White Cheese Samples Research Articles

Bacteriological Quality and Incidence of Some Pathogenic Bacteria in Fresh White Cheese Sold in Tripoli, Libya

Abstract The aim of this study was to evaluate the bacteriological quality and safety of fresh white cheese sold in Tripoli, Libya. The study lasted for approximately 7 months (November 2011-May 2012), during this period 87 fresh white cheese samples were collected from seven different areas (4 to 5 factories from each area with the rate of 3 duplicates). The samples were tested for temperature at receiving, pH and acidity, total aerobic counts, total coliform counts and the detection of incidence of some pathogenic bacteria including: Escherichia coli, Escherichia coli O157:H7, Staphylococous aureus, Salmonella spp., Aeromonas hydrophila and Listeria monocytogenes. Results indicated that the average temperature, % acidity, and pH of the tested samples were (15.80°C ± 5.8, 0.21 ± 0.02% and 5.81 ± 0.06) respectively. Data indicated that 70.1% of the samples exceeded the Libyan standard for white cheese No. 366 in respect to temperature, while pH of all samples was within the limits of such standard. On the other hand, means of total aerobic counts, total coliform counts, and the numbers of Staphyloccoccus aureus were (38 × 107, 74 × 105, 35 × 104 and 53 × 103 cfu/g) respectively of the study.

English

Polymerase chain reaction (PCR) assay was used to detect pathogenic bacteria in white cheese samples using suitable primers which are based on specific genes. A total of 70 samples of white cheese were collected from different parts of Baghdad for detection of the pathogens, Escherichia coli, Staphylococcus aureus and Bacillus cereus. Cheese was made ​​locally from different sources of milk (buffalo, cows and sheep). Samples were cultured in liquid enrichment medium (Nutrient Broth) and incubated at 37°C for a period of 16-20 h. DNA was extracted by kit extraction and pathogens were diagnosed. Multiplex polymerase chain reaction was used with primers targeting specialized sites of the target gene in one reaction and the results showed the presence of E. coli (87%), S. aureus (20%) and B. cerues (18%). The results of this study revealed that PCR was a rapid and useful tool for detection of pathogenic bacteria in cheese. Key words: Cheese, polymerase chain reaction (PCR), Escherichia coli, Staphylococcus aureus, Bacillus cereus.

Occurrence and Behavior of Pseudomonas Organisms in White Soft Cheese.

Absract :. One hundred and twenty five random samples of white soft cheese ; fivety of each Damietta , kariesh and twenty five of Feta cheese were collected from sreet vendors, supermarkets and groceries at Damietta province.All samples examined chemically and sensory and proved to be fit for human consumption. The prevalence of pseudomonas spp. was 68% and 58% with mean count 9.02x104±2.87x104 and 2.43x105±9.32x104 for Damietta and kariesh cheese respectively. Pseudomonas spp were not detected in Feta cheese.The most prevalent spp was p.fluorescens (35.14% and 45.5%) while p.aeruginosa (21.26% and 15.2%) ; p.putida (27% and 18.2%) and p. stutzeri (16.21%and 21.21%) for Damietta and kariesh cheese respectively. All strains of p.aeruginosa showed 100% resistance to Ampicillin , Ampicillin/sulbectam , Cefazolin ,Tigecyclin , Nitrofurantoin andTrimethoprim / sulfamethoxazole followed by Cefatriaxone and Cefepim 23% while Imipenem , Meropenem , Amikacin , Gentamycin and Tobramycin showed 100% sensetivety followed by Ciprofloxacin and Moxifloxacin 69.23% . Viability of p.aeruginosa during manufacture and storage of Damietta cheese was studied , Using 0.1% Potassium sorbate with 10% Sodium chloride and cold storage of cheese had great inhibitory effect on p.aeruginosa at14th day. The public health significance of these finding were discussed. .

