Antimicrobial resistance, virulence gene profile and molecular typing of Staphylococcus aureus isolates from dairy cows in Xinjiang Province, northwest China

Genomic insights of S. aureus associated with bovine mastitis in a high livestock activity region of Mexico

IMPORTANCE

Bovine mastitis, predominantly associated with gram-positive Staphylococcus aureus, poses a significant threat to dairy cows, leading to a decline in milk quality and volume with substantial economic implications.

OBJECTIVE

This study investigated the incidence, virulence, and antibiotic resistance of S. aureus associated with mastitis in dairy cows.

METHODS

Fifty milk-productive cows underwent a subclinical mastitis diagnosis, and the S. aureus strains were isolated. Genomic DNA extraction, sequencing, and bioinformatic analysis were performed, supplemented by including 124 S. aureus genomes from cows with subclinical mastitis to enhance the overall analysis.

RESULTS

The results revealed a 42% prevalence of subclinical mastitis among the cows tested. Genomic analysis identified 26 sequence types (STs) for all isolates, with Mexican STs belonging primarily to CC1 and CC97. The analyzed genomes exhibited multidrug resistance to phenicol, fluoroquinolone, tetracycline, and cephalosporine, which are commonly used as the first line of treatment. Furthermore, a similar genomic virulence repertoire was observed across the genomes, encompassing the genes related to invasion, survival, pathogenesis, and iron uptake. In particular, the toxic shock syndrome toxin (tss-1) was found predominantly in the genomes isolated in this study, posing potential health risks, particularly in children.

CONCLUSION AND RELEVANCE

These findings underscore the broad capacity for antibiotic resistance and pathogenicity by S. aureus, compromising the integrity of milk and dairy products. The study emphasizes the need to evaluate the effectiveness of antibiotics in combating S. aureus infections.

Recent Trends in S. aureus and E. coli-Based Endometritis, and the Therapeutic Evaluation of Sodium Alginate-Based Antibiotics and Nanoparticles

Postpartum infection of the uterus by pathogenic bacteria is exacerbated due to a lack of sufficient epidemiological studies and evidence-based therapeutics. Therefore, this study was planned to find the prevalence, risk factors, and drug-resistance profile of S. aureus and E. coli isolated from bovine endometritis and to evaluate the antibacterial potential of sodium alginate-based antibiotics and nanoparticles. The study revealed 34.21% S. aureus and 31.57% E. coli, whereas most of the assumed risk factors presented significant association in this study. S. aureus showed the highest resistance against fusidic acid (60%) and cefoxitin (50%), while the highest resistance in E. coli was found against fusidic acid (60%), gentamicin (60%), chloramphenicol (50%), and cefoxitin (50%). Tylosin coupled with MgO nanoparticles stabilized in sodium alginate gel (Tylo + MgO + gel) presented significantly lower minimum inhibitory concentration (MIC) against E. coli, showing 13.88 ± 4.51 µg/mL after 24 h incubation. On the other hand, gel-based preparations showed MIC as 31.25 ± 0 µg/mL (Tylo + gel + MgO) and 26.04 ± 9.02 µg/mL (Tylo + Gel) against S. aureus. Generally, the MICs of non-gel-based preparations were significantly higher against bacteria except ampicillin against S. aureus in this study. The toxicity analysis of MgO nanoparticles presented 20-80% mortality of snails against a wider range of 0.01 mg/mL-10 mg/mL. The histopathological parameters concluded MgO nanoparticles safe to use on off targets. The current study thus concludes the rise in antimicrobial resistance while the gel-based products appearing as effective antimicrobials with sufficient safety margins for off-targets. The study thus invites further investigation for the development of suitable and affordable modified therapeutics for better health and production of animals.

Molecular characteristics of Staphylococcus aureus strains isolated from subclinical mastitis of water buffaloes in Guangdong Province, China

