Genotyping of methicillin-resistant Staphylococcus aureus (MRSA) isolated from milk and dairy products in South Italy

Prevalence and Phage-Based Biocontrol of Methicillin-Resistant Staphylococcus aureus Isolated from Raw Milk of Cows with Subclinical Mastitis in Vietnam

S. aureus, particularly methicillin-resistant S. aureus, has been recognized as a main cause of bovine mastitis and food poisoning. This study investigated the prevalence, antibiotic resistance, and phage-based biocontrol of S. aureus and methicillin-resistant S. aureus isolated from raw milk of cows with subclinical mastitis. The results showed that the prevalence of S. aureus and methicillin-resistant S. aureus was 12% (48/400) and 1.5% (6/400), respectively. The S. aureus isolates were highly resistant to penicillin (72.92%), erythromycin (43.75%), and tetracycline (39.58%). Out of 48 S. aureus isolates, 6 were identified as methicillin-resistant strains. Among them, one isolate was found to harbor the sea gene. A total of 5 phages were recovered from 50 pork and 50 chicken meat samples, 1 from pork and 4 from chicken meat samples. Phage PSA2 capable of lysing all 6 methicillin-resistant isolates was selected for characterization. The use of phage PSA2 completely inactivated methicillin-resistant S. aureus SA33 in raw milk at both 24 °C and 4 °C, indicating its potential as a promising antibacterial agent in controlling methicillin-resistant S. aureus in raw milk and treating bovine mastitis.

Methicillin-Resistant Staphylococcus aureus (MRSA) in Dairy Products and Bulk-Tank Milk (BTM)

In order to contribute to an assessment of the role of food in the risks of transmission of methicillin-resistant Staphylococcus aureus (MRSA), a review was undertaken of research on this microorganism in milk and dairy products published from January 2001 to February 2024. A total of 186 publications were selected, 125 for dairy products and 61 for bulk-tank milk (BTM). MRSA was detected in 68.8% of the research into dairy products and 73.8% of investigations relating to BTM, although in most studies the prevalence was less than 5%. Of the set of S. aureus strains isolated, approximately 30% corresponded to MRSA. The foods most extensively contaminated with this microorganism were raw milk and some types of soft cheese. Determination of the mecA gene on its own is known not to suffice for the detection of all MRSA strains. The great diversity of techniques used to study MRSA in milk and dairy products made it difficult to draw comparisons between studies. It would thus be advisable to develop a standardized protocol for the study of this microorganism in foods.

Antibiotic Resistance Profiles and MLST Typing of Staphylococcus Aureus Clone Associated with Skin and Soft Tissue Infections in a Hospital of China

Objective

To analyze the antibiotic resistance profile, virulence genes, and molecular typing of Staphylococcus aureus (S. aureus) strains isolated in skin and soft tissue infections at the First Affiliated Hospital, Gannan Medical University, to better understand the molecular epidemiological characteristics of S. aureus.

Methods

In 2023, 65 S. aureus strains were isolated from patients with skin and soft tissue infections. Strain identification and susceptibility tests were performed using VITEK 2 and gram-positive bacteria identification cards. DNA was extracted using a DNA extraction kit, and all genes were amplified using polymerase chain reaction. Multilocus sequence typing (MLST) was used for molecular typing.

Results

In this study, of the 65 S. aureus strains were tested for their susceptibility to 16 antibiotics, the highest resistance rate to penicillin G was 95.4%. None of the staphylococcal isolates showed resistance to ceftaroline, daptomycin, linezolid, tigecycline, teicoplanin, or vancomycin. fnbA was the most prevalent virulence gene (100%) in S. aureus strains isolated in skin and soft tissue infections, followed by arcA (98.5%). Statistical analyses showed that the resistance rates of methicillin-resistant S. aureus isolates to various antibiotics were significantly higher than those of methicillin-susceptible S. aureus isolates. Fifty sequence types (STs), including 44 new ones, were identified by MLST.

Conclusion

In this study, the high resistance rate to penicillin G and the high carrying rate of virulence gene fnbA and arcA of S.aureus were determine, and 44 new STs were identified, which may be associated with the geographical location of southern Jiangxi and local trends in antibiotic use. The study of the clonal lineage and evolutionary relationships of S. aureus in these regions may help in understanding the molecular epidemiology and provide the experimental basis for pathogenic bacteria prevention and treatment.

Characterization of resistance and virulence factors in livestock-associated methicillin-resistant Staphylococcus aureus

The study investigated the economic concerns associated with livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) in livestock (cow), examining its connection to severe infections, antimicrobial resistance (AMR), and virulence factors. The research, conducted in Edo State, Nigeria, analyzed 400 samples (200 rectal and 200 nasal swabs) collected between March 2018 and February 2019. MRSA prevalence was identified using conventional culture-based methods and polymerase chain reaction (PCR) techniques, revealing 63.5% (n = 254) for Staphylococcus aureus and 55% (n = 220) for MRSA. Of the 76 mecA-positive MRSA isolates, 64.5% (n = 49) exhibited multidrug resistance (MDR) while the remaining were sensitive to specific antimicrobials. Key virulence genes, such as PVL (81.6%; n = 62) and tsst-1 (44.7%; n = 34), were prevalent, along with AMR genes like mecC, tetM, ermA, ermC, vanA, and vanC. Staphylococcal chromosomal cassette mec (SCCmec) typing identified different types, notably II, IVa, and IVb. Biofilm formation, a crucial virulence factor varied in strength, is associated with icaA and icaB genes (p < 0.01). The findings highlighted substantial AMR and biofilm-forming capacity within LA-MRSA isolates, emphasizing the importance of ongoing surveillance for informed treatment strategies, AMR policies, and control measures against MDR staphylococcal infections.

Growth of methicillin-resistant Staphylococcus aureus during raw milk soft cheese-production and the inhibitory effect of starter cultures

The consumption of raw milk or raw milk products might be a potential risk factor for the transmission of methicillin-resistant Staphylococcus aureus (MRSA). Therefore, we studied MRSA growth during raw milk soft cheese-production. Furthermore, we investigated the inhibitory effect of four starter cultures (Lactococcus lactis, Lacticaseibacillus rhamnosus, Lactiplantibacillus plantarum, Lactobacillus helveticus) on the growth of MRSA in a spot-agar-assay and in raw milk co-culture following a cheesemaking temperature profile. During the initial phases of raw milk cheese-production, MRSA counts increased by 2 log units. In the ripening phase, MRSA counts only dropped slightly and remained high up to the end of the storage. Comparable MRSA counts were found in the rind and core and strain-specific differences in survival were observed. In the spot-agar-assay, all four starter cultures showed strong or intermediate inhibition of MRSA growth. In contrast, in raw milk, only Lactococcus lactis strongly inhibited MRSA, whereas all other starter cultures only had minor inhibitory effects on MRSA growth. Our results indicate that MRSA follow a similar growth pattern as described for other S. aureus during raw milk soft cheese-production and illustrate the potential use of appropriate starter cultures to inhibit MRSA growth during the production of raw milk cheese.

