Methicillin-resistant Staphylococcus aureus: a controversial food-borne pathogen

Prevalence and types of methicillin-resistant Staphylococcus aureus (MRSA) in meat and meat products from retail outlets and in samples of animal origin collected in farms, slaughterhouses and meat processing facilities. A review

Methicillin-resistant Staphylococcus aureus (MRSA) is a frequent cause of nosocomial and community infections, in some cases severe and difficult to treat. In addition, there are strains of MRSA that are specifically associated with food-producing animals. For this reason, in recent years special attention has been paid to the role played by foodstuffs of animal origin in infections by this microorganism. With the aim of gaining knowledge on the prevalence and types of MRSA in meat and meat products, a review was undertaken of work published on this topic since 2001, a total of 259 publications, 185 relating to meat samples from retail outlets and 74 to samples of animal origin collected in farms, slaughterhouses and meat processing facilities. Strains of MRSA were detected in 84.3% reports (156 out of 185) from retail outlets and 86.5% reports (64 out of 74) from farms, slaughterhouses and meat processing facilities, although in most of the research this microorganism was detected in under 20% of samples from retail outlets, and under 10% in those from farms, slaughterhouses and meat processing facilities. The meat and meat products most often contaminated with MRSA were pork and chicken. In addition to the mecA gene, it is crucial to take into consideration the mecB and mecC genes, so as to avoid misidentification of strains as MSSA (methicillin-susceptible Staphylococcus aureus). The great variety of methods used for the determination of MRSA highlights the need to develop a standardized protocol for the study of this microorganism in foods.

Development and mouse model evaluation of a new phage cocktail intended as an alternative to antibiotics for treatment of Staphylococcus aureus-induced bovine mastitis

Bovine mastitis is a prevalent infectious disease in dairy herds worldwide, resulting in substantial economic losses. Staphylococcus aureus is a major cause of mastitis in animals, and its antibiotic resistance poses challenges for treatment. Recently, renewed interest has focused on the development of alternative methods to antibiotic therapy, including bacteriophages (phages), for controlling bacterial infections. In this study, 2 lytic phages, vB_SauM_JDYN (JDYN) and vB_SauM_JDF86 (JDF86), were isolated from the cattle sewage effluent samples collected from dairy farms in Shanghai. The 2 phages have a broad bactericidal spectrum against Staphylococcus of various origins. Genomic and morphological analyses revealed that the 2 phages belonged to the Myoviridae family. Moreover, JDYN and JDF86 remained stable under a wide temperature and pH range and were almost unaffected in chloroform. In this study, we prepared a phage cocktail (PHC-1) which consisted of a 1:1:1 ratio of JDYN, JDF86, and SLPW (a previously characterized phage). We found that PHC-1 showed the strongest bacteriolytic effect and the lowest frequency of emergence of bacteriophage insensitive mutants compared with monophages. Bovine mammary epithelial cells and lactating mice mastitis models were used to evaluate the effectiveness of PHC-1 in vitro and in vivo, respectively. The results demonstrated that PHC-1 treatment significantly reduced bacterial load, alleviated inflammatory response, and improved mastitis pathology. Altogether, these results suggest that PHC-1 has the potential to treat S. aureus-induced bovine mastitis and that phage cocktails can combat antibiotic-resistant S. aureus infections.

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.

Bacitracin-resistant Staphylococcus aureus induced in chicken gut and in vitro under bacitracin exposure

It is common knowledge that prolonged and excessive use of antibiotics can lead to antimicrobial resistance. However, the characteristics and mechanism of resistant-bacteria induced by clinically recommended and prophylactic dose drugs remain largely unclear. This study aimed to observe the trends of drug resistance of the bacitracin-susceptible Staphylococcus aureus strain FS127 under exposure to bacitracin (BAC), which were induced in vitro and in chicken gut. Antimicrobial susceptibility testing was used to detect the susceptibility of S. aureus induced in vitro and in the chicken gut to gentamicin, chloramphenicol, tetracycline, doxycycline, penicillin and chloramphenicol. The research results showed that bacitracin could induce drug resistance in S. aureus both in vitro and in vivo. The bacitracin-resistance rate of S. aureus isolated from chicken gut was positively correlated with the dose and time of bacitracin administration. The findings revealed that bacitracin-resistant S. aureus induced in vivo had enhanced susceptibility to chloramphenicol but no such change in vitro. Meanwhile, RT-qPCR assay was used to detect the expression levels of vraD, braD, braR and bacA in typical strains with different bacitracin-resistance levels. It was found that BacA may play a key role in the bacitracin resistance of S. aureus. In conclusion, this work reveals the characteristics and mechanism of bacitracin-resistant S. aureus induced by bacitracin in vivo and in vitro respectively.

Occurrence and Characteristics of Toxigenic Staphylococcus aureus in Retail Foods in Iran

Staphylococcus aureus causes various toxigenic and invasive diseases in humans worldwide. This study examined the prevalence, virulence genes, and antibiotic resistance of S. aureus isolates collected from 894 retail food samples in Ardabil, Iran. Staphylococcal cassette chromosome mec (SCCmec), spa, and multilocus sequence typing methods were employed to further investigate the molecular characteristics of methicillin-resistant S. aureus (MRSA) isolates. The results revealed that 11.18% (n = 100) of food samples exhibited contamination with S. aureus (10.50% methicillin-sensitive S. aureus [MSSA] and 0.67% MRSA). Notably, raw minced meat (29.41%), Faloodeh (25%), and Olivier salad (21.42%) emerged as the most frequently contaminated food items. Among the 100 isolates of S. aureus, 94% were characterized as MSSA, with the remaining 6% identified as MRSA. The highest resistance was observed for penicillin (12%). MRSA isolates exhibited significantly higher resistance rates. Seventy-nine percent of the isolates were positive for sea, 14% for seb, 8% for a sec, and 0% for sed enterotoxin-encoding genes. Sixteen percent of isolates harbored two or more staphylococcal enterotoxin genes, simultaneously. Moreover, 97%, 94%, 24%, and 22% of isolates were positive for hla, hld, tst, and pvl virulence-encoding genes, respectively. No isolate was positive for the exfoliative toxins encoding eta and etb genes. MRSA isolates belonged to CC8 (n = 4) and CC22 (n = 2). Isolates in CC8 belonged to lineage ST239-MRSA-III and spa type t030; the isolates in CC22 belonged to ST22-MRSA-IV and spa types t310 and t223. In conclusion, a relatively high proportion of our retail food samples were contaminated with S. aureus. The high incidence of isolates with toxigenic genes raises serious health concerns. Furthermore, the presence of MRSA lineages linked to humans suggests that retail foods may be contaminated with human origin.

