Akrum H. Tamimi

Transfer efficiency of bacteria and viruses from porous and nonporous fomites to fingers under different relative humidity conditions.

ABSTRACT Fomites can serve as routes of transmission for both enteric and respiratory pathogens. The present study examined the effect of low and high relative humidity on fomite-to-finger transfer efficiency of five model organisms from several common inanimate surfaces (fomites). Nine fomites representing porous and nonporous surfaces of different compositions were studied. Escherichia coli, Staphylococcus aureus, Bacillus thuringiensis, MS2 coliphage, and poliovirus 1 were placed on fomites in 10-μl drops and allowed to dry for 30 min under low (15% to 32%) or high (40% to 65%) relative humidity. Fomite-to-finger transfers were performed using 1.0 kg/cm2 of pressure for 10 s. Transfer efficiencies were greater under high relative humidity for both porous and nonporous surfaces. Most organisms on average had greater transfer efficiencies under high relative humidity than under low relative humidity. Nonporous surfaces had a greater transfer efficiency (up to 57%) than porous surfaces (<6.8%) under low relative humidity, as well as under high relative humidity (nonporous, up to 79.5%; porous, <13.4%). Transfer efficiency also varied with fomite material and organism type. The data generated can be used in quantitative microbial risk assessment models to assess the risk of infection from fomite-transmitted human pathogens and the relative levels of exposure to different types of fomites and microorganisms.

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.

Long-term efficacy of a self-disinfecting coating in an intensive care unit

BACKGROUND Cleaning and disinfecting fomites can effectively remove/kill pathogens on surfaces, but studies have shown that more than one-half the time, surfaces are not adequately cleaned or are recontaminated within minutes. This study evaluated a product designed to create a long-lasting surface coating that provides continuous disinfecting action. METHODS This study was performed in an intensive care unit (ICU) in a major hospital. Various sites within the ICU were cultured before treatment and then at 1, 2, 4, 8, and 15 weeks after application of an antimicrobial coating. Samples were cultured for total bacteria, as well as Clostridium difficile, methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococcus, and carbapenemase-resistant Enterobacteriaceae. RESULTS The average bacterial count on all treated surfaces was reduced by >99% (2 logs) for at least 8 weeks after treatment. Overall, average levels of bacteria never returned to those observed before treatment even after 15 weeks. Antibiotic-resistant bacteria were found on 25% of the sites tested before treatment, but were isolated at only 1 site during the 15 weeks after treatment. CONCLUSIONS The product assessed in this study was found to have persisted over 15 weeks in reducing the total number of bacteria and antibiotic resistant bacteria on surfaces within an ICU.

Reduction of risk of Salmonella infection from kitchen cleaning clothes by use of sodium hypochlorite disinfectant cleaner

The objective of this study was to evaluate the reduction of infection risk due to exposure to Salmonella sp. in kitchen cleaning clothes by the use of a bleach (sodium hypochlorite) cleaner utilizing a continuous‐time dynamic exposure model. The only route of exposure considered was hand contamination during cloth use. The occurrence and numbers of Salmonella was studied in 60 homes over a 6‐week period in which half disinfected kitchen cleaning clothes with a sodium hypochlorite based disinfectant cleaner. This study demonstrated that a significant risk exists for Salmonella infection from kitchen cleaning clothes in Mexican homes and that this risk can be reduced by almost 100‐fold by soaking cleaning clothes in a bleach product. The risks of infection and illness could likely be further reduced by developing a more effective procedure for reducing Salmonella in cleaning clothes treated twice a day with a sodium hypochlorite disinfectant (i.e. longer soaking time) or using a greater concentration of the disinfectant.