Methicillin-resistant staphylococci in clinical bovine mastitis: occurrence, molecular analysis, and biofilm production

Staphylococcus aureus is an important pathogen that causes mastitis in cattle, and the emergence of methicillin-resistant S. aureus (MRSA) poses a threat to veterinary and human medicine. The aims of the study were to investigate the prevalence of MRSA and methicillin-resistant coagulase-negative staphylococci (MR-CoNS) isolated from clinical mastitis, their ability to form biofilms, and the antimicrobial susceptibility of S. aureus strains. In addition, the Staphylococcal Cassette Chromosome mec (SCCmec) type, spa type and the presence of Panton-Valentine Leucocidin in MRSA were evaluated. A total of 326 staphylococcal strains were screened by multiplex-PCR for S. aureus and Staphylococcus intermedius group (SIG) identification. The S. aureus strains (n = 163) were subjected to phenotypic testing for antimicrobial susceptibility and biofilm formation. Molecular analysis was performed on MRSA mecA-positive strains. Of 163 S. aureus isolates, 142 strains (87.1%) were resistant to at least one antibiotic, and all 19 MRSA strains were resistant to at least four out of five antibiotics tested. All S. aureus strains harboured the icaA gene and were biofilm producers. Nineteen MR-CoNS strains were also isolated. The most prevalent spa types among MRSA were t001 (57.9%) and t037 (31.6%), while one MRSA was type t008 and one was type t041. Most MRSA were SCCmec type I (63.2%) and III (31.6%) and only one strain was type IV. None of the MRSA isolates had the PVL gene. The prevalence of multidrug-resistant S. aureus in bovine mastitis is a serious concern. The finding of MRSA with spa types predominant in humans and infrequent in Italian cows and with SCCmec infrequently found in bovine milk or cheese suggest a human origin of these strains. The ability of MRSA and MR-CoNS involved in bovine mastitis to be transferred to humans and vice versa poses a public health concern.

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.

Antimicrobial resistance and molecular typing of Staphylococcus aureus isolates from raw milk in Hunan Province

Background

Staphylococcus aureus is one of the most important foodborne pathogens in the world and the main cause of dairy cow mastitis. Few studies have investigated the epidemic pedigree of S. aureus of bovine origin in Hunan, China. Therefore, we aimed to analyze the capsular polysaccharides (CP), molecular typing, and antibiotic resistance characteristics of S. aureus isolated from raw milk of dairy farms in Hunan Province.

Methods

Between 2018 and 2022, 681 raw milk samples were collected from dairy cows from farms in Changsha, Changde, Shaoyang, Yongzhou, and Chenzhou in Hunan Province. S. aureus was isolated from these samples, and the isolates were subjected to molecular typing, CP typing, and determination of antibiotic resistance through broth dilution and polymerase chain reaction (PCR).

Results

From 681 raw milk samples, 76 strains of S. aureus were isolated. The pathogenicity of 76 isolates was determined preliminarily by detecting cp5 and cp8 CP genes. Eighteen types of antimicrobial resistance phenotypes of 76 S. aureus strains were detected by the broth dilution method, and 11 kinds of related resistance genes were amplified by PCR. The S. aureus isolates had CP5 (42.10%) and CP8 (57.89%). S. aureus had a multiple antimicrobial resistance rate of 26.75%. The isolated strains had the highest resistance rate to penicillin (82.89%) and showed varying degrees of resistance to other drugs, but no isolate showed resistance to doxycycline. The 76 isolates all carried two or more antibiotic resistance genes, with a maximum of eight antibiotics resistance genes. FemB was detected in all isolates, but none of isolates carried vanA, ermA, or glrA. The 76 isolates were divided into 22 sequence types (ST) and 20 spa types by MLST and spa typing, and the number of t796-ST7 (n = 15) isolates was the highest, which may be the major epidemic strain of multidrug-resistant S. aureus.

Conclusion

The present findings indicate the need to increase production of the CP8 S. aureus vaccine in Hunan Province and strengthen resistance monitoring of t796-ST7 isolates with the prevalent molecular type of multi-drug resistant strains. The use of β-lactam, macrolides, and lincosamides should be reduced; doxycycline, sulfonamides, and glycopeptides could be appropriately added to veterinary antibiotics to treat infectious diseases in dairy cows.

Occurrence, Antibiotic Susceptibility, Biofilm Formation and Molecular Characterization of Staphylococcus aureus Isolated from Raw Shrimp in China

The aim of this study was to determine the prevalence and characterization of Staphylococcus aureus isolated from 145 shrimp samples from 39 cities in China. The results show that 41 samples (28%) from 24 cities were positive, and most of the positive samples (39/41, 95.1%) were less than 110 MPN/g. Antimicrobial susceptibility testing showed that only seven isolates were susceptible to all 24 antibiotics, whereas 65.1% were multidrug-resistant. Antibiotic resistance genes that confer resistance to β-lactams, aminoglycosides, tetracycline, macrolides, lincosamides and streptogramin B (MLSB), trimethoprim, fosfomycin and streptothricin antibiotics were detected. All S. aureus isolates had the ability to produce biofilm and harbored most of the biofilm-related genes. Genes encoding one or more of the important virulence factors staphylococcal enterotoxins (sea, seb and sec), toxic shock syndrome toxin 1 (tsst-1) and Panton-Valentine leukocidin (PVL) were detected in 47.6% (30/63) of the S. aureus isolates. Molecular typing showed that ST15-t085 (27.0%, 17/63), ST1-t127 (14.3%, 9/63) and ST188-t189 (11.1%, 7/63) were the dominant genetic types. The finding of this study provides the first comprehensive surveillance on the incidence of S. aureus in raw shrimp in China. Some retained genotypes found in this food have been linked to human infections around the world.

Antimicrobial Usage and Detection of Multidrug-Resistant Staphylococcus aureus: Methicillin- and Tetracycline-Resistant Strains in Raw Milk of Lactating Dairy Cattle

Staphylococcus aureus is a prominent cause of food-borne diseases worldwide. Enterotoxigenic strains of this bacteria are frequently found in raw milk, and some of these strains are resistant to antimicrobials, posing a risk to consumers. The main objectives of this study were to determine the antimicrobial resistance pattern of S. aureus in raw milk and to detect the presence of mecA and tetK genes in it. A total of 150 milk samples were obtained aseptically from lactating cattle, including Holstein Friesian, Achai, and Jersey breeds, maintained at different dairy farms. The milk samples were checked for the presence of S. aureus, and it was detected in 55 (37%) of them. The presence of S. aureus was verified by culturing on selective media, gram staining, and performing coagulase and catalase tests. Further confirmation was performed through PCR with a species-specific thermonuclease (nuc) gene. Antimicrobial susceptibility testing of the confirmed S. aureus was then determined by using the Kirby-Bauer disc diffusion technique. Out of the 55 confirmed S. aureus isolates, 11 were determined to be multidrug-resistant (MDR). The highest resistance was found to penicillin (100%) and oxacillin (100%), followed by tetracycline (72.72%), amikacin (27.27%), sulfamethoxazole/trimethoprim (18.18%), tobramycin (18.18%), and gentamycin (9.09%). Amoxicillin and ciprofloxacin were found to be susceptible (100%). Out of 11 MDR S. aureus isolates, the methicillin resistance gene (mecA) was detected in 9 isolates, while the tetracycline resistance gene (tetK) was found in 7 isolates. The presence of these methicillin- and tetracycline-resistant strains in raw milk poses a major risk to public health, as they can cause food poisoning outbreaks that can spread rapidly through populations. Our study concludes that out of nine empirically used antibiotics, amoxicillin, ciprofloxacin, and gentamicin were highly effective against S. aureus compared to penicillin, oxacillin, and tetracycline.