Analysis of Antimicrobial Resistance in Bacterial Pathogens Recovered from Food and Human Sources: Insights from 639,087 Bacterial Whole-Genome Sequences in the NCBI Pathogen Detection Database

Understanding the role of foods in the emergence and spread of antimicrobial resistance necessitates the initial documentation of antibiotic resistance genes within bacterial species found in foods. Here, the NCBI Pathogen Detection database was used to query antimicrobial resistance gene prevalence in foodborne and human clinical bacterial isolates. Of the 1,843,630 sequence entries, 639,087 (34.7%) were assigned to foodborne or human clinical sources with 147,788 (23.14%) from food and 427,614 (76.88%) from humans. The majority of foodborne isolates were either Salmonella (47.88%), Campylobacter (23.03%), Escherichia (11.79%), or Listeria (11.3%), and the remaining 6% belonged to 20 other genera. Most foodborne isolates were from meat/poultry (95,251 or 64.45%), followed by multi-product mixed food sources (29,892 or 20.23%) and fish/seafood (6503 or 4.4%); however, the most prominent isolation source varied depending on the genus/species. Resistance gene carriage also varied depending on isolation source and genus/species. Of note, Klebsiella pneumoniae and Enterobacter spp. carried larger proportions of the quinolone resistance gene qnrS and some clinically relevant beta-lactam resistance genes in comparison to Salmonella and Escherichia coli. The prevalence of mec in S. aureus did not significantly differ between meat/poultry and multi-product sources relative to clinical sources, whereas this resistance was rare in isolates from dairy sources. The proportion of biocide resistance in Bacillus and Escherichia was significantly higher in clinical isolates compared to many foodborne sources but significantly lower in clinical Listeria compared to foodborne Listeria. This work exposes the gaps in current publicly available sequence data repositories, which are largely composed of clinical isolates and are biased towards specific highly abundant pathogenic species. We also highlight the importance of requiring and curating metadata on sequence submission to not only ensure correct information and data interpretation but also foster efficient analysis, sharing, and collaboration. To effectively monitor resistance carriage in food production, additional work on sequencing and characterizing AMR carriage in common commensal foodborne bacteria is critical.

Protective mechanism of Paeonol on central nervous system

Cerebrovascular diseases involve neuronal damage, resulting in degenerative neuropathy and posing a serious threat to human health. The discovery of effective drug components from natural plants and the study of their mechanism are a research idea different from chemical synthetic medicines. Paeonol is the main active component of traditional Chinese medicine Paeonia lactiflora Pall. It widely exists in many medicinal plants and has pharmacological effects such as anti-atherosclerosis, antiplatelet aggregation, anti-oxidation, and anti-inflammatory, which keeps generally used in the treatment of cardiovascular and cerebrovascular diseases. Based on the therapeutic effects of Paeonol for cardiovascular and cerebrovascular diseases, this article reviewed the pharmacological effects of Paeonol in Alzheimer's disease, Parkinson's disease, stroke, epilepsy, diabetes encephalopathy, and other neurological diseases, providing a reference for the research of the mechanism of Paeonol in central nervous system diseases.

Direct microwave treatment enhances antioxidant and antibacterial properties of the seed extracts of Kékfrankos grapes

The Kékfrankos is the most frequently cultivated wine grape in Hungary, with a significant national and regional impact, resulting in considerable amounts of byproducts (e.g. pomace, seeds). To the best of our knowledge no research has been conducted on the antioxidant and antibacterial properties of its seed extracts (GSE). A novel apporach of applying direct microwave treatment on grape seeds was implemented for the first time to enhance antioxidant and antimicrobial properties of GSE. Antioxidant properties were assayed using the DPPH (2,2-diphenyl-1-picrylhydrazyl), FRAP (Ferric Reducing Antioxidant Power) and TPC (Folin-Ciocâlteu's Total Polyphenol Content) methods. Profile and content of polyphenols was studied using high-performance liquid chromatography/tandem mass spectrometry and matrix-assisted laser desorption/ionization mass spectrometry. Antibacterial properties were evaluated using Gram-positive Staphylococcus aureus (SA), methicillin-resistant Staphylococcus aureus (ST239) (MRSA) and Gram-negative Escherichia coli (EC) bacteria strains. Results proved that the mild direct microwave treatment of grape seeds significantly increased total polyphenol, (+)-catechin, (-)-epicatechin as well as antioxidant capacity levels by 20-30 % compared to untreated samples and resulted the best antibacterial properties based on bacterial growth curves (SA and MRSA: 0.015625 mg/mL, EC: 0.25 mg/mL). Results justify the importance of further pharmacological investigations on Kékfrankos grape seed extracts and that the direct microwave treatment of grape seeds is an innovative approach for the fast and cost efficient improvement of the antibacterial properties of grape seed extracts.

Pulsed-Field Gel Electrophoresis Analysis of Bovine Associated Staphylococcus aureus: A Review

For decades now, DNA fingerprinting by means of pulsed-field gel electrophoresis (PFGE) continues to be the most widely used to separate large DNA molecules and distinguish between different strains in alternating pulses. This is done by isolating intact chromosomal DNA and using restriction enzymes with specific restriction sites to generate less than 30 restriction fragments from 50 Kb to 10 Mbp. These results make clone-specific band profiles easy to compare. Specialized equipment is required for the optimization of DNA separation and resolution, among which a contour-clamped homogeneous electric field (CHEF) apparatus is the most commonly used. As a result, the PFGE analysis of a bacterial genome provides useful information in terms of epidemiological investigations of different bacterial pathogens. For Staphylococcus aureus subtyping, despite its limitations and the emergence of alternative methods, PFGE analysis has proven to be an adequate choice and the gold standard for determining genetic relatedness, especially in outbreak detection and short-term surveillance in the veterinary field.

Occurrence and Patterns of Enterotoxin Genes, spa Types and Antimicrobial Resistance Patterns in Staphylococcus aureus in Food and Food Contact Surfaces in Singapore

Staphylococcus aureus contamination of food and food contact surfaces is a public health concern given its virulent and antimicrobial-resistant properties worldwide. In this study, a total of 181 MSSA isolates were analyzed for SE genes, antimicrobial resistance patterns, and spa types. Overall, 24.9% of isolates were positive for SE gene detection, with sea being the most prevalent classical SE (18.8%). The most predominant sample sources for SE gene contamination were hand swabs for sea (6/48), meat dishes for seb (3/14) and seafood dishes for sec (2/24). Antimicrobial resistance was also observed at relatively high frequencies for the clinically important antibiotics penicillin G and ampicillin (both 54.7%), followed by tetracycline (14.9%) and azithromycin (8.8%). In addition, characterization of spa types revealed spa type t5078 to be the most predominant (40.3%), with significant associations between spa types t127 and t5521 and the sea gene. This study offers insights into the enterotoxin gene and antimicrobial resistance profiles of S. aureus in cooked or ready-to-eat food to inform future surveillance and epidemiological studies.

Antibacterial activity of 2-hydroxy-4-methoxybenzaldehyde and its possible mechanism against Staphylococcus aureus

AIM

Staphylococcus aureus causes several complicated infections. Despite decades of research on developing new antimicrobials, methicillin-resistant S. aureus (MRSA) remains a global health problem. Hence, there is a dire need to identify potent natural antibacterial compounds as an alternative to antimicrobials. In this light, the present work divulges the antibacterial efficacy and the action mechanism of 2-hydroxy-4-methoxybenzaldehyde (HMB) isolated from Hemidesmus indicus against S. aureus.

