Prevalence, antimicrobial susceptibility, and enterotoxin gene detection of Staphylococcus aureus isolates in ready-to-eat foods in Shaanxi, People's Republic of China

Characterisation of a colourimetric biosensor SapYZUM13@Mn3O4-NH2 reveals the mechanisms underlying its rapid and sensitive detection of viable Staphylococcus aureus in food

In this study, a colourimetric biosensor based on bacteriophage SapYZUM13 and an aminated Mn3O4 (Mn3O4-NH2) nanozyme was constructed and evaluated for its ability to detect Staphylococcus aureus in food. The biosensor had a detection time of 20 min, with a detection limit of 2 × 101 CFU/mL and recovery rate of 92.42-106.96%, indicating its high reliability and accuracy in detecting the food pathogen. Mechanistically, SapYZUM13@Mn3O4-NH2 exhibited oxidase-mimicking capability, producing O2•- free radicals which oxidise 3,3',5,5'-tetramethylbenzidine (TMB) to yield blue-coloured oxTMB. In the presence of S. aureus, the oxidase activity decreased remarkably owing to shielding of the nanozyme active sites. Moreover, SapYZUM13@Mn3O4-NH2 could detect viable S. aureus from various sources, likely because of the special receptor-binding proteins of SapYZUM13 adsorbing to the wall teichoic acids on the S. aureus cell surface. Thus, SapYZUM13@Mn3O4-NH2 has broad application prospects for the detection of viable S. aureus in various foods.

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.

Prevalence, Antibiotic Resistance, and Molecular Typing of Staphylococcus aureus Isolated from Ready-to-Eat Foods in Guangdong, South China

The increasing global popularity of ready-to-eat (RTE) foods for their convenience simultaneously brings along a risk, as these products can be contaminated with various microorganisms, including potentially harmful pathogens. We aimed to investigate the food contamination of Staphylococcus aureus (S. aureus) in RTE foods in Guangdong, South China. All S. aureus isolates were subjected to characterization through antimicrobial susceptibility tests, multilocus sequence typing (MLST), and PCR analysis for detecting mec and blaZ genes. A total of 824 RTE food samples were collected from 2017 to 2022, of which 73 (8.9%) were found to be contaminated with S. aureus. Contamination levels were mostly in the range of 0.3-1.0 most probable number (MPN)/g, with 10 samples exceeding 110 MPN/g. Of the 73 S. aureus isolates, 10 were identified as methicillin-resistant S. aureus (MRSA). In MRSA, resistance was most frequently observed to penicillin (100%, 10/10), followed by erythromycin (80.0%, 8/10) and tetracycline (70%, 7/10). And in methicillin-sensitive S. aureus (MSSA), resistance was most frequently observed to penicillin (98.4%, 62/63), followed by tetracycline (30.2%, 19/63) and erythromycin (23.8%, 15/63). Overall, 98.6% (72/73) of the isolates demonstrated resistance to at least one antimicrobial agent, whereas 31.5% (23/73) were resistant to three or more antimicrobials. Fifty-seven S. aureus isolates harbored the penicillin-resistant gene blaZ, and 10 isolates carried the mec gene. In addition, 30.1% of the isolates harbored genes for classical staphylococcal enterotoxins (SEs), with seb being the most frequently detected SE gene. MLST revealed that the 73 isolates belonged to 14 different sequence types (STs), the most prevalent of which was ST7. In MRSA, the most common prevalent clone is ST6, and in MSSA, ST7 was the most common isolates. The prevalent multidrug resistance indicates that the resistance situation of foodborne S. aureus in Guangdong is severe, posing a potential threat to consumer safety and health.

Ready-to-Eat Foods: A Potential Vehicle for the Spread of Coagulase-Positive Staphylococci and Antimicrobial-Resistant Staphylococcus aureus in Buea Municipality, South West Cameroon

