Detection and Molecular Characterization of Methicillin-Resistant Staphylococcus aureus Isolated from Bulk Tank Milk of Cows, Sheep, and Goats

Prevalence and antimicrobial resistance profiles of mastitis causing bacteria isolated from dairy goats in Mukurweini Sub-County, Nyeri County, Kenya

BACKGROUND

Ruminant mastitis continues to be a cause of economic losses in the dairy industry and remains a major public health hazard globally.

OBJECTIVES

This cross-sectional study was carried out in Mukurweini Sub-County of Nyeri County, Kenya, to investigate the prevalence of bacteria causing mastitis, risk factors associated with goat mastitis and the antibiotic resistance profiles of bacteria isolated from the goat milk.

METHODS

Farm level data on risk factors for mastitis was obtained from 56 farmers using a semi structured questionnaire. A total of 189 goat milk samples were collected. The goat's udder was observed for signs of clinical mastitis and the California Mastitis Test (CMT) used to test the milk for sub-clinical mastitis. All samples were then cultured for morphological identification of bacteria and strain typing by Matrix Assisted Laser Desorption/Ionization (MALDI)-Time of Flight (ToF) technique. Antimicrobial susceptibility of the isolated Staphylococcus aureus, coagulase-negative Staphylococcus (CoNS), Escherichia coli, Klebsiella oxytoca, Pseudomonas spp., Enterobacter spp., Proteus vulgaris and Escherichia vulneris to eight commonly used antibiotics was done by the disc diffusion method and validated by determining the presence of antibiotic resistance genes (mecA and blaTEM) using polymerase chain reaction method.

RESULTS

The prevalence of clinical mastitis was 1.1% (2/189) while that of sub-clinical mastitis was 84.7% (160/189). Higher (p < 0.05) prevalence of mastitis was observed in goats whose houses were cleaned fortnightly and in cases where farmers used same towel to dry different does' udders during the milking process. Thirteen different bacterial species were isolated from the milk samples and identified by MALDI-ToF, and these included S. aureus (22.0%), CoNS (20.3%), E. coli (18.1%), Pseudomonas spp. (14.3%), Enterobacter spp. (10.4%), K. oxytoca (6.0%), E. vulneris (1.7%), P. vulgaris (1.7%), Raoutella ornithinolytica (1.7%), Stenotrophomonas maltophilia (1.1%), Pantoea agglomerans (1.1%), Serratia marcescens (1.1%) and Cedeceas spp. (0.6%). One hundred pathogenic bacterial isolates were randomly selected and tested for antibiotic sensitivity to eight antibiotics out of which S. aureus were 97.5% resistant to Oxacillin and 100% sensitive to Ciprofloxacin. The CoNSs were 100% resistant to Oxacillin and 100% sensitive to Ciprofloxacin. E. coli were 93.9% resistant to Oxacillin, 69.7% sensitive to Ciprofloxacin and 87.9% sensitive to both Amoxicillin/Clavulanic acid and Meropenem. The antimicrobial resistant genes detected in S. aureus and E. coli were mecA [66.7%, 0%], and blaTEM [20% and 78.3%], respectively.

CONCLUSION

In conclusion, the study showed that most of the does were affected by subclinical mastitis with the main causative bacteria being Staphylococci spp. and coliforms. Farmers need to be trained on improved control of mastitis by adoption of good milking practices and use of CMT kit for early detection of mastitis. Occurrence of multidrug resistance by key mastitis causing pathogens was shown to be prevalent and therefore there is need for development of intervention strategies.

Epidemiological characterization of clinical isolates of meticillin resistant Staphylococcus aureus through multilocus sequence typing and staphylococcal cassette chromosome mec typing in Northwest Iran

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA), is considered a potential and aggressive nosocomial pathogen. It accounts for 50% of S. aureus isolates in tertiary hospitals in Iran, however, there is no sufficient evolutionary and epidemiological investigation about this medically important bacterium. We aimed to study the lineage and evolution of MRSA in Northwest Iran during 2021-2022 based on the obtained phenotypic and genotypic characteristics.