METHODS AND RESULTS

Antimicrobial activity of HMB was assessed. HMB exhibited 1024 µg ml-1 as the minimum inhibitory concentration (MIC) and 2 × MIC as the minimum bactericidal concentration against S. aureus. The results were validated by spot assay, time kill, and growth curve analysis. In addition, HMB treatment increased the release of intracellular proteins and nucleic acid contents from MRSA. Additional experiments assessing the structural morphology of bacterial cells using SEM analysis, β-galactosidase enzyme activity, and the fluorescence intensities of propidium iodide and rhodamine123 dye divulged that the cell membrane as one of the targets of HMB to hinder S. aureus growth. Moreover, the mature biofilm eradication assay revealed that HMB dislodged nearly 80% of the preformed biofilms of MRSA at the tested concentrations. Further, HMB treatment was found to sensitize MRSA cells upon combining tetracycline treatment.

CONCLUSIONS

The present study suggests that HMB is a promising compound with antibacterial and antibiofilm activities and could act as a lead structure for developing new antibacterial drugs against MRSA.

Staphylococcus aureus in the Processing Environment of Cured Meat Products

The presence of Staphylococcus aureus in six dry-cured meat-processing facilities was investigated. S. aureus was detected in 3.8% of surfaces from five facilities. The occurrence was clearly higher during processing (4.8%) than after cleaning and disinfection (1.4%). Thirty-eight isolates were typified by PFGE and MLST. Eleven sequence types (STs) were defined by MLST. ST30 (32%) and ST12 (24%) were the most abundant. Enterotoxin genes were detected in 53% of isolates. The enterotoxin A gene (sea) was present in all ST30 isolates, seb in one ST1 isolate, and sec in two ST45 isolates. Sixteen isolates harbored the enterotoxin gene cluster (egc) with four variations in the sequence. The toxic shock syndrome toxin gene (tst) was detected in 82% of isolates. Regarding antimicrobial resistance, twelve strains were susceptible to all the antibiotics tested (31.6%). However, 15.8% were resistant to three or more antimicrobials and, therefore, multidrug-resistant. Our results showed that in general, efficient cleaning and disinfection procedures were applied. Nonetheless, the presence of S. aureus with virulence determinants and resistance to antimicrobials, particularly multidrug-resistant MRSA ST398 strains, might represent a potential health hazard for consumers.

The use of aminopenicillins in animals within the EU, emergence of resistance in bacteria of animal and human origin and its possible impact on animal and human health

Aminopenicillins have been widely used for decades for the treatment of various infections in animals and humans in European countries. Following this extensive use, acquired resistance has emerged among human and animal pathogens and commensal bacteria. Aminopenicillins are important first-line treatment options in both humans and animals, but are also among limited therapies for infections with enterococci and Listeria spp. in humans in some settings. Therefore, there is a need to assess the impact of the use of these antimicrobials in animals on public and animal health. The most important mechanisms of resistance to aminopenicillins are the β-lactamase enzymes. Similar resistance genes have been detected in bacteria of human and animal origin, and molecular studies suggest that transmission of resistant bacteria or resistance genes occurs between animals and humans. Due to the complexity of epidemiology and the near ubiquity of many aminopenicillin resistance determinants, the direction of transfer is difficult to ascertain, except for major zoonotic pathogens. It is therefore challenging to estimate to what extent the use of aminopenicillins in animals could create negative health consequences to humans at the population level. Based on the extent of use of aminopenicillins in humans, it seems probable that the major resistance selection pressure in human pathogens in European countries is due to human consumption. It is evident that veterinary use of these antimicrobials increases the selection pressure towards resistance in animals and loss of efficacy will at minimum jeopardize animal health and welfare.

Antibiotic Resistance in Selected Emerging Bacterial Foodborne Pathogens-An Issue of Concern?

Antibiotic resistance (AR) and multidrug resistance (MDR) have been confirmed for all major foodborne pathogens: Campylobacter spp., Salmonella spp., Escherichia coli and Listeria monocytogenes. Of great concern to scientists and physicians are also reports of antibiotic-resistant emerging food pathogens-microorganisms that have not previously been linked to food contamination or were considered epidemiologically insignificant. Since the properties of foodborne pathogens are not always sufficiently recognized, the consequences of the infections are often not easily predictable, and the control of their activity is difficult. The bacteria most commonly identified as emerging foodborne pathogens include Aliarcobacter spp., Aeromonas spp., Cronobacter spp., Vibrio spp., Clostridioides difficile, Escherichia coli, Mycobacterium paratuberculosis, Salmonella enterica, Streptocccus suis, Campylobacter jejuni, Helicobacter pylori, Listeria monocytogenes and Yersinia enterocolitica. The results of our analysis confirm antibiotic resistance and multidrug resistance among the mentioned species. Among the antibiotics whose effectiveness is steadily declining due to expanding resistance among bacteria isolated from food are β-lactams, sulfonamides, tetracyclines and fluoroquinolones. Continuous and thorough monitoring of strains isolated from food is necessary to characterize the existing mechanisms of resistance. In our opinion, this review shows the scale of the problem of microbes related to health, which should not be underestimated.

Correlating the physico-chemical properties of two conventional glazed porcelain stoneware tiles in relation to cleanability and sanitization

Keeping surfaces clean can reduce the spread of infections. In particular, to decrease the potential for SARS CoV-2 contamination, performing disinfection of high-touching surfaces. Several ceramic tiles and porcelain stoneware tiles with antimicrobial properties are already available on the market. However, the widespread use of antimicrobial glazed stoneware tiles may require to replace the ceramic surfaces already present in many buildings. The unfeasibility of such replacement can be due to both product durability (lifetime of a tile is usually long) and/or monetary restrictions. Furthermore, as porcelain stoneware per se does not have antimicrobial activity, these materials are fabricated by adding chemical agents able to provide antimicrobial properties. This approach requires a compatibility between the antimicrobial agents and the glaze formulation, as well as a careful control of the firing cycle and the final properties of the ceramic products. It follows that the final cost of antimicrobial tiles is not competitive with that of conventional tiles. In the latter, the persistence of potential pathogens on the surfaces is a crucial problem to face: the longer a pathogen survives on a surface, the longer it may be a source of transmission and thus endanger susceptible subjects. In this work, bacteria's capacity to adhere and to be effectively removed from two conventional glazed porcelain stoneware tiles (under dirty and clean conditions) was investigated. Two different glazes were tested, one mainly glassy (glossy) and the other mainly crystalline (matt). The sanitization procedures were carried out by chemical and chemo-mechanical procedures. The results showed that chemo-mechanical sanitization was the most effective, and the best results could be obtained on the stoneware tiles coated with the mainly glassy glaze, with the lowest porosity and the lower roughness values and water contact angles, especially under clean conditions.

