Identification of Livestock-Associated Methicillin-ResistantStaphylococcus aureusIsolates in Korea and Molecular Comparison Between Isolates from Animal Carcasses and Slaughterhouse Workers

High Prevalence of Clonal Complex 398 Methicillin-Susceptible and -Resistant Staphylococcus aureus in Pig Farms: Clonal Lineages, Multiple Drug Resistance, and Occurrence of the Staphylococcal Cassette Chromosome mec IX

High prevalence of livestock-associated methicillin-susceptible and -resistant Staphylococcus aureus (LA-MSSA and LA-MRSA, respectively) in livestock farms, particularly pig farms, is an increasingly serious threat to food safety and public health. In this study, 173 S. aureus (84 MRSA and 89 MSSA) isolates from healthy pigs, farm environments, and farm workers in Korea were examined to determine the (1) genetic diversity of S. aureus isolates (sequence type [ST], spa, and agr types), (2) staphylococcal cassette chromosome mec (SCCmec) types of MRSA isolates, and (3) multidrug resistance (MDR) phenotypes of MRSA and MSSA isolates. Clonal complex 398 (CC398) genotypes of MRSA and MSSA isolates, particularly CC398-spa type t571-agr I lineages, displaying MDR phenotypes were highly prevalent in pig farms. High prevalence of CC398-t571 MRSA and MSSA was more frequently associated with weaning piglets and growing pigs. Moreover, the same clonal lineages of S. aureus isolates colonized both pigs and farm workers, suggesting the transmission of antimicrobial-resistant CC398 MRSA and MSSA between pigs and humans in the pig farms. Furthermore, two dominant SCCmec types, SCCmec V and SCCmec IX, were identified in CC398 MRSA isolates colonizing healthy pigs. To the best of our knowledge, this is the first report of a CC398 LA-MRSA isolate carrying SCCmec IX in Korea. Collectively, these results suggest widespread distribution of the CC398 lineage among MRSA and MSSA isolates in pigs, farm environments, and farm workers in Korea.

Multilocus sequence type-dependent activity of human and animal cathelicidins against community-, hospital-, and livestock-associated methicillin-resistant Staphylococcus aureus isolates

Sequence type (ST) 5 methicillin-resistant Staphylococcus aureus (MRSA) with staphylococcal cassette chromosome mec (SCCmec) type II (ST5-MRSA-II) and ST72-MRSA-IV represent the most significant genotypes for healthcare- (HA) and community-associated (CA) MRSA in Korea, respectively. In addition to the human-type MRSA strains, the prevalence of livestock-associated (LA) MRSA clonal lineages, such as ST541 and ST398 LA-MRSA-V in pigs and ST692 LA-MRSA-V and ST188 LA-MRSA-IV in chickens, has recently been found. In this study, clonotype-specific resistance profiles to cathelicidins derived from humans (LL-37), pigs (PMAP-36), and chickens (CATH-2) were examined using six different ST groups of MRSA strains: ST5 HA-MRSA-II, ST72 CA-MRSA-IV, ST398 LA-MRSA-V, ST541 LA-MRSA-V, ST188 LA-MRSA-IV, and ST692 LA-MRSA-V. Phenotypic characteristics often involved in cathelicidin resistance, such as net surface positive charge, carotenoid production, and hydrogen peroxide susceptibility were also determined in the MRSA strains. Human- and animal-type MRSA strains exhibited clonotype-specific resistance profiles to LL-37, PMAP-36, or CATH-2, indicating the potential role of cathelicidin resistance in the adaptation and colonization of human and animal hosts. The ST5 HA-MRSA isolates showed enhanced resistance to all three cathelicidins and hydrogen peroxide than ST72 CA-MRSA isolates by implementing increased surface positive charge and carotenoid production. In contrast, LA-MRSA strains employed mechanisms independent of surface charge regulation and carotenoid production for cathelicidin resistance. These results suggest that human- and livestock-derived MRSA strains use different strategies to counteract the bactericidal action of cathelicidins during the colonization of their respective host species.

Co-occurrence of cfr-mediated linezolid-resistance in ST398 LA-MRSA and non-aureus staphylococci isolated from a pig farm

Linezolid resistance, mediated by the cfr gene, which confers resistant phenotypes to phenicols, lincosamides, oxazolidinones, pleuromutilins, and streptogramin A antimicrobials, has emerged in S. aureus and non-aureus staphylococci (NAS). Moreover, due to the transferable potential via plasmids, the spread of cfr among staphylococci is of great concern. In the present study, we investigated the prevalence of cfr-mediated linezolid resistance in ST398 methicillin-resistant S. aureus (MRSA) and NAS strains isolated from a pig farm. Among the 26 staphylococci isolates collected from a pig farm, 14 cfr-harboring ST398 MRSA and NAS (S. epidermidis, S. pasteuri, S. cohnii, and S. rostri) strains were resistant to linezolid and also carried the fexA gene. Comparative genome analysis of cfr-carrying linezolid-resistant ST398 MRSA and NAS (S. pasteuri, S. cohnii, and S. epidermidis) strains revealed that the segments harboring cfr in different staphylococcal strains showed ≥ 99 % sequence identity and the corresponding region containing the cfr, fexA, and Tn558 elements were located in a 38-kb plasmid, designated pSA12 of ST398 MRSA. These observations indicate that the cfr-carrying plasmids and/or fragments may be disseminated among staphylococci in a pig farm and possibly transmitted to staphylococci of human origin, subsequently posing a threat to public health. This is the first report of the co-existence of cfr in linezolid-resistant ST398 MRSA and NAS isolated from a pig farm in South Korea.

