The prevalence and influencing factors of methicillin-resistant Staphylococcus aureus carriage in people in contact with livestock: A systematic review

Comparative Evaluation of the Antibiotic Resistance Profile of Staphylococcus aureus Isolated From Breeders and Livestock

Objectives

Animals are a potential source of Methicillin Resistant Staphylococcus aureus. This study evaluated the antibiotics susceptibility pattern of S. aureus isolates from breeders and livestock.

Methods

S. aureus strains were isolated from 180 livestock and 48 livestock farmers and identified using standard methods. Antibiotic susceptibility profiles and MRSA status were determined via disk diffusion susceptibility method.

Results

Among farm workers, 37.5% were colonized by S. aureus, with pig farm workers exhibiting the highest prevalence (56.2%), cattle herders (37.5%), and goat farm workers (18.7%). MRSA carriage among livestock isolates was 41.3%, while, six isolates from the poultry farm worker were MRSA, representing a carriage of 33.3%. Drug susceptibility profiles revealed differential patterns between isolates from breeders and animals. Gentamicin and levofloxacin demonstrated higher efficacy against farm worker isolates compared to animal isolates. Resistance to cefuroxime was higher among animal isolates (84.1%) as against the 66.7% for the breeders.

Conclusion

The identification of multidrug-resistant S. aureus strains underscores the risk posed to humans in contact with animals. These findings stress the importance of monitoring and managing MRSA transmission between animals and humans.

Evolution of polyamine resistance in Staphylococcus aureus through modulation of potassium transport

Microbes must adapt to diverse biotic and abiotic factors encountered in host environments. Polyamines are an abundant class of aliphatic molecules that play essential roles in fundamental cellular processes across the tree of life. Surprisingly, the bacterial pathogen Staphylococcus aureus is highly sensitive to polyamines encountered during infection, and acquisition of a polyamine resistance locus has been implicated in spread of the prominent USA300 methicillin-resistant S. aureus lineage. At present, alternative pathways of polyamine resistance in staphylococci are largely unknown. Here we applied experimental evolution to identify novel mechanisms and consequences of S. aureus adaption when exposed to increasing concentrations of the polyamine spermine. Evolved populations of S. aureus exhibited striking evidence of parallel adaptation, accumulating independent mutations in the potassium transporter genes ktrA and ktrD. Mutations in either ktrA or ktrD are sufficient to confer polyamine resistance and function in an additive manner. Moreover, we find that ktr mutations provide increased resistance to multiple classes of unrelated cationic antibiotics, suggesting a common mechanism of resistance. Consistent with this hypothesis, ktr mutants exhibit alterations in cell surface charge indicative of reduced affinity and uptake of cationic molecules. Finally, we observe that laboratory-evolved ktr mutations are also present in diverse natural S. aureus isolates, suggesting these mutations may contribute to antimicrobial resistance during human infections. Collectively this study identifies a new role for potassium transport in S. aureus polyamine resistance with consequences for susceptibility to both host-derived and clinically-used antimicrobials.

Cross-sectional analysis of risk factors associated with Mugil cephalus in retail fish markets concerning methicillin-resistant Staphylococcus aureus and Aeromonas hydrophila

Introduction

Aeromonas hydrophila and methicillin-resistant Staphylococcus aureus (MRSA) are potent bacterial pathogens posing major hazards to human health via consuming fish harboring these pathogens or by cross-contamination beyond the contaminated environment. The aim of this study was to determine risk variables associated with the presence of certain pathogenic bacteria from Mugil cephalus fish in retail markets in Egypt. The virulence genes of A. hydrophila and S. aureus were also studied. Furthermore, the antibiotic sensitivity and multidrug resistance of the microorganisms were evaluated.

Methods

In a cross-sectional investigation, 370 samples were collected from mullet skin and muscle samples, washing water, fish handlers, knives, and chopping boards. Furthermore, fish handlers' public health implications were assessed via their response to a descriptive questionnaire.

Results

S. aureus and Aeromonas species dominated the investigated samples with percentages of 26.76% and 30.81%, respectively. Furthermore, A. hydrophila and MRSA were the predominant recovered bacterial pathogens among washing water and knives (53.85% and 46.66%, respectively). The virulence markers aerA and hlyA were found in 90.7% and 46.5% of A. hydrophila isolates, respectively. Moreover, the virulence genes nuc and mec were prevalent in 80% and 60% of S. aureus isolates, respectively. Antimicrobial susceptibility results revealed that all A. hydrophila isolates were resistant to amoxicillin and all MRSA isolates were resistant to amoxicillin and ampicillin. Remarkably, multiple drug resistance (MDR) patterns were detected in high proportions in A. hydrophila (88.37%) and MRSA (100%) isolates. The prevalence of Aeromonas spp. and S. aureus had a positive significant correlation with the frequency of handwashing and use of sanitizer in cleaning of instruments. MRSA showed the highest significant prevalence rate in the oldest age category.