Repeated Emergence of Variant TetR Family Regulator, FarR, and Increased Resistance to Antimicrobial Unsaturated Fatty Acid among Clonal Complex 5 Methicillin-Resistant Staphylococcus aureus

Resistance-nodulation-division (RND) superfamily efflux pumps promote antibiotic resistance in Gram-negative pathogens, but their role in Gram-positive pathogens, including methicillin-resistant Staphylococcus aureus (MRSA) is undocumented. However, recent in vitro selections for resistance of S. aureus to an antimicrobial fatty acid, linoleic acid, and an antibiotic, rhodomyrtone, identified H121Y and C116R substitution variants, respectively, in a TetR family regulator, FarR, promoting increased expression of the RND pump FarE. Hypothesizing that in vivo selection pressures have also promoted the emergence of FarR variants, we searched available genome data and found that strains with FarR^H121Y from human and bovine hosts have emerged sporadically in clonal complexes (CCs) CC1, CC30, CC8, CC22, and CC97, whereas multiple FarR variants have occurred within CC5 hospital-associated (HA)-MRSA. Of these, FarR^E160G and FarR^E93EE were exclusive to CC5, while FarR^C116Y, FarR^P165L, and FarR^G166D also occurred in nonrelated CCs, primarily from bovine hosts. Within CC5, FarR^C116Y and FarR^G166D strains were polyphyletic, each exhibiting two emergence events. FarR^C116Y and FarR^E160G were individually sufficient to confer increased expression of FarE and enhanced resistance to linoleic acid (LA). Isolates with FarR^E93EE were most closely related to S. aureus N315 MRSA and exhibited increased resistance independently of FarR^E93EE. Accumulation of pseudogenes and additional polymorphisms in FarR^E93EE strains contributed to a multiresistance phenotype which included fosfomycin and fusidic acid resistance in addition to increased linoleic acid resistance. These findings underscore the remarkable adaptive capacity of CC5 MRSA, which includes the polyphyletic USA100 lineage of HA-MRSA that is endemic in the Western hemisphere and known for the acquisition of multiple resistance phenotypes.

CRISPR/Cas12a-based magnetic relaxation switching biosensor for nucleic acid amplification-free and ultrasensitive detection of methicillin-resistant Staphylococcus aureus

Herein, we develop a CRISPR/Cas12a-based magnetic relaxation switching (C-MRS) biosensor for ultrasensitive and nucleic acid amplification-free detection of methicillin-resistant Staphylococcus aureus (MRSA) in food. In this biosensor, mecA gene in MRSA was recognized by CRISPR-RNA, which will activate the trans-cleavage activity of Cas12a and release the fastened alkaline phosphatase (ALP) on the particle. The freed ALP can then use to hydrolyze substrate to produce ascorbic acid that trigger the click reaction between magnetic probe. The transverse relaxation time of the unbound magnetic probe can be measured for signal readout. By incorporating collateral activity of CRISPR/Cas12a, on-particle rolling circle amplification, and ALP-triggered click chemistry into background-free MRS, as low as 16 CFU/mL MRSA can be detected without any nucleic acid pre-amplification, which avoids carryover contamination, but without compromising sensitivity. Moreover, this C-MRS biosensor could distinguish 0.01% target DNA from the single-base mutant. Recovery in eggs, milk and pork ranged from 75% to 112%, 82%-104%, and 81%-91%, respectively, revealing its satisfactory accuracy and applicability in the complex food matrix. The developed C-MRS biosensor fleshes out the CRISPR toolbox for food safety and provides a new approach for the sensitive and accurate detection of foodborne drug-resistant bacteria.

Prevalence, Contamination Level, and Associated Factors of Methicillin-Resistant Staphylococcus aureus in Raw Cow Milk at Selected Districts of Gamo Zone, Southern Ethiopia

Staphylococcus aureus is pathogenic bacterium contaminating milk and milk products causing bacterial food poisoning. In the current study sites, there is no information on methicillin-resistant Staphylococcus aureus. Thus, the current study sought to assess the risk factors that contribute to the contamination of raw cow milk, the bacterial load, and the prevalence of methicillin-resistant Staphylococcus aurous. A cross-sectional study was conducted, January to December, 2021, on randomly selected 140 milk samples from selling point of Arba Minch Zuria and Chencha districts. Fresh milk samples were processed and tested for bacterial load, bacterial isolation, and methicillin susceptibility patterns. Questionnaire survey was conducted on 140 producers and collectors to assess hygienic factors attributed to contamination of raw cow milk with Staphylococcus aureus. The overall prevalence of S. aureus was 42.1% (59/140) (95% confidence interval (CI): 34.80-51.40%). About 15.6% (22/140) of the milk samples assessed had the viable count and total S. aureus count higher than 5log cfu/mL with 5.3 + 1.68 and 1.36 + 1.7log cfu/ml^-1 bacterial loads, respectively. The rate of isolation of S. aureus was significantly high in milk from highland than lowland (p=0.030). The multivariable logistic regression revealed that educational status (OR: 6.00; 95% CI: 4.01-8.07), picking one's nose while working on milk (OR: 1.41; 95% CI: 0.54-2.25), cleaning the milk can (OR: 4.5; 95% CI: 2.61-5.17), hand washing activities (OR: 3.4; 95% CI: 1.670-6.987), check for abnormal milk (OR: 2; 95% CI: 1.55-2.75), and container for milk (OR: 3; 95% CI: 0.12-0.67) were risk factors significantly associated with the occurrence of S. aureus in milk. In conclusion, the highest rate of resistance was observed to ampicillin (84.7%) and cefoxitin (76.3%). All isolates are resistant to at least two types of antimicrobial drugs, while 65.0% of the isolates were found to be multidrug-resistant. The higher prevalence, high load, and antimicrobial resistance of S. aureus indicate the higher public health risk due to the widespread consumption of raw milk in the area. Furthermore, consumers in the study area should be aware of the risks associated with consuming raw milk.