The Resistome and Mobilome of Multidrug-Resistant Staphylococcus sciuri C2865 Unveil a Transferable Trimethoprim Resistance Gene, Designated dfrE, Spread Unnoticed

Methicillin-resistant Staphylococcus sciuri (MRSS) strain C2865 from a stranded dog in Nigeria was trimethoprim (TMP) resistant but lacked formerly described staphylococcal TMP-resistant dihydrofolate reductase genes (dfr). Whole-genome sequencing, comparative genomics, and pan-genome analyses were pursued to unveil the molecular bases for TMP resistance via resistome and mobilome profiling. MRSS C2865 comprised a species subcluster and positioned just above the intraspecies boundary. Lack of species host tropism was observed. S. sciuri exhibited an open pan-genome, while MRSS C2865 harbored the highest number of unique genes (75% associated with mobilome). Within this fraction, we discovered a transferable TMP resistance gene, named dfrE, which confers high-level TMP resistance in Staphylococcus aureus and Escherichia coli. dfrE was located in a novel multidrug resistance mosaic plasmid (pUR2865-34) encompassing adaptive, mobilization, and segregational stability traits. dfrE was formerly denoted as dfr_like in Exiguobacterium spp. from fish farm sediment in China but escaped identification in one macrococcal and diverse staphylococcal genomes in different Asian countries. dfrE shares the highest identity with dfr of soil-related Paenibacillus anaericanus (68%). Data analysis discloses that dfrE has emerged from a single ancestor and places S. sciuri as a plausible donor. C2865 unique fraction additionally enclosed novel chromosomal mobile islands, including a multidrug-resistant pseudo-SCCmec cassette, three apparently functional prophages (Siphoviridae), and an SaPI4-related staphylococcal pathogenicity island. Since dfrE seems not yet common in staphylococcal clinical specimens, our data promote early surveillance and enable molecular diagnosis. We evidence the genome plasticity of S. sciuri and highlight its role as a resourceful reservoir for adaptive traits.

IMPORTANCE The discovery and surveillance of antimicrobial resistance genes (AMRG) and their mobilization platforms are critical to understand the evolution of bacterial resistance and to restrain further expansion. Limited genomic data are available on Staphylococcus sciuri; regardless, it is considered a reservoir for critical AMRG and mobile elements. We uncover a transferable staphylococcal TMP resistance gene, named dfrE, in a novel mosaic plasmid harboring additional resistance, adaptive, and self-stabilization features. dfrE is present but evaded detection in diverse species from varied sources geographically distant. Our analyses evidence that the dfrE-carrying element has emerged from a single ancestor and position S. sciuri as the donor species for dfrE spread. We also identify novel mobilizable chromosomal islands encompassing AMRG and three unrelated prophages. We prove high intraspecies heterogenicity and genome plasticity for S. sciuri. This work highlights the importance of genome-wide ecological studies to facilitate identification, characterization, and evolution routes of bacteria adaptive features.

Detection and molecular characterisation of methicillin-resistant Staphylococcus aureus isolated from raw meat in the retail market

OBJECTIVES

This study aimed to detect and characterise methicillin-resistant Staphylococcus aureus (MRSA) from retail meat in the Czech Republic.

METHODS

Isolates were identified by PCR detection of the S. aureus-specific fragment Sa442 and mecA gene. spa typing, MLST, detection of genes encoding staphylococcal enterotoxins, Panton-Valentine leukocidin (pvl), exfoliative toxins A and B (eta and etb), toxic shock syndrome toxin (tst) and staphylokinase (sak), detection of φSa3 prophage and antimicrobial susceptibility testing were performed.

RESULTS

Of 65 raw meat samples examined (poultry, beef, pork and rabbit), 23 (35.4%) were positive for MRSA. Twelve positive samples originated from poultry (12/33; 36.4%), while the remaining eleven came from pork (9/9; 100%) and pork/beef mixed minced meat (2/5; 40.0%). Eight spa types belonging to five different sequence types (STs) were identified. ST398 was the most frequent (28/36; 77.8%), presenting spa types t011, t034, t2576, t4132, t588 and t899. Other livestock-associated MRSA STs (ST9-t899, ST5-t002, ST692-t8646 or the newly described ST4034-t899) were also sporadically identified. In seven isolates (19.4%), one or more staphylococcal enterotoxin genes were detected, with sea, seg and sei prevailing. Three isolates from turkey [ST398-t899 (n = 2) and ST398-t011] harboured the sak gene, and the latter also harboured the sea gene. Seven isolates from poultry harboured the φSa3 prophage and were resistant to tetracycline.

CONCLUSION

Specific kinds of meat appear to be a possible source of MRSA, although the risk to humans is hard to define. Therefore, surveillance of MRSA in meat as well as hygienic practices should be improved.

Mobile Oxazolidinone Resistance Genes in Gram-Positive and Gram-Negative Bacteria

Seven mobile oxazolidinone resistance genes, including cfr, cfr(B), cfr(C), cfr(D), cfr(E), optrA, and poxtA, have been identified to date. The cfr genes code for 23S rRNA methylases, which confer a multiresistance phenotype that includes resistance to phenicols, lincosamides, oxazolidinones, pleuromutilins, and streptogramin A compounds. The optrA and poxtA genes code for ABC-F proteins that protect the bacterial ribosomes from the inhibitory effects of oxazolidinones. The optrA gene confers resistance to oxazolidinones and phenicols, while the poxtA gene confers elevated MICs or resistance to oxazolidinones, phenicols, and tetracycline. These oxazolidinone resistance genes are most frequently found on plasmids, but they are also located on transposons, integrative and conjugative elements (ICEs), genomic islands, and prophages. In these mobile genetic elements (MGEs), insertion sequences (IS) most often flanked the cfr, optrA, and poxtA genes and were able to generate translocatable units (TUs) that comprise the oxazolidinone resistance genes and occasionally also other genes. MGEs and TUs play an important role in the dissemination of oxazolidinone resistance genes across strain, species, and genus boundaries. Most frequently, these MGEs also harbor genes that mediate resistance not only to antimicrobial agents of other classes, but also to metals and biocides. Direct selection pressure by the use of antimicrobial agents to which the oxazolidinone resistance genes confer resistance, but also indirect selection pressure by the use of antimicrobial agents, metals, or biocides (the respective resistance genes against which are colocated on cfr-, optrA-, or poxtA-carrying MGEs) may play a role in the coselection and persistence of oxazolidinone resistance genes.

