scholarly journals Survival of Selected Pathogenic Bacteria during PDO Pecorino Romano Cheese Ripening

Dairy ◽  
2020 ◽  
Vol 1 (3) ◽  
pp. 297-312
Author(s):  
Giacomo Lai ◽  
Rita Melillo ◽  
Massimo Pes ◽  
Margherita Addis ◽  
Antonio Fadda ◽  
...  
Keyword(s):  
Pathogenic Bacteria ◽  
Salt Content ◽  
Raw Milk ◽  
Salmonella Spp ◽  
Growth And Survival ◽  
E Coli ◽  
Cheese Ripening ◽  
Protected Designation Of Origin ◽  
Low Levels ◽  
First Time

This study was conducted to assess, for the first time, the survival of the pathogenic bacteria Listeria monocytogenes, Salmonella spp., Escherichia coli O157:H7, and Staphylococcus aureus during the ripening of protected designation of origin (PDO) Pecorino Romano cheese. A total of twenty-four cheese-making trials (twelve from raw milk and twelve from thermized milk) were performed under the protocol specified by PDO requirements. Sheep cheese milk was first inoculated before processing with approximately 106 colony-forming unit (CFU) mL−1 of each considered pathogen and the experiment was repeated six times for each selected pathogen. Cheese composition and pathogens count were then evaluated in inoculated raw milk, thermized milk, and cheese after 1, 90, and 150 days of ripening. pH, moisture, water activity, and salt content of cheese were within the range of the commercial PDO Pecorino Romano cheese. All the cheeses made from raw and thermized milk were microbiologically safe after 90 days and 1 day from their production, respectively. In conclusion, when Pecorino Romano cheese is produced under PDO specifications, from raw or thermized milk, a combination of factors including the speed and extent of curd acidification in the first phase of the production, together with an intense salting and a long ripening time, preclude the possibility of growth and survival of L. monocytogenes, Salmonella spp., and E. coli O157:H7. Only S. aureus can be still detectable at such low levels that it does not pose a risk to consumers.

scholarly journals Quality and safety of artisan cheese produced in the serrana region of Santa Catarina

2017 ◽  
Vol 38 (2) ◽  
pp. 739 ◽  
Author(s):  
Giane Helenita Pontarolo ◽  
Fernanda Danielle Melo ◽  
Caroline Lopes Martini ◽  
Paula Wildemann ◽  
Dileta Regina Moro Alessio ◽  
...  
Keyword(s):  
Salt Content ◽  
Raw Milk ◽  
Good Manufacturing Practice ◽  
Quality And Safety ◽  
Salmonella Spp ◽  
Santa Catarina ◽  
Maturation Period ◽  
E Coli ◽  
Coagulase Positive Staphylococci ◽  
Cheese Production

The serrano artisan cheese produced from raw milk of dairy cattle is a typical product of high-altitude farms in the states of Santa Catarina and Rio Grande do Sul. However, marketing of the cheeses occurs illegally because they lack the minimum maturation period required for cheese produced from raw milk. The production of artisan cheeses is required to follow strict hygiene standards. This study aimed to test the quality and safety of cheeses that were produced in 31 farms of the Serrana region in Santa Catarina after 14 and 28 days of maturation. Coliform count was measured at 35 °C, and presence of other microorganisms such as Escherichia coli, Staphylococcus, Listeria spp., and Salmonella spp. were also tested. Fat and protein percentages, acidity, salt content, and humidity were also evaluated. Data were subjected to statistical analyses using the SAS® software. After 14 and 28 days of maturation, 74.19% (23/31) and 64.52% (20/31) of samples, respectively, showed higher numbers of coliforms at 35 °C than those permissible by law. Higher than permissible numbers of E. coli were observed in 45.16% (14/31) and 48.39% (15/31) of the samples analyzed after 14 and 28 days of maturation, respectively. Coagulase-positive staphylococci values above 103 CFU/g were observed in 54.84% (17/31) and 51.61% (16/31) of cheese samples after 14 and 28 days of maturation, respectively. Contamination with Salmonella spp. was not detected. However, Listeria monocytogenes serovar 4b was isolated in 3.23% (1/31) and 6.45% (2/31) of samples after 14 and 28 days of maturation, respectively. The results of humidity tests classified the cheese samples into three categories: low, medium, and high humidity. Semi fat cheeses were predominant in both maturation periods, although the samples were classified in thin, semi fat, and fat cheeses. The main variations in the compositions of analyzed samples occurred for salt and acidity levels. The maturation process has not proven to be effective in reducing microbiological contamination to compliance levels. Considering the heterogeneity of the analyzed cheese samples, the frequency of non-conformities with respect to microorganisms and pathogens present in the samples, this study indicates the necessity to improve the Serrano artisan cheese production system through adoption of good manufacturing practice measures.

