Prevalence, molecular epidemiology, and antimicrobial resistance of methicillin-resistant Staphylococcus aureus from swine in southern Italy

Repurposing of non-steroidal anti-inflammatory drugs for combination therapies to combat multidrug-resistant S. aureus of bovine reproductive tract origin

Multidrug-resistant bacteria have become the predominant etiology in bovine female reproductive tract infections and thus require effective treatment approaches. The main goal of this study was the molecular detection of mecA, blaZ, tetK, and aacA-aphD genes in Staphylococcus aureus (S. aureus) responsible for methicillin, beta-lactam, tetracycline, and aminoglycoside resistance respectively. Phylogenetic analysis was conducted to check the homology of staphylococcal genes with NCBI sequences. The in-vitro efficacy of non-steroidal anti-inflammatory drugs (NSAIDs) in combination therapies against MDR S. aureus was evaluated using well diffusion assay and checkerboard method. Vaginal swab samples (n = 384) collected from bovines suffering from endometritis, pyometra, and retained placenta were tested for S. aureus. Results showed a 17.96% overall prevalence. Both phenotypic and genotypic resistance was observed among S. aureus isolates with 50.72% and 37.68% isolates being confirmed as methicillin-resistant (MRSA), 36.23% and 18.84% isolates exhibiting beta-lactam, 40.58%, and 27.54% isolates showing tetracycline, and 33.33% and 36.23% isolates showing aminoglycosides resistance based on disc diffusion and gene confirmation, respectively. Phylogenetic analysis indicated homology with previously reported Pakistani isolates suggesting the possibility of MDR S. aureus transmission within and between animals. Synergy testing indicated that combinations of ceftriaxone-ketoprofen (153.77%), ceftriaxone-meloxicam (149.55%), amoxiclav-flunixin meglumine (106.06%), and oxytetracycline-flunixin meglumine (104.47%) showed synergy on well diffusion assay. Based on the fractional inhibitory concentration index by checkerboard method, oxytetracycline-meloxicam and gentamicin-ketoprofen combinations exhibited synergistic interaction. In conclusion, MDR S. aureus resistance was mitigated in-vitro through the combination of antibiotics (oxytetracycline, gentamicin) with NSAIDs (meloxicam, ketoprofen) that could be used to create therapeutic strategies for bovine reproductive issues.

A look at staphylococci from the one health perspective

Staphylococcus aureus and other staphylococcal species are resident and transient multihost colonizers as well as conditional pathogens. Especially S. aureus represents an excellent model bacterium for the "One Health" concept because of its dynamics at the human-animal interface and versatility with respect to host adaptation. The development of antimicrobial resistance plays another integral part. This overview will focus on studies at the human-animal interface with respect to livestock farming and to companion animals, as well as on staphylococci in wildlife. In this context transmissions of staphylococci and of antimicrobial resistance genes between animals and humans are of particular significance.

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.

Genomic Diversity of Methicillin-Resistant Staphylococcus aureus CC398 Isolates Collected from Diseased Swine in the German National Resistance Monitoring Program GERM-Vet from 2007 to 2019

Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) clonal complex 398 (CC398) isolates (n = 178) collected in the national resistance monitoring program GERM-Vet from diseased swine in Germany from 2007 to 2019 were investigated for their genomic diversity with a focus on virulence and antimicrobial resistance (AMR) traits. Whole-genome sequencing was followed by molecular typing and sequence analysis. A minimum spanning tree based on core-genome multilocus sequence typing was constructed, and antimicrobial susceptibility testing was performed. Most isolates were assigned to nine clusters. They displayed close phylogenetic relationships but a wide molecular variety, including 13 spa types and 19 known and four novel dru types. Several toxin-encoding genes, including eta, seb, sek, sep, and seq, were detected. The isolates harbored a wide range of AMR properties mirroring the proportions of the classes of antimicrobial agents applied in veterinary medicine in Germany. Multiple novel or rare AMR genes were identified, including the phenicol-lincosamide-oxazolidinone-pleuromutilin-streptogramin A resistance gene cfr, the lincosamide-pleuromutilin-streptogramin A resistance gene vga(C), and the novel macrolide-lincosamide-streptogramin B resistance gene erm(54). Many AMR genes were part of small transposons or plasmids. Clonal and geographical correlations of molecular characteristics and resistance and virulence genes were more frequently observed than temporal relations. In conclusion, this study provides insight into population dynamics of the main epidemic porcine LA-MRSA lineage in Germany over a 13-year-period. The observed comprehensive AMR and virulence properties, most likely resulting from the exchange of genetic material between bacteria, highlighted the importance of LA-MRSA surveillance to prevent further dissemination among swine husbandry facilities and entry into the human community. IMPORTANCE The LA-MRSA-CC398 lineage is known for its low host specificity and frequent multiresistance to antimicrobial agents. Colonized swine and their related surroundings represent a considerable risk of LA-MRSA-CC398 colonization or infection for occupationally exposed people through which such isolates might be further disseminated within the human community. This study provides insight into the diversity of the porcine LA-MRSA-CC398 lineage in Germany. Clonal and geographical correlations of molecular characteristics and resistance and virulence traits were detected and may be associated with the spread of specific isolates through livestock trade, human occupational exposure, or dust emission. The demonstrated genetic variability underlines the lineage's ability to horizontally acquire foreign genetic material. Thus, LA-MRSA-CC398 isolates have the potential to become even more dangerous for various host species, including humans, due to increased virulence and/or limited therapeutic options for infection control. Full-scale LA-MRSA monitoring at the farm, community, and hospital level is therefore essential.

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.

