Clinical impact and prevalence of MRSA CC398 and differences between MRSA-TetR and MRSA-TetS in an area of Spain with a high density of pig farming: a prospective cohort study

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.

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

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

Review of pork and pork products as a source for transmission of methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is an opportunistic bacterium that can cause infection in animals and humans. Recently, MRSA from food-producing or farm animals has been identified as livestock-associated MRSA (LA-MRSA). The spread of LA-MRSA is particularly found in pork and pork products because LA-MRSA has been widely known to infect pigs. The most common type of LA-MRSA identified in pork and pork products is the clonal complex LA-MRSA 398 (LA-MRSA CC398). The MRSA strains on the surface of pork carcasses can be spread during the handling and processing of pork and pork products through human hands, cutting tools, and any surface that comes into direct contact with pork. Food infection is the main risk of MRSA in pork and pork products consumed by humans. Antibiotics to treat food infection cases due to MRSA infection include vancomycin and tigecycline. The spread of MRSA in pork and pork products is preventable by appropriately cooking and cooling the pork and pork products at temperatures above 60°C and below 5°C, respectively. It is also necessary to take other preventive measures, such as having a clean meat processing area and disinfecting the equipment used for processing pork and pork products. This review aimed to explain epidemiology, transmission, risk factors, diagnosis, public health consequences, treatment of food poisoning, and preventing the spread of MRSA in pork and pork products.

Transmission routes of antibiotic resistant bacteria: a systematic review

Background

Quantification of acquisition routes of antibiotic resistant bacteria (ARB) is pivotal for understanding transmission dynamics and designing cost-effective interventions. Different methods have been used to quantify the importance of transmission routes, such as relative risks, odds ratios (OR), genomic comparisons and basic reproduction numbers. We systematically reviewed reported estimates on acquisition routes’ contributions of ARB in humans, animals, water and the environment and assessed the methods used to quantify the importance of transmission routes.

Methods

PubMed and EMBASE were searched, resulting in 6054 articles published up until January 1st, 2019. Full text screening was performed on 525 articles and 277 are included.

Results

We extracted 718 estimates with S. aureus (n = 273), E. coli (n = 157) and Enterobacteriaceae (n = 99) being studied most frequently. Most estimates were derived from statistical methods (n = 560), mainly expressed as risks (n = 246) and ORs (n = 239), followed by genetic comparisons (n = 85), modelling (n = 62) and dosage of ARB ingested (n = 17). Transmission routes analysed most frequently were occupational exposure (n = 157), travelling (n = 110) and contacts with carriers (n = 83). Studies were mostly performed in the United States (n = 142), the Netherlands (n = 87) and Germany (n = 60). Comparison of methods was not possible as studies using different methods to estimate the same route were lacking. Due to study heterogeneity not all estimates by the same method could be pooled.

Conclusion

Despite an abundance of published data the relative importance of transmission routes of ARB has not been accurately quantified. Links between exposure and acquisition are often present, but the frequency of exposure is missing, which disables estimation of transmission routes’ importance. To create effective policies reducing ARB, estimates of transmission should be weighed by the frequency of exposure occurrence.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07360-z.

Mycotic Aneurysm of Internal Carotid Artery Secondary to Livestock-associated Methicillin-resistant Staphylococcus Aureus Clonal Complex CC398

The aim of this article is to present a case of mycotic aneurysm of internal carotid artery secondary to livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) treated with resection and common-to-internal carotid artery bypass with autologous vein graft in a male pig farmer. A 69-year-old man, pig farmer, with recent dental extraction was admitted with a right cervical pulsatile mass, dysphonia, pain, leukocytosis and elevated C-reactive protein (CRP). Ultrasonography (US) and computed tomography angiography (CTA) showed a 3.9 × 4.5 cm mycotic aneurysm of right internal carotid artery with hypermetabolic uptake in positron emission tomography (PET) scan. Resection of the mycotic aneurysm and a common-to-internal carotid artery bypass with major saphenous vein graft were performed. LA-MRSA clonal complex (CC) 398 was detected in intraoperative samples and antibiotic therapy was changed according to antibiogram. Patient was discharged at the seventh postoperative day and received antibiotic therapy for 6 weeks. US 12 months later showed patency of the bypass without collections. Mycotic aneurysms of internal carotid artery are very infrequent. MRSA isolation is rare, and to the best of our knowledge this is the first case caused by multi-drug resistant LA-MRSA CC398. The treatment includes mycotic aneurysm resection and reconstruction with venous graft bypass plus intensive antibiotic therapy.

Linezolid-resistant MRSA-CC398 carrying the cfr gene, and MRSA-CC9 isolates from pigs with signs of infection in Spain

AIMS

To perform the molecular characterization of 23 Staphylococcus aureus isolates from pigs with signs of infections recovered in Spanish farms during 2018-2019.

METHODS AND RESULTS

The antimicrobial resistance pattern and virulence profile were determined. The molecular typing was performed by different molecular techniques. The transferability of the cfr gene was assessed by conjugation and its genetic environment was determined by PCR mapping. In all, 21 isolates were methicillin-resistant S. aureus (MRSA) carrying the mecA gene (SCCmecV or non-typeable SCCmec), whereas the remaining two were methicillin-susceptible (MSSA). All but one MRSA isolates (n = 20) belonged to the CC398, being the spa t011 the most prevalent (n = 11). The remaining MRSA and the two MSSA isolates were ascribed to ST9/CC9. The S. aureus isolates exhibited resistance to (number of resistant isolates): β-lactamics (21), erythromycin and/or clindamycin (20), aminoglycosides (7), tetracycline (22), fluoroquinolones (14), chloramphenicol (5) and linezolid (1). The S. aureus isolates did not carry any of the virulence genes studied. One MRSA belonging to the CC398 showed linezolid resistance mediated by the cfr gene. The cfr gene was co-located with fexA in the Tn558 variant previously reported in the S. aureus plasmid pSCFS7.

