Category Archives: Staphylococcus aureus

Research – Investigation and Follow-Up of a Staphylococcal Food Poisoning Outbreak Linked to the Consumption of Traditional Hand-Crafted Alm Cheese

MDPI

Staph

Image CDC

Staphylococcal food poisoning (SFP) is one of the most important foodborne diseases. This work describes a SFP event linked to the consumption of alm cheese and involved three people belonging to the same family. Leftovers of the consumed cheese, samples from the grocery store and the producing alm were collected and tested for Coagulase positive staphylococci (CPS) enumeration and for the presence of staphylococcal enterotoxins (SEs). Isolates were typed with MLST, spa typing, and tested for SEs and methicillin resistance genes. An in vitro test evaluated SEs production in relation to bacterial growth. The presence of CPS and SEs was detected in all cheese samples and all isolates belonged to the same methicillin sensitive ST8/t13296 strain harbouring sedser and sej genes. The in vitro test showed the production of enterotoxins started from 105 CFU/mL. The farmer was prescribed with corrective actions that led to eradication of the contaminating strain. View Full-Text

Research – Biofilm-Forming Ability of Pathogenic Bacteria Isolated from Retail Food in Poland

Journal of Food Protection

ABSTRACT

Biofilms have a significant impact on food safety in the food industry. Many foodborne outbreaks have been associated with pathogenic bacterial strains that can form a biofilm. The present study was conducted under the Official Control and Monitoring Program in Poland to examine the ability of pathogenic bacteria collected from retail food samples to form biofilms. Biofilm formation was assessed by qualitative detection of extracellular polymeric substances on Congo red agar, by adherence to glass with the tube method, by the crystal violet biofilm (CV) assay, and by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. A total of 40 isolates from food samples (10 strains each of Listeria monocytogenes, Staphylococcus aureus, Escherichia coli, and Bacillus cereus) were examined. The strains were classified as adherent, slightly adherent, or nonadherent; biofilm production was classified as weak (WBP), moderate (MBP), or strong (SBP); and metabolic activity was classified as weak (WMA), moderate (MMA), or high (HMA). The incubation conditions and time influenced the amount of biofilm formed as well as did the growth medium. In the test tubes with Luria-Bertani broth (LBB), 22.5% of the strains were adherent and 77.5% were slightly adherent. Stronger adhesion was obtained in brain heart infusion (BHI) with 2% sucrose; 60% of the isolates were classified as adherent. With the CV assay with LBB, SBP was noted for 7.5% of the strains after 24 h of incubation and for 37.5% of the strains after 48 h. In BHI plus 2% sucrose, SBP was noted for 42.5 and 37.6% of the strains after 24 and 48 h, respectively. With the MTT assay with LBB, HMA was found for 15% of the strains after 24 h of incubation and for 25% of the strains after 48 h. In BHI plus 2% sucrose, 70 and 85% of the incubated strains were classified as HMA after 24 and 48 h, respectively.

HIGHLIGHTS
  • All tested bacterial pathogens isolated from food formed biofilms.
  • Biofilm formation was dependent on environmental conditions and the assay used.
  • Culture in BHI plus 2% sucrose produced more biofilm with higher metabolic activity.

Research – Attributing Human Foodborne Diseases to Food Sources and Water in Japan Using Analysis of Outbreak Surveillance Data

Journal of Food Protection

ABSTRACT

In Japan, strategies for ensuring food safety have been developed without reliable scientific evidence on the relationship between foodborne diseases and food sources. This study aimed to provide information on the proportions of foodborne diseases caused by seven major causative pathogens (Campylobacter spp., Salmonella, enterohemorrhagic Escherichia coli [EHEC], Vibrio parahaemolyticus, Clostridium perfringens, Staphylococcus aureus, and norovirus) attributed to foods and to explore factors affecting changes in these source attribution proportions over time using analysis of outbreak surveillance data. For the calculation of the number of outbreaks attributed to each source, simple-food outbreaks were assigned to the single-food category in question, and complex-food outbreaks were classified under each category proportional to the estimated probability. During 2007 to 2018, 8,730 outbreaks of foodborne diseases caused by seven pathogens were reported, of which 6,690 (76.6%) were of unknown source. We estimated the following source attribution proportions of foodborne diseases: chicken products (80.3%, 95% uncertainty interval [UI] 80.1 to 80.4) for Campylobacter spp.; beef products (50.1%, UI 47.0 to 51.5) and vegetables (42.3%, UI 40.9 to 45.5) for EHEC; eggs (34.6%, UI 27.8 to 41.4) and vegetables (34.4%, UI 27.8 to 40.8) for Salmonella; finfish (50.3%, UI 33.3 to 66.7) and shellfish (49.7%, UI 33.3 to 66.7) for V. parahaemolyticus; grains and beans (57.8%, UI 49.7 to 64.9) for S. aureus; vegetables (63.6%, UI 48.5 to 74.6), chicken products (12.7%, UI 4.6 to 21.5), and beef products (11.1%, UI 8.5 to 13.1) for C. perfringens; and shellfish (75.5%, UI 74.7 to 76.2) for norovirus. In this study, we provide the best available evidence-based information to evaluate the link between foodborne diseases and foods. Our results on source attribution for Campylobacter spp. and EHEC suggest that the strict health regulations for raw beef were reflected in the proportions of these diseases attributed to this food.

