MRSA in swine, farmers and abattoir workers in Southern Italy

Presence and Resistance Profile of Staphylococcus spp. Isolated from Slaughtered Pigs

Background: The objective of this study was to isolate Staphylococcus spp. and to characterize the resistance profile in nasal samples from pigs slaughtered for consumption. Material and Methods: Intranasal swabs were collected from 100 pigs immediately after bleeding in a slaughterhouse located in the largest pork production region in Brazil, these samples were cultured and isolated to identify Staphylococcus spp. in coagulase positive (CoPS) and coagulase negative (CoNS) and molecular identification of Staphylococcus aureus and then subjected to the disk-diffusion test to identify the bacterial resistance profile and search for the mecA gene. Results: Of the 100 samples collected, it was possible to isolate 79 Staphylococcus spp., of these, 72.15% were classified as CoNS and 27.85% of the isolates classified as CoPS. Among the CoPS isolates, 77.27% were identified as S. aureus. Through the disk-diffusion test, it was possible to verify isolates resistant to clindamycin and erythromycin (98.73%), chloramphenicol (93.67%), and doxycycline (89.87%). There was amplification of the mecA gene in 30.38% of Staphylococcus spp. Conclusion: The results of this study highlight the need for the careful use of antibiotics in swine production, in addition to aiming at continuous surveillance in relation to the rate of multiresistant microorganisms within these environments, focused on large industrial centers; such results also indicate the importance of understanding, through future studies, possible pathways to transmission of these microorganisms directly, or indirectly, through meat products derived from these pigs, which can be considered neglected diffusers of variants of Staphylococcus spp. resistant to antibiotics or carriers of important resistance genes related to One Health.

Heterogeneity and transmission of food safety-related enterotoxigenic Staphylococcus aureus in pig abattoirs in Hubei, China

The dissemination of Staphylococcus aureus in the pork production chain is a major food safety concern. Abattoirs can serve both as disruptor and transmitter for S. aureus. In this study, we conducted a systematic genomic epidemiology research on the prevalence, heterogeneity, and transmission of S. aureus in 3,638 samples collected from four pig abattoirs in Hubei province, China. Our findings revealed substantial heterogeneity between S. aureus recovered from samples collected at upstream (from stunning step to head-removal step) and downstream (from splitting step to chilling step) locations within the slaughter process. Overall, 966 (26.6%) samples were positive for S. aureus, with significantly higher overall prevalence for upstream samples (29.0%, 488/1,681) compared to downstream samples (24.4%, 478/1,957). Antimicrobial susceptibility testing demonstrated that the isolates from the upstream exhibited significantly higher resistance proportions to different antimicrobials than those from the downstream. Whole-genome sequencing of 126 isolates revealed that ST398 (32.9%, 23/70) and ST9 (22.9%, 16/70) were more common among upstream isolates, while ST7 (35.7%, 20/56) and ST97 (28.6%, 16/56) were most frequently observed among downstream isolates. Additionally, molecular characterization analysis demonstrated that upstream isolates possessed significantly higher enterotoxigenic potential, more antimicrobial resistance genes, and S. aureus pathogenicity islands than downstream isolates. Notably, we discovered that enterotoxigenic S. aureus could be transmitted across different slaughter stages, with knives, water, and air serving as vectors. Although slaughtering processes had a substantial effect on reducing the food safety risk posed by enterotoxigenic S. aureus, the possibility of its widespread transmission should not be disregarded. IMPORTANCE Staphylococcus aureus (S. aureus) is one of the most important foodborne pathogens, and can cause foodborne poisoning by producing enterotoxins. Pork is a preferable reservoir and its contamination often occurs during the slaughter process. Our findings revealed significant differences in the prevalence, antimicrobial resistance, and enterotoxigenic potential between the upstream and downstream isolates within the slaughter process. Also, it is imperative not to overlook enterotoxigenic S. aureus transmitted across all stages of the slaughter process, with notable vectors being knives, water, and air. These findings hold significant implications for policy-makers to reassess their surveillance projects, and underscore the importance of implementing effective control measures to minimize the risk of S. aureus contamination in pork production. Moreover, we provide a more compelling method of characterizing pathogen transmission based on core-SNPs of bacterial genomes.

Methicillin-resistant and methicillin-sensitive Staphylococcus aureus in pork industry workers, Catalonia, Spain

Background

Methicillin-resistant S. aureus (MRSA) especially ST398, is a zoonotic agent. This study aimed to determine the prevalence of methicillin-susceptible S. aureus (MSSA) and MRSA among workers in the pork production chain.

Methods

659 workers associated with 123 pig farms, livestock transporters, one pig slaughterhouse, pork transporters and 23 pork butcheries were studied for S. aureus recovery, and all isolates were characterized (antibiotic resistance, MLST and spa-typing).

