Species Diversity and Pheno‐ and Genotypic Antibiotic Resistance Patterns of Staphylococci Isolated from Retail Ground Meats

The presence and species diversity of staphylococci in 250 ground beef and lamb meat samples obtained from Diyarbakir, Turkey were investigated. The presence of the 16S rRNA gene, mecA, nuc, pvl, and femA was analyzed by multiplex PCR. Pheno‐ and genotypic antibiotic resistance profiles of 208 staphylococci isolates were established. Of the ground beef and ground lamb samples, 86.4% and 62.4% were positive for staphylococci, respectively. Staphylococcus aureus, S. saprophyticus, S. hominis, S. lentus, S. pasteuri, S. warneri, S. intermedius, and S. vitulinus made up 40.8%, 28.8%, 11%, 3.8%, 3.8%, 2.4%, 2.4%, and 2.4% of isolates, respectively. Of the 85 S. aureus isolates, 40%, 47%, and 5.8% carried femA, mecA, and pvl, respectively, whereas the corresponding rates for the 118 coagulase‐negative staphylococci (CoNS) were 0%, 10.1%, and 0%, respectively. We determined from the 208 isolates, the highest antibiotic resistances were to tetracycline and oxytetracycline (85.5%), followed by penicillin (51.4%), novobiocin (45.6%), ampicillin (39.9%), and doxycycline (31.7%), using the Clinical and Laboratory Standards Inst. (CLSI) method. All isolates were sensitive to gentamycin, ofloxacin, and tobramycin, but 2.3% of the S. aureus isolates had resistance to vancomycin. The staphylococci isolates carried tet(K), blaZ, tet(L), tet(W), cat, tet(S), tet(M), ermB, ermA, and ermC antibiotic resistance genes at rates of 59%, 51.7%, 36.9%, 31.8%, 27.2%, 27.2%, 24.4%, 18.1%, 7.9%, and 3.9%, respectively.     

Characterization of Staphylococcus aureus strains isolated from raw milk utilized in small-scale artisan cheese production

Staphylococcus aureus is an important agent of bacterial mastitis in milking animals and of foodborne intoxication in humans. The purpose of this study was to examine the genetic and phenotypic diversity, enterotoxigenicity, and antimicrobial resistance of S. aureus strains isolated from raw milk used for the production of artisan cheese in Vermont. Cross-tabulations revealed that the 16 ribotypes identified among the 90 milk isolates examined were typically associated with a specific animal species and that more than half of these ribotypes were unique to individual farms. In general, specific EcoRI ribotypes were commonly associated with specific phenotypical characteristics, including staphylococcal enterotoxin production or the lack thereof. Limited antimicrobial resistance was observed among the isolates, with resistance to ampicillin (12.51%) or penicillin (17.04%) most common. Two isolates of the same ribotype obtained from the same farm were resistant to oxacillin with 2% NaCl. More than half (52.22%) of isolates produced toxin, and 31 of the 32 isolates solely produced staphylococcal enterotoxin type C. Although these data demonstrate that S. aureus strains found in raw milk intended for artisan cheese manufacture are capable of enterotoxin production, staphylococcal enterotoxin C is not typically linked to foodborne illness. Because S. aureus is a common contaminant of cheese, an understanding of the ecology of this pathogen and of the antimicrobial susceptibility and toxigenicity of various strains will ultimately contribute to the development of control practices needed to enhance the safety of artisan and farmstead cheese production.     

First report of methicillin‐resistant Staphylococcus aureus in tank cultured dusky kob (Argyrosomus japonicus), and evaluation of three phenotypic methods in the detection of MRSA

This study was conducted to ascertain the occurrence of methicillin‐resistant Staphylococcus aureus (MRSA) in marine finfish (Argyrosomus japonicus) harvested from the wild and two re‐circulatory aquaculture systems, and evaluating the reliability of three phenotypic methods in the detection of methicillin resistance. A total of 120 dusky kob fish were sampled for S. aureus detection using conventional methods and confirmed by polymerase chain reaction (PCR) targeting the nuc gene. Methicillin resistance was determined by molecular detection of the mecA gene. Using mecA as the defining standard, the specificities and sensitivities of cefoxitin disc diffusion, oxacillin screen agar, and growth of S. aureus on Brilliance MRSA II Agar were evaluated. A total of 321 presumptive S. aureus isolates were recovered by culture, out of which 202 (62.9%) were confirmed by PCR. Of these, 33 (16.3%) strains were mecA positive while 169 (83.7%) were mecA negative. The sensitivities and specificities of MRSA detection was 93.9 and 91.7%, 81.8 and 92.3%, and 87.9 and 94.1% for cefoxitin disc, oxacillin screen agar test, and Brilliance MRSA II agar, respectively. This is so far the first report of MRSA in dusky kob aquaculture in South Africa. In the absence of molecular techniques, cefoxitin disc diffusion test is recommended along with any other phenotypic method to improve MRSA detection from samples of veterinary origin.