HIGHLIGHTS
  • Source attribution proportions of foodborne diseases in Japan were estimated.
  • Source attribution was useful to guide interventions and evaluate their effect.
  • Strict health regulations for raw beef affected source attribution proportions.

Norway – Microbiological control of pasteurised and unpasteurised dairy products, 2018

Mattilsynet

The microbiological quality was generally good for the 189 dairy products on the Norwegian market that the Norwegian Food Safety Authority examined in 2018. Nevertheless, we see that there are microbiological challenges in connection with unpasteurised dairy products.

What did we investigate? 189 samples of unpasteurised and pasteurised cheeses and other dairy products produced in Norway and in the EU.
Period: 2018
What were we looking for?

The four categories have been analysed for various disease-causing bacteria (pathogens). These choices are made in order to get the most information for each category.

The different categories are:

PN = pasteurised milk product produced in Norway.

P EU = pasteurised milk product produced outside Norway.

UN = unpasteurised milk product produced in Norway.

U EU = unpasteurised milk product produced outside Norway.
 

The various disease-causing infectious agents we analysed for:

Listeria monocytogenes (pathogen): PN, P EU, UN, U EU, number 189 pcs.

Shigatoxin-producing Escherichia coli (STEC) (pathogen): UN, U EU, number 96 pcs.

E. coli (hygiene parameter): PN, UN, U EU, 169 st.

S. aureus (hygiene parameter): UN, number 71 st.

Toxins (enterotoxin) from S. aureus (pathogen): UN, U EU, number 96 pcs.

Salmonella (pathogen): U EU, number 25 st.

What did we find?

Listeria monocytogenes : No detection in 189 samples of dairy product.

Shigatoxin-producing Escherichia coli (STEC):
One finding in French red cow cheese of cow’s milk ( E. coli O-, stx2 and eae ). A total of 25 unpasteurised milk products produced outside Norway were examined. No findings in 71 unpasteurised milk products from Norway.

Escherichia coli (hygiene parameter):
In 73 pasteurised milk products from Norway, there was a detection and this was above the lower limit value (100 cfu / g) but below the upper limit value (1,000 cfu / g). No E. coli was detected above the detection limit of 10 colony forming units / g sample (cfu / g) in the other samples.

In 61 of the 71 unpasteurised milk products produced in Norway, E. coli was not detected above the detection limit of 10 colony-forming units / g sample (cfu / g). 3 st. (4.2%) was above 100 cfu / g.

In unpasteurised dairy products from the EU (25), 5 (20%) of the products had more than 100 cfu/ g E. coli. There is no microbiological criterion for E. coli in the regulations for unpasteurised cheeses.

Staphylococcus aureus:
Of 71 samples, none exceeded the regulatory limit of 10,000 cfu/ g.

Of the 96 unpasteurised dairy products examined, the enterotoxins AE Toxins (enterotoxins), which some S. aureus can produce , were not detected .

Salmonella was not detected in the 25 samples of unpasteurised milk products produced outside Norway.

Report Link

Research – Anti‐adhesive effects of sialic acid and Lactobacillus plantarum on Staphylococcus aureus in vitro

