Karlo Muratoglu

Prevalence of staphylococcal enterotoxins, toxin genes and genetic-relatedness of foodborne Staphylococcus aureus strains isolated in the Marmara Region of Turkey

Staphylococcus aureus is a major foodborne pathogen and it has the ability to produce a number of extracellular toxins. We analyzed 1070 food samples obtained from retail markets and dairy farms in the Marmara Region of Turkey for the presence of S. aureus. Out of 147 isolates, 92 (62.6%) were enterotoxigenic. PCR was used to investigate the presence of staphylococcal enterotoxin genes (sea, seb, sec, sed, see, seg, seh, sei, sej, sek, sel, sem, sen, seo, sep, seq and seu), exfoliative toxin genes (eta and etb) and the toxic-shock syndrome toxin gene (tst). The PCR results showed that 53.3% of the isolates contained staphylococcal enterotoxin-like (SEl) toxin genes (seg, seh, sei, sej, sek, sel, sem, sen, seo, sep, seq and seu) which were more frequent than classical enterotoxin genes (sea to see). Furthermore, seo, sei, sem, seg, seu and sec were found in 37.0, 32.7, 30.4, 29.3, 29.3 and 27.2% of the isolates, respectively. The tst gene was detected and confirmed by DNA sequencing in 9 isolates. The presence of eta and etb were not found in the isolates. Enterotoxigenic capabilities of isolates with SEA-SEE were investigated by ELISA. Enterotoxigenic S. aureus isolates produced one to three enterotoxins, with the most frequently produced types being enterotoxin A and C. There was a correlation of 72.1% between production of a specific toxin and the presence of the respective genes. PFGE analysis was used to identify genetic-relatedness of enterotoxigenic S. aureus isolates and the results revealed that 13 groups of isolates from different or the same origin that contained the same genes showed 100% homology with indistinguishable band patterns. The other enterotoxigenic isolates showed related band patterns with 72-86% homology in sea-, 61-90% homology in sec-, 80-96% homology in seh-, and 69-96% homology in sep-positive isolates. To our knowledge, this is the first study to examine enterotoxins and related gene contents of S. aureus food isolates in the Marmara Region of Turkey.

Prevalence and Antibiotic Resistance of Foodborne Staphylococcus aureus Isolates in Turkey

Abstract In this study, 154 Staphylococcus aureus isolates were detected from 1070 food samples (14.4%) collected from seven cities in Turkey. Antimicrobial susceptibility testing against 21 antibiotics was performed by agar disk diffusion method, and those isolates resistant to any antibiotic were further analyzed to determine minimum inhibitory concentration by E-test and polymerase chain reaction analysis of vanA and mecA genes. According to disk diffusion test results, a total of 139 strains were resistant to at least one tested antibiotic, with 39 (25.3%) strains being multidrug resistant (MDR) and the other 15 strains being susceptible to all antibiotics. Penicillin G, linezolid, erythromycin, and tetracycline took up 71.4%, 23.4%, 18.2%, and 15.6% of the tested strains, respectively. In addition, all of the strains were susceptible to vancomycin, oxacillin, cefoxitin, and imipenem. Only one strain (S158B) was resistant to both teicoplanin and cefazolin. On the other hand, the presence of vanA and mecA genes was not detected in the strains. Pulsed-field gel electrophoresis analysis was used to identify genetic-relatedness of the MDR strains. It is noteworthy that some strains from different sources showed 100% homology; however, some of MDR strains were found unrelated with 60% or less homology. The high diversity observed in pulsed-field gel electrophoresis results indicated the possible contamination of S. aureus from different sources and routes.

Frequency and phylogeny of norovirus in diarrheic children in Istanbul, Turkey

BACKGROUND Norovirus (NoV) is recognised as one of the most common causes of foodborne infections. Contaminated shellfish, food, water and hospitals are well documented sources of the virus. OBJECTIVE NoV in diarrheic children has not previously been investigated in Istanbul, Turkey, hence the aim of this study was to detect and investigate the frequency and phylogeny of human NoV genogroups I and II in children with acute gastroenteritis. STUDY DESIGN 238 stool samples were collected from diarrheic children from 2 hospitals (Cerrahpasa Medical School and Haseki) in Istanbul and analysed by ELISA, RT-PCR and real-time RT-PCR using both SYBR Green and probe-based assays for human NoV. Primers targeting the RNA-polymerase gene were used for RT-PCR to allow DNA sequencing of Turkish NoV strains and phylogenetic analysis to be performed. RESULTS NoV GII was detected in 36 (15.1%) of 238 samples by SYBR Green real-time RT-PCR, 10.9% by a probe-based real-time RT-PCR and 10.5% by ELISA (Ridascreen). Genogroup II (GII) the Turkish NoVs clustered with including GII4 (72.2%), GII16 (5.5%), GIIb (16.7%) and GIIe (5.5%). Two variants of GII4 (GII4-2006b and GII4-2008), GII16 and recombinant noroviruses (GIIb and GIIe) were identified. CONCLUSION This study shows a high frequency and genetic diversity of NoV GII infections in children with acute gastroenteritis in Istanbul, Turkey.

