Category Archives: microbial contamination

Research- Effect of cultivars and irrigation waters on persistence of indicator bacteria on lettuce grown in high tunnel

Wiley Online


Effect of irrigation with groundwater (GW), primary‐treated wastewater (PTWW), secondary‐treated wastewater (STWW), and roof‐collected rainwater (RCR) on the microbial quality of lettuce cultivars “Annapolis,” “Celinet,” and “Coastline” grown in high tunnel was investigated. Lettuce plants were spray irrigated with irrigation waters once a week for 2 weeks and analyzed for indicator and pathogenic bacteria. PTWW irrigation resulted in the highest Escherichia coli recovery on the lettuce plants (4.7 log MPN/g) as compared to irrigation with other three waters on 0 day post irrigation (dpi). Lettuce cultivars affected the bacterial die‐off rate, where E. coli populations reduced the most by 1.5 log MPN/g on “Annapolis” lettuce on 2 dpi. The STWW and RCR irrigation did not significantly influence indicator bacterial populations on lettuce as compared to GW irrigation. The STWW and RCR containing low populations of indicator bacteria may be suitable for lettuce irrigation in Mid‐Atlantic area without affecting its microbial quality.

Research – Salmonella enterica Elicits and Is Restricted by Nitric Oxide and Reactive Oxygen Species on Tomato

Frontiers in Microbiology

The enteric pathogen Salmonella enterica can interact with parts of the plant immune system despite not being a phytopathogen. Previous transcriptomic profiling of S. enterica associating with tomato suggested that Salmonella was responding to oxidative and nitrosative stress in the plant niche. We aimed to investigate whether Salmonella was eliciting generation of reactive oxygen species (ROS) and nitric oxide (NO), two components of the microbe-associated molecular pattern (MAMP)-triggered immunity (MTI) of plants. We also sought to determine whether this interaction had any measurable effects on Salmonella colonization of plants. Biochemical, gene expression and on-plant challenge assays of tomato vegetative and fruit organs were conducted to assess the elicitation of ROS and NO in response to Salmonella Newport association. The counter bacterial response and the effect of NO and ROS on Salmonella colonization was also investigated. We detected H2O2 in leaves and fruit following challenge with live S. Newport (p < 0.05). Conversely, NO was detected on leaves but not on fruit in response to S. Newport (p < 0.05). We found no evidence of plant defense attenuation by live S. Newport. Bacterial gene expression of S. Newport associating with leaves and fruit were indicative of adaptation to biotic stress in the plant niche. The nitrosative stress response genes hmpA and yoaG were significantly up-regulated in S. Newport on leaves and fruit tissue compared to tissue scavenged of NO or ROS (p < 0.05). Chemical modulation of these molecules in the plant had a restrictive effect on bacterial populations. Significantly higher S. Newport titers were retrieved from H2O2 scavenged leaves and fruit surfaces compared to controls (p < 0.05). Similarly, S. Newport counts recovered from NO-scavenged leaves, but not fruit, were higher compared to control (p < 0.05), and significantly lower on leaves pre-elicited to produce endogenous NO. We present evidence of Salmonella elicitation of ROS and NO in tomato, which appear to have a restricting effect on the pathogen. Moreover, bacterial recognition of ROS and NO stress was detected. This work shows that tomato has mechanisms to restrict Salmonella populations and ROS and NO detoxification may play an important role in Salmonella adaptation to the plant niche.

Research – Burying or burning garbage boosts airborne bacteria, antibiotic resistance genes

Science Daily

Municipal solid waste is trash — such as plastic, food scraps and lawn clippings — that goes into garbage bins and doesn’t get recycled. Most of this waste is buried in landfills or is incinerated. Now, researchers reporting in ACS’ Environmental Science & Technology have shown that when disposed of in this way, municipal solid waste can be an important source of antibiotic-resistance genes in the air.

Residual antibiotics from discarded medications and other products can end up in municipal solid waste. Some microbes in the garbage are resistant to those antibiotics, and they can spread resistance genes to other bacteria, allowing them to survive in the presence of these drugs. But scientists hadn’t studied whether treating the garbage through incineration or landfilling releases these bacteria and genes into the air, where people or animals could breathe them in. So Yi Luo, Xiangdong Li and colleagues wanted to investigate the bacterial community and associated antibiotic-resistance genes in the municipal solid waste treatment system of Changzhou, a city in eastern China.


Research – Root Cause Analyses Are ‘Critical to Preventing Foodborne Illnesses’

PEW Trusts

When foodborne illnesses are linked to products regulated by the Food and Drug Administration, the agency’s top priority is limiting harm to consumers with swift removal of unsafe items from the market. But FDA’s work doesn’t end there. The agency increasingly uses an investigative approach called root cause analysis (RCA) to identify how and why dangerous bacteria or other pathogens contaminated specific products and what steps could help businesses prevent a recurrence of these problems. The FDA publicly shares findings and recommended corrective actions from each RCA so that food growers and manufacturers across an industry can apply them to their food safety systems.

Frank Yiannas, deputy commissioner for food policy and response, heads FDA’s efforts to reduce food contamination risks and respond to foodborne outbreaks. He spoke with The Pew Charitable Trusts about the importance of RCA in this work and cited a new Pew report that offers guidance for effective analyses to food companies and government agencies. His responses have been edited for clarity and length.

Research – Scale‐up model of forced air‐integrated gaseous chlorine dioxide for the decontamination of lowbush blueberries

Wiley Online 

Gaseous chlorine dioxide (ClO2) is a promising sanitizer for frozen products because of its efficacy under nonthermal and waterless conditions. A major knowledge gap exists between laboratory trials and effectiveness at the industrial scale. To address this, a pilot study implementing a pallet‐sized fumigation container (60 harvest totes) was designed for gaseous ClO2. Fifty kilograms of blueberries were exposed to initial dose of 57.46 mg/L, representing a treatment of 2.35 mg/g of blueberries. Blueberries remained enclosed for 10 hr. Reduction of all viable cells, coliforms, yeasts, and molds were measured by plating treated samples on Tryptic Soy Agar, Violet Red Bile Agar, and Dichloran Rose Bengal Chloramphenicol Agar and compared to untreated controls. The results demonstrate that a significant reduction of 1.5 log CFU/g can be achieved against coliforms after ClO2 exposure. Our findings demonstrate a cost‐effective procedure that could be adapted to commercial processing.

RASFF Alerts – Animal Feed – Aflatoxins – Groundnuts – Peanuts – Crushed Peanut Kernels


RASFF – aflatoxins (B1 = 46 µg/kg – ppb) in groundnuts for birdfeed from Argentina in the Netherlands

RASFF – aflatoxins (B1 = 81 µg/kg – ppb) in peanuts from India than the Netherlands

RASFF – aflatoxins (B1 = 34.3 µg/kg – ppb) in crushed peanut kernels from Argentina in Germany

RASFF Alerts – Animal Feed -Salmonella – Toasted Soymeal for Pigs


RASFF – Salmonella enterica ser. Mbandaka (presence /25g) in toasted soymeal used in several types of compound feeds for pigs from Belgium in Belgium