CONCLUSIONS

Two major livestock-associated genetic lineages were detected among pigs with signs of infection in Spain. The presence of the cfr gene among LA-MRSA-CC398 is of great concern not only for veterinary medicine, but also for humans in close contact.

SIGNIFICANCE AND IMPACT OF THE STUDY

This work describes the molecular characterization of S. aureus isolates recovered from pigs with signs of infection and we report, as far as we know, the first description of MRSA-CC9 from pigs in Spain. Moreover, the detection of a MRSA-CC398 isolate carrying the multiresistance cfr gene highlights the need for continuous surveillance and awareness of LA-MRSA.

Clinical studies of the Tildox AVZ complex drug efficacy in respiratory and gastrointestinal pathologies of young pigs caused by opportunistic microflora

This publication provides a study of the efficacy of Tildox AVZ (a combined formulation of doxycycline and tylosin) in non-specific bacterial respiratory and gastrointestinal pathologies in piglets. The study population included 70 piglets with respiratory and gastrointestinal pathologies randomized into 6 groups. The effects of investigational drug used according 3-day or 5-day regimen were assessed using clinical examination, as well as bacteriological, blood count and blood chemistry lab tests. The investigational drug (Tildox AVZ) was safe for target animals and had no adverse effects, showed a similar species specificity and efficacy on the respiratory and gastrointestinal flora in piglets vs. the reference drug (Gentamicin) and allows achieving a beneficial clinical effect in respiratory and gastrointestinal diseases caused by opportunistic microflora. A significant clinical effect is achieved by Day 4 in gastrointestinal pathology and by Days 6-7 in respiratory pathology. Moreover, the control group with gastrointestinal pathology had no changes in the most of the parameters vs. baseline even on Day 7. Tildox AVZ had no adverse effects on blood count and blood chemistry parameters; on the contrary, for a number of parameters, a trend towards normalization was noted. The investigational drug was at least equivalent to the reference one (Gentamicin) and can be used for both respiratory and gastrointestinal disorders caused by the non-specific opportunistic bacterial microflora.

Epidemiology of MRSA CC398 in hospitals located in Spanish regions with different pig-farming densities: a multicentre study

BACKGROUND

Tetracycline resistance (TetR) is a marker of livestock-associated MRSA of lineage CC398.

OBJECTIVES

To determine the MRSA CC398 prevalence among TetR-MRSA recovered in Spanish hospitals located in regions with different pig-farming densities, and the influence of pig density as a key risk factor for its acquisition.

METHODS

TetR-MRSA isolates (n = 232) recovered from clinical and epidemiological samples during January-June 2016 in 20 hospitals in 13 regions with different pig-farming densities were analysed. MRSA CC398 identification, detection of spa types, methicillin resistance genes and immune evasion cluster (IEC) genes were performed by PCR/sequencing. Statistical analyses were performed to establish the relationships between MRSA CC398 prevalence and pig density.

RESULTS

The global MRSA prevalence was 29.7% (6.9% TetR-MRSA/MRSA), with 137 CC398 isolates recovered, representing 4.1% of total MRSA and 59.1% of TetR-MRSA. Among MRSA CC398, 16 different spa types were recorded (t011: 72.3%), and all but two strains were IEC negative. Higher pig-density regions were associated with significant MRSA CC398 increases in hospitals located in adjacent regions (P < 0.001). Linear regression models explained the relationships between MRSA CC398 and pig density (P < 0.001), with an increase of 6.6 MRSA CC398 cases per 100 MRSA per increase of 100 pigs/km2 in a region.

CONCLUSIONS

High pig density leads to a significant increase in MRSA CC398 in hospitals in Spain, and its combination with a high human population could help its dissemination. In Spain, the prevalence of the zoonotic CC398 lineage is closely related to pig-farming density; therefore, specific tools could be implemented in order to detect its dissemination.

Methicillin-resistant Staphylococcus aureus in food and the prevalence in Brazil: a review

Foodborne diseases (FBD) occur worldwide and affect a large part of the population, being a cause of international concern among health authorities. Staphylococcus aureus can be transmitted by contaminated food, and it is one of the pathogens that most cause foodborne outbreaks in Brazil. Currently, this organism's ability in developing resistance to antibiotics is notorious; methicillin-resistant Staphylococcus aureus-MRSA-is known for its resistance to methicillin, oxacillin, and others. MRSA is one of the leading causes of infections, becoming a major threat to human health worldwide due to the numerous toxins that can produce. At first, the transmission of MRSA occurred in clinical environments; but in recent decades, its presence has been reported in the community, outside the hospital environment, including food and food-producing animals around the world. In this review, information about MRSA was gathered to verify MRSA incidence in the world but especially in Brazil in food samples, food handlers, food-producing animals, and food processing environments. The studies show that MRSA is easily found and in certain cases with high frequency, thus representing a potential risk to public health.

Prevalence of MRSA ST398 Carriage in Nursing Home Residents in an Area of Spain With a High Density of Pig Farming

MRSA nasal carriage was detected in 15.7% of 204 residents from 6 nursing homes (NHs) in the Osona region (Barcelona, Spain), and the MRSA-ST398 lineage was identified in 15.6% of MRSA-positive residents and in 2.5% of all NH residents evaluated. Most MRSA-ST398 carriers (4 of 5) had direct or indirect contact with pig farms. Infect Control Hosp Epidemiol 2018;39:90-93.