Antibacterial, Antioxidant, and in silico NADPH Oxidase Inhibition Studies of Essential Oils of Lavandula dentata against Foodborne Pathogens

Food is always subjected to microbial infection and lipid peroxidation, which frequently leads to serious food intoxications. In the present study, essential oils (EOs) extracted from Lavandula dentata Moroccan species and its major component (linalool) were chemically characterized and their antioxidant potential and antibacterial properties against foodborne pathogenic bacteria were examined. EOs phytochemical profile was carried out using gas chromatography-mass spectrometry analysis (GC-MS). The antioxidant potential was evaluated, in vitro, by use of the β-carotene discoloration assay and in silico vs. NADPH oxidase enzymatic complex as an antioxidant marker. The antibacterial proprieties were assessed by use of minimal inhibitory concentration (MIC) and disc diffusion methods, against Gram (-) bacteria (Pseudomonas aeruginosa, Salmonella enterica, and Escherichia coli) and Gram (+) bacteria (Bacillus subtilis and Staphylococcus aureus). Linalool (49.71%) was the major component among the eighteen components identified in Lavandula dentate EO, followed by camphor (14.36%) and borneol (8.21%). The studied EO and linalool compounds showed important antioxidant activity through the β-carotene discoloration test with IC₅₀ values of 35.72 ± 1.21 mg/mL and 30.32 ± 1.23 mg/mL, respectively. Among all the analyzed compounds of lavender EOs, thymol, carvacrol, and α-terpineol were the most active compounds against NADPH oxidase with a glide score of -6.483, -6.17, and -4.728 kcal/mol, respectively. 2D and 3D views showed the formation of hydrogen bonds between the most active compounds and the active site of NADPH oxidase. The antibacterial data showed a significant activity of Lavandula dentata essences against tested foodborne pathogenic bacteria, especially against S. aureus and B. subtilis. Linalool proved active toward the same bacteria and had closer activity to that of lavender essential oil. In light of the obtained findings, the essential oil of Lavandula dentata Moroccan species can be used in the packaging sector as a promising natural food conservative to limit lipid oxidation and treat foodborne infections.

Anti-biofilm effects of sinomenine against Staphylococcus aureus

Staphylococcus aureus is a gram-positive foodborne pathogen capable of forming strong biofilms. This study identified that anti-biofilm natural compound against S. aureus. Sinomenine, a natural compound, showed significantly reduced biofilm formation (31.97-39.86%), but no effect on bacterial growth was observed. The dispersion of preformed biofilms was observed by confocal laser scanning microscopy (CLSM). qRT-PCR revealed that sinomenine treatment significantly up-regulated agrA by 3.8-fold and down-regulated icaA gene by 3.1-fold. These indicate that sinomenine treatment induces biofilm dispersal due to cell-cell adhesion, polysaccharide intercellular adhesin (PIA), and phenol-soluble modulin (PSM) peptides production. Our results suggest that sinomenine can be used as a promising agent for effectively controlling biofilm formation and dispersion, thereby making S. aureus more susceptible to the action of antimicrobial agents.

Prevalence, multiple antibiotic resistance and virulence profile of methicillin-resistant Staphylococcus aureus (MRSA) in retail poultry meat from Edo, Nigeria

Introduction

Staphylococcus aureus causes staphylococcal food poisoning and several difficult-to-treat infections. The occurrence and dissemination of methicillin-resistance S. aureus (MRSA) in Nigeria is crucial and well documented in hospitals. However, findings on MRSA from meat in the country are yet to be adequately reported. The current study determined the prevalence, virulence profile and antibiogram characteristics of MRSA from a raw chicken product from retail outlets within Edo.

Methods

A total of 368 poultry meat samples were assessed for MRSA using a standard culture-based approach and characterized further using a molecular method. The antimicrobial susceptibility profile of the isolates was determined using the disc diffusion method. The biofilm profile of the isolates was assayed via the crystal violet microtitre-plate method. Virulence and antimicrobial resistance genes were screened using polymerase chain reaction via specific primers.

Results

Of the samples tested, 110 (29.9%) were positive for MRSA. All the isolates were positive for deoxyribonuclease (DNase), coagulase and beta-hemolysis production. Biofilm profile revealed 27 (24.55%) weak biofilm formers, 18 (16.36%) moderate biofilm formers, and 39 (35.45%) strong biofilm formers. The isolates harboured 2 and ≤17 virulence genes. Enterotoxin gene profiling revealed that 100 (90.9%) isolates harboured one or more genes. Resistance against the tested antibiotics followed the order: tetracycline 64(58.2%), ciprofloxacin 71(64.6%), trimethoprim 71(64.6%) and rifampin 103(93.6%). A total of 89 isolates were multidrug-resistant, while 3 isolates were resistant to all 22 antibiotics tested. The isolates harboured antimicrobial-resistant determinants such as methicillin-resistant gene (mecA), tetracycline resistance genes (tetK, tetL), erythromycin resistance genes (ermA, ermC), trimethoprim resistance gene (dfrK). All the staphylococcal cassette chromosome mec (SCCmec) IVa and SCCmec V positive isolates harboured the Panton-Valentine Leukocidin Gene (PVL).

Conclusion

In conclusion, S. aureus was resistant to commonly used antibiotics; a concern to public health concerning the transmission of these pathogens after consuming these highlight the significance of antimicrobial and enterotoxigenic monitoring of S. aureus in food chains.

Prevalence of staphylococcal toxin in food contaminated by Staphylococcus spp.: Protocol for a systematic review with meta-analysis

BACKGROUND

Food contamination by Staphylococcus spp. enterotoxigenic strains is quite common and despite underreporting caused by the short duration of clinical symptoms and lack of medical care, staphylococcal food poisoning is one of the most common Foodborne Diseases (FBD) in the world. This study describes a systematic review protocol with meta-analysis on the prevalence and types of staphylococcal enterotoxins in food, and the profile of contaminated foods.

METHODS

The research will be conducted through the selection of studies reporting the analysis of staphylococcal enterotoxins in food contaminated by Staphylococcus spp. Searches will happen on the following databases: Medline (OVID), GALE, Science Direct, CAB Direct (CABI), Google Scholar, in addition to manual search in the list of references of articles, directory of theses and dissertations, and countries' health agencies. Reports will be imported into the application Rayyan. Two researchers will independently select studies and extract data, and a third reviewer will solve conflicting decisions. The primary outcome will be the identification of staphylococcal enterotoxins in food, and the secondary outcomes will include staphylococcal enterotoxin types and foods involved. To assess the risk of bias in the studies, the tool developed by the Joanna Briggs Institute (JBI) will be used. For data synthesis, a meta-analysis will be performed. However, in case that is not possible, a narrative synthesis of the most relevant results will be carried out.

DISCUSSION

This protocol will serve as the basis for a systematic review that aims to relate the results of existing studies on the staphylococcal enterotoxin prevalence and types in food, and the profile of the contaminated foods. The results will broaden the perception of food safety risks, highlight existing literature gaps, contribute to the study of the epidemiological profile and may guide the allocation of health resources for the development of preventive measures related.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration number: CRD42021258223.