Nationwide Surveillance on Antimicrobial Resistance Profiles of Staphylococcus aureus Isolated from Major Food Animal Carcasses in South Korea During 2010-2018

Contamination of meat with antimicrobial-resistant bacteria represents a major public health threat worldwide. In this study, we determined the antimicrobial resistance profiles and resistance trends of Staphylococcus aureus isolated from major food animal carcasses (408 cattle, 1196 pig, and 1312 chicken carcass isolates) in Korea from 2010 to 2018. Approximately 75%, 92%, and 77% of cattle, pig, and chicken carcass isolates, respectively, were resistant to at least one antimicrobial agent. Resistance to penicillin (62.1%) was the highest, followed by resistance to tetracycline (42.1%) and erythromycin (28.2%). About 30% of pig and chicken isolates were resistant to ciprofloxacin. We observed linezolid resistance only in pig isolates (2.3%). However, all S. aureus isolates were sensitive to rifampin and vancomycin. We noted an increasing but fluctuating trend of kanamycin and penicillin resistance in cattle isolates. Similarly, the chloramphenicol, ciprofloxacin, tetracycline, and trimethoprim resistance rates were increased but fluctuated through time in pig isolates. Methicillin-resistant S. aureus (MRSA) accounted for 5%, 8%, and 9% of the cattle, pig, and chicken isolates, respectively. The MRSA strains exhibited significantly high resistance rates to most of the tested antimicrobials, including ciprofloxacin, erythromycin, and tetracycline compared with methicillin-susceptible S. aureus (MSSA) strains. Notably, a relatively high percentage of MRSA strains (5.2%) recovered from pig carcasses were resistant to linezolid compared with MSSA strains (2.1%). In addition, almost 37% of the isolates were multi-drug resistant. S. aureus isolates recovered from major food animal carcasses in Korea exhibited resistance to clinically important antimicrobials, posing a public health risk.

Genomic Information on Linezolid-Resistant Sequence-Type 398 Livestock-Associated Methicillin-Resistant Staphylococcus aureus Isolated from a Pig

The frequent occurrence of sequence-type 398 (ST398) livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) in pigs has become a major public health concern owing to the increased zoonotic potential of the pathogen. Recently, a novel oxazolidinone resistance gene, chloramphenicol-florfenicol resistant (cfr), conferring multiresistance phenotypes to phenicols, lincosamides, oxazolidinones, pleuromutilins, and streptogramin A (PhLOPS_A), has been found among ST398 LA-MRSA strains isolated from pigs. In this study, we report the first in silico genome analysis of a linezolid-resistant ST398 LA-MRSA strain, designated PJFA-521M, recovered from a pig in Korea. Genomic analyses revealed that the presence of the cfr gene was responsible for the observed linezolid resistance in the PJFA-521M strain. Moreover, newer antimicrobial resistance genes, such as the dfrG, aadE, spw, lsa(E), lnu(B), and fexA genes, were found in the PJFA-521M strain. In addition to the genetic elements for antimicrobial resistance, the carriage of various virulence genes for adherence, invasion, and immunomodulation was identified in the genome, especially within several mobile genetic elements (MGEs). The presence of multiple antimicrobial resistance genes and virulence genes on MGEs in the genome of a linezolid-resistant ST398 LA-MRSA should raise awareness regarding the use of other antimicrobial agents in pig farms and may also provide selective pressure for the prevalence of the cfr gene and the associated multidrug-resistant phenotype.

Effectiveness of ear skin swabs for monitoring methicillin-resistant Staphylococcus aureus ST398 in pigs at abattoirs

Monitoring the prevalence of livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) in pigs could be useful for managing transmission risk to humans. To optimize sampling for LA-MRSA monitoring, we compared the sensitivity of MRSA isolation from skin swabs taken behind the ear and nasal swabs collected from 276 pigs and investigated the prevalence of MRSA in their carcasses. MRSA was isolated from 40 behind the ear skin swabs (14.5%), which was statistically higher than the number isolated from nasal swabs (23 samples, 8.3%). MRSA prevalence in the carcasses was 0.4%. All MRSA isolates were sequence type 398 lineage. Sampling of both the skin behind the ear and nasal mucosa in a pig is recommended to investigate the prevalence of LA-MRSA in pigs.

Short communication: First detection of Panton-Valentine leukocidin-positive methicillin-resistant Staphylococcus aureus ST30 in raw milk taken from dairy cows with mastitis in South Korea

We identified 199 Staphylococcus aureus isolates from quarter milk samples of 1,289 dairy cattle between 2014 and 2018. About 66% of the isolates were resistant to at least 1 antimicrobial agent; the highest rate of resistance was to penicillin, followed by resistance to ampicillin, erythromycin, and sulfadimethoxine. We obtained 30 methicillin-resistant S. aureus (MRSA) strains from 6 farms in 3 provinces. The MRSA strains exhibited a significantly higher resistance rate to most of the tested antimicrobials than the oxacillin-susceptible strains. The MRSA strains represented 5 genotypes: ST72-t324-SCCmec IV (n = 14), ST30-t1752-SCCmec IV (n = 8), ST188-t189-SCCmec NT (n = 6), ST188-t2284-SCCmec NT (n = 1), and NT-NT-SCCmec IV (n = 1). One of the ST188 MRSA strains represented a novel staphylococcal protein A (spa) type (t2284). In addition, 7 of the 8 ST30 MRSA strains were Panton-Valentine leukocidin (PVL)-positive and carried various staphylococcal enterotoxin encoding genes. This is the first report of PVL-positive ST30 MRSA-t1752-SCCmec IV from bovine mastitis in Korea. All of ST72-t324-SCCmec IV MRSA strains carried staphylococcal enterotoxin and leukotoxin encoding genes. They were also sensitive to most of the tested non-β-lactam antimicrobials. In contrast, ST188-t189 MRSA strains were resistant to multiple antimicrobials and predominantly carried the leukotoxin encoding gene. Taken together, these findings may indicate that dairy cows could be a major source for spreading MRSA strains, and contaminated milk could be a vehicle for transmission. Suitable hygienic measures should be established in dairy farms and processing plants to limit the likelihood of introducing MRSA into the food chain.

Emergence of cfr-Mediated Linezolid Resistance in Staphylococcus aureus Isolated from Pig Carcasses

Altogether, 2547 Staphylococcus aureus isolated from cattle (n = 382), pig (n = 1077), and chicken carcasses (n = 1088) during 2010-2017 were investigated for linezolid resistance and were further characterized using molecular methods. We identified linezolid resistance in only 2.3% of pig carcass isolates. The linezolid-resistant (LR) isolates presented resistance to multiple antimicrobials, including chloramphenicol, clindamycin, and tiamulin. Molecular investigation exhibited no mutations in the 23S ribosomal RNA. Nevertheless, we found mutations in ribosomal proteins rplC (G121A) and rplD (C353T) in one and seven LR strains, respectively. All the LR isolates carried the multi-resistance gene cfr, and six of them co-carried the mecA gene. Additionally, all the LR isolates co-carried the phenicol exporter gene, fexA, and presented a high level of chloramphenicol resistance. LR S. aureus isolates represented 10 genotypes, including major genotypes ST433-t318, ST541-t034, ST5-t002, and ST9-t337. Staphylococcal enterotoxin and leukotoxin-encoding genes, alone or in combination, were detected in 68% of LR isolates. Isolates from different farms presented identical or different pulsed-field gel electrophoresis patterns. Collectively, toxigenic and LR S. aureus strains pose a crisis for public health. This study is the first to describe the mechanism of linezolid resistance in S. aureus isolated from food animal products in Korea.