The Occurrence of Aflatoxin M1 in Milk, soft cheese and yoghurt in Baghdad Province by Using ELISA Test

Milk and dairy products are fundamental components in the human diet and may be the principle way for entrance of Aflatoxin M1 (AFM1) in to the human body. All milk and dairy products samples were tested for the occurrence of AFM1 by the competitive ELISA technique. Out of 32 bovine raw milk samples that were collected from eight villages around Baghdad province, 32 samples (100 %) were contaminated with AFM1 ranging from 0.15 to 86.96ng/kg with mean value of 42.37±26.07 ng/kg, of which 17 samples were contaminated with concentrations < 50 ng/kg and 15 samples exceeded the maximum acceptable level of AFM1 in milk (50 ng/kg) imposed by the European legislation. The raw milk samples belonged to animals fed with composite and stored fodder as in Althahab Alabiadh, Radhwaniya and Fadhaliya villages had higher significantly AFM1 concentrations over all the other five villages (Grazing feed). All 32 (100%) locally produced soft white cheese samples analyzed were contaminated with AFM1 ranging from 31.84 to 89.44 ng/kg with the mean value of 59.92±17.03 ng/kg. Out of 32 locally produced yoghurt samples analyzed, 32 samples (100%) were contaminated with AFM1 ranging from 0.16 to 42.74 ng/kg with the mean value of 16.92±11.55 ng/kg. Thirty samples (100%) of the examined 30 imported UHT milk samples that were collected from different commercial companies in the province of Baghdad presented significantly high contamination level with AFM1 that were found to range from 0.18 to 85.66 ng/kg.

Occurrence and antibiotic resistance of Escherichia coli,Staphylococcus aureus and Bacillus cereus in raw milk and dairy products in Turkey

In this survey, 150 samples of raw milk, white cheese and ice cream from three different dairy‐processing plants in Ankara were analysed to find out if they were contaminated with Escherichia coli, Staphylococcus aureus or Bacillus cereus. The highest contamination percentages were found in raw milk samples as follows: B. cereus (90%), E. coli (74%) and S. aureus (56%) followed by cheese (70% B. cereus, 60% E. coli, and 48% S. aureus) and ice cream (56% E. coli, 36% S. aureus and 20% B. cereus). The survey showed that 2% of cheese samples were contaminated with E. coli O157. It was also found that the numbers of S. aureus and E. coli in raw milk, cheese and ice cream samples exceeded the numbers permitted under the Turkish Food Codex (TFC). The number of B. cereus in raw milk, cheese and ice cream samples was lower than the limit given in the TFC standards. The study also showed that E. coli and S. aureus exhibit resistance to ampicillin, penicillin, tetracycline, erythromycin, gentamicin and trimethoprim/sulfamethoxazole. Escherichia coli isolates also showed resistance to chloramphenicol and ciprofloxacin but none of them exhibited resistance to cefotaxime. All S. aureus isolates were found to be susceptible to cefotaxime, chloramphenicol, and ciprofloxacin. Bacillus cereus isolates were found to be resistant to ampicillin, penicillin and trimethoprim/sulfamethoxazole and sensitive to cefotaxime, chloramphenicol, ciprofloxacin erythromycin, gentamicin and tetracycline.

Microbiological Assessment and Prevalence of Food Borne Pathogens in Street Vended Wara - Nigerian White Cheese

Fifty white cheese (wara) samples were collected from ten local cheese hawkwer/vendors within Abeokuta, Nigeria to determine the microbial characteristics and the prevalence of some common food borne pathogen. The total aerobic plate counts (TPC) ranged from 6.8 to 9.5 log cfu/g; Lactic acid bacteria counts ranged from 2.8 to 6.9 log cfu/g while yeasts and mould counts ranged from 2.8 to 6.6 log cfu/g. Significant (p<0.05) variations were found between vendors and microbial population. The mean S. aureus count was 6.5 log cfu/g Salmonella, Presumptive E. coli and Bacillus cereus counts were 0.3, 2.4 and 3.3 log cfu/g respectively. B. cereus was found in 78%, Staphylococcus aureus in 100%, presumptive E. coli in 56% and Salmonella spp in 6% of the 50 wara cheese samples tested. None of the samples analyzed contained Vibrio cholerae. The results indicate that wara cheese presents a potential hazard for public health; and necessary precaution will have to be taken to improve the sanitary practices and cheese manufacturing technique.