Zinc oxide nanoparticles reduce biofilm formation, synergize antibiotics action and attenuate Staphylococcus aureus virulence in host; an important message to clinicians

BACKGROUND

Biofilm-related infections are difficult to be treated because of higher resistance to antimicrobial agents. Current study aims to characterize the influence of zinc oxide nanoparticles (ZnO-NPs) on both S. aureus susceptibility to antibiotics and pathogenesis.

METHODS

The influence of ZnO-NPs on biofilm formation by S. aureus was characterized by the crystal violet and tube assay. The synergistic effect of ZnO-NPs in combination with antibiotics on S. aureus was characterized using the checkerboard method. The effect of ZnO-NPs on S. aureus cell surface hydrophobicity and blood hemolysis was investigated. RT-qPCR was used to investigate the effect of ZnO-NPs on the expression of biofilm related genes (icaA, icaR and sarA), katA and sigB. The impact of ZnO-NPs on S. aureus pathogenesis was evaluated using mice infection model.

RESULTS

ZnO-NPs exhibited a good antibiofilm activity against S. aureus. The findings indicate a synergistic antibiofilm effect of combination between ZnO-NPs and tested antibiotics. ZnO-NPs were capable of decreasing S. aureus cell surface hydrophobicity which could account for observed decrease in bacterial biofilm forming capacity. Moreover, ZnO-NPs-treated bacteria exhibited a significant decrease in blood hemolysis relative to control untreated S. aureus. The expression of biofilm related genes was significantly repressed in ZnO-NPs treated bacteria as compared to untreated cells. Finally, the effect of ZnO-NPs on S. aureus pathogenesis was investigated using mice infection model where ZnO-NPs accelerated healing of wounds in mice as compared to control untreated mice.

CONCLUSIONS

Present data support the efficiency of ZnO-NPs as antibiofilm agent in treatment of S. aureus infections. This study recommends the incorporation of ZnO-NPs as adjuvant with other antibiotics targeting S. aureus based on the promising findings obtained herein in order to control infection with this pathogen.

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.

Genetic Characterization and Antimicrobial-Resistant Profiles of Staphylococcus aureus Isolated from Different Food Sources

This study determined the prevalence of Staphylococcus aureus in food of animal origin, investigated its antimicrobial susceptibility profiles and antimicrobial-resistant genes encoding resistance to methicillin (mecA), penicillin (blaZ), and vancomycin (vanA). Two hundred and sixty food samples, including raw retail milk, meat, and meat products, were obtained from local retail shops in Mansoura city, Egypt. The overall prevalence of S. aureus in the total examined food samples was 32.69% (85/260). Methicillin-resistant S. aureus (MRSA) was identified in 11.15% (29/260) of the tested food samples. S. aureus indicated a high resistance to nalidixic acid, penicillin, ampicillin, cefuroxime, trimethoprim/sulfamethoxazole, and azithromycin. The multiple antibiotic resistance (MAR) rate was 89.4% of the total S. aureus isolates, and MARindex ranges from 0.05-0.64. Genotypically, mecA and blaZ genes were identified in a percentage of 34.11% and 82.35%, respectively, while no isolates harbored the vanA gene. The presence of MAR S. aureus particularly, MRSA in food samples, is of great concern and represents a possible threat to the community. Therefore, the study's findings highlight the importance of establishing vigilant food safety practices for food handlers to inhibit the transmission of S. aureus through the food chain to reduce public health risks.

Relevant safety aspects of raw milk for dairy foods processing

The concern with food safety in the milk chain begins with the quality of the raw milk. Due to the health hazard that this food can carry when contaminated, the focus of studies has turned to microbiological and chemical contaminants that may be present in raw milk. There is an essential concern about conventional pathogens (Shiga toxin-producing Escherichia coli, Salmonella spp., Listeria monocytogenes, Campylobacter spp., Salmonella spp., and coagulase-positive Staphylococcus spp.) and emerging pathogens (Arcobacter butzleri, Yersinia enterocolitica, Mycobacterium avium ssp. paratuberculosis, Helicobacter pylori, and Cronobacter sakazakii) found in raw milk and dairy products. In addition, a growing public health issue has been raised regarding antimicrobial-resistant pathogens and commensal strains found in milk and dairy products. The antibiotic residues in milk can also damage health, such as allergies, and cause technological problems in dairy products processing. This health issue extends to other chemical contaminants such as heavy metals, pesticides, polycyclic aromatic hydrocarbons, melamine, dioxins, polychlorinated biphenyls, plasticizers, and additives in milk and dairy products. Other chemical substances formed by microorganisms are also of high importance, such as biogenic amines and mycotoxins. Therefore, this chapter aimed to revise and discuss relevant biological and chemical risks to ensure the safety and quality of raw milk and dairy products.

Antimicrobial Susceptibility, and Molecular Characterization of Staphylococcus aureus Isolated From Different Raw Milk Samples in China

Staphylococcus aureus (S. aureus) is one of the main pathogens in different raw milk and dairy products, which may lead to economic losses. Staphylococcus aureus is a significant and costly public health concern because it may enter the human food chain and contaminate milk causing foodborne illness. This study aimed to investigate the prevalence, antimicrobial susceptibility and virulence genes of S. aureus in raw milks. In total, 125 raw milk samples collected from goat (n = 50), buffalo (n = 25), camel (n = 25), and yak (n = 25) were collected from 5 provinces in China in 2016. Out of 125 samples, 36 (28.8%) S. aureus were isolated (16 from goat, 9 from buffalo, 6 from camel, and 5 from yak). Out of 36 S. aureus, 26 strains (26/36, 72.2%) showed antibiotics resistance, and 6 strains isolated from goats were identified as methicillin-resistant S. aureus (MRSA). The antimicrobial resistance against Penicillin G, tetracycline and gentamicin was 50% (18/36), 41.7% (15/36), and 36.1% (13/36), respectively. 19 S. aureus (52.8%) were considered as multidrug resistant. The highest prevalence of resistant S. aureus was observed in goat milk (13/36, 36.1%). Among the 36 strains, 16 isolates harbored three or more resistant genes. The resistance genes were detected in 25 S. aureus, including 13 strains in goat, 5 strains in buffalo, 4 strains in camel, and 3 strains in yak. Among the 26 resistant strains, 61.5% of isolates harbored three or more resistant genes. The resistance genes were detected in 25 S. aureus, including 13 strains in goat milk, 5 strains in buffalo milk, 4 strains in camel milk, and 3 strains in yak milk. The most predominant resistance genes were blaZ (18/26, 69.2%), aac6′-aph2″ (13/26, 50.0%), and tet(M) (10/26, 38.5%). The mecA, ant(6)-Ia and fexA gene were only detected in S. aureus from goat milk. The most predominant toxin gene were sec (8/26, 30.8%). The majority of S. aureus were multidrug resistant and carried multiple virulence genes, which may pose potential risk to public health. Our findings indicated that the prevalence and antimicrobial resistance of S. aureus was a serious concern in different raw milks in China, especially goat milks.