A review of new emerging livestock-associated methicillin-resistant Staphylococcus aureus from pig farms

Methicillin-resistant Staphylococcus aureus (MRSA) is a S. aureus strain resistant to β-lactam antibiotics and is often associated with livestock, known as livestock-associated (LA)-MRSA. Using molecular typing with multi-locus sequence typing, MRSA clones have been classified in pigs, including clonal complex 398. Livestock-associated-methicillin-resistant S. aureus was first discovered in pigs in the Netherlands in 2005. Since then, it has been widely detected in pigs in other countries. Livestock-associated-methicillin-resistant S. aureus can be transmitted from pigs to pigs, pigs to humans (zoonosis), and humans to humans. This transmission is enabled by several risk factors involved in the pig trade, including the use of antibiotics and zinc, the size and type of the herd, and the pig pen management system. Although LA-MRSA has little impact on the pigs' health, it can be transmitted from pig to pig or from pig to human. This is a serious concern as people in direct contact with pigs are highly predisposed to acquiring LA-MRSA infection. The measures to control LA-MRSA spread in pig farms include conducting periodic LA-MRSA screening tests on pigs and avoiding certain antibiotics in pigs. This study aimed to review the emerging LA-MRSA strains in pig farms.

Prevalence, antimicrobial resistance, and staphylococcal toxin genes of blaTEM-1a -producing Staphylococcus aureus isolated from animals in Chongqing, China

BACKGROUND

Staphylococcus aureus infection of livestock animals and humans is a major public health issue. There are reports of antimicrobial resistance and multiple staphylococcal superantigen genes in many countries and several provinces of China, but the status in Chongqing, China is uncertain.

OBJECTIVES

The aim of this study was to determine the prevalence, antimicrobial susceptibility, and other molecular characteristics of S. aureus isolates from livestock animals in Chongqing.

METHODS

Staphylococcus aureus was isolated and identified by selective enrichment and amplification of the nuc gene from 1371 samples collected at farms in Chongqing. The agar dilution method was used to determine the resistant phenotype, and extended spectrum β-lactamase genes were amplified by PCR. Methicillin-resistant S. aureus was verified by the presence of the mecA gene, and the presence or absence of SE, SEl, and TSST-1 genes was detected in the isolates.

RESULTS

We cultured 89 S. aureus isolates from 1371 samples between March 2014 and December 2017. These isolates were from pigs, cattle, goats, rabbits, and chickens. There were four methicillin-resistant S. aureus strains (three from pigs and one from a chicken). The 89 isolates had high resistance to penicillin (93.3%) and ampicillin (92.1%), but most were susceptible to amikacin and ofloxacin, with resistance rates below 10%. A total of 62.9% of the isolates had varying degrees of multidrug resistance. Almost all strains, except for three isolates from chickens, were positive for bla_TEM-1a . There were 19 of 20 tested staphylococcal SE/SEl/TSST-1 genes present (all except for seq), and the predominant genes were sei (58.4%), tst-1 (56.2%), and seg (51.7%).

CONCLUSIONS

The high antimicrobial resistance and prevalence of bla_TEM-1a reinforce the need to reduce the usage of antimicrobials in livestock. The universal existence of staphylococcal toxin genes implies a potential threat to public health by animal-to-human transmission via the food chain.

Low-level colonization of methicillin-resistant Staphylococcus aureus in pigs is maintained by slowly evolving, closely related strains in Finnish pig farms

BACKGROUND

Over the past two decades, livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) has become widely prevalent in pig production in Europe. The carriage status of LA-MRSA is known to vary among individual pigs, but bacterial load in pigs has rarely been studied. We assessed the quantity of LA-MRSA in nasal and skin samples of pigs and investigated the genetic diversity of the strains together with sequenced strains from national surveillance and pathology samples from the Finnish Food Authority. On two farms with assumed MRSA-positive status, farm 1 and farm 2, 10 healthy pigs were sampled three times during 2 weeks from the nares and skin (study A). On farm 1, 54 additional pigs were sampled and from confirmed MRSA-positive animals, 10 were randomly selected and transported to a clean, controlled environment for further sampling (study B). From the samples taken on farms 1 and 2 and in the controlled environment, MRSA was isolated both by direct plating and enrichment on selective media. spa types, multilocus sequence types, staphylococcal cassette chromosome mec types, resistance and virulence genes were determined. Core genome multilocus sequence typing (cgMLST) analysis was performed, including the sequences deriving from the surveillance/pathology samples from the Finnish Food Authority.

RESULTS

All pigs on farm 1 carried LA-MRSA in the nares at all three time points and five pigs on farm 2 at one time point. Nasal quantity varied between 10 and 10³ CFU/swab and quantity on the skin between 10 and 10² CFU/swab. In the controlled environment, MRSA was detected in at least one of the nasal samples from each animal. spa type t034 was predominant. cgMLST showed one cluster with minimum allele differences between 0 and 11.

CONCLUSIONS

The study shows predominantly low-level carriage (< 10³ CFU/swab) of LA-MRSA on farms. In the controlled environment we observed a decline in nasal carriage but constant skin carriage. cgMLST showed that strains of spa type t034 are closely related at the national level.

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.

Antimicrobial Resistance and Molecular Characterization of Methicillin-Resistant Staphylococcus aureus from Two Pig Farms: Longitudinal Study of LA-MRSA

Pigs were identified as the most important reservoir of livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA), mostly belonging to the emergent zoonotic clonal complex (CC) 398. Here, we investigated the presence of MRSA in sows and piglets over a period of several months in two pig farms (intensive farm A and family-run farm B). Isolates underwent antimicrobial susceptibility testing, PCR characterization and spa typing. We collected 280 samples, namely 206 nasal swabs from pigs and 74 environmental samples from pig housings at 12 consecutive time points. A total of 120/161 (74.5%) and 75/119 (63.0%) samples were MRSA-positive in farms A and B, respectively. All isolates harbored mecA but lacked mecC and PVL-encoding genes. The identified spa types (t571, t034, t1250 and t898 in farm A, t1451 and t011 in farm B) were indicative of CC398. Antimicrobial resistance patterns (all multidrug resistant in farm A, 57.2% in farm B) depended on the farm, suggesting the impact of farm size and management practices on the prevalence and characteristics of MRSA. Due to the intermittent colonization of pigs and the high contamination of their immediate environment, MRSA status should be determined at the farm level when considering preventive measures or animal trade between farms.