Conclusion

The pathogenic bacteria recovered in this study were virulent and had a significant correlation with risk factors associated with improper fish handling. Furthermore, a high frequency of MDR was detected in these pathogenic bacteria, posing a significant risk to food safety and public health.

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.

Effect of cattle farm exposure on oropharyngeal and gut microbial communities and antibiotic resistance genes in workers

Livestock farms are recognized as the main sources of antibiotic resistance genes (ARGs) and antibiotic-resistant bacteria (ARB) with potential implications for human health. In this study, we systematically analyzed microbiome composition, distribution of ARGs and mobile genetic elements (MGEs) in the oropharynx and gut of workers in cattle farms and surrounding villagers, cattle feces and farm air, and the relationship of microbial communities among farm air, cattle feces and farmworkers (oropharynx and gut). Exposure to the farm environment may have remodeled farmworkers' oropharynx and gut microbiota, with reduced microbial diversity (P < 0.05) and enrichment of some opportunistic pathogenic bacteria like Shigella, Streptococcus, and Neisseria in the oropharynx. Meanwhile, compared with villagers, ARG abundance in oropharynx of farmworkers increased significantly (P < 0.05), but, no significant difference in gut (P > 0.05). Microbial composition and ARG profile in farmworkers might be influenced by working time and work type, ARG abundance in farmworkers' gut was positively correlated with working time (P < 0.01), and higher ARG abundance was found in the oropharynx of drovers. The network analysis revealed that 4 MGEs (tnpA-01, tnpA-04, Tp614, and IS613), 5 phyla (e.g. Bacteroidetes, Fusobacteria, and TM7), and 6 genera were significantly associated with 37 ARGs (ρ > 0.6, P < 0.01). Overall, our results indicated that farm exposure may have affected the microbial composition and increased ARG abundance of farmworkers. Transmission of some ARGs may have occurred among the environment, animals and humans via host bacteria, which might pose a potential threat to human health.

Cross-species transmission risk of livestock-associated MRSA: A systematic review and Bayesian meta-analysis of global data

Although increasing studies have indicated a strong relationship between livestock exposure and methicillin-resistant Staphylococcus aureus (MRSA) carriage in humans, the risk magnitude of cross-species transmission of livestock-associated MRSA (LA-MRSA) is still unclear. This meta-analysis aimed to evaluate the potential effect of livestock exposure on LA-MRSA (including CC398/CC9, scn-negative, and tetracycline-resistant isolates) transmission. The summary estimates were pooled by random-effects models using the DerSimonian & Laird (DL) method and the Bayesian method. Twenty-two studies were included in this meta-analysis. Livestock-exposed people demonstrated a significantly higher rate of livestock-associated S. aureus (LA-SA) carriage than non-exposed people (Bayesian estimates: OR = 5.23 for CC398/CC9; OR = 2.35 for scn-negative isolates; OR = 3.86 for tetracycline-resistant isolates). Similarly, there was a greater positive association between livestock exposure and LA-MRSA carriage in humans ((Bayesian estimates: OR = 7.64 for CC398/CC9; OR = 7.54 for scn-negative isolates; OR = 9.89 for tetracycline-resistant isolates), indicating that livestock exposure increases the risk of LA-MRSA carriage in humans. These findings provide evidence for revealing the high risk of cross-species LA-MRSA transmission by livestock exposure.

Pet husbandry as a risk factor for colonization or infection with MDR organisms: a systematic meta-analysis

BACKGROUND

MDR organisms (MDROs) pose a relevant risk for patients in modern healthcare. Although ownership of pet animals is common and owners and pets commonly live in close contact, it is still unclear whether pet ownership may be considered as a risk factor for MDRO acquisition prior to hospitalization.

METHODS

We performed three separate meta-analyses in accordance with the PRISMA guidelines, assessing contact to pets as a risk factor for acquisition of MRSA, VRE and MDR Gram-negatives [namely third-generation cephalosporin-resistant Enterobacterales (3GCRE) and carbapenem-resistant Enterobacterales (CRE)].