scholarly journals Isolation and Characterization of Bacteriophage ZCSE6 against Salmonella spp.: Phage Application in Milk

Biologics ◽  
2021 ◽  
Vol 1 (2) ◽  
pp. 164-176
Author(s):  
Abdallah S. Abdelsattar ◽  
Anan Safwat ◽  
Rana Nofal ◽  
Amera Elsayed ◽  
Salsabil Makky ◽  
...  
Keyword(s):  
Pathogenic Bacteria ◽  
Raw Milk ◽  
Salmonella Spp ◽  
Isolation And Characterization ◽  
Food Borne ◽  
Wide Range ◽  
Almost All ◽  
And Control ◽  
Milk And Dairy Products

Food safety is very important in the food industry as most pathogenic bacteria can cause food-borne diseases and negatively affect public health. In the milk industry, contamination with Salmonella has always been a challenge, but the risks have dramatically increased as almost all bacteria now show resistance to a wide range of commercial antibiotics. This study aimed to isolate a bacteriophage to be used as a bactericidal agent against Salmonella in milk and dairy products. Here, phage ZCSE6 has been isolated from raw milk sample sand molecularly and chemically characterized. At different multiplicities of infection (MOIs) of 0.1, 0.01, and 0.001, the phage–Salmonella interaction was studied for 6 h at 37 °C and 24 h at 8 °C. In addition, ZCSE6 was tested against Salmonella contamination in milk to examine its lytic activity for 3 h at 37 °C. The results showed that ZCSE6 has a small genome size (<48.5 kbp) and belongs to the Siphovirus family. Phage ZCSE6 revealed a high thermal and pH stability at various conditions that mimic milk manufacturing and supply chain conditions. It also demonstrated a significant reduction in Salmonella concentration in media at various MOIs, with higher bacterial eradication at higher MOI. Moreover, it significantly reduced Salmonella growth (MOI 1) in milk, manifesting a 1000-fold decrease in bacteria concentration following 3 h incubation at 37 °C. The results highlighted the strong ability of ZCSE6 to kill Salmonella and control its growth in milk. Thus, ZCSE6 is recommended as a biocontrol agent in milk to limit bacterial growth and increase the milk shelf-life.

scholarly journals The Survey of Microbial Quality of the Dry Sample, Extract and Brewing of some Medicinal Plants

2014 ◽  
Vol 6 (4) ◽  
pp. 478-482
Author(s):  
Razieh VALIASILL ◽  
Majid AZIZI ◽  
Maasome BAHREINI ◽  
Hossein AROUIE
Keyword(s):  
Medicinal Plants ◽  
Pathogenic Bacteria ◽  
Agar Medium ◽  
Total Count ◽  
Plate Count ◽  
Microbial Quality ◽  
Salmonella Spp ◽  
E Coli ◽  
Wide Range