Journal of Food Safety

Staphylococcus aureus (S. aureus) is a common food‐borne pathogen that causes severe diseases after adhesion to epithelial cells. Lactobacillus inhibits pathogenic bacterial adhesion and infection. In addition, sialic acid (SA) is widely known for its beneficial biological functions. A new way of reducing the occurrence of diseases and curbing the overuse of antibiotics is ingesting prebiotics and probiotics that regulate the intestinal flora. In this study, we first evaluated the anti‐adhesive effects of several strains of Lactobacillus on S. aureus. The study revealed that the S. aureus adhesion was inhibited by all the strains of Lactobacillus. Besides, the rate of inhibition by L. plantarum Z‐4 was significantly higher than other Lactobacillus species. We then investigated the effects of different SA concentrations (40, 100, 150, 200, and 260 μg/ml) on the growth and adhesion characteristics of L. plantarum and S. aureus. The results showed that SA influences bacterial adhesion by regulating the bacteria’s growth characteristics. Finally, the effects of SA combined with Lactobacillus on the adhesion of S. aureus were assessed by competition, exclusion and displacement methods. SA with a concentration of 260 μg/mL combined with L. plantarum had the highest inhibition effect on the competition assays. In addition, the expression of S. aureus adhesion‐related genes was reduced. This provides a new perspective on the application of SA and/or L. plantarum and its potential to resist adhesion of S. aureus.

Research – Microbiological control of pasteurized and unpasteurized dairy products, 2018 – Norway

Mattilsynet

The microbiological quality was generally good for the 189 dairy products on the Norwegian market that the Norwegian Food Safety Authority examined in 2018. Nevertheless, we see that there are microbiological challenges in connection with unpasteurized dairy products.

What did we investigate? 189 samples of unpasteurized and pasteurized cheeses and other dairy products produced in Norway and in the EU.
Period: 2018
What were we looking for? The four categories have been analyzed for various disease-causing bacteria (pathogens). These choices are made in order to get the most information for each category.

The different categories are:

PN = pasteurized milk product produced in Norway.

P EU = pasteurized milk product produced outside Norway.

UN = unpasteurized milk product produced in Norway.

U EU = unpasteurized milk product produced outside Norway.
The various disease-causing infectious agents we analyzed for:

Listeria monocytogenes (pathogen): PN, P EU, UN, U EU, number 189 pcs.

Shigatoxin-producing Escherichia coli (STEC) (pathogen): UN, U EU, number 96 pcs.

E. coli (hygiene parameter): PN, UN, U EU, 169 st.

S. aureus (hygiene parameter): UN, number 71 st.

Toxins (enterotoxin) from S. aureus (pathogen): UN, U EU, number 96 pcs.

Salmonella (pathogen): U EU, number 25 st.

What did we find? Listeria monocytogenes : No detection in 189 samples of dairy product.

Shigatoxin-producing Escherichia coli (STEC):
One finding in French red cow cheese of cow’s milk ( E. coli O-, stx2 and eae ). A total of 25 unpasteurized milk products produced outside Norway were examined. No findings in 71 unpasteurized milk products from Norway.

Escherichia coli (hygiene parameter):
In 73 pasteurized milk products from Norway, there was a detection and this was above the lower limit value (100 kde / g) but below the upper limit value (1,000 kde / g). No E. coli was detected above the detection limit of 10 colony forming units / g sample (kde / g) in the other samples.

In 61 of the 71 unpasteurized milk products produced in Norway, E. coli was not detected above the detection limit of 10 colony-forming units / g sample (kde / g). 3 st. (4.2%) was above 100 kde / g.

In unpasteurized dairy products from the EU (25), 5 (20%) of the products had more than 100 kde / g E. coli. There is no microbiological criterion for E. coli in the regulations for unpasteurized cheeses.

Staphylococcus aureus:
Of 71 samples, none exceeded the regulatory limit of 10,000 kde / g.

Of the 96 unpasteurized dairy products examined, the enterotoxins AE Toxins (enterotoxins), which some S. aureus can produce , were not detected .

Salmonella was not detected in the 25 samples of unpasteurized milk products produced outside Norway.

RASFF Alerts – Microbial Contamination – microbial contamination (yeasts, molds, Staphylococcus aureus) of pyramide cake products and rum balls

European Food Alerts

RASFF

microbial contamination (yeasts, molds, Staphylococcus aureus) of pyramide cake products and rum balls from Germany in Germany

Research – Microbiological Quality of Cooked Chicken: Results of Monitoring in England (2013 to 2017)