Results

The prevalence of S. aureus was 35.5%, 75.6% of isolates being MRSA. The prevalence of MRSA was 68.7% (149/217) among pig farm, 33.9% (19/56) livestock transporters, 2.9% (9/306) slaughterhouse, 0% in pork transporters (0/36) and butchery workers (0/44). Of the 234 S. aureus-positive workers, 100% (149/149) of pig farm workers, 82.6% (19/23) of livestock transporters, and 16.4% (9/55) of slaughterhouse workers carried MRSA isolates (p < 0.001). Of the workers who had contact with live swine, 61.8% (178/288) were S. aureus-positive, MRSA being detected in 96.1% of cases (p < 0.001). The most frequent lineage among MRSA were: ST398 (97.7%; 173/177) and ST1 (1.7%; 3/177); and among MSSA were ST30 (19.2%; 11/57) and ST5 (10.5%; 6/57). The most frequent spa-types among MRSA were t011 (93.8%, 166/177) and t1451 (2.25%, 4/177), and among MSSA: t084 (10.5%, 6/57) and t021 (7.0%, 4/57). All MRSA isolates showed resistance to tetracycline, 92.7% to clindamycin, 81.9% to erythromycin and 40.1% to cotrimoxazole.

Conclusions

Pig industry workers having occupational contact with live animals present a high risk of colonization of MRSA, especially by MRSA-ST398. Prevention measures should be intensified in any employment sector involving live animals.

Biosecurity and Hygiene Procedures in Pig Farms: Effects of a Tailor-Made Approach as Monitored by Environmental Samples

In livestock, the importance of hygiene management is gaining importance within the context of biosecurity. The aim of this study was to monitor the implementation of biosecurity and hygiene procedures in 20 swine herds over a 12-month period, as driven by tailor-made plans, including training on-farm. The measure of adenosine triphosphate (ATP) environmental contents was used as an output biomarker. The presence of livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) and extended-spectrum β-lactamase producing Escherichia coli (ESBL-E. coli) was also investigated as sentinels of antibiotic resistance. A significant biosecurity improvement (p = 0.006) and a reduction in the ATP content in the sanitised environment (p = 0.039) were observed. A cluster including 6/20 farms greatly improved both biosecurity and ATP contents, while the remaining 14/20 farms ameliorated them only slightly. Even if the ESBL-E. coli prevalence (30.0%) after the hygiene procedures significantly decreased, the prevalence of LA-MRSA (22.5%) was unaffected. Despite the promising results supporting the adoption of tailor-made biosecurity plans and the measure of environmental ATP as an output biomarker, the high LA-MRSA prevalence still detected at the end of the study underlines the importance of improving even more biosecurity and farm hygiene in a one-health approach aimed to preserve also the pig workers health.

Staphylococcus aureus and MRSA in Livestock: Antimicrobial Resistance and Genetic Lineages

Animal production is associated with the frequent use of antimicrobial agents for growth promotion and for the prevention, treatment, and control of animal diseases, thus maintaining animal health and productivity. Staphylococcus aureus, in particular methicillin-resistant S. aureus (MRSA), can cause a variety of infections from superficial skin and soft tissue infections to life-threatening septicaemia. S. aureus represents a serious public health problem in hospital and community settings, as well as an economic and animal welfare problem. Livestock-associated MRSA (LA-MRSA) was first described associated with the sequence (ST) 398 that was grouped within the clonal complex (CC) 398. Initially, LA-MRSA strains were restricted to CC398, but over the years it has become clear that its diversity is much greater and that it is constantly changing, a trend increasingly associated with multidrug resistance. Therefore, in this review, we aimed to describe the main clonal lineages associated with different production animals, such as swine, cattle, rabbits, and poultry, as well as verify the multidrug resistance associated with each animal species and clonal lineage. Overall, S. aureus ST398 still remains the most common clone among livestock and was reported in rabbits, goats, cattle, pigs, and birds, often together with spa-type t011. Nevertheless, a wide diversity of clonal lineages was reported worldwide in livestock.

Prevalence, Infectious Characteristics and Genetic Diversity of Staphylococcus aureus and Methicillin-Resistant Staphylococcus aureus (MRSA) in Two Raw-Meat Processing Establishments in Northern Greece

In the present study, we investigated the isolation frequency, the genetic diversity, and the infectious characteristics of Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) from the incoming meat and the meat products, the environment, and the workers' nasal cavities, in two meat-processing establishments in northern Greece. The isolated S. aureus strains were examined for their resistance to antimicrobials, carriage of the mecA and mecC genes, carriage of genes encoding for the production of nine staphylococcal enterotoxins, carriage of the Panton-Valentine Leukocidin and Toxic Shock Syndrome genes, and the ability to form biofilm. The genetic diversity of the isolates was evaluated using Pulsed Field Gel Electrophoresis (PFGE) and spa typing. S. aureus was isolated from 13.8% of the 160 samples examined, while only one sample (0.6%) was contaminated by MRSA carrying the mecA gene. The evaluation of the antimicrobial susceptibility of the isolates revealed low antimicrobial resistance. The higher resistance frequencies were observed for penicillin (68.2%), amoxicillin/clavulanic acid (36.4%) and tetracycline (18.2%), while 31.8% of the isolates were sensitive to all antimicrobials examined. Multidrug resistance was observed in two isolates. None of the isolates carried the mecC or lukF-PV genes, and two isolates (9.1%) harbored the tst gene. Eight isolates (36.4%) carried the seb gene, one carried the sed gene, two (9.1%) carried both the sed and sei genes, and one isolate (4.5%) carried the seb, sed and sei genes. Twenty-one (95.5%) of the isolates showed moderate biofilm production ability, while only one (4.5%) was characterized as a strong biofilm producer. Genotyping of the isolates by PFGE indicates that S. aureus from different meat-processing establishments represent separate genetic populations. Ten different spa types were identified, while no common spa type isolates were detected within the two plants. Overall, our findings emphasize the need for the strict application of good hygienic practices at the plant level to control the spread of S. aureus and MRSA to the community through the end products.

