Presence of methicillin-resistant Staphylococcus aureus in the food chain

Prevalence, antimicrobial resistance, and genetic characteristics of Staphylococcus aureus isolates in frozen flour and rice products in Shanghai, China

Staphylococcus aureus is widely recognized as a highly hazardous pathogen that poses significant threats to food safety and public health. This study aimed to assess the prevalence, antimicrobial resistance, and genetic characteristics of S. aureus isolates recovered from 288 frozen flour and rice product samples in Shanghai, China, between September 2019 and May 2020. A total of 81 S. aureus isolates were obtained, representing 25 sequence types (STs), with ST7 being the most prevalent (17.28%, n = 14). The majority of S. aureus isolates (85.19%, n = 69) carried at least one enterotoxin gene, with the seg gene being the most frequently detected (51.85%, n = 42). Additionally, 12 isolates (14.81%) were identified as methicillin-resistant S. aureus (MRSA) through mecA gene detection. Notably, this study reported the presence of an ST398 MRSA isolate in frozen flour and rice products for the first time. All MRSA isolates displayed multidrug resistance, with the highest resistance observed against cefoxitin (100.00%), followed by penicillin (91.67%) and erythromycin (66.67%). Genomic analysis of the 12 MRSA isolates revealed the presence of twenty distinct acquired antimicrobial resistance genes (ARGs), eight chromosomal point mutations, and twenty-four unique virulence genes. Comparative genome analysis indicated close genetic relationships between these MRSA isolates and previously reported MRSA isolates from clinical infections, highlighting the potential transmission of MRSA through the food chain and its implications for public health. Significantly, the identification of three plasmids harboring ARGs, insertion sequences (ISs), the origin of transfer site (oriT), and the relaxase gene suggested the potential for horizontal transfer of ARGs via conjugative plasmids in S. aureus. In conclusion, this study revealed significant contamination of retail frozen flour and rice products with S. aureus, and provided essential data for ensuring food safety and protecting public health.

Antimicrobial Resistant Pathogens Detected in Raw Pork and Poultry Meat in Retailing Outlets in Kenya

There is increasing proof of bacterial resistance to antibiotics all over the world, and this puts the effectiveness of antimicrobials that have been essential in decreasing disease mortality and morbidity at stake. The WHO has labeled some classes of antimicrobials as vitally important to human health. Bacteria from animals are thought to be reservoirs of resistance genes that can be transferred to humans through the food chain. This study aimed to identify the resistance patterns of bacteria from pork and poultry meat samples purchased from leading retail outlets in Kenya. Of the 393 samples collected, 98.4% of pork and 96.6% of poultry were contaminated with high levels of bacteria. Among the 611 bacterial isolates recovered, 38.5% were multi-drug resistant. This resistance was noted for critically essential antimicrobials (according to the WHO) such as rifampicin (96%), ampicillin (35%), cefotaxime (9%), cefepime (6%), and ciprofloxacin (6%). Moreover, there was high resistance to key antimicrobials for veterinary medicine such as tetracycline (39%), sulfamethoxazole (33%), and trimethoprim (30%). It is essential to spread awareness about the judicious use of antibiotics and take preventive measures to reduce disease burden.

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.

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

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

Garlic essential oil in water nanoemulsion prepared by high-power ultrasound: Properties, stability and its antibacterial mechanism against MRSA isolated from pork

Food-borne methicillin-resistance Staphylococcus aureus (MRSA) has caused significant health threats and economic loss in livestock and poultry products. Garlic essential oil (GEO) is an effective antibacterial agent but presents strong instability and hydrophobicity. In this study, GEO in water nanoemulsion (GEON) with good stability was produced by emulsification technique of high-power ultrasound. Its antibacterial activity and underlying mechanism against MRSA isolated from retailed pork were investigated. Results showed that ultrasonic treatment significantly reduced the particle size of GENO from 820.3 to 215.0 nm as time increased from 0 to 10 min. Comparatively, GEON of 10 min ultrasound was more stable than other GEONs (0, 1, 5 min) during 30 d storage. It also displayed good thermal stability and relatively good ion stability (NaCl, MgCl₂, and glucose). Antibacterial analysis showed that GEON (10 min) exhibited the best anti-MRSA activity among all GEONs, and the minimum inhibitory concentration of GEO in this nanoemulsion was 0.125 % (1.25 mg/mL). Treatment of GEON (10 min) significantly suppressed the cell proliferation of MRSA, which was mainly achieved by damaging the cell membrane as evidenced by membrane depolarization and considerable leakage of intracellular nucleic acids and protein. Laser scanning confocal microscope and scanning electron microscopy showed that treatment of GEON (10 min) significantly altered the membrane integrity and severely damaged the cellular membrane and structure. The present work illustrated that GEON produced by ultrasonic emulsification is a promising alternative to inhibit the contamination and spread of MRSA in livestock and poultry products.

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.