MATERIALS AND METHODS

Seventy-two non-duplicate MRSA isolates were collected from 3 referral hospitals in Tabriz, Ardebil, and Urmia cities. The antimicrobial susceptibility patterns were determined by disk diffusion test and micro broth dilution methods. Thereafter 4 virulence genes (eta, etb, pvl, tst) and 5 types of staphylococcal cassette chromosome mec (SCCmec) were detected by PCR. In the final step, representative isolates were selected to be studied by Multilocus sequence typing (MLST).

RESULTS

The highest resistance was observed to erythromycin and clindamycin at a rate of 76.4%, followed by ciprofloxacin (61.1%), gentamicin (54.2%), rifampin (38.9%), and co-trimoxazole (27.8%). All isolates were susceptible to vancomycin. The virulence genes of etb, pvl, tst, and eta were detected in 50%, 29.2%, 21.8%, and 13.9% of isolates, respectively. SCCmec types III and I were the most prevalent types, followed by types IV, II, and V. MLST analysis revealed 6 sequence types: ST6854, ST5282, ST127, ST7804, ST1607, and ST7784. Two MLST-based clonal complexes (CC8, and CC97) were identified as well.

CONCLUSION

The ST numbers were non-repetitive. CC8 as a pandemic clone and an individual lineage and clinically significant clade was reported as the most prevalent clonal complex. It is essential periodic evaluations of antibiotic susceptibility patterns and study the evolutionary characteristics of medical-challenging microorganisms in particular MRSA to effectively treat and restrict the outbreaks.

Genomic Insights into Methicillin-Resistant Staphylococci and Mammaliicocci from Bulk Tank Milk of Dairy Farms in Serbia

The potential risk to human and animal health provides a rationale for research on methicillin-resistant staphylococci (MRS) and mammaliicocci (MRM) in dairy herds. Here, we aimed to estimate their occurrence in the bulk tank milk (BTM) samples collected in 2019-2021 from 283 bovine dairy farms in the Belgrade district. We used whole-genome sequencing to characterize the obtained isolates and assess their genetic relatedness. A total of 70 MRS/MRM were recovered, most frequently Staphylococcus haemolyticus and Mammaliicoccus sciuri. Five clusters of 2-4 genetically related isolates were identified and epidemiological data indicated transmission through, e.g., farm visits by personnel or milk collection trucks. Most MRSA isolates belonged to the typical livestock-associated lineage ST398-t034. One MRSA isolate (ST152-t355) harbored the PVL-encoding genes. Since MRS/MRM isolates obtained in this study frequently harbored genes conferring multidrug resistance (MDR), this argues for their role as reservoirs for the spread of antimicrobial resistance genes. The pipeline milking system and total bacterial count >100,000 CFU/mL were significantly associated with higher occurrences of MRS/MRM. Our study confirms that BTM can be a zoonotic source of MRS, including MDR strains. This highlights the urgent need for good agricultural practices and the continuous monitoring of MRS/MRM in dairy farms.

Prevalence of methicillin-resistant Staphylococcus aureus in dairy farms: A systematic review and meta-analysis

Methicillin-resistant Staphylococcus aureus (MRSA) is an opportunistic bacterium that causes many human and animal infections worldwide. MRSA infections are classified as priority infections owing to their high morbidity and mortality, with a significant risk of zoonotic transmission. This study aimed to determine the pooled prevalence of MRSA in dairy cattle farms and its heterogeneity. Relevant studies were retrieved from three databases: PubMed, Web of Science, and Scopus. The pooled prevalence of MRSA in dairy farms was estimated using a random-effects model. Subgroup and meta-regression analyses were used to assess the probable sources of heterogeneity. Sensitivity and publication bias analyses were also performed. A total of 94 articles were eligible for inclusion in this meta-analysis. The pooled prevalence of MRSA was estimated to be 3.81% [95% confidence interval (95% CI) = 2.61-5.20] with significantly high heterogeneity (I ² = 96.6%, p = 0.00). For the subgroup analysis among continents, the prevalence was highest in Asia (4.89%; 95% CI = 2.88-7.35) and lowest in South America (1.33%, 95% CI = 0.00-5.49). As for the year of publication, MRSA prevalence was highest in reports published from 2015 to 2018 (4.36%, 95% CI = 2.41-6.80) and lowest in reports published before 2015 (2.65%, 95% CI = 0.75-5.52). As for sample type, the prevalence of MRSA in cattle milk (3.91%, 95% CI = 2.64-5.39) was higher than that in other sample types (1.19%, 95% CI = 0.05-3.24). These three factors were not significantly associated with the pooled prevalence of MRSA (p > 0.05). Therefore, the findings of this study indicate that the prevalence of MRSA has been minimal and consistent in dairy cattle farms over time.

