power, but are not suitable for routine use in clinical veterinary medicine at this time. Descriptions of the evolution of these methods, their advantages, and limitations are given in this review.

Diversity and pathogenesis of Staphylococcus aureus from bovine mastitis: current understanding and future perspectives

Staphylococcus aureus is a leading cause of bovine mastitis worldwide. Despite some improved understanding of disease pathogenesis, progress towards new methods for the control of intramammary infections (IMI) has been limited, particularly in the field of vaccination. Although herd management programs have helped to reduce the number of clinical cases, S. aureus mastitis remains a major disease burden. This review summarizes the past 16 years of research on bovine S. aureus population genetics, and molecular pathogenesis that have been conducted worldwide. We describe the diversity of S. aureus associated with bovine mastitis and the geographical distribution of S. aureus clones in different continents. We also describe studies investigating the evolution of bovine S. aureus and the importance of host-adaptation in its emergence as a mastitis pathogen. The available information on the prevalence of virulence determinants and their functional relevance during the pathogenesis of bovine mastitis are also discussed. Although traits such as biofilm formation and innate immune evasion are critical for the persistence of bacteria, the current understanding of the key host-pathogen interactions that determine the outcome of S. aureus IMI is very limited. We suggest that greater investment in research into the genetic and molecular basis of bovine S. aureus pathogenesis is essential for the identification of novel therapeutic and vaccine targets.

Molecular detection of vancomycin and methicillin resistance in Staphylococcus aureus isolated from food processing environments

Staphylococcus aureus is a well-known foodborne pathogen. The aim of this study was to investigate the presence of S. aureus isolated from serving utensils in food processing environments in Mymensingh city, Bangladesh and to determine their antibiogram and resistance determinants. A total of 120 environmental samples were collected from different food settings. Isolation and identification were conducted using conventional biochemical tests. Molecular identification of isolates and detection of methicillin and vancomycin resistance were done using primer-specific polymerase chain reaction (PCR) targeting Tuf, nuc, mecA, and mecC genes. Antibiotic sensitivity tests were performed, and resistance genes were also detected by amplifying bla TEM , vanA, vanB, and vanC genes. Among the 120 samples, 81 (67.5%) were positive for Staphylococcus spp. and 41 (50.62%) were positive for the nuc-gene. Among the 41 isolates, 5 (12.20%) were positive for mecA, but none were positive for the mecC gene. A total of 12.2% of the isolates were vanC-positive, of which 4 isolates (9.76%) were also positive for the mecA gene. Antibiotic sensitivity testing revealed that all S. aureus isolates (100%) from hotel samples were sensitive to ciprofloxacin and chloramphenicol, 90.32% were sensitive to doxycycline, and 80.65% were sensitive to streptomycin. Conversely, all isolates (100%) were resistant to ampicillin, and 29.03% were resistant to vancomycin. All S. aureus isolates obtained from non-hotel samples were susceptible to chloramphenicol, ceftriaxone, ciprofloxacin, doxycycline, meropenem, and vancomycin; however, 40% of isolates were resistant to novobiocin. Among the hotel isolates, 29 (93.55%) of the ampicillin-resistant isolates harbored the blaTEM gene while 5 (55.55%) of the vancomycin-resistant isolates harbored the vanC gene. Four of the five vanC positive isolates were also positive for the mecA gene. The presence of methicillin-resistant S. aureus (MRSA) which is also vancomycin-resistant in food processing environments is a threat to public health. This is the first report on the molecular detection of methicillin and vancomycin-resistant S. aureus isolated from food processing environments in Bangladesh.

Molecular Characterization of Antimicrobial Resistance and Virulence Genes of Bacterial Pathogens from Bovine and Caprine Mastitis in Northern Lebanon