Journal of Food Protection

Results from monitoring of the microbiological quality of 2,721 samples of ready-to-eat cooked chicken collected between 2013 to 2017 in England were reviewed: 70% of samples were from retail, catering, or manufacture and 30% were imported and collected at English ports. Samples were tested for a range of bacterial pathogens and indicator organisms. Six samples (<1%) had unsatisfactory levels of pathogens that were potentially injurious to health. Neither Salmonella nor Campylobacter were recovered from any samples. Two samples from catering settings contained either an unsatisfactory level of Bacillus cereus (5 × 106 CFU/g) or an unsatisfactory level of coagulase-positive staphylococci (1.6 × 104 CFU/g). Listeria monocytogenes was recovered from 36 samples (1 at manufacture, 26 at catering, and 9 at retail) and in 4 samples, unsatisfactory levels (≥102 CFU/g) were detected (3 samples collected at catering and 1 sample at retail). For L. monocytogenes, there were no significant differences between the rates of contamination for the samples collected from ports, manufacture, retail supermarkets, and other retailers (P = 0.288). There were no differences between the rates of contamination for other potential pathogens detected between samples from different settings. The prevalence of hygiene indicators (Escherichia coli, Enterobacteriaceae, and aerobic colony counts) at import was significantly lower than in samples collected from manufacturers, retail, or catering (P < 0.01). Samples collected from catering gave poorer results than those from all other settings. Regardless of the stage in the food chain, samples from Thailand and from other non–European Union countries were of significantly better microbiological quality with respect to indicator organisms than those from the United Kingdom or from other European Union countries (P = <0.001).

HIGHLIGHTS
  • Routine microbiological monitoring of 2,721 samples was reviewed.
  • Six samples (<1%) were unsatisfactory due to the levels of bacterial pathogens.
  • Hygiene indicator bacteria were significantly higher in samples from catering.
  • Port samples had significantly lower levels of hygiene indicators.

Research – Evaluation of Listeria monocytogenes and Staphylococcus aureus survival and growth during cooling of hams cured with natural-source nitrite

Journal of Food Protection

Growing consumer desires for clean label, “natural” products drives more meat processors to cure meat products with natural sources of nitrate or nitrite such as celery juice powder (CJP). One particular challenge for these producers is to identify safe cooling rates in CJP-cured products where extended cooling could allow growth of pathogens. USDA FSIS recently added guidelines for stabilization of meat products cured using naturally occurring nitrites, based on control of Clostridium spp . Currently a gap exists in knowledge associated with safe cooling rates of naturally cured ham that prevent the growth of Listeria monocytogenes and Staphylococcus aureus that are potential post-lethality contaminants. The study aims to investigate the temperature profiles of naturally cured hams of typical sizes during refrigerator cooling and determine the survival behavior of S. aureus and L. monocytogenes on ham during these cooling periods. Whole (14 lbs / 6300 g), half (6 lbs / 2700 g) and quarter hams (3 lbs / 1400 g) were slowly cooked in Alkar Ò 1000 smokehouse until internal temperatures reached a minimum of 140 ° F / 60°C and were immediately transferred into walk-in cooler (38 ° F / 3.3°C). Cooling times for all sizes were within the requirements for cured products but not for uncured products. Worst-case scenarios of post-processing surface contamination were simulated by inoculating small, naturally cured ham samples with S. aureus or L. monocytogenes , which were cooled in controlled processes (130-45 ° F / 54.4-7.2 ° C in 720-900 min). B y the end of cooling, each inoculum had a small decrease of 0.5-0.6 log CFU/g. This study helps small processors identify if recommended concentrations of natural cure agents that prevent growth of Clostridium pathogens may also prevent growth of other pathogens during cooling, which aids small meat processors in production and quality control.

Research – Antimicrobial and preservative effects of the combinations of nisin, tea polyphenols, rosemary extract and chitosan on pasteurized chicken sausage

Journal of Food Protection

The study evaluated the antimicrobial and antioxidant effects of the combinations of nisin (NS), tea polyphenols (TP), rosemary extract (RE) and chitosan (CS) on low-temperature chicken sausage. An orthogonal test revealed that the most effective antimicrobial compositions were equal-quantity mixtures of 0.05% NS + 0.05% TP + 0.03% RE + 0.55% CS . The mixture also produced strong antimicrobial and antioxidant effects in low-temperature chicken sausage related to extend the shelf life to more than 30 days at 4°C. The study also investigated the inhibitory zone of NS, TP, RE and CS against Pseudomonas aeruginosa , lactic acid bacteria (LAB) and Staphylococcus aureus which were the dominant spoilage bacteria in low-temperature chicken sausage. NS had the greatest inhibitory effect on LAB and Staphylococcus aureus , exhibiting clear zone diameters of 19.7 mm and 17.8 mm respectively. TP had the largest inhibitory effect on Pseudomonas aeruginosa , exhibiting a clear zone diameter of 18.2 mm. These results indicated that the combination of NS, TP, RE and CS could be used as natural preservative s to efficiently inhibit the growth of spoilage microorganisms in low-temperature chicken sausage so as to improve its safety and shelf life.