Prevalence, antibiotic resistance, and enterotoxin production of Staphylococcus aureus isolated from retail raw beef, sheep, and lamb meat in Turkey

The main objective of this study was to isolate and identify Staphylococcus aureus from retail raw red meat samples and evaluate their enterotoxin gene and antibiotic resistance profiles. A total of 452 retail raw meat samples, including beef (n = 200), sheep (n = 125), and lamb (n = 127) randomly purchased from various supermarkets and butchers in Ankara between July 2019 and November 2020, were tested for the prevalence of S. aureus. The S. aureus strain was identified using morphological and molecular (16S rRNA and nuc gene) methods. Moreover, nine Staphylococcal enterotoxin (SE) genes were screened using polymerase chain reaction. Antibiotic resistance of S. aureus was determined using the phenotypic disc diffusion method. The overall prevalence of S. aureus among screened samples was 21.23%. Additionally, 65.62% of S. aureus strains contained SE gene regions. The predominant SEs in the S. aureus strains were sea (50.79%), followed by sed (25.39%) and seb (23.80%). However, sec, see, seg, seh, sei, and sej genes were never detected. A substantial proportion (40-100%) of the isolates were found resistant to kanamycin, telithromycin, penicillin G, streptomycin, erythromycin, cloxacillin, ampicillin, pristinamycin, nalidixic acid, azithromycin, and ciprofloxacin. Multi-drug resistance (MDR) was observed in 96.87% of the S. aureus strains. These results show a low prevalence of S. aureus in raw red meat samples in Turkey. However, a high rate of SEA raises serious health concerns. Due to the high levels of MDR observed in this study, there is a need to strictly control antibiotic use in animals in Turkey.

Cefotax-magnetic nanoparticles as an alternative approach to control Methicillin-Resistant Staphylococcus aureus (MRSA) from different sources

This study aimed to evaluate the efficacy of magnetic nanocomposite of cefotax against MRSA. A total of 190 samples were collected from milk, farm personnel and different environmental components from the dairy farm under the study to isolate S. aureus. Cefotax based magnetic nanoparticles was synthetized by the adsorption method and marked using Fourier-transform infrared spectrum (FT-IR), and X-ray diffraction (XRD), then it was characterized using Scanning and Transmission Electron Microscope (SEM and TEM). The obtained results revealed that number of positive samples of S. aureus isolation were 63 (33.1%), mainly from feed manger followed by milk machine swabs (60.0 and 53.3%, respectively) at X2 = 48.83 and P < 0.001. Obtained isolates were identified biochemically and by using molecular assays (PCR), also mec A gene responsible for resistance to cefotax was detected. Testing the sensitivity of 63 isolates of S. aureus showed variable degree of resistance to different tested antibiotics and significant sensitivity to cefotax based magnetic nanoparticles at P < 0.05. It was concluded that dairy environment might act a potential source for transmission of MRSA between human and animal populations. In addition, cefotax based magnetic nanoparticles verified an extreme antimicrobial efficacy against MRSA.

Prevalence, Antimicrobial Resistance, and Molecular Characteristics of Staphylococcus aureus and Methicillin-Resistant Staphylococcus aureus from Retail Ice Cream in Shaanxi Province, China

Staphylococcus aureus (S. aureus) is one of the major opportunistic foodborne pathogens as well as a source of human and animal infections. As surveillance of S. aureus and methicillin-resistant Staphylococcus aureus (MRSA) is limited in ice cream, a total of 240 ice cream samples were collected from three cities in Shaanxi province, China, and screened for S. aureus. All isolates were characterized by antimicrobial susceptibility testing, staphylococcal protein A typing, multilocus sequence typing, enterobacterial repetitive intergenic consensus typing, virulence, and resistance genes. S. aureus was recovered from 10 (4.2%) ice cream samples (13 isolates) with average count from 10 to 100 colony-forming units per gram in all cases. Resistance to amoxicillin/clavulanic acid, penicillin, and trimethoprim/sulfamethoxazole (each 100.0%) was most frequently observed, followed by ampicillin (76.9%), erythromycin (46.2%), ceftriaxone (30.8%), and cefoxitin (15.4%). A total of five types of antimicrobial resistance genes were detected, including β-lactam (blaZ and mecA), macrolide (ermB and ermC), tetracycline (tetK), aminoglycoside [aac(6')/aph(2') and aph(3')-III], and trimethoprim (dfrG). All of the strains harbored at least one staphylococcal enterotoxins gene. The commonly detected virulence genes were selw and hld (100.0%), followed by selx (92.3%); hla (84.6%); pvl (76.9%); seg, sem, and sen (each 38.5%); sei, seo, and hlb (each 30.8%); sea, seb, selu, and sely (each 23.1%); sed, sej, sek, sep, and seq (each 15.4%); and ser (7.7%). ST5-t002, ST7-t091, and ST5225-t4911 (each 15.4%) were the predominant clones, followed by ST5-t045/t105, ST6-t701/t15417, ST25-t078, ST188-t189, and ST398-t034 (each 7.7%). Among the 13 strains of S. aureus, 2 isolates were detected as MRSA (15.4%), and the molecular type belonged to ST5225-IVa-t4911. Using a 98.8% similarity cutoff, the 13 isolates were divided into 5 clusters (I-1 to I-5). These results demonstrated that the prevalence of S. aureus and MRSA was low in ice cream. However, these isolates exhibited a high level of potential pathogenicity, which represents a potential health hazard for consumers.