Occurrence of antimicrobial resistance and antimicrobial resistance genes in methicillin-resistant Staphylococcus aureus isolated from healthy rabbits

Background and Aim

Methicillin-resistant globally, Staphylococcus aureus (MRSA) is a major cause of disease in both humans and animals. Several studies have documented the presence of MRSA in healthy and infected animals. However, there is less information on MRSA occurrence in exotic pets, especially healthy rabbits. This study aimed to look into the antimicrobial resistance profile, hidden antimicrobial-resistant genes in isolated bacteria, and to estimate prevalence of MRSA in healthy rabbits.

Materials and Methods

Two-hundreds and eighteen samples, including 42 eyes, 44 ears, 44 oral, 44 ventral thoracic, and 44 perineal swabs, were taken from 44 healthy rabbits that visited the Prasu-Arthorn Animal Hospital, in Nakornpathom, Thailand, from January 2015 to March 2016. The traditional methods of Gram stain, mannitol fermentation, hemolysis on blood agar, catalase test, and coagulase production were used to confirm the presence of Staphylococcus aureus in all specimens. All bacterial isolates were determined by antimicrobial susceptibility test by the disk diffusion method. The polymerase chain reaction was used to identify the antimicrobial-resistant genes (blaZ, mecA, aacA-aphD, msrA, tetK, gyrA, grlA, and dfrG) in isolates of MRSA with a cefoxitin-resistant phenotype.

Results

From 218 specimens, 185 S. aureus were isolated, with the majority of these being found in the oral cavity (29.73%) and ventral thoracic area (22.7%), respectively. Forty-seven (25.41%) MRSAs were found in S. aureus isolates, with the majority of these being found in the perineum (16, 34.04%) and ventral thoracic area (13, 27.66%) specimens. Among MRSAs, 29 (61.7%) isolates were multidrug-resistant (MDR) strains. Most of MRSA isolates were resistant to penicillin (100%), followed by ceftriaxone (44.68%) and azithromycin (44.68%). In addition, these bacteria contained the most drug-resistance genes, blaZ (47.83%), followed by gyrA (36.17%) and tetK (23.4%).

Conclusion

This study revealed that MRSA could be found even in healthy rabbits. Some MRSAs strains were MDR-MRSA, which means that when an infection occurs, the available antibiotics were not effective in treating it. To prevent the spread of MDR-MRSA from pets to owners, it may be helpful to educate owners about effective prevention and hygiene measures.

Prevalence of LA-MRSA in pigsties: analysis of factors influencing the (De)colonization process

Professional pig husbandry is often associated with a more or less high load of LA-MRSA. Possible risk factors for LA-MRSA colonization in pig herds have already been identified in studies suggesting that housing conditions may affect LA-MRSA prevalence. In Europe, pigs are kept under variety of conditions. The aim of this study is to identify husbandry and housing condition factors that affect colonization with LA-MRSA. 78 pig farms were selected and assigned to three categories according to housing conditions: conventional, alternative and organic. Animal and surface samples were taken and examined for the presence of LA-MRSA at beginning and end of one fattening period per farm. Altogether, a significant (p < 0.05) decrease in colonization with LA-MRSA from beginning to end of the fattening periods in pigs and surfaces can be observed. Alternative farms showed a higher dynamic in the colonization. In organic farms, almost no colonization was found. Influencing housing condition factors that determine LA-MRSA status at the end of the fattening period are the number of pigs in the building, LA-MRSA status at the beginning of fattening period, material of the floor (straw bedding), strictness of black-white separation and antibiotic treatment during the fattening period. For pig farming in general, knowledge and measures to reduce the colonization with LA-MRSA would be important.

Methicillin Resistant Staphylococci Isolated from Goats and Their Farm Environments in Saudi Arabia Genotypically Linked to Known Human Clinical Isolates: a Pilot Study

We conducted a pilot whole genome sequencing (WGS) study to characterize the genotypes of nine methicillin resistant staphylococci (MRS) isolates recovered from goats and their farm environments in Eastern Province, Saudi Arabia, between November 2019 to August 2020. Seven out of nine isolates were methicillin resistant Staphylococcus aureus (MRSA), and two were methicillin resistant Staphylococcus epidermidis (MRSE). All MRSA isolates possessed genotypes previously identified to infect humans, including isolates harboring ST6-SCCmec IV-t304 (n = 4), ST5-SCCmec VI- t688 (n = 2) and ST5-SCCmec V-t311 (n = 1). 2 MRSA isolates possessed plasmids that were genetically similar to those identified in S. aureus isolates recovered from humans and poultry. In contrast, plasmids found in three MRSA isolates and one MRSE isolate were genetically similar to those recovered from humans. All MRSA isolates harbored the host innate modulate genes sak and scn previously associated with human infections. The genotypes of MRSE isolates were determined as ST35, a well-known zoonotic sequence type and ST153, which has been associated with humans. However, the MRSE isolates were untypeable due to extra ccr complexes identified in their SCCmec elements. Moreover, we identified in ST153 isolate SCCmec element also harbored the Arginine Catabolic Mobile Element (ACME) IV. All MRS isolates were phenotypically resistant to trimethoprim-sulfamethoxazole, an antibiotic for the decolonization of MRS. Three isolates carried antibiotic resistance genes in their SCCmec elements that were not previously described, including those encoding fusidic acid resistance (fusC) and trimethoprim resistance (dfrC) incorporated in the MRSA SCCmec VI. IMPORTANCE Our findings demonstrate a possible cross-transmission of methicillin resistant staphylococci between goats and their local environments and between goats and humans. Due to ever increasing resistance to multiple antibiotics, the burden of MRS has a significant impact on livestock farming, public health, and the economy worldwide. This study highlights that implementing a holistic approach to whole genome sequencing surveillance in livestock and farm environments would aid our understanding of the transmission of methicillin resistant staphylococci and, most importantly, allow us to implement appropriate infection control and hygiene practices.