Mastitis is an infectious disease encountered in dairy animals worldwide that is currently a growing concern in Lebanon. This study aimed at investigating the etiology of the main mastitis-causing pathogens in Northern Lebanon, determining their antimicrobial susceptibility profiles, and identifying their antimicrobial resistance (AMR) genes. A total of 101 quarter milk samples were collected from 77 cows and 11 goats presenting symptoms of mastitis on 45 dairy farms. Bacterial identification was carried out through matrix-assisted laser desorption/ionization-time of flight mass spectrometry. Antimicrobial susceptibility was tested by disc diffusion and broth microdilution methods. Molecular characterization included polymerase chain reaction (PCR) screening for genes encoding extended-spectrum beta-lactamases (ESBLs) and plasmid-mediated AmpC among Enterobacterales isolates, and virulence factors among Staphylococcus isolates. Escherichia coli isolates were subjected to phylogenetic typing by a quadruplex PCR method. The most frequently identified species were Streptococcus uberis (19.2%), Streptococcus agalactiae (15.1%), E. coli (12.3%), and Staphylococcus aureus (10.96%). Gram-positive bacteria were resistant to macrolides and tetracycline, whereas gram-negative bacteria displayed resistance to ampicillin and tetracycline. Two ESBL genes, blaTEM (83.3%) and blaOXA (16.7%), and one AmpC beta-lactamase gene, blaCMY-II (16.7%), were detected among six E. coli isolates, which mainly belonged to phylogenetic group B1. Among Staphylococcus spp., the mecA gene was present in three isolates. Furthermore, four isolates contained at least one toxin gene, and all S. aureus isolates carried the ica operon. These findings revealed the alarming risk of AMR in the Lebanese dairy chain and the importance of monitoring antimicrobial usage.

Detection of methicillin-resistant coagulase-negative staphylococci and PVL/mecA genes in cefoxitin-susceptible Staphylococcus aureus (t044/ST80) from unpasteurized milk sold in stores in Djelfa, Algeria

This study was designed to determine antimicrobial resistance phenotypes and genotypes and virulence factors in Staphylococcus aureus and coagulase-negative staphylococci (CNS) in unpasteurized milk sold in Djelfa, Algeria. Eighty-two unpasteurized cow milk samples were randomly obtained from 82 retail stores in Djelfa and tested to detect staphylococci. Species were identified by biochemical tests and MALDI-TOF. Antimicrobial resistance phenotypes and genotypes were determined by disk diffusion test, PCR, and sequencing. The Staph. aureus isolates were subjected to spa typing, multilocus sequence typing, and detection of virulence genes and the scn gene by PCR and sequencing. Forty-five (54.9%) milk samples were contaminated by staphylococci and 45 isolates were recovered: 10 Staph. aureus (12.2% of total samples) and 35 CNS (42.7%). Resistance to penicillin (blaZ), tetracycline (tetL/tetK), and erythromycin (ermB/msrA/ermC) were the most common phenotypes (genotypes). Three CNS were methicillin-resistant and all were mecA-positive. The Staph. aureus isolates were ascribed to the following lineages [spa type/sequence type/associated clonal complex (number of isolates)]: t267/ST479/CC479 (n = 6), t1510/ST5651/CC45 (n = 1), t359/ST97/CC97/ (n = 1), t346/ST15/CC15 (n = 1), and t044/ST80 (n = 1). The mecA gene was detected in the cefoxitin-susceptible t044/ST80 isolate and co-harbored the lukF/lukS-PV and scn genes. The detection of mecA-PVL-positive Staph. aureus, methicillin-resistant CNS, and multidrug-resistant staphylococcal species indicates a potentially serious health issue and reveals that unpasteurized milk sold in Djelfa city could be a potential vehicle for pathogenic and antimicrobial-resistant staphylococci.

Characterization of Staphylococcus aureus Isolates From Cases of Clinical Bovine Mastitis on Large-Scale Chinese Dairy Farms

Bovine mastitis is a prevalent disease that causes serious economic problems globally in the dairy industry. Staphylococcus aureus is an important pathogen of bovine mastitis. This study was conducted to characterize S. aureus isolates from clinical bovine mastitis cases in large-scale dairy herds in China. S. aureus was isolated from 624 clinical mastitis cases and confirmed by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). In total, 62 S. aureus isolates were obtained. Cluster analysis, genetic diversity, quantification of biofilm formation, antimicrobial resistance, and detection of virulence genes were performed on these isolates of S. aureus. Eight isolates harbored the mecA gene and were sensitive to oxacillin. MALDI-TOF MS cluster analysis revealed that the 62 isolates were divided into three major clusters (I, II, III) and eight main groups (A–H) at the distance level of 700. The agr II was the most prevalent (56.5%). The 62 S. aureus isolates were assigned to seven spa types. The most common spa type was t529(58.1%), followed by t2196 (14.5%), t518 (14.5%), t571(6.5%), t034 (3.2%), t2734 (1.6%), and t730 (1.6%). Five STs were identified from seven representative isolates as follows: ST630/CC8, ST97/CC97, ST50, ST398, and ST705. All isolates had the ability to form biofilm. Antimicrobial resistance was most frequently observed to ciprofloxacin (29%), followed by penicillin (24.2%), and streptomycin (9.6%). All isolates harbored the fnbA, clfB (100%), icaA, and icaD genes. This study provides the basis for the development of bovine mastitis prevention program on large-scale dairy farms.