The consumption of ready-to-eat (RTE) foods contaminated with coagulase-positive staphylococci (CoPS) and especially Staphylococcus aureus puts consumers at a potential risk of food-borne disease or colonization and subsequent infection. This cross-sectional study determined the levels of CoPS and the presence of S. aureus in RTE foods sold in Buea municipality. A total of 420 RTE food samples, comprising 70 each of cake, bread, fruit salad, meat hot-pot, suya, and boiled rice were randomly purchased from February to August 2020. The CoPS counts were determined by culturing on Baird-Parker agar, and S. aureus was identified by amplification of the nuc gene using the polymerase chain reaction. All S. aureus isolates were screened for the presence of classical staphylococcal enterotoxin genes. To determine antimicrobial resistance profiles, each isolate was tested against 11 antimicrobials. Oxacillin-resistant S. aureus strains were analyzed for the presence of the mecA gene. Overall, 161 (38.3%) samples had detectable levels of CoPS ranging from 2.0 to 5.81 log10 CFU/g. Based on CoPS levels, 37 (8.81%) of the 420 RTE food samples-only fruit salad and meat hot-pot, had unsatisfactory microbiological quality. A total of 72 S. aureus isolates, comprising 52.78% from fruit salad, 16.67% from meat hot-pot, 12.5% from boiled rice, 9.72% from suya, 5.56% from bread, and 4.17% from cake, were recovered. None of the S. aureus isolates possessed any of the classical enterotoxin genes. All the isolates were susceptible to vancomycin and ofloxacin, while 68 (94.44%) and 66 (91.67%) were susceptible to oxacillin and ciprofloxacin, respectively. Resistance to penicillin (93.06%) was highest, followed by amoxicillin (91.67%) and erythromycin (79.17%). Four isolates were identified as methicillin-resistant S. aureus, all of which carried the mecA gene. A total of 24 antibiotypes were identified. Our findings showed that RTE foods sold in the Buea municipality are likely vehicles for the transmission of CoPS and antimicrobial-resistant S. aureus.

Prevalence of Antimicrobial-resistant Bacteria in HACCP Facilities

Foodborne pathogens, such as Staphylococcus aureus and Salmonella spp., develop antimicrobial resistance (AMR) over time, resulting in compromised food safety. Therefore, this study aimed to determine the prevalence, compliance against Malaysia's veterinary standing procedure directive (APTVM 16 (c): 1/2011): Appendix 713), and antimicrobial resistance (AMR) profiles of S. aureus and Salmonella spp., in raw poultry meat, poultry meat products, and poultry-based ready-to-eat (RTE) foods. Here, 699 raw poultry meat and meat products samples were obtained from selected hazard analysis critical control points (HACCP)-certified poultry meat-processing plants. Additionally, 377 samples of poultry-based RTE meals were collected from dine-in establishments and hospital catering facilities in Klang Valley, Malaysia. Salmonella spp. and S. aureus were present in 2.1% and 2.8% of the analyzed samples, respectively. Salmonella spp isolated from raw poultry meat and its products displayed resistance to ampicillin (100%), chloramphenicol (87.0%), cefuroxime (60.9%), cefazolin (56.5%), and kanamycin (52.2%). Similarly, S. aureus isolated from raw poultry meat, its products, and poultry-based RTE foods exhibited resistance against tetracycline, chloramphenicol, penicillin, ciprofloxacin, trimethoprim, kanamycin, and cefoxitin. The multi-antibiotic resistance (MAR) demonstrated by these foodborne pathogens makes their prevalence disconcerting. This highlights the need for more stringent monitoring and enduring sanitary and hygiene practices in HACCP establishments to prevent foodborne infections and potential transmission of AMR bacteria.

Genomic analysis, antibiotic resistance, and virulence of Staphylococcus aureus from food and food outbreaks: A potential public concern

Transmission and outbreaks of Staphylococcus aureus among retail food highlights the need to comprehensive analysis the molecular characteristic of Staphylococcus aureus in foods. However, the information about Staphylococcus aureus in north China is limited. In this study, 97 and 28 S. aureus strains were isolated for analysis from 4262 samples of retail food and 61 samples food outbreaks with prevalence rate 2.28 % and 45.9 %, respectively in Jilin, China from 2014 to 2018. This study aimed to investigate the prevalence of S. aureus isolates and characterize by antimicrobial resistance testing, virulence profiles, spa typing, and multilocus sequence typing (MLST) analysis. 60 % (75/125) of the isolates contained at least enterotoxin genes including classic and new SEs genes as following: sea (40/125,32 %), see (36/125,28.8 %), sec (29/125,23.2 %), sell (29/125,23.2 %), seb (25/125,20 %), seh (22/125,17.6 %), sed (6/125,4.8 %), selq (6/125,4.8 %), and selk (6/125,4.8 %). In antimicrobial susceptibility tests, 59.2 % of the isolates (74/125) were considered as multi-drug-resistant isolates and four MRSA strains were all found with high multi-drug-resistance. Phenotype resistance to penicillin (94.4 %), erythromycin (84.2 %), clindamycin (63.9 %), and tetracycline (47.2 %) was observed which was corresponding with genotype resistance. The strains were classified to twenty-two sequence types (STs), fourteen clonal complexes (CCs), and forty-seven spa types. The predominant ST and spa types were ST1(22/125,17.6 %), ST25(20/125,16.00 %), ST398 (14/125,11.2 %) and t127 (20/125,16 %), t078 (14/125,11.2 %), t803 (7/125,5.6 %). The wgSNP analysis of these isolates in food represents showed close relatedness with food outbreaks which pose a potential health risk for consumers and warrants further attention.