Occurrence and Characteristics of Staphylococcus aureus Isolated from Dairy Products

Food, particularly milk and cheese, may be a reservoir of multi-drug resistant Staphylococcus aureus strains, which can be considered an important issue in terms of food safety. Furthermore, foods of animal origin can be a cause of staphylococcal food poisoning via the production of heat-stable enterotoxins (SE). For this reason, we investigated the prevalence of and characterized Staphylococcus aureus strains isolated from milk and fresh soft cheese obtained from farms located in Wielkopolskie and Zachodniopomorskie Provinces in Poland. Overall, 92% of S. aureus isolates were positive for at least one of the 18 enterotoxin genes identified, and 26% of the strains harbored 5 to 8 enterotoxin genes. Moreover, the S. aureus strains contained genes conferring resistance to antibiotics that are critically important in both human and veterinary medicine, i.e., β-lactams (mecA), aminoglycosides (aac(6′)/aph(2″), aph(3′)-IIIa, ant(4′)-Ia) and MLS_B (erm(A), msr(A), lun(A)). The antimicrobial susceptibility of S. aureus to 16 antibiotics representing 11 different categories showed that 74% of the strains were resistant to at least 1 antibiotic. Moreover, 28% of the strains showed multidrug resistance; in particular, two methicillin-resistant S. aureus strains (MRSA) exhibited significant antibiotic resistance. In summary, our results show that dairy products are contaminated by S. aureus strains carrying genes encoding a variety of enterotoxins as well genes conferring resistance to antibiotics. Both MRSA strains and MSSA isolates showing multidrug resistance were present in foods of animal origin.

First isolation of ST398 methicillin-resistant Staphylococcus aureus carrying staphylococcal cassette chromosome mec type IVd from pig ears in Japan

The emergence and increasing prevalence of livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) are a global concern. To investigate the prevalence and characteristics of sequence type 398 (ST398) MRSA in pig ears, 102 pig's ears were collected from 102 animals shipped from 51 farms at an abattoir. Eight ST398 MRSA isolates were isolated from the ears of eight pigs shipped from seven farms. Of the eight ST398 isolates, seven had the staphylococcal cassette chromosome mec (SCCmec) type IVd and these were obtained from seven pigs shipped from six farms. Single nucleotide polymorphisms ranging from 13 to 26 were observed in the core-genome regions in the seven SCCmec type IVd isolates. We believe that this is the first report on the isolation of ST398 MRSA SCCmec type IVd in Japan.

Prevalence of Livestock-Associated MRSA ST398 in a Swine Slaughterhouse in Guangzhou, China

Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) is an important zoonotic microorganism that is increasingly causing public health concern worldwide. The objective of this study was to determine the transmission and occurrence of MRSA in a slaughterhouse environment and evaluate its antimicrobial resistance and genetic characterization. In this study, we conducted a comprehensive epidemiological survey of S. aureus by spa typing and whole-genome sequencing (WGS) of samples obtained from the pork production chain, the environment, and community residents. To clarify the evolutionary relationships of MRSA sequence type (ST) 398 in this study and global isolates, 197 published whole-genome sequences data of MRSA ST398 strains were downloaded from the GenBank database and included in the phylogenetic analysis. A total of 585 porcine samples (snout and carcass swabs), 78 human nasal samples, and 136 environmental samples were collected. The MRSA isolates were detected at higher frequencies in samples from swine (15.0%) than carcasses (10.0%), slaughterhouse workers (8.0%), community residents (0%), and environment samples (5.9%). The spa typing results showed that t571 accounted for a higher proportion than other spa types. Closely related isolates from the samples of swine, slaughterhouse workers, carcasses, carrier vehicle, and surrounding fishpond water indicate that MRSA ST398 strains may spread among swine, humans, and the environment. MRSA ST398-t571 isolates were genetically different from global strains, except for two Korean isolates, which showed genetic closeness with it. In addition, a MRSA ST398 isolate recovered from an infected patient in Europe differed by only 31 SNPs from the airborne dust-associated strain isolated in this study, thereby suggesting potential transmission among different countries. Antimicrobial susceptibility testing results demonstrated that 99.0% (96/97) of MRSA and 95.1% (231/243) of methicillin-sensitive S. aureus (MSSA) showed multidrug-resistant (MDR) phenotypes. According to WGS analysis, the poxtA-carrying segment (IS431mec-optrA-IS1216-fexB-IS431mec) was reported in MRSA ST398 isolates for the first time. The coexistence of cfr and optrA in a plasmid was first detected in MRSA ST398. The potential transmission of MRSA among humans, animals, and the environment is a cause for concern. The emergence and transmission of LA-MRSA ST398 with high levels of resistance profiles highlight the urgent need for LA-MRSA surveillance.

Prevalence and Characterisation of Multiresistant Bacterial Strains Isolated in Pigs from the Island of Tenerife

Background: Antibiotic-resistant bacteria can circulate among human and animal populations through direct contact with animals, as well as via food and the environment. The purpose of this study was to examine the prevalence and characterisation of multiresistant bacteria in pig samples. Methods: 224 samples of pig livestock were taken at the slaughterhouse on the island of Tenerife. A nasal and a rectal sample were collected from each pig. The presence of methicillin-resistant Staphylococcus aureus (MRSA), methicillin-resistant Staphylococcus coagulase-negative (MRCoNS), vancomycin-resistant Enterococcus (VRE), extended-spectrum ß-lactamase-producing Enterobacteriaceae (BLEE), carbapenemase-producing Enterobacteriaceae (CPE), and colistin-resistant Enterobacteriaceae was investigated. The resistance genes of the isolated bacteria were characterised by specific PCRs depending on the microorganism to be studied, and in vitro antimicrobial resistance was determined using the broth microdilution method (Vitek^®2 system bioMérieux^®, Nurtingen, Germany). Results: MRSA prevalence was 73.21% (164 isolates). MRCoNS prevalence was 9.8% (22 isolates), S. sciuri being the prevalent species. Six isolates presented a 2.7% prevalence of extended-spectrum ß-lactamase-producing Escherichia coli (BLEE) in the CTX-M-1 group. No vancomycin-resistant Enterococcus (VRE), carbapenemase-producing Enterobacteriaceae (CRE), or colistin-resistant Enterobacteriaceae were isolated. Conclusion: we found a high presence of multiresistant bacteria, suggesting the need for increased control and surveillance of this type of strains in pig livestock and a better understanding of the possible transmission routes of these microorganisms through livestock products.