Resistance profiling and molecular characterization of Staphylococcus aureus isolated from goats in Korea

Staphylococcus aureus is among the most common zoonotic pathogens that cause foodborne illnesses worldwide. The main objectives of the current study were therefore to determine the antimicrobial susceptibility profiles of S. aureus isolated from goats in Korea and to investigate the molecular characteristics of identified methicillin-resistant S. aureus (MRSA). In the study, 481 S. aureus isolates (431 from the nasal cavity and 50 from carcass) were recovered from 1146 carcasses and nasal swabs between July 2018 and January 2019. Approximately 82% and 72.6% of nasal and carcass isolates, respectively, were resistant to at least one antimicrobial agent, with the highest rate of resistance to penicillin, followed by resistance to chloramphenicol and tetracycline. Relatively small proportions of the isolates were resistant to cefoxitin, clindamycin, and erythromycin. However, all S. aureus isolates were sensitive to linezolid, rifampin, and vancomycin. Six MRSA isolates were obtained, three each from the nasal cavity and carcass. MRSA isolates were of two sequence types (ST) (ST72 and ST398), three spa types (t664, t324, and t571), and two SCCmec types (IV and V). The ST72 MRSA isolates had identical PFGE profiles. In addition, ST72 MRSA-SCCmec IV isolates carried at least six staphylococcal leukotoxin- and enterotoxin-encoding genes (lukED, seg, sei, sem, sen, seo, and seq). The remaining ST398 isolate carried only the lukED gene and was additionally resistant to eight non-β-lactam antibiotics. To the best of our knowledge, this is the first report of MRSA from goats in Korea. There is a possibility of transmission of MRSA from goat to human or contamination of food products. Therefore, regular microbiological investigation in goats, farms, and slaughterhouses is critical to determine the existence of virulent and multi-drug resistant (MDR) S. aureus and to implement preventive strategies.

Prevalence and Characteristics of Antimicrobial-Resistant Staphylococcus aureus and Methicillin-Resistant Staphylococcus aureus from Retail Meat in Korea

This study was to investigate the prevalence and characteristics of antimicrobial-resistant Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) from 4,264 retail meat samples including beef, pork, and chicken in Korea between 2013 and 2018. A broth microdilution antimicrobial susceptibility testing was performed for S. aureus. Molecular typing by multilocus sequence typing (MLST), spa typing, and pulsed-field gel electrophoresis (PFGE), was performed on mecA-positive S. aureus strain. S. aureus was isolated at a rate of 18.2% (777/4,264), of which MRSA comprised 0.7% (29 strains). MLST analysis showed that 11 out of the 29 MRSA isolates were predominantly sequence type (ST) 398 (37.9%). In addition, ST72, ST692, ST188, ST9, and ST630 were identified in the MRSA isolates. The spa typing results were classified into 11 types and showed a high correlation with MLST. The antimicrobial resistance assays revealed that MRSA showed 100% resistance to cefoxitin and penicillin. In addition, resistance to tetracycline (62.1%), clindamycin (55.2%), and erythromycin (55.2%) was relatively high; 27 of the 29 MRSA isolates exhibited multidrug resistance. PFGE analysis of the 18 strains excluding the 11 ST398 strains exhibited a maximum of 100% homology and a minimum of 64.0% homology. Among these, three pairs of isolates showed 100% homology in PFGE; these results were consistent with the MLST and spa typing results. Identification of MRSA at the final consumption stage has potential risks, suggesting that continuous monitoring of retail meat products is required.

Livestock-associated methicillin-resistant Staphylococcus aureus in Korea: antimicrobial resistance and molecular characteristics of LA-MRSA strains isolated from pigs, pig farmers, and farm environment

The emergence of livestock-associated (LA)-methicillin-resistant Staphylococcus aureus (MRSA) in livestock animal has become a significant zoonotic concern. In the present study, we investigated nationwide prevalence of LA-MRSA across pork production chain including pig farms, slaughterhouses, and retail markets. A total of 40 MRSA strains were isolated during the investigation and the overall prevalence of MRSA was 3.4% (n = 37), 0.6% (n = 2), and 0.4% (n = 1) in pig farms, slaughterhouses, and retail markets, respectively. Multilocus sequence typing analyses revealed that the 2 most significant clonal lineages in pork production chain in Korea were ST398 (n = 25) and ST541 (n = 6). All of the 40 MRSA isolates were further characterized to investigate key genotypic and phenotypic correlates associated with the emergence and spread of clonal complex 398 (CC398; ST398, and ST541) LA-MRSA. Although the prevalence of swine-associated MRSA was still relatively low and mostly restricted to pig farms, multidrug-resistant CC398 LA-MRSA isolates with new spa types (t18102 and t18103) were identified as a major clonal lineage. The CC398 LA-MRSA strains tended to exhibit increased levels of multiple drug resistance (MDR) phenotype compared with non-CC398 MRSA strains. Of note, in comparison with non-CC398 MRSA isolates, CC398 LA-MRSA isolates exhibited significantly enhanced tetracycline (TET) and zinc resistance. These findings suggested that co-selection pressure associated with MDR phenotype, especially TET resistance, and zinc resistance may have played a significant role in the emergence and persistence of CC398 LA-MRSA in pig farms in Korea.

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.

Occurrence and Characteristics of Methicillin-Resistant and -Susceptible Staphylococcus aureus Isolated from the Beef Production Chain in Korea

The emergence and persistence of methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant S. aureus (MRSA) in livestock animals have been reported as a potential risk factor for transmission to humans. In this study, we investigated the nationwide prevalence and characteristics of MRSA and MSSA in the Korean beef production system, including retail markets, slaughterhouses, and cattle farms. From a total of 1,285 samples, only 5 MRSA strains were isolated: from a farmer (1 ST72 MRSA), a carcass sample from a slaughterhouse (1 ST72 MRSA), and beef cattle (3 ST5 MRSA). In addition, 11 MSSA strains were isolated from beef cattle (n=3), humans (1 farmer, 1 slaughterhouse worker, and 4 retail market workers), and carcass samples (n=1) and slaughterhouse environment (n=1). Although the prevalence of MRSA and MSSA in beef cattle was much lower than that reported in pigs, 5/5 MRSA and 2/11 MSSA strains displayed multiple drug resistance (MDR) phenotypes. Unlike the swine-associated MRSA, no correlation was found between tetracycline/zinc resistance and MDR phenotype. However, MRSA strains had an identical set of staphylococcal enterotoxins and exhibited enhanced levels of resistance to antimicrobial peptides (PMAP-36 and LL-37) compared to the MSSA strains. In conclusion, continued and systemic surveillance of livestock, meat products, and humans in close contact with livestock/meat products is necessary to prevent the transmission of MRSA and MSSA to humans.