Determination of Some Virulence Factors in Staphylococcus aureus, Enterococcus faecalis and Enterococcus faecium Isolated from Meat and Milk Products

AbstractThe aim of this work is to characterize Staphylococcus aureus, Enterococcus faecalis and Enterococcus faecium isolated from meat and milk products in Ankara, Turkey. A total of 40 S. aureus, 55 E. faecalis and 30 E. faecium isolates were isolated from raw calf meat (minced), chicken drumsticks, raw milk, ice cream and white cheese samples. A high proportion of S. aureus isolates had slime formation (80%), biofilm formation (70%), deoxyribonuclease (DNase) activity (53%), hemolytic activity (40%), protease production (80%) and lipase production (45%). The frequency of positive slime formation, DNase activity, hemolysis and protease production for E. faecalis isolates was 36, 5, 7 and 16%, and for E. faecium isolates was 50, 10, 13 and 6%. Neither biofilm formation nor lipase production was detected in Enterococcus isolates. It was found that S. aureus isolates were resistant to penicillin (77%), ampicillin (67%), erythromycin (30%), tetracycline (25%), chloramphenicol (20%) and gentamicin (17%), but they were sensitive to vancomycin and teicoplanin. All Enterococcus spp. isolates were sensitive to ampicillin, chloramphenicol, teicoplanin, tetracycline and vancomycin, but they were resistant to erythromycin (47%), gentamicin (14%) and penicillin (4%).Practical ApplicationsA number of factors contribute to the virulence of Staphylococcus aureus and enterococci, including slime, biofilm, deoxyribonuclease, hemolysin, protease and lipase production. Our results suggest that the determination of these traits in food isolates of S. aureus and enterococci could be valuable tests for the meat and dairy industry. Antimicrobial resistance is an important public health concern worldwide. Thus, antibiotic resistance can also be used as adjunct test in the food industry. In the absence of control measures, virulent and antibiotic‐resistant organisms might be transmitted to humans by the consumption of meat, milk and their product.

Prevalence and antibiotic resistance of extended-spectrum beta-lactamase (ESBL) producing Escherichia coli and Klebsiella species isolated from foods of animal origin in Turkey

The present study includes 50 Klebsiella oxytoca, 45 Escherichia coli and 13 Klebsiella pneumoniae isolated from raw meat (chicken drumsticks and minced meat), raw milk, white cheese and ice cream samples and was undertaken to determine the prevalence of extended-spectrum β-lactamase (ESBL)-producing isolates and antibiotic resistance. The double-disk synergy test was used to determine ESBL production. ESBL production was detected in 20 of 45 E. coli (44.4%), 5 of 13 K. pneumoniae (38.5%) and 13 of 50 K. oxytoca (26%) isolates. Resistance of all isolates to 14 antibiotics was determined by the disk diffusion method. All isolates showed resistance to ampicillin but none exhibited resistance to imipenem, ertapenem, cefepime and piperacillin/tazobactam. E. coli andKlebsiella spp. isolates have also been found resistant to cefotaxime, ceftazidime, ceftriaxone, aztroenam, tetracycline and ciprofloxacin. All isolates were resistant to two or more antimicrobial agents. Key words: β-Lactamases, antibiotic resistance, Escherichia coli, Klebsiella spp., foods.

Biofilm, protease and lipase properties and antibiotic resistance profiles of staphylococci isolated from various foods

In this study, a total of 209 isolates were isolated from raw calf meat (minced), chicken drumsticks, raw milk, ice cream and white cheese samples. One hundred and seventy-five (83.7 %) coagulase-negative Staphylococci (CNS) and 34 (16.3%) coagulase-positive staphylococci (CPS) were isolated from these samples. The majority of Staphylococcusisolates showed biofilm formation (75.1%) and slime formation (68.4%). The frequency of positive protease and lipase production for Staphylococcus aureus isolates were 23.5 and 11.8%, respectively. Proteolytic and lipolytic activitiy were not found in the otherStaphylococcus species. The overall antimicrobial susceptibility profiles revealed that the highest percentage of resistance was detected for ampicillin (33.8%), tetracycline (26.3%), erythromycin (20.6%), methicillin (17.2%) and gentamicin (12.4%). The susceptibility to vancomycin, chloramphenicol, amikacin and clindamycin were 100% for all isolates. Key words: Coagulase positive, coagulase negative Staphylococcus, biofilm, slime, lipase, protease, antibiotic resistance, foods

Aflatoxin M1 contamination in white and Lighvan cheese marketed in Rafsanjan, Iran