First comparative genomic characterization of the MSSA ST398 lineage detected in aquaculture and other reservoirs

Staphylococcus aureus ST398 can cause diseases in several different animals. In this study we analyzed ten S. aureus ST398 previously collected in three different reservoirs in Portugal (humans, gilthead seabream from aquaculture and dolphin from a zoo). Strains tested against sixteen antibiotics, by disk diffusion or minimum inhibitory concentration, showed decreased susceptibility to benzylpenicillin (all strains from gilthead seabream and dolphin) and to erythromycin with an iMLS_B phenotype (nine strains), and susceptibility to cefoxitin (methicillin-susceptible S. aureus, MSSA). All strains from aquaculture belonged to the same spa type, t2383, whereas strains from the dolphin and humans belonged to spa type t571. A more detailed analysis using single nucleotide polymorphisms (SNPs)-based tree and a heat map, showed that all strains from aquaculture origin were highly related with each other and the strains from dolphin and humans were more distinct, although they were very similar in ARG, VF and MGE content. Mutations F3I and A100V in glpT gene and D278E and E291D in murA gene were identified in nine fosfomycin susceptible strains. The blaZ gene was also detected in six of the seven animal strains. The study of the genetic environment of erm(T)-type (found in nine S. aureus strains) allowed the identification of MGE (rep13-type plasmids and IS431R-type), presumably involved in the mobilization of this gene. All strains showed genes encoding efflux pumps from major facilitator superfamily (e.g., arlR, lmrS-type and norA/B-type), ATP-binding cassettes (ABC; mgrA) and multidrug and toxic compound extrusion (MATE; mepA/R-type) families, all associated to decreased susceptibility to antibiotics/disinfectants. Moreover, genes related with tolerance to heavy metals (cadD), and several VF (e.g., scn, aur, hlgA/B/C and hlb) were also identified. Insertion sequences, prophages, and plasmids made up the mobilome, some of them associated with ARG, VF and genes related with tolerance to heavy metals. This study highlights that S. aureus ST398 can be a reservoir of several ARG, heavy metals resistance genes and VF, which are essential in the adaption and survival of the bacterium in the different environments and an active agent in its dissemination. It makes an important contribution to understanding the extent of the spread of antimicrobial resistance, as well as the virulome, mobilome and resistome of this dangerous lineage.

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.

Plasmid-Coded Linezolid Resistance in Methicillin-Resistant Staphylococcus aureus from Food and Livestock in Germany

Resistance of methicillin-resistant Staphylococcus aureus (MRSA) from food and livestock to last resort antibiotics such as linezolid is highly concerning, since treatment options for infections in humans might be diminished. Known mechanisms of linezolid resistance include point mutations in the 23S rRNA gene and in the ribosomal proteins L3, L4 and L22 as well as an acquisition of the cfr, optrA or poxtA gene. The objective of our study was to characterize antimicrobial resistance (AMR) determinants and phylogenetic relationships among linezolid-resistant (LR-) MRSA from food and livestock. In total, from more than 4000 incoming isolates in the years 2012 to 2021, only two strains from 2015 originating from pig samples exhibited linezolid resistance in the antimicrobial susceptibility testing with MICs of ≥8 mg/L. These LR-MRSA were characterized in detail by whole-genome sequencing and phylogenetic analyses using cgMLST. The LR-MRSA strains showed resistances to ten and eight different antibiotics, respectively. Both strains harbored plasmid-coded cfr genes mediating the linezolid resistance. The cfr genes showed identical sequences in both strains. In addition to the cfr gene, genes for phenicol and clindamycin resistance were detected on the respective plasmids, opening the possibility for a co-selection. The LR-MRSA differed distantly in the phylogenetic analyses and also to other MRSA from pig samples in the year 2015. In conclusion, the occurrence of LR-MRSA in food and livestock seems to be very rare in Germany. However, carriage of plasmids with linezolid resistance determinants could lead to further linezolid-resistant strains by horizontal gene transfer.

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.

Suppression of Methicillin-Resistant Staphylococcus aureus and Reduction of Other Bacteria by Black Soldier Fly Larvae Reared on Potato Substrate

Larvae of black soldier flies, Hermetia illucens, are increasingly used for biological conversion of animal and plant wastes into ingredients of animal feeds on an industrial scale. The presence of pathogenic microorganisms in harvested larvae may be a serious problem for wide-scale adoption of this technology. Fortunately, black soldier fly larvae may have some antimicrobial properties. Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterium associated with various environments that can be pathogenic to humans and farmed animals. We tested whether black soldier fly larvae suppress MRSA on potato substrate. Autoclaved potatoes containing black soldier fly larvae (P+BSFL), potatoes inoculated with MRSA and containing black soldier fly larvae (P+MRSA+BSFL), and potatoes inoculated with MRSA (P+MRSA) were incubated in glass jars. Substrate samples were taken after 3 and 7 days of incubation and plated on Trypticase soy agar (TSA) and Staphylococcus medium 110 agar (SA) to quantify total bacteria and MRSA, respectively. DNA was extracted from potato substrates on both days and sequenced to assess bacterial and fungal diversity using 515F/806R and internal transcribed spacer (ITS) 1/2 primers, respectively, and QIIME 2.0 software. Both total bacterial and MRSA-specific CFU were reduced in the presence of black soldier fly larvae, with a larger reduction for the latter. Twenty-five bacterial genera and 3 fungal genera were detected. Twenty bacterial genera were shared among the treatments and the days, but their relative abundances often varied. Among the most abundant genera, only Enterococcus and Lactococcus were universally present. Our findings confirm antimicrobial properties of black soldier fly larvae. IMPORTANCE Larvae of black soldier flies, Hermetia illucens, may be used to provide an environmentally sustainable and economically viable method for biological conversion of animal and plant wastes into ingredients of animal feeds on an industrial scale. However, contamination of harvested larvae by pathogenic microorganisms inhabiting decaying substrates may be a serious problem for wide-scale adoption of this technology. Fortunately, black soldier fly larvae may have some antimicrobial properties, including suppression of several common pathogens. Our study showed that such a suppression applies to methicillin-resistant Staphylococcus aureus, which is a ubiquitous bacterium pathogenic to animals (including humans).

Four Novel Leaderless Bacteriocins, Bacin A1, A2, A3, and A4 Exhibit Potent Antimicrobial and Antibiofilm Activities against Methicillin-Resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is a major bacterial pathogen that causes hospital- and community-acquired infections. Owing to its multidrug resistance, it is imperative to develop new antimicrobial agents to treat MRSA infections. In this study, using genome mining analysis and a culture-based screening method to detect bacteriocin activity, we screened a strain, Bacillus sp. TL12, which harbored a putative leaderless bacteriocin gene cluster (bac gene cluster) and exhibited potent anti-MRSA activity. The antimicrobial agents, products of the bac gene cluster, were purified and identified as four novel leaderless bacteriocins: bacin A1, A2, A3, and A4. Bacin A2 was evaluated as a representative antimicrobial agent and showed remarkable antimicrobial activity against S. aureus, MRSA, and the foodborne pathogens Listeria monocytogenes and Bacillus cereus. Mechanistic experiments revealed that bacin A2 damaged cell membranes and exhibited bactericidal activity against MRSA. Bacin A2 effectively inhibited the formation of S. aureus and MRSA biofilms (>0.5× MIC) and killed the cells in their established biofilms (>4× MIC). The hemolytic and NIH/3T3 cytotoxicity assay results for bacin A2 confirmed its biosafety. Thus, bacins have potential as alternative antimicrobial agents for treating MRSA infections. IMPORTANCE Methicillin-resistant Staphylococcus aureus (MRSA) is a major human pathogen that is difficult to treat because of its resistance to several widely used antibiotics. The present study aimed to identify novel anti-MRSA bacteriocins in a prominent producer of bacteriocins, Bacillus cereus group. Four novel leaderless bacteriocins, bacin A1, A2, A3, and A4, which show potent bactericidal effect against S. aureus and MRSA, were identified in Bacillus sp. TL12. Moreover, bacins inhibited biofilm formation and killed cells in the established biofilms of S. aureus and MRSA. These findings suggest that bacins are promising alternatives to treat MRSA infections.

