Category Archives: Microbiology

Research – Listeria monocytogenes in dairy plants in Southern Brazil: Occurrence, virulence potential, and genetic diversity

Wiley Online

Abstract

Listeria monocytogenes is a foodborne pathogen widely distributed in nature. The aims of this study were to evaluate the occurrence of Listeria spp. in three dairy plants located in Southern Brazil, and to characterize the Lmonocytogenes isolates according to serotypes, virulence genes, and PFGE. A total of 212 samples were collected, and 15 were positive for Listeria spp., of which seven were LmonocytogenesLmonocytogenes isolates harbored all the 11 virulence genes evaluated and belonged to the main virulent serotypes, indicating potential risks of listeriosis for consumers. The PFGE analysis indicated low genetic diversity among the isolates, and the same pulsotypes were detected in a 2‐month period, indicating persistence of Lmonocytogenes.

Practical applications

The study evaluated the occurrence of Listeria spp. in three dairy plants located in Southern Brazil, as well as characterized the L. monocytogenes isolates according to serotypes, virulence genes and PFGE. The presence of Listeria species indicated postprocessing contamination in the dairy plants and threat to public health. Furthermore, the isolates showed a low genetic diversity, since only two pulsotypes were identified, highlighting the strain’s persistence in the processing environment and/or the presence of clones in this region.

Research – Massachusetts General Hospital publishes new Shigella research

Outbreak News Today

The bacterial pathogen Shigella, often spread through contaminated food or water, is a leading cause of mortality in both children and older adults in the developing world. Although scientists have been studying Shigella for decades, no effective vaccine has been developed, and the pathogen has acquired resistance to many antibiotics. The recent discovery of an early adherence step in the infection cycle by researchers at Massachusetts General Hospital (MGH) could provide a new therapeutic target or even a new method for vaccine development.

As it moves through the digestive system, Shigella traverses the small intestine and subsequently infects the large intestine, causing cramping, diarrhea and dehydration in the disease called shigellosis. “We wanted to determine how Shigella makes its first contact with epithelial cells in the early stages of disease development,” says Dr. Christina Faherty, senior author on the study published in mSphere. “Because of certain gene sequence annotations, and the way that Shigella appeared following growth in standard laboratory media, it was believed that Shigella strains do not produce fimbriae or other adherence factors.” Fimbriae are short hair-like fibers that bacterial cells use to adhere to individual epithelial cells to instigate infection.

Research -Anti‐listeria activity and shelf life extension effects of Lactobacillus along with garlic extract in ground beef

Wiley Online

Abstract

The current study investigates the effect of Lactobacillus reuteri and Lactobacillus plantarum combined with water extract of garlic on microbial growth, chemical changes, and sensory attributes in ground beef samples at refrigeration condition (+4°C) up to 12 days of storage. in vitro study revealed that garlic extract combined with L. reuteri or L. plantarum caused 2.13 and 2.57 log reduction in the Listeria monocytogenes count, respectively. Combination of L. plantarum and 1% garlic extract significantly (p < .05) reduced aerobic mesophilic bacteria (1.64 log cycle) and L. monocytogenes (1.44 log cycle) counts in ground beef. Lipid oxidation was also significantly (p < .05) lower in samples treated with L. plantarum plus garlic extract (1%). Furthermore, higher sensory scores were received by samples treated with Lactobacillus plus garlic extract. In conclusion, the combination of L. plantarum and garlic extract was found to be suitable to use in ground beef by controlling the L. monocytogenes growth and increasing its shelf life.

Practical Applications

Garlic extract not only has an antimicrobial activity but also has a stimulatory effect on the Lactobacillus spp. growth. On the other hand, some Lactobacillus strains can inhibit pathogenic bacteria. Then, the combination of Lactobacillus and garlic extract may be used to produce new bio‐preserved and functional meat products. The current study indicated the potential of Lactobacillus combined with garlic extract to control microbial and chemical changes in ground beef. The combination of Lactobacillus plantarum and garlic extract significantly (p < .05) reduced Listeria monocytogenes counts and lipid oxidation rates and improved the sensory scores in ground beef.