Medicinal plants may be exposed to a wide range of microbial contamination during pre- and post- harvest stages and they can present high microbial counts. In this study, the microbial quality of 44 samples of dry herbs namely: mint (Menthaspp.), lemon balm (Melissa officinalis), summer savory (Satureja hortensis), zataria (Zataria multiflora), Indian valerian (Valeriana wallichii), their brewing and extracts were analyzed. Total count using plate count agar medium (PCA), coliform count by Violet Red Bile Agar (VRBL), Enterobacteriacea by Violet Red Bile Glucose (VRBG) were evaluated. Medium Baird-Parker agar (BP) medium and Tryptone Bile X-Gluc (TBX) medium were used for the isolation and enumeration of Staphylococcus aurous and E. coli spp. respectively. Furthermore, Xylose Lysine Deoxycholate agar medium (XLD) and Bismuth Sulfite Agar medium(BSA) were used for detection of Salmonella spp. Fungal and mold contamination was assessed using yeast extract glucose chloramphenicol agar. The results showed that the contamination of the samples with total count (100%) and Enterobacteriaceae (85%), total coliform (83%), mold and yeast (98%) and E. coli ssp. (2.27) were detected, including in the study samples the absence of pathogenic bacteria like Staphylococcus aurous, Salmonella spp. Moreover, the extract had a lower microbial load in comparison to dry herb samples. Also, the lowest and the highest of contamination rates were observed for Indian valerian and zataria, respectively. According to the results, there is a need to control the environmental conditions and improve hygiene in the production process; even more, it is recommended to choose a suitable decontamination method for disinfection during packing medicinal plants and during post-packing manipulation and transport.

Behavior of Escherichia coli O157:H7 on Damaged Leaves of Spinach, Lettuce, Cilantro, and Parsley Stored at Abusive Temperatures

2010 ◽  
Vol 73 (2) ◽  
pp. 212-220 ◽  
Author(s):  
ROWAIDA K. KHALIL ◽  
JOSEPH F. FRANK
Keyword(s):  
Escherichia Coli ◽  
Pathogenic Bacteria ◽  
Leaf Damage ◽  
Escherichia Coli O157 ◽  
Oxidation Reactions ◽  
Leaf Extracts ◽  
Romaine Lettuce ◽  
Growth And Survival ◽  
E Coli ◽  
Additional Information

Recent foodborne illness outbreaks associated with the consumption of leafy green produce indicates a need for additional information on the behavior of pathogenic bacteria on these products. Previous research indicates that pathogen growth and survival is enhanced by leaf damage. The objective of this study was to compare the behavior of Escherichia coli O157:H7 on damaged leaves of baby Romaine lettuce, spinach, cilantro, and parsley stored at three abusive temperatures (8, 12, and 15°C). The damaged portions of leaves were inoculated with approximately 105 CFU E. coli O157:H7 per leaf. The pathogen grew on damaged spinach leaves held for 3 days at 8 and 12°C (P &lt; 0.05), with the population increasing by 1.18 and 2.08 log CFU per leaf, respectively. E. coli O157:H7 did not grow on damaged Romaine leaves at 8 or 12°C, but growth was observed after 8 h of storage at 15°C, with an increase of less than 1.0 log. Growth of E. coli O157:H7 on Romaine lettuce held at 8 or 12°C was enhanced when inocula were suspended in 0.05% ascorbic acid, indicating the possibility of inhibition by oxidation reactions associated with tissue damage. Damaged cilantro and Italian parsley leaves held at 8°C for 4 days did not support the growth of E. coli O157:H7. Behavior of the pathogen in leaf extracts differed from behavior on the damaged tissue. This study provides evidence that the damaged portion of a leafy green is a distinct growth niche that elicits different microbial responses in the various types of leafy greens.

Behavior of Escherichia coli O157:H7 during the Manufacture and Aging of Gouda and Stirred-Curd Cheddar Cheeses Manufactured from Raw Milk

2010 ◽  
Vol 73 (12) ◽  
pp. 2217-2224 ◽  
Author(s):  
DENNIS J. D'AMICO ◽  
MARC J. DRUART ◽  
CATHERINE W. DONNELLY
Keyword(s):  
Escherichia Coli ◽  
Population Level ◽  
Raw Milk ◽  
Escherichia Coli O157 ◽  
Milk Whey ◽  
Selective Enrichment ◽  
Point Counts ◽  
E Coli ◽  
Unpasteurized Milk ◽  
Low Levels