This study was a screening survey to determine the occurrence of aflatoxin M1 (AFM1) in 82 cheese samples composed of white cheese (45 samples) and Lighvan cheese (37 samples) obtained from supermarkets and retail outlets in Rafsanjan city of Iran. The competitive enzyme immunoassay method was used for determination of the toxin in the samples. Aflatoxin M1 was detected in 39 (47.6%) samples, consisting of 29 (64.4%) white cheese (mean: 135 ng/kg; range: 93.3–309 ng/kg) and 10 (27%) Lighvan cheese samples (mean: 90.8 ng/kg; range: 70.5–203 ng/kg). According to Iranian national standard limit for AFM1 in cheese (200 ng/kg), 9 samples (20%) of white cheese and 1 sample (2.70%) of Lighvan cheese had levels above the limit. It was concluded that the contamination of the samples with AFM1 in such a level could be considered as a serious public health problem.

Determination of Nitrate and Nitrite Contents of Syrian White Cheese

The levels of nitrate and nitrite were determined in 102 samples of Syrian white cheese which represents the major production of total cheeses, manufactured mainly from cow’s milk and sheep’s milk in a less degree. Determination of nitrate and nitrite levels has been made by spectrophotometric method. The results for nitrate in cow’s and sheep’s milk cheeses reveal an average of 5.10 and 6.25 mg/kg, respectively. The results for nitrite in cow’s and sheep’s milk cheese were found to contain 1.24 and 1.31 mg/kg as an average, respectively. Several factors can play a role in the interpretation of the high nitrate content, such as livestock nutrition by forge with high nitrate load and water contaminated with nitrogen fertilizer and domestic effluents, primitive production techniques in many cases, and adding nitrate salts to prevent the growth of gas-producing bacteria caused by failing in the hygienic conditions. There is a necessity to apply strict controls to reduce the presence of these two anions in the Syrian white cheese.

Characterization of thermophilic streptococci isolated from rustic white cheese

The thermophilic streptococci are dominant members of the microflora of several types of cheese produced with a natural starter. A total of 205 isolates of thermophilic streptococci were obtained from 70 samples of white cheese which had been collected from producing areas of different regions of Syria during 2009 and 2010. The isolates were cocci gram positive and catalase negative. From these isolates, 120 were identified as Enterococcus spp. including: 72 isolates of E. faecium, 35 isolates of E. fecalis and 13 isolates of E. durans. In addition, 70 isolates were identified as Streptococcus including: 50 isolates of S. thermophilus, and 20 isolates of S. equines. Fifteen isolates of cocci grew at 45°C with spherical morphology, gram positive and catalase negative. The PCR technique could be efficiently used for identifying and typing the thermophilic streptococci.

English

The study was based on surveying ten samples of Sudanese white cheese packaged in two different containers (plastic and metal), collected from different supermarkets in Khartoum state. The comparison of chemical composition and microbial count was done. The experimental results showed that the average ash content, moisture, acidity, pH, and total solid content means were 7.00 &plusmn; 2.73, 45.00 &plusmn; 4.81, 0.85 &plusmn; 0.12, 5.72 &plusmn; 0.25 and 45.00 &plusmn; 10.63%, respectively for cheese samples packaged in plastic containers while for samples packaged in metal containers, the values were 5.50 &plusmn; 1.11, 52.06 &plusmn; 9.18, 1.85 &plusmn; 0.41, 5.06 &plusmn; 0.33 and 55.00 &plusmn; 9.35% for ash content, moisture, acidity, pH, and total solid content, respectively. The average chemical properties showed significant differences between the samples packaged in the two types of containers (P &le; 0.05). The logarithm counts of total bacteria, yeasts and moulds for the samples packaged in plastic containers were found to be 8.86 &plusmn; 4.80 and 0.12 &plusmn; 0.16, respectively. On the other hand, the logarithm counts of total bacteria, yeasts and moulds for the samples packaged in metal containers were found to be 13.86 &plusmn; 3.61 and 015 &plusmn; 0.09, respectively. A clear significant differences between the samples packaged in the two types of containers (P &le; 0.05) was found. There was no significant correlation between the total bacteria counts and the moisture content of the samples packaged in plastic and metal containers (P &le; 0.05). The total bacterial count of the samples packaged in plastic and metal containers showed significant correlation to the pH value of the cheese samples collected from the supermarket (P &le; 0.05). &nbsp; Key words:&nbsp;Sudanese white cheese, average ash content, microbial count, moisture.