Research – Determination of the effect of ethyl pyruvate on the surface contamination of sausage to Listeria monocytogenes by using Q‐PCR assay

Wiley Online

Abstract

In this study, we examined the effect of ethyl pyruvate on the efficacy of the inactivation of Listeria monocytogenes on the surface of sausage samples by using quantitative PCR (Q‐PCR). Propidium monoazide (PMA) was used for direct quantification of viable and dead cells. The samples inoculated with L. monocytogenes (~3 to 4 log CFU/mL) and uninoculated samples were treated with 0, 42, 105, and 420 mg/L vaporized ethyl pyruvate (EP) in 1 L volume containers. Sausage samples were tested on Days 0, 7, 14, 21, and 28 with regards to changes in microbial, physicochemical, and quality characteristics. As compared with control samples (EP no‐applied), 105 and 420 mg/L concentration of vaporized EP applications were provided 1 and 2 log reduction, respectively. The vaporized EP application was considered to be an alternative preservation method for the modified atmosphere and vacuum packaging and could be easily applied, especially in meat products such as sausages.

Practical application

EP could be used for successful preservation of meat and meat products.

Research – Evaluation of Bactericidal Effects of Phenyllactic Acid on Escherichia coli O157:H7 and Salmonella Typhimurium on Beef Meat

Journal of Food Protection

ABSTRACT

Bactericidal effects of various concentrations of phenyllactic acid on Shiga toxin–producing Escherichia coli (STEC), including E. coli O157:H7, O26:H11, O103:H2, and O121:H19, and on Salmonella Typhimurium DT104 in pure culture and microplates assays were studied. Beef cuts were surface sprayed with phenyllactic acid or lactic acid for inactivation of E. coli O157:H7 and Salmonella Typhimurium. The 1.5% phenyllactic acid inactivated all inoculated E. coli O157:H7, O26:H11, O103:H2, and O121:H19 and Salmonella Typhimurium DT104 (>6-log reduction) within 1 min of contact at 21°C, whereas 1.5% lactic acid did not result in microbial reduction. Microplate assays (for STEC and Salmonella Typhimurium DT104 at 10 to 100 CFU per well) indicated that concentrations of 0.25% phenyllactic acid or 0.25% lactic acid inhibited the growth of STEC and Salmonella Typhimurium DT104 incubated at 37°C for 24 h. Treatment of beef with 1.5% lactic acid or 1.5% phenyllactic acid reduced E. coli O157:H7 by 0.22 and 0.38 log CFU/cm2, respectively, within 5 min and reduced Salmonella Typhimurium DT104 by 0.12 and 0.86 log CFU/cm2, respectively. When meat treated with 1.5% phenyllactic acid was frozen at −20°C, inactivation of E. coli O157 and Salmonella Typhimurium DT104 was enhanced by 1.06 and 1.46 log CFU/cm2, respectively. Thus, treatment of beef with 1.5% phenyllactic acid significantly reduced the population of E. coli O157:H7 and Salmonella.

HIGHLIGHTS
  • Phenyllactic acid at 1.5% killed STEC and Salmonella (>6-log reduction) within 1 min.

  • The MIC of lactic and phenyllactic acids was 0.25%.

  • The bactericidal effect of phenyllactic acid on beef was enhanced by freezing.

Research – Salmonella Survival in Soil and Transfer onto Produce via Splash Events

Journal of Food Protection

ABSTRACT

Nearly one-half of foodborne illnesses in the United States can be attributed to fresh produce consumption. The preharvest stage of production presents a critical opportunity to prevent produce contamination in the field from contaminating postharvest operations and exposing consumers to foodborne pathogens. One produce-contamination route that is not often explored is the transfer of pathogens in the soil to edible portions of crops via splash water. We report here on the results from multiple field and microcosm experiments examining the potential for Salmonella contamination of produce crops via splash water, and the effect of soil moisture content on Salmonella survival in soil and concentration in splash water. In field and microcosm experiments, we detected Salmonella for up to 8 to 10 days after inoculation in soil and on produce. Salmonella and suspended solids were detected in splash water at heights of up to 80 cm from the soil surface. Soil-moisture conditions before the splash event influenced the detection of Salmonella on crops after the splash events—Salmonella concentrations on produce after rainfall were significantly higher in wet plots than in dry plots (geometric mean difference = 0.43 CFU/g; P = 0.03). Similarly, concentrations of Salmonella in splash water in wet plots trended higher than concentrations from dry plots (geometric mean difference = 0.67 CFU/100 mL; P = 0.04). These results indicate that splash transfer of Salmonella from soil onto crops can occur and that antecedent soil-moisture content may mediate the efficiency of microbial transfer. Splash transfer of Salmonella may, therefore, pose a hazard to produce safety. The potential for the risk of splash should be further explored in agricultural regions in which Salmonella and other pathogens are present in soil. These results will help inform the assessment of produce safety risk and the development of management practices for the mitigation of produce contamination.