RESULTS

We calculated an increased risk of MRSA carriage for dog owners [risk ratio (RR) 2.28, 95% CI 1.47-3.56]. Meta-analysis did not show a significantly higher risk for 3GCRE colonization among owners of different pet species compared with non-pet owners (RR 1.18, 95% CI 0.83-1.68 for pet owners in general, RR 0.88, 95% CI 0.56-1.40 for dog owners, RR 1.16, 95% CI 0.58-2.34 for cat owners, RR 1.34, 95% CI 0.43-4.18 for rodent owners, RR 0.91, 95% CI 0.38-2.18 for bird owners, and RR 2.34, 95% CI 0.33-16.63 for lizard/frog owners). For VRE, there were insufficient data to perform a meta-analysis.

CONCLUSIONS

Our analyses suggest contact to pet animals is a risk factor for MRSA, but not for 3GCRE/CRE acquisition. Evaluation of the underlying literature suggested a possible role of pet animals as: (i) vectors for the transmission of MDROs between livestock and humans; as well as (ii) a reservoir for MDROs. Pets, therefore, may promote transmission and reinfection of humans.

A One Health approach to assessing occupational exposure to antimicrobial resistance in Thailand: The FarmResist project

This Southeast Asia-Europe research project will use a One Health approach to identify the major parameters responsible for the presence of animal-associated antimicrobial resistant bacteria in animal production facilities in Thailand and the risk of their transmission from animals to humans. We will focus on traditional, small, extensive pig and poultry farms where information on antibiotic use is scarce and animals live in close contact with humans. This cross-sectional study will be based on the epidemiological analysis of the antimicrobial resistance (AMR) present in fecal samples from animals and humans. Extended spectrum beta-lactamase producing Enterobacteriaceae (ESBL-E) and Enterobacteriaceae resistant to colistin will be actively searched in the feces of farm animals (pigs and poultry), small wild rodents and farmers. Phenotypic (selective plating) and genotypic (multilocus seuquence typing and sequencing) methods will be used for the detection of AMR, the identification of antibiotic resistance genes (ARGs) and the characterization of strains carrying resistance genes. Questionnaires will be administered to investigate the effects of antibiotic use, farm characteristics and biosecurity measures on the occurrence of AMR in animals. Subsequently, the fecal carriage of AMR and ARGs in farmers will be compared to a control population with no occupational contacts with animals, thus enabling an estimation of the risk of transmission of AMR/ARGs from animals to farmers.

Chemical disinfection in healthcare settings: critical aspects for the development of global strategies

Chemical disinfection is an indispensable means of preventing infection. This holds true for healthcare settings, but also for all other settings where transmission of pathogens poses a potential health risk to humans and/or animals. Research on how to ensure effectiveness of disinfectants and the process of disinfection, as well as on when, how and where to implement disinfection precautions is an ongoing challenge requiring an interdisciplinary team effort. The valuable resources of active substances used for disinfection must be used wisely and their interaction with the target organisms and the environment should be evaluated and monitored closely, if we are to reliable reap the benefits of disinfection in future generations. In view of the global threat of communicable diseases and emerging and re-emerging pathogens and multidrug-resistant pathogens, the relevance of chemical disinfection is continually increasing. Although this consensus paper pinpoints crucial aspects for strategies of chemical disinfection in terms of the properties of disinfectant agents and disinfection practices in a particularly vulnerable group and setting, i.e., patients in healthcare settings, it takes a comprehensive, holistic approach to do justice to the complexity of the topic of disinfection.

Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) colonisation and infection among livestock workers and veterinarians: a systematic review and meta-analysis

OBJECTIVES

Methicillin-resistant Staphylococcus aureus (MRSA) is an increasing public health concern worldwide. The objective of this study was to calculate a summary odds ratio (OR) of livestock-associated MRSA colonisation and infection in humans, and to determine specific risk factors in livestock production contributing to MRSA colonisation.

METHODS

We screened PubMed and Embase for studies published from 2005 to 2019 inclusive, reporting livestock-associated (LA)-MRSA colonisation and infection among livestock workers/veterinarians, their families, and community members not regularly exposed to livestock. The primary outcome of interest was the OR of LA-MRSA colonisation comparing exposed and control groups. Quality was assessed according to the Newcastle-Ottawa quality assessment scale. A meta-analysis using a random-effects model was conducted to calculate a pooled OR. The heterogeneity in the meta-analysis was assessed using the I² method, and publication bias was evaluated using funnel plots.