Whole-Genome Analysis of Staphylococcus aureus Isolates from Ready-to-Eat Food in Russia

This study provides a thorough investigation of a diverse set of antimicrobial resistant (AMR) Staphylococcus aureus isolates collected from a broad range of ready-to-eat (RTE) food in various geographic regions of Russia ranging from Pskov to Kamchatka. Thirty-five isolates were characterized using the whole genome sequencing (WGS) analysis in terms of clonal structure, the presence of resistance and virulence determinants, as well as plasmid replicon sequences and CRISPR/Cas systems. To the best of our knowledge, this is the first WGS-based surveillance of Russian RTE food-associated S. aureus isolates. The isolates belonged to fifteen different multilocus sequence typing (MLST)-based types with a predominant being the ones of clonal complex (CC) 22. The isolates studied can pose a threat to public health since about 40% of the isolates carried at least one enterotoxin gene, and 70% of methicillin-resistant (MRSA) isolates carried a tsst1 gene encoding a toxin that may cause severe acute disease. In addition, plasmid analysis revealed some important characteristics, e.g., Rep5 and Rep20 plasmid replicons were a “signature” of MRSA CC22. By analyzing the isolates belonging to the same/single strain based on cgMLST analysis, we were able to identify the differences in their accessory genomes marking their dynamics and plasticity. This data is very important since S. aureus isolates studied and RTE food, in general, represent an important route of transmission and dissemination of multiple pathogenic determinants. We believe that the results obtained will facilitate performing epidemiological surveillance and developing protection measures against this important pathogen in community settings.

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

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

Occurrence and Characteristics of Staphylococcus aureus Isolated from Dairy Products

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

Antibacterial and Biofilm Degradation Effects of Hungarian Honeys Linked With Botanical Origin, Antioxidant Capacity and Mineral Content

The aim of the study was to assess the impact of four unifloral honeys on the food-borne pathogens Pseudomonas aeruginosa and Staphylococcus aureus, by analyzing the honeys’ antibacterial and biofilm degradation effects, as well as their antioxidant activity and element content. Linden and milkweed honeys represented light colored honeys, while goldenrod and chestnut honeys the darker ones. The botanical origin of the honeys and the relative frequency of their pollen types were established with melissopalynological analysis. The antioxidant capacities were calculated by two single electron transfer based methods (TRC – Total Reducing Capacity and TEAC – Trolox Equivalent Antioxidant Capacity) and a hydrogen atom transfer based assay (ORAC – Oxygen Radical Absorbance). The amount of four main macro- and two microelements was quantified. The antibacterial activity was determined by minimum inhibitory concentration (MIC) and membrane degradation assays. Furthermore, the biofilm degradation power of the samples was studied as well. The light colored linden honey with the lowest TRC and TEAC, but with the highest ORAC antioxidant activity and high element content showed the best antibacterial and biofilm degradation effects. Meanwhile, the dark colored chestnut honey with significantly higher single electron transfer based antioxidant capacities, with high element content, but lower ORAC showed significantly higher MIC and lower membrane degradation activity than linden honey. In case of biofilm degradation, both honey types gave similarly high inhibitory effect. Goldenrod honey was similarly effective regarding its MIC properties like chestnut honey, but had significantly lower antioxidant potential and ability to disrupt bacterial membranes and biofilms. Milkweed honey was the honey type with the lowest bioactivity and element content. The honeys, unequivocally characterized by their antioxidant characters and element content, displayed different antibacterial and biofilm degradation effects. In addition, some honey traits were found to be good predictors of the antimicrobial potential of honeys: ORAC assay showed correlation with the MIC values of both bacteria, and strict correlation was found between the mineral content and the antibiofilm activity of the studied honeys. Our studies indicate that unifloral honeys, such as linden and chestnut honeys, are plant-derived products with great potential as antimicrobial agents in food preservation, exhibiting remarkable antibacterial activity against food-borne pathogens.

Antibiofilm mechanism of a novel milk-derived antimicrobial peptide against Staphylococcus aureus by down regulating agr quorum sensing system

AIMS

Staphylococcus aureus has emerged as a serious threat to food safety owing to biofilm formation. The study aimed to examine antibiofilm mechanism of a novel milk-derived antimicrobial peptide BCp12 against it.

METHODS AND RESULTS

Anti-biofilm activity of BCp12 was studied by crystal violet staining, MTT assay, motility, SEM and CLSM. TMT proteome, real-time PCR, and molecular docking in silico were conducted to evaluate the mechanism of BCp12 against S. aureus biofilm. The results showed that BCp12 had significant anti-biofilm activity at 1×MIC and sub-MIC. BCp12 induced the dispersion of structure of S. aureus biofilm BCp12 inhibited the movement of S. aureus. A total of 703 proteins were down-regulated and 334 proteins were up-regulated after BCp12 treatment. The proteins (agrA, agrB, agrC, and psmβ) of the QS systems were down-regulated. Additionally, the expression of the agr-related genes, agrA, agrB, agrC, and psmβ were down-regulated. BCp12 was bound to the receptor proteins agrA and agrC through hydrogen bonds and π-π bonds.

CONCLUSIONS

The results indicated the antibiofilm activity of BCp12 and it inhibiting biofilm formation by interfering agr QS system.

SIGNIFICANCE AND IMPACT OF STUDY

BCp12 has the potential to be a novel anti-biofilm agent against S. aureus biofilm and used in the food industry.

Prevalence and Characterisation of Multiresistant Bacterial Strains Isolated in Pigs from the Island of Tenerife

Background: Antibiotic-resistant bacteria can circulate among human and animal populations through direct contact with animals, as well as via food and the environment. The purpose of this study was to examine the prevalence and characterisation of multiresistant bacteria in pig samples. Methods: 224 samples of pig livestock were taken at the slaughterhouse on the island of Tenerife. A nasal and a rectal sample were collected from each pig. The presence of methicillin-resistant Staphylococcus aureus (MRSA), methicillin-resistant Staphylococcus coagulase-negative (MRCoNS), vancomycin-resistant Enterococcus (VRE), extended-spectrum ß-lactamase-producing Enterobacteriaceae (BLEE), carbapenemase-producing Enterobacteriaceae (CPE), and colistin-resistant Enterobacteriaceae was investigated. The resistance genes of the isolated bacteria were characterised by specific PCRs depending on the microorganism to be studied, and in vitro antimicrobial resistance was determined using the broth microdilution method (Vitek^®2 system bioMérieux^®, Nurtingen, Germany). Results: MRSA prevalence was 73.21% (164 isolates). MRCoNS prevalence was 9.8% (22 isolates), S. sciuri being the prevalent species. Six isolates presented a 2.7% prevalence of extended-spectrum ß-lactamase-producing Escherichia coli (BLEE) in the CTX-M-1 group. No vancomycin-resistant Enterococcus (VRE), carbapenemase-producing Enterobacteriaceae (CRE), or colistin-resistant Enterobacteriaceae were isolated. Conclusion: we found a high presence of multiresistant bacteria, suggesting the need for increased control and surveillance of this type of strains in pig livestock and a better understanding of the possible transmission routes of these microorganisms through livestock products.