Staphylococcus aureus in poultry, with special emphasis on methicillin-resistant strain infection: A comprehensive review from one health perspective

Staphylococcus aureus is a Gram-positive coccus normally present on the skin and internal organs of animals, birds, and humans. Under certain conditions, S. aureus could produce septicemia and affection of the skin, joints, and heart, as well as sepsis and death. The pathogenicity of S. aureus is associated with the presence of some virulent surface proteins and the production of some virulent toxins and enzymes. This pathogen is considered one of the most important and worldwide foodborne causes as it is incriminated in most cases of food poisoning. The hazardous use of antibiotics in the veterinary field leads to the development of multidrug-resistant S. aureus strains that can be transmitted to humans. The incidence of methicillin-resistant S. aureus (MRSA) strains has increased globally. These resistant strains have been detected in live animals, poultry, and humans. In addition, retail animal products, especially those of avian origin, are considered the main source of MRSA strains that can be easily transmitted to humans. MRSA infection is regarded as nosocomial or occupational. Humans get infected with MRSA strains through improper handling or preparation of contaminated animals or poultry carcasses or improper cooking with contaminated meat. Live birds also can transmit MRSA to close-contact workers in poultry farms. Transmission of MRSA infection in hospitals is from an infected individual to a healthy one. Prevention and control of MRSA are based on the application of hygienic measures in farms as well as proper processing, handling, and cooking of retail poultry products. The cooperation between veterinary and human practitioners is a must to avoid the possibility of zoonotic transmission. Accordingly, this review focused on the sources and transmission of MRSA infection, virulence and resistance factors, incidence and prevalence in poultry and different products, antibiotic resistance, and prevention and control strategies.

Multisite survey of bacterial contamination in ready-to-eat meat products throughout the cooking and selling processes in urban supermarket, Nanjing, China

OBJECTIVE

Ready-to-eat (RTE) meat is a kind of popular instant food easily contaminated by microbes, which is one of the causes of foodborne diseases. This study analyzes the possible sources of RTE food bacterial contamination during processing and subsequent selling.

METHOD

Samples of eight kinds of RTE meat were collected from four supermarkets in Nanjing, China. The knives, chopping boards, trays(containers of food), clamps, air, water, and hands of the sales staff were sampled, and the enumeration of aerobic plate count and total coliforms and pathogenic bacteria was performed.

RESULTS

The survey revealed that poor hygienic levels was the causes that RTE meat products were contaminated by bacteria at different levels. With regard to pathogen, the incidences of Salmonella spp. and Staphylococcus aureus were 4.2% and 2.1%, respectively. These results also revealed that the bacterial contamination of RTE food was caused by the air, as well as clamps, chopping boards, knives, trays, and hands of the operators. The total number of aerobic colonies were positively correlated with the amount of RTE food in one pot (r = .87728, p = .0217), and negatively correlated with the maximum temperature in the center of the meat (r = -.81633, p = .0475).

CONCLUSION

The high number of bacteria in RTE foods indicates potential food safety risks and the need to improve the health of supermarket sales staff. The most important thing is to determine how to raise hygiene awareness of employees through food safety education. Meanwhile, a comprehensive set of regulations on hand cleaning and disinfection should be developed to facilitate public health and reduce foodborne illness caused by the consumption of RTE food.

