Detection of Enterotoxin Genes and Methicillin-Resistance in Staphylococcus aureus Isolated from Water Buffalo Milk and Dairy Products

Aptamer-modified paper-based analytical devices for the detection of food hazards: Emerging applications and future perspective

Food analysis plays a critical role in assessing human health risks and monitoring food quality and safety. Currently, there is a pressing need for a reliable, portable, and quick recognition element for point-of-care testing (POCT) to better serve the demands of on-site food analysis. Aptamer-modified paper-based analytical devices (Apt-PADs) have excellent characteristics of high portability, high sensitivity, high specificity, and on-site detection, which have been widely used and concerned in the field of food safety. The article reviews the basic components and working principles of Apt-PADs, and introduces their representative applications detecting food hazards. Finally, the advantages, challenges, and future directions of Apt-PADs-based sensing performance are discussed, to provide new directions and insights for researchers to select appropriate Apt-PADs according to specific applications.

Characterization and technological functions of different lactic acid bacteria from traditionally produced Kırklareli white brined cheese during the ripening period

In the present study, the evolution of the physicochemical and microbiological characteristics of lactic acid bacteria (LAB) in traditional Kırklareli white brined cheese collected from 14 different cheese manufacturing facilities were investigated on different days of the 90-day ripening period. The obtained LAB within the species Lactococcus (Lc.) lactis, Latilactobacillus (Lt.) curvatus, Lactobacillus (Lb.) casei and Lb. plantarum, Enterococcus (E.) durans, E. faecium, E. faecalis, Streptococcus macedonicus, and Weissella paramesenteroides were characterized in terms of their influence on technological properties and their potential as starter cultures for traditional white brined cheese production. The results of the microbiological and physicochemical investigations showed that a few selected isolates of Lc. lactis, Lb. casei, and Lb. plantarum had certain functions as starter germs. Moderate acidification capacity, antibacterial activity and proteolytic activity, which are characteristic of their use as starter lactic acid bacteria, were found. Importantly, antibiotic resistance among selected Lc. lactis, Lb. casei, and Lb. plantarum isolates was extremely low, whereas some of these isolates demonstrated antibacterial activity against major foodborne pathogenic bacteria. Based on the results obtained in this study, selected Lc. and Lb. isolates can also be considered as starter culture in traditional cheese production.

Antimicrobial-resistant foodborne pathogens in the Middle East: a systematic review

Foodborne pathogens are known as significant public health hazards worldwide, particularly in the Middle East region. Antimicrobial resistance (AMR) among foodborne pathogens becomes one of the top challenges for the environment, public health, and food safety sectors. However, less is known about antimicrobial-resistant foodborne pathogens in the Middle East region. Possibly because of the lack of surveillance, documentation, and reporting. This review focuses on the current status of antimicrobial resistance profiling among foodborne pathogens in the Middle East. Therefore, PubMed and other relevant databases were searched following PRISMA guidelines. Subject heading and texts were searched for "antimicrobial resistances," "foodborne," and "Middle East" to identify observational studies on AMR foodborne pathogens published during the last 10 years (2011 to 2020). Article retrieval and screening were done using a structured search string and strict inclusion/exclusion criteria. Median and interquartile ranges of percent resistance were calculated for each antibiotic-bacterium combination. A total of 249 articles were included in the final analysis from ten countries, where only five countries had more than 85% of the included articles. The most commonly reported pathogens were Escherichia coli, Salmonella spp. Staphylococcus aureus, and Listeria spp. An apparent rise in drug resistance among foodborne pathogens was recorded particularly against amoxicillin-clavulanic acid, ampicillin, nalidixic acid, streptomycin, and tetracycline that are commonly prescribed in most countries in the Middle East. Besides, there is a lack of standardization and quality control for microbiological identification and susceptibility testing methods in many of the Middle East countries.

Integrating multiple hybridization chain reactions on gold nanoparticle and alkaline phosphatase-mediated in situ growth of gold nanobipyramids: An ultrasensitive and high color resolution colorimetric method to detect the mecA gene of Staphylococcus aureus

Colorimetry has been considered as a potential instrument-free platform for point-of-care genomic detection. However, it is limited by the poor sensitivity and low color resolution. Herein, we report a high-resolution colorimetric biosensor based on multiple hybridization chain reactions (HCRs) on gold nanoparticle (AuNP) and alkaline phosphatase (ALP)-mediated in situ growth of gold nanobipyramids (AuNBPs) for ultrasensitive detection of the Staphylococcus aureus (S. aureus) mecA gene. In our design, target DNA is hybridized with capture hairpin DNA on magnetic beads and then amplified by multiple HCRs on AuNP. Since biotin-labeled hairpin-structured nucleic acids are utilized to conduct HCRs, together with the large specific surface area of AuNP, the biotin- and streptavidin- based reaction results in a large amount of ALP on AuNP. With the aid of NADPH, ALP-mediated in situ growth of AuNBPs is observed, and a series of rainbow-like colors are associated with different target DNA concentrations. Through the multiple-amplification strategy produced by AuNP, HCRs, and enzymatic reactions, the target DNA as low as 2.71 pM can be detected with high specificity. Moreover, this method has been successfully applied to detect the mecA gene extracted from S. aureus. Therefore, the proposed method holds great potential in clinical diagnosis.