Practical implications

Methicillin‐resistant Staphylococcus aureus currently presents one of the greatest challenges for medical research worldwide, as well as is one of the most important causes of bacteria gastroenteritis due to preformed toxins in foods. There is a dearth of knowledge on marine foods as carriers/sources of MRSA infection. There are also major discrepancies obtained with MRSA detection methods, making effective detection of this pathogen complicated. The results from this study show that healthy aquaculture fish are reservoirs of MRSA, thus it is necessary to regularly monitor marine foods. Cefoxitin disc diffusion test is recommended as the preferred method for detection of MRSA from fish/food samples where molecular methods are lacking.     

A survey of the occurrence and properties of methicillin‐resistant Staphylococcus aureus and methicillin‐resistant Staphylococcus intermedius in water buffalo milk and dairy products in Turkey

Antimicrobial resistance, β‐lactamase activity and mecA gene of Staphylococcus aureus and Staphylococcus intermedius isolated from raw water buffalo milk and dairy products in Turkey were determined. All strains showed resistance to at least one antibiotic but none was resistant to vancomycin. Of the 97 S. aureus and 35 S. intermedius strains, 9 (9.2%) and 2 (5.7%) were resistant to oxacillin and harboured mecA gene. β‐lactamase activity of 13.4% and 5.7% of S. aureus and S. intermedius strains was positive, respectively. Overall, 2.5% and 0.55% of the samples were contaminated with methicillin‐resistant S. aureus and S. intermedius, respectively.     

ANTIMICROBIAL RESISTANCE IN SALMONELLA ENTERITIDIS ISOLATED FROM FOODS INVOLVED IN HUMAN FOODBORNE OUTBREAKS THAT OCCURRED IN THE SOUTH OF BRAZIL, 1999–2000

Antimicrobial resistance was determined for 73 isolates of Salmonella enteritidis isolated from foods involved in human foodborne outbreaks that occurred in the South of Brazil, from 1999 to 2000. The isolates were individually tested against 10 antimicrobial agents using a disc diffusion method. Most isolates were susceptible to all drugs tested. No S. enteritidis isolates were resistant to sulfamethoxazole/trimethoprim or chloramphenicol. The predominant resistance observed was to streptomycin (S) (37%), gentamicin (GEN) (13.7%) and nalidixic acid (NAL) (13.7%), while intermediate resistance was observed most often for tetracycline (53.4%), neomycin (NEO) (30.1%) and GEN (15.1%). Resistance was verified in 40 isolates (54%), which were grouped in 15 different patterns. Multiple resistance was presented in 17 (23%) of the isolates, and one isolate exhibited resistance to four drugs (NEO, kanamycin, S and NAL), demonstrating the involvement of multiresistant S. enteritidis strains with foodborne outbreaks.     

The Use of Multiplex PCR to Determine the Prevalence of Enterotoxigenic Staphylococcus aureus Isolated from Raw Milk,Feta Cheese,and Hand Swabs

Staphylococcus aureus (S. aureus) can cause mastitis in cattle and, therefore, can be present in milk. This study was undertaken to determine the prevalence of coagulase positive S. aureus and its enterotoxin genes sea, seb, and sec in isolates recovered from raw milk, feta cheese, and human hand swabs of milk and cheese handlers in Beni‐Suef province, Egypt. A total of 100 samples of raw milk and 50 samples of pasteurized‐milk feta cheese were collected. In addition, 50 hand swabs from milk handlers and 25 hand swabs from cheese handlers were examined for the presence of coagulase positive S. aureus. The isolates were characterized by multiplex PCR for detection of sea, seb, and sec genes, and for resistance to 5 classes of commonly used antibiotics. Twelve (12/100), 12 (6/50), and 17% (13/75) of milk, cheese, and hand swab samples, respectively, were positive for coagulase positive S. aureus. One isolate was obtained from each positive sample (31 isolates), and none contained genes for SEA or SEC production. Twenty‐five percent, 33%, and 31%, respectively, of the isolates contained the genes for SEB, resulting in 3%, 4%, and 5% of samples being positive for toxin producing coagulase positive S. aureus, respectively. At least one isolate was resistant to each of the antibiotics tested. Despite the low potential for SEB production shown, preventative measures, such as maintenance of the cold‐chain and good hygienic practices should be implemented to further reduce the potential risk to public health from SEB, and to reduce the spread of antimicrobial resistance.     