Isolation and Identification of Staphylococcus aureus from Milk and Milk Products, Associated Factors for Contamination, and Their Antibiogram in Holeta, Central Ethiopia

Staphylococcus aureus is a pathogenic bacterium-contaminating milk and milk products causing food poisoning primarily due to its enterotoxins. The study aimed at estimating the prevalence of S. aureus in milk and milk products, assessing potential risk factors for contamination, and determining the load and the antimicrobial susceptibility profile of the isolates. A cross-sectional study design was employed to collect a total of 486 samples, comprising 383 raw milk, 47 bulk tank milk, 29 curd milk (Ergo), and 28 Ethiopian cottage cheese (Ayib) samples. Enumeration, isolation, and identification of S. aureus were carried out following standard microbiological techniques. Antibiogram was performed using 12 antimicrobials following the Kirby–Bauer disc diffusion method. Logistic regression analyses were used to assess the association between the occurrence of S. aureus in milk and milk products and potential risk factors. The overall prevalence of S. aureus was 10.69% (52/486) [95% confidence interval (CI):8.09–13.79%]. The prevalence of S. aureus in raw milk, curd milk, bulk tanks at the farm, bulk tanks at milk collection facilities, and cottage cheese was 8.64%, 24.14%, 14.73%, 23.08%, and 14.29%, respectively. The rate of isolation of S. aureus was significantly high in curd milk than in other types of samples (P = 0.010). The study revealed that teat washing (OR: 4.93, 95% CI: 2.06–11.81), use of towel (OR: 12.13, 95% CI: 3.74–39.29), and tick infestations (OR: 4.31, 95% CI: 1.28–14.44) were risk factors associated with the occurrence of S. aureus in milk. About 48.39% of the milk samples assessed had the S. aureus count higher than 10⁵ CFU/ml. The highest rate of resistance was observed to ampicillin (95%), amoxicillin (95%), oxacillin (87.5%), and cefotaxime (80%). All isolates are resistant to at least two classes of antimicrobial drugs, while 65.0% of the isolates were found to be multidrug-resistant. The moderate prevalence, high load, and antimicrobial resistance of S. aureus indicate the higher public health risk due to the widespread consumption of raw milk in the area. Good hygienic practices, regular surveillance of antimicrobial resistance, and prudent use of drugs are suggested.

The Production of Streptomyces W-5B Extract for Antibiofilm against Methicillin-resistant Staphylococcus aureus

The ability of Methicillin-resistant Staphylococcus aureus (MRSA) to form biofilms is one of the triggering factors for the emergence of MRSA resistance to antibiotics. Streptomyces W-5B has shown potency as an antibacterial producer against MRSA. However, the production of microbial bioactive compounds is strongly affected by the source of nutrients in the fermentation medium. Therefore, the objective of this study was to determine the optimal sources of carbon and nitrogen for the production of bioactive compounds with antibiofilm activities. The research method included cultivating Streptomyces W-5B, extract production, and variation of carbon (glucose, sucrose, starch) and nitrogen (casein, peptone, urea) sources for fermentation medium. Antibiofilm activities were measured based on inhibition of biofilm formation and biofilm degradation tests using the microtiter plate method with a crystal violet stain. The results showed that the highest inhibition of biofilm formation was 68.206 ± 1.750% after 12 days of incubation in a fermentation medium containing sucrose and urea. Meanwhile, the highest biofilm degradation was 73.023 ± 1.972% after nine days of incubation on a fermentation medium containing starch and urea. These findings indicated that Streptomyces W-5B has the potency to produce antibiofilm extract against MRSA.

Genetic Characterization of Staphylococcus aureus From Subclinical Mastitis Cases in Dairy Cows in Rwanda

Whole-genome sequencing was carried out on 30 Staphylococcus (S.) aureus isolates from dairy cows with subclinical mastitis from all five provinces of Rwanda. Twenty-five of the isolates produced enough sequence to be analyzed using core genome multilocus sequence typing (cg-MLST). The isolates group into three main clusters. The largest cluster contain isolates of sequence type (ST) 152 (n = 6) and the closely related ST1633 (n = 2). These sequence types have previously mainly been encountered in humans. The isolates of the second-largest cluster belong to ST5477 (n = 5),so far exclusively isolated from cows in Rwanda. The third cluster consists of isolates of ST97 (n = 4), which is a well-known bovine-adapted sequence type. These three clusters were all widespread over the country. Isolates of the usually human-adapted sequence types 1 (n = 2) and 5 (n= 1) were found and a single isolate of ST2430, previously found among humans in Africa. Finally, four isolates of novel sequence types were found: ST7108 (n = 2), ST7109 (n = 1), and ST7110 (n = 1). The blaZ penicillin resistance gene was found in 84% of the isolates and was in all cases corroborated by phenotypic resistance determination. Five (20%) of the isolates carried a tetracycline resistance gene, tet(K) or tetM, and three of these five also displayed phenotypic resistance while two isolates carried a tetM-gene but were yet tetracycline susceptible. Seven (28%) isolates carried the dfrG gene conferring resistance to trimethoprim. Four of these isolates indeed were resistant to trimethoprim while three isolates were sensitive. The str gene conferring resistance to aminoglycosides was found in three isolates; however, none of these displayed resistance to gentamycin. Our data revealed a high diversity of the sequence types of S. aureus isolates from cows with subclinical mastitis in Rwanda. Two major clusters of ST97 and ST5477 are likely to be bovine adapted and cause mastitis while the third cluster of ST152 usually have been found in humans and may signify a recent transmission of these types from human to cows, for example from hand milking. The high prevalence of this sequence type among dairy cows may pose zoonotic threat. The sequence types were widely distributed without any geographic correlation. Penicillin resistance, the most common type of resistance with a prevalence over 80%, but also tetracycline and trimethoprim resistance were displayed by several isolates.

Prevalence and Genetic Diversity of Coagulase Negative Staphylococcus in Food Products Collected from Riyadh Region

The goal of this study was to isolate, count, and identify coagulase-negative Staphylococci from meat and dairy products collected in Riyadh, Saudi Arabia, as well as to perform molecular identification of the mecA gene. In addition, the prevalence of these bacteria among the examined food products was determined. Ninety samples of both meat and dairy products were collected and examined between February 2018 and August 2019. Mannitol salt agar and VITEK 2 system were carried out and VITEK 2 system was used to identify all bacterial isolates. Also, the molecular technique was used to detect the target gene of mecA among CoNS. The proportion of samples in which Staphylococcus species isolated is 13.33% (Camel meat), 6.66% (Beef mortadella), 6.66% (Turkish labneh), 33.33% (Cows cheese), 6.66% (Goat labneh), 13.33% (Nabulsy cheese), 13.33% (Haloumi goat cheese) and 6.66% (Akawy white cheese). Counts of coagulase-negative Staphylococcus species (as cfu/gm) of sample were around 11×104, 10×104, 9×104, 12×104, 4×105, 11×104 (Nabulsy cheese), 14×104 and 12×104, respectively. The Prevalence of species in both products was 3.30% (Staphylococcus vitulinus), 53.30% (Staphylococcus saprophyticus), 16.66% (Staphylococcus hominis), 6.66%, (Staphylococcus equorum and Staphylococcus lentus) and 13.33% (Staphylococcus sciuri). Furthermore, results showed methicillin specific mecA gene was harbored in 40 % of the CoNS.