Intramammary infections (IMI) in animals reared for milk production can result in large economic losses and distress to the animals. Staphylococcus aureus is an important causative agent of IMI in dairy cows, but its prevalence in water buffaloes has not been determined. Therefore, the current study was conducted to investigate the prevalence of subclinical mastitis in water buffaloes and the antimicrobial susceptibility, virulence genes and biofilm formation abilities of Staphylococcus aureus isolates recovered from water buffaloes in Guangdong, China. Staphylococcus aureus strains were isolated from milk samples of water buffaloes with subclinical mastitis, and twofold microdilution, PCR and crystal violet staining methods were used to determine antimicrobial susceptibility, distributions of virulence and antimicrobial resistance genes and biofilm formation ability, respectively. Our results indicated that 29.44% of water buffaloes were diagnosed with subclinical mastitis, and the most prevalent pathogens were Escherichia coli (96.17%), coagulase-negative staphylococci (CoNS) (67.60%) and S. aureus (28.57%). Most S. aureus isolates showed resistance to bacitracin, doxycycline, penicillin, florfenicol, and tetracycline but were susceptible to ciprofloxacin, ceftizoxime, cefoquinoxime, and ofloxacin. Moreover, 63.72% of S. aureus isolates were positive for tetM, and the prevalence of msrB, blaZ, mecA, fexA, and tetK ranged from 21.24 to 6.19%. All S. aureus isolates harbored clfB and icaA genes, and the virulence genes hla (93.8%), hld (91.15%), clfA (90.27%), fnbA (86.73%), and hlb (83.19%), and tsst, icaD, sec, see, fnbB, and sea showed a varied prevalence ranging from 3.5 to 65.49%. All S. aureus isolates possessed the ability to form biofilms, and 30.09% of isolates showed strong biofilm formation abilities, while 19.47% of isolates were weak biofilm producers. Our results indicated that subclinical mastitis is prevalent in water buffaloes in Guangdong, China, and S. aureus is prevalent in samples from water buffaloes with subclinical mastitis. Most S. aureus isolates were susceptible to cephalosporins and fluoroquinolones; thus, ceftizoxime and cefoquinoxime can be used to treat subclinical mastitis in water buffaloes.

Molecular epidemiology and characterization of antimicrobial-resistant Staphylococcus haemolyticus strains isolated from dairy cattle milk in Northwest, China

Introduction

Non-aureus Staphylococcus (NAS) species are currently the most commonly identified microbial agents causing sub-clinical infections of the udder and are also deemed as opportunistic pathogens of clinical mastitis in dairy cattle. More than 10 NAS species have been identified and studied but little is known about S. haemolyticus in accordance with dairy mastitis. The present study focused on the molecular epidemiology and genotypic characterization of S. haemolyticus isolated from dairy cattle milk in Northwest, China.

Methods

In this study, a total of 356 milk samples were collected from large dairy farms in three provinces in Northwest, China. The bacterial isolation and presumptive identification were done by microbiological and biochemical methods following the molecular confirmation by 16S rRNA gene sequencing. The antimicrobial susceptibility testing (AST) was done by Kirby-Bauer disk diffusion assay and antibiotic-resistance genes (ARGs) were identified by PCR. The phylogenetic grouping and sequence typing was done by Pulsed Field Gel Electrophoresis (PFGE) and Multi-Locus Sequence Typing (MLST) respectively.

Results

In total, 39/356 (11.0%) were identified as positive for S. haemolyticus. The overall prevalence of other Staphylococcus species was noted to be 39.6% (141/356), while the species distribution was as follows: S. aureus 14.9%, S. sciuri 10.4%, S. saprophyticus 7.6%, S. chromogenes 4.2%, S. simulans 1.4%, and S. epidermidis 1.1%. The antimicrobial susceptibility of 39 S. haemolyticus strains exhibited higher resistance to erythromycin (92.3%) followed by trimethoprim-sulfamethoxazole (51.3%), ciprofloxacin (43.6%), florfenicol (30.8%), cefoxitin (28.2%), and gentamicin (23.1%). All of the S. haemolyticus strains were susceptible to tetracycline, vancomycin, and linezolid. The overall percentage of multi-drug resistant (MDR) S. haemolyticus strains was noted to be 46.15% (18/39). Among ARGs, mphC was identified as predominant (82.05%), followed by ermB (33.33%), floR (30.77%), gyrA (30.77%), sul1 (28.21%), ermA (23.08%), aadD (12.82%), grlA (12.82%), aacA-aphD (10.26%), sul2 (10.26%), dfrA (7.69%), and dfrG (5.13%). The PFGE categorized 39 S. haemolyticus strains into A-H phylogenetic groups while the MLST categorized strains into eight STs with ST8 being the most predominant while other STs identified were ST3, ST11, ST22, ST32, ST19, ST16, and ST7.

Conclusion

These findings provided new insights into our understanding of the epidemiology and genetic characteristics of S. haemolyticus in dairy farms to inform interventions limiting the spread of AMR in dairy production.