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

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

Comparative Extraction of Phenolic Compounds from Olive Leaves Using a Sonotrode and an Ultrasonic Bath and the Evaluation of Both Antioxidant and Antimicrobial Activity

A sonotrode ultrasound-assisted extraction of phenolic compounds from olive leaves has been developed using a Box–Behnken design to optimize the effects of solvent composition and ultrasound parameters. The determination of single phenolic compounds was performed by HPLC–MS and the highest recovery in total compounds, oleuropein and hydroxytyrosol was achieved using EtOH/H2O (55:45, v/v), 8 min and 100% of amplitude. The optimal conditions were applied on leaves from seven olive cultivars grown under the same conditions and the results were compared with those found by using a conventional ultrasonic bath, obtaining no statistical differences. Moreover, antioxidant activity by FRAP, DPPH and ABTS in these olive leaf extracts was evaluated and they exhibited a significant correlation with oleuropein and total phenolic content. All cultivars of olive leaf extracts were found to be active against S. aureus and methicillin-resistant S. aureus with minimum bactericidal concentration (MBC) values) that ranged from 5.5 to 22.5 mg mL−1. No extracts showed antimicrobial activity against C. albicans. The percentages of mycelium reduction in B. cinerea ranged from 2.2 and 18.1%. Therefore, sonotrode could be considered as an efficient and fast extraction technique that could be easily scaled-up at industrial level, thus allowing for olive leaves to be revalorized.

Hazard of Staphylococcal Enterotoxins in Food and Promising Strategies for Natural Products against Virulence

Staphylococcal enterotoxins (SEs) secreted by Staphylococcus aureus frequently contaminate food and cause serious foodborne diseases but are ignored during food processing and even cold-chain storage. Notably, SEs are stable and resistant to harsh sterilization environments, which can induce more serious hazards to public health than the bacterium itself. Therefore, it is necessary to develop promising strategies to control SE contamination in food and improve food safety. Natural products not only have various pharmaceutical properties, such as antimicrobial and antitoxin activities, but they are also eco-friendly, safe, nutritive, and barely drug-resistant. Here, the hazards of SEs and the promising natural compounds with different inhibitory mechanisms are summarized and classified. The key points of future research and applications for natural products against bacterial toxin contamination in food are also prospected. Overall, this review may provide enlightening insights for screening effective natural compounds to prevent foodborne diseases caused by bacterial toxins.

Effect of paeonol against bacterial growth, biofilm formation and dispersal of Staphylococcus aureus and Listeria monocytogenes in vitro

Previous studies have demonstrated the antibacterial activity of paeonol against bacterial pathogens, but its anti-biofilm activities against Staphylococcus aureus and Listeria monocytogenes remain largely unexplored. Here, the antibacterial and anti-biofilm activities of paeonol against S. aureus and L. monocytogenes were examined using the crystal violet staining assay (CVSA), field emission scanning electron microscopy (FESEM), and confocal laser scanning microscopy (CLSM) analysis. Paeonol effectively inhibited the growth of S. aureus and L. monocytogenes with a minimum inhibitory concentration (MIC) of 500 and 125 μg ml^-1, respectively, and disrupted the integrity of cell membranes. Moreover, sub-MIC paeonol exhibited an inhibitory effect on the attachment of S. aureus and L. monocytogenes to the abiotic surface and biofilm formation. Further, paeonol effectively destroyed cell membranes within biofilms, and dispersed mature biofilms of both strains. The results indicate that paeonol might be a promising antibacterial and anti-biofilm agent for combating infections caused by S. aureus and L. monocytogenes.

Review on skeletal disorders caused by Staphylococcus spp. in poultry

Lameness or leg weakness is the main cause of poor poultry welfare and serious economic losses in meat-type poultry production worldwide. Disorders related to the legs are often associated with multifactorial aetiology which makes diagnosis and proper treatment difficult. Among the infectious agents, bacteria of genus Staphylococcus are one of the most common causes of bone infections in poultry and are some of the oldest bacterial infections described in poultry. Staphylococci readily infect bones and joints and are associated with bacterial chondronecrosis with osteomyelitis (BCO), spondylitis, arthritis, tendinitis, tenosynovitis, osteomyelitis, turkey osteomyelitis complex (TOC), bumblefoot, dyschondroplasia with osteomyelitis and amyloid arthropathy. Overall, 61 staphylococcal species have been described so far, and 56% of them (34/61) have been isolated from clinical cases in poultry. Although Staphylococcus aureus is the principal cause of poultry staphylococcosis, other Staphylococcus species, such as S. agnetis, S. cohnii, S. epidermidis, S. hyicus, S. simulans, have also been isolated from skeletal lesions. Antimicrobial treatment of staphylococcosis is usually ineffective due to the location and type of lesion, as well as the possible occurrence of multidrug-resistant strains. Increasing demand for antibiotic-free farming has contributed to the use of alternatives to antibiotics. Other prevention methods, such as better management strategies, early feed restriction or use of slow growing broilers should be implemented to avoid rapid growth rate, which is associated with locomotor problems. This review aims to summarise and address current knowledge on skeletal disorders associated with Staphylococcus spp. infection in poultry.

Presence and characterization of methicillin-resistant Staphylococcus aureus co-carrying the multidrug resistance genes cfr and lsa(E) in retail food in China

Staphylococcus aureus is an important food-related pathogen associated with bacterial poisoning that is difficult to treat due to its multidrug resistance. The cfr and lsa(E) genes both cause multiple drug resistance and have been identified in numerous Staphylococcus species, respectively. In this study, we found that a methicillin-resistant S. aureus (MRSA) strain, 2868B2, which was isolated from a sample of frozen dumplings in Hangzhou in 2015, co-carried these two different multidrug resistance genes. Further analysis showed that this strain was resistant to more than 18 antibiotics and expressed high-level resistance to florfenicol, chloramphenicol, clindamycin, tiamulin, erythromycin, ampicillin, cefepime, ceftazidime, kanamycin, streptomycin, tetracycline, trimethoprim-sulfamethoxazole and linezolid (MIC = 8 μg/mL). Whole genome sequencing was performed to characterize the genetic environment of these resistance genes and other genomic features. The cfr gene was located on the single plasmid p2868B2 (39,159 bp), which demonstrated considerable similarity to many plasmids previously identified in humans and animals. p2868B2 contained the insertion sequence (IS) element IS21-558, which allowed the insertion of cfr into Tn558 and played an important role in the mobility of cfr. Additionally, a novel multidrug resistance region (36.9 kb) harbouring lsa(E) along with nine additional antibiotic resistance genes (ARGs) (aadD, aadE, aacA-aphD, spc, lnu(B), lsa(E), tetL, ermC and blaZ) was identified. The multidrug resistance region harboured four copies of IS257 that were active and can mediate the formation of four circular structures containing ARGs and ISs. In addition, genes encoding various virulence factors and affecting multiple cell adhesion properties were identified in the genome of MRSA 2868B2. This study confirmed that the cfr and lsa(E) genes coexist in one MRSA strain and the presence of plasmid and IS257 in the multi-ARG cluster can promote both ARG transfer and dissemination. Furthermore, the presence of so many ARGs and virulence genes in food-related pathogens may seriously compromise the effectiveness of clinical therapy and threaten public health, its occurrence should pay public attention and the traceability of these genes in food-related samples needs further surveillance.