Toxin Production and Resistance of Staphylococcus Species Isolated from Fermented Artisanal Dairy Products in Benin

Staphylococcus species are considered as one of the major pathogens causing outbreaks of food poisoning. The aim of this work was to assess the toxinogenic and antibiotic susceptibility profiles of the strains of Staphylococcus spp isolated from three types of fermented dairy products (yoghourt, millet dêguê, and couscous dêguê). The isolation of the Staphylococcus strains was performed on selective media, and their identification was done using biochemical and molecular methods. The susceptibility at 15 antibiotics tested was assessed using the disc diffusion method. The immunodiffusion method was used to evaluate the toxin (luk-E/D, luk-S/F, ETA, and ETB) production. Biofilm formation was qualitatively researched on microplates. Less than half (42.77%) of the collected samples were contaminated with Staphylococcus spp. The yoghourt and millet dêguê samples collected in the afternoon were more contaminated than those collected in the morning. The S. aureus, S. capitis, and S. xylosus strains, respectively, were the most present. S. aureus was the only coagulase-positive species identified in our samples. The highest resistance to antibiotics was observed with penicillin (100%) irrespective of the nature of the sample. S. aureus strains were highly (71.4%) resistant to methicillin. The S. aureus strains were the most biofilm-forming (27.6%), followed by S. capitis strains. Panton and Valentine's leukocidin (luk-S/F) was produced by only S. aureus strains at a rate of 8.33%. Only coagulase-negative Staphylococcus (CNS) produced Luk-E/D. The high rates of Staphylococci contamination indicate bad hygiene quality during the production and distribution of dairy products. It is, therefore, necessary to improve the quality of fermented milk products.

Staphylococcus aureus From Goats Are Genetically Heterogeneous and Distinct to Bovine Ones

Staphylococcus aureus is one of the major pathogens responsible for intramammary infections in small ruminants, causing severe economic losses in dairy farms. In addition, S. aureus can contaminate milk and dairy products and produce staphylococcal enterotoxins, being responsible for staphylococcal food poisoning. Currently, data on the population structure and the virulence gene patterns of S. aureus strains isolated from goat milk is limited. Therefore, this study aimed at defining Ribosomal Spacer PCR (RS-PCR) genotypes, clonal complexes (CC), spa types, and virulence gene profiles of S. aureus isolated from goat milk samples from Lombardy region of Italy. A total of 295 S. aureus isolates from 65 goat bulk tank milk samples were genotyped by RS-PCR. spa typing and virulence gene patterns of a subgroup of 88 isolates were determined, and MLST was performed on a further subgroup of 39 isolates, representing all the spa types identified during the analysis. This study revealed 7 major genotypic clusters (CLR, CLAA, CLZ, CLAW, CLBW, CLS, and CLI), of which S. aureus CLR (19.8%) was the most common. A total of 26 different spa types were detected, the most prevalent types were t1773 (24%), t5428 (22.7%), and t2678 (12.5%). Overall, 44.3% of all isolates harbored at least one enterotoxin gene. The most prevalent was the combination of sec-sel genes (35.2%). Based on their MLST, isolates were assigned to 14 different CC, with majority grouped as CC133 (24%), CC130 (19.6%), and CC522 (19.6%). The caprine S. aureus population was depicted with a minimum spanning tree and an evolutionary analysis based on spa typing and MLST, respectively. Then, the variability of such strains was compared to that of bovine strains isolated in the same space-time span. Our results confirmed that S. aureus isolates from goats have wide genetic variability and differ from the bovine strains, supporting the idea that S. aureus from small ruminants may constitute a distinct population.

