Category Archives: Food Microbiology Research

Australia – How a frozen meringue led investigators to the source of a potent Salmonella outbreak


When people started getting sick from a particularly potent strain of salmonella last year, a team of experts rushed to try to trace the source of the outbreak.

Key points:

  • Salmonella enteritidis (SE) is worse than other forms of the bacteria because it infects the hen’s ovaries, meaning the bacteria is deposited inside eggs
  • Other forms of salmonella are just found on the outside of eggs and human illness can be avoided by washing them and discarding those with cracked shells
  • SE is found in egg industries around the world, but until last year Australian farms were free of the harmful bacteria

Investigation is the key to managing and containing an outbreak’s impact — for consumers, farmers and entire industries, which can be brought to their knees if things go badly.

But investigators depend on people’s memories of what they’ve eaten, making it a seemingly impossible task.

A few weeks after being interviewed, one of those people remembered they had a frozen meringue cake in their freezer, leftover from a birthday party, around the time they got sick.

Officers went to that person’s home, collected the cake and had it tested.

“We were able to isolate the salmonella enteritidis and it had that same whole genome sequence. At the same time we could see who manufactured that cake,” Ms Szabo said.

HPS publishes annual surveillance reports for Cryptosporidium, Giardia and Cyclospora in Scotland, 2018



Article: 53/3701

On 17 September 2019, Health Protection Scotland (HPS) published annual surveillance reports for laboratory-confirmed cases of:

  • Cryptosporidium – In 2018, HPS received 536 laboratory reports of Cryptosporidium. This represents an increase of 27 reports (5.3%) when compared with 2017 (509 reports), but is within the year-on-year variation observed in Cryptosporidium as reported in the previous ten years.
  • Giardia – In 2018, HPS received 199 laboratory reports of Giardia, which represents a decrease of 70 reports (26.0%) when compared with 2017 (269 reports).
  • Cyclospora – A total of 12 laboratory reports of Cyclospora were received by HPS in 2018, compared with 46 in 2017, 167 in 2016, 24 in 2015 and two in 2014.

Korea – KCDC pegs salted clam as culprit behind Hepatitis A rise

Korea Biomed

The Korea Centers for Disease Control and Prevention (KCDC) said that it has confirmed that contaminated fermented shellfish was the main culprit behind the hepatitis A outbreak this summer.

The KCDC came to the conclusions after conducting an in-depth epidemiological investigation.

The agency randomly sampled 270 of the 2,178 hepatitis A patients, diagnosed between July 28 and August 24, and surveyed whether they consumed fermented shellfish this summer. It found that 42 percent of the patients had eaten fermented shellfish during the incubation period.

KCDC also found that 80.7 percent of the 26 patients diagnosed with hepatitis A in August also ate fermented shellfish, while discovering Hepatitis A virus genes in 11 batches out of the 18 batches collected after the outbreak.

Research – Modelling the interaction of the sakacin-producing Lactobacillus sakei CTC494 and Listeria monocytogenes in filleted gilthead sea bream (Sparus aurata) under modified atmosphere packaging at isothermal and non-isothermal conditions

Science Direct


L. sakei CTC494 inhibited L. monocytogenes growth in sea bream fillets during chilled and moderate abuse temperature storage.

L. sakei CTC494 did not increase deterioration of filleted sea bream at an initial level of ≤4 log cfu/g.

L. sakei CTC494 showed potential as bioprotective culture for fish products.

An approach from broth to food was developed for modelling microbial interaction.

Models simulated the bioprotective effect of L. sakei CTC494 on L. monocytogenes in sea bream.


The objective of this work was to quantitatively evaluate the effect of Lactobacillussakei CTC494 (sakacin-producing bioprotective strain) against Listeria monocytogenesin fish juice and to apply and validate three microbial interaction models (Jameson, modified Jameson and Lotka Volterra models) through challenge tests with gilthead sea bream (Sparus aurata) fillets under modified atmosphere packaging stored at isothermal and non-isothermal conditions. L. sakei CTC494 inhibited L. monocytogenes growth when simultaneously present in the matrix (fish juice and fish fillets) at different inoculation ratios pathogen:bioprotector (i.e. 1:1, 1:2 and 1:3). The higher the inoculation ratio, the stronger the inhibition of L. monocytogenes growth, with the ratio 1:3 yielding no growth of the pathogen. The maximum population density (Nmax) was the most affected parameter for L. monocytogenes at all inoculation ratios. According to the microbiological and sensory analysis outcomes, an initial inoculation level of 4 log cfu/g for L. sakei CTC494 would be a suitable bioprotective strategy without compromising the sensory quality of the fish product. The performance of the tested interaction models was evaluated using the Acceptable Simulation Zone approach. The Lotka Volterra model showed slightly better fit than the Jameson-based models with 75–92% out of the observed counts falling into the Acceptable Simulation Zone, indicating a satisfactory model performance. The evaluated interaction models could be used as predictive modelling tool to simulate the simultaneous behaviour of bacteriocin-producing Lactobacillus strains and L. monocytogenes; thus, supporting the design and optimization of bioprotective culture-based strategies against L. monocytogenes in minimally processed fish products.

Research – Inactivation of Salmonella, Listeria monocytogenes and Enterococcus faecium NRRL B-2354 in a selection of low moisture foods

Science Direct


Pathogens or surrogate survived well in samples during storage (21 days at 16 °C).

