The survival and transfer of microbial contamination via cloths, hands and utensils

Survival and transfer of bacteria from laminated surfaces and cleaning cloths were investigated under laboratory conditions. Drying produced substantial reductions in numbers of recoverable organisms and achieved satisfactory decontamination of clean laminate surfaces. On soiled surfaces and on clean and soiled cloths, Gram-positive and some Gram-negative species survived for up to 4 h, and in some cases up to 24 h. Where contaminated surfaces or cloths came into contact with the fingers, a stainless steel bowl, or a clean laminate surface, organisms were transferred in sufficient numbers to represent a potential hazard if in contact with food.     

Achieving hygiene in the domestic kitchen: the effectiveness of commonly used cleaning procedures

AIMS: To quantify the transmission of Salmonella and Campylobacter to hands, cloths, and hand- and food-contact surfaces during the preparation of raw poultry in domestic kitchens, and to examine the impact on numbers of these bacteria of detergent-based cleaning alone, or in conjunction with thorough rising. METHODS AND RESULTS: Groups of volunteers prepared chickens for cooking. Surfaces were sampled either before cleaning or after cleaning using water and detergent with or without thorough rinsing. Although cleaning followed by rinsing consistently achieved decontamination of surfaces contaminated with Campylobacter, significant numbers of surfaces were still contaminated with low numbers of Salmonella. Where cloths contaminated with Salmonella were stored overnight, a reduction in the efficacy of detergent-based cleaning regimes was observed. CONCLUSIONS: Rinsing is the critical step in ensuring that bacteria are removed from surfaces during cleaning, but this may still leave residual contamination. Growth of Salmonella occurs in some contaminated cloths during overnight storage; Salmonella on cloths stored overnight are also more difficult to remove by washing. SIGNIFICANCE AND IMPACT OF THE STUDY: Rinsing, as part of the cleaning process, is a critical step in achieving hygiene in the kitchen. However, to achieve completely hygienic surfaces, the use of an antimicrobial agent may be necessary.     

An in-use study of the relationship between bacterial contamination of food preparation surfaces and cleaning cloths

The relationship between bacterial contamination of food preparation surfaces and the cleaning cloths associated with these surfaces was investigated in a busy college kitchen. Cleaning cloths used in conjunction with detergent became heavily contaminated within hours of first use. Following 'cleaning' with these cloths with detergent, both surfaces and cloths were found to be more heavily contaminated and there was evidence of contamination transfer to and from cloths and surfaces. Following 'cleaning' with cloths impregnated with quaternary ammonium disinfectant, there was a significant reduction in contamination on both surfaces and cloths, together with a reduction in the numbers of enterobacteria and pseudomonads. The results suggest that significant improvements in kitchen hygiene could be achieved by ensuring that contaminated cloths are not used for food preparation activities.     

Removal and transfer of viruses on food contact surfaces by cleaning cloths

Contamination of food contact surfaces with pathogens is considered an important vehicle for the indirect transmission of food-borne diseases. Five different cleaning cloths were assessed for the ability to remove viruses from food contact surfaces (stainless steel surface and nonporous solid surface) and to transfer viruses back to these surfaces. Cleaning cloths evaluated include two different cellulose/cotton cloths, one microfiber cloth, one nonwoven cloth, and one cotton terry bar towel. Four viral surrogates (murine norovirus [MNV], feline calicivirus [FCV], bacteriophages PRD1 and MS2) were included. Removal of FCV from stainless steel was significantly greater (P ≤ 0.05) than that from nonporous solid surface, and overall removal of MNV from both surfaces was significantly less (P ≤ 0.05) than that of FCV and PRD1. Additionally, the terry towel removed significantly fewer total viruses (P ≤ 0.05) than the microfiber and one of the cotton/cellulose cloths. The cleaning cloth experiments were repeated with human norovirus. For transfer of viruses from cloth to surface, both cellulose/cotton cloths and microfiber transferred an average of 3.4 and 8.5 total PFU, respectively, to both surfaces, and the amounts transferred were significantly different (P ≤ 0.05) from those for the nonwoven cloth and terry towel (309 and 331 total PFU, respectively). There was no statistically significant difference (P > 0.05) in the amount of virus transfer between surfaces. These data indicate that while the cleaning cloths assessed here can remove viruses from surfaces, some cloths may also transfer a significant amount of viruses back to food contact surfaces.     

