Presence of Methicillin-resistant Staphylococcus Aureus in Slaughterhouse Environment, Pigs, Carcasses, and Workers

An emerging zoonosis: molecular detection of multidrug-methicillin resistant Staphylococcus aureus from butchers' knives, livestock products and contact surfaces

Methicillin-resistant Staphylococcus aureus (MRSA) transmission in livestock, community, and healthcare settings poses a significant public health concern both locally and globally. This study aimed to investigate the occurrence, molecular detection, and antibiogram of the MRSA strain in fresh beef, contact surfaces, and butchers' knives from the four major abattoirs (Karu, Gwagwalada, Deidei, and Kubwa) located in the Federal Capital Territory, Nigeria. A multi-stage sampling technique was used to collect 400 swab samples from butchers' knives (132), fresh beef (136), and contact surfaces (132). Presumptive colonies on mannitol salt agar were subjected to culture, isolation, and biotyping. The antibiogram was carried out via a Kirby-Bauer disk containing eight antibiotics. MRSA was phenotypically confirmed by oxacillin-resistant screening agar base (ORSAB) and genotypically by PCR to detect the presence of the mecA gene. Out of the 400 samples, 47.24% of fresh beef, 37% of contact surfaces, and 64.33% of butchers' knife swabs were Staphylococcus aureus positive. Thirty-two Staphylococcus aureus-positive isolates were confirmed to be MRSA, 50% fresh beef, 28.12% contact surfaces, and 21.87% butcher's knife swabs. MRSA isolates displayed multidrug-resistant traits, with a high resistance of 90.62% against cloxacillin, and a highest susceptibility of 100% to co-trimaxole. The antibiogram showed MRSA strains to be multidrug resistant. Molecular characterisation of the MRSA detected the presence of the mecA gene at a band size of 163 bp in all isolates. Strict hygiene of butchers, and working equipment in meat processing and marketing should be of top priority.

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 and Virulence Determinants of Staphylococcus aureus in Wholesale and Retail Pork in Wuhan, Central China

Staphylococcus aureus is one of the major foodborne pathogens and can cause serious foodborne illness in humans by foods contaminated with S. aureus enterotoxins. In recent years, livestock-associated S. aureus has been a major public health concern for humans and has emerged in various countries globally. China is one of the largest producers of pigs and pork in the world. However, there are few studies on the detailed genotypic and pathogenic characterization of pork-associated S. aureus in China. In this study, the prevalence, antimicrobial resistance, and genotypic characteristics of S. aureus in raw pork in Wuhan, China, were investigated through multilocus sequence typing (MLST), staphylococcal protein A gene (spa) typing, and whole-genome sequencing analysis. A total of 518 S. aureus isolates (16.9%) were isolated from 3067 retail and wholesale pork samples. The prevalence of S. aureus in retail pork (22.7%) was significantly higher than in wholesale pork (15.1%), while the proportion of multidrug-resistant (MDR) isolates in wholesale pork (12.9%) was significantly higher than in retail pork (6.2%). Among the isolates, 10.8% were resistant to three or more antibiotics, with higher rates of resistance to penicillin (88.8%) and erythromycin (58.1%). A total of 28 sequence types (STs) were identified in the 518 isolates, and the predominant type was ST7 (57.5%), followed by ST5 (9.1%). In addition, based on the whole-genome sequences of 39 representative strains, 17 spa types were identified among the isolates, of which t899, t091, and t437 were the most common. Furthermore, 19 staphylococcal enterotoxin (SE) and SE-like (SEl) toxin genes were detected in the isolates, of which selw was the most common type (100%), followed by sei, sem, seo, seu, and selv (46.2%); sey (35.9%); and sea, seg, and sen (33.3%). This study found for the first time that ST7-t091-selw and ST9-t899-SCCmecXII-selw were the predominant genotypes of S. aureus in pork in China, which indicated the spreading of S. aureus with multiple virulence factors, especially with new SE/SEl types in pigs and pork, is a serious new challenge for food safety. Good hygiene and good production practices to prevent interspecies transmission and cross-contamination of S. aureus in the pig-pork chain are of great significance to public health.