Evaluation of antimicrobial compounds to inhibit growth of select Gram-positive pathogenic or antimicrobial resistant bacteria in air-exposed silage

Spoiled silages can harbor pathogenic and antimicrobial-resistant microbes. The potential of some antimicrobial additives to inhibit certain pathogenic and antimicrobial-resistant bacteria in air-exposed silage was measured using pure and mixed bacterial cultures. With pure cultures, laurate and monolaurin (5 mg·mL−1) caused decreases (P < 0.05) of 4 to >7 log10 colony-forming units (CFU)·mL−1 in Listeria monocytogenes and Enterococcus faecalis compared to controls. Ten-fold higher amounts of these inhibitors were needed to equivalently decrease staphylococci. 2-Nitropropanol (1 mg·mL−1) decreased (P < 0.05) E. faecalis and L. monocytogenes 2.9–3.8 and 2.4–7.2 log10 CFU·mL−1 after 6 and 24 h incubations, respectively. In air-exposed whole-plant corn silage the inhibitors caused decreases, although not necessarily significant, of 0.7–2.2 log10 CFU·mL−1 in L. monocytogenes, staphylococci and culturable aerobes after 24 h incubation, with modest yet significant (P < 0.05) inhibition (<0.1–0.3 log10 CFU·mL−1) of yeasts and molds. Tests for carry-over effects against ruminal microbes revealed laurate, monolaurin, and 2-nitropropanol inhibited methanogenesis by >50% (P < 0.05) after 24 h incubation and inhibited L. monocytogenes and enterococci. The antimicrobial activities exhibited by these compounds may yield opportunities to optimize their use to rescue spoiled silages.

Prevalence, Enterotoxigenic Potential and Antimicrobial Resistance of Staphylococcus aureus and Methicillin-Resistant Staphylococcus aureus (MRSA) Isolated from Algerian Ready to Eat Foods

Staphylococcus aureus causes a foodborne intoxication due to the production of enterotoxins and shows antimicrobial resistance, as in the case of methicillin-resistant strains (MRSA). Herein, we analyzed 207 ready-to-eat foods collected in Algeria, reporting a S. aureus prevalence of 23.2% (48/207) and respective loads of coagulase positive staphylococci (CPS) ranging from 1.00 ± 0.5 to 5.11 ± 0.24 Log CFU/g. The 48 S. aureus isolates were widely characterized by staphylococcal enterotoxin gene (SEg)-typing and 16S-23S rDNA intergenic spacer region (ISR)-PCR, as well as by detecting tst and mecA genes, genetic determinants of toxic shock syndrome toxin-1 and methicillin resistance, respectively. We found that the S. aureus isolates belonged to seven different SEg-types harboring the following combinations of genes: (1) selW, selX; (2) egc (seG, seI, seM, seN, seO), selW, selX; (3) seA, seH, seK, seQ, selW, selX; (4) seB, selW, selX; (5) seD, selJ, seR, selW, selX; (6) seH, selW, selX, selY; and (7) seA, egc, selW, selX, while among these, 2.1% and 4.2% were tst- and mecA- (staphylococcal chromosomal cassette mec-type IV) positive, respectively. Selected strains belonging to the 12 detected ISR-types were resistant towards antimicrobials including benzylpenicillin, ofloxacin, erythromycin, lincomycin, tetracyclin, kanamycin, oxacillin, and cefoxitin; 8.3% (1/12) were confirmed as MRSA and 16.7% (2/12) were multidrug resistant. The present study shows the heterogeneity of the S. aureus population in Algerian ready-to-eat foods as for their toxigenic potential and antimicrobial resistance, shedding the light on the quality and safety related to the consume of ready-to-eat foods in Algeria.

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.

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.

Prevalence and characterization of Staphylococcus aureus and methicillin-resistant Staphylococcus aureus isolated from retail yak butter in Tibet, China