Usefulness of molecular typing methods for epidemiological and evolutionary studies of Staphylococcus aureus isolated from bovine intramammary infections

In cattle, Staphylococcus aureus is a major pathogen of increasing importance due to its association with intramammary infections (IMIs), which are a primary cause of antibiotic use on farms and thus of the rise in antibiotic resistance. Methicillin-resistant S. aureus (MRSA), which are frequently isolated from cases of bovine mastitis, represent a public health problem worldwide. Understanding the epidemiology and the evolution of these strains relies on typing methods. Such methods were phenotypic at first, but more recently, molecular methods have been increasingly utilized. Multiple-locus variable number tandem repeat analysis (MLVA), a high-throughput molecular method for determining genetic diversity and the emergence of host- or udder-adapted clones, appears to be the most useful PCR-based method. Despite the difficulties present in reproducibility, interlaboratory reliability, and hard work, it is agreed that pulsed-field gel electrophoresis (PFGE) remains the gold standard, particularly for short-term surveillance. Multilocus sequence typing (MLST) is a good typing method for long-term and global epidemiological investigations, but it is not suitable for outbreak investigations. Staphylococcal protein A (spa) typing is the most widely used method today for first-line typing in the study of molecular evolution, and outbreaks investigations. Staphylococcal cassette chromosome mec (SCCmec) typing has gained popularity for the evolutionary analysis of MRSA strains. Whole-genome sequencing (WGS) and DNA microarrays that represent relatively new DNA-based technologies, provide more information for tracking antibioresistant and virulent outbreak strains. They offer a higher discriminatory power, but are not suitable for routine use in clinical veterinary medicine at this time. Descriptions of the evolution of these methods, their advantages, and limitations are given in this review.

Role of milk and milk products in the spread of methicillin-resistant Staphylococcus aureus in the dairy production chain

Milk and milk products can harbor a multiple varieties of microorganisms. Therefore, they can be an important source of foodborne pathogens, including multidrug-resistant bacteria. Methicillin-resistant Staphylococcus aureus (MRSA) causes a wide spectrum of infections both in animals and humans. Over the last two decades, the presence of MRSA in foods and food-producing animals, including milk and milk products, has been frequently reported worldwide, raising public health concerns. In order to monitor and prevent foodborne MRSA contamination, it is necessary to understand their sources, the pheno/genotypic characteristics of the strains, and their transmission dynamics. In this review, studies conducted worldwide were summarized in order to assess the prevalence and diversity of MRSA circulating in milk and milk products. The risk factors for the occurrence of MRSA in milk and milk products were also discussed with preventive and control measures to avoid MRSA contamination in the dairy food chain.

Occurrence and Characteristics of Staphylococcus aureus Isolated from Dairy Products

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

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): antimicrobial-resistant Staphylococcus aureus in cattle and horses

Staphylococcus aureus (S. aureus) was identified among the most relevant antimicrobial-resistant (AMR) bacteria in the EU for cattle and horses in previous scientific opinions. Thus, it has been assessed according to the criteria of the Animal Health Law (AHL), in particular criteria of Article 7 on disease profile and impacts, Article 5 on its eligibility to be listed, Annex IV for its categorisation according to disease prevention and control rules as in Article 9, and Article 8 for listing animal species related to the bacterium. The assessment has been performed following a methodology previously published. The outcome is the median of the probability ranges provided by the experts, which indicates whether each criterion is fulfilled (lower bound ≥ 66%) or not (upper bound ≤ 33%), or whether there is uncertainty about fulfilment. Reasoning points are reported for criteria with uncertain outcome. According to the assessment here performed, it is uncertain whether AMR S. aureus can be considered eligible to be listed for Union intervention according to Article 5 of the AHL (60-90% probability). According to the criteria in Annex IV, for the purpose of categorisation related to the level of prevention and control as in Article 9 of the AHL, the AHAW Panel concluded that the bacterium does not meet the criteria in Sections 1, 2 and 4 (Categories A, B and D; 1-5%, 5-10% and 10-33% probability of meeting the criteria, respectively) and the AHAW Panel was uncertain whether it meets the criteria in Sections 3 and 5 (Categories C and E, 33-90% and 60-90% probability of meeting the criteria, respectively). The animal species to be listed for AMR S. aureus according to Article 8 criteria include mainly mammals, birds, reptiles and fish.