RESULTS

A total of 3490 studies were identified by the search, with 37 studies including 53 matched exposed-control groups and 14 038 participants eligible for the meta-analysis. The pooled OR for LA-MRSA among livestock workers and veterinarians is 9.80 (95% CI 6.89 to 13.95; p=0.000; I2 =73.4), with no significant publication bias (Egger's p=0.66). The OR for swine workers was highest at 15.41 (95% CI 9.24 to 25.69), followed by cattle workers (11.62, 95% CI 4.60 to 29.36), veterinarians (7.63, 95% CI 3.10 to 18.74), horse workers (7.45, 95% CI 2.39 to 23.25), livestock workers (5.86, 95% CI 1.14 to 30.16), poultry workers (5.70, 95% CI 1.70 19.11), and industrial slaughterhouse workers (4.69, 95% CI 1.10 to 20.0).

CONCLUSIONS

Livestock workers, particularly swine farmers, are at significantly higher risk for LA-MRSA colonisation and subsequent infection. These results support the need for preventive practices to reduce LA-MRSA risk among those who handle and treat livestock.

TRIAL REGISTRATION NUMBER

CRD42019120403.

Risk of Antibiotic-Resistant Staphylococcus aureus Dispersion from Hog Farms: A Critical Review

The World Health Organization has declared antibiotic resistance "one of the biggest threats to global health." Mounting evidence suggests that antibiotic use in industrial-scale hog farming is contributing to the spread of antibiotic-resistant Staphylococcus aureus. To capture available evidence on these risks, we searched peer-reviewed studies published before June 2017 and conducted a meta-analysis of these studies' estimates of the prevalence of swine-associated, antibiotic-resistant S. aureus in animals, humans, and the environment. The 166 relevant studies revealed consistent evidence of livestock-associated methicillin-resistant S. aureus (MRSA) in hog herds (55.3%) raised with antibiotics. MRSA prevalence was also substantial in slaughterhouse pigs (30.4%), industrial hog operation workers (24.4%), and veterinarians (16.8%). The prevalence of swine-associated, multidrug-resistant S. aureus (MDRSA)-with resistance to three or more antibiotics-is not as well documented. Nonetheless, sufficient studies were available to estimate MDRSA pooled prevalence in conventional hog operation workers (15.0%), workers' household members (13.0%), and community members (5.37%). Evidence also suggests that antibiotic-resistant S. aureus can be present in air, soil, water, and household surface samples gathered in or near high-intensity hog operations. An important caveat is that prevalence estimates for humans reflect colonization, not active infection, and the health risks of colonization remain poorly understood. In addition, these pooled results may not represent risks in specific locations, due to wide geographic variation. Nonetheless, these results underscore the need for additional preventive action to stem the spread of antibiotic-resistant pathogens from livestock operations and a streamlined reporting system to track this risk.

Prevalence of methicillin-resistant Staphylococcus aureus in healthy Chinese population: A system review and meta-analysis

Objective

To comprehensively determine the prevalence of MRSA in healthy Chinese population, the influencing factors of MRSA colonization and its antibiotic resistance.

Methods

Articles that studied prevalence or influencing factors of MRSA carriage in healthy Chinese population were retrieved from PubMed, Ovid database, three Chinese electronic databases. The pooled prevalence of MRSA, its antibiotic resistance and influencing factors were analyzed by STATA12.0.

Results

37 studies were included. The pooled prevalence of MRSA was 21.2% (95% CI: 18.5%-23.9%), and the prevalence of S.aureus was 15% (95% CI: 10%-19%), with a significant heterogeneity (MRSA: I² = 97.6%, P<0.001; S.aureus: I² = 98.4%, P < 0.001). In subgroup analysis, the pooled prevalence of MRSA was 28% (95%CI: 10%-51%) for Livestock-related workers, 18% (95%CI: 11%-26%) for children, 20% (95%CI: 12%-29%) for healthcare workers, 7% (95%CI: 3%-13%) for community residents. The prevalence of MRSA in studies with oxacillin disk diffusion method (28%, 95%CI: 21%-35%) seemed higher than that with the mecA gene method(12%, 95%CI: 7%-19%). MRSA in studies conducted in Taiwan was more common than in Mainland China and Hong Kong. Similar results were found in meta-regression. Influencing factors for MRSA colonization were noted in seven eligible studies, they included younger age (OR: 3.54, 95% CI: 2.38–5.26; OR: 2.24, 95% CI: 1.73–2.9), attending day care centers (DCCs) (OR: 1.95, 95% CI: 1.4–2.72; OR: 1.53, 95% CI: 1.2–1.95), flu vaccination (OR:1.73, 95% CI: 1.28–2.35), using antibiotics within the past year (OR: 2.05, 95% CI:1.35–3.11), residing in northern Taiwan (OR: 1.45, 95% CI: 1.19–1.77), regular visits to health care facility (OR: 23.83, 95% CI: 2.72–209.01), household member working in health care facility (OR: 8.98, 95% CI:1.4–55.63), and contact with livestock (OR: 6.31, 95% CI: 3.44–11.57). Moreover, MRSA was found to be highly resistant to penicillin, ampicillin, erythromycin, and clindamycin, with a pooled resistance ratio of 100, 93, 88, and 75%, respectively. However, no resistance were noted to vancomycin.