Investigation of clonal diversity, virulence genes, and antibiotic resistance of Staphylococcus aureus recovered from raw cow milk in southern Xinjiang, China

Staphylococcus aureus is an important pathogen of humans and animals. The aim of this study was to characterize 71 of S. aureus isolates from raw cow milk in southern Xinjiang of China, including molecular typing, distribution of virulence genes, and antimicrobial susceptibility. The isolates belonged to 18 sequence types (STs) (including 11 novel STs) and 6 spa types which were divided into five different clonal complexes (CCs), including CC188, CC352, CC22, CC398, and CC5406. The majority of the strains was grouped into multilocus sequence typing (MLST) CC188 (n = 41), t189 (n = 40), and ST5796 (n = 17). Only 30.9, 12.7, 11.3, and 9.9% of the isolates were resistant to erythromycin, clindamycin/norfloxacin, tetracycline, and gentamicin, respectively. Nine of multidrug resistant (MDR) isolates were observed which was associated with CC398-t2876. The adhesion molecules clfa, clfb, and hlb were most frequently detected with the percentage rate of 98.6% (70/71), 98.6% (70/71), and 90.1% (64/71), respectively. The percentage rates of the staphylococcal enterotoxin genes sea, seb, sec, sed, seg, and sei in S. aureus isolates were 5.6, 19.8, 40.8, 1.4, 49.3, and 30.9%, respectively. The see, seh, and sej genes were not found. This study provides data about the occurrence of S. aureus in raw cow milk, revealing high carriage frequency, drug resistance, and population structure of S. aureus. Furthermore, this study suggests that effective hygienic measures be taken when handling dairy cows, in order to prevent spreading MDR strains to human through direct contact and/or consumption of contaminated food.

Molecular Characterization of Staphylococcus aureus Isolated from Human and Food Samples in Northern Algeria

Staphylococcus aureus is a commensal resident of the skin and nasal cavities of humans and can cause various infections. Some toxigenic strains can contaminate food matrices and cause foodborne intoxications. The present study aimed to provide relevant information (clonal complex lineages, agr types, virulence and antimicrobial resistance-associated genes) based on DNA microarray analyses as well as the origins and dissemination of several circulating clones of 60 Staphylococcus aureus isolated from food matrices (n = 24), clinical samples (n = 20), and nasal carriers (n = 16) in northern Algeria. Staphylococcus aureus were genotyped into 14 different clonal complexes. Out of 60 S. aureus, 13 and 10 isolates belonged to CC1-MSSA and CC97-MSSA, respectively. The CC 80-MRSA-IV was the predominant S. aureus strain in clinical isolates. The accessory gene regulator allele agr group III was mainly found among clinical isolates (70.4%). Panton–Valentine leukocidin genes lukF/lukS-PV were detected in 13.3% of isolates that all belonged to CC80-MRSA. The lukF/S-hlg, hlgA, and hla genes encoding for hemolysins and leucocidin components were detected in all Staphylococcusaureus isolates. Clinical and food isolates harbored more often the antibiotic resistance genes markers. Seventeen (28.3%) methicillin-resistant Staphylococcus aureus carrying the mecA gene localized on a SCCmec type IV element were identified. The penicillinase operon (blaZ/I/R) was found in 71.7% (43/60) of isolates. Food isolates belonging to CC97-MSSA carried several antibiotic resistance genes (blaZ, ermB, aphA3, sat, tetM, and tetK). The results of this study showed that all clones were found in their typical host, but interestingly, some nasal carriers had isolates assigned to CC705 thought to be absent in humans. The detection of MRSA strains among food isolates should be considered as a potential public health risk. Therefore, controlling the antibiotics prescription for a rational use in human and animal infections is mandatory.

Antimicrobial resistance studies in staphylococci and streptococci isolated from cows with mastitis in Argentina

BACKGROUND

Staphylococcus aureus and Streptococcus agalactiae are the main cause of clinical mastitis in dairy cattle in Argentina, whereas coagulase-negative staphylococci (CNS) and environmental streptococci are the main cause of subclinical mastitis. Bacteria isolated from infected animals show increasing antimicrobial resistance.

OBJECTIVES

This study aims to determine the antimicrobial resistance of staphylococci and streptococci isolated from milk with mastitis, and to genotypically characterize the methicillin-resistant (MR) staphylococci.

METHODS

Isolation was performed on blood agar and identification was based on biochemical reactions. Antimicrobial susceptibility was according to the Clinical and Laboratory Standards Institute guidelines. The antimicrobial resistance genes, SCCmec type and spa type were detected by the polymerase chain reaction method.

RESULTS

We isolated a total of 185 staphylococci and 28 streptococci from 148 milk samples. Among the staphylococcal isolates, 154 were identified as CNS and 31 as S. aureus. Among the 154 CNS, 24.6% (n = 38) were resistant to penicillin, 14.9% (n = 23) to erythromycin, 17.5% (n = 27) to clindamycin, 6.5% (n = 10) to cefoxitin and oxacillin. Among the S. aureus isolates, 16.1% (n = 5) were resistant to penicillin, 3.2% (n = 1) to cefoxitin and oxacillin (MRSA). Six MR isolates (5 CNS and 1 MRSA) were positive to the mecA gene, and presented the SCCmec IVa. The MRSA strain presented the sequence type 83 and the spa type 002. Among the 28 streptococcal isolates, 14.3% (n = 4) were resistant to penicillin, 10.7% (n = 3) to erythromycin and 14.3% (n = 4) to clindamycin.

CONCLUSIONS

The present findings of this study indicate a development of antimicrobial resistance in main bacteria isolated from cows with mastitis in Argentina.

Potentiating effects of leaderless enterocin DD14 in combination with methicillin on clinical methicillin-resistant Staphylococcus aureus S1 strain

Biofilm formation by pathogenic bacteria as well as their resilience to antibiotic treatments are a major health problem. Here, we sequenced and analyzed the genome of the clinical methicillin-resistant Staphylococcus aureus S1 (MRSA-S1) strain and established its sensitivity to the combination of methicillin and the leaderless two peptides enterocin DD14 (EntDD14). Such sensitivity was assessed in vitro based on the MIC/FIC values as well as on killing curves experiments. Moreover, combination of EntDD14 and methicillin was able to reduce the biofilm formation of Staphylococcus aureus S1 of about ∼30 %. Interestingly, genes thought to be involved in the virulence of MRSA-S1, like nuc and pvl which code, respectively, for nuclease and Panton-Valentine leucocidin, were shown to be downregulated following treatment with EntDD14 and methicillin. Similar effects were registered for other genes such as cflA, cflB and icaB, coding for bacterial ligands clumping factors A, B and intercellular adhesion factor respectively. All these data, suggest that combinations of bacteriocins and antibiotics are useful as a backup for treatment of bacterial infections.