Prevalence and characteristics of livestock-associated methicillin-susceptible Staphylococcus aureus in the pork production chain in Korea

The emergence and prevalence of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) in livestock animals have become a worldwide public health concern. While the prevalence and genetic profiles of MRSA strains in pigs and pork meat have been actively studied, livestock-associated MSSA strains have only been characterized in a few small-scale studies. In this investigation, we assessed the nationwide prevalence of MSSA in the Korean pig production chain, including pig farms, slaughterhouses, and retail markets. Among the 41 MSSA strains, the predominant clonal lineages were sequence type (ST) 398 (n = 15, 37%) and ST5 (n = 13, 32%). Although the overall prevalence of MSSA (2.58%) was low and mostly restricted to pig farms, ST398 MSSA strains showed higher level of multidrug resistance phenotype versus non-ST398 MSSA strains. In addition to the MDR phenotype, all of the ST398 MSSA strains exhibited resistance to tetracycline as they harbored the tet(K), tet(L), and/or tet(M) genes. However, ST398 MSSA strains did not exhibit increased resistance to zinc compared with the non-ST398 strains. This study is the first to provide evidence of ST398 MSSA emergence in livestock animals in Korea. Further studies are necessary to elucidate the potential of ST398 MSSA strains for human transmission. Our findings suggest that the MDR phenotype and high levels of tetracycline resistance may have played an important role in the emergence and prevalence of ST398 MSSA in pig farms in Korea.

Detection and phylogeny of Staphylococcus aureus sequence type 398 in Taiwan

Background

Methicillin-resistant Staphylococcus aureus (MRSA) ST398 is a livestock associated-bacterium that is most prevalent in Europe. Human-adapted MRSA ST398 was recently reported from China, but there is no data available yet for Taiwan.

Methods

To identify S. aureus ST398 isolates, we examined 6413 S. aureus isolates (5632 MRSA and 781 susceptible strains) that were collected in Taiwan between 1995 and 2017. If isolates could not be typed by pulsed-field gel electrophoresis upon Sma I digestion, we performed further characterization and complete genome sequencing.

Results

We identified 18 ST398 S. aureus isolates from 16 subjects (0.28%), including 6 sensitive and 12 resistant strains. Of these, 14 were colonizing isolates, 3 were clinical (infecting) isolates and one isolate was from a pork specimen. All 3 infecting isolates were MSSA strains identified in 2015 from two children with recurrent otitis media or sinusitis. The other 3 MSSA isolates were identified from workers handling pork (2) or pork meat (1) in 2015. The first 5 MRSA colonizing isolates were identified from residents in two nursing homes in 2012. Six MRSA isolates were identified from residents and foreign employees at a nursing home in 2016 and one MRSA from a foreign worker in 2017. Phylogenetic analysis of genome sequences indicated that all 12 local ST398 MRSA strains cluster together, human-adapted and phylogenetically related to a human MRSA strain identified in China in 2002. Two local MSSA isolates could be linked to isolates from livestock. The toxin profiles were similar for the MRSA and MSSA isolates.

Conclusions

Our results demonstrate that S. aureus ST398 was present in Taiwan in 2012 and potentially earlier. Although some isolates could be linked to livestock, most ST398 S. aureus isolates identified in Taiwan, particularly MRSA, represent human-adapted strains. Local transmission of human-adapted MRSA ST398 strains has occurred in nursing homes in Taiwan, possibly after import from China. Further surveillance is needed.

Effect of tetracycline treatment regimens on antibiotic resistance gene selection over time in nursery pigs

Background

The majority of antimicrobials given during the production of pigs are given to nursery pigs. The influence of antimicrobial use on the levels of antimicrobial resistant (AMR) genes is important to quantify to be able to assess the impact of resistance on the food chain and risk to human and animal health.

Results

This study investigated the response on the levels of nine AMR genes to five different treatment strategies with oxytetracycline, and the dynamics of gene abundance over time by following 1167 pigs from five different farms in Denmark.

The results showed no significant difference between treatments and an increase in abundance for the efflux pump encoding tet(A) gene and the genes encoding the ribosomal protection proteins tet(O) and tet(W) tetracycline resistant genes following treatment, while tet(M) showed no response to treatment. However, it was also observed that the levels of tet(O), tet(W), and ermB in some farms would drift more over time compared to a single treatment-course with antibiotic.

Conclusion

This study underlines the large variation in AMR levels under natural conditions and the need for increased investigation of the complex interactions of antimicrobial treatment and other environmental and managerial practices in swine production on AMR gene abundance.

Prevalence and Characteristics of Methicillin-Resistant Staphylococcus aureus Isolates in Pigs and Pig Farmers in Korea

In this study, we investigated the prevalence and characteristics of methicillin-resistant Staphylococcus aureus (MRSA) isolates from pigs and pig farmers in Korea. A total of 1245 nasal swabs were collected from pigs and farmers at 53 pig farms in nine provinces from 2012 to 2016. The prevalence of MRSA was 7.9% (88/1119) in pigs and 16.7% (21/126) in farmers. Among 119 farmers working on conventional farms, 21 (17.6%) tested positive for MRSA. However, no MRSA was detected in either pigs or farmers at four organic farms. The individual pig-level prevalence of MRSA differed between age groups, with the percentage of positive samples being highest in weaners (17.3%), followed by growers (9.0%), piglets (6.5%), finishers (4.4%), and sows (0%). Two different lineages of MRSA were detected among the 109 isolates from pigs and farmers: (1) livestock-associated types of MRSA belonging to 27 isolates of ST541-t034-V, 24 isolates of ST398-t571-V, 17 isolates of ST398-t034 variant (G420A)-V, and one isolate of ST541-t8588-V; and (2) community-associated types of MRSA belonging to 21 isolates of ST188-t189-IV, 14 isolates of ST72-t324-IV, three isolates of ST72-t664-IV, one isolate of ST72-t148-IV, and one isolate of ST72-t5440-IV. Identical genotypes were detected in both pigs and farmers at six farms. New MRSA clones were isolated from pigs (ST398-t034 (G420A)-V, ST188-t189-IV, and ST398-t571-V) and pig farmers (ST541-t8588-V and ST72-t5440-IV). The prevalence of MRSA was also correlated with antibiotic usage, and the clones showed diversification between pigs and farmers. Ultimately, the increased frequency and diversification of livestock-associated MRSA could be a potential threat to public health in Korea. To our knowledge, this is the first study to report the prevalence and characteristics of MRSA in pigs and pig farmers in Korea.