Conclusion

The pooled prevalence of MRSA was considerably high in health Chinese population. Additionally, these strains showed extreme resistance to penicillin, ampicillin, erythromycin and clindamycin. Public MRSA protection measures and the surveillance of MRSA should be strengthened to reduce the spread of MRSA among hospitals, communities, and livestock.

Prevalence of Livestock-Associated Methicillin-Resistant Staphylococcus Aureus (LA-MRSA) Among Farm and Slaughterhouse Workers in Italy

OBJECTIVE

We measured the prevalence of livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) in swine livestock workers, examined LA-MRSA resistance profile, and associated carriage with the working activities.

METHODS

Information was collected on demographics and occupational history. Swabs were collected and tested for the isolation of S. aureus, examined for antimicrobial susceptibility, and all MRSA underwent ST398qPCR assay.

RESULTS

LA-MRSA was isolated in 7.3% of the 396 enrolled workers. LA-MRSA colonization was more likely in farmers than in slaughterhouse workers (Fisher exact P = 0.001). Carriage was associated with herd size, being less frequent in small/medium farms (odds ratio = 0.20; 95% confidence interval = 0.07 to 0.53), and with the number of working days per week (OR = 2.11; 95% confidence interval = 1.07 to 4.19).

CONCLUSIONS

LA-MRSA carriage is strongly animal-exposure related, and educational intervention informing about the risks related to the activity with livestock is needed.

Relationship between livestock exposure and methicillin-resistant Staphylococcus aureus carriage in humans: A systematic review and dose-response meta-analysis

Although previous studies have suggested an association between livestock exposure and the risk of methicillin-resistant Staphylococcus aureus (MRSA) carriage in humans, it remains unclear whether there is a dose-response relationship. The aim of this study was to evaluate the relationship between livestock exposure and MRSA carriage. Pooled risk estimates were calculated using fixed-effects or random-effects models based on homogeneity analysis. A dose-response meta-analysis based on linear and non-linear regression was performed to explore the frequency-risk relationship between livestock exposure and MRSA carriage. Subgroup analyses were conducted to explore sources of heterogeneity among eligible studies. A total of 25 studies were included in the meta-analysis. Livestock exposure was significantly associated with an increased risk of MRSA carriage [odds ratio (OR) = 7.03, 95% confidence interval 4.29-11.52], and similar positive associations were observed for pig (OR = 11.41), poultry (OR = 6.20) and cattle (OR = 5.66) exposure. Regarding studies on ordinal and continuous frequency of livestock exposure, a monotonically increasing frequency-risk relationship between livestock (or pig) exposure and MRSA carriage was consistently observed. This study found a monotonically increasing frequency-risk relationship between livestock exposure and MRSA carriage, which provides evidence for potential livestock-to-human transmission of MRSA.

Prevalence of methicillin-resistant Staphylococcus aureus (MRSA) carriage and pattern of antibiotic resistance among sheep farmers from Southern Italy

PURPOSE

We conducted a cross-sectional study to measure the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) colonization, with a particular focus on livestock associated (LA)-MRSA in farmers working in contact with livestock (sheep) in one Italian region. Furthermore, we have assessed the antimicrobial resistance pattern of isolates and the association of carriage with specific characteristic of farms and working tasks.

PATIENTS AND METHODS

Demographic data, occupational history, and contact with animals information was collected. Nasal and oropharyngeal swabs were collected and all samples were tested for the isolation and identification of S. aureus. Isolates were examined for antimicrobial susceptibility and all MRSA strains underwent molecular analyses through multiple-locus variable number of tandem repeat analysis (MLVA).