Target-based screening for natural products against Staphylococcus aureus biofilms

As a notorious food-borne pathogen, Staphylococcus aureus can readily cause diseases in humans via contaminated food. Biofilm formation on various surfaces can increase the capacity of viable S. aureus cells for self-protection due to the stubborn structure of the biofilm matrix. Increased disease risk and economic losses caused by biofilm contamination in the food industry necessitate the urgent development of effective strategies for the inhibition and removal of S. aureus biofilms. Natural products have been extensively used as important sources of "eco-friendly" antibiofilm agents to avoid the side effects of conventional strategies on human health and the environment. This review discusses biofilm formation of S. aureus in food industries and focuses on providing an overview of potential promising target-oriented natural products and their mechanisms of S. aureus biofilm inhibition or removal. Hoping to provide valuable information of attractive research targets or potential undeveloped targets to screen potent natural anti-biofilm agents in food industries.

Antibiotic resistance of Staphylococcus aureus isolated from raw cow and goat milk produced in the Tiaret and Souk Ahras areas of Algeria

Background and Aim:

Staphylococcus aureus is a leading cause of infection in both humans and animals. Most livestock strains have shown antibiotic resistance to the many molecules used in veterinary therapeutics. This study aimed to assess the resistance patterns of these bacteria, we carried out our study in the Tiaret and Souk Ahras areas of Algeria.

Materials and Methods:

We collected 116 samples of bovine and goat milk to detect S. aureus. We used a selective media to isolate the strains, followed by biochemically identifying the isolates. We determined the susceptibility of the strains to antibiotic molecules using the disk diffusion method and confirmed the methicillin-resistant S. aureus (MRSA) with oxacillin minimum inhibitory concentration (MIC).

Results:

Our results showed that 26.72% of the samples were contaminated with S. aureus, and we recovered 31 isolates from the positive samples. We ascribed a high resistance profile to penicillin G (96.77%), fusidic acid (67.74%), and tobramycin (45.16%) and isolated 4MRSA strains.

Conclusion:

The presence of S. aureus, including MRSA strains in raw milk, can present a public health hazard, because these strains can cause widespread food poisoning. This finding will be useful to the veterinarians to choose an adequate treatment and to sensitize livestock breeders and milk producers to ensure the health of consumers.

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.

Multilocus sequence analysis reveals genetic diversity in Staphylococcus aureus isolate of goat with mastitis persistent after treatment with enrofloxacin

Staphylococcus aureus is one of the main bacterial agents responsible for cases of mastitis in ruminants, playing an important role in the persistence and chronicity of diseases treated with antimicrobials. Using the multilocus sequence typing technique, network approaches and study of the population diversity of microorganisms, we performed analyzes of S. aureus (ES-GPM) isolated from goats with persistent mastitis (GPM). The most strains of ES-GPM were categorically different phylogenetically from the others and could be divided into two lineages: one with a majority belonging to ES-GPM and the other to varied strains. These two lineages were separated by 27 nuclear polymorphisms. The 43 strains comprised 22 clonal complexes (CCs), of which the ES-GPM strains were present in CC133, CC5 and a new complex formed by the sequence type 4966. The genetic diversity of some alleles showed be greater diversity and polymorphism than others, such as of the aroE and yqiL genes less than glpF gene. In addition, the sequences ES-GPM to the arc gene and glpF alleles showed the greatest number of mutations for ES-GPM in relation to non-ES-GPM. Therefore, this study identified genetic polymorphisms characteristic of S. aureus isolated from milk of goats diagnosed with persistent mastitis after the failed treatment with the antibiotic enrofloxacin. This study may help in the future to identify and discriminate this agent in cases of mastitis, and with that, the most appropriate antibiotic treatment can be performed in advance of the appearance of persistent mastitis caused by the agent, reducing the chances of premature culling and animal suffering.

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.

Multi Locus Sequence Typing and spa Typing of Staphylococcus Aureus Isolated from the Milk of Cows with Subclinical Mastitis in Croatia

Background: The bacterial species S. aureus is the most common causative agent of mastitis in cows in most countries with a dairy industry. The prevalence of infection caused by S. aureus ranges from 2% to more than 50%, and it causes 10–12% of all cases of clinical mastitis. Aim: The objective was to analyze 237 strains of S. aureus isolated from the milk of cows with subclinical mastitis regarding the spa, mecA, mecC and pvl genes and to perform spa and multi-locus sequence typing (MLST). Methods: Sequencing amplified gene sequences was conducted at Macrogen Europe. Ridom StaphType and BioNumerics software was used to analyze obtained sequences of spa and seven housekeeping genes. Results: The spa fragment was present in 204 (86.1%) of strains, while mecA and mecC gene were detected in 10 strains, and the pvl gene was not detected. Spa typing successfully analyzed 153 tested isolates (64.3%), confirming 53 spa types, four of which were new types. The most frequent spa type was t2678 (14%). MLST typed 198 (83.5%) tested strains and defined 32 different allele profiles, of which three were new. The most frequent allele profile was ST133 (20.7%). Six groups (G) and 15 singletons were defined. Conclusion: Taking the number of confirmed spa types and sequence types (STs) into account, it can be concluded that the strains of S. aureus isolated from the milk of cows with subclinical mastitis form a heterogenous group. To check the possible zoonotic potential of isolates it would be necessary to test the persons and other livestock on the farms.

Antimicrobial resistance of Staphylococcus spp. isolated from organic and conventional Minas Frescal cheese producers in São Paulo, Brazil

The genus Staphylococcus is recognized worldwide as a cause of bacterial infections in humans and animals. Antibiotics used in dairy cattle combined with ineffective control can increase antimicrobial resistance. The objective of this study was to characterize 95 Staphylococcus strains isolated from organic and conventional Minas Frescal cheese production regarding antibiotic resistance (phenotype and genotype), presence of sanitizer-resistant genes and biofilm-formation genes, and SCCmec typing. Most strains (25.3%) showed higher resistance to penicillin, followed by oxacillin (21.1%) and clindamycin (11.6%). Among antibiotic resistance genes, the most prevalent were blaZ (25.3%), mecA (13.7%), lsaB (6.3%), msrA (4.2%), ant4 (3.2%), and tetM (2.1%); among sanitizer-resistance genes they were qacA/B (5.3%) and qacC (6.3%); and among biofilm, bap (4.2%), icaA (29.5%), icaD (41.1%). However, there was no statistically significant difference between organic and conventional dairy products, possibly due to the lack of synthetic antibiotic use on conventional farms during the sample collection period. Methicillin-resistant Staphylococcus aureus (MRSA) had their SCCmec identified as types I and IVc, and the methicillin-resistant coagulase-negative staphylococci had nontypeable SCCmec. These results suggest that there are antibiotic-resistant strains in both organic and conventional Minas Frescal cheese production in the state of São Paulo, Brazil. This supports the idea that improved quality control is needed from the milking stage up to the final product.