This study was conducted to examine the fate of Escherichia coli O157:H7 during the manufacture and aging of Gouda and stirred-curd Cheddar cheeses made from raw milk. Cheeses were manufactured from unpasteurized milk experimentally contaminated with one of three strains of E. coli O157:H7 at an approximate population level of 20 CFU/ml. Samples of milk, whey, curd, and cheese were collected for enumeration of bacteria throughout the manufacturing and aging process. Overall, bacterial counts in both cheese types increased almost 10-fold from initial inoculation levels in milk to approximately 145 CFU/g found in cheeses on day 1. From this point, counts dropped significantly over 60 days to mean levels of 25 and 5 CFU/g in Cheddar and Gouda, respectively. Levels of E. coli O157:H7 fell and stayed below 5 CFU/g after an average of 94 and 108 days in Gouda and Cheddar, respectively, yet remained detectable after selective enrichment for more than 270 days in both cheese types. Changes in pathogen levels observed throughout manufacture and aging did not significantly differ by cheese type. In agreement with results of previous studies, our results suggest that the 60-day aging requirement alone is insufficient to completely eliminate levels of viable E. coli O157:H7 in Gouda or stirred-curd Cheddar cheese manufactured from raw milk contaminated with low levels of this pathogen.

Survival of Pathogenic Bacteria in Pesticide Solutions and on Treated Tomato Plants

2005 ◽  
Vol 68 (2) ◽  
pp. 296-304 ◽  
Author(s):  
TIFFANY T. Y. GUAN ◽  
GREGORY BLANK ◽  
RICHARD A. HOLLEY
Keyword(s):  
Membrane Filtration ◽  
Salmonella Enteritidis ◽  
Pathogenic Bacteria ◽  
Incubation Temperature ◽  
Bacterial Survival ◽  
Salmonella Spp ◽  
Tomato Plants ◽  
Sterile Saline ◽  
E Coli ◽  
Pesticide Formulations

The ability of Salmonella, Escherichia coli O157:H7, Listeria monocytogenes, and Shigella to survive or grow in pesticide solutions (Ambush 240EC, Benlate T-N-G, Bravo 500, Botran 75WP, Captan 80WDG, Parasol, and Vendex 50W) used by the horticultural industry was examined. In the laboratory, individual cultures were inoculated at 4 log CFU/ml in pesticides diluted with sterile saline to the lowest recommended spray concentrations. During 21°C incubation for ≤96 h, bacterial survivors in the samples and a control consisting of saline were enumerated either by agar surface plating or hydrophobic grid membrane filtration. Most formulations tested were somewhat inhibitory to the pathogenic bacteria. All inoculated bacteria survived or grew in Bravo 500. Among bacteria tested, Salmonella spp. were best able to survive and Listeria spp. were least able to survive in pesticide solutions. When the incubation temperature or pesticide concentration was increased, survival of Salmonella varied depending on the type of formulation. In the field, when a bacterial cocktail containing E. coli O157:H7 and Salmonella Enteritidis was added to Bravo 500 at 6 log CFU/ml, both organisms were recovered from leaves and fruit skins of sprayed tomato plants after the recommended 1 day-to-harvest interval. E. coli and Salmonella survived longer on tomato leaves when sprayed in saline (at least 26 and 56 days, respectively) than when sprayed in Bravo 500 (&gt;45 h and &lt;15 days, respectively). While Salmonella serovars Typhimurium and Heidelberg grew in the fungicide Bravo, and Enteritidis grew in the insecticide Vendex within 96 h at 21°C in the laboratory, pathogen growth in other pesticide formulations did not occur. Higher temperature (≤30°C) or doubling pesticide concentrations had either no or a negative effect on Salmonella Heidelberg survival. Use of unexpired pesticide formulations may have contributed to the reduced bacterial survival and growth found in the laboratory and during the field trials with Bravo.