Microbial community structure and antibiotic resistance profiles in sediments with long-term aquaculture history

The aim of this investigation was to examine the microbial populations and their resistance patterns towards antibiotics, including the impact of nitrogen metabolism in response to the reintroduction of antibiotics, as well as the presence of resistance genes in sediments from shrimp ponds that have been utilized for extended periods of 5, 15, and over 30 years. Results showed that the sediments exhibited a high prevalence of Proteobacteria, Bacteroidetes, Planctomycetes, Chloroflexi, and Oxyphotobacteria as the most abundant bacterial phyla, accounting for 70.35-77.43% of the total bacterial community. The five most abundant phyla of fungi detected in all sediments, namely Rozellomycota, Ascomycota, Aphelidiomycota, Basidiomycota, and Mortierellomycota, constituted 24.26-32.54% of the total fungal community. It was highly probable that the Proteobacteria and Bacteroidetes phyla serve as the primary reservoir of antibiotic-resistant bacteria (ARB) in the sediment, which included various genera like Sulfurovum, Woeseia, Sulfurimonas, Desulfosarcina, and Robiginitalea. Among these genera, Sulfurovum appeared to be the most widespread in the sediment of aquaculture ponds that have been in operation for more than three decades, while Woeseia dominated in ponds that have been recently reclaimed and have a 15-year aquaculture history. Antibiotic resistance genes (ARGs) were categorized into seven distinct groups according to their mechanism of action. The prevalence of multidrug-resistant ARGs was found to be the highest among all types, with an abundance ranging from 8.74 × 10^-2 to 1.90 × 10^-1 copies per 16S rRNA gene copies. The results of a comparative analysis of sediment samples with varying aquaculture histories indicated that the total relative abundance of ARGs was significantly diminished in sediment with a 15-year aquaculture history as opposed to sediment with either a 5-year or 30-year aquaculture history. Another assessment of antibiotic resistances in aquaculture sediments involved an examination of the effects of reintroducing antibiotics on nitrogen metabolism processes. The findings revealed that the rates of ammonification, nitrification, and denitrification in the sediment with a history of 5 years and 15 years, decreased as the concentration of oxytetracycline increased from 1 to 300, and 2000 mg/kg, and inhibitory effects were found to be less pronounced in sediments with a 5-year history compared to those with a 15-year history. In contrast, oxytetracycline exposure led to a significant decrease in the rates of these processes in aquaculture pond sediments with a >30 years of aquaculture history across all the concentrations tested. The emergence and dissemination of antibiotic resistance profiles in aquaculture environments requires attention in future aquaculture management.

Phenotypic and Genotypic Characterization of Macrolide-Lincosamide-Streptogramin Resistance in Staphylococcus aureus Isolates from Bovine and Human

In this study, penicillin, oxacillin, and macrolide-lincosamide-streptogramin (MLS) resistance in S. aureus strains that were isolated from bovine mastitis cases, and human patients were investigated. Inducible clindamycin resistance (iML) was not found in 30 bovine isolates, while it was detected in 3 (10%) of 30 human isolates. MIC90 values of penicillin, oxacillin and macrolide-lincosamides (ML) were 2, 0.19, >256 µg/ml in bovine isolates and were 3, 3 and 0.19-1.5 µg/ml in human isolates, respectively. Streptogramin resistance was not found in both bovine and human isolates. Although the mecA gene was detected in all of the oxacillin resistant isolates, blaZ gene could not be detected in penicillin resistant isolates. The erm(B) gene was detected in 5 (38.6%) of 13 ML-resistant bovine isolates, and the mph(C) gene was detected in 2 (66.66%) of 3 human isolates. As a result, resistance to penicillin and oxacillin was found to be higher in human S. aureus isolates, while ML resistance was found to be higher in bovine isolates in this investigation. It was concluded that the presence of genes in extra-chromosomal elements associated to penicillin and macrolide resistance should be investigated. The data obtained from this study will contribute to the studies on antimicrobial susceptibility in the field of human and veterinary medicine.

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

BACKGROUND

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

The novel fosfomycin resistance gene fosY is present on a genomic island in CC1 methicillin-resistant Staphylococcus aureus

Fosfomycin has gained attention as a combination therapy for methicillin-resistant Staphylococcus aureus infections. Hence, the detection of novel fosfomycin-resistance mechanisms in S. aureus is important. Here, the minimal inhibitory concentrations (MICs) of fosfomycin in CC1 methicillin-resistant S. aureus were determined. The pangenome analysis and comparative genomics were used to analyse CC1 MRSA. The gene function was confirmed by cloning the gene into pTXΔ. A phylogenetic tree was constructed to determine the clustering of the CC1 strains of S. aureus. We identified a novel gene, designated fosY, that confers fosfomycin resistance in S. aureus. The FosY protein is a putative bacillithiol transferase enzyme sharing 65.9-77.5% amino acid identity with FosB and FosD, respectively. The function of fosY in decreasing fosfomycin susceptibility was confirmed by cloning it into pTXΔ. The pTX-fosY transformant exhibited a 16-fold increase in fosfomycin MIC. The bioinformatic analysis showed that fosY is in a novel genomic island designated RI_fosY (for "resistance island carrying fosY") that originated from other species. The global phylogenetic tree of ST1 MRSA displayed this fosY-positive ST1 clone, originating from different regions, in the same clade. The novel resistance gene in the fos family, fosY, and a genomic island, RI_fosY, can promote cross-species gene transfer and confer resistance to CC1 MRSA causing the failure of clinical treatment. This emphasises the importance of genetic surveillance of resistance genes among MRSA isolates.