Short communication: β-Lactam resistance and vancomycin heteroresistance in Staphylococcus spp. isolated from bovine subclinical mastitis

The use of antimicrobial agents has led to the emergence of resistant bacterial strains over a relatively short period. Furthermore, Staphylococcus spp. can produce β-lactamase, which explains the survival of these strains in a focus of infection despite the use of a β-lactam antibiotic. The aim of this study was to evaluate the resistance of Staphylococcus spp. isolated from bovine subclinical mastitis to oxacillin and vancomycin (by minimum inhibitory concentration) and to detect vancomycin heteroresistance by a screening method. We also evaluated β-lactamase production and resistance due to hyperproduction of this enzyme and investigated the mecA and mecC genes and performed staphylococcal cassette chromosome mec typing. For this purpose, 181 Staphylococcus spp. isolated from mastitis subclinical bovine were analyzed. Using the phenotypic method, 33 (18.2%) of Staphylococcus spp. were resistant to oxacillin. In contrast, all isolates were susceptible to vancomycin, and heteroresistance was detected by the screening method in 13 isolates. Production of β-lactamase was observed in 174 (96%) of the Staphylococcus spp. isolates. The mecA gene was detected in 8 isolates, all of them belonging to the species Staphylococcus epidermidis, and staphylococcal cassette chromosome mec typing revealed the presence of type I and type IV isolates.     

Antimicrobial‐Resistance Genetic Markers in Potentially Pathogenic Gram Positive Cocci Isolated from Brazilian Soft Cheese

Although most Brazilian dairy products meet high technological standards, there are quality issues regarding milk production, which may reduce the final product quality. Several microbial species may contaminate milk during manufacture and handling. If antimicrobial usage remains uncontrolled in dairy cattle, the horizontal transfer of antimicrobial resistance genes in foodstuffs may be of particular concern for both food producers and dairy industry. This study focused on the evaluation of putative Gram positive cocci in Minas cheese and of antimicrobial and biocide resistance genes among the isolated bacteria. Representative samples of 7 different industrially trademarked Minas cheeses (n = 35) were processed for selective culture and isolation of Gram positive cocci. All isolated bacteria were identified by DNA sequencing of the 16S rRNA gene. Antimicrobial resistance genes were screened by PCR. Overall, 208 strains were isolated and identified as follows: Enterococcus faecalis (47.6%), Macrococcus caseolyticus (18.3%), Enterococcus faecium (11.5%), Enterococcus caseliflavus (7.7%), Staphylococcus haemolyticus (7.2%), Staphylococcus aureus (4.3%), Staphylococcus epidermidis (2.9%), and Enterococcus hirae (0.5%). The genetic markers mecA (78.0%) and smr (71.4%) were the most prevalent, but others were also detected, such as blaZ (65.2%), msrA (60.9%), msrB (46.6%), linA (54.7%), and aacA‐aphD (47.6%). The occurrence of opportunist pathogenic bacteria harboring antimicrobial resistance markers in the cheese samples are of special concern, since these bacteria are not considered harmful contaminating agents according to the Brazilian sanitary regulations. However, they are potentially pathogenic bacteria and the cheese may be considered a reservoir for antimicrobial resistance genes available for horizontal transfer through the food chain, manufacturing personnel and consumers.     

Sensory and bio‐chemical preservation of ricotta cheese using natural products

The objective of this study was to evaluate the antimicrobial activity and to study their preserving effect on quality and sensory parameters on flavoured ricotta cheese of Argentinean oregano essential oils (EOs). Criollo essential oil was the most effective agent controlling foodborne bacteria, with MIC values of 1.90 E‐04 mg mL^?1 for S. aureus and Salmonella sp. Ricotta with Cordobes essential oil exhibited the lowest percentage of lactic acid at the end of the storage (0.246%). After 30 days of storage, ricotta flavoured with Cordobes and Criollo EOs had the lowest total count (5.63 × 10³ and 7.80 × 10³ cfu g^?1, respectively). The Pearson's correlation analyses (P ≤ 0.05) showed that sour flavour was negatively related to cheese and casein flavours (r = ?0.46 and ?0.52, respectively). The inclusion of oregano EOs into ricotta cheese improves quality parameters but affects its sensory attributes.     