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

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.

Molecular Epidemiology of Methicillin-Resistant Staphylococcus aureus in Hospitalized Patients in Eastern Heilongjiang Province, China

Background

Recently, owing to antibiotic resistance, the incidence of methicillin-resistant Staphylococcus aureus (MRSA) colonization among intensive care unit (ICU) patients has increased rapidly. So far, there are few studies on active screening of MRSA. The purpose of the current study was to verify the effectiveness of active screening and analyze the molecular epidemiological characteristics of MRSA in the region.

Methods

We collected 30 samples of the MRSA strains from a tertiary hospital in the Eastern Heilongjiang Province. Among them, 7 were retrieved through nasal vestibular swabs at the emergency ICU and 23 were obtained from clinical specimens. Additionally, relevant patient medical information was examined retrospectively and molecular epidemiology and risk factor analysis for MRSA were performed.

Results

Molecular epidemiology studies revealed that all strains of bacteria carried the mecA resistance gene. The Panton Valentine leukocidin (PVL), for instance, was detected at a rate of 13.33% (4/30). The Staphylococcus aureus protein A (spa) types, found amongst our samples, were mainly t324, t437, t034, etc., and we discovered a new spa type t19702. We also revealed 3 types of SCCmec, namely, SCCmec type II, SCCmec type IVa, and SCCmec type V, with the most prevalent clonotypes being ST72 and ST59. In addition, we also found 7 new ST types, namely, ST6567, ST6568, ST6569, ST6570, ST6571, ST6572, and ST6573. Using risk factor analysis, we also demonstrated that long, invasive procedures used in the ICU, such as tracheal intubation and ventilator usage, along with patients with cerebral infarction and other embolism are more susceptible to developing MRSA colonization and further infections.

Conclusion

We recommend the infection control department within hospitals to actively screen for MRSA and perform risk factor analysis in order to establish accurate preventive measures for controlling MRSA spread.

Staphylococcus aureus in Agriculture: Lessons in Evolution from a Multispecies Pathogen

Staphylococcus aureus is a formidable bacterial pathogen that is responsible for infections in humans and various species of wild, companion, and agricultural animals. The ability of S. aureus to move between humans and livestock is due to specific characteristics of this bacterium as well as modern agricultural practices. Pathoadaptive clonal lineages of S. aureus have emerged and caused significant economic losses in the agricultural sector. While humans appear to be a primary reservoir for S. aureus, the continued expansion of the livestock industry, globalization, and ubiquitous use of antibiotics has increased the dissemination of pathoadaptive S. aureus in this environment. This review comprehensively summarizes the available literature on the epidemiology, pathophysiology, genomics, antibiotic resistance (ABR), and clinical manifestations of S. aureus infections in domesticated livestock. The availability of S. aureus whole-genome sequence data has provided insight into the mechanisms of host adaptation and host specificity. Several lineages of S. aureus are specifically adapted to a narrow host range on a short evolutionary time scale. However, on a longer evolutionary time scale, host-specific S. aureus has jumped the species barrier between livestock and humans in both directions several times. S. aureus illustrates how close contact between humans and animals in high-density environments can drive evolution. The use of antibiotics in agriculture also drives the emergence of antibiotic-resistant strains, making the possible emergence of human-adapted ABR strains from agricultural practices concerning. Addressing the concerns of ABR S. aureus, without negatively affecting agricultural productivity, is a challenging priority.

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

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

Genomic Insights into Methicillin-Resistant Staphylococcus aureus spa Type t899 Isolates Belonging to Different Sequence Types

This study showed the genetic diversity and population structure of S. aureus presenting the same spa type, t899, but belonging to different STs. Our findings revealed that these isolates vary deeply in their core and accessory genomes, contrary to what is regularly inferred from studies using spa typing only.

Methicillin-resistant Staphylococcus aureus (MRSA) presenting spa type t899 is commonly associated with sequence type 9 (ST9) but is also increasingly linked to ST398. This study provides genomic insight into the diversity of t899 isolates using core genome multilocus sequence typing (cgMLST), single nucleotide polymorphism (SNP)-based phylogeny, and the description of selected antimicrobial resistance and virulence markers. The SNP-based phylogenic tree showed that isolates sharing the same spa type (t899) but different STs highly diverged in their core and accessory genomes, revealing discriminant antimicrobial resistance (AMR) and virulence markers. Our results highlighted the idea that in a surveillance context where only spa typing is used, an additional multiplex PCR for the detection of the tet(M), sak, and seg genes would be valuable in helping distinguish ST9 from ST398 isolates on a routine basis.

IMPORTANCE This study showed the genetic diversity and population structure of S. aureus presenting the same spa type, t899, but belonging to different STs. Our findings revealed that these isolates vary deeply in their core and accessory genomes, contrary to what is regularly inferred from studies using spa typing only. Given that identical spa types can be associated with different STs and that spa typing only is not appropriate for S. aureus isolates that have undergone major recombination events which include the passage of the spa gene (such as in t899-positive MRSA), the combination of both MLST and spa typing methods is recommended. However, spa typing alone is still largely used in surveillance studies and basic characterization. Our data suggest that additional markers, such as tet(M), sak, and seg genes, could be implemented in an easy and inexpensive manner in order to identify S. aureus lineages with a higher accuracy.