Estimating Bacterial Pathogen Levels in New Zealand Bulk Tank Milk

2016 ◽  
Vol 79 (5) ◽  
pp. 771-780 ◽  
Author(s):  
J. C. MARSHALL ◽  
T. K. SOBOLEVA ◽  
P. JAMIESON ◽  
N. P. FRENCH
Keyword(s):  
New Zealand ◽  
Predictive Model ◽  
Pathogenic Bacteria ◽  
Fecal Contamination ◽  
Raw Milk ◽  
Quality Data ◽  
Bulk Tank Milk ◽  
E Coli ◽  
Cell Counts ◽  
Bulk Tank

ABSTRACT Zoonotic bacteria such as Campylobacter, Listeria, and Shiga toxin–producing Escherichia coli have been found in bulk tank milk in many countries, and the consumption of raw milk has been implicated in outbreaks of disease in New Zealand. Fecal contamination at milking is probably the most common source of pathogenic bacteria in bulk tank milk. Raw milk was collected from 80 New Zealand dairy farms during 2011 and 2012 and tested periodically for Campylobacter, E. coli O157, Listeria monocytogenes, and Salmonella. Milk quality data such as coliform counts, total bacterial counts, and somatic cell counts also were collected. By treating the total bacterial count as a proxy for fecal contamination of milk and utilizing farm and animal level prevalence and shedding rates of each pathogen, a predictive model for the level of pathogenic bacteria in bulk tank raw milk was developed. The model utilizes a mixture distribution to combine the low level of contamination inherent in the milking process with isolated contamination events associated with significantly higher pathogen levels. By simulating the sampling and testing process, the predictive model was validated against the observed prevalence of each pathogen in the survey. The predicted prevalence was similar to the observed prevalence for E. coli O157 and Salmonella, although the predicted prevalence was higher than that observed in samples tested for Campylobacter.

Susceptibility for antibiotics among faecal indicators and pathogenic bacteria in sewage treated effluents

2013 ◽  
Vol 8 (1) ◽  
pp. 1-6 ◽  
Author(s):  
Adel A. S. AL-Gheethi ◽  
Norli Ismail ◽  
J. Lalung ◽  
Azieda Talib ◽  
A. N. Efaq ◽  
...  
Keyword(s):  
Antibiotic Resistance ◽  
High Resistance ◽  
Pathogenic Bacteria ◽  
Sewage Treatment ◽  
Salmonella Spp ◽  
Sewage Treatment Plants ◽  
Total Coliforms ◽  
E Coli ◽  
Treated Effluents ◽  
Faecal Indicators

The objective of this work was to study the prevalence of antibiotic resistance phenotypes among total coliforms (TC), E. coli, E. faecalis and Salmonella spp. in the sewage treated effluents generated from three sewage treatment plants in Penang Malaysia. Among the isolates tested, TC and E. coli occurred high resistance for cephalexin (100 and 90.47%), ampicillin (80.93 and 95.23%) and ciprofloxacin (19.06 and 14.3%) compared to E. faecalis (42.86, 71.4 and 4.7%) and Salmonella spp. (59.8, 47.46 and 14.3%) respectively. All E. coli strains, 76.18% of TC, 66.66% of E. faecalis and 35% of Salmonella spp. were multi-resistant.

scholarly journals Evaluation of a Steam Pasteurization Process in a Commercial Beef Processing Facility

1997 ◽  
Vol 60 (5) ◽  
pp. 485-492 ◽  
Author(s):  
ABBEY L. NUTSCH ◽  
RANDALL K. PHEBUS ◽  
M. JAMES RIEMANN ◽  
DAVID E. SCHAFER ◽  
J. E. BOYER ◽  
...  
Keyword(s):  
Pathogenic Bacteria ◽  
Control Point ◽  
Meat Products ◽  
Steam Treatment ◽  
Salmonella Spp ◽  
Bacterial Populations ◽  
E Coli ◽  
Critical Control Point ◽  
Beef Processing ◽  
Steam Pasteurization