Prevalence of Salmonella serotypes S. Enteritidis and S. Typhimurium in poultry and poultry products

Salmonella continues to be a major food safety and public health threat. In the present study, Salmonella enterica subsp. enterica serotypes Enteritidis (SE) and Typhimurium (ST) were isolated from poultry and characterized for virulence, antimicrobial susceptibility, and biofilm formation. Prevalence of Salmonella serotypes in poultry was 3.35%; predominant serotypes isolated were S. Enteritidis (68.1%) and S. Typhimurium (31.8%). Source-wise, Salmonella were isolated from retail market chicken meat (4.8%), live chicken at farm (2.5%), and table eggs (2.1%). Salmonella isolates produced invA gene of 284 bp (100%), spvR gene of 310 bp (77.27%), spvC gene of 571 bp (22.72%), and stn gene of 260 bp (100%) as virulence/ pathogenicity determinants. Salmonella isolates exhibited resistance to common antimicrobials; 72.7% isolates showed multiple resistance (≥3 antimicrobial class), highest resistance was observed for polymyxin-B (81.8%) followed by nalidixic acid (72.7%), colistin (59.1%), ampicillin/tetracyline (45.5%), ampicillin + sulbactam (40.9%), cefodroxil (18.2%), streptomycin (9.1%), and cefazidine/ceftriaxone-tazobactam (4.5%). Multiple antimicrobial resistance (MAR) index of poultry Salmonella isolates ranged from 0.11 to 0.35; wherein, 59.1% isolates showed MAR of >0.2. About 81.8% Salmonella isolates produced biofilm and were categorized as strong (13.6%), moderate (45.4%), and weak (22.7%) biofilm producers. Occurrence of antimicrobial resistant virulent Salmonella strains in poultry requires implementation of suitable strategies so as to protect the public health.     

Incidence and antibiotic resistance of Salmonella spp. on raw chicken carcasses

The current study was carried out to detect Salmonella spp. contamination on chicken carcasses and to determine the antibiotic susceptibility profiles and serotype distribution of the isolates. A total of 200 packaged fresh raw chicken samples sold at retail in different markets in central Anatolia were analysed between April 2005 and March 2006. Salmonella spp. was detected in 34% (68/200) of samples using cultural technique and were confirmed by PCR. Ten Salmonella serovars were identified; predominant ones included Typhimurium, Infantis and Heidelberg. All of the Salmonella spp. isolates tested, exhibited resistance to one or more antimicrobial agents used. Resistance to penicillin, oxacillin, clindamycin, vancomycin, erythromycin and ampicillin were evident 100%, 97%, 97%, 92.6%, 89.7% and 85.2%, respectively. Also resistance to tetracycline (67.6%), streptomycin (61.7%), neomycin (55.8%) and cephalothin (52.9%) was observed but a small percentage of the isolates demonstrated resistance to gentamicin (14.7%), chloramphenicol (10.2%), cefotaxime (2.9%) and amikacin (2.9%). As a result, high prevalence of Salmonella spp. and the relatively high resistance among the bacteria tested could pose public health and therapeutic problems in consumers as potential vehicle of resistant Salmonella foodborne infections. To avoid Salmonella contamination, hygienic rules of slaughter and poultry meat processing must be rigorously observed and antibiotic use must be controlled by governmental agencies to prevent increased resistance of antibiotics.     

Molecular and phenotypic characterization of Staphylococcus aureus strains isolated from carcass swabs and carcass drips of chickens slaughtered in the informal market in Gauteng Province,South Africa