ZnO@Polyvinyl Alcohol/Poly(lactic acid) Nanocomposite Films for the Extended Shelf Life of Pork by Efficient Antibacterial Adhesion

The proliferation of microorganisms is an important reason for meat spoilage and deterioration. Freezing and packaging by polymer films and preservatives are commonly used to preserve meat. While the energy consumption of freezing is very big, the polymer films made by petroleum bring up heavy environmental pressure. In the present study, biodegradable antibacterial ZnO@PLA (ZP) and ZnO@PVA/PLA (ZPP) nanocomposite films used as food packaging have been synthesized by the solvent evaporation method and coating method, respectively. Compared with films without ZnO NPs, ZP and ZPP both had long-term bacteriostasis for 24 and 120 h at temperatures of 25 and 4 °C, respectively. Moreover, the antibacterial effect showed positive relevance with the increase of the ZnO NP concentration. In addition, the antibacterial effect of ZPP was better than that of ZP in the same condition. Scanning electron microscopy showed that the numbers of methicillin-resistant staphylococcus aureus (MRSA) on ZP and ZPP were significantly reduced compared to that in the blank film, and ZPP caused the morphology of MRSA to change, which means that the antibacterial mechanism of ZP and ZPP composite films might be related to antibacterial adhesion. In conclusion, ZPP films have great potential to be regarded as the candidate of food packing to extend the shelf life of pork.

Multi-Drug Resistant Staphylococcus aureus Carriage in Abattoir Workers in Busia, Kenya

Abattoir workers have been identified as high-risk for livestock-associated Staphylococcus aureus carriage. This study investigated S. aureus carriage in abattoir workers in Western Kenya. Nasal swabs were collected once from participants between February-November 2012. S. aureus was isolated using bacterial culture and antibiotic susceptibility testing performed using the VITEK 2 instrument and disc diffusion methods. Isolates underwent whole genome sequencing and Multi Locus Sequence Types were derived from these data. S. aureus (n = 126) was isolated from 118/737 (16.0%) participants. Carriage was higher in HIV-positive (24/89, 27.0%) than HIV−negative participants (94/648, 14.5%; p = 0.003). There were 23 sequence types (STs) identified, and half of the isolates were ST152 (34.1%) or ST8 (15.1%). Many isolates carried the Panton-Valentine leucocidin toxin gene (42.9%). Only three isolates were methicillin resistant S. aureus (MRSA) (3/126, 2.4%) and the prevalence of MRSA carriage was 0.4% (3/737). All MRSA were ST88. Isolates from HIV-positive participants (37.0%) were more frequently resistant to sulfamethoxazole/trimethoprim compared to isolates from HIV-negative participants (6.1%; p < 0.001). Similarly, trimethoprim resistance genes were more frequently detected in isolates from HIV-positive (81.5%) compared to HIV-negative participants (60.6%; p = 0.044). S. aureus in abattoir workers were representative of major sequence types in Africa, with a high proportion being toxigenic isolates. HIV-positive individuals were more frequently colonized by antimicrobial resistant S. aureus which may be explained by prophylactic antimicrobial use.

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.

Multidrug-Resistant Bacteria and Enterobacteriaceae Count in Abattoir Wastes and Its Receiving Waters in Limbe Municipality, Cameroon: Public Health Implications

The release of untreated wastes from abattoirs into the environment and nearby water bodies poses a significant threat to public health. Such litters may contain pathogens, including antibiotic-resistant bacteria. This study investigated 80 samples collected from butchering tables, slaughter slabs, meat rinsing points, and abattoir wastes receiving water from two abattoirs (A and B). Total Enterobacteriaceae count (TEC) for each sample was determined, and Escherichia coli (E. coli), Salmonella spp., Shigella spp., and Staphylococcus aureus (S. aureus) were isolated and identified. Antimicrobial susceptibility testing was done on all bacterial isolates against nine locally used antibiotics. Overall, 118 bacterial isolates, comprising E. coli (42.5%), Salmonella spp. (27.5%), Shigella spp. (37.5%), and S. aureus (40.0%), were recovered. Of the 118 bacterial isolates, 104 (88.1%) were multidrug-resistant, including 58 (55.8%) from abattoir A and 46 (44.2%) from abattoir B; however, this difference was not statistically significant (p = 0.6837). Of the 32 S. aureus isolates, 29 (90.6%) were multidrug-resistant. All S. aureus were 100% sensitive to vancomycin, kanamycin, and amikacin. Similarly, 31 (91.2%) of the 34 E. coli isolates recovered in this study were multidrug-resistant. Salmonella spp. and Shigella spp. also showed high levels of multidrug resistance corresponding to 81.8% and 86.7%, respectively. All isolates of E. coli, Salmonella, and Shigella were 100% resistant to ampicillin and 100% sensitive to ciprofloxacin. Minimum and maximum mean values for TEC were 3.62-5.83 log CFU/mL for abattoir A and 4.08–5.56 log CFU/mL for abattoir B. The highest and lowest TEC counts were from slaughter slab and upstream water, respectively, in each abattoir. Our results indicate a predominance of multidrug-resistant bacteria in abattoir wastes and their receiving waters in the study sites. Hence, we recommend the treatment of abattoir wastes before disposal and improved hygiene and sanitation practices to enhance public health.