Characterization of the Multi-Drug Resistance Gene cfr in Methicillin-Resistant Staphylococcus aureus (MRSA) Strains Isolated From Animals and Humans in China

We investigated cfr-positive and -negative MRSA strains isolated from animals and humans in different geographical areas of China, from 2011 to 2016. Twenty cfr-positive strains (15.6%) were identified from 128 MRSA strains including 17 from food animals and three from humans. The resistance rates and prevalence of the tested antibiotic resistance genes (ARGs) in the cfr-positive MRSA isolates were higher than that in the cfr-negative MRSA isolates. All cfr-positive MRSA isolates were co-carrying fexA and ermC, and had significantly higher optrA incidence rate vs. the cfr-negative isolates (P < 0.05). In addition, multilocus sequence typing (MLST) assays showed that ST9 and spa-type t899 were the most prevalent ST and spa types in the study strains. However, all of the 20 cfr-positive and 10 randomly selected cfr-negative MRSA isolates were clonally unrelated as determined by pulsed-field gel electrophoresis (PFGE) analyses. Importantly, the cfr gene was successfully transferred to a recipient Staphylococcus aureus strain RN4220 from 13 of the 20 cfr-positive MRSA isolates by electroporation. Among these 13 cfr-positive MRSA isolates, two different genetic contexts surrounding cfr were determined and each was associated with one type of cfr-carrying plasmids. Of note, the predominant genetic context of cfr was found to be a Tn558 variant and locate on large plasmids (∼50 kb) co-harboring fexA in 11 of the 13 MRSA isolates. Furthermore, the cfr gene was also identified on small plasmids (∼ 7.1 kb) that co-carried ermC in two of the 13 MRSA isolates. Our results demonstrated a high occurrence of multi-drug resistance in cfr-positive MRSA isolates, and the spread of cfr might be attributed to horizontal dissemination of similar cfr-carrying transposons and plasmids.

Antimicrobial Resistance Distribution Differs Among Methicillin Resistant Staphylococcus aureus Sequence Type (ST) 5 Isolates From Health Care and Agricultural Sources

Antimicrobial resistance (AMR) is an expanding public health concern and methicillin resistant Staphylococcus aureus (MRSA) is a notable example. Since the discovery of livestock associated MRSA (LA-MRSA), public health concerns have arisen surrounding the potential of LA-MRSA isolates to serve as a reservoir for AMR determinants. In this study, we compare swine associated LA-MRSA ST5 and human clinical MRSA ST5 isolates for phenotypic antimicrobial susceptibilities determined via broth microdilution and genotypic determinants of AMR using whole genome sequencing and comparative genomic analysis to identify AMR elements. Swine associated LA-MRSA ST5 isolates exhibited phenotypic resistance to fewer antibiotics than clinical MRSA ST5 isolates from humans with no swine contact. Distinct genomic AMR elements were harbored by each subgroup, with little overlap in shared AMR genes between swine associated LA-MRSA ST5 and clinical MRSA ST5 isolates. Our results demonstrate that phenotypic antimicrobial susceptibilities and genotypic determinants of AMR among swine associated LA-MRSA ST5 and clinical MRSA ST5 isolates are separate and distinct.

Prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in broilers and workers at 'pluck shops' in Trinidad

Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) is a cause of zoonotic infections in many countries. People with occupational contact with food animal production are at risk of colonization. The aim of this study was to determine the prevalence of MRSA and their frequency of resistance to other antimicrobial agents from broilers and workers at the 'pluck shops' in Trinidad. For isolation of MRSA, choanal, cloacal and pharyngeal swabs taken from broilers and nasal swabs from humans were enriched then plated on CHROMagar MRSA and Brilliance MRSA. MRSA was confirmed using the PBP2a test kit, resistance to oxacillin and cefoxitin and polymerase chain reaction (PCR) for the mecA gene. Antimicrobial resistance of the MRSA isolates to 16 antimicrobial agents was determined using the disc diffusion method. Of the 287 broilers and 47 humans sampled, MRSA was isolated at a frequency of 2 (0.7%) and 0 (0.0%) respectively. All the MRSA isolates exhibited resistance to one or more of the 16 antimicrobial agents. The study demonstrated that broilers at 'pluck shops' in Trinidad harbor MRSA. This is the first isolation of MRSA from poultry in Trinidad, West Indies, and this finding is of public health significance since occupational exposure of humans can lead to increased risk of acquiring MRSA infections.

Staphylococcus aureus and Methicillin-Resistant Staphylococcus aureus in Workers in the Food Industry

Staphylococcus aureus is part of the common flora on the skin and mucous membranes of mammals and approximately 20–30% of humans are persistently colonized, mainly by mostly susceptible human-adapted isolates. In contrast, colonization with methicillin-resistant S. aureus is rare (approximately 1%), predominantly transient and associated with prior contact to the health care system. Additionally, in recent years livestock-associated S. aureus clones contributed to colonization in humans, especially in those working in close contact to farm animals. A considerable percentage of colonizing S. aureus isolates is equipped with enterotoxin genes. Humans carrying enterotoxigenic isolates represent a contamination source when handling food, thus generating a continuous risk of S. aureus food intoxication. Molecular characterization of isolates colonizing humans and obtained from food, respectively, enables the tracing of food-related outbreaks back to the source of food intoxication. We will summarize current knowledge about the S. aureus population colonizing humans, including those in close contact to animals and food, respectively. Additionally, we will review data on the molecular characterization of S. aureus isolates related to staphylococcal foodborne disease and the elucidation of staphylococcal foodborne outbreaks. Staphylococcal food poisoning is a common foodborne disease, mediated by the ingestion of enterotoxins produced by enterotoxigenic strains of S. aureus. For several outbreaks of foodborne S. aureus disease, colonized personnel could be identified as the source of food contamination. However, because of the widespread occurrence of enterotoxigenic strains as human colonizers and the often transient nature of colonization, the source of contamination cannot always be identified unambiguously. Therefore, compliance with hygiene measures is the most important requirement to prevent food contamination by both human colonization and environmental S. aureus reservoirs.