Antimicrobial resistance genes in bacteria from animal-based foods

Antimicrobial resistance is a worldwide public health threat. Farm animals are important sources of bacteria containing antimicrobial resistance genes (ARGs). Although the use of antimicrobials in aquaculture and livestock has been reduced in several countries, these compounds are still routinely applied in animal production, and contribute to ARGs emergence and spread among bacteria. ARGs are transmitted to humans mainly through the consumption of products of animal origin (PAO). Bacteria can present intrinsic resistance, and once antimicrobials are administered, this resistance may be selected and multiply. The exchange of genetic material is another mechanism used by bacteria to acquire resistance. Some of the main ARGs found in bacteria present in PAO are the bla, mcr-1, cfr and tet genes, which are directly associated to antibiotic resistance in the human clinic.

Methicillin-Resistant Staphylococcus Aureus (MRSA) in Poultry Species in Algeria: Long-Term Study on Prevalence and Antimicrobial Resistance

Methicillin-resistant Staphylococcus aureus (MRSA) is a well-known pathogen with a serious impact on human and veterinary public health. To determine antibiotic resistance of MRSA in poultry, 4248 nasal swabs were collected from 840 poultry farms in 18 different Wilayas (provinces) of Algeria. Swabs were collected between 2011 and 2018 from breeding hens, laying hens, broilers, and turkeys. Identification was carried out by the classical culture methods, and the disc diffusion test was used to determine the antibiotic resistance patterns. S. aureus was isolated from 477 (56.8%) farms, and flock prevalence was 52.8%, 48.8%, 48.4%, and 75.6% in breeding hens, laying hens, broilers, and turkeys, respectively. MRSA was isolated from 252 (30%) farms and flock prevalence was 22%, 33.5%, 27.4%, and 36%, respectively. As expected, all MRSA isolates were resistant to cefoxitin, penicillin G, amoxicillin/clavulanic acid, and oxacillin. High levels of resistance were found for tetracycline (82.5%), erythromycin (70.6%), clindamycin (68.6%), and ciprofloxacin (50%). Almost all isolates were susceptible to vancomycin (100%) and mupirocin and rifampicin (99.2%), followed by chloramphenicol (82.3%), and gentamicin (76%). This moderate proportion of MRSA in poultry poses a considerable risk to public health. The results of this study highlight the need for control programs that encompass primary animal production and the food chain to mitigate contamination and spread of MRSA in the poultry industry of Algeria, and consequently to humans.

Burden and antimicrobial resistance of S. aureus in dairy farms in Mekelle, Northern Ethiopia

Background

Staphylococcus aureus is a frequent colonizer of human and several animal species, including dairy cows. It is the most common cause of intramammary infections in dairy cows. Its public health importance increases inline to the continuous emergence of drug-resistant strains; such as Methicillin-resistant S. aureus (MRSA). Indeed, the recent emergence of human and veterinary adapted MRSA demands serious attention. The aim of this study was to determine the burden and drug resistance pattern of S. aureus in dairy farms in Mekelle and determine the molecular characteristics of MRSA.

Results

This study was done on 385 lactating dairy cows and 71 dairy farmers. The ages of the cows and farmworkers were between 3 and 14 and 17–63 years respectively. S. aureus was isolated from 12.5% of cows and 31% of farmworkers. Highest resistance was observed for penicillin (> 90%) followed by tetracycline (32–35%) and trimethoprim-sulphamethoxazole (10–27%). But no resistance was observed for vancomycin, daptomycin, and rifampin. Only one isolate was MRSA both phenotypically and harboring mecA. This isolate was from nasal of a farmworker and was MRSA SCCmec Iva, spa type t064 of CC8. Multi-drug resistance was observed in 6.2% of cow isolates and 13.6% of nasal isolates.

Conclusions

In this study, S. aureus infected 12.5% of dairy cows and colonized 31% of farmworkers. Except for penicillin, resistance to other drugs was rare. Although no MRSA was found from dairy cows the existence of the human and animal adapted and globally spread strain, MRSA SCCmec IVa spa t064, warrants for a coordinated action to tackle AMR in both human and veterinary in the country.

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.

