Caliciviruses: A Major Cause of Foodborne Illness

Porcine Sapovirus in Northern Vietnam: Genetic Detection and Characterization Reveals Co-Circulation of Multiple Genotypes

Porcine sapovirus (PoSaV) has been reported in many countries over the world, which may cause gastroenteritis symptoms in pigs with all ages. There has been no report on PoSaV infection in Vietnam up to now. In this study, a total of 102 samples were collected from piglets, fattening pigs, and sows with diarrhea in several cities and provinces in northern Vietnam. The PoSaV genome was examined using polymerase chain reaction (PCR). Sequencing of the partial RNA-dependent RNA polymerase (RdRp) gene sequences (324 bp) was performed. Of the 102 tested samples, 10 (9.8%) and 7/20 (35%) were detected as positive for the PoSaV RdRp gene using the PCR method at the individual and farm levels, respectively. Genetic analysis of the partial RdRp gene region of about 324 bp indicated that the nucleotide identity of the current 10 Vietnamese viral strains ranged from 61.39% to 100%. Among the 10 strains obtained, 8 belonged to genotype III and the remaining 2 strains were clustered in genotype VIII. The Vietnamese genotype III viruses formed two sub-clusters. The Vietnamese PoSaV strains were closely related to PoSaVs reported in South Korea, Venezuela, and the Netherlands. This research was the first to describe PoSaV infection in northern Vietnam during 2022-2023.

Environmentally Transmitted Pathogens

This chapter describes a variety of pathogens found in the environment that are capable of infecting humans and causing disease. Different classes of pathogens are discussed including bacteria, parasites and viruses. For each pathogen, data are provided on the incidence of the organism in a particular environmental matrix such as water, food or municipal waste. In addition, we discuss: the disease caused by the particular microbe; the mode of transmission; the incubation time needed within the host prior to the onset of disease; and the duration of illness. Fate and transport of pathogens in the environment are also described. A variety of bacterial pathogens are discussed including waterborne and waterbased bacteria. Parasites discussed include protozoa, nematodes, cestodes and trematodes. For viruses, both enteric and respiratory viruses are included.

Quaternary ammonium biocides: efficacy in application

Quaternary ammonium compounds (QACs) are among the most commonly used disinfectants. There has been concern that their widespread use will lead to the development of resistant organisms, and it has been suggested that limits should be place on their use. While increases in tolerance to QACs have been observed, there is no clear evidence to support the development of resistance to QACs. Since efflux pumps are believe to account for at least some of the increased tolerance found in bacteria, there has been concern that this will enhance the resistance of bacteria to certain antibiotics. QACs are membrane-active agents interacting with the cytoplasmic membrane of bacteria and lipids of viruses. The wide variety of chemical structures possible has seen an evolution in their effectiveness and expansion of applications over the last century, including non-lipid-containing viruses (i.e., noroviruses). Selection of formulations and methods of application have been shown to affect the efficacy of QACs. While numerous laboratory studies on the efficacy of QACs are available, relatively few studies have been conducted to assess their efficacy in practice. Better standardized tests for assessing and defining the differences between increases in tolerance versus resistance are needed. The ecological dynamics of microbial communities where QACs are a main line of defense against exposure to pathogens need to be better understood in terms of sublethal doses and antibiotic resistance.

Sources of microbial pathogens in municipal solid waste landfills in the United States of America

Municipal solid waste (MSW) categories, as specified by United States Environmental Protection Agency (US EPA), were evaluated for their relative contribution of pathogenic viruses, bacteria, and protozoan parasites into MSW landfills from 1960 to 2007. The purpose of this study was to identify trends and quantify the potential contribution of pathogens in MSW as an aid to the assessment of potential public health risks. A review of the literature was conducted to estimate values for the concentrations of faecal indicator bacteria and pathogens in the major categories of MSW. The major sources of MSW contributing enteric pathogens were food waste, pet faeces, absorbent products, and biosolids. During the last 47 years, recycling of glass, metals, plastic, paper and some organic wastes in MSW has increased, resulting in a decreased proportion of these materials in the total landfilled MSW. The relative proportion of remaining waste materials has increased; several of these waste categories contain pathogens. For all potential sources, food waste contributes the greatest number of faecal coliforms (80.62%). The largest contribution of salmonellae (97.27%), human enteroviruses (94.88%) and protozoan parasites (97%) are expected to come from pet faeces. Biosolids from wastewater treatment sludge contribute the greatest number of human noroviruses (99.94%). By comparison, absorbent hygiene products do not appear to contribute significantly to overall pathogen loading for any group of pathogens. This is largely due to the relatively low volume of these pathogen sources in MSW, compared, for example, with food waste at almost 40% of total MSW.