The study was conducted to characterize Staphylococcus aureus strains from swabs and drips of dressed chicken carcasses sold at outlets in six townships in the informal market in Gauteng province, South Africa, using molecular and phenotypic methods. Seven genes (6 toxins and 1 antimicrobial resistance) comprising staphylococcal enterotoxin A (SEA), B (SEB), C (SEC), D (SED), exfoliative toxin A, toxic shock syndrome toxin, and MecA encoding methicillin resistance were assayed using polymerase chain reaction. The resistance of the S. aureus strains to 18 antimicrobial agents was determined using the disk diffusion method. The frequency of detection of the six toxin genes was sea (52.2%), followed by seb (10.9%), sec (6.5%), sed (2.2%), eta (93.5%), and tst (19.6%). The mecA gene was detected in 4.3% of the isolates. The predominant profiles of toxin genes detected were sea-eta (37.0%). All 63 isolates of S. aureus were resistant to one or more antimicrobial agents. The frequency of resistance was high to spectinomycin (98.4%), nalidixic acid (85.7%), and penicillin (84.1%), but low to gentamycin (1.6%) and cefotaxime (1.6%). The high frequency of toxin genes and antimicrobial resistance gene observed in S. aureus isolates from chicken could pose a challenge to food safety and may have therapeutic and zoonotic implications.     

Incidence,Antibiotic Susceptibility,and Toxin Profiles of Bacillus cereus sensu lato Isolated from Korean Fermented Soybean Products

Korean fermented soybean products, such as doenjang, kochujang, ssamjang, and cho‐kochujang, can harbor foodborne pathogens such as Bacillus cereus sensu lato (B. cereus sensu lato). The aim of this study was to characterize the toxin gene profiles, biochemical characteristics, and antibiotic resistance patterns of B. cereus sensu lato strains isolated from Korean fermented soybean products. Eighty‐eight samples of Korean fermented soybean products purchased from retails in Seoul were tested. Thirteen of 26 doenjang samples, 13 of 23 kochujang samples, 16 of 30 ssamjang samples, and 5 of 9 cho‐kochujang samples were positive for B. cereus sensu lato strains. The contamination level of all positive samples did not exceed 4 log CFU/g of food (maximum levels of Korea Food Code). Eighty‐seven B. cereus sensu lato strains were isolated from 47 positive samples, and all isolates carried at least one enterotoxin gene. The detection rates of hblCDA, nheABC, cytK, and entFM enterotoxin genes among all isolates were 34.5%, 98.9%, 57.5%, and 100%, respectively. Fifteen strains (17.2%) harbored the emetic toxin gene. Most strains tested positive for salicin fermentation (62.1%), starch hydrolysis (66.7%), hemolysis (98.9%), motility test (100%), and lecithinase production (96.6%). The B. cereus sensu lato strains were highly resistant to β‐lactam antibiotics such as ampicillin, penicillin, cefepime, imipenem, and oxacillin. Although B. cereus sensu lato levels in Korean fermented soybean products did not exceed the maximum levels permitted in South Korea (<10⁴ CFU/g), these results indicate that the bacterial isolates have the potential to cause diarrheal or emetic gastrointestinal diseases.     

Antimicrobial resistance and genetic characterization of coagulase-negative staphylococci from bovine mastitis milk samples in Korea

Coagulase-negative staphylococci (CNS) are one of the most common bovine mastitis pathogens found worldwide. In this study, we investigated the prevalence and distribution of CNS species in mastitis milk samples and further characterized the methicillin-resistant (MR) CNS. A total of 311 CNS were isolated from 3,692 quarter milk samples from 1,373 dairy cattle at 81 farms between 2013 and 2017. Further evaluation of the CNS isolates revealed 14 CNS species among the samples and 3 predominant species—namely, Staphylococcus chromogenes, Staphylococcus simulans, and Staphylococcus epidermidis. Resistance was higher in S. epidermidis than in other CNS species except for resistance against oxacillin in Staphylococcus sciuri. Resistance to β-lactams was the most common in all CNS species (8.4% in ampicillin, 21.2% in oxacillin, and 13.5% in penicillin). Conversely, only minimal resistance to cephalothin, ceftiofur, and pirlimycin/novobiocin was found. Twenty-one isolates from 4 species were mecA-carrying MRCNS strains, including 18 S. epidermidis and 1 each of S. sciuri, Staphylococcus equorum, and Staphylococcus hominis. The majority of the mecA-carrying MRCNS isolates were produced in the biofilm. Furthermore, multidrug-resistant sequence type 179 isolate produced the strongest biofilm. Seven genotypes were detected in the 18 MR S. epidermidis strains, the most predominant of which persisted on a farm for 2 yr. Our findings for the antimicrobial susceptibility profiles and genotypic characterization of the MRCNS isolates could provide valuable information for controlling the spread of resistance and the selection of appropriate antimicrobial therapies for mastitis in the future. Further, strategic antibiotic use for mastitis treatment and hygienic management practices aimed at the prevention of the growth of resistant bacteria are urgently needed on dairy farms.     