RESULTS

A total of 115 sheep farms and 275 sheep farmers were enrolled. MRSA colonized workers were found in three farms; S. aureus was isolated in 97 workers (35.5%), whereas MRSA was isolated in 3 (1.1%) workers. All MRSA isolates were classified as multidrug resistant. Two of the MRSA isolates were resistant to quinupristin/dalfopristin (QDA), mupirocin, erythromycin, and tetracycline. Among methicillin-susceptible S. aureus (MSSA), 32 (34%) were resistant to tetracycline, 31 (33%) to erythromycin, 26 (27.6%) to QDA, and 22 (23.4%) to linezolid and clindamycin. One MRSA belonged to MLVA complex (MC) 001, found to colonize both humans and animals.

CONCLUSION

The picture of MRSA transmission among sheep farmers does not seem to be critical, although there is the need to improve adequate control measures to prevent and minimize any biological risk in sheep farms for both animal and human health. Specific monitoring/surveillance programs would help in better understanding the epidemiology of resistant strains.

MRSA in swine, farmers and abattoir workers in Southern Italy

Methicillin-resistant Staphylococcus aureus (MRSA) is an important medical issue, since it causes serious and sometimes fatal infections in humans. Intensively reared swine may serve as reservoirs for MRSA that can infect swine workers, and also consumers (via contaminated meat). In this study, MRSA strains were isolated from 55 of the 85 (64.7%) intensive pig farms surveyed, and prevalence was greater on pig fattening farms than on breeding farms. In addition, we included in the study 63 foreign pigs imported for slaughter. Overall, the prevalence of MRSA in the 418 sampled swine was 59.1%; 12 genotypes were identified among the isolates; ST398 (96.4%) was most prevalent, followed by ST97 (2%), ST9 (0.8%) and ST1 (0.8%). MRSA isolates were also detected in 26 (17.3%) of the 150 operators included in the study; the genotypes detected were ST398 (85%), ST9 (7.6%), ST5 (3.8%) and ST1 (3.8%). All the strains were pvl negative and pia positive. Both swine and human strains displayed a multi-resistance pattern, and almost all were resistant to tetracycline. The results obtained in this study confirm the high prevalence of MRSA in swine reared and slaughtered in Italy, and underline the public health risk linked to the spread of antimicrobial-resistant Staphylococcus aureus among intensively reared pigs.

High Genetic Similarity of MRSA ST88 Isolated From Pigs and Humans in Kogi State, Nigeria

We determined the prevalence and genetic characteristics of methicillin-resistant Staphylococcus aureus (MRSA) isolated from pigs and humans between September 2013 and February 2015 in Kogi State, a central region in Nigeria. A total of 680 nasal swabs were collected and analyzed from pigs (n = 425) and “pig-contact” humans (n = 55) on 35 farms, and “non-pig-contact” humans (n = 200). MRSA was recovered from 20 (4.7%) pigs on 12 farms and 18 (7.0%) humans. Six (2.4%) of the human isolates were recovered from “pig-contact” humans, of which only three work on farms also harboring MRSA positive pigs. All 38 MRSA were resistant to β-lactams only, belonged to spa type t1603, sequence type (ST) 88, and mecA was associated with a SCCmec IVa element. Four isolates from a pig, a pig-contact human from the same farm, a pig-contact human from a pig farm in a different district, and a non-pig-contact human were subjected to whole genome sequencing (WGS). Core genome SNP analysis revealed high genetic similarity between strains (3–11 SNP differences), despite the temporal (2 year gap) and geographic (165 km) differences between isolates. Furthermore, these Nigerian isolates form a distinct clade when compared to other African MRSA ST88 isolates. All but one porcine strain was positive for scn suggesting a possible human origin and that pigs were either transiently contaminated by humans or result of a very recent human-to-pig transmission event. To our knowledge, this is the first report of genetically confirmed MRSA in pigs in Nigeria, which appear to be a typical CA-MRSA clone present in the human population.

Emergence of highly prevalent CA-MRSA ST93 as an occupational risk in people working on a pig farm in Australia

BACKGROUND

The occurrence of livestock-associated (LA) MRSA (ST398) in pig herds has emerged as a threat to occupational safety in many parts of the world. Recently, an outbreak of skin lesions due to MRSA occurred in workers at a pig farm in regional Australia and both the humans and pigs were shown to have a high prevalence of carriage of either the human-strain ST93 or porcine strain ST398. This study closely scrutinises this outbreak to determine factors associated with MRSA carriage amongst the workers.

METHODS

Information on potential risk factors was collected from employees by means of a questionnaire. The carriage status of MRSA by workers was assessed by nasal swabs processed using standard laboratory techniques with confirmed isolates subjected to sequence typing. Associations between MRSA carriage in workers and their questionnaire responses were investigated using univariable and multivariable logistic regression.