Prevalence and Characterization of Coagulase Positive Staphylococci from Food Products and Human Specimens in Egypt

Methicillin-resistant Staphylococcus aureus (MRSA) strains have veterinary and public health importance as they are responsible for a wide range of difficult to treat infections and food poisoning. Two hundred samples (50 samples each of minced meat, beef luncheon, Karish cheese, and human samples (pus swab from open wounds)) were cultured, and MRSA strains were identified using disk diffusion tests and mecA gene-based PCR. A total of 35% (70/200) of the examined samples were confirmed as coagulase-positive S. aureus in minced meat (46%), beef luncheon (44%), Karish cheese (44%), and human samples (22%). The MRSA strains showed resistance to amoxicillin (91.4%), penicillin (97.1%), cefoxitin (85.7%), cephradine (82.9%), tetracycline (57.2%), and erythromycin (52.8%). More than half of the tested S. aureus isolates harbored the mecA gene. The sequence analysis of the mecA gene from the minced meat, Karish cheese, and human samples revealed high genetic similarities between the S. aureus isolates from these sources. In conclusion, our findings indicate a risk for the transmission of the mecA gene of S. aureus across the food chain between humans and animal food products. Further studies should focus on finding additional epidemiological aspects of the MRSA strains in food chain.

Dysregulated Host Responses Underlie 2009 Pandemic Influenza-Methicillin Resistant Staphylococcus aureus Coinfection Pathogenesis at the Alveolar-Capillary Barrier

Influenza viruses are a continual public health concern resulting in 3-5 million severe infections annually despite intense vaccination campaigns and messaging. Secondary bacterial infections, including Staphylococcus aureus, result in increased morbidity and mortality during seasonal epidemics and pandemics. While coinfections can result in deleterious pathologic consequences, including alveolar-capillary barrier disruption, the underlying mechanisms are poorly understood. We have characterized host- and pathogen-centric mechanisms contributing to influenza-bacterial coinfections in a primary cell coculture model of the alveolar-capillary barrier. Using 2009 pandemic influenza (pH1N1) and methicillin-resistant S. aureus (MRSA), we demonstrate that coinfection resulted in dysregulated barrier function. Preinfection with pH1N1 resulted in modulation of adhesion- and invasion-associated MRSA virulence factors during lag phase bacterial replication. Host response modulation in coinfected alveolar epithelial cells were primarily related to TLR- and inflammatory response-mediated cell signaling events. While less extensive in cocultured endothelial cells, coinfection resulted in changes to cellular stress response- and TLR-related signaling events. Analysis of cytokine expression suggested that cytokine secretion might play an important role in coinfection pathogenesis. Taken together, we demonstrate that coinfection pathogenesis is related to complex host- and pathogen-mediated events impacting both epithelial and endothelial cell regulation at the alveolar-capillary barrier.

Methicillin-Resistant Staphylococcus aureus (MRSA) in Slaughter Houses and Meat Shops in Capital Territory of Pakistan During 2018–2019

Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) is a major concern in many parts of the world, including Pakistan. The aim of this study was to investigate the prevalence of MRSA in slaughterhouses and meat shops in Rawalpindi-Islamabad, Pakistan, 2018–2019. A total of 300 samples were collected: 40 from each of working area, tools (knives, hooks), butcher hands and beef, 30 from each of chicken and mutton, 20 from each of nasal and rectal swabs. S. aureus was phenotypically identified by performing gram staining and biochemical tests. 150 of the 300 samples were confirmed to be S. aureus by phenotypic identification. MRSA was identified among S. aureus positive isolates by performing disk diffusion test and by detecting S. aureus-specific genes such as 16s rRNA, nuc, mecA, spa, and coa. Out of 150 isolates 96 (63%) showed resistance to antibiotic cefoxitin, known as a potential marker for detecting MRSA. While all 150 isolates have shown complete resistance to the four antibiotics neomycin, methicillin, ciprofloxacin and tetracycline. The nuc and 16s rRNA genes were detected in all 150 S. aureus-positive isolates and 118 (79%) were confirmed to be MRSA through the detection of the mecA gene. MRSA prevalence was highest in chicken (23/30, 77%) followed by beef (25/40, 63%), mutton (15/30, 50%), knives (18/40, 45%), nasal swabs (7/20, 35%), working area (11/40, 28%), rectal swabs (5/20, 25%), hooks (7/40, 18%), and butcher hands (7/40, 18%). 50 MRSA-positive isolates were chosen to identify two virulence factors (spa and coa gene). Of the 50 MRSA isolates subject to coa and spa gene typing, 27 (54%) were positive for the coa gene and 18 (36%) were positive for the spa gene, respectively. To the best of our knowledge, this was the first study on the molecular identification of MRSA in meat samples from Pakistan. High prevalence of MRSA in meat samples demand for implementation of proper hygienic practices and procedures during the slaughtering, transport and marketing of meat and meat products in order to prevent the spread of these bacteria to the human population.

Isolation and Characterization of Staphylococcus aureus From Food of Bovine Origin in Mekelle, Tigray, Ethiopia

Background:

Among Food-borne diseases, S. aureus is a leading cause of gastroenteritis resulting from the consumption of contaminated food.

Objectives:

The study aimed to isolate and characterize S. aureus from raw milk, yogurt and meat and determine its antibiotic sensitivity pattern.

Materials and Methods:

A cross-sectional study was conducted from December 2014 to June 2015 in Mekelle. A total of 284 samples were collected purposively. Enumeration of total viable bacteria count (TVBC), bacteriological isolation and identification, antimicrobial susceptibility testing, as well as PCR amplification of fem A and mec A genes were performed. Chi-square (χ2) and one way ANOVA tests were used for analysis.

Results:

Overall TVBC mean was found to be 1.29x108cfu/ml/g. The highest TVBC (1.38x108cfu/ml) was from the yogurt sample and the lowest (1.26x108cfu/g) was from meat. The overall prevalence of coagulase positive S. aureus (CoPS) was 39.1% (111) and of the smaples, 51(56.04%), 38(26.20%) and 22(45.83%) were isolated from meat, raw milk, and yogurt, respectively. There was a statistically significant difference (p<0.05) among the different sample types and sources in the prevalence of S. aureus. Almost half of the CoPS isolates were sensitive to Tetracycline, Gentamycin, and Kanamycin, but resistant to Amoxicillin (96.9%) and Penicillin G (93.8%). Moreover, 93.75% of the isolates developed multidrug resistance. All isolates carried the fem A gene and among these isolates, 12 (37.5%) carried mec A gene.

Conclusion:

The present study revealed that foods of bovine origin of the study area are found to be having less bacteriological quality, high prevalence of CoPS and development of drug resistance.