Prevalence of meticillin-resistant and -susceptible coagulase-negative staphylococci with the first detection of the mecC gene among cows, humans and manure in Tunisia

In Europe, a novel mecA homologue - mecC (formerly mecA_LGA251) - has emerged recently in staphylococci from animals, humans and the environment. This paper reports the first occurrence of the mecC gene in Staphylococcus sciuri from cows and manure in Tunisia and Africa. Forty-nine coagulase-negative staphylococci (CNS) were isolated from the milk of cows with mastitis (n=20), manure (n=20) and human nares (n=9), including 16 Staphylococcus equoruim (32.6%), 12 S. xylosus (24.5%), 12 S. sciuri (24.5%), two S. saprophyticus (4.1%), two S. haemolyticus (4.1%), two S. lentus (4.1%), two S. vitulinus (4.1%) and one S. cohnii (2%). CNS from the three origins carried various resistance genes [mecA, blaZ, tet(K), erm(A), erm(B), msr(A)], suggesting an ongoing genetic exchange among CNS from the three niches. The mecA gene was detected in CNS (n=11) recovered from cows, manure and humans, whereas the mecC gene (n=3) was only detected in CNS from cows and manure. Various staphylococcal cassette chromosome mec (SCCmec) - SCCmec type I (n=1), II (n=3), IV (n=2), V/VII (n=2) and untypeable (n=3) - and diverse pulsed-field gel electrophoresis (PFGE) patterns were observed in mecA-positive CNS. Otherwise, similar SCCmec types and PFGE patterns were found in meticillin-resistant CNS within different farms and origins, showing the potential of SCCmec interspecies exchange and circulation of the same clones of meticillin-resistant CNS in the human-animal-environment interface. This study provides baseline data to support clonal dissemination of CNS between cows, humans and manure, and indicates the possible transmission of the mecC gene to humans in contact with cows and manure.

Identification of staphylococci causing mastitis in dairy cattle from Algeria and characterization of Staphylococcus aureus

AIMS

This study was conducted to determine the occurrence of staphylococci from cows with subclinical mastitis from independent herds in Algeria, and to characterize Staphylococcus aureus isolates.

METHODS AND RESULTS

Quarter milk samples were collected separately, somatic cells were counted and samples with more than 200 000 somatic cells per ml were cultured on blood agar. Staphylococci isolates were identified by routine diagnostics, and S. aureus isolates were tested for antibiotic susceptibility by disk diffusion and microdilution. Congo red agar was used to detect biofilm formation and capsule synthesis was detected on serum soft agar (SSA). The S. aureus isolates were characterized by spa typing. DNA microarray analysis was performed to detect resistance and virulence genes. Overall, 40·0% (167/418) of the cows suffered from mastitis. In 63·5% (106/167) of the cows staphylococci were identified. Nine of the 106 Staphylococcus isolates (8·5%) were S. aureus. The coagulase-negative staphylococci belonged to 14 species. All S. aureus isolates were multiresistant and biofilm forming, with 66·67% of them showing diffuse colonies on SSA and belonged to CC97-agrI-cap5. Biofilm genes (icaA/C/D), 13 genes encoding for adhesion, six genes encoding proteases, 11 genes encoding superantigen like toxins were found. Genes conferring resistance to tetracycline (tet(K)), penicillin (blaZ/I/R) and macrolide-lincosamide-streptogramin B (erm(B), erm(A)) were also detected in the S. aureus from this study.

CONCLUSIONS

The current investigation provides a detailed molecular and biofilm formation ability of S. aureus involved in subclinical mastitis in Algeria and shows the wide distribution of adhesion and enterotoxin(-like) genes among S. aureus responsible for causing subclinical bovine mastitis.

SIGNIFICANCE AND IMPACT OF THE STUDY

These findings are valuable in tracking the evolution and genomic variation of S. aureus from bovine origin.

High occurrence of enterotoxigenic isolates and low antibiotic resistance rates of Staphylococcus aureus isolated from raw milk from cows and ewes