This study aimed to investigate the prevalence, molecular characteristics and antibiotic resistance of Staphylococcus aureus isolates from yak butter in Tibet, China. A total of 218 yak butter samples were collected from retail stores in Tibet and screened for Staph. aureus. Furthermore, the virulence genes, resistance genes, antimicrobial susceptibility, and molecular typing [pulsed-field gel electrophoresis (PFGE), multilocus sequence typing, and staphylococcal protein A (spa) typing] of Staph. aureus isolates were detected. The results showed that 12.4% of yak butter samples were contaminated with Staph. aureus, including 5 samples positive for methicillin-resistant Staph. aureus (MRSA). Among all isolates, 96.3% harbored one or more virulence genes, including classical (sea and sec), novel enterotoxin-encoding genes (seh, sek, sel, and seq), and hemolysin genes (hla and hld). All isolates were resistant to at least 2 different antibiotic classes, and the isolates were most commonly resistant to sulfonamides, β-lactams, and erythromycin. For resistance genes, blaZ (74.1%) was most frequently detected, followed by dfrG (51.9%), erm(B) (22.2%), mecA (18.5%), tet(K) (14.8%), aph(2″)-Ia, aph(3')-III, and ant(6)-Ia (11.1% for each), and erm(C) (7.4%). We detected 8 spa types, 6 sequence types (ST), and 5 clonal complex (CC) types. In addition, 1 isolate of Staph. aureus was nontypeable. We found that CC1-ST1-t559 (55.6%) was the most predominant clone, followed by CC59-ST59-t437 (11.1%), CC5-ST5-t002 (7.4%), CC1-ST1, CC1-ST1-t114, CC1-ST573-t4938, CC1-ST573-t8915, CC30-ST30-t021, and CC25-ST25-t167 (3.7% for each). For PFGE typing, a total of 5 clusters and 15 pulsotypes were generated, and some isolates from different samples showed indistinguishable pulsotypes. Our findings suggest that yak butter produced in Tibet, China, could be contaminated by Staph. aureus strains, including MRSA strains, carrying various virulence and resistance genes, representing multiple antimicrobial resistance phenotypes. The presence of potentially virulent and antibiotic-resistant Staph. aureus strains in yak butter poses a potential threat to consumers, and appropriate measures need to be taken in the production chain to reduce the occurrence of Staph. aureus in yak butter.

Prevalence of pathogens harbouring mobile antimicrobial resistance genes and virulence factors in retail beef and mutton

Food safety is always a global issue, due to the increased dissemination of antimicrobial resistance and food poisoning related to foodborne bacterial pathogens. The purpose of this study was to assess the risk of potential foodborne bacteria of beef and mutton in retail stores. A total of 134 samples were collected from 24 local markets in Beijing, including raw and cooked beef or mutton, as well as samples derived from the corresponding environment and human beings. We obtained 674 isolates, of which Klebsiella spp. and Staphylococcus spp. were the dominant bacterial species in the meat samples and the environmental samples, respectively. Additionally, environmental bacteria are common in samples from different sources. Based on the results of antimicrobial sensitivity testing, resistance to tetracycline (with a resistance rate of 47.40%), amoxicillin + clavulanate (47.13%) and erythromycin (28.03%) were the major resistant phenotypes. According to the whole genome analysis, the extended spectrum beta-lactamase genes harboured by two K. pneumoniae strains isolated from cooked and raw beef were located on mobile elements. The major toxin genes of Bacillus cereus and adhesion- or invasion-related virulence factors were also shared among isolates from different sources. These factors pose potential risks to public health and need attention.

Staphylococcus aureus grown in anaerobic conditions exhibits elevated glutamine biosynthesis and biofilm units

The enormous spread of Staphylococcus aureus infections through biofilms is a major concern in hospital-acquired infections. Biofilm formation by S. aureus on any surface is facilitated by adjusting its redox status. This organism is a facultative anaerobe shift more towards reductive conditions by enhancing nitrogen metabolism where glutamine synthesis plays a key role. Glutamine is synthesized by glutamine synthetase (GS) encoded by the glnA gene. The gene was amplified by PCR from the chromosomal DNA of S. aureus, sequenced (HQ329146.1), and cloned. The pure recombinant GS exhibited K_m of 11.06 ± 0.05 mmol·L^-1 for glutamate and 2.4 ± 0.03 mmol·L^-1 for ATP. The glnA gene sequence showed a high degree of variability with its human counterpart, while it was highly conserved in bacteria. Structural analysis revealed that the GS structure of S. aureus showed close homology with other Gram-positive bacteria and exhibited a high degree of variation with Escherichia coli GS. In the present study, we observed the increased presence of GS activity in multidrug-resistant strains of S. aureus with elevated biofilm units, grown in brain heart infusion broth; among them methicillin-resistant strains S. aureus LMV 3, 4, and 5 showed higher biofilm units. All these results explain the important role of glutamine biosynthesis with elevated biofilm units in the pathogenesis of S. aureus.

Traditional and Artisanal Beverages in Nigeria: Microbial Diversity and Safety Issues

A review of up to 90 articles on the microorganisms associated with important artisanal or traditional beverages in Nigeria was carried out. This resulted in an overview of the prevalent microorganisms associated with soymilk, nono (fermented cow milk), tiger nut milk, yoghurt, kunu, zobo, palm wine and the local beers pito and brukutu. The bacteria genera, namely Bacillus, Escherichia, Lactobacillus, Staphylococcus, and Streptococcus, were detected in all nine beverages. On the contrary, this survey resulted in finding that the genera Saccharomyces, Aspergillus, Candida, and Penicillium were the eukaryotic microorganisms isolated in all beverages. The occurrence of fungal isolates, which can be responsible for producing mycotoxins, is a concern and shows the need for post-production tests. Overall, there is a low prevalence of bacteria associated with hygiene, especially the Escherichia genus in alcoholic beverages such as palm wine, pito and burukutu, which may be due both to a low acidity and high ethanol content. However, the prevalence of hygiene indicator genera was higher in nonalcoholic drinks, probably because of incorrect practices during processing. The magnitude of the production and sales of unregulated local beverages in Nigeria has reached the stage where significant regulation and food safety standards are required to safeguard public health. An opportunity exists to monitor and characterize the microbial flora of the artisanal beverages using molecular methods at all stages of production and storage.