Antimicrobial Resistance and Clonal Lineages of Staphylococcus aureus from Cattle, Their Handlers, and Their Surroundings: A Cross-Sectional Study from the One Health Perspective

Staphylococcus aureus have been progressively identified in farm animals and in humans with direct contact with these animals showing that S. aureus may be a major zoonotic pathogen. Therefore, we aimed to isolate S. aureus from cows, their handlers, and their immediate surroundings, and to investigate the antimicrobial resistance and genetic lineages of the isolates. Mouth and nose swabs of 244 healthy cows (195 Maronesa, 11 Holstein-Friesians, and 28 crossbreeds), 82 farm workers, 53 water and 63 soil samples were collected. Identification of species was carried out by MALDI-TOF MS Biotyper. The presence of antimicrobial resistance genes and virulence factors was assessed based on gene search by PCR. All isolates were typed by multilocus sequence typing and spa-typing. From 442 samples, 33 (13.9%), 24 (29.3%), 1 (2%), and 1 (2%) S. aureus were recovered from cows, farm workers, water, and soil samples, respectively. Most of the isolates showed resistance only to penicillin. S. aureus isolates were ascribed to 17 sequence types (STs) and 26 spa-types. Some clonal lineages were common to both cows and farm workers such as ST30-t9413, ST72-t148, and ST45-t350. Through a One Health approach, this study revealed that there is a great diversity of clonal lineages of S. aureus in cows and their handlers. Furthermore, some S. aureus lineages are common to cows and handlers, which may suggest a possible transmission.

Aptasensors for Staphylococcus aureus Risk Assessment in Food

Staphylococcus aureus (S. aureus) is the top ordinary pathogen causing epidemic and food poisoning. The authentication of S. aureus has great significance for pathologic diagnosis and food hygiene supervision. Various biosensor methods have been established for identification. This paper reviews the research progress of aptasensors for S. aureus detection, focusing on the classification of aptamer technologies, including optical aptasensors and electrochemical aptasensors. Furthermore, the feasibility and future challenges of S. aureus detection for aptamer assays are discussed. Combining aptasensors with nanomaterials appears to be the developing trend in aptasensors.

The molecular epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) in the Czech Republic

OBJECTIVES

To gain data on the current molecular epidemiology and resistance of MRSA in the Czech Republic.

METHODS

Between September 2017 and January 2018, a total of 441 single-patient MRSA isolates were collected from 11 Czech hospitals and analysed by spa typing, SCCmec typing, antibiotic susceptibility testing, detection of the PVL toxin and the arcA gene.

RESULTS

Of all MRSA isolates, 81.41% (n = 359) belonged to the CC5-MRSA clone represented by the spa types t003 (n = 136), t586 (n = 92), t014 (n = 81), t002 (n = 20) and other spa types (n = 30); a majority of the CC5 isolates (n = 348, 96.94%) carried SCCmec type II. The occurrence of CC5-MRSA was more likely in older inpatients and associated with a healthcare origin (P < 0.001). The CC5-MRSA isolates were resistant to more antimicrobial drugs compared with the other MRSAs (P < 0.001). Interestingly, t586 was detected in blood samples more often than the other spa types and, contrary to other spa types belonging to CC5-MRSA, t586 was not associated with patients of advanced age. Other frequently found lineages were CC8 (n = 17), CC398 (n = 11) and CC59 (n = 10). The presence of the PVL was detected in 8.62% (n = 38) of the MRSA isolates.

CONCLUSIONS

The healthcare-associated CC5-MRSA-II lineage (t003, t586, t014) was found to be predominant in the Czech Republic. t586 is a newly emerging spa type in the Czech Republic, yet reported rarely in other countries. Our observations stress the need for MRSA surveillance in the Czech Republic in order to monitor changes in MRSA epidemiology.