Relationship between Biofilm Formation and Antibiotic Resistance and Adherence Genes in Staphylococcus aureus Strains Isolated from Raw Cow Milk in Shahrekord, Iran

The production of biofilms by S. aureus contributes significantly to treatment failures. The present study aims to establish the relationship between biofilm formation and antibiotic resistance and adhesion genes in Staphylococcus aureus strains isolated from raw cow milk in Shahrekord, Iran. A total of 90 samples of raw cow's milk were collected. Presumptive S. aureus strains were obtained using Baird-Parker plates after enrichment in tryptone soy broth, and final colonies were selected from brain heart infusion. Additional tests such as coagulase were done, and the identification was confirmed by the detection of the aroA gene. Biofilm producing strains were screened using a spectrophotometry method applied to microplates. Crystal violet staining was used to quantify the formation of biofilm. An antibiotic susceptibility test was performed using the Kirby-Bauer disc diffusion method. PCR was used to detect several biofilm and antibiotics resistance related genes. The chi-square test and Fisher's exact test were used to establish a statistically significant relationship between biofilm reaction and antibiotic resistance (p value <0.05). Results show a moderate (38.88%) recovery rate of S. aureus in milk and 65.71% of the isolates were strong biofilm producers. Antibiotic susceptibility tests show an alarming rate of resistance to beta-lactam antibiotics, especially penicillin (100%), ampicillin (91.42%), and oxacillin (71.42%). This finding correlates with antibiotic resistance gene detection, in which the gene blaZ was most found (71.42%), followed by mecA and Aac-D (42.85%). Detection of biofilm-related genes shows that all the genes targeted were found among S. aureus isolates. Statistical tests show a significant correlation between biofilm production and antibiotic resistance in S. aureus. This study revealed that there is a significant correlation between biofilm production and antibiotic resistance in S. aureus isolated from raw milk. These results highlight the need for regular surveillance of the occurrence of S. aureus strains in milk and milk products in Iran.

Detection of Antibiotic Resistance, Virulence Gene, and Drug Resistance Gene of Staphylococcus aureus Isolates from Bovine Mastitis

Antimicrobial therapy plays an important role in mastitis control caused by Staphylococcus aureus but has become less effective due to widespread drug resistance. The purpose of this study was to detect antibiotic resistance, drug resistance gene, and virulence gene of S. aureus strains. In this study, 2,962 milk samples were collected from 43 dairy farms located in 16 provinces of China and cultured for isolation of S. aureus. Antibiotic resistance, capsular polysaccharide, spa typing, virulence genes, and drug resistance genes of the strains were analyzed. Of 2,962 samples, 298 strains were isolated and identified as S. aureus. The strains exhibited high percentages of resistance to penicillin G (91.95%). Moreover, all strains showed resistance to more than one antimicrobial agent but were sensitive to nitrofurantoin and sulfamethoxazole/trimethoprim. The results indicate that type 8 was the dominant capsular polysaccharide serotype and t459 was the dominant spa type. The most prevalent virulence gene was clfA (98%). The resistance genes of several antibiotics were detected, among which the blaZ gene (92.95%) was the highest. In conclusion, we present the antimicrobial resistance and virulence genes of S. aureus in this study which are of importance for mastitis control. IMPORTANCE Bovine mastitis is a serious disease associated with both high incidence and economic loss, posing a major challenge to the dairy industry worldwide. Staphylococcus aureus is one of the most common pathogens to cause bovine mastitis, and antimicrobial therapy plays an important role in mastitis control caused by S. aureus but has become less effective due to widespread drug resistance. The purpose of this study was to detect antibiotic resistance, drug resistance gene, and virulence gene of S. aureus strains, which would be helpful to mastitis control.