New clues about the global MRSA ST398: Emergence of MRSA ST398 from pigs in Qinghai, China

This study, a part of the China national surveillance program on antimicrobial resistance in zoonotic bacteria, was to determine the phenotypic and genomic characteristics of endemic pig-associated Staphylococcus aureus ST398 strains in China. A total of 68 (48.9 %) S. aureus strains were recovered from 139 samples collected from two pig farms and one slaughterhouse in Qinghai province. Genomic characterization of All S. aureus strains was performed by WGS and their evolutionary relationships were assessed by phylogenetic analysis. Their susceptibilities to antimicrobials were determined using the broth dilution method. All S. aureus strains consisted of 41 ST398-t571 MSSA, 26 ST398-t011 MRSA and 1 ST5-t002 MRSA. Among these, ST398 was frequently identified in 67 S. aureus strains, suggesting that ST398 was a frequent source of MRSA and MSSA infections in Qinghai province and its possibility of transmission between individuals in pigs from farms and slaughterhouse. Meanwhile, Livestock-associated-MRSA ST398 in our study was establishing closely evolutionary relationships with MRSA ST 398 in Europe and Australia. The clues about closely relatedness of the global S. aureus ST398 underscore the potential public health risk of S. aureus ST398 in the pork supply chain and offer significant guidance for veterinary and human health.

Occurrence and Distribution of Antibiotic-Resistant Staphylococcus aureus in a Brazilian Pork Production Chain

ABSTRACT

Here we characterized the distribution and the antibiotic resistance of staphylococci from a Brazilian pork production chain. Samples (n = 1,114) from pig farms, pig lots, and slaughterhouses, located in two Brazilian states (Minas Gerais and Paraná), were subjected to coagulase-positive Staphylococcus enumeration. S. aureus isolates (n = 251) from this collection were further characterized for their resistance to oxacillin, cefoxitin, vancomycin, and tetracycline through phenotypic and molecular assays. Coagulase-positive Staphylococcus counts from pig farms were higher compared with other samples (P < 0.05). Other counts were relatively low but were present in all production stages. S. aureus isolates were commonly resistant to oxacillin and cefoxitin (54 of 73, 74.0%), qualifying them as methicillin-resistant S. aureus, but PCR assays indicated that few harbored the expected antimicrobial resistance genes (femB, mecA, and mecC). Lower frequencies of vancomycin and tetracycline resistance were found (6.8 to 37.0%). PCR sensitivity (34.5 to 86.7%) and specificity (26.6 to 85.0%) for detection of antibiotic resistance genes varied based on the assessed antibiotic. Antibiotic-resistant staphylococci are widely distributed in the Brazilian pork production chain, and methicillin-resistant S. aureus can become a potential health and economic impediment for the Brazilian pork industry.

HIGHLIGHTS

Oxidative Stress-Mediated Antibacterial Activity of the Total Flavonoid Extracted from the Agrimonia pilosa Ledeb. in Methicillin-Resistant Staphylococcusaureus (MRSA)

(1) Background: Methicillin-resistant Staphylococcus aureus (MRSA) is a zoonotic pathogen that causes endocarditis, pneumonia, and skin diseases in humans and livestock. (2) Methods: The antibacterial effect of the total flavonoid against MRSA (ATCC43300) extracted from the Agrimonia pilosa Ledeb. (A. pilosa Ledeb) was evaluated by the microdilution method. The oxidative stresses in MRSA were evaluated by the levels of intracellular hydrogen peroxide (H₂O₂), reactive oxygen species (ROS), and oxidative stress-related genes. The DNA oxidative damage was tested by the 8-hydroxy-2′-deoxyguanosine (8-OHdG) and DNA gel electrophoresis. The differentially expressed proteins were determined by the method of SDS-PAGE and NanoLC-ESI-MS/MS, while the mRNAs of differential proteins were determined by Real-Time PCR. The changes of ultra-structures in MRSA were observed by Transmission Electron Microscope (TEM). (3) Results: The minimum inhibitory concentration (MIC) of the total flavonoid against MRSA was recorded as 62.5 μg/mL. After treatment with the total flavonoid, the levels of intracellular H₂O₂ and ROS were increased and the gene expressions against oxidative stress (SodA, katA, TrxB) were decreased (p < 0.01), while the gene expression for oxidative stress (PerR) was increased (p < 0.01). The level of intracellular 8-OHdG in MRSA was increased (p < 0.01) and the DNA was damaged. The results of TEM also showed that the total flavonoid could destroy the ultra-structures in the bacteria. (4) Conclusions: The total flavonoid extracted from the A. pilosa Ledeb can induce the oxidative stress that disturbed the energy metabolism and protein synthesis in MRSA.