Multidrug resistant staphylococci isolated from pigs with exudative epidermitis in North eastern Region of India

Exudative epidermatitis or greasy pig disease (GPD) is a contagious disease of pig and endemic worldwide caused by toxigenic strains under genus Staphylococcus. The present study reported an outbreak of GPD in Champhai district of Mizoram adjoining to the southern border of Myanmar. A total of 60 samples were collected from 22 clinically affected animals and processed for isolation and identification of Staphylococcus spp. All the isolates were subjected to antimicrobial sensitivity assay, biofilm production assay and detection of virulence genes, biofilm genes and mec genes followed by cloning and sequencing for phylogenetic analysis. A total of 44 staphylococci belonged to four species (S. sciuri, S. aureus,S. lentus, and S. hyicus) were isolated. Majority of the isolates were multidrug resistant with maximum resistance against ampicillin, penicillin including vancomycin. None of the S. hyicus isolates was methicillin resistant (MRSH) but 66·67% isolates were MRSA. By PCR, mecA gene was detected in S. aureus (n = 2), S. sciuri (n = 4) and S. lentus (n = 3). Biofilm associated gene icaD was detected in S. aureus (n = 3), S. sciuri (n = 5), S. hyicus (n = 4) and S. lentus (n = 6). The exfoliative toxin genes (ehxB, shetA and tsst1) were detected in S. hyicus (n = 3) and S. aureus (n = 1) isolates. All the isolates were closely related with the isolates from pigs of China, Germany, Japan and USA. The pathogens might be transmitted through illegal migration of pigs from Myanmar to India.

Methicillin-resistant Staphylococcus aureus: epidemiology and antimicrobial susceptibility experiences from the University Hospital 'Luigi Vanvitelli' of Naples

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the important pathogens worldwide showing resistance to several widely used antibiotics. This has made the treatment of MRSA infections harder, especially due to their prevalence in the hospital setting. We evaluated the antibiotic susceptibility patterns of healthcare-associated MRSA infections with a focus on Vancomycin Intermediate S. Aureus (VISA) and macrolide-licosamide-streptogramin B (MLS_B) phenotypes. A total of 417 Staphylococcus aureus (S. aureus) cases were isolated between January 2017 and December 2018, through several clinical specimens collected from the University Hospital 'Luigi Vanvitelli' of Naples. We identified bacterial strains using Matrix-Assisted Laser Desorption/Ionization-Time of Flight (MALDI-TOF) and antimicrobial susceptibility using Phoenix BD (Becton Dickinson, NJ, USA). Out of the total 417 S. aureus cases, 140 were MRSA (33.6%) and of these, 50% were soft tissue infections. All MRSA and Methicillin sensible S.aureus MSSA isolates were susceptible to linezolid and daptomycin. Two MRSA cases exhibited intermediate resistance to vancomycin and were of constitutive MLS_B phenotype. Among the MRSA strains, 11.4% were constitutive and 43.6% were inducible MLS_B phenotypes and 8.6% were macrolide-streptogramin B phenotype. This study characterized the epidemiological status, antibiotic resistance patterns, and current prevalent phenotypes of healthcare-associated MRSA. This knowledge can aid clinicians in improving the antimicrobial stewardship program by adapting appropriate guidelines for the proper use of MRSA antibacterial agents.

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.

Molecular epidemiology of methicillin-resistant Staphylococcus aureus from dairy farms in North-eastern Italy

Transmission of Staphylococcus aureus along the dairy production chain is an emerging public health problem with human, veterinary, and food safety issues. The prevalence of multidrug-resistant, particularly methicillin-resistant S. aureus (MRSA), has steadily increased in several European countries. In this study, the prevalence of S. aureus in raw cow milk and farm workers was investigated, and the trajectories of MRSA transmission at the primary stage of the dairy chain were assessed. To this purpose, a longitudinal survey was conducted in 618 dairy farms in two contiguous regions with high livestock density in North-eastern Italy. S. aureus contamination of bulk tank milk (BTM) was observed in more than 80% of farms, while MRSA prevalence was 3.6% and 15.9% in BTM and farm workers, respectively. The majority of MRSA isolates from both BTM and farm workers were assigned to ST398, and showed a worrisome multidrug-resistant phenotype. Enterotoxin and Panton-Valentine leukocidin genes were detected in 11.5% and 4.9% of MRSA isolates from both sources. Nearly all MRSA isolates from workers belonged to the same epidemiological type as BTM isolates from the corresponding farm, denoting a bidirectional MRSA transmission pattern. A focus on the ST398 spa type t899 MRSA lineage in the Italian livestock system highlighted the presence of two major clusters whose dissemination was likely facilitated by the selective pressure imposed by antimicrobial use in animal farming. Our findings emphasize the need for continuous monitoring of MRSA along the dairy production chain, not only to avoid transmission between animals and exposed workers, but also to contain the risk of raw milk and dairy product contamination by multidrug resistant and toxigenic strain.

Isolation of ST398 methicillin-resistant Staphylococcus aureus from pigs at abattoirs in Tohoku region, Japan

Here, we investigated the presence of ST398 livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) in nasal swabs of 420 slaughtered pigs from 84 farms at three abattoirs in Tohoku, Japan. MRSA were isolated from 13 (3.1%) samples from 9 (10.7%) farms at two abattoirs. All isolates were classified as ST398 and were resistant to ampicillin and tetracycline. Ten and three isolates were classified as Staphylococcal Cassette Chromosome mec (SCCmec) types V and IVa, respectively. All type V isolates possessed czrC. The minimum inhibitory concentrations (MICs) of zinc chloride against types IVa and V were 1 and 4 mM, respectively. This study shows the presence of ST398 MRSA in pigs in this region. Antimicrobials and zinc compounds in feed and drugs might select SCCmec type V ST398 MRSA.

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.