Electron-beam inactivation of a norovirus surrogate in fresh produce and model systems

Norovirus remains the leading cause of foodborne illness, but there is no effective intervention to eliminate viral contaminants in fresh produce. Murine norovirus 1 (MNV-1) was inoculated in either 100 ml of liquid or 100 g of food. The inactivation of MNV-1 by electron-beam (e-beam), or high-energy electrons, at varying doses was measured in model systems (phosphate-buffered saline [PBS], Dulbecco's modified Eagle's medium [DMEM]) or from fresh foods (shredded cabbage, diced strawberries). E-beam was applied at a current of 1.5 mA, with doses of 0, 2, 4, 6, 8, 10, and 12 kGy. The surviving viral titer was determined by plaque assays in RAW 264.7 cells. In PBS and DMEM, e-beam at 0 and 2 kGy provided less than a 1-log reduction of virus. At doses of 4, 6, 8, 10, and 12 kGy, viral inactivation in PBS ranged from 2.37 to 6.40 log, while in DMEM inactivation ranged from 1.40 to 3.59 log. Irradiation of inoculated cabbage showed up to a 1-log reduction at 4 kGy, and less than a 3-log reduction at 12 kGy. On strawberries, less than a 1-log reduction occurred at doses up to 6 kGy, with a maximum reduction of 2.21 log at 12 kGy. These results suggest that a food matrix might provide increased survival for viruses. In foods, noroviruses are difficult to inactivate because of the protective effect of the food matrix, their small sizes, and their highly stable viral capsid.

Reduction in infection risk through treatment of microbially contaminated surfaces with a novel, portable, saturated steam vapor disinfection system

BACKGROUND

Surface-mediated infectious disease transmission is a major concern in various settings, including schools, hospitals, and food-processing facilities. Chemical disinfectants are frequently used to reduce contamination, but many pose significant risks to humans, surfaces, and the environment, and all must be properly applied in strict accordance with label instructions to be effective. This study set out to determine the capability of a novel chemical-free, saturated steam vapor disinfection system to kill microorganisms, reduce surface-mediated infection risks, and serve as an alternative to chemical disinfectants.

METHODS

High concentrations of Escherichia coli, Shigella flexneri, vancomycin-resistant Enterococcus faecalis (VRE), methicillin-resistant Staphylococcus aureus (MRSA), Salmonella enterica, methicillin-sensitive Staphylococcus aureus, MS2 coliphage (used as a surrogate for nonenveloped viruses including norovirus), Candida albicans, Aspergillus niger, and the endospores of Clostridium difficile were dried individually onto porous clay test surfaces. Surfaces were treated with the saturated steam vapor disinfection system for brief periods and then numbers of surviving microorganisms were determined. Infection risks were calculated from the kill-time data using microbial dose-response relationships published in the scientific literature, accounting for surface-to-hand and hand-to-mouth transfer efficiencies.

RESULTS

A diverse assortment of pathogenic microorganisms was rapidly killed by the steam disinfection system; all of the pathogens tested were completely inactivated within 5 seconds. Risks of infection from the contaminated surfaces decreased rapidly with increasing periods of treatment by the saturated steam vapor disinfection system.

CONCLUSIONS

The saturated steam vapor disinfection system tested for this study is chemical-free, broadly active, rapidly efficacious, and therefore represents a novel alternative to liquid chemical disinfectants.

Environmentally Transmitted Pathogens

Pathogenic microorganisms usually originate from an infected host or directly from the environment; however, only a small proportion of these microbes cause infection. This chapter discusses the pathogens that are transmitted through the environment such as bacteria, viruses, and protozoa. Many human pathogens can be transmitted only by direct or close contact with an infected person or animal such as herpesvirus. Virus transmission by the airborne route may be both direct and indirect inhalation of infectious droplets or through contact with contaminated fomites. Water-borne diseases—such as yellow fever, dengue, filariasis, malaria, onchocerciasis, and sleeping sicknessare transmitted by insects that breed in water or live near water. The common bacterial pathogens transmitted through water include Salmonella, Escherichia coli, Shigella, Campylobacter, Yersinia, Vibrio, Helicobacter, and Legionella. Opportunistic pathogens are also numerous in the environment, and the most important opportunistic pathogen is Pseudomonas aeruginosa. Viruses are a leading cause of gastroenteritis and water-borne outbreaks may be caused by norovirus, hepatitis A virus, Coxsackie virus, echovirus, and adenoviruses. Respiratory diseases are also associated with a large number of viruses such as rhinoviruses, coronaviruses, parainfluenza viruses, respiratory syncytial virus (RSV), influenza virus, and adenovirus. Generally, viral and protozoan pathogens survive longer in the environment than enteric bacterial pathogens.

Estimating the under-reporting rate for infectious gastrointestinal illness in Ontario

BACKGROUND

In Ontario, infectious gastrointestinal illness (IGI) reporting can be represented by a linear model of several sequential steps required for a case to be captured in the provincial reportable disease surveillance system. Since reportable enteric data are known to represent only a small fraction of the total IGI in the community, the objective of this study was to estimate the under-reporting rate for IGI in Ontario.

METHODS

A distribution of plausible values for the under-reporting rate was estimated by specifying input distributions for the proportions reported at each step in the reporting chain, and multiplying these distributions together using simulation methods. Input distributions (type of distribution and parameters) for the proportion of cases reported at each step of the reporting chain were determined using data from the Public Health Agency of Canada's National Studies on Acute Gastrointestinal Illness (NSAGI) initiative.

RESULTS

For each case of enteric illness reported to the province of Ontario, the estimated number of cases of IGI in the community ranged from 105 to 1,389, with a median of 285, and a mean and standard deviation of 313 and 128, respectively.

CONCLUSIONS

Each case of enteric illness reported to the province of Ontario represents an estimated several hundred cases of IGI in the community. Thus, reportable disease data should be used with caution when estimating the burden of such illness. Program planners and public health personnel may want to consider this fact when developing population-based interventions.