Investigations on the frequency of norovirus contamination of ready-to-eat food items in Istanbul, Turkey, by using real-time reverse transcription PCR

Investigation of norovirus (NoV) contamination of food items is important because many outbreaks occur after consumption of contaminated shellfish, vegetables, fruits, and water. The frequency of NoV contamination in food items has not previously been investigated in Turkey. The aim of this study was to investigate the frequency of human NoV genogroups (G) I and II in ready-to-eat tomatoes, parsley, green onion, lettuce, mixed salads, and cracked wheat balls. RNA was extracted with the RNeasy Mini Kit, and a real-time reverse transcription (RT) PCR assay was performed using primers specific for NoV GI and GII. Among the 525 samples analyzed, NoV GII was detected in 1 green onion sample and 1 tomato sample by both SYBR Green and TaqMan real-time RT-PCR assays; no GI virus was detected. The Enterobactericaeae and Escherichia coli levels in the NoV-positive green onion were 6.56 and 1.28 log CFU/g, and those in the tomato were 5.55 and 1.30 log CFU/g, respectively. No significant difference in the bacterial levels was found between the NoV-positive and NoV-negative samples. This study is the first in which NoV GII was found in ready-to-eat food collected from Istanbul, Turkey; thus, these foods may be considered a risk to human health. Epidemiological studies and measures to prevent NoV infection should be considered.

Effect of lemon juice on the survival of Salmonella Enteritidis and Escherichia coli in cig kofte (raw meatball)

Purpose – The purpose of this study is to investigate the effect of lemon juice on the survival of Salmonella Enteritidis and Escherichia coli in cig kofte (raw meatball).Design/methodology/approach – Cig kofte samples were inoculated one by one with both bacteria at high inoculum levels and were treated with different doses of fresh lemon juice (2, 5, 10 and 15 ml) for 10 seconds, 30 seconds, and 1, 5, 15, 30 and 60 minutes.Findings – Treatments of lemon juice for different exposure times caused reduction ranging between 0.1 and 1.7 log CFU/g for Salmonella Enteritidis and 0.1 and 2.1 log CFU/g for E.coli. Results showed that lemon juice caused slight decrease in Salmonella Enteritidis and E.coli as an immediate inhibitor, but this effect increased with concentration and time.Originality/value – This is a research study to provide information on the effectiveness of lemon juice which is squeezed generally before eating cig kofte, on the presence of the surface flora to strengthen the hygienic quality of ...

The microbiological quality of stuffed mussels (Midye Dolma) sold in Istanbul

Purpose – This study was performed to determine the microbial quality of stuffed mussels and to discuss the microbiological quality criteria of ready‐to‐eat (RTE) foods defined in the Turkish Food Codex (TFC).Design/methodology/approach – Stuffed mussel (Midye Dolma), which can be classified as RTE foods, made from mussel and rice, cooked separately then put together in the shell, is commonly consumed in Turkey. This special food might be an important source of microorganisms especially pathogen bacteria because of preparation and serving process. During the period of March‐October 2006, a total of 168 stuffed mussel samples were collected randomly from restaurants, buffets and street sellers located in Istanbul and analysed some microbiological parameters.Findings – Coliforms were detected in 130 (77.38 per cent), Escherichia coli in 37 (22.02 per cent), Staphylococcus aureus in 40 (23.80 per cent), Bacillus cereus in 65 (38.69 per cent), yeast and moulds in 147 (87.50 per cent) and sulphite‐reducing ana...

The prevalence of Clostridium difficile in cattle and sheep carcasses and the antibiotic susceptibility of isolates

Clostridium difficile is an anaerobic, spore forming, rod shaped bacterium frequently isolated from butchery animals in recent years. The aim of this study is to evaluate the presence of C. difficile (especially ribotype 027 and 078) in cattle and sheep carcasses and to investigate the antibiotic susceptibility of isolates. The bacterium was isolated in 83 out of 247 (33.6%) cattle and 78 out of 308 (25.3%) sheep carcass samples. 15/83 (18.1%) cattle and 6/78 (7.7%) sheep isolates were identified as ribotype 027, whereas the other hypervirulent isolate ribotype 078 could not be detected among the analysed samples. Almost all isolates were susceptible to amoxicillin-clavulanic acid (98.8%), vancomycin (96.9%) and tetracycline (97.5%), whereas resistant to cefotaxim (97.5%) and imipenem (87.0%). In conclusion, the results demonstrate the presence of toxigenic C. difficile isolates in cattle and sheep carcasses on the slaughter line. As a result, the results of this study demonstrate the presence of toxigenic C. difficile isolates in cattle and sheep carcasses on the slaughter line.

THE EFFECT OF HEAT PROCESSING ON PCR DETECTION OF GENETICALLY MODIFIED SOY IN BAKERY PRODUCTS

Soy is commonly added to various foods because of its quality and health benefits. However, it is also the most commonly cultivated genetically modified (GM) crop. Hence, detection of GM soy in food preparations is an important goal of food science research. Although DNA is relatively stable during processing, and polymerase chain reaction (PCR) can be used to analyze processed food products, the processing factor-induced DNA degradation limits these methods. We evaluated the effect of different baking temperatures on the detection of GM soy in cookies by preparing cookies containing various amounts of GM soy and baking them at different temperatures and for different times. The effect of heat on the DNA quality was inspected by detecting the cauliflower mosaic virus 35S promoter and species-specific lectin sequences. As conclusion, the heating process affects the sensitivity of the PCR screening of GM organisms significantly, and the detection limit is elevated.