Coagulase-positive methicillin-resistant Staphylococcus aureus circulating in clinical mastitic goats in Bangladesh

BACKGROUND AND AIM

Staphylococcus aureus is argued as one of the principal organisms responsible for mammary gland infection in lactating goats, causing both clinical and subclinical mastitis. Being highly zoonotic potential, pathogen emergence of methicillin-resistant S. aureus (MRSA) has a significant clinical impact on treatment and management of clinical mastitis. We conducted a cross-sectional study to investigate the prevalence of coagulase-positive S. aureus (CoPS), antimicrobial resistance profile of Staphylococcus spp., prevalence of MRSA, and association between different clinical parameters with CoPS.

MATERIALS AND METHODS

A total of 67 clinical mastitic goats were sampled based on clinical examination and California mastitis test. Standard bacteriological methods were performed to isolate and identify Staphylococcus spp. CoPS were confirmed by nuc gene using polymerase chain reaction (PCR). All staphylococcal isolates were further examined for antimicrobial susceptibility testing by disk diffusion method. MRSA was confirmed based on mecA gene-based PCR.

RESULTS

Here, 49 (73.13%; 95% confidence interval [CI], 61.41-82.35) samples were positive for Staphylococcus spp., of which 17 (34.69%; 95% CI, 22.88-48.73) isolates were CoPS and rest of the isolates (32; 65.30%; 95% CI, 51.27-77.12) were identified as coagulase-negative Staphylococcus spp. (coagulase-negative staphylococci [CNS]). Both, CoPS and CNS isolates displayed the highest resistance against tetracycline (76.47% and 75%, respectively) and oxacillin (70.58% and 68.75%, respectively). Notably, all staphylococcal isolates were multidrug-resistant (showed resistance to ≥3 classes of antimicrobials). mecA gene was found in 6 (8.96%; 95% CI, 3.84-18.52) CoPS isolates indicating MRSA strains. Among different clinical parameters, presence of high body temperature (p<0.05), firm udder consistency (p<0.01), bloodstained milk (p<0.00), and pus in milk (p<0.00) were significantly associated with the presence of CoPS in mastitic caprine milk.

CONCLUSION

To the best of our knowledge, this is the first report of MRSA isolated from clinical caprine mastitis cases in Bangladesh. The findings of this study would help in cautious selection as well as administration of antimicrobials for therapeutic management of mastitic goats.

The Genomic Context for the Evolution and Transmission of Community-Associated Staphylococcus aureus ST59 Through the Food Chain

Sequence type 59 (ST59) is a predominant clonal lineage of community-acquired, methicillin-resistant Staphylococcus aureus (CA-MRSA) in Asia. Despite its increasing clinical relevance in China, the evolution and geographic expansion of ST59 has been relatively uncared for. Previous study has shown that ST59 was the predominant clone in food-related MRSA in China. This study compared the genomes of 87 clonal complex (CC) 59 S. aureus isolates sourced from food chain and infection cases to reconstruct the molecular evolution and geographical spread of ST59. Accordingly, three major sub-clades of ST59 were identified and these did not correlate with isolation source or location. Phylogenetic analysis estimated that ST59 in mainland China diverged from a most common recent ancestor around 1974, and most of the cases of cross-country transmission occurred between 1987 and 2000. Notably, two recent events of cross-country transmission through the food chain were observed, the isolates from these events diverged within relatively short time intervals. These isolates also showed high similarity in terms of their core genome, accessory genes, and antibiotic resistance patterns. These findings provide a valuable insight into the potential route of ST59 expansion in China and indicate a need for robust food chain surveillance to prevent the spread of this pathogen.

Overview of Evidence of Antimicrobial Use and Antimicrobial Resistance in the Food Chain

Antimicrobial resistance (AMR) is a global health problem. Bacteria carrying resistance genes can be transmitted between humans, animals and the environment. There are concerns that the widespread use of antimicrobials in the food chain constitutes an important source of AMR in humans, but the extent of this transmission is not well understood. The aim of this review is to examine published evidence on the links between antimicrobial use (AMU) in the food chain and AMR in people and animals. The evidence showed a link between AMU in animals and the occurrence of resistance in these animals. However, evidence of the benefits of a reduction in AMU in animals on the prevalence of resistant bacteria in humans is scarce. The presence of resistant bacteria is documented in the human food supply chain, which presents a potential exposure route and risk to public health. Microbial genome sequencing has enabled the establishment of some links between the presence of resistant bacteria in humans and animals but, for some antimicrobials, no link could be established. Research and monitoring of AMU and AMR in an integrated manner is essential for a better understanding of the biology and the dynamics of antimicrobial resistance.

