Category Archives: Food Microbiology Research

USA- Romaine in the cross-hairs – FDA to test lettuce for pathogens

Food Poison Journal

The FDA is conducting a small, focused assignment to collect samples of raw agricultural commodity (RAC) romaine lettuce to test for Salmonella spp. and pathogenic Escherichia coli (also known as Shiga Toxin-producing E. coli or STEC), microbial hazards repeatedly linked to foodborne illnesses associated with romaine lettuce consumption. The assignment begins this month (November 2019) and is expected to last one year.

Research -First report of Escherichia coli O157:H7 in ready-to-eat sushi.

Europe PMC

AIMS:The aim of this study was to evaluate the microbiological quality of commercially prepared ready-to-eat (RTE) sushi by enumerating aerobic mesophilic bacteria (AMB) and thermotolerant coliforms (TC) and detecting Escherichia coli and Salmonella ssp. An isolate was identified as E. coli O157:H7 which was evaluated for its virulence and antimicrobial resistance profiling as well as its ability to form biofilms on stainless steel. METHODS AND RESULTS:There were four sampling events in seven establishments, totalling 28 pools of sushi samples. Mean AMB counts ranged between 5·2 and 7·7 log CFU per gram. The enumeration of TC varied between 2·1 and 2·7 log MPN per gram. Salmonella ssp. were not detected, and one sample was positive for E. coli and was identified as E. coli O157:H7. To the best of our knowledge, this is the first report of E. coli O157:H7 in sushi samples in the world literature. This isolate presented virulence genes stx1, stx2, eae and hlyA. It was also susceptible to 14 antimicrobials tested and had the ability to form biofilms on stainless steel. CONCLUSIONS:There is a need to improve the good hygiene practices adopted in establishments selling sushi in the city of Pelotas, Brazil. In addition, the isolated E. coli O157:H7 carries a range of important virulence genes being a potential risk to consumer health, as sushi is a RTE food. This isolate also presents biofilm formation ability, therefore, may trigger a constant source of contamination in the production line of this food. SIGNIFICANCE AND IMPACT OF THE STUDY:The increase in the consumption of sushi worldwide attracts attention regarding the microbiological point of view, since it is a ready-to-eat food. To our knowledge, this was the first time that E. coli O157:H7 was identified in sushi samples.

Singapore -Eating raw pig liver from local market may raise chances of contracting Hepatitis E virus liver disease


Do you like to eat raw liver? Is liver pâté one of your favorite dishes? You may want to think twice before ingesting such a meal again, as researchers at the Singapore General Hospital have found definite similarities between the virus strains of Hepatitis E virus or (HEV) in pig liver and human liver.


Research – Decontamination of Bacillus cereus in cardamom (Elettaria cardamomum) seeds by infrared radiation and modeling of microbial inactivation through experimental models

Wiley Online 

In this work, infrared (IR) irradiation was used for inactivation of Bacillus cereus in cardamom seeds. The effect of IR power (100, 200, and 300 W), sample distance from radiation source (5, 10, and 15 cm) and holding times (0–11 min) was investigated on B. cereus count, as well as cardamom seeds color and temperature profiles. Inactivation of B. cereus on cardamom seeds during IR processing was demonstrated by experimental models. The highest reduction of B. cereus count (5.11 Log CFU/g) was achieved after 8 min IR irradiation at 300 W power and 15 cm distance. Measurement of temperature profiles revealed that there was a significant difference (p < .05) between surface and center temperatures of the cardamom seeds. The green color (a* value) of cardamom seeds was slightly affected and the highest color change was observed at 200 W IR, 10 cm distance and 10 min irradiation that resulted in an increase of a* from −3.05 ± 0.96 to −0.05 ± 0.44. In conclusion, IR irradiation could be successful for decontamination of cardamom seeds without severe alteration of its quality. Among the experimental models for microbial inactivation during IR processing, the Double Weibull model had the highest coefficient value of determination (R2 = 0.9966).