Review of Nonfoodborne Zoonotic and Potentially Zoonotic Poultry Diseases

Emerging and re-emerging diseases are continuously diagnosed in poultry species. A few of these diseases are known to cross the species barrier, thus posing a public health risk and an economic burden. We identified and synthesized global evidence for poultry nonfoodborne zoonoses to better understand these diseases in people who were exposed to different poultry-related characteristics (e.g., occupational or nonoccupational, operational types, poultry species, outbreak conditions, health status of flocks). This review builds on current knowledge on poultry zoonoses/potentially zoonotic agents transmitted via the nonfoodborne route. It also identifies research gaps and potential intervention points within the poultry industry to reduce zoonotic transmission by using various knowledge synthesis tools such as systematic review (SR) and qualitative (descriptive) and quantitative synthesis methods (i.e., meta-analysis). Overall, 1663 abstracts were screened and 156 relevant articles were selected for further review. Full articles (in English) were retrieved and critically appraised using routine SR methods. In total, eight known zoonotic diseases were reviewed: avian influenza (AI) virus (n = 85 articles), Newcastle disease virus (n = 8), West Nile virus (WNV, n = 2), avian Chlamydia (n = 24), Erysipelothrix rhusiopathiae (n = 3), methicillin-resistant Staphylococcus aureus (MRSA, n = 15), Ornithonyssus sylvarium (n = 4), and Microsporum gallinae (n = 3). In addition, articles on other viral poultry pathogens (n = 5) and poultry respiratory allergens derived from mites and fungi (n = 7) were reviewed. The level of investigations (e.g., exposure history, risk factor, clinical disease in epidemiologically linked poultry, molecular studies) to establish zoonotic linkages varied across disease agents and across studies. Based on the multiple outcome measures captured in this review, AI virus seems to be the poultry zoonotic pathogen that may have considerable and significant public health consequences; however, epidemiologic reports have only documented severe human cases clustered in Asia and not in North America. In contrast, avian Chlamydia and MRSA reports clustered mainly in Europe and less so in North America and other regions. Knowledge gaps in other zoonoses or other agents were identified, including potential direct (i.e., nonmosquito-borne) transmission of WNV from flocks to poultry workers, the public health and clinical significance of poultry-derived (livestock-associated) MRSA, the zoonotic significance of other viruses, and the role of poultry allergens in the pathophysiology of respiratory diseases of poultry workers. Across all pathogens reviewed, the use of personal protective equipment was commonly cited as the most important preventive measure to reduce the zoonotic spread of these diseases and the use of biosecurity measures to reduce horizontal transmission in flock populations. The studies also emphasized the need for flock monitoring and an integrated approach to prevention (i.e., veterinary-public health coordination with regard to diagnosis, and knowledge translation and education in the general population) to reduce zoonotic transmission.

Phenotypic and molecular characteristics of Staphylococcus aureus and methicillin-resistant Staphylococcus aureus in slaughterhouse pig-related workers and control workers in Guangdong Province, China

Pig farmers and veterinarians have high prevalence of methicillin-resistant Staphylococcus aureus (MRSA) due to the occupational livestock exposure, while few reported this association on slaughterhouse workers. We conducted this cross-sectional study to explore the phenotypic and molecular characteristics of S. aureus and MRSA in slaughterhouse pig-related workers and control workers in Guangdong Province, China. Participants were interviewed and provided two nasal swabs. Swabs were tested for S. aureus, and isolates were further tested for antimicrobial susceptibility, virulence genes and multi-locus sequence typing. Compared with control workers, pig-related workers have significantly higher prevalence of MRSA carriage (adjusted odd ratio (aOR) 3·70, 95% CI 1·63-8·40). The proportions of MRSA resistant to clindamycin, erythromycin, tetracycline or chloromycetin were significantly higher in pig-related workers than in control workers. The predominant phenotypes of S. aureus were resistant to penicillin, clindamycin, erythromycin and tetracycline. Three MRSA CC9 isolates with livestock-associated characteristics (resistance to tetracycline and absence of immune evasion cluster (IEC) genes) were detected in pig-related workers but not in control workers. For human-associated CCs (CC7, CC59, CC6, and CC188), there was no significant difference in IEC profile or antimicrobial resistance between the groups. These findings reveal that there may be a potential risk for livestock-to-human transmission of LA-MRSA and human-to-human transmission of human-associated MRSA.

Antibiotic Application and Emergence of Multiple Antibiotic Resistance (MAR) in Global Catfish Aquaculture

Catfish is one of the most cultivated species worldwide. Antibiotics are usually used in catfish farming as therapeutic and prophylactic agents. In the USA, only oxytetracycline, a combination of sulfadimethoxine and ormetoprim, and florfenicol are approved by the Food Drug Administration for specific fish species (e.g., catfish and salmonids) and their specific diseases. Misuse of antibiotics as prophylactic agents in disease prevention, however, is common and contributes in the development of antibiotic resistance. Various studies had reported on antibiotic residues and/or resistance in farmed species, feral fish, water column, sediments, and, in a lesser content, among farm workers. Ninety percent of the world aquaculture production is carried out in developing countries, which lack regulations and enforcement on the use of antibiotics. Hence, efforts are needed to promote the development and enforcement of such a regulatory structure. Alternatives to antibiotics such as antibacterial vaccines, bacteriophages and their lysins, and probiotics have been applied to curtail the increasing emergence of antibiotic-resistant bacteria due to the imprudent application of antibiotics in aquaculture.