Label-Free Quantitative Proteomics Reveals the Multitargeted Antibacterial Mechanisms of Lactobionic Acid against Methicillin-Resistant Staphylococcus aureus (MRSA) using SWATH-MS Technology

The objective of the present study was to reveal the antibacterial mechanism of lactobionic acid (LBA) against methicillin-resistant Staphylococcus aureus (MRSA) using quantitative proteomics by sequential window acquisition of all theoretical mass spectra (SWATH-MS) to analyze 100 differentially expressed proteins after LBA treatment. Furthermore, multiple experiments were conducted to validate the results of the proteomic analysis including reactive oxygen species (ROS), virulence-associated gene expression, and the relative quantification of target proteins and genes by parallel reaction monitoring and quantitative real-time PCR. Combining the ultrastructure observations, proteomic analysis, and our previous research, the mode of LBA action against MRSA was speculated as cell wall damage and loss of membrane integrity; inhibition of DNA repair and protein synthesis; inhibition of virulence factors and biofilm production; induction of oxidative stress; and inhibition of metabolic pathways. These results suggest potential applications for LBA in food safety and pharmaceuticals, considering its multitarget effects against MRSA.

Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) in bulk tank milk, livestock and dairy-farm personnel in north-central and north-eastern Greece: Prevalence, characterization and genetic relatedness

Recently, there has been an increased tendency towards raw-milk consumption, which may pose a consumer risk, due to the possible presence of human pathogenic microorganisms, such as Staphylococcus aureus and even methicillin-resistant S. aureus (MRSA). The prevalence of S. aureus and methicillin-resistant S. aureus (MRSA) was investigated in 40 dairy (cattle, sheep and goat) farms in northern Greece. S. aureus and MRSA were detected in 47.8% and 4.1% of the 387 samples (raw milk, farmers and animal samples) tested, respectively. Most (81.3%) of the MRSA isolates harbored the mecA gene, whereas the mecC or Panton-Valentine Leucocidin (PVL) genes were not detected. Seven spa types were identified, with t127 being the most prevalent. Spa type t034 (CC398) was isolated for the first time from livestock in Greece. Staphylococcal enterotoxin genes were detected in 93.8% of the MRSA isolates. The MRSA isolates were genetically diverse and were all capable of biofilm production. Our results confirm the lurking threat of MRSA in raw milk and dairy farms and suggest the need for surveillance programs starting at the farm level.

Hydrothermal-assisted synthesis of highly crystalline titania-copper oxide binary systems with enhanced antibacterial properties

Binary oxide systems containing TiO₂ and CuO were synthesized using hydrothermal treatment and shown to have enhanced antibacterial properties. A detailed investigation was made of the effect of the molar ratio of components (TiO₂:CuO = 7:3, 5:5, 3:7, 1:9) on the physicochemical parameters and antibacterial activity. Analysis of morphology (SEM, TEM and HRTEM) confirmed the presence of spherical and sheet-shaped particles. On the XRD patterns for the binary oxide materials, two crystalline forms (anatase and monoclinic CuO) were observed. It was found that an increase in CuO content led to a decrease in the BET surface area of the TiO₂-CuO binary oxide systems. The synthesized TiO₂-CuO materials exhibited very good antibacterial activity against both Gram-positive (methicillin-resistant Staphylococcus aureus and Bacillus cereus) and Gram-negative (Salmonella Enteritidis and Pseudomonas aeruginosa) bacteria. The obtained results show that TiO₂-CuO oxide materials may have applications in the biomedical and food industries.

Antimicrobial Activity and Mechanism of Action of Dracocephalum moldavica L. Extracts Against Clinical Isolates of Staphylococcus aureus

Background: Dracocephalum moldavica L. is a popular traditional medicine used by many countries, which has a wide range of pharmacological effects. The aim of this work was to investigate the antimicrobial effects of D. moldavica L. extracts against clinical isolates of Staphylococcus aureus. Our results demonstrated that the minimal inhibitory concentration (MIC) for 50 and 90% of S. aureus isolates (MIC₅₀ and MIC₉₀) of the ethyl acetate (EtOAc) fraction from D. moldavica L. ethanol extract were 780 and 1,065 μg/ml, respectively. We further observed that the EtOAc fraction disrupted 24-h biofilm caused cell membrane damage and irregular cell shape. Additionally, the EtOAc fraction showed slight to moderate toxic effects on human epidermal keratinocyte (HaCaT) cells. Moreover, the results of the differential proteome revealed that 231 proteins were upregulated, while 61 proteins were downregulated in S. aureus after treatment with the EtOAc fraction. The differentially expressed proteins were functionally categorized by the Gene Ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway. These proteins contribute to membrane damage, inhibition of biofilm formation, and changes in energy metabolism. Thus, the EtOAc fraction of D. moldavica L. ethanol extract, as a natural product, has the potential to be used as an antimicrobial agent to control the clinical isolates of S. aureus.

Efficacy of a Ruminal Bacteriocin Against Pure and Mixed Cultures of Bovine Mastitis Pathogens

Bacteriocins have been suggested as an alternative to conventional antibiotics for the prevention and treatment of mastitis infections. Predominant bacteria associated with bovine mastitis (n = 276 isolates) were evaluated for their susceptibility to bovicin HC5, a ruminal bacteriocin produced by Streptococcus equinus HC5. Bovicin HC5 inhibited most (> 80%) of the streptococcal and staphylococcal strains tested, but showed no effect against Escherichia coli strains. Susceptibility and resistance testing indicated that approximately 95% of the S. aureus strains were inhibited by concentrations of bovicin HC5 varying from 40 to 2560 AU ml^-1. Bovicin HC5 (62.50 AU ml^-1) also inhibited the growth of aerobic and anaerobic mixed cultures of S. aureus and S. agalactiae, but the combination with 0.25 mmol l^-1 of EDTA showed even greater bactericidal activity. These results demonstrate that bovicin HC5 is effective against the most prevalent pathogens found in contagious udder infections and could complement the use antibiotics in mastitis prophylaxis and therapy.