This study aimed to analyse the frequency of genes encoding virulence factors and to characterize resistance profiles of Staphylococcus aureus isolated from raw milk. In total, 47 and 9 S. aureus isolates were recovered from 150 and 100 raw bovine and ovine milk samples, respectively, in Tunisia. The majority of isolates was resistant to penicillin, and no methicillin-resistant S. aureus was detected. Eighteen and two isolates harboured etd and eta genes respectively. Sixteen enterotoxin-encoding genes were detected (n, %): sed (25, 44·6%), sec (16, 28·6%), sei (16, 28·6%), seh (13, 23·2%), seln (13, 23·2%), sell (10, 17·8%), seg (9, 16%), selu (8, 14·3%), selq (7, 12·5%), selo (7, 12·5%), selm (7, 12·5%), seb (7, 12·5%), sea (6, 10·7%), selk (3, 5·4%), ser (1, 1·8%) and selp (1, 1·8%). Ten isolates carried the tsst1 gene. All isolates carried the haemolysin toxin (hla, hld and hlg). The immune evasion cluster system-type B was predominant (20 isolates) followed by C (3 isolates), A and E (1 isolate each). The occurrence of enterotoxigenic S. aureus in raw milk constitutes a potential risk for human health. SIGNIFICANCE AND IMPACT OF THE STUDY: This paper describes the characteristics of Staphylococcus aureus isolated from raw milk samples from healthy cows and ewes collected from small family farms in Tunisia. Fifty-six strains were analysed by determining their antibiotic susceptibility and genes encoding antibiotic resistance and virulence factors. Methicillin-resistant strains were not detected, and overall low level of antimicrobial resistance was reported. However, our strains harboured several genes encoding virulence factors and 87·5% of them carried at least one gene encoding for enterotoxins showing a high risk of spread of food-borne diseases.

Staphylococcus aureus Isolates from Bovine Mastitis in Eight Countries: Genotypes, Detection of Genes Encoding Different Toxins and Other Virulence Genes

Staphylococcus aureus is recognized worldwide as one of the major agents of dairy cow intra-mammary infections. This microorganism can express a wide spectrum of pathogenic factors used to attach, colonize, invade and infect the host. The present study evaluated 120 isolates from eight different countries that were genotyped by RS-PCR and investigated for 26 different virulence factors to increase the knowledge on the circulating genetic lineages among the cow population with mastitis. New genotypes were observed for South African strains while for all the other countries new variants of existing genotypes were detected. For each country, a specific genotypic pattern was found. Among the virulence factors, fmtB, cna, clfA and leucocidins genes were the most frequent. The sea and sei genes were present in seven out of eight countries; seh showed high frequency in South American countries (Brazil, Colombia, Argentina), while sel was harboured especially in one Mediterranean country (Tunisia). The etb, seb and see genes were not detected in any of the isolates, while only two isolates were MRSA (Germany and Italy) confirming the low diffusion of methicillin resistance microorganism among bovine mastitis isolates. This work demonstrated the wide variety of S. aureus genotypes found in dairy cattle worldwide. This condition suggests that considering the region of interest might help to formulate strategies for reducing the infection spreading.

Characterization of Staphylococcus aureus Isolated from Food Products in Western Algeria

The current study aimed to characterize Staphylococcus aureus isolates from foodstuffs collected from western Algeria. A total of 153 S. aureus isolates from various raw and processed foods were obtained and identified using matrix-assisted laser desorption and ionization time-of-flight mass spectrometry. Isolates were characterized by antimicrobial susceptibility testing and toxin gene detection. Methicillin-resistant Staphylococcus aureus (MRSA) isolates were identified by detection of the mecA gene and characterized by staphylococcal cassette chromosome mec (SCCmec) typing. We found that 30.9% (153/495) of food samples were contaminated with S. aureus. Thirty-three (21.5%) S. aureus isolates were identified as MRSA, and 16.9% (26/153) carried the mecA gene. Three SCCmec types were identified of which type IV was the most common (69.2%) followed by type V (15.3%) and type II (7.6%). Two MRSA isolates were not typable with SCCmec typing. None of the examined isolates harbored mecC. Furthermore, 14.3% (22/153) of the isolates were toxigenic S. aureus. The cytotoxin gene pvl was detected in 11.1% of the S. aureus isolates. This gene was more commonly detected (76.4%) in MRSA isolates than in methicillin-suceptible Staphylococcus aureus (MSSA) isolates. The tsst-1 gene coding for toxic shock syndrome toxin was isolated rarely (3.2%) and only in MSSA isolates. According to disk diffusion test results, 70 isolates were resistant to only one antimicrobial drug, and 51 (33.3%) isolates were multidrug resistant. Other 32 isolates were susceptible to all antibiotics. Our study highlights, for the first time, a high prevalence of multidrug-resistant S. aureus isolates carrying pvl or tsst-1 found in food products in Algeria. The risk of MRSA transmission through the food chain cannot be disregarded, particularly in uncooked foods.