Detection of Antimicrobial Resistance of Bacteria Staphylococcus chromogenes Isolated from Sheep's Milk and Cheese

Antimicrobial and multidrug resistance is detected in nonaureus staphylococci, including Staphylococcus chromogenes, which commonly causes intramammary infections. Recent clinical studies point to the presence of methicillin-resistant S. chromogenes. Therefore, this study aims to determine the prevalence of this species in samples of sheep‘s milk and cheeses made from them. Isolates were identified by polymerase chain reaction and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI–TOF). A total of 208 staphylococcal isolates were identified. Of these, 18% were identified as S. chromogenes. The antimicrobial resistance of the identified isolates was determined using the agar dilution method against penicillin, ceftaroline, teicoplanin, gentamicin, erythromycin, tetracycline, and ofloxacin. The highest resistance was found to penicillin (95%), tetracycline (86%), and oxacillin (81%). The highest sensitivity was confirmed for gentamicin (55%). The study also confirmed the presence of methicillin resistant staphylococcal isolates (30%) based on the phenotypic manifestation of antimicrobial resistance and detection of the presence of the mecA gene. The study shows that the tested isolates (62%) were multidrug resistant. Resistance to two antibiotics was most often found (39%).

Occurrence of Methicillin-Resistant Staphylococcus spp. on Brazilian Dairy Farms that Produce Unpasteurized Cheese

Methicillin-resistant Staphylococcus spp. (MRS) have been identified in several foods, including dairy products. Studies are needed about their occurrence and genetic diversity in the dairy production chain in order to gain a better understanding of their epidemiology and control. This study therefore focuses on isolating and characterizing MRS strains detected in milk used in the production of Brazilian artisanal unpasteurized cheeses. To this end, samples were collected from bovine feces, the hands of milkmen, milking buckets, sieves, unpasteurized milk, whey, water, artisanal unpasteurized cheeses, cheese processing surfaces, cheese handlers, cheese trays, cheese molds, and skimmers at five dairy farms located in the state of São Paulo, Brazil. Colonies suggestive of Staphylococcus spp. were subjected to multiplex PCR to confirm the presence of Staphylococcus aureus and to detect the mecA gene. Sixteen isolates containing mecA gene were detected in samples from unpasteurized cheese and from cheese handlers. None of these isolates were positive to enterotoxin genes. These 16 isolates were subjected to antimicrobial susceptibility tests, which revealed they were resistant to oxacillin, penicillin, and cefepime. Using gene sequencing, the MRS isolates were identified as S. haemolyticus, S. hominis, and S. epidermidis. Furthermore, isolates from cheese handlers’ hands and artisanal unpasteurized cheese presented high genetic similarity by random amplified polymorphic DNA (RAPD-PCR) analysis, which indicates cross contamination during cheese production. Thus, we found that people directly involved in milking and cheese processing activities at small dairy farms are a potential source of contamination of MRS strains in unpasteurized milk and cheese, representing a risk to public health.

Occurrence and characteristics of methicillin-resistant Staphylococcus aureus (MRSA) in buffalo bulk tank milk and the farm workers in Italy

The aim of the present study was to assess the occurrence of MRSA in buffalo dairy farms and in buffalo tank milk from Italy, and to provide information about the antimicrobial resistance profile and molecular characteristics of the isolates. We collected 75 bulk tank milk (BTM) samples from 75 farms and 24 nasal swabs from 24 farm operators. Three (4%) of the 75 BTM samples and 1 (4%) of the 24 human nasal swabs tested positive for MRSA. The milk isolates belonged to the genotypes ST1/t127/Va and ST72/t3092/V, while the human isolate was characterized as ST1/t127/IVa. All isolates were multidrug resistant but vancomycin susceptible; they carried the icaA gene but tested negative for the pvl and ses genes. ST72 is a CA-MRSA commonly found in South Korea, and this is the first report of its detection in Europe. Although we found a low prevalence of MRSA in the farms we surveyed, this study clearly demonstrates, for the first time in Europe, that MRSA can be found in dairy buffalo farms and in raw buffalo milk. Therefore, the risk of human colonization/infection with MRSA linked to the handling of raw milk or consumption of contaminated dairy products should not be ruled out.