Inhibition of multidrug-resistant Staphylococci by sodium chlorate and select nitro- and medium chain fatty acid compounds

AIMS

Determine the antimicrobial effects of 5 μmol ml^-1 sodium chlorate, 9 μmol ml^-1 nitroethane or 2-nitropropanol as well as lauric acid, myristic acid and the glycerol ester of lauric acid Lauricidin^® , each at 5 mg ml^-1 , against representative methicillin-resistant staphylococci, important mastitis- and opportunistic dermal-pathogens of humans and livestock.

METHODS AND RESULTS

Three methicillin-resistant Staphylococcus aureus and two methicillin-resistant coagulase-negative staphylococci were cultured at 39°C in 5 μmol ml^-1 nitrate-supplemented half-strength Brain Heart Infusion broth treated without or with the potential inhibitors. Results revealed that 2-nitropropanol was the most potent and persistent of all compounds tested, achieving 58-99% decreases in mean specific growth rates and maximum optical densities when compared with untreated controls. Growth inhibition did not persist by cultures treated solely with chlorate or nitroethane, with adaptation occurring by different mechanisms after 7 h. Adaptation did not occur in cultures co-treated with nitroethane and chlorate. The medium chain fatty acid compounds had modest effects on all the staphylococci tested except the coagulase-negative Staphylococcus epidermidis strain NKR1.

CONCLUSIONS

The antimicrobial activity of nitrocompounds, chlorate and medium chain fatty acid compounds against different methicillin-resistant staphylococci varied in potency.

SIGNIFICANCE AND IMPACT OF THE STUDY

Results suggest that differential antimicrobial activities exhibited by mechanistically dissimilar inhibitors against methicillin-resistant staphylococci may yield potential opportunities to combine the treatments to overcome their individual limitations and broaden their activity against other mastitis and dermal pathogens.

Oxacillin-susceptible mecA-positive Staphylococcus aureus associated with processed food in Europe

We report for the first time an oxacillin-susceptible mecA-positive Staphylococcus aureus (OS-MRSA) associated with a processed food product in Europe. One isolate (MRSA-ST5-type V SCCmec) was found in cheese among 600 food samples confiscated from air passengers from international flights in Vienna Airport (Austria). Type V SCCmec strains do not harbor functional mecI-mecR1 genes and in such strains mecA expression is regulated by the bla system (blaI-blaR1-blaZ). It has been recently reported that malfunctions in the bla system lead to the constitutive expression of mecA. The OS-MRSA reported in this study harbored the bla system on a plasmid and one deletion occurred in the blaR1 gene causing a frameshift variant that lead to an incomplete BlaR1 protein. This finding highlights the potential role of food as a neglected route of dissemination of emerging MRSA variants.

Prevalence, antimicrobial susceptibility and characterization of Staphylococcus aureus and methicillin-resistant Staphylococcus aureus isolated from dairy industries in north-central and north-eastern Greece

Staphylococcus aureus is an important cause of food intoxication, whereas methicillin-resistant S. aureus (MRSA) constitutes a serious public-health concern due to its ability to colonize and infect humans and animals. S. aureus and MRSA have often been isolated from milk and dairy products. The objectives of this study were to estimate the prevalence and the antimicrobial resistance of S. aureus and MRSA in four Greek dairy industries, to identify virulence factors of MRSA isolates and to describe their genetic diversity, in order to identify possible epidemiological links and evaluate the risk of MRSA dissemination to the community. S. aureus was isolated from 67 out of 305 (22.0%) dairy industry samples (bulk-tank milk, dairy products, employee nasal swabs and equipment/surface swabs). Almost all (99%) of the 227 corresponding S. aureus isolates (approximately 4 isolates per positive sample) were resistant to at least one antimicrobial and 22% were multi-drug resistant (MDR). MRSA were isolated from 11 different samples (3.6%) originating from three of the dairy plants. All MRSA isolates were capable of forming biofilms, while staphylococcal enterotoxin (SE) genes were detected in 91% of the MRSA isolates, with sec being the most frequent. All of the MRSA isolates harbored the mecA gene but the mecC and Pandon-Valentine leucocidin (PVL) genes were not detected. Pulse-Field Gel Electrophoresis (PFGE) analysis showed genetic diversity among the MRSA isolates and indicated clonal circulation in one of the dairy plants. Seven spa types were identified among the MRSA isolates with the most prevalent (t065) isolated only in one dairy plant. Certain spa types (t065, t337 and t3536) were isolated for the first time in Greece. The presence of MDR, biofilm-forming and enterotoxigenic MRSA strains in dairy plant facilities may lead to their dissemination to the community, but also to staphylococcal food poisoning, when conditions are favorable. The study's findings highlight the need for continuous monitoring of the dairy production chain, the need for re-evaluating the implemented cleaning and sanitizing processes and the adoption of preventive strategies in order to minimize public-health risks.