Virulence and antimicrobial resistance gene profiles of Staphylococcus aureus associated with clinical mastitis in cattle

Staphylococcus aureus (S. aureus) is the most prevalent microorganism associated with mastitis in cattle, which harbours several virulence factors and antibiotic resistance genes. The present study aimed to characterize S. aureus isolated from mastitic milk of the cattle for antibiotic resistance (blaZ and mecA), haemolysins (hla and hlb) and enterotoxins (sea, seb, sec, and sed) genes. A total of 69 staphylococci were isolated and phenotypically characterized for haemolytic properties on 5% sheep blood agar medium. Out of 69 isolates, 55 (79.71%) were identified as S. aureus by polymerase chain reaction assay. Among S. aureus, the majority of the isolates harboured the gene blaZ (92.73%), followed by coa (89.09%), hlb (60%) and hla (49.09%). Gene mecA responsible for methicillin resistance was detected in 23.64% of S. aureus isolates. Enterotoxin genes seb (9.09%), sec (1.82%) and sed (7.27%) responsible for food poisoning were detected at a comparatively lower rate and none of the S. aureus strain was found positive for sea. Additionally, antimicrobial susceptibility study of S. aureus against 18 antimicrobial discs showed maximum resistance to oxytetracycline, penicillin, and fluoroquinolone groups, contrarily, we observed maximum sensitivity to methicillin and cefuroxime antimicrobials. The high occurrence rate of S. aureus harbouring genes for virulence factors and antimicrobial resistance needs appropriate strategies to control the pathogen spread to the human population.

Prevalence and Characteristics of Staphylococcus aureus Isolated From Retail Raw Milk in Northern Xinjiang, China

Staphylococcus aureus is one of the main pathogens causing mastitis in dairy animals worldwide. It is an important opportunistic pathogen of raw milk, and the enterotoxin causes significant food poisoning. Monitoring the antibiotic resistance of S. aureus in raw milk is helpful for a risk assessment of S. aureus. In this study, 62 strains (43.1%) of S. aureus were isolated from 144 retail raw milk samples of different varieties from four regions in northern Xinjiang, China. Among them, the isolation rates at Shihezi, Hami, Altay, and Tacheng were 58.1% (54/93), 12.9% (4/31), 18.2% (2/11), and 22.2% (2/9), respectively. The isolation rate of positive strains in cow milk samples was the highest (61.7%, 37/60), followed by camel milk (35.9%, 23/64), and horse milk (10.0%, 2/20). The results of the classical virulence genes test showed that 12.9% (8/62) of the isolates carried at least one virulence gene. The main genotype was see (6.5%, 4/62), followed by sea+sec (3.2%, 2/62), sea (1.6%, 1/62), and sec (1.6%, 1/62). The analysis of 13 resistance genes and the susceptibility to 12 different antibiotics of 62 isolates showed that 80.6% (50/62) of the strains were resistant to at least one antibiotic, and 46.8% (29/62) were resistant to three or more antibiotics. The isolated strains had the highest resistance rate to penicillin (72.6%, 45/62), and 25.8% (16/62) of the isolates carried the blaZ resistance gene. In addition, 32 strains (51.6%, 32/62) of methicillin-resistant S. aureus were detected. All isolates had the ability to form biofilms. The pulsed-field gel electrophoresis results showed that the 47 isolates revealed 13 major pulsotypes (P1–P13) and 26 subtypes with 80% similarity, indicating the overall genetic diversity in the distribution area and sources of the samples. These findings indicate that S. aureus causes serious pollution of raw milk in northern Xinjiang, which has a negative effect on public health. Therefore, control measures and continuous monitoring should be undertaken to ensure the quality and safety of raw milk.

Molecular Characterization of Staphylococcus aureus Isolated from Raw Milk Samples of Dairy Cows in Manhiça District, Southern Mozambique

Staphylococcal infections are among the most common foodborne diseases. We performed the antibiotic susceptibility and molecular characterization of S. aureus from milk samples of dairy cows in Manhiça District. We observed a high frequency of S. aureus (41%, 58/143), in which 71% (41/58) were from commercial farms and 29% (17/58) from smallholder farms. Half of the isolates (50%, 29/58) were resistant to at least one antibiotic, with higher rates of resistance to penicillin (43%, 25/58), followed by tetracycline (16%, 9/58). Multidrug-resistant and methicillin-resistant S. aureus isolates were rare (5%, 3/58 and 3%, 2/58, respectively). The genetic diversity was low, with predominance of human-adapted strains being: ST1/CC1-t5388 (78%) and ST152-t1299 (10%), followed by ST8/CC8-t1476 (5%) and ST5/CC5-t002 (3%) and lastly, ST508/CC45-t331 and ST152-t355, with 2% each. The Panton–Valentine leukocidin (PVL) gene was detected among 14% (8/58) of the isolates, while genes encoding staphylococcal enterotoxins were scarce (3%, 2/58). Our findings revealed a high frequency of S. aureus, with high rates of resistance to the antibiotics commonly used in veterinary and human medicine. Further investigations focusing on the molecular epidemiology of S. aureus from cattle and farmers will provide detailed insights on the genetic relatedness between the strains.