Therapeutic potential of a designed CSαβ peptide ID13 in Staphylococcus aureus-induced endometritis of mice

Staphylococcus aureus is a common pathogen that can cause clinical and subclinical endometritis in humans and animals. In this study, a designed CSαβ peptide ID13 from DLP4 exhibited high stable antibacterial activity in simulated gastric fluid (90.79%), serum (99.54%), and different pH buffers (> 99%) against S. aureus CVCC 546 and lower cytotoxicity (89.62% viability) than its parent peptide DLP4 (74.14% viability) toward mouse endometrial epithelial cells (MEECs). ID13 caused a depolarization of bacterial membrane and downregulation of the expression of genes involved in membrane potential maintenance and biofilm formation. The in vitro efficacy analysis of ID13 showed a synergistic effect with vancomycin, ampicillin, rifampin, and ciprofloxacin; intracellular antimicrobial activity against S. aureus CVCC 546 in MEECs; and the ability to inhibit lipoteichoic acid-induced pro-inflammatory cytokines from RAW 264.7. In the S. aureus-induced endometritis of mice, similar to vancomycin, ID13 remarkably alleviated pathological conditions, inhibited the production of cytokines (TNF-α, IL-1ß, IL-6, and IL-10), and suppressed the TLR2-NF-κB signal pathway. Collectively, these results suggest that ID13 could be a potential candidate peptide for therapeutic application in S. aureus-induced endometritis. Key Points •Higher antibacterial activity and lower hemolysis of ID13 than DLP4. •ID13 could downregulate the genes of bacterial survival and infection. •ID13 could alleviate the S. aureus-induced endometritis of mice. •ID13 could regulate the cytokines and suppress the TLR2-NF-κB signal pathway.

An Enhanced Variant Designed From DLP4 Cationic Peptide Against Staphylococcus aureus CVCC 546

Insect defensins are promising candidates for the development of potent antimicrobials against antibiotic-resistant Staphylococcus aureus (S. aureus). An insect defensin, DLP4, isolated from the hemolymph of Hermetia illucens larvae, showed low antimicrobial activity against Gram-positive (G+) pathogens and high cytotoxicity, which limited its effective therapeutic application. To obtain more potent and low cytotoxicity molecules, a series of peptides was designed based on the DLP4 template by changing the conservative site, secondary structure, charge, or hydrophobicity. Among them, a variant designated as ID13 exhibited strong antibacterial activity at low MIC values of 4-8 μg/mL to G+ pathogens (S. aureus: 4 μg/mL; Staphylococcus epidermidis: 8 μg/mL; Streptococcus pneumoniae: 4 μg/mL; Streptococcus suis: 4 μg/mL), which were lower than those of DLP4 (S. aureus: 16 μg/mL; S. epidermidis: 64 μg/mL; S. pneumoniae: 32 μg/mL; S. suis: 16 μg/mL), and cytotoxicity of ID13 (71.4% viability) was less than that of DLP4 (63.8% viability). ID13 could penetrate and destroy the cell membrane of S. aureus CVCC 546, resulting in an increase in potassium ion leakage; it bound to genomic DNA (gDNA) and led to the change of gDNA conformation. After treatment with ID13, perforated, wrinkled, and collapsed S. aureus CVCC 546 cells were observed in electron microscopy. Additionally, ID13 killed over 99.99% of S. aureus within 1 h, 2 × MIC of ID13 induced a post-antibiotic effect (PAE) of 12.78 ± 0.28 h, and 10 mg/kg ID13 caused a 1.8 log10 (CFU/g) (CFU: colony-forming units) reduction of S. aureus in infected mouse thigh muscles and a downregulation of TNF-α, IL-6, and IL-10 levels, which were superior to those of DLP4 or vancomycin. These findings indicate that ID13 may be a promising peptide antimicrobial agent for therapeutic application.

Methicillin-Resistant Staphylococcus aureus Strains in Swiss Pigs and Their Relation to Isolates from Farmers and Veterinarians

Methicillin-resistant Staphylococcus aureus (MRSA) has emerged over the last few decades as a One Health problem with an increasing prevalence in various animal species. The most notable animals are pigs, as asymptomatic carriers, and horses, where there is often an association with infections. The current study looked at the course of MRSA prevalence in Swiss livestock since 2009, with a special focus on pigs, followed by screening of veterinarians and farmers. Livestock isolates were obtained from the Swiss monitoring program and then characterized by spa typing. Concentrating on the year 2017, we analyzed the prevalence of MRSA in Swiss veterinarians and farmers, followed by whole-genome sequencing of selected human and animal strains. The phylogeny was assessed by applying core-genome multilocus sequence typing (MLST) and single-nucleotide polymorphism (SNP) analyses, followed by screening for resistance genes and virulence factors. The prevalence of MRSA in Swiss pigs showed a dramatic increase from 2% in 2009 to 44% in 2017. Isolates typically belonged to clonal complex 398 (CC398), split between spa t011 and t034. The higher prevalence was mainly due to an increase in t011. spa t034 strains from farmers were found to be closely associated with porcine t034 strains. The same could be shown for spa t011 strains from horses and veterinarians. spa t034 strains had a high number of additional resistance genes, and two strains had acquired the immune evasion cluster. However, all but one of the pig spa t011 strains clustered in a separate group. Thus, the increase in pig spa t011 strains does not directly translate to humans.IMPORTANCE MRSA is an important human pathogen; thus, its increasing prevalence in livestock over the last decade has a potentially large impact on public health. Farmers and veterinarians are especially at risk due to their close contact with animals. Our work demonstrates a dramatic increase in MRSA prevalence in Swiss pigs, from 2% in 2009 to 44% in 2017. Whole-genome sequencing allowed us to show a close association between farmer and pig strains as well as veterinarian and horse strains, indicating that the respective animals are a likely source of human colonization. Furthermore, we could demonstrate that pig spa t011 strains cluster separately and are probably less likely to colonize humans than are pig spa t034 strains. This research may provide a basis for a more substantiated risk assessment and preventive measures.

Occurrence of multidrug-resistant methicillin-resistant Staphylococcus aureus among healthy farm animals: a public health concern

Methicillin-resistant Staphylococcus aureus (MRSA) is an emerging pathogen causing serious public health threats. This study was conducted to investigate the occurrence of multidrug-resistant MRSA among apparently healthy farm animals to shed the light on the potential role of these animals as a reservoir for such pathogen. For this purpose, 195 nasal swabs from apparently healthy farm animals (52 sheep, 51 goats, 47 cattle and 45 buffalo) were screened for multidrug-resistant MRSA. MRSA was isolated using a selective chromogenic medium and identified by colonial characters, Gram’s stain films, conventional biochemical tests, coagulase test, resistance to cefoxitin and amplification of nuc and mecA genes. The antimicrobial susceptibility testing profile was performed by disk diffusion method to identify multidrug-resistant MRSA. Of 195 samples, 7 yielded MRSA with an overall prevalence 3.6%, whereas the prevalence rates were 3.8%, 3.9%, 4.3% and 2.2% for sheep, goats, cattle and buffalo, respectively. All MRSA isolates were multidrug-resistant strains. The phylogenetic analysis of 2 mecA gene sequences from the obtained isolates revealed that both sequences were clustered in the same clade with those derived from human clinical cases from different countries to highlight the public health burden of such strains. The distribution of multidrug-resistant MRSA among all examined farm animal species being apparently healthy points out that farm animals could represent a potential reservoir for multidrug-resistant MRSA with public health implications.