A Survey of Chinese Pig Farms and Human Healthcare Isolates Reveals Separate Human and Animal Methicillin-Resistant Staphylococcus aureus Populations

There has been increasing concern that the overuse of antibiotics in livestock farming is contributing to the burden of antimicrobial resistance in people. Farmed animals in Europe and North America, particularly pigs, provide a reservoir for livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA ST398 lineage) found in people. This study is designed to investigate the contribution of MRSA from Chinese pig farms to human infection. A collection of 483 MRSA are isolated from 55 farms and 4 hospitals in central China, a high pig farming density area. CC9 MRSA accounts for 97.2% of all farm isolates, but is not present in hospital isolates. ST398 isolates are found on farms and hospitals, but none of them formed part of the "LA-MRSA ST398 lineage" present in Europe and North America. The hospital ST398 MRSA isolate form a clade that is clearly separate from the farm ST398 isolates. Despite the presence of high levels of MRSA found on Chinese pig farms, the authors find no evidence of them spilling over to the human population. Nevertheless, the ST398 MRSA obtained from hospitals appear to be part of a widely distributed lineage in China. The new animal-adapted ST398 lineage that has emerged in China is of concern.

Disinfectant and Antimicrobial Susceptibility Studies of Staphylococcus aureus Strains and ST398-MRSA and ST5-MRSA Strains from Swine Mandibular Lymph Node Tissue, Commercial Pork Sausage Meat and Swine Feces

Staphylococcus aureus (S. aureus) causes gastrointestinal illness worldwide. Disinfectants are used throughout the food chain for pathogenic bacteria control. We investigated S. aureus bioavailability in swine Mandibular lymph node tissue (MLT) and pork sausage meat (PSM), established susceptibility values for S. aureus to disinfectants, and determined the multilocus sequence type of MRSA strains. Antimicrobial and disinfectant susceptibility profiles were determined for 164 S. aureus strains isolated from swine feces (n = 63), MLT (n = 49) and PSM (n = 52). No antimicrobial resistance (AMR) was detected to daptomycin, nitrofurantoin, linezolid, and tigecycline, while high AMR prevalence was determined to erythromycin (50.6%), tylosin tartrate (42.7%), penicillin (72%), and tetracycline (68.9%). Methicillin-resistant S. aureus (MRSA) strains, ST398 (n = 6) and ST5 (n = 1), were found in the MLT and PSM, 4 MRSA in MLT and 3 MRSA strains in the PSM. About 17.5% of feces strains and 41.6% of MLT and PSM strains were resistant to chlorhexidine. All strains were susceptible to triclosan and benzalkonium chloride, with no cross-resistance between antimicrobials and disinfectants. Six MRSA strains had elevated susceptibilities to 18 disinfectants. The use of formaldehyde and tris(hydroxylmethyl)nitromethane in DC&R was not effective, which can add chemicals to the environment. Didecyldimethylammonium chloride and benzyldimethylhexadecylammonium chloride were equally effective disinfectants. ST398 and ST5 MRSA strains had elevated susceptibilities to 75% of the disinfectants tested. This study establishes susceptibility values for S. aureus strains from swine feces, mandibular lymph node tissue, and commercial pork sausage against 24 disinfectants. Since it was demonstrated that S. aureus and MRSA strains can be found deep within swine lymph node tissue, it may be beneficial for the consumer if raw swine lymph node tissue is not used in uncooked food products and pork sausage.

Ecology and Genetic Lineages of Nasal Staphylococcus aureus and MRSA Carriage in Healthy Persons with or without Animal-Related Occupational Risks of Colonization: A Review of Global Reports