Heat resistance did not change significantly throughout the storage period.

Viability of pathogens or surrogate was adequate for inactivation/validation studies.

E. faecium NRRL B2354 was a suitable surrogate in tested products except confectionery.

Pathogens were inactivated by heating to 112 °C solid foods in sealed thermal cells.


The aims of this study were to obtain data on survival and heat resistance of cocktails of SalmonellaListeria monocytogenes and the surrogate Enterococcus faecium(NRRL B-2354) in four low moisture foods (confectionery formulation, chicken meat powder, pet food and savoury seasoning) during storage before processing. Inoculated samples were stored at 16 °C and cell viability examined at day 0, 3, 7 and 21. At each time point, the heat resistance at 80 °C was determined. The purpose was to determine a suitable storage time of inoculated foods that can be applied in heat resistance studies or process validations with similar cell viability and heat resistance characteristics. The main inactivation study was carried out within 7 days after inoculation, the heat resistance of each bacterial cocktail was evaluated in each low moisture food heated in thermal cells exposed to temperatures between 70 and 140 °C. The Weibull model and the first order kinetics (D-value) were used to express inactivation data and calculate the heating time to achieve 5 log reduction at each temperature.

Results showed that the pathogens Salmonella and Lmonocytogenes and the surrogate E. faecium NRRL B-2354, can survive well (maximum reduction < 0.8 log) in low moisture foods maintained at 16 °C, as simulation of warehouse raw material storage in winter and before processing. The D80 value of the pathogens and surrogate did not significantly change during the 21 day storage (p > 0.05). The inactivation kinetics of the pathogens and surrogate at temperatures between 70 and 140 °C, were different between each organism and product. E. faecium NRRL B-2354 was a suitable Salmonella surrogate for three of the low moisture foods studied, but not for the sugar-containing confectionery formulation. Heating low moisture food in moisture-tight environments (thermal cells) to 111.2, 105.3 or 111.8 °C can inactivate 5 log of SalmonellaL. monocytogenes or E. faecium NRRL B-2354 respectively.

Research – Comparison of pH effects on ohmic heating and conventional heating for inactivation of Escherichia coli O157:H7, Salmonella enterica Serovar Typhimurium and Listeria monocytogenes in orange juice

Science Direct


Effect of pH on ohmic heating compared to conventional heating was investigated.

Adjusting pH has significant effect on the heating rate of ohmic heating.

Unusual tendency of pathogen inactivation was identified in ohmic heating.

Quality aspects of samples were not severely degraded regardless of pH.


The objective of the current study is to identify the influence of acidity on ohmic heating compared to conventional heating for inactivation of food-borne pathogensin orange juice. For conventional heating, the heating rate was not significantly different (P > 0.05) regardless of pH and pathogens were inactivated more effectively at lower pH. However, different patterns were observed for ohmic heating. Although temperature and electrical conductivity were not greatly affected by lowering pH, temperature increased more rapidly with increasing pH due to higher electrical conductivity. Also, the inactivation patterns were significantly different (P < 0.05) from conventional heating. While Salmonella Typhimurium was inactivated most rapidly at pH 2.5, Escherichia coli O157:H7 and Listeria monocytogenes were inactivated most rapidly at pH 4.5. When pathogens were exposed to each heating method at a fixed temperature, additional effects of ohmic heating were not observed. Also, the overall quality of orange juice subjected to ohmic heating was not greatly affected at any pH level. Therefore, increasing as well as lowering pH can also be considered effective ways to optimize pasteurization of orange juice when using ohmic heating. The different characteristics of ohmic heating compared to conventional heating indicate the necessity of a new approach.

Research – Antibiotic resistant phenotypes of Staphylococcus aureus isolated from fresh and fermented milk in parts of Nasarawa State, Nigeria

Academic Journals


This work was aimed at determining the occurrence and antibiogram of Staphylococcus aureusisolated from fresh and fermented milk samples in parts of Nasarawa State, Nigeria. A total of 180 samples comprising of fresh raw milk, bulk milk, nono, and kindirmo were collected over a period of 6 months (May to October, 2017). Standard microbiological procedures were employed in the isolation, identification, characterisation, and determination of the antibiogram of S. aureus from the milk samples. Characterisation of the S. aureus isolates was by morphological, biochemical characteristics using conventional methods, Microgen® STAPH-ID kits. Confirmed isolates were tested for susceptibility or resistance to a panel of 11 commonly used antibiotics using the agar disc diffusion technique. Out of the 180 milk samples examined, 9 S. aureus were isolated giving a prevalence of 5.0%. The occurrence of S. aureus was higher in nono (12.1%) and kindirmo (10.6%) than in fresh raw milk (5.9%). The high occurrence of S. aureus in nono disproved the assertion that fermented foods are not good media for the survival and growth of S. aureus. The antibiotic susceptibility profile of the S. aureus isolates indicated all of the nine isolates were completely resistant to cefoxitin, ampicillin, and amoxicillin/clavulanic acid. The isolates were moderately resistant to erythromycin (22.2%), sulphamethoxazole/trimethoprim (22.2%), and tetracycline (44.4%). Five antibiotic resistance patterns were recorded among the isolates. All of the isolates had a multiple antibiotics resistance (MAR) index of 0.3 and above, an indication of possible antibiotic misuse in the areas studied.