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.

Genetic Diversity of Staphylococcus aureus Strains from a Tertiary Care Hospital in Rawalpindi, Pakistan

Staphylococcus aureus is an important healthcare-associated bacterium that causes a multitude of infections in humans such as superficial skin and soft tissue infections, necrotizing pneumonia, foodborne illnesses and postsurgical infections. Treatment of S. aureus infections has become more complicated due to the emergence of Methicillin-Resistant Staphylococcus aureus (MRSA), some of which are multidrug resistant. The present study aimed to characterize S. aureus isolates from a tertiary care hospital in the Rawalpindi district of Pakistan. Staphylococci were isolated from 300 clinical samples collected from January 2018 to January 2019 and S. aureus isolates were tested for antimicrobial susceptibility and analyzed using Pulsed-Field Gel Electrophoresis (PFGE), Multi-Locus Sequence Typing (MLST), staphylococcal cassette chromosome mec (SCCmec) and spa typing. Approximately 25.3% (76/300) of the clinical samples were positive for S. aureus; of those, 88.2% (67/76) were mecA+ (MRSA). In addition to the β-lactam antibiotics, high levels of resistance were also found to the fluoroquinolones (ciprofloxacin, gatifloxacin and levofloxacin (73.7% each)). Of the 23 different spa types identified, the majority of isolates belonged to spa type t632 and t657 (9/66; 13.6% each spa type). ST772-t657 (Bengal Bay clone) was the most commonly identified clone in this study although other clones circulating around different regions of the world were also found indicating the diversity in MRSA isolates from this area of Pakistan. This study emphasizes the need to monitor MRSA in the clinical setting for improved infection control and treatment options.

Essential Oils from Fruit and Vegetables, Aromatic Herbs, and Spices: Composition, Antioxidant, and Antimicrobial Activities

In the field of food preservation, encapsulated Essential Oils (EOs) could be the best non-toxic and eco-friendly tool for food preservative applications substituting the chemicals ones that have several disadvantages for the environment and health. Thirteen commercial EOs from plants, fruits, and vegetables were characterized by GC-MS. The antioxidant activity was measured by DPPH and ABTS techniques. Antimicrobial activity was assessed by agar well-diffusion method and the Minimum Inhibitory Concentration (MIC) by agar dilution method against six bacteria, Candida albicans, and Botrytis cinerea. All the EOs tested have demonstrated antioxidant activity in the range of IC50 0.01-105.32 mg/mL. Between them, cinnamon EOs were the best, followed by oregano and thyme EOs. Fennel EO showed the lowest radical scavenging. MIC values ranged from 0.14 to 9 mg/mL. C. cassia, thyme, and oregano EOs were the most effective against the bacterial species tested, and the yeast C. albicans. On the contrary, citric fruit EOs showed low or no inhibition against most bacterial strains. The percentages of inhibition of mycelia growth of B. cinerea ranged from 3.4 to 98.5%. Thyme, oregano, mint, and fennel EOs showed the highest inhibition.

Phage Treatment Trial to Eradicate LA-MRSA from Healthy Carrier Pigs

The increase of livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) causes a threat to human health. LA-MRSA can be transmitted from animals to animal caretakers, which may further spread MRSA to communities and health care facilities. The objective of this work was to study the efficacy of phage treatment in the eradication of LA-MRSA from healthy carrier pigs. A total of 19 MRSA -positive weanling pigs were assigned to a test (n = 10) and a control group (n = 9). A phage cocktail containing three Staphylococcus phages, or a control buffer was administered to the nares and skin of the pigs three times every two days, after which the phage and MRSA levels in nasal and skin swab samples were monitored for a three-week period. The sensitivity of the strains isolated during the follow-up period to the phage cocktail and each phage individually was analyzed and the pig sera were tested for antibodies against the phages used in the cocktail. The phage treatment did not cause any side effects to the pigs. Phages were found in the skin and nasal samples on the days following the phage applications, but there was no reduction in the MRSA levels in the sampled animals. Phage-resistant strains or phage-specific antibodies were not detected during the experiment. The MRSA load in these healthy carrier animals was only 10-100 CFU/swab or nasal sample, which was likely below the replication threshold of phages. The effectiveness of phage treatment to eradicate MRSA from the pigs could thus not be (reliably) determined.

Aptasensors for Staphylococcus aureus Risk Assessment in Food

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

Simultaneous Hydrodistillation-Steam Distillation of Rosmarinus officinalis, Lavandula angustifolia and Citrus aurantium from Morocco, Major Terpenes: Impact on Biological Activities

Interest in the use of essential oils (EOs) in the biomedical and food industries have seen growing over the last decades due to their richness in bioactive compounds. The challenges in developing an EO extraction process that assure an efficient levels of monoterpenes with impact on biological activities have driven the present study, in which the EO extraction process of rosemary, lavender and citrus was performed by simultaneous hydrodistillation-steam distillation, and the influence of EO composition on biological activities, namely antioxidant, anti-inflammatory, antidiabetic, anti-acetylcholinesterase, anti-tyrosinase, antibacterial, and antibiofilm activity, were evaluated. The EO yields of combinations were generally higher than the individual plants (R. officinalis (Ro), L. angustifolia (La), and C. aurantium (Ca)) extracted by the conventional hydrodistillation. The EOs obtained by this process generally had a better capacity for scavenging the free radicals, inhibiting α-glucosidase, and acetylcholinesterase activities than the individual EOs. The combination of EOs did not improve the ability for scavenging peroxide hydrogen or the capacity for inhibiting lipoxygenase activity. The antioxidant activity or the enzyme inhibition activity could not only be attributed to their major compounds because they presented lower activities than the EOs. The chemical composition of the combination Ro:La:Ca, at the ratio 1/6:1/6:2/3, was enriched in 1,8-cineole, linalool, and linalyl acetate and resulted in lower MIC values for all tested strains in comparison with the ratio 1/6:2/3:1/6 that was deprived on those components. The biofilm formation of Gram positive and Gram negative bacteria was impaired by the combination Ro:La:Ca at a sub-inhibitory concentration.

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.