Molecular fingerprinting of bovine mastitis-associated Staphylococcus aureus isolates from India

Staphylococcus aureus is a major etiological agent of clinical and subclinical bovine mastitis. Owing to the mostly backyard dairy practices, we hypothesized that genetic diversity among mastitis-associated S. aureus from India would be high, and investigated 166 isolates obtained mostly from the Southern State of Karnataka, but also from a few other states. The results revealed (a) 8 to 13 fragments in pulsed-field gel electrophoresis (PFGE), forming 31 distinct patterns, and (b) 34 spa types, of which three (t17680, t18314, and t18320) were newly identified. Multi-locus sequencing typing (MLST) identified 39 sequence types (STs), with ST2454 (34.4%) and ST2459 (24%) being the most commonly represented, which clustered to clonal complexes (CC) CC9 and CC97, respectively; 12 STs were newly identified. Thirty-four (20.5%) of the 166 isolates displayed oxacillin resistance. On the other hand, whereas none were mecC⁺, 44 (26.5%) isolates were mecA⁺, with a predominance of SCCmecIVb (26/32 isolates, others being untypeable); 24 isolates (14.46%) were oxacillin-susceptible methicillin-resistant S. aureus (OS-MRSA; mecA⁺ but OS). Integrated analysis revealed that CC9-ST2454- and CC97-ST2459-SCCmecIVb were the predominant MRSA, although the distribution of CC9 and CC97 was similar between methicillin-resistant and -susceptible isolates. By PCR, 56.25%, 28.75% and 47.5% of the 166 isolates were positive for hlg, tsst and pvl genes, respectively. Our results, for the first time describe the application of a combination of various molecular methods to bovine mastitis-associated S. aureus isolates from India, corroborate the worldwide distribution of CC97 and CC9, and suggest pathogenic potential of the isolates.

A meta-analysis of the global prevalence of methicillin-resistant Staphylococcus aureus (MRSA) isolated from clinical and subclinical bovine mastitis

AIMS

This meta-analysis aims to assess the point prevalence of methicillin-resistant Staphylococcus aureus (MRSA) isolated from bovine mastitis cases at the global level.

METHODS AND RESULTS

Several electronic databases were searched for relevant publications (PubMed, EMBASE, Web of Knowledge and Cochrane Library). Heterogeneity between studies was assessed using the Cochrane Q test and I² test statistics based on the random-effect model. The potential sources of between-study heterogeneity were evaluated using subgroup analysis and meta-regression. Sensitivity and publication bias analyses were performed. Sixty-six studies with a total of 77,644 mastitis cases were eligible and included in the analysis. The overall pooled prevalence of MRSA was 4·30% (95% CI: 3·24-5·50) with a significant heterogeneity (I²  = 97·48%, p < 0·001). In the subgroup analysis by region, the highest prevalence was found in Asia (6·47%, 95% CI: 4·33-8·97), and the lowest prevalence was reported in Europe (1·18%, 95% CI: 0·18-2·83). The pooled prevalence was significantly higher in clinical mastitis and cases published during 2016-2020.

CONCLUSIONS

The results of this study suggest that there is a lower prevalence of MRSA in bovine mastitis. However, its prevalence increased in the past 4 years. Therefore, continuous surveillance is urgently required for monitoring the dissemination of these clinically important bacteria.

SIGNIFICANCE OF THE STUDY

To our knowledge, this is the first meta-analysis to estimate the global prevalence of MRSA isolated from bovine mastitis cases.

Antimicrobial resistance and genotyping of Staphylococcus aureus obtained from food animals in Sichuan Province, China

Background

Staphylococcus aureus (S. aureus), especially methicillin-resistant Staphylococcus aureus (MRSA), is considered a common zoonotic pathogen, causing severe infections. The objective of this study was to investigate the antimicrobial susceptibility, resistance genes and molecular epidemiology among MRSA and methicillin-susceptible Staphylococcus aureus (MSSA) isolated from food animals in Sichuan Province, China.

Methods

This study was conducted on 236 S. aureus isolates. All isolates were subjected to antimicrobial susceptibility testing by using a standard microbroth dilution method. The Polymerase Chain Reaction (PCR) was performed to identify genes encoding the β-lactams resistance (blaZ, mecA), macrolides (ermA, ermB, ermC) and aminoglycosides (aacA-aphD). The molecular structures and genomic relatedness of MRSA isolates were determined by staphylococcal chromosome cassette mec (SCCmec) typing and pulsed-field gel electrophoresis (PFGE), respectively.