RESULTS

Nasal carriage of MRSA was identified in 60% (31/52) of participants. Workers having contact with pigs had 24 times the odds of MRSA carriage compared to workers with no direct contact (OR 23.6; CI 5.2-172.8). In addition, the probability of MRSA carriage in workers was significantly (P < 0.001) associated with the number of hours in contact with pigs and each hour of contact-time per day increased the risk of MRSA carriage by 1.44 times (CI 1.14-1.96). These associations were significant (P < 0.001) for both strains, ST398 and ST93, present on this farm. Using a multivariable logistic regression model that incorporated human exposure to five different pig age groups (dry sows, farrowing, weaner, grower, and finisher) as fixed effects, a significant (P = 0.027) increased odds of MRSA carriage was found for persons working with farrowing sows compared with those who did not (OR 6.39, CI 1.23-39.36).

CONCLUSIONS

This study shows that workers in close contact with pigs on a pig farm where MRSA is present had a higher risk of MRSA carriage as the number of hours of direct contact with pigs increased. Since we have detected a significant association for the human-derived CA-MRSA ST93, similar to the pig-adapted LA-MRSA ST398, we consider ST93 as a potential occupational risk for piggery workers. The risk of MRSA carriage is greatest when working with the farrowing group; therefore, an emphasis is required on personal protective equipment while working in the farrowing house. The study has ramifications for the conduct of surveillance for MRSA in people exposed to pigs.

Veterinary Students' Knowledge and Perceptions About Antimicrobial Stewardship and Biosecurity-A National Survey

A better understanding of veterinary students’ perceptions, attitudes, and knowledge about antimicrobial stewardship and biosecurity could facilitate more effective education of future veterinarians about these important issues. A multicenter cross-sectional study was performed by administering a questionnaire to veterinary students expected to graduate in 2017 or 2018 in all Australian veterinary schools. Four hundred and seventy-six of 1246 students (38%) completed the survey. Many students were unaware of the high importance of some veterinary drugs to human medicine, specifically enrofloxacin and cefovecin (59% and 47% of responses, respectively). Fewer than 10% of students would use appropriate personal protective equipment in scenarios suggestive of Q fever or psittacosis. Students expected to graduate in 2018 were more likely to select culture and susceptibility testing in companion animal cases (OR 1.89, 95% CI 1.33–2.69, p < 0.001), and were more likely to appropriately avoid antimicrobials in large animal cases (OR 1.75, 95% CI 1.26–2.44, p = 0.001) than those expected to graduate in 2017. However, 2018 graduates were less likely to correctly identify the importance rating of veterinary antimicrobials for human health (OR 0.48, 95% CI 0.34–0.67, p < 0.001) than 2017 graduates. Students reported having a good knowledge of antimicrobial resistance, and combating resistance, but only 34% thought pharmacology teaching was adequate and only 20% said that teaching in lectures matched clinical teaching. Efforts need to be made to harmonize preclinical and clinical teaching, and greater emphasis is needed on appropriate biosecurity and antimicrobial stewardship.

Cross-sectional study of antimicrobials used for surgical prophylaxis by bovine veterinary practitioners in Australia

Antimicrobials are widely used in veterinary practices, but there has been no investigation of antimicrobial classes used or the appropriateness of their use in bovine practice. This study investigated antimicrobial use for surgical prophylaxis in bovine practice in Australia. A cross-sectional study of veterinarian antimicrobial usage patterns was conducted using an online questionnaire. Information solicited included respondent's details, the frequency with which antimicrobials were used for specific surgical conditions (including the dose, timing and duration of therapy) and details of practice antimicrobial use policies and sources of information about antimicrobials. In total, 212 members of the Australian veterinary profession working in bovine practice completed the survey. Antimicrobials were always or frequently used by more than 75 per cent of respondents in all scenarios. Generally, antimicrobial drug choice was appropriate for the reported surgical conditions. Procaine penicillin and oxytetracycline accounted for 93 per cent of use. However, there was a wide range of doses used, with underdosing and inappropriate timing of administration being common reasons for inappropriate prophylactic treatment. There was very low use of critically important antimicrobials (3.3 per cent of antimicrobials reported). Antimicrobial use guidelines need to be developed and promoted to improve the responsible use of antimicrobials in bovine practice.

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.

Antimicrobials used for surgical prophylaxis by equine veterinary practitioners in Australia

BACKGROUND

Antimicrobials are widely used in Australian veterinary practices, but no investigation into the classes of antimicrobials used, or the appropriateness of use in horses, has been conducted.

OBJECTIVES

The aim of the study was to describe antimicrobial use for surgical prophylaxis in equine practice in Australia.