Dispersive liquid–liquid microextraction combined with field-amplified sample stacking in capillary electrophoresis for the determination of non-steroidal anti-inflammatory drugs in milk and dairy products

Dispersive liquid–liquid microextraction (DLLME) was coupled with field-amplified sample stacking in capillary electrophoresis (FASS) for the determination of five non-steroidal anti-inflammatory drugs (NSAIDs) in bovine milk and dairy products. After extraction, the enriched analytes were back-extracted into a basic aqueous solution for injection into CE. Under optimum conditions, enrichment factors were in the range 46–229. Limits of detection of the analytes ranged from 3.0 to 13.1μgkg−1 for all matrices analysed. Calibration graphs showed good linearity with coefficients of determination (R2)⩾0.9915 and relative standard deviations (RSD%) of the analyses in the range of 0.6–6.2% (n=5). Recoveries of all NSAIDs from bottled milk, raw milk, yogurt and white cheese samples were in the ranges of 86.6–109.3%, 84.3–100.5%, 77.4–107.3%, and 90.9–101.6%, respectively. DLLME–FASS-CE was demonstrated to be a rapid and convenient method for the determination of NSAIDs in milk and dairy products.

Detection of Enterotoxigenic Staphylococcus aureus in Raw Milk and Dairy Products by Multiplex PCR

The aim of this study was to investigate the prevalence of enterotoxigenic Staphylococcus aureus in 122 samples, including 60 raw milk, 32 white cheese, 10 kashar cheese, 10 butter, and 10 ice cream samples obtained from Samsun province, Turkey. In this study, S. aureus was detected in 64 samples, including raw milk (45/60; 75%), white cheese (12/32; 37.5%), kashar cheese (3/10; 30%), butter (3/10; 30%), and ice cream (1/10; 10%) samples. A total of 81 isolates were identified as S. aureus by PCR with the presence of 16S rRNA and nuc genes. The presence of genes encoding the staphylococcal enterotoxins (SEs) SEA, SEB, SEC, and SED was detected by multiplex PCR. According to the analysis, seven isolates from the raw milk samples (7/51; 13.7%) were enterotoxigenic; five of them produced SEA (5/7; 71.4%), one produced SEB (1/7; 14.2%), and one produced SEA+SEB (1/7; 14.2%). Four isolates from the white cheese samples (4/21; 19%) produced the SEA (1/4; 25%), SEC (1/4; 25%), SED (1/4; 25%), and SEA+SED (1/4; 25%) toxins. Two isolates from the kashar cheese samples (2/4; 50%) were found to be enterotoxigenic; one produced SEA (1/2; 50%) and the other produced SED (1/2; 50%). One isolate from the butter samples (1/4; 25%) showed enterotoxigenic character (SEB, 1/1; 100%). The products were found to be potentially hazardous to public health because of the fact that levels of contamination were higher than 105-106 cfu/g ml in 39% (25/64, 17 raw milk, 7 white cheese, and 1 butter) of the analyzed samples.

Determination of Aflatoxin Levels in Some Dairy Food Products and Dry Nuts Consumed in Saudi Arabia

Three hundred and ninety-three samples of dairy products (124 samples of white cheese, 61 samples of cream cheese, 76 samples of Kashar cheese, and 132 samples of butter), 91 samples of cashew nut and 97 macademia nut marketed in Eastern Province, Saudi Arabia during September 2010-September 2011, were analyzed for aflatoxin M1 (AFM1), total aflatoxin and AFB1 by microtitre plate enzyme linked immunosorband assay (ELISA) The incidence of AFM1 contamination in dairy products analyzed was 82%. Total aflatoxin contamination was determined in 84 (92.3%) of 91 cashew nut and in 88 (90.7%) of 97 macademia nut whereas total aflatoxin contamination was not detected in 3 (3.2%) of 91 cashew nut samples and in 12 of 97 macademia nut samples. AFB1 was found in 84 (92.3%) of 91 cashew nut and in 83 (85.5%) of 97 samples of macademia nut samples. AFM1 levels in 3 (2.4%) white cheese, 4 (3.0%) of butter, 2 (3.2%) in cream cheese and 5 (6.5%) of Kashar cheese samples were found higher than the maximum acceptable levels as set by European Union.Continuous surveillance program may be warranted to monitor regularly the occurrence of aflatoxins in foodstuffs.