Results

Among 236 isolates, 24 (10.17 %) were recognized as MRSA. MRSA isolates showed different resistance rates to 11 antimicrobials ranging from 33.33 to 100 %, while for MSSA isolates the rates varied from 8.02 to 91.51 %. Multi-drug resistance phenotype was found in all MRSA isolates. The ermC gene encoding macrolides-lincosamides-streptogramin B was the most prevalent gene detected in 87.29 % of the S. aureus isolates, followed by ermB (83.05 %), blaZ (63.98 %), aacA-aphD (44.07 %), ermA (11.44 %) and mecA (11.02 %) genes. The prevalence of resistance genes in MRSA isolates was significantly higher than that of MSSA. Regarding the molecular morphology, SCCmec III (12/24, 50 %) was the most common SCCmec type. Furthermore, the PFGE typing showed that 24 MRSA were divided into 15 cluster groups (A to O), the major pulsotype J encompassed 25 % of MRSA isolates.

Conclusions

The S. aureus isolates from food animals in Sichuan province of China have severe antimicrobials resistance with various resistance genes, especially MRSA isolates. Additionally, the genetic pool of MRSA isolates is diverse and complex, and further investigation is necessary.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-021-02884-z.

Prevalence and distribution of multilocus sequence types of Staphylococcus aureus isolated from bulk tank milk and cows with mastitis in Pennsylvania

A total of 163 S. aureus isolates; 113 from mastitic milk (MM) and 50 from bulk tank milk (BTM) (2008, 2013–2015) submitted for bacteriologic analysis at the Penn State Animal Diagnostic Laboratory were examined for their phenotypic and genotypic characteristics. Multi-locus sequence typing (MLST) analysis identified 16 unique sequence types (STs) which belonged to eight clonal complexes (CCs). Majority of the isolates were variants of CC97 (68.7%) and CC151 (25.1%). CC97 comprised of seven STs, of which two were new STs (ST3273, ST3274), while CC151 comprised of three STs of which ST3272 was identified for the first time. Several farms had more than one ST type that were either members of the same clonal complex or unrelated STs. On one farm, six different STs of both categories were seen over the years within the farm. It was observed that ST352 and ST151 were the two main clonal populations in cattle not only in Pennsylvania but also globally. Most isolates were susceptible to all the antibiotics evaluated. 6.7% of isolates showed resistance to vancomycin and penicillin. Two isolates of ST398 showed multidrug resistance (>3 antibiotics) against clindamycin, erythromycin, tetracycline, and penicillin. It was noted that 59 of 163 (36.2%) isolates encoded for enterotoxigenic genes. Enterotoxin genes seg/sei accounted for ~85% of enterotoxin positive isolates. Toxic shock syndrome gene tsst-1 alone was positive in two isolates (ST352, ST 2187). 97.5% of CC151 isolates were enterotoxin seg/sei positive. Most isolates were positive for lukED (95%) and lukAB (96.3%) leukotoxin genes. Bovine specific bi-component leucocidin lukMF’ was present in 54% of isolates. A prominent observation of this study was the explicit association of lukMF’ with lineages ST151 and ST352. In conclusion, the findings of the study, suggest that small number of S. aureus STs types (ST352, ST2187, ST3028, and ST151) are associated with majority of cases of bovine mastitis in Pennsylvania dairy farms. It was observed that one ST of S. aureus predominated in the herd and this ST can coexist with several other ST types of S. aureus strains. When STs were interpreted along with virulence, leucocidin genes and antimicrobial resistance, ST-variants allowed better interpretation of the S. aureus molecular epidemiologic findings specifically for tracing recurrence or persistence of infections in cow over time, among cows in the herd, and between herds in Pennsylvania.

Antibiotic resistance and genotyping of mecA-positive methicillin-resistant Staphylococcus aureus (MRSA) from milk and nasal carriage of dairy water buffaloes (Bubalus bubalis) in the Philippines

Objective

Mastitis is considered as an economically important disease of dairy buffaloes in Asia. This study examined the mastitis milk and nasal swab samples for the detection and genotyping of methicillin-resistant Staphylococcus aureus (MRSA) in water buffaloes.

Materials and Methods

Staphylococcus aureus was identified based on biochemical tests and Polymerase Chain Reaction (PCR) detection of nuc gene, whereas MRSA on mecA gene. The disc diffusion test was used to determine the antibiotic resistance and staphylococcal cassette chromosome mec (SCCmec), spa, and multilocus sequence typing for the genotyping of isolates.