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.

Livestock-associated methicillin-resistant Staphylococcus aureus in slaughtered pigs in England

This study was performed to investigate the occurrence of livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) in batches of pigs at slaughter and at different stages along the slaughter line. Nasal and ear skin swabs were collected from 105 batches of 10 pigs at six abattoirs. Cultures (pooled or individual) were performed for MRSA using selective media; presumptive MRSA were confirmed by mecA and nuc gene detection and a selection was spa-typed. MRSA was detected in 46 batches. All spa-types detected were those associated with LA-MRSA clonal complex 398. The proportion of positive batches varied among abattoirs (0–100%). Two abattoirs were subsequently further investigated, with samples taken at post-stunning, chiller and either at lairage or post-singe. Results suggested cross-contamination occurred between the lairage and point of post-stunning, but the slaughter processes appeared effective at reducing contamination before carcases entered the chiller. One abattoir provided only negative samples in the initial study and in the subsequent study along the slaughter line (26 batches in total), suggesting differences possibly in the MRSA status of pigs on arrival from supply farms or in its abattoir practices affecting the MRSA status of pigs at the sampling points. This study highlights that in the investigated abattoirs, MRSA was detected in 43.8% of batches of pigs at slaughter using sensitive selective culture methods.

Methicillin-Resistant Staphylococcus aureus (MRSA) in Slaughter Houses and Meat Shops in Capital Territory of Pakistan During 2018–2019

Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) is a major concern in many parts of the world, including Pakistan. The aim of this study was to investigate the prevalence of MRSA in slaughterhouses and meat shops in Rawalpindi-Islamabad, Pakistan, 2018–2019. A total of 300 samples were collected: 40 from each of working area, tools (knives, hooks), butcher hands and beef, 30 from each of chicken and mutton, 20 from each of nasal and rectal swabs. S. aureus was phenotypically identified by performing gram staining and biochemical tests. 150 of the 300 samples were confirmed to be S. aureus by phenotypic identification. MRSA was identified among S. aureus positive isolates by performing disk diffusion test and by detecting S. aureus-specific genes such as 16s rRNA, nuc, mecA, spa, and coa. Out of 150 isolates 96 (63%) showed resistance to antibiotic cefoxitin, known as a potential marker for detecting MRSA. While all 150 isolates have shown complete resistance to the four antibiotics neomycin, methicillin, ciprofloxacin and tetracycline. The nuc and 16s rRNA genes were detected in all 150 S. aureus-positive isolates and 118 (79%) were confirmed to be MRSA through the detection of the mecA gene. MRSA prevalence was highest in chicken (23/30, 77%) followed by beef (25/40, 63%), mutton (15/30, 50%), knives (18/40, 45%), nasal swabs (7/20, 35%), working area (11/40, 28%), rectal swabs (5/20, 25%), hooks (7/40, 18%), and butcher hands (7/40, 18%). 50 MRSA-positive isolates were chosen to identify two virulence factors (spa and coa gene). Of the 50 MRSA isolates subject to coa and spa gene typing, 27 (54%) were positive for the coa gene and 18 (36%) were positive for the spa gene, respectively. To the best of our knowledge, this was the first study on the molecular identification of MRSA in meat samples from Pakistan. High prevalence of MRSA in meat samples demand for implementation of proper hygienic practices and procedures during the slaughtering, transport and marketing of meat and meat products in order to prevent the spread of these bacteria to the human population.

Antibiotic-resistant bacteria and antimicrobial residues in wastewater and process water from German pig slaughterhouses and their receiving municipal wastewater treatment plants

Slaughterhouse process- and wastewater are considered as a hotspot for antibiotic-resistant bacteria and antimicrobial residues and may thus play an important role for their dissemination into the environment. In this study, we investigated occurrence and characteristics of ESKAPE bacteria (E. faecium, S. aureus, K. pneumoniae, A. baumannii, P. aeruginosa, Enterobacter spp.) and ESBL (extended spectrum β-lactamase) -producing E. coli in water samples of different processing stages of two German pig slaughterhouses (S1/S2) as well as their municipal wastewater treatment plants (mWWTPs). Furthermore, residues of various antimicrobials were determined. A total of 103 water samples were taken in delivery and dirty areas of the slaughterhouses S1/S2 (n = 37), their in-house WWTPs (n = 30) and mWWTPs including their receiving water bodies (n = 36). The recovered isolates (n = 886) were characterized for their antimicrobial resistance pattern and its genetic basis. Targeted species were ubiquitous along the slaughtering and wastewater chains. Phenotypic and genotypic analyses revealed a broad variety of resistance phenotypes and β-lactamase genes. Carbapenemase-producing Enterobacteriaceae (CPE), vancomycin-resistant enterococci (VRE) and healthcare-associated (HA) MRSA were recovered only from mWWTPs and their preflooders. In contrast, the mcr-1 gene was exclusively detected in E. coli from S1/S2. Residues of five antimicrobials were detected in 14.9% (10/67) of S1/S2 samples in low range concentrations (≤1.30 μg/L), whereas 91.7% (33/36) of mWWTPs samples exhibited residues of 22 different antibiotics in concentrations of up to 4.20 μg/L. Target bacteria from S1/S2 and mWWTPs exhibited differences in their abundances, resistance phenotypes and genotypes as well as clonal lineages. S1/S2 samples exhibited bacteria with zoonotic potential (e.g. MRSA of CC398, E. coli of significant clones), whereas ESKAPE bacteria exhibiting resistances of clinical importance were mainly detected in mWWTPs. Municipal WWTPs seem to fail to eliminate these bacteria leading to a discharge into the preflooder and a subsequent dissemination into the surface water.