Antibiotic Resistance, spa Typing and Clonal Analysis of Methicillin-Resistant Staphylococcus aureus (MRSA) Isolates from Blood of Patients Hospitalized in the Czech Republic

Staphylococcus aureus is one of the major causes of bloodstream infections. The aim of our study was to characterize methicillin-resistant Staphylococcus aureus (MRSA) isolates from blood of patients hospitalized in the Czech Republic between 2016 and 2018. All MRSA strains were tested for antibiotic susceptibility, analyzed by spa typing and clustered using a Based Upon Repeat Pattern (BURP) algorithm. The representative isolates of the four most common spa types and representative isolates of all spa clonal complexes were further typed by multilocus sequence typing (MLST) and staphylococcal cassette chromosome mec (SCCmec) typing. The majority of MRSA strains were resistant to ciprofloxacin (94%), erythromycin (95.5%) and clindamycin (95.6%). Among the 618 strains analyzed, 52 different spa types were detected. BURP analysis divided them into six different clusters. The most common spa types were t003, t586, t014 and t002, all belonging to the CC5 (clonal complex). CC5 was the most abundant MLST CC of our study, comprising of 91.7% (n = 565) of spa-typeable isolates. Other CCs present in our study were CC398, CC22, CC8, CC45 and CC97. To our knowledge, this is the biggest nationwide study aimed at typing MRSA blood isolates from the Czech Republic.

Prevalence, Antimicrobial Resistance, and Molecular Characterization of Staphylococcus aureus Isolated from Animals, Meats, and Market Environments in Xinjiang, China

Staphylococcus aureus has been recognized as an important foodborne pathogen. However, knowledge about the epidemiology and genetic characteristics of S. aureus in the meat production chain from farm to market is limited. The aim of this study was to investigate the genetic characteristics of S. aureus in animal samples isolated from Xinjiang province farms and farmer' markets, by determining staphylococcal protein A (spa) repeat region and virulence factor typing, and by assessment of antimicrobial resistance. Out of 1324 samples, 128 (9.7%) were positive for S. aureus, 26 (2.0%) of them were identified as methicillin-resistant S. aureus (MRSA) and 88 (6.6%) of them were identified as vancomycin-resistant S. aureus (VRSA). Antimicrobial resistance was determined using the disk diffusion method. S. aureus isolates showed resistance to penicillin G (98.4%), clarithromycin (69.5%), erythromycin (69.5%), vancomycin (68.8%), and tetracycline (67.2%). A total of 80.4% of isolates showed resistance to three or more antimicrobial classes. PCR was used to detect ten virulence genes such as the enterotoxin (sea, seb, and sec), hemolysin (hla and hlb), clumping factor (clfA), and fibronectin-binding proteins A and B (fnbA and fnbB). Our study showed that isolates harbored two or seven virulence genes. All strains encode hla and clfA, and half of them encode hlb and enterotoxin genes. The spa typing results showed that the 128 isolates were grouped into 32 spa types. The main spa types were t127 (22.7%), t2592 (12.5%), t437 (10.9%), and t2616 (10.9%). Notably, isolates of t437 type accounted for 46.2% of the MRSA. Our data indicate that meats in the slaughterhouse and farmers' markets were contaminated with S. aureus. S. aureus virulence genes and spa types were diverse, and its antibiotic resistance was serious. The presence of MRSA and VRSA represents potential public health risks and warrants further investigation regarding the driving factors of such resistance and their transmission to humans.

The first outbreak of methicillin-resistant Staphylococcus aureus in dairy cattle in Poland with evidence of on-farm and intrahousehold transmission