The effectiveness of a steam pasteurization process for reducing naturally occurring bacterial populations on freshly slaughtered beef sides was evaluated in a large commercial facility. Over a period of 10 days, 140 randomly chosen beef sides were microbiologically analyzed. Each side was sampled immediately before, immediately after, and 24 h after steam pasteurization treatment. Total aerobic bacteria (APC), Escherichia coli (generic), coliform, and Enterobacteriaceae populations were enumerated. The process significantly (P ≤ 0.01) reduced mean APCs from 2.19 log CFU/cm2 before treatment to 0.84 log CFU/cm2 immediately after and 0.94 log CFU/cm2 24 h after treatment. Before pasteurization (8 s steam exposure), 16.4% of carcasses were positive for generic E. coli (level of 0.60 to 1.53 log CFU/cm2), 37.9% were positive for coliforms (level of 0.60 to 2.26 log CFU/cm2), and 46.4% were positive for Enterobacteriaceae (level of 0.60 to 2.25 log CFU/cm2). After pasteurization, 0% of carcasses were positive for E. coli, 1.4% were positive for coliforms (level of 0.60 to 1.53 log CFU/cm2), and 2.9% were positive for Enterobacteriaceae (level of 0.60 to 1.99 log CFU/cm2). Of the 140 carcasses evaluated, one carcass was positive for Salmonella spp. before treatment (0.7% incidence rate); all carcasses were negative after steam treatment. This study indicates that steam pasteurization is very effective in a commercial setting for reducing overall bacterial populations on freshly slaughtered beef carcasses. The system may effectively serve as an important critical control point for HACCP systems at the slaughter phase of beef processing. In conjunction with other antimicrobial interventions (mandated by USDA to achieve zero tolerance standards for visible contamination) and good manufacturing practices, this process can play an important role in reducing the risk of pathogenic bacteria in raw meat and meat products.

scholarly journals A stress-induced block in dicarboxylate uptake and utilization in Salmonella

2019 ◽  
Author(s):  
Steven J. Hersch ◽  
Bojana Radan ◽  
Bushra Ilyas ◽  
Patrick Lavoie ◽  
William Wiley Navarre
Keyword(s):  
Pathogenic Bacteria ◽  
Constitutive Expression ◽  
Elongation Factor ◽  
Stringent Response ◽  
Close Relative ◽  
Translation Elongation ◽  
Growth And Survival ◽  
E Coli ◽  
Sense And Respond

AbstractBacteria have evolved to sense and respond to their environment by altering gene expression and metabolism to promote growth and survival. In this work we demonstrate that Salmonella displays an extensive (>30 hour) lag in growth when subcultured into media where dicarboxylates such as succinate are the sole carbon source. This growth lag is regulated in part by RpoS, the RssB anti-adaptor IraP, translation elongation factor P, and to a lesser degree the stringent response. We also show that small amounts of proline or citrate can trigger early growth in succinate media and that, at least for proline, this effect requires the multifunctional enzyme/regulator PutA. We demonstrate that activation of RpoS results in the repression of dctA, encoding the primary dicarboxylate importer, and that constitutive expression of dctA induced growth. This dicarboxylate growth lag phenotype is far more severe across multiple Salmonella isolates than in its close relative E. coli. Replacing 200 nt of the Salmonella dctA promoter region with that of E. coli was sufficient to eliminate the observed lag in growth. We hypothesize that this cis-regulatory divergence might be an adaptation to Salmonella’s virulent lifestyle where levels of phagocyte-produced succinate increase in response to bacterial LPS. We found that impairing dctA repression had no effect on Salmonella’s survival in acidified succinate or in macrophage but propose alternate hypotheses of fitness advantages acquired by repressing dicarboxylate uptake.ImportanceBacteria have evolved to sense and respond to their environment to maximize their chance of survival. By studying differences in the responses of pathogenic bacteria and closely related non-pathogens, we can gain insight into what environments they encounter inside of an infected host. Here we demonstrate that Salmonella diverges from its close relative E. coli in its response to dicarboxylates such as the metabolite succinate. We show that this is regulated by stress response proteins and ultimately can be attributed to Salmonella repressing its import of dicarboxylates. Understanding this phenomenon may reveal a novel aspect of the Salmonella virulence cycle, and our characterization of its regulation yields a number of mutant strains that can be used to further study it.

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