Antibiotic Resistance Patterns of Staphylococcus aureus Isolates from Retail Foods in Mainland China: A Meta-Analysis

Foodborne Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA), is increasingly threatening human health. Pooled prevalence rates of S. aureus contamination have been extensively studied in retail food products in mainland China, but data regarding antibiotic resistance rates of S. aureus remain scattered. This study was designed to collect researches published between 2007 and 2017 in mainland China and to evaluate the antibiotic resistance of S. aureus from retail foods using a meta-analytic approach. We systematically searched the China National Knowledge Infrastructure (CNKI) and Web of Science databases to identify peer-reviewed literature. A number of multilevel random-effects models were fitted to estimate mean occurrence rates of antibiotic-resistant S. aureus, and subgroup analyses were performed to compare antibiotic resistance rates of S. aureus throughout the years and among the methods to determine the antimicrobial susceptibility. Among the considered antibiotics, S. aureus showed the highest resistance rate to penicillin G (87%, 95% confidence interval [CI] 83-90%), followed by ampicillin (72%, 95% CI 62-81%) and erythromycin (41%, 95% CI 36-46%). MRSA showed the highest resistance rate to ampicillin (98%, 95% CI 89-100%), followed by oxacillin (97%, 95% CI 80-100%) and penicillin G (96%, 95% CI 89-99%). Multidrug resistance (MDR) of S. aureus was most frequently observed to three antibiotics (17%, 95% CI 12-22%), and MRSA showed the highest resistance rate to four antibiotics (24%, 95% CI 5-67%). Subgroup analyses results proved that sources of heterogeneity among studies were neither publication year nor detection method. In conclusion, the meta-analysis showed that β-lactam antibiotics resistance of S. aureus and MRSA strains isolated from retail foods remained the most serious, and MDR of S. aureus and MRSA were also observed. Therefore, it is important to monitor the antibiotic resistance of S. aureus and MRSA in food chain, and food safety measures should be taken to reduce the transmission of this bacterium from foods to human beings.

The Prevalence, Antibiotic Resistance and Biofilm Formation of Staphylococcus aureus in Bulk Ready-To-Eat Foods

The prevalence of Staphylococcus aureus in 2160 bulk ready-to-eat foods from the Sichuan province of China during 2013-2016 was investigated. The antibiotic resistance and the associated genes, as well as biofilm formation capacity of the S. aureus isolates were measured. Furthermore, the relationship between the antibiotic resistance and the resistant genes was discussed. It was found that 54 S. aureus isolates were recovered, and their prevalence in meat products, dairy, fruit and vegetables, and desserts were 31 (2.6%), six (3.0%), nine (2.2%) and eight (2.3%), respectively. Most strains (52/54) were resistant to at least one of the antibiotics, and 21 isolates were identified as multidrug-resistant (MDR) S. aureus. Three isolates were found to be methicillin-resistant S. aureus. Penicillin, erythromycin, clindamycin, tetracycline and inducible clindamycin resistance were determined as the predominant antibiotics, and the isolates with the phenotypic resistance on these five antibiotics were all determined positive for the resistant gene associated. In total, 33 of 54 S. aureus isolates showed biofilm formation capacity, including two strong biofilm producers, one moderate and 30 weak ones. Two S. aureus isolates with strong biofilm formation abilities showed multi-drug resistance, and one moderate biofilm producer was resistant to two categories of antibiotics.

Staphylococcus aureus Isolated From Retail Meat and Meat Products in China: Incidence, Antibiotic Resistance and Genetic Diversity