Research -Occurrence of Campylobacter spp., Salmonella spp. and shiga toxin‐producing Escherichia coli in inline milk filters from Swedish dairy farms

Wiley Online


This study investigated the occurrence of shiga toxin‐producing Escherichia coli (STEC), thermotolerant Campylobacter spp. and Salmonella spp. in Swedish dairy milk. A total of 302 inline milk filters were analyzed. Salmonella was not isolated from any filters. Polymerase chain reaction screening detected thermotolerant Campylobacter in 30.5% of the milk filters analyzed and it was isolated from 12.6% of filters. The stx genes (stx 1stx 2, or both) were screened from 71% of the filters and STEC was isolated from 14% of these. Of the STEC isolates, 21 contained the stx 1 gene, 19 the stx 2 gene, and five a combination of both stx 1 and stx 2 genes. Whole genome sequence typing on 34 of the 45 STEC showed that they belonged to 21 different serotypes, of which STEC O145:H28 was the most common (2%). STEC O157:H7 was only found from one (0.3%) of the filters. A combination of stx 2 and eae genes was found from 0.7% of the total number of inline milk filters analyzed, while stx 2a was found in 24% of the whole genome‐sequenced isolates. There was a significant positive correlations between number of animals per farm and presence of pathogens on milk filters.

Research -Radiofrequency pasteurization process for inactivation of Salmonella spp. and Enterococcus faecium NRRL B-2354 on ground black pepper

Science Direct


Salmonella persistence in ground black pepper has caused several foodborne outbreaks and created public concern about the safety of low water activity (aw) foods. In this study, radiofrequency (RF) processing was evaluated for pasteurization of ground black pepper. Stability and homogeneity tests were done for both Salmonella spp. and E. faecium during moisture equilibration before RF heating to evaluate the inoculation method. Moisture content of samples were conditioned such that the final moisture content after RF heating reached the optimal storage moisture. RF heating was shown to provide more than 5.98 log CFU/g reduction for Salmonella spp. and the reduction of 3.89 log CFU/g for E. faecium with a 130 s of treatment time. The higher thermal resistance of E. faecium indicated its suitability as surrogate for Salmonella spp. during RF heating of ground black pepper. Piperine, total phenolics, volatile compounds, and antioxidant activity were assessed as quality parameters for ground black pepper. The results demonstrated that the RF processing provided effective inactivation of Salmonella spp. with insignificant (p > 0.05) quality deterioration.

Research – Searching for high pressure processing parameters for Escherichia coli O157:H7, Salmonella enterica and Listeria monocytogenes reduction in Concord grape juice

Research Gate

Purpose High pressure processing (HPP) has been widely used for high-acid (pH<4.6) juices. The purpose of this study was to investigate optimal parameters aimed at achieving 5-log reduction of the pathogens of reference in Concord grape juice (pH 3.39). Design/methodology/approach Grape juice was inoculated with five strain cocktails of Escherichia coli O157:H7, Salmonella enterica and Listeria monocytogenes . In total, 11 trials were carried out based on a Central Composite Rotational Design (CCRD). The pressure ( P ), ranging from 319 to 531 MPa, and dwell time ( t ), from 35 to 205 s, were tested. The performance of the combinations ( P × t ) was evaluated by pathogen challenge microbiological assays. Findings E. coli O157:H7 was more resistant to HPP than S. enterica . L. monocytogenes did not grow in unprocessed juice (before HPP). Findings demonstrated that moderate pressures (~400 MPa) and short dwell times (~2 min) were effective in achieving a greater than 5-log reduction in the pathogens of reference. Practical implications Because the maintenance costs of equipment exponentially increase with pressure beyond 600 MPa, significant reductions in process pressure are highly desirable. Originality/value The results of this study can supplement the dearth of information on the applicability of high pressure as a Concord grape juice processing technology in terms of the pathogens inactivation. Furthermore, the use of a cocktail of five strains of pathogens inoculated in Concord grape juice to challenge different HPP parameters has not been reported.