STUDY DESIGN

Cross-sectional questionnaire survey.

METHODS

An online questionnaire was used to document antimicrobial usage patterns. Information solicited in the questionnaire included demographic details of the respondents, the frequency with which antimicrobials were used for specific surgical conditions (including the dose, timing and duration of therapy) and practice antimicrobial use policies and sources of information about antimicrobials and their uses.

RESULTS

A total of 337 members of the Australian veterinary profession completed the survey. Generally, the choice of antimicrobial was appropriate for the specified equine surgical condition, but the dose and duration of therapy varied greatly. While there was poor optimal compliance with British Equine Veterinary Association guidelines in all scenarios (range 1-15%), except removal of a nonulcerated dermal mass (42%), suboptimal compliance (compliant antimicrobial drug selection but inappropriate timing, dose or duration of therapy) was moderate for all scenarios (range 48-68%), except for an uninfected contaminated wound over the thorax, where both optimal and suboptimal compliance was very poor (1%). Veterinarians practicing at a university hospital had higher odds of compliance than general practice veterinarians (Odds ratio 3.2, 95% CI, 1.1-8.9, P = 0.03).

MAIN LIMITATIONS

Many survey responses were collected at conferences which may introduce selection bias, as veterinarians attending conferences may be more likely to have been exposed to contemporary antimicrobial prescribing recommendations.

CONCLUSIONS

Antimicrobial use guidelines need to be developed and promoted to improve the responsible use of antimicrobials in equine practice in Australia. An emphasis should be placed on antimicrobial therapy for wounds and appropriate dosing for procaine penicillin.

Comparison of Fecal Microbial Composition and Antibiotic Resistance Genes from Swine, Farm Workers and the Surrounding Villagers

The external environment plays a critical role in shaping the structure of the gut microbiome. One potential health threat lies in the release of antibiotic resistant genes (ARGs) from cross-contaminated microbiomes. We focused this study on a comparison of fecal microbial composition and antibiotic resistant genes between farm workers, local villagers and swine. We used a high-throughput next-generation sequencing of 16S rRNA and real-time PCR for these studies. Our results indicated that workers had less species diversity as compared to the local villagers. Moreover, the bacterial communities of the farm workers, the local villagers and swine feces were clearly divided into three groups. The workers had a greater abundance of Proteobacteria as compared to swine and the local villagers. The Clostridiaceae in the workers and swine were more abundant than the local villagers. In addition, there were ARG differences between the farm workers or local villager’s and swine feces. The farm workers and the local villagers had similar relative abundance except for macrolide ARGs. Taken together, these data suggest that the swine farm environment affects the fecal bacterial composition of swine farm workers. However, ARG spread was influenced by factors independent of the swine farm environment.

Methicillin-resistant Staphylococcus aureus not detected in Swedish nucleus and multiplying pig herds

Introduction: Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) has emerged among pigs in many countries. MRSA in the pig population constitute a reservoir with risk for transmission to humans in close contact with pigs. Absence of MRSA in the top of the breeding pyramid would prevent spread to the rest of the pig population. The aim of this study was to investigate the occurrence of MRSA in nucleus and multiplying pig herds in Sweden.

Materials and methods: All nucleus and multiplying pig herds in Sweden present in 2011 (n = 53) and 2014 (n = 39) were sampled for MRSA.

Results and discussion: MRSA was not detected either in 2011 or in 2014. That MRSA was not detected in the top of the breeding pyramid indicates a favourable MRSA situation in the Swedish pig population.

Abbreviations: MRSA: methicillin-resistant Staphylococcus aureus; LA-MRSA: livestock-associated MRSA; CC: clonal complex

Gender differences in rates of carriage and bloodstream infection caused by methicillin-resistant Staphylococcus aureus: are they real, do they matter and why?

There is increasing interest in sexual and gender dimorphism in disease. We reviewed the epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) carriage and bloodstream infection (BSI), which shows a male predominance, and explored some of the possible reasons. Males are more prone to bacterial sepsis, but some studies suggest females may have a poorer prognosis from BSI. Hand-hygiene behavior varies according to gender. Males are less compliant, which in turn may predispose them to higher colonization and infection rates. Female hormones such as estrogen affect the expression of virulence factors in Pseudomonas aeruginosa, and although not studied, this may also apply to S. aureus. Further research is required on the relationship between gender and risk of infection, the reasons for higher MRSA carriage and BSI rates in males, the value of gender-specific infection prevention campaigns, and other factors such as the possible role of contact sports and occupation.