Staphylococcus aureus is a widely recognized pathogen responsible for many serious diseases in both humans and animals. It is also one of the major causative agents of bovine mastitis. Methicillin-resistant S. aureus (MRSA), although relatively rare in this pathology, has been increasingly reported in livestock animals, mainly in pigs, but also cattle, sheep, and poultry. The recent emergence of livestock-associated (LA-)MRSA is cause for an immediate public health concern due to the risk of zoonotic transmission to humans, and is of particular concern for people who work in animal husbandry or have prolonged contact with livestock animals. This study reports on the first LA-MRSA outbreak in dairy cattle and the first probable case of MRSA transmission between humans and cows in Poland. A single dairy farm located in Eastern Poland was monitored on a regular basis for the occurrence of mastitis. Over a 1-yr study period, 717 quarter-milk samples from 583 cows were collected and examined microbiologically. A total of 5 MRSA isolates from as many cows with subclinical mastitis were cultured. They all belonged to the same outbreak, given a 2-mo time window in which they were identified. During the outbreak, 24 oral and nasal swabs were voluntarily taken from 6 people: a milker, a veterinarian, and 4 members of the veterinarian's family. Eight swabs from a milker, veterinarian, and 2 family members yielded positive MRSA cultures. All MRSA isolates were genotyped with a combination of multiple-locus variable number tandem repeat analysis, multilocus sequence typing, and staphylococcal protein A gene (spa) typing. Eleven bovine (n = 5; 5 cases) and human (n = 6; 4 cases) isolates showed an identical drug-susceptibility profile and were indistinguishable upon multiple-locus variable number tandem repeat analysis (pattern A), multilocus sequence typing (ST398) and spa (t034) typing. The results of this study provide the evidence of transmission of MRSA between humans and cows, and between humans in the family setting. This work, despite being a preliminary investigation, underscores the risk of intra- and interspecies transmission of LA-MRSA and urges enhancement of the existing biosecurity measures aimed at preventing MRSA (and other milk pathogens) spread at both the farm- and household levels.

Methicillin-resistant Staphylococcus aureus (MRSA) isolated from chicken meat and giblets often produces staphylococcal enterotoxin B (SEB) in non-refrigerated raw chicken livers

Methicillin-resistant Staphylococcus aureus (MRSA) is responsible for several difficult-to-treat infections and staphylococcal food poisoning (SFP). This study was conducted to investigate the prevalence and enterotoxigenicity of MRSA in broiler chicken meat and giblets. A total of 5.5% (8/144) of the examined samples were contaminated with mecA positive/mecC negative MRSA, with staphylococcal counts of approximately 10² colony forming units (CFU)/g in breast, leg and gizzard samples and approximately 3.3 × 10³ CFU/g in frozen liver samples. Most MRSA isolates (75%, 6/8) harboured the staphylococcal enterotoxin B (seb) gene. Reverse transcription-PCR (RT-PCR) showed that MRSA isolates initiated SEB production in experimentally contaminated chicken livers within 24 h of storage at temperatures over 8 °C. SEB was maximally produced at 24 °C when the MRSA counts reached 7.3 × 10³ ± 1.2 × 10³ CFU/g sample homogenate. The current study concludes that the main broiler chicken MRSA isolates in Egypt harbour the seb gene. To mitigate possible SEB production, especially in broiler chicken livers, a maximum "out of refrigeration" time limit should be implemented for cold chain poultry products.

Burden and antimicrobial resistance of S. aureus in dairy farms in Mekelle, Northern Ethiopia

Background

Staphylococcus aureus is a frequent colonizer of human and several animal species, including dairy cows. It is the most common cause of intramammary infections in dairy cows. Its public health importance increases inline to the continuous emergence of drug-resistant strains; such as Methicillin-resistant S. aureus (MRSA). Indeed, the recent emergence of human and veterinary adapted MRSA demands serious attention. The aim of this study was to determine the burden and drug resistance pattern of S. aureus in dairy farms in Mekelle and determine the molecular characteristics of MRSA.

Results

This study was done on 385 lactating dairy cows and 71 dairy farmers. The ages of the cows and farmworkers were between 3 and 14 and 17–63 years respectively. S. aureus was isolated from 12.5% of cows and 31% of farmworkers. Highest resistance was observed for penicillin (> 90%) followed by tetracycline (32–35%) and trimethoprim-sulphamethoxazole (10–27%). But no resistance was observed for vancomycin, daptomycin, and rifampin. Only one isolate was MRSA both phenotypically and harboring mecA. This isolate was from nasal of a farmworker and was MRSA SCCmec Iva, spa type t064 of CC8. Multi-drug resistance was observed in 6.2% of cow isolates and 13.6% of nasal isolates.

Conclusions

In this study, S. aureus infected 12.5% of dairy cows and colonized 31% of farmworkers. Except for penicillin, resistance to other drugs was rare. Although no MRSA was found from dairy cows the existence of the human and animal adapted and globally spread strain, MRSA SCCmec IVa spa t064, warrants for a coordinated action to tackle AMR in both human and veterinary in the country.