In this conceptual review, we thoroughly searched for appropriate English articles on nasal staphylococci carriage among healthy people with no reported risk of colonization (Group A), food handlers (Group B), veterinarians (Group C), and livestock farmers (Group D) published between 2000 and 2021. Random-effects analyses of proportions were performed to determine the pooled prevalence of S. aureus, MRSA, MRSA-CC398, and MSSA-CC398, as well as the prevalence of PVL-positive S. aureus from all eligible studies. A total of 166 eligible papers were evaluated for Groups A/B/C/D (n = 58/31/26/51). The pooled prevalence of S. aureus and MRSA in healthy humans of Groups A to D were 15.9, 7.8, 34.9, and 27.1%, and 0.8, 0.9, 8.6, and 13.5%, respectively. The pooled prevalence of MRSA-CC398 nasal carriage among healthy humans was as follows: Group A/B (<0.05%), Group C (1.4%), Group D (5.4%); and the following among Group D: pig farmers (8.4%) and dairy farmers (4.7%). The pooled prevalence of CC398 lineage among the MSSA and MRSA isolates from studies of the four groups were Group A (2.9 and 6.9%), B (1.5 and 0.0%), C (47.6% in MRSA), and D (11.5 and 58.8%). Moreover, MSSA-CC398 isolates of Groups A and B were mostly of spa-t571 (animal-independent clade), while those of Groups C and D were spa-t011 and t034. The MRSA-CC398 was predominately of t011 and t034 in all the groups (with few other spa-types, livestock-associated clades). The pooled prevalence of MSSA and MRSA isolates carrying the PVL encoding genes were 11.5 and 9.6% (ranges: 0.0-76.9 and 0.0-28.6%), respectively. Moreover, one PVL-positive MSSA-t011-CC398 isolate was detected in Group A. Contact with livestock and veterinary practice seems to increase the risk of carrying MRSA-CC398, but not in food handlers. Thus, this emphasizes the need for integrated molecular epidemiology of zoonotic staphylococci.

Comparative analysis of genomic characteristics, fitness and virulence of MRSA ST398 and ST9 isolated from China and Germany

Methicillin-resistant Staphylococcus aureus (MRSA) of sequence types ST398 and ST9 are dominant lineages among livestock in Europe and Asia, respectively. Although both STs were commonly found as colonizers of the skin and the mucosal membranes, MRSA ST398, rather than MRSA ST9, has been reported to cause infections in humans and animals. Herein, we comparatively analyzed the genomic characteristics, fitness and virulence of MRSA ST398 and ST9 isolated from pigs in both China (CHN) and Germany (GER) to explore the factors that lead to differences in their epidemics and pathogenicity. We observed that the CHN-MRSA ST9 and the GER-MRSA ST9 have evolved independently, whereas the CHN-MRSA ST398 and GER-MRSA ST398 had close evolutionary relationships. Resistance to antimicrobial agents commonly used in livestock, the enhanced ability of biofilm formation, and the resistance to desiccation contribute to the success of the dominant clones of CHN-MRSA ST9 and GER-MRSA ST398, and the vwb^νSaα gene on the genomic island might in part contribute to their colonization fitness in pigs. All MRSA ST398 strains revealed more diverse genome structures, higher tolerance to acids and high osmotic pressure, and greater competitive fitness in co-culture experiments. Notably, we identified and characterized a novel hysA^νSaβ gene, which was located on the genomic island νSaβ of MRSA ST398 but was absent in MRSA ST9. The enhanced pathogenicity of the MRSA ST398 strains due to hysA^νSaβ might in part explain why MRSA ST398 strains are more likely to cause infections.

Occurrence of Methicillin-Resistant Coagulase-Negative Staphylococci (MRCoNS) and Methicillin-Resistant Staphylococcus aureus (MRSA) from Pigs and Farm Environment in Northwestern Italy

Swine farming as a source of methicillin-resistant Staphylococcus aureus (MRSA) has been well documented. Methicillin-resistant coagulase-negative staphylococci (MRCoNS) have been less studied, but their importance as pathogens is increasing. MRCoNS are indeed considered relevant nosocomial pathogens; identifying putative sources of MRCoNS is thus gaining importance to prevent human health hazards. In the present study, we investigated MRSA and MRCoNS in animals and environment in five pigsties in a high farm-density area of northwestern Italy. Farms were three intensive, one intensive with antibiotic-free finishing, and one organic. We tested nasal swabs from 195 animals and 26 environmental samples from three production phases: post-weaning, finishing and female breeders. Phenotypic tests, including MALDI-TOF MS, were used for the identification of Staphylococcus species; PCR and nucleotide sequencing confirmed resistance and bacterial species. MRCoNS were recovered in 64.5% of nasal swabs, in all farms and animal categories, while MRSA was detected only in one post-weaning sample in one farm. The lowest prevalence of MRCoNS was detected in pigs from the organic farm and in the finishing of the antibiotic-free farm. MRCoNS were mainly Staphylococcus sciuri, but we also recovered S. pasteuri, S. haemolyticus, S. cohnii, S. equorum and S. xylosus. Fifteen environmental samples were positive for MRCoNS, which were mainly S. sciuri; no MRSA was found in the farms’ environment. The analyses of the mecA gene and the PBP2-a protein highlighted the same mecA fragment in strains of S. aureus, S. sciuri and S. haemolyticus. Our results show the emergence of MRCoNS carrying the mecA gene in swine farms. Moreover, they suggest that this gene might be horizontally transferred from MRCoNS to bacterial species more relevant for human health, such as S. aureus.