HIGHLIGHTS
  • Salmonella was detected for 8 to 10 days after inoculation in soil and on produce.

  • Salmonella in soil can be detected in splash water from rainfall/irrigation events.

  • Salmonella was detected in splash water at heights of up to 80 cm.

  • Soil moisture conditions may affect the transfer potential of Salmonella.

Sweden – Sweden -Cryptosporidium outbreak tops 300 cases since October

Outbreak News Today crypt

In a follow-up on a previous report on the Cryptosporidium outbreak in Sweden, the Public Health Authority, or Folkhalsomyndigheten, report more than 300 cases of cryptosporidiosis in October and November.

The good news is while the number of cases are still unusually high, the number of reported cases has decreased.

 

Research – Overview of Listeriosis in the Southern African Hemisphere—Review

Wiley Online

Listeriosis is rarely reported in the Southern African Hemispheres in spite of the increasing rate of Listeria in several foodborne outbreaks reported in advanced countries. This paper reviews the emerging trends in the spread, distribution, and epidemiology of Listeria species in foods, water, human, animals, and different environments in Southern Africa based on the appraisal of scholarly articles. In this regard, information obtained from literatures from various online databases revealed that Listeria species are commonly recovered from food, water, and human samples. Fewer articles provided information on Listeria recovered from animals (ruminants) and soil samples. Generally, reports of studies were more focused on Listeria monocytogenes among other Listeria species. To this end, reports obtained from literature on the method of identification of Listeria were mostly based on serological, classical biochemical methods and the principle of aesculin hydrolysis, usually characterized by black coloration on selective media for Listeria. These methods may not be reliable, as they could sometimes give a false positive report. Therefore, molecular methods are more reliable, accurate, could show the genetic relationship between isolates, and at the same time capable of enabling tracking the source of this pathogen should be embraced as a better substitute for the identification of Listeria in Southern African sub‐region.

Research – Bacterial contamination and prevalence of antimicrobial resistance phenotypes in raw fruits and vegetables sold in Delhi, India

Wiley Online

Fresh fruits and vegetables contaminated with microbial pathogens can cause outbreaks of food poisoning and other enteric diseases if consumed raw. The objective of the present study was to determine the bacterial contamination and antibiotic resistance in fresh produce sold in Delhi, India. One hundred fifty samples of fruits and vegetables generally consumed raw were collected from retail and wholesale vendors of Delhi‐NCR, India. Microbial contamination was studied by culturing 25 g of each sample. Antimicrobial resistance testing was performed for isolated pathogens and resistance phenotypes determined. Overall, 97.3% of fruit and vegetables sampled were contaminated with pathogens. In over 75% of samples, coliforms were detected with Escherichia coli in 17.4%. Majority of vegetables were contaminated with coliforms particularly ginger (100%), cabbage (80%), cucumber (75%), and tomato (75%). Extended spectrum beta‐lactamases (ESBL) was detected in eight (5.7%) isolates, carbapenem resistance in four with three metallo‐β‐lactamases producers. E. coli was isolated at a significantly higher rate from retail shops viz‐a‐viz wholesale markets (p value = .04). As high level of contamination with potential human pathogens is present in fruits and vegetables sold in wholesale markets and retail shops in Delhi‐NCR, the study underlines the need for stricter regulations and implementation of standards.

Research -Shiga toxin-producing Escherichia coli survives storage in wheat flour for two years

Science Direct

Abstract

Wheat flour has recently been recognised as an exposure vehicle for the foodborne pathogen Shiga toxin-producing Escherichia coli (STEC). Wheat flour milled on two sequential production days in October 2016, and implicated in a Canada wide outbreak of STEC O121:H19, was analysed for the presence of STEC in November 2018. Stored in sealed containers at ambient temperature, the water activity of individual flour samples was below 0.5 at 6 months post-milling and remained static or decreased slightly in individual samples during 18 months of additional storage. STEC O121 was isolated, with the same genotype (stx2aeaehlyA) and core genome multilocus sequence type as previous flour and clinical isolates associated with the outbreak. The result of this analysis demonstrates the potential for STEC to persist in wheat flour at levels associated with outbreak infections for periods of up to two years. This has implications for the potential for STEC to survive in other foods with low water activity.