Short communication: Detection of antibiotic resistance, mecA, and virulence genes in coagulase-negative Staphylococcus spp. from buffalo milk and the milking environment

The aim of this study was to determinate whether coagulase-negative staphylococci (CNS) from buffalo milk or the milking environment possess virulence factors that are associated with intramammary infections or antimicrobial resistance. Milk samples (n = 320) from 80 lactating buffalo were evaluated for clinical and subclinical mastitis by physical examination, the strip cup test, California Mastitis Test (CMT), and somatic cell count (SCC) over a 4-mo period. In addition, swabs were obtained from the hands of consenting milkers (16), liners (64), and from the mouths (15) and nostrils (15) of buffalo calves. No clinical cases of mastitis were observed; however, CMT together with SCC results indicated that 8 animals had subclinical mastitis. Eighty-four CNS isolates were identified by MALDI-TOF MS and cydB real-time PCR (qPCR) and then evaluated by qPCR for presence of the eta, etb, sea, sec, cna, seb, sei, seq, sem, seg, see, and tst toxin genes, adhesion- and biofilm-associated genes (eno, ebps, fib, fnbA, coa), and the methicillin resistance gene (mecA). Resistance to antibiotics commonly used for mastitis treatment in Brazil was determined using the Kirby-Bauer test. Two strains were positive for the see and eta toxin genes; and mecA (1), eno (27), ebps (10), fnbA (10), and coa (5) genes were also detected. A notable number of isolates were resistant to erythromycin (30), penicillin (26), and cotrimoxazole (18); importantly, 10 vancomycin-resistant isolates were also detected. A smaller number of isolates were resistant to rifampicin (8), oxacillin (7), clindamycin (5), cefepime (4), tetracycline (3), ciprofloxacin (2), and chloramphenicol (1), and none were resistant to gentamicin or ciprofloxacin. Isolates with resistance to 2 (13 isolates), 3 (3), 4 (3), 5 (1), and 6 (1) antibiotics were detected. Taken together, our findings suggest that CNS isolates may not be a significant cause of clinical or even subclinical mastitis in buffaloes, but they may be a reservoir of virulence and antibiotic resistance genes.

Inhibitory effects of Inula britannica extract fermented by Lactobacillus plantarum KCCM 11613P on coagulase activity and growth of Staphylococcus aureus including methicillin-resistant strains

The aim of this study was to evaluate the antimicrobial efficacy of fermented Inula britannica extract (FIBE) against Staphylococcus aureus strains including methicillin-resistant S. aureus (MRSA). I. britannica extract was fermented by Lactobacillus plantarum KCCM 11613P, and the pathogenicity of S. aureus strains was determined via assessment of coagulase, DNase, and hemolytic activities. Epicatechin concentration increased from 4.38 to 6.05 μg/mg during fermentation (p < 0.01). FIBE treatment inhibited coagulase release from S. aureus to levels below the inhibitory concentration. FIBE promoted the release of intracellular nucleic acids and N-phenyl-1-naphthylamine absorption. In three S. aureus strains, damaged cells exhibited 21.58, 16.79, and 17.65% decreases in membrane potential induced by cell membrane depolarization, respectively (p < 0.05). Upon FIBE treatment in culture, the minimum inhibitory concentration of FIBE exerted a bacteriostatic effect. In conclusion, FIBE possesses antimicrobial properties, including inhibition of virulence factors, damage to cell membranes, and inhibition of bacterial growth. PRACTICAL APPLICATIONS: Methicillin-resistant Staphylococcus aureus (MRSA) is a serious concern in hospitals because of its known antibiotic resistance. Vancomycin and tigecycline are used for treating MRSA, but the appearance of vancomycin-intermediate and multidrug-resistant strains of these bacteria has created a demand for new antimicrobial agents. This study demonstrates the effective application of Inula britannica and fermentation technology for developing natural antimicrobial agents against methicillin-resistant Staphylococcus aureus.

Panton-Valentine leukocidin (PVL) positive methicillin resistant Staphylococcus aureus (MRSA) in raw milk in Punjab

The emergence of methicillin resistant Staphylococcus aureus (MRSA) as a foodborne pathogen has posed a serious public health issue. Milk is extensively consumed food worldwide. The aim of this study was to estimate the presence of MRSA in raw milk in Punjab, by culture and polymerase chain reaction (PCR) techniques. Raw milk samples (291) were collected from all over Punjab. These 291 samples comprised 204 and 87 cow and buffalomilk samples respectively. The S. aureus was isolated on Baird Parker agar and typical colonies were subjected to biochemical tests and PCR for genus (16S rDNA) and species (nuc) specific detection. All the S. aureus isolates were further subjected to susceptibility testing to oxacillin and detection of mecA gene for methicillin resistance. Out of 291 samples, 42 (14.43%) showed contamination of S. aureus. Prevalence of S. aureus contamination was higher in cow milk (15.68%) than buffalo milk (11.49%). Only, three (1.03%) samples (one from buffalo and two from cow) were positive for MRSA. On SCC mec typing, all the MRSA positive isolates belonged to SCC mec type V, which is characteristic of Community Associated-MRSA (CA-MRSA). One isolate was also positive for pvl gene. PFGE showed that all the four isolates were closely related to each other. The results show that MRSA arepresent in food of animal origin and has potential to spread through it.