Antimicrobial Resistance and Molecular Characterization of Methicillin-Resistant Staphylococcus aureus Isolated from Slaughtered Pigs and Pork in the Central Region of Thailand

Methicillin-resistant Staphylococcus aureus (MRSA) have been a major public health concern in humans. Among MRSA, livestock-associated (LA)-MRSA strains have always been associated with exposure to livestock or their products and have emerged in different countries globally. Although studies have identified LA-MRSA from healthy pigs and pork in Thailand, prevalence in slaughtered pigs is still unknown. In addition, there are few reports on the epidemiology and molecular characteristics of LA-MRSA in Thailand. Hence, this is the first report investigating the epidemiology and molecular characteristics of MRSA in individual slaughtered pigs and pork in Thailand. A total of 204 nasal swab and 116 retailed pork samples were collected from three slaughterhouses and four fresh markets, respectively. Individual samples were used for screening for MRSA and obtained isolates were examined for drug- resistance profiling for 12 antimicrobial agents of 10 drug classes. In addition, SCCmec typing and multi-locus sequence typing were conducted to obtain genotype profiles. MRSA were isolated from 11 and 52 nasal swab and pork samples, respectively. The prevalence was significantly higher in the pork than in the nasal swab samples (p-value < 0.05). A high prevalence of ST9-SCCmecIX and ST398-SCCmecV with high-level antimicrobial resistance from markets and slaughterhouses indicated the spreading of MRSA with these genotypes in the Thai swine processing chains and suggested the need for further investigation to determine a control.

Treatment of Staphylococcus aureus skin infection in vivo using rifampicin loaded lipid nanoparticles

We have previously reported on a novel nanoparticle formulation that was effective at killing Staphylococcus aureus in vitro. Here, we report for the first time, the antibacterial effects of a lipidic nano-carrier containing rifampicin (NanoRIF) which can be used to successfully treat Methicillin-Resistant S. aureus (MRSA) infection at a reduced antibiotic dosage compared to the free drug in a skin wound model in mice. The formulation used contains the lipid monoolein, a cationic lipid N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium methyl-sulfate (DOTAP) and the antibiotic. We have shown that rifampicin-loaded nanoparticles are more effective at treating infection in the skin wound model than the antibiotic alone. Cryo-TEM was used to capture for the first time, interactions of the formed nanoparticles with the cell wall of an individual bacterium. Our data strongly indicate enhanced binding of these charged nanoparticles with the negatively charged bacterial membrane. The efficacy we have now observed in vivo is of significant importance for the continued development of nanomedicine-based strategies to combat antibiotic resistant bacterial skin infections.

Molecular characterization of Methicillin-resistant Staphylococcus aureus isolated from the pig production chain in Northern Italy

This study aimed to evaluate the molecular characteristics of methicillin resistant Staphylococcus aureus (MRSA) isolated in the swine chain in Northern Italy. A sample of 50 fattening units located in Lombardy was selected. Five cutaneous samples at slaughtering and three environmental samples at farm were collected from each unit giving a total of 250 and 150 samples, respectively. A total of 25 MRSA isolates were isolated from 400 samples, in 17 different fattening units. At farm, 12 out of 250 samples were positive for MRSA (4,8 %), and 13 out of 150 samples at slaughter were identified as MRSA (8,7 %), giving an overall incidence among samples of 6,25 % (n = 25). Molecular characterization was carried out using multi-locus sequence typing (MLST) and spa-typing. Outcomes showed that most of the isolates belonged to ST398, carrying spa-types t899, t011, t18498, t1939, t1200, and t304. Nonetheless, three isolates were identified as ST97 (t1730 and t4795), and one as ST30, showing spa-type t318. Furthermore, a novel ST was identified, namely 5422, showing spa-type t1730. Heterogeneity in genotypes within the same farm was also found in different fattening units, with concern for the possibility of the exchange of genetic determinants among different lineages. Genetic diversity among MRSA isolates in pig fattening units has been observed, highlighting the possibility that some isolates could be able to infect different hosts, including human.

Assessment of the Antibiotic Resistance Profile, Genetic Heterogeneity and Biofilm Production of Methicillin-Resistant Staphylococcus aureus (MRSA) Isolated from The Italian Swine Production Chain

The main aim of the present study was to evaluate the level of antibiotic resistance, prevalence and virulence features of methicillin-resistant Staphylococcus aureus (MRSA) isolated from heavy swine at abattoir level and farming environments in Lombardy (Northern Italy). With this scope, 88 different heavy swine farms were surveyed, obtaining a total of n = 440 animal swabs and n = 150 environmental swabs. A total of n = 87 MRSA isolates were obtained, with an overall MRSA incidence of 17.50% (n = 77) among animal samples and a 6.67% (n = 10) among environmental. Molecular characterisation using multilocus sequence typing (MLST) plus spa-typing showed that sequence type ST398/t899 and ST398/t011 were the most commonly isolated genotypes, although other relevant sequence types such as ST1 or ST97 were also found. A lack of susceptibility to penicillins, tetracycline and ceftiofur was detected in >91.95, 85.05 and 48.28% of the isolates, respectively. Resistance to doxycycline (32.18%), enrofloxacin (27.59%) and gentamicin (25.29%) was also observed. Additionally, a remarkable level of antibiotic multiresistance (AMR) was observed representing a 77.01% (n = 67) of the obtained isolates. Genetic analysis revealed that 97.70% and 77.01% of the isolates harboured at least one antibiotic resistance or enterotoxin gene, respectively, pointing out a high isolate virulence potential. Lastly, 55.17% (n = 48) were able to produce measurable amounts of biofilm after 24 h. In spite of the current programmes for antibiotic reduction in intensively farming, a still on-going high level of AMR and virulence potential in MRSA was demonstrated, making this pathogen a serious risk in swine production chain, highlighting once more the need to develop efficient, pathogen-specific control strategies.