High prevalence of antimicrobial‐resistant Escherichia coli from animals at slaughter: a food safety risk

BACKGROUND: There has been concern about the increase of antimicrobial resistant bacteria and protection of animal and public health, along with food safety. In the present study, we evaluate the incidence of antimicrobial resistance among 192 strains of Escherichia coli isolated from faecal samples of healthy food‐producing animals at slaughter in Portugal. RESULTS: Ninety‐seven % of the pig isolates, 74% from sheep and 55% from cattle were resistant to one or more antimicrobial agents, with the resistances to ampicillin, streptomycin, tetracycline and trimethoprim–sulfamethoxazole the most common phenotype detected. Genes encoding resistance to antimicrobial agents were detected in most of the resistant isolates. Ninety‐three % of the resistant isolates were included in the A or B1 phylogenetic groups, and the virulence gene fimA (alone or in association with papC or aer genes) was detected in 137 of the resistant isolates. Five isolates from pigs belonging to phylogroup B2 and D were resistant to five different antimicrobial agents. CONCLUSION: Our data shows a high percentage of antibiotic resistance in E. coli isolates from food animals, and raises important questions in the potential impact of antibiotic use in animals and the possible transmission of resistant bacteria to humans through the food chain. © 2012 Society of Chemical Industry     

Occurrence and Antimicrobial Susceptibility of Listeria monocytogenes Isolated from Brined White Cheese in Jordan

Listeria monocytogenes is a serious foodborne pathogen that has been isolated from different dairy food products. Several foodborne outbreaks of listeriosis have been associated with consumption of cheese. The aims of this study were to determine the occurrence of L. monocytogenes and Listeria spp. in brined white cheese (BWC) sold in Jordan, and to determine the susceptibility of isolated L. monocytogenes to antimicrobials. Three hundred and fifty samples of 5 different types of BWC (akkawi, boiled, halloumi, pasteurized, and shellal) were collected from a local market in Jordan. The ISO (11290-1) procedure was followed for isolation and identification of Listeria spp. from cheese samples and a polymerase chain reaction (PCR) technique was used for confirmation of L. monocytogenes isolates. The VITEK2 automated system was used for testing antimicrobial susceptibility of L. monocytogenes isolates. The overall prevalence of Listeria spp. in cheese sample was 27.1%. L. monocytogenes was isolated from 39 (11.1%) samples. Other isolated species were L. grayi (6.9%), L. innocua (2%), L. ivanovii (4%), L. seeligeri (2%), and L. welshimeri (0.3%). The pH values and salt concentrations of L. monocytogenes positive cheese samples ranged from 5.10 to 6.32 and 5.64 to 13.16, respectively. L. monocytogenes isolates were sensitive or intermediate susceptible to imipenem, gentamicin, linezolid, teicoplanin, vancomycin, fusidic acid, trimethoprim/sulfamethoxazole, benzylpenicillin, ciprofloxacin, erythromycin, tetracycline, and rifampicin, but resistant to fosfomycin, oxacillin, and clindamycin.     

SIDEROPHORE PRODUCTION, SERUM RESISTANCE, HEMOLYTIC ACTIVITY AND EXTENDED-SPECTRUM β-LACTAMASE-PRODUCING KLEBSIELLA SPECIES ISOLATED FROM MILK AND MILK PRODUCTS

This study aimed at the isolation and identification of Klebsiella spp. from dairy product to establish their public health significance by determining their virulence factors, antibiotic resistance and extended‐spectrum β‐lactamase (ESBL). Klebsiella pneumoniae, Klebsiella oxytoca and Klebsiella rhinoscleromatis were identified in 25 (58%), 11 (26%) and 7 (16%) isolates, respectively. A high prevalence of Klebsiella isolates had virulence factors such as siderophore production (63%), serum resistance (32.5%) and hemolytic activity (58%). ESBL‐producing Klebsiella spp. was detected in 35% of the isolates. Resistance to the antimicrobial agents tested was found to be much higher in the ESBL‐producing Klebsiella spp. than in non‐ESBL‐producing isolates. All ESBL‐producing Klebsiella spp. showed high‐level resistance to cephalosporins and monobactams. The majority of the serum resistant, siderophore, hemolysin and ESBL producers were K. pneumoniae.     