Microarray based genetic profiling of Staphylococcus aureus isolated from abattoir byproducts of pork origin

Many parts of pork meat processing are currently not used for human consumption in Switzerland, although they are of great nutritional value. Therefore, data on the occurrence of pathogenic organisms on byproducts is extremely scarce and the prevalence and population structure of Staphylococcus aureus on meat processing sidestreams is unknown. Hence, abattoir byproducts of pork origin including ear, forefoot, heart, intestine, liver, rib bone, sternum, bladder, stomach, hind foot and tongue originating from six abattoirs were screened for S. aureus. The obtained isolates were investigated by spa typing and DNA microarray analysis to reveal their genomic profile and population structure. The prevalence of S. aureus was generally low with a mean of 8%. In total, 40 S. aureus strains were detected and assigned to 12 spa types (t015, t1491, t1778, t091, t337, t899, t2922, t7439, t1333, t208, t4049, t034) and seven clonal complexes (CC1, CC7, CC9, CC30, CC45, CC49, CC398). Detected enterotoxin genes included sea, seb, sec, seh, sel and egc encoded toxin genes seg, sei, sem, sen, seo, and seu. None of the isolates harbored genes conferring methicillin resistance, but blaZ/I/R genes causing penicillin resistance were frequently found. In addition, strains from CC398 exhibited tetM and tetK, conferring tetracycline resistance. Similarity calculations based on microarray profiles revealed no association of clonal complexes with particular body parts, but revealed a certain correspondence of clonal complex and originating abattoir.

Prevalence, antimicrobial susceptibility and characterization of Staphylococcus aureus and methicillin-resistant Staphylococcus aureus isolated from dairy industries in north-central and north-eastern Greece

Staphylococcus aureus is an important cause of food intoxication, whereas methicillin-resistant S. aureus (MRSA) constitutes a serious public-health concern due to its ability to colonize and infect humans and animals. S. aureus and MRSA have often been isolated from milk and dairy products. The objectives of this study were to estimate the prevalence and the antimicrobial resistance of S. aureus and MRSA in four Greek dairy industries, to identify virulence factors of MRSA isolates and to describe their genetic diversity, in order to identify possible epidemiological links and evaluate the risk of MRSA dissemination to the community. S. aureus was isolated from 67 out of 305 (22.0%) dairy industry samples (bulk-tank milk, dairy products, employee nasal swabs and equipment/surface swabs). Almost all (99%) of the 227 corresponding S. aureus isolates (approximately 4 isolates per positive sample) were resistant to at least one antimicrobial and 22% were multi-drug resistant (MDR). MRSA were isolated from 11 different samples (3.6%) originating from three of the dairy plants. All MRSA isolates were capable of forming biofilms, while staphylococcal enterotoxin (SE) genes were detected in 91% of the MRSA isolates, with sec being the most frequent. All of the MRSA isolates harbored the mecA gene but the mecC and Pandon-Valentine leucocidin (PVL) genes were not detected. Pulse-Field Gel Electrophoresis (PFGE) analysis showed genetic diversity among the MRSA isolates and indicated clonal circulation in one of the dairy plants. Seven spa types were identified among the MRSA isolates with the most prevalent (t065) isolated only in one dairy plant. Certain spa types (t065, t337 and t3536) were isolated for the first time in Greece. The presence of MDR, biofilm-forming and enterotoxigenic MRSA strains in dairy plant facilities may lead to their dissemination to the community, but also to staphylococcal food poisoning, when conditions are favorable. The study's findings highlight the need for continuous monitoring of the dairy production chain, the need for re-evaluating the implemented cleaning and sanitizing processes and the adoption of preventive strategies in order to minimize public-health risks.