Assessment of aflatoxin M1 in milk and milk products from Punjab, Pakistan

The basic objective of this research was to investigate the incidence and occurrence of aflatoxin M1 (AFM1) in milk and dairy products produced in the province of Punjab, Pakistan. Milk samples (107) and dairy products including yogurt (96), white cheese (119), cheese cream (150) and butter (74) samples were analyzed using High performance liquid chromatography equipped with fluorescence detector. The results have shown that AFM1 was detected in 71% of milk samples with 58% samples were found above the permissible limit of European Union (EU). AFM1 was detected in 61% of yogurt, 78% white cheese, 59% cheese cream and 45% butter samples with 47, 15, 11 and 52% samples of yogurt, white cheese, cheese cream and butter, respectively were found above the recommended limit of EU. The data of the present study will be helpful for the implementation of regulatory limit for AFB1 in order to minimize or avoid AFM1 in milk and milk products from Pakistan and also gives insights that whether the occurrence of AFM1 in dairy products was considered as a possible risk for consumers health.

Survey of aflatoxin M1 in milk and dairy products consumed in Burdur, Turkey

The aim of this study was to investigate the occurrence of aflatoxin M1 (AFM1) in dairy product samples in Burdur city. A total of 315 samples of dairy products were collected during 2008. Of the 315 samples analysed, AFM1 in 246 samples (78.1%) was found to range from 5.5 to 800 ng/kg. In addition, AFM1 levels of 16 raw milk, two pasteurised milk, only one milk powder and three white cheese samples were above the Turkish Food Codex. It is concluded that the occurrence of AFM1 in dairy products may be considered as a possible hazard for public health.

ISOLATION AND BIOTYPING OF STAPHYLOCOCCUS AUREUS FROM WHITE CHEESE IN BASRAH LOCAL MARKETS

Fifty samples of white cheese were collected from 3 different local market of Basra city AL0basra, (15), AL0ashar(20) and AL0jumh urya(15 ) samples respectively, After being examined by culturing on MSA media , the results reveal thate 53.33% , 50% , and 13.33% of Staph aureus were isolate from white chees respectively . Depending on the biotyping , the percentage of biotype A Staphylococcus aureus was 90% and biotype C was 10% . Antibiotic sensitivety test showed that 55% ,55% , 45% , 35% of isolates were more sensitive to Erythromycin Chloramphenicol Tetracycline and Ciprofloxacin respectively .

Spoilage potentials and antimicrobial resistance of Pseudomonas spp. isolated from cheeses

Pseudomonas spp. are aerobic, gram-negative bacteria that are recognized as major food spoilage microorganisms. A total of 32 (22.9%) Pseudomonas spp. from 140 homemade white cheese samples collected from the open-air public bazaar were isolated and characterized. The aim of the present study was to investigate the biochemical characteristics, the production of extracellular enzymes, slime and β-lactamase, and antimicrobial susceptibility of Pseudomonas spp. isolated from cheeses. The identified isolates including Pseudomonas pseudoalcaligenes, Pseudomonas alcaligenes, Pseudomonas aeruginosa, Pseudomonas fluorescens biovar V, and P. pseudoalcaligenes ssp. citrulli were found to produce extracellular enzymes, respectively: protease and lecithinase production (100%), and lipase activity (85.7, 42.9, 100, and 100%, and nonlipolytic, respectively). The isolates did not produce slime and had no detectable β-lactamase activity. The antimicrobial susceptibility of the isolates was tested using the disk diffusion method. Pseudomonas spp. had the highest resistance to penicillin G (100%), then sulphamethoxazole/trimethoprim (28.1%). However, all Pseudomonas spp. isolates were 100% susceptible to ceftazidime, ciprofloxacin, amikacin, gentamicin, and imipenem. Multidrug-resistance patterns were not observed among these isolates. In this study, Pseudomonas spp., exhibiting spoilage features, were isolated mainly from cheeses. Isolation of this organism from processed milk highlights the need to improve the hygienic practices. All of the stages in the milk processing chain during manufacturing have to be under control to achieve the quality and safety of dairy products.