Local and Transboundary Transmissions of Methicillin-Resistant Staphylococcus aureus Sequence Type 398 through Pig Trading

Livestock-associated methicillin-resistant Staphylococcus aureus sequence type (ST) 398 (LA-MRSA ST398) is a genetic lineage for which pigs are regarded as the main reservoir. An increasing prevalence of LA-MRSA ST398 has been reported in areas with high livestock density throughout Europe. In this study, we investigated the drivers contributing to the introduction and spread of LA-MRSA ST398 through the pig farming system in southern Italy. Whole-genome sequencing (WGS) of LA-MRSA ST398 isolates collected in 2018 from pigs (n = 53) and employees (n = 14) from 10 farms in the Calabria region of Italy were comparatively analyzed with previously published WGS data from Italian ST398 isolates (n = 45), an international ST398 reference collection (n = 89), and isolates from Danish pig farms (n = 283), which are the main suppliers of pigs imported to Italy. Single-nucleotide polymorphisms (SNP) were used to infer isolate relatedness, and these data were used together with data from animal trading to identify factors contributing to LA-MRSA ST398 dissemination. The analyses support the existence of two concurrent pathways for the spread of LA-MRSA ST398 in southern Italy: (i) multiple introductions of LA-MRSA ST398 through the import of colonized pigs from other European countries, including Denmark and France, and (ii) the spread of distinct clones dependent on local trading of pigs between farms. Phylogenetically related Italian and Danish LA-MRSA ST398 isolates shared extensive similarities, including carriage of antimicrobial resistance genes. Our findings highlight the potential risk of transboundary transmission of antimicrobial-resistant bacterial clones with a high zoonotic potential during import of pigs from countries with high LA-MRSA prevalence.IMPORTANCE Over the past decade, livestock-associated methicillin-resistant Staphylococcus aureus sequence type 398 (LA-MRSA ST398) has spread among pig holdings throughout Europe, in parallel with the increased incidence of infections among humans, especially in intensive pig farming regions. Despite the growing prevalence of LA-MRSA ST398 in Italian pig farms, the transmission dynamics of this clone in Italy remains unclear. This work provides genome-based evidence to suggest transboundary LA-MRSA ST398 transmission through trading of colonized pigs between European countries and Italy, as well as between farms in the same Italian region. Our findings show that both international trading and local trading of colonized pigs are important factors contributing to the global spread of LA-MRSA ST398 and underscore the need for control measures on and off the farm to reduce the dissemination of this zoonotic pathogen.

Biofilm Production Ability, Virulence and Antimicrobial Resistance Genes in Staphylococcus aureus from Various Veterinary Hospitals

: Staphylococcus aureus (S. aureus) is one of the most clinically important zoonotic pathogens, but an understanding of the prevalence, biofilm formulation ability, virulence, and antimicrobial resistance genes of S. aureus from veterinary hospitals is lacking. By characterizing S. aureus in different origins of veterinary hospitals in Guangzhou, China, in 2019, we identified with the presence of S. aureus in pets (17.1%), veterinarians (31.7%), airborne dust (19.1%), environmental surfaces (4.3%), and medical device surfaces (10.8%). Multilocus sequence typing (MLST) and Staphylococcus protein A (spa) typing analyses demonstrated methicillin-sensitive S. aureus (MSSA) ST398-t571, MSSA ST188-t189, and methicillin-resistant S. aureus (MRSA) ST59-t437 were the most prevalent lineage. S. aureus with similar pulsed-field gel electrophoresis (PFGE) types distributed widely in different kinds of samples. The crystal violet straining assays revealed 100% (3/3) of MRSA ST59 and 81.8% (9/11) of MSSA ST188 showed strong biofilm formulation ability, whereas other STs (ST1, ST5, ST7, ST15, ST88, ST398, ST3154 and ST5353) showed weak biofilm production ability. Polymerase chain reaction (PCR) confirmed the most prevalent leucocidin, staphylococcal enterotoxins, ica operon, and adhesion genes were lukD-lukE (49.0%), sec-sel (15.7%), icaA-icaB-icaC-icaR (100.0%), and fnbB-cidA-fib-ebps-eno (100.0%), respectively. Our study showed that the isolates with strong biofilm production ability had a higher prevalence in clfA, clfB, fnbA and sdrC genes compared to the isolates with weak biofilm production ability. Furthermore, 2 ST1-MRSA isolates with tst gene and 1 ST88-MSSA isolate with lukS/F-PV gene were detected. In conclusion, the clonal dissemination of S. aureus of different origins in veterinary hospitals may have occurred; the biofilm production capacity of S. aureus is strongly correlated with ST types; some adhesion genes such as clfA, clfB, fnbA, and sdrC may pose an influence on biofilm production ability and the emergence of lukS/F-PV and tst genes in S. aureus from veterinary hospitals should raise our vigilance.