Pleuromutilins: Potent Drugs for Resistant Bugs-Mode of Action and Resistance

Pleuromutilins are antibiotics that selectively inhibit bacterial translation and are semisynthetic derivatives of the naturally occurring tricyclic diterpenoid pleuromutilin, which received its name from the pleuromutilin-producing fungus Pleurotus mutilus Tiamulin and valnemulin are two established derivatives in veterinary medicine for oral and intramuscular administration. As these early pleuromutilin drugs were developed at a time when companies focused on major antibacterial classes, such as the β-lactams, and resistance was not regarded as an issue, interest in antibiotic research including pleuromutilins was limited. Over the last decade or so, there has been a resurgence in interest to develop this class for human use. This has resulted in a topical derivative, retapamulin, and additional derivatives in clinical development. The most advanced compound is lefamulin, which is in late-stage development for the intravenous and oral treatment of community-acquired bacterial pneumonia and acute bacterial skin infections. Overall, pleuromutilins and, in particular, lefamulin are characterized by potent activity against Gram-positive and fastidious Gram-negative pathogens as well as against mycoplasmas and intracellular organisms, such as Chlamydia spp. and Legionella pneumophila Pleuromutilins are unaffected by resistance to other major antibiotic classes, such as macrolides, fluoroquinolones, tetracyclines, β-lactam antibiotics, and others. Furthermore, pleuromutilins display very low spontaneous mutation frequencies and slow, stepwise resistance development at sub-MIC in vitro. The potential for resistance development in clinic is predicted to be slow as confirmed by extremely low resistance rates to this class despite the use of pleuromutilins in veterinary medicine for >30 years. Although rare, resistant strains have been identified in human- and livestock-associated environments and as with any antibiotic class, require close monitoring as well as prudent use in veterinary medicine. This review focuses on the structural characteristics, mode of action, antibacterial activity, and resistance development of this potent and novel antibacterial class for systemic use in humans.

Diversity of Staphylococcus aureus Isolates in European Wildlife

Staphylococcus aureus is a well-known colonizer and cause of infection among animals and it has been described from numerous domestic and wild animal species. The aim of the present study was to investigate the molecular epidemiology of S. aureus in a convenience sample of European wildlife and to review what previously has been observed in the subject field. 124 S. aureus isolates were collected from wildlife in Germany, Austria and Sweden; they were characterized by DNA microarray hybridization and, for isolates with novel hybridization patterns, by multilocus sequence typing (MLST). The isolates were assigned to 29 clonal complexes and singleton sequence types (CC1, CC5, CC6, CC7, CC8, CC9, CC12, CC15, CC22, CC25, CC30, CC49, CC59, CC88, CC97, CC130, CC133, CC398, ST425, CC599, CC692, CC707, ST890, CC1956, ST2425, CC2671, ST2691, CC2767 and ST2963), some of which (ST2425, ST2691, ST2963) were not described previously. Resistance rates in wildlife strains were rather low and mecA-MRSA isolates were rare (n = 6). mecC-MRSA (n = 8) were identified from a fox, a fallow deer, hares and hedgehogs. The common cattle-associated lineages CC479 and CC705 were not detected in wildlife in the present study while, in contrast, a third common cattle lineage, CC97, was found to be common among cervids. No Staphylococcus argenteus or Staphylococcus schweitzeri-like isolates were found. Systematic studies are required to monitor the possible transmission of human- and livestock-associated S. aureus/MRSA to wildlife and vice versa as well as the possible transmission, by unprotected contact to animals. The prevalence of S. aureus/MRSA in wildlife as well as its population structures in different wildlife host species warrants further investigation.

Occurrence of cfr-mediated multiresistance in staphylococci from veal calves and pigs, from humans at the corresponding farms, and from veterinarians and their family members

This study reports on the emergence of linezolid-resistant coagulase-negative staphylococci (CoNS) containing the multiresistance gene cfr in veal calves and pigs, as well as in humans exposed to these animals. CoNS (Staphylococcus auricularis, Staphylococcus cohnii, Staphylococcus lentus, Staphylococcus kloosii, Staphylococcus sciuri, Staphylococcus simulans), but not Staphylococcus aureus, carrying the gene cfr were detected in samples of 12 out of 52 calves at three farms which had a history of florfenicol use. Nasal swabs from 10 humans living on these farms were negative for cfr-carrying staphylococci. Nasal swabs taken from 142 calves at 16 farms in the same area that did not use florfenicol were also negative for cfr-carrying staphylococci. 14 cfr-carrying CoNS (S. kloosii, S. saprophyticus, S. simulans) were detected in three of eight conventional pig farms investigated. One of 12 humans living on these farms harboured a cfr-carrying S. cohnii. Among the nasal swabs taken from 169 veterinarians from all over Germany, four (2.3%) were positive for cfr-carrying CoNS (three S. epidermidis, one S. saprophyticus), and three (1.1%) of 263 contact persons of this group also harboured cfr-carrying CoNS (one S. epidermidis, two S. saprophyticus). In vitro conjugation of cfr by filter mating to S. aureus 8325-4 was possible for 10 of 34CoNS and the cfr gene was associated with plasmids of 38-40kb. Moreover, a total of 363 humans of a German municipal community were investigated for nasal carriage of cfr-carrying staphylococci to get an idea whether such isolates are disseminated as nasal colonizers in non-hospitalized humans in the community, were all negative.

Resistome diversity in cattle and the environment decreases during beef production

Antimicrobial resistant determinants (ARDs) can be transmitted from livestock systems through meat products or environmental effluents. The public health risk posed by these two routes is not well understood, particularly in non-pathogenic bacteria. We collected pooled samples from 8 groups of 1741 commercial cattle as they moved through the process of beef production from feedlot entry through slaughter. We recorded antimicrobial drug exposures and interrogated the resistome at points in production when management procedures could potentially influence ARD abundance and/or transmission. Over 300 unique ARDs were identified. Resistome diversity decreased while cattle were in the feedlot, indicating selective pressure. ARDs were not identified in beef products, suggesting that slaughter interventions may reduce the risk of transmission of ARDs to beef consumers. This report highlights the utility and limitations of metagenomics for assessing public health risks regarding antimicrobial resistance, and demonstrates that environmental pathways may represent a greater risk than the food supply.

Genome Sequence of a Unique t2247-ST692-III Livestock-Associated Methicillin-Resistant Staphylococcus aureus Strain from Chicken Carcass

We report the draft genome sequence of a novel livestock-associated t2247-ST692-III methicillin-resistant Staphylococcus aureus strain designated K12S0375, which was isolated from a chicken carcass in South Korea. The K12S0375 strain contains uncommon genes, including antimicrobial resistance genes (tetL and tetS) and leukotoxin (lukED), and the genomic distance indicates a single lineage in a genome-based phylogenetic tree compared with 459 S. aureus genome sequences. This genome sequence will contribute to understanding epidemiological and genomic features of the ST692 lineage, including antimicrobial resistance and virulence genes.