This study was to estimate the prevalence and characteristics of Staphylococcus aureus from 1,850 retail meat and meat products in China during July 2011 to June 2016. The samples were collected covering most provincial capitals in China, including 604 raw meat, 601 quick-frozen meat, and 645 ready-to-eat meat. Using the qualitative and quantitative methods, all 39 cities had S. aureus-positive samples, and S. aureus was detected in 35.0% (647/1,850) of the samples. The levels of S. aureus in retail meat showed that the MPN value of the majority of the positive samples ranged from 0.3 to 100 MPN/g. Twenty-four antibiotics were used to test all 868 S. aureus isolates for antibiotic susceptibility. Only 11 isolates (1.26%) were susceptible to all antibiotics, whereas most isolates (821/868, 94.6%) showed resistance or intermediary resistance to more than three or more antibiotics. Of these strains, 104 (12.0%) were resistant to more than 10 antibiotics. However, the most frequent resistance was observed to ampicillin (85.4%), followed by penicillin (84.6%), erythromycin (52.7%), tetracycline (49.3%), kanamycin (45.3%), telithromycin (30.1%), clindamycin (29.6%), streptomycin (21.1%), norfloxacin (20.4%), gentamicin (19.4%), fusidic acid (18.4%), ciprofloxacin (16.9%), chloramphenicol (13.1%), amoxycillin/clavulanic acid (11.0%), and others (<10%). 7.4% of isolates (62/868) were confirmed as methicillin-resistance S. aureus (MRSA). By molecular typing analysis, there were 164 spa types and 111 STs were identified, including 15 novel spa types and 65 newly STs by multilocus sequence typing (MLST) and spa typing. Despite the wide genetic diversity observed among the 868 isolates, a great proportion of the population belonged to finite number of major clones: ST1-t127 (93/868, 10.7%) and ST7-t091 (92/868, 10.6%), ST5-t002 (42/868, 4.8%), ST398-t034 (40/868, 4.6%), ST188-t034 (38/868, 4.4%), ST59-t437 (30/868, 3.5%), ST6-t701 (29/868, 3.3%), and ST9-t899 (27/868, 3.1%) in China. This study reflects S. aureus was readily detected in Chinese retail meat and meat products but the level were not very excessive. In this study, the high antibiotic resistance is alarming and raising public health concern. In additions, most of molecular types of isolates have been linked to human infections around the world, indicating that these types of S. aureus in China have a theoretical pathogenic potential.

Occurrence of transferable antibiotic resistances in commercialized ready-to-eat mealworms (Tenebrio molitor L.)

The present study aimed to assess the occurrence of transferable determinants conferring resistance to tetracyclines, macrolide-lincosamide-streptogramin B, vancomycin, beta-lactams, and aminoglycosides in 40 samples of commercialized edible mealworms (Tenebrio molitor L.) purchased from European Union (EU) and non-EU producers. A high prevalence of tet(K) was observed in all of the samples assayed, with percentages of PCR-based positivity that ranged from 80% (samples from Thailand) to 100% (samples from the Netherlands, Belgium and France). For macrolides, erm(B) prevailed, being detected in 57.5% of the samples assayed, whereas erm(A) and erm(C) were detected with lower frequencies. Genes for resistance to vancomycin were only detected in samples produced in France and Belgium, with 90% and 10% of the samples being positive for vanA, respectively. Beta-lactamase genes were found with low occurrence, whereas the gene aac-aph, conferring high resistance to aminoglycosides, was found in 40% of the samples produced in the Netherlands and Belgium and 20% of the samples produced in Thailand. The results of Principal Coordinate Analysis and Principal Component Analysis depicted a clean separation of the samples collected from the four producers based on the distribution of the 12 AR determinants considered. Given the growing interest on the use of mealworms as a novel protein source, AR detection frequencies found in the present study suggest further investigation into the use of antibiotics during rearing of this insect species and more extensive studies focused on the factors that can affect the diffusion of transferable ARs in the production chain. Until such studies are completed, prudent use of antibiotics during rearing of edible insects is recommended.

Occurrence of antibiotic resistance genes in the fecal DNA of healthy omnivores, ovo-lacto vegetarians and vegans

SCOPE

The effects of long-term omnivore, ovo-lacto vegetarian and vegan diets on the occurrence of 12 antibiotic resistance (AR) genes in the human gut were studied.

METHODS AND RESULTS

The feces of 144 healthy volunteers recruited from Turin, Bari, Bologna, and Parma were screened for the occurrence of genes conferring resistance to tetracyclines, macrolide-lincosamide-streptogramin B, vancomycin, and β-lactams. Overall, erm(B), tet(W) and tet(M) were detected at the highest frequency. A low effect from the diet on the AR gene distribution emerged, with tet(K) and vanB occurring at a lower and higher frequency in vegans and omnivores, respectively. A correlation of the intake of eggs, milk from animal sources and cheese with an increased occurrence of tet(K) was observed, together with a higher incidence of vanB in consumers of eggs, poultry meat, fish and seafood. When the detection frequencies of AR genes in volunteers from Bari and the other sites were comparatively evaluated, a north-to-south gradient was observed, whereas no effect of sex or age was highlighted. Except for tet(K), a negligible three-factor interaction was seen.

CONCLUSION

A high impact of the geographical location on AR gene distribution was seen in the cohort of subjects analyzed, irrespective of their dietary habits.