Unidirectional animal-to-human transmission of methicillin-resistant Staphylococcus aureus ST398 in pig farming; evidence from a surveillance study in southern Italy

Background

Livestock-associated methicillin-resistant Staphylococcus aureus (MRSA) belonging to clonal complex 398 is recognized as an occupational hazard for workers employed in intensive animal husbandry, especially in the swine-breeding chain. In this study, we compared the prevalence and epidemiological type of MRSA isolates from swine and farm workers in a large area of southern Italy.

Methods

Between January and March 2018, 88 workers from 32 farms where we had previously performed a survey for MRSA colonization of farmed pigs, were sampled by nasal swabbing. A follow-up investigation was conducted on seven workers 1 year after primary screening. MRSA isolates were characterized by MLST, spa and SCCmec typing, and tested for susceptibility to 15 antimicrobials. Epidemiological correlations between human and swine MRSA isolates were supported by Rep-MP3 and RAPD PCR fingerprinting, and whole-genome sequencing.

Results

The overall colonization rate of MRSA in swine farm workers was 21.6%, being significantly higher in intensive farms and in workers with direct animal contact. All human MRSA isolates were multi-drug resistant, belonged to the ST398 livestock clade, and did not carry Panton-Valentine leukocidin and enterotoxin genes. Notably, 94.1% of human MRSA isolates belonged to the same epidemiological type as swine MRSA isolates from the corresponding farm. Persistent MRSA carriage was documented in some workers 1 year after primary sampling.

Conclusions

We report a high prevalence of MRSA among swine farm workers, with higher colonization rates associated with intensive breeding and animal exposure. Our findings suggest unidirectional animal-to-human transmission of LA-MRSA and denote the high zoonotic transmissibility of the ST398 livestock clade.

Distribution of Toxinogenic Methicillin-Resistant and Methicillin-Susceptible Staphylococcus aureus from Different Ecological Niches in Algeria

The diffusion of Panton-Valentine leukocidin (PVL)-positive methicillin-resistant S. aureus (MRSA) is a health problem in Algeria. The objectives of the study were to investigate the global distribution of methicillin-susceptible S. aureus (MSSA) and MRSA isolates in different ecological niches in this country. In total, 2246 samples were collected from humans, livestock, wild animals, pets, food products and the aquatic environment, from 12 Algerian provinces. A total of 312 S. aureus were detected from 2446 samples (12.7%) in the screened niches. We observed the emergence of toxinogenic S. aureus representing 41% of the isolates. Among them, we noted the diffusion of ST80-IV CA-MRSA PVL + strains isolated in human, animals, and food and genetic diversity of MSSA PVL + isolates. This study suggests an alarming dissemination of MRSA-ST80 PVL + in both human and extra-human sources in Algeria. Moreover, MSSA may become a permanent reservoir of the PVL genes necessary for human infections.

Isolation and Molecular Identification of Virulence, Antimicrobial and Heavy Metal Resistance Genes in Livestock-Associated Methicillin-Resistant Staphylococcus aureus

Staphylococcus aureus is one of the most important pathogens of humans and animals. Livestock production contributes a significant proportion to the South African Gross Domestic Product. Consequently, the aim of this study was to determine for the first time the prevalence, virulence, antibiotic and heavy metal resistance in livestock-associated S. aureus isolated from South African livestock production systems. Microbial phenotypic methods were used to detect the presence of antibiotic and heavy metal resistance. Furthermore, molecular DNA based methods were used to genetically determine virulence as well as antibiotic and heavy metal resistance determinants. Polymerase chain reaction (PCR) confirmed 217 out of 403 (53.8%) isolates to be S. aureus. Kirby-Bauer disc diffusion method was conducted to evaluate antibiotic resistance and 90.8% of S. aureus isolates were found to be resistant to at least three antibiotics, and therefore, classified as multidrug resistant. Of the antibiotics tested, 98% of the isolates demonstrated resistance towards penicillin G. High resistance was shown against different heavy metals, with 90% (196/217), 88% (192/217), 86% (188/217) and 84% (183/217) of the isolates resistant to 1500 µg/mL concentration of Cadmium (Cd), Zinc (Zn), Lead (Pb) and Copper (Cu) respectively. A total of 10 antimicrobial resistance and virulence genetic determinants were screened for all livestock associated S. aureus isolates. Methicillin-resistant S. aureus (MRSA) isolates were identified, by the presence of mecC, in 27% of the isolates with a significant relationship (p < 0.001)) with the host animal. This is the first report of mecC positive LA-MRSA in South Africa and the African continent. The gene for tetracycline resistance (tetK) was the most frequently detected of the screened genes with an overall prevalence of 35% and the highest prevalence percentage was observed for goats (56.76%) followed by avian species (chicken, duck and wild birds) (42.5%). Virulence-associated genes were observed across all animal host species. The study reports the presence of luks/pv, a gene encoding the PVL toxin previously described to be a marker for community acquired-MRSA, suggesting the crossing of species between human and livestock. The high prevalence of S. aureus from the livestock indicates a major food security and healthcare threat. This threat is further compounded by the virulence of the pathogen, which causes numerous clinical manifestations. The phenomenon of co-selection is observed in this study as isolates exhibited resistance to both antibiotics and heavy metals. Further, all the screened antibiotic and heavy metal resistance genes did not correspond with the phenotypic resistance.