Antibiotic Resistance Traits and Molecular Subtyping of Staphylococcus aureus Isolated from Raw Sheep Milk Cheese

The main objective of the present research was to evaluate the antibiotic resistance profiles of Staphylococcus aureus isolated from raw sheep milk cheese. A total of 150 strains were isolated from curd cheese samples and identified as S. aureus. The survey on antibiotic resistance was carried out on 47 strains, selected among isolates showing differences in the banding pattern after Pulsed Field Gel Electrophoresis (PFGE) screening or, belonging at the same pulsotype but isolated from different cheese samples. On selected strains antimicrobial resistance against ampicillin, penicillin, cloxacillin, tetracycline, erythromycin, and vancomycin was assessed by broth microdilution method. The presence of the genes coding for antibiotic resistance and virulence factors (agr alleles, sea‐see, and tst) was also investigated by PCR. Thirty‐one isolates belonging to agrI and agrIII groups carried at least one gene coding for enterotoxins or toxic shock syndrome toxin. Approximately 60% of the selected strains were susceptible to the tested antibiotics. Twelve of 47 isolates showed multiple resistance against ampicillin and penicillin. Only 1 strain, represented by a unique PFGE profile showed simultaneous resistance to ampicillin, penicillin and cloxacillin. Single resistance against tetracycline was found in 5 isolates belonging to 2 different pulsotypes. The results of this study suggest that the recovery of S. aureus resistant strains in raw milk cheese samples is quite common but it is limited to few antibiotic classes, mainly β‐lactams and tetracyclines. None of the strains showed resistance to erythromycin and vancomycin.     

Phenotypic and Genotypic Antimicrobial Resistance Traits of Foodborne Staphylococcus aureus Isolates from Shanghai

Staphylococcus aureus is a recognized pathogen in humans, which causes nosocomial infections and food poisoning. The transmission of antibiotic resistant S. aureus (ARSA), especially methicillin‐resistant S. aureus, between food products and humans has become a serious problem. Hence, it is necessary to monitor S. aureus through the food supply chain. In this study, the disk diffusion method and epsilometer test were performed to determine the prevalence of ARSA in 78 foodborne isolates using 18 antibiotics. The highest resistance frequency was found for penicillin G (74.4%), followed by erythromycin (59.0%) and clindamycin (44.9%), whereas no vancomycin‐resistant isolates were found. The 78 isolates could be subtyped into 31 resistance profiles and 11 clusters based on their antimicrobial susceptibility. Furthermore, Polymerase chain reaction (PCR) screening for the presence of 13 genes conferring antibiotic resistance was conducted. The presence of resistance genes was relatively high: bla_TEM (80.8%), ermB (41.0%), grlA (38.5%), ermC (35.9%), and aac6’/aph2” (35.9%). The incidence of antibiotic resistance was significantly correlated to food types (p = 0.018), with isolates from meat and raw milk more resistant to antibiotics than those from frozen food and vegetables.     

Antimicrobial susceptibility of isolated pathogens from patients with contact lens-related bacterial keratitis in Crete,Greece: A ten-year analysis

PurposeTo evaluate the bacterial spectrum and antimicrobial susceptibilities of pathogens isolated from contact lens-related bacterial keratitis cases in a large academic Greek hospital.MethodsAll adult patients with positive corneal scrapings or contact lens culture between 2007 and 2016 at the University Hospital of Heraklion, Greece, were retrospectively identified through a local microbiology database and their medical records were reviewed.ResultsA total of 240 isolates were recovered from 131 patients with culture-proven contact lens-associated bacterial keratitis. The most common microorganism identified was Serratia marcescens (17.1% of total isolates), followed by Pseudomonas aeruginosa, Klebsiella spp. and coagulase-negative staphylococci (CoNS). Rates of aztreonam-resistant P. aeruginosa and erythromycin-resistant CoNS decreased in recent years, while the decrease in oxacillin-resistant CoNS was statistically significant (p=0.009). More than 90% of the isolated organisms (S. marcescens, P. aeruginosa, Klebsiella spp. and CoNS) were susceptible to ciprofloxacin or gentamicin.ConclusionGram-negative microorganisms are the most common causative pathogens of contact lens-related keratitis in the region of Crete. Topical antibacterials containing quinolones or gentamicin represent an effective empirical treatment for the majority of the cases. This is quite encouraging, considering that the present study was conducted in a country characterised by high antimicrobial resistance rates. However, culture-driven antimicrobial treatment is mandatory for this sight-threatening infection.