Prevalence and antibiotic resistance profiles of Staphylococcus sp. isolated from food, food contact surfaces and food handlers in a Moroccan hospital kitchen

Food poisoning risk related to the consumption of contaminated food with known foodborne pathogens or antibiotic-resistant bacteria is currently a serious threat for public health. Thus, pathogenic methicillin-resistant Staphylococcus strains are considered as one of the major cause of foodborne diseases in hospitals. The present study aims to determine the prevalence and the antibiotic resistance patterns of Staphylococcus in various types of hospital food samples, work surfaces and its carriage by food handlers. A total of 608 collected samples including 300 food samples, 238 food contact surfaces and 70 nasal and hand samples were tested. The identified Staphylococcus and their antibiotic resistance patterns were analysed using the agar disk-diffusion and PCR method was used for mecA resistance gene amplification. The prevalence of S. aureus and the coagulase-negative staphylococci were 17·33 and 23·33%, respectively. The antibiotic resistance reached 100% towards oxacillin and Penicillin G for both S. aureus and CoNs. The mecA gene was detected in 5·71% (4/70) and 7·69% (4/52) of S. aureus and CoNs strains, respectively. The outcome of this study enlightens isolation of MRSA strains and resistant CoNs from food, food contact surfaces and food handlers. The presence of this resistant species in this critical setting, where products were intended to vulnerable and immunocompromised patients, represents a serious threat to this community. It can be a source of nosocomial infection and more precautions must be taken to prevent staphylococci food contamination mainly in hospitals. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study describing the antibiotic resistance patterns of Staphylococcus aureus and coagulase-negative Staphylococcus isolated from hospital food, food contact surfaces and food handlers samples in a Moroccan hospital kitchen. High levels of multi-resistance were reported. The alarming outcome of this study emphasizes the crucial need of implementing an approach to fight multidrug-resistant staphylococci mainly in healthcare settings, where the community have already compromised health issues.

Recent Research on Occupational Animal Exposures and Health Risks: A Narrative Review

PURPOSE OF REVIEW

In the last year, an increasing number of studies have reported on methicillin-resistant Staphylococcus aureus (MRSA) transmission in Africa and Asia and in migrant workers. We reviewed original research on occupational health and safety of animal workers published from January 1, 2018, through June 30, 2019, with a targeted focus on infectious disease studies published in these populations.

RECENT FINDINGS

Studies focused on occupational exposures to infectious agents, dust and allergens, pesticides, and occupational injury. Research on zoonotic MRSA used whole genome-sequencing technologies to evaluate transmission in Africa and Asia. Swine worker exposure to porcine coronavirus and emerging influenza A viruses was documented in China. 16s RNA amplicon sequencing identified distinct microbiota compositions in households with active animal farmers. Multiple bioaerosol exposures were assessed for industrial dairy workers. Occupational injury studies highlighted the struggles of Latino animal workers in the USA. These studies highlighted the global expansion of zoonotic antibiotic resistance and identified novel occupational zoonoses of concern. The integration of microbiome assessment and compound mixtures into the evaluation of dust and endotoxin exposures for animal workers marks a new direction for this work.

Comparison of Antibiotic Resistance Profile and Biofilm Production of Staphylococcus aureus Isolates Derived from Human Specimens and Animal-Derived Samples

Background: The diffusion of antimicrobial resistance is a significant concern for public health worldwide. Staphylococcus aureus represents a paradigm microorganism for antibiotic resistance in that resistant strains appear within a decade after the introduction of new antibiotics. Methods: Fourteen S. aureus isolates from human specimens and twenty-one from samples of animal origin, were compared for their antimicrobial resistance and biofilm capability. In addition, they were characterized at the molecular level to detect the antimicrobial resistance mecA gene and genes related with enterotoxin, toxin, and biofilm production. Results: Both phenotypic and molecular analysis showed main differences among human- and animal-derived isolates. Among the human-derived isolates, more multidrug-resistant isolates were detected and mecA gene, enterotoxin, and toxin genes were more prevalent. Different genes involved in biofilm production were detected with bap present only in animal-derived isolates and sasC present in both isolates, however, with a higher prevalence in the human-derived isolates. Biofilm capability was higher in human-derived isolates mainly associated to the sasC gene. Conclusions: The overall results indicate that human S. aureus isolates are more virulent and resistant than the isolates of animal origin randomly selected with no infection anamnesis. This study confirms that selection for more virulent and resistant S. aureus strains is related to the clinical practice.