Antibiotic Susceptibility profile of Staphylococcus aureus isolated from sausages in Meknes, Morocco

Background and Aims

Staphylococcus aureus is one of the most common causes of foodborne disease worldwide, due to the consumption of food contaminated by their toxins. This study aimed to determine the prevalence and the antimicrobial resistance of S. aureus isolated from sausages in Meknes city of Morocco.

Materials and Methods

A total of 156 samples (Beef sausages, Turkey sausages, and Artisanal sausages "Merguez") were collected from different shopping sites (butchery, supermarket, street vendors, and weekly market "Souk") and used for the isolation of S. aureus. All the isolated strains were tested for their antimicrobials resistance to 16 antibiotics.

Results

Our results showed the presence of S. aureus in 63 samples (40.38%). Furthermore, the antimicrobial resistance study showed that 84.13% of isolated S. aureus were resistant to streptomycin, 76.20% to tetracycline, 42.86% to ampicillin, 41.27% to doxycycline, 38.1% to penicillin G, and 19.05% to chloramphenicol with the presence of 25 different phenotypic profiles. However, all isolated strains were sensitive to oxacillin, cefoxitin, gentamicin, and vancomycin.

Conclusion

The findings of this study revealed consumption of sausages as a potential risk of foodborne poisonings because of its contamination with the multi-resistant strains of S. aureus. Moreover, this contamination is related to the season, sampling sites and the origin of the raw material.

Antimicrobial-resistant Staphylococcus aureus and MRSA prevalence among Korean families and household items

One-hundred-and-seventy-nine Staphylococcus aureus strains, collected from a total of 825 resident and household item samples in Korean homes nationwide, were tested, to survey the spread of antimicrobial-resistant S. aureus including the methicillin-resistant S. aureus (MRSA) strain. Antimicrobial resistance to sulfamethoxazole-trimethoprim (0.0%), teicoplanin (0.0%), tetracycline, vancomycin (0.0%,) chloramphenicol (0.0%), ciprofloxacin (1.1%), clindamycin (1.1%), amikacin (2.2%), gentamicin (8.4%), oxacillin (17.9%), erythromycin (21.8%), ampicillin (96.6%) and penicillin (96.6%), was detected by disk diffusion method and 7.3% (13/179) of the antimicrobial-resistant isolates, were multi-drug resistant (resistant to ≥3 antimicrobial classes). Nine of 32 oxacillin-resistant strains, were positive for the mecA gene and identified as MRSA, in 4 residents and 4 loofah samples, by polymerase chain reaction. These findings provide public health information and contribute to preventing circulation of antimicrobial-resistant strains in community settings including healthy homes.

Detection and Characterization of Staphylococcus aureus and Methicillin-Resistant S. aureus in Foods Confiscated in EU Borders

The aim of the study was to evaluate the potential role of the illegal entry of food in UE in the Methicillin-resistant S. aureus (MRSA) spread. We studied the prevalence and characteristics of Staphylococcus aureus and MRSA isolated from foods of animal origin confiscated from passengers on flights from 45 non-EU countries from 2012 to 2015 by the Border Authorities at Bilbao International Airport (Spain) and Vienna International Airport (Austria), as well as foods from open markets close to EU land borders. Of 868 food samples tested (diverse meat samples including antelope, duck, guinea pig, pork, rodents, turkey, dairy products, and eggs), 136 (15.7%) were positive for S. aureus and 26 (3.0%) for MRSA. All MRSA strains were mecA-positive. The prevalence of S. aureus-positive dairy samples among food confiscated at Bilbao International Airport was 64.6%, and this airport also had the highest value (11.8%) for MRSA-positive samples. The predominant sequence type was ST5 (30.8%), followed by ST8, ST1649, ST1, and other lineages were found to a lesser extent (ST7, ST22, ST72, ST97, and ST398). Six isolates tested positive for luk-PVL genes (SCCmec IV subtypes IVc and IVe). Enterotoxin profiling revealed that 19 MRSA strains were enterotoxigenic, harboring one or more se genes. The MRSA isolates positive for luk-PVL genes were not enterotoxigenic, and none of the isolates tested positive for enterotoxin E. We found 14 resistance profiles, and more than 69% of the MRSA isolates were resistant to three or more types of antimicrobial agents. This finding reveals both the wide diversity of the antimicrobial resistance found in the strains and the capacity to resist not only to beta-lactam drugs. One MRSA strain showed unusual characteristics: it was oxacillin-susceptible, harbored SCCmec V, and was positive for sed, seg, and sej but negative for PVL virulence factors. This study shows the presence of enterotoxigenic HA-, CA-, and LA-MRSA in foods illegally entering the EU, and highlights illegal importation of food as route of enterotoxigenic MRSA spread. Uncontrolled entry of food stuffs into the EU can be a relevant neglected route of MRSA dissemination.