Results

Staphylococcus aureus was detected on 39/93 milk (41.94%) and 27/384 nasal swab (7.03%) samples. However, only nine isolates (23.08%) harbored the mecA gene from milk samples and three isolates (11.11%) from the nasal carriage. All MRSA isolates exhibited resistance to cefoxitin and penicillin, whereas 50% were found resistant to clindamycin. All these isolates were found susceptible to sulfa-trimethoprim and chloramphenicol, whereas the majority of the isolates were susceptible to gentamicin, ciprofloxacin, tetracycline, and rifampicin. The SCCmec types of the MRSA isolates were type IVc (50.00%), type II (8.33%), type I (8.33%), and non-typeable (33.33%). The spa types and sequence type (ST) identified were t019 (ST30), t701 (ST1649), t311 (ST5), t657 (ST1148), t015 (ST508), t1939 (ST12), t800 (ST9), t091 (ST2454), t138 (ST5991), and t1642 (ST5992).

Conclusion

Milk and nasal swab samples from dairy water buffaloes were found positive for MRSA. The MRSA isolates were still susceptible to most antibiotics tested. Moreover, the genotypes of some MRSA isolates were found similar to some human MRSA strains, suggesting a possible human to animal transmission.

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

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

In vitro Antibiotic Susceptibility, Virulence Genes Distribution and Biofilm Production of Staphylococcus aureus Isolates from Bovine Mastitis in the Liaoning Province of China

Purpose

The aim of this study was to identify the subtype, characterize the antimicrobial resistance, determine the virulence gene distribution, and analyze the biofilm production of Staphylococcus aureus isolates from bovine mastitis milk samples in the Liaoning Province of China.

Materials and Methods

In total, 56 Staph. aureus isolates were collected and identified in this study; the isolates were divided into different spa types based on the sequence of the polymorphic X region of the spa gene. Additionally, antimicrobial susceptibility was investigated using the broth microdilution method, and 18 virulence genes were detected using PCR. Biofilm formation was measured by spectrophotometry with crystal violet staining and observed using confocal laser scanning microscopy.

Results

There were 12.12% (56/462) milk samples that were positive for Staph. aureus. These isolates were nonsusceptible to sulfamethoxazole (100%), penicillin (76.9%), daptomycin (76.79%), clindamycin (69.64%), and oxacillin (60.71%); however, the majority of the isolates (80.4%) were susceptible to amoxicillin/clavulanate. The predominant virulence genes encoded the cytotoxins, hla (94.64%) and hlb (89.29%), and the adhesion factors clfA (89.29%), clfB (89.29%), and fnbB (80.36%). Comparatively, virulence genes related to other adhesion factors such as cna (8.93%) and enterotoxins, such as seg (26.79%), sea (16.07%), seb (7.14%), and sec (7.14%) were detected at relatively lower rates. The following eight spa types were identified: t267 (35.84%), t730 (22.64%), t518 (15.09%), t1190 (11.32%), t1456 (9.43%), t224 (1.88%), t9129 (1.88%), and t177 (1.88%). The highest biofilm production was observed for t267. Staph. aureus exhibited various patterns of biofilm formation, with the biofilm often being associated with a tower-shaped structure or a thicker biofilm.

Conclusion

Our results indicated that Staph. aureus isolates from dairy cows with mastitis in the Liaoning Province of China were non-susceptible to sulfamethoxazole, penicillin, daptomycin, oxacillin, and clindamycin. Additionally, the most prevalent subtype was t267, which displayed resistance to multiple antimicrobial agents and harbored several virulence genes, including clfA, clfB, fnbB, hla, and hlb.

Risk Factors for the Occurrence of Methicillin-Resistant Staphylococcus aureus in Dairy Herds: An Update

In dairy cows, Staphylococcus aureus is a major mastitis pathogen and methicillin-resistant S. aureus (MRSA) has been reported from dairy farms around the world. The risk of foodborne zoonotic infections with bovine MRSA strains seems to be low since MRSA prevalence is low in dairy herds and milk is commonly heat treated before consumption. However, bovine mastitis caused by MRSA is an important issue in veterinary medicine since treatment options with non-β-lactam antibiotics are limited. For the development of effective MRSA prevention strategies, it is necessary to know which factors increase the risk for MRSA transmission into and within dairy herds. Therefore, the aim of this review is to summarize the risk factors for the occurrence of MRSA in dairy herds and to identify the respective knowledge gaps. MRSA was more frequently detected in conventional dairy farms than in organic farms and in larger farms than in smaller farms. Dairy farms housing pigs along with cattle are more frequently affected by MRSA. Moreover, humans carrying MRSA can probably infect dairy cows. Consequently, pigs and humans may introduce new MRSA strains into dairy herds. MRSA transmission within dairy herds was associated with improper milking hygiene procedures. Furthermore, methicillin-resistant coagulase-negative staphylococci (MR-CoNS) were repeatedly isolated from dairy farms. This is an important issue since MR-CoNS may transfer resistance genes to S. aureus. The role of antimicrobial exposure as a risk factor for the occurrence of MRSA within dairy herds needs to be further investigated.