A comparison of contact plate and calcium alginaie swab techniques for quantitative assessment of bacteriological contamination of environmental surfaces

S cott , E. B loomfield , S.F. & B arlow , C.G. 1984. A comparison of contact plate and calcium alginate swab techniques for quantitative assessment of bacteriological contamination of environmental surfaces. Journal of Applied Bacteriology 56 , 317–320.
A contact plate method for enumeration of bacteriological contamination at 9 environmental sites in 64 homes was compared with swab sampling techniques. Contamination levels of 100 or more organisms/21–25 cm² were demonstrated more frequently using swab methods, but for some sites where low numbers of organisms were present, higher recovery rates were obtained using contact plates. When contamination levels from contact plate and swab techniques were compared according to rank order a good correlation was obtained. Results of this investigation indicate that the contact plate method is satisfactory for differentiation of 'hygiene levels' at environmental sites whilst facilitating handling of large numbers of samples in a field survey.     

Intermittent stimulation and delay of puberty by urinary chemosignals and social contact in wild stock female house mice (Mus Domesticus)

A sequence of six experiments using wild stock house mouse (Mus domesticus) tested the effects of intermittent stimulation with either the urinary chemosignal released by grouped female mice or social contact from grouped females on the age of first vaginal oestrus in young females. Weanling female mice were exposed to bedding soiled by grouped females or cages containing grouped females for 15 min periods, then removed for a prescribed period, and placed again in a cage with soiled bedding or grouped females. The nature of the exposure to the puberty delaying effect, the number of total exposures each day, the total length of exposure to the stimulus, and the total time period over which the exposures occurred were varied. None of the treatment regimes employed here with soiled bedding from grouped females resulted in delays in the onset of first oestrus in test females. Young females exposed to grouped females for 6 or 8 exposures in a 4 h period, 6 or 8 exposures in an 8 h period, or 8 exposures in a 12 h period were significantly delayed in attaining puberty relative to control females that were exposed to cages containing clean bedding. These results are in contrast to earlier findings involving chemosignals that accelerate first oestrus wherein young females exhibited the capacity to accumulate the exposures to the urinary chemosignals from males, females in oestrus and pregnant or lactating females. Direct exposure to the grouped females on an intermittent basis can provide stimulation that is cummulative and results in delays in the onset of first oestrus.     

Do European Standard Disinfectant tests truly simulate in‐use microbial and organic soiling conditions on food preparation surfaces?

Aims: The results from European standard disinfectant tests are used as one basis to approve the use of disinfectants in Europe. The design of these laboratory‐based tests should thus simulate as closely as possible the practical conditions and challenges that the disinfectants would encounter in use. No evidence is available that the organic and microbial loading in these tests simulates actual levels in the food service sector. Methods and Results: Total organic carbon (TOC) and total viable count (TVC) were determined on 17 visibly clean and 45 visibly dirty surfaces in two restaurants and the food preparation surfaces of a large retail store. These values were compared to reference values recovered from surfaces soiled with the organic and microbial loading, following the standard conditions of the European Surface Test for bactericidal efficacy, EN 13697. Conclusions: The TOC reference values for clean and dirty conditions were higher than the data from practice, but cannot be regarded as statistical outliers. This was considered as a conservative assessment; however, as additional nine TOC samples from visibly dirty surfaces were discarded from the analysis, as their loading made them impossible to process. Similarly, the recovery of test organisms from surfaces contaminated according to EN 13697 was higher than the TVC from visibly dirty surfaces in practice; though they could not be regarded as statistical outliers of the whole data field. No correlation was found between TVC and TOC in the sampled data, which re‐emphasizes the potential presence of micro‐organisms on visibly clean surfaces and thus the need for the same degree of disinfection as visibly dirty surfaces. Significance and Impact of the Study: The organic soil and the microbial burden used in EN disinfectant standards represent a realistic worst‐case scenario for disinfectants used in the food service and food‐processing areas.     

Microbiology of Drycleaning

An appreciable number of bacteria on contaminated fabric survived modern drycleaning procedures. Various stages in the process, especially steam pressing, reduced the total number of bacteria, but viable organisms were found on certain areas of garments even after pressing. A significant number of bacteria were redeposited on clean fabric during the washing of ordinary soiled garments in drycleaning units. These bacteria included gram-positive cocci, diphtheroid bacilli, and gram-positive sporeformers. Gram-negative bacilli were seldom found, although some gram-negative bacilli survived drycleaning. The redeposited organisms apparently came mainly from other garments in the same loads, as few bacteria were isolated from the filtered solvent used for washing. The number of bacteria in the drycleaning washwheel was highest shortly after the beginning of the wash, and decreased, with the exchange of solvent in the wheel, to a low level at the end. Although it appears that in most cases several factors combine to reduce to a low level the numbers of bacteria on articles cleaned in a well-operated drycleaning plant, it would seem that under certain conditions pathogenic microorganisms could be disseminated by drycleaning.     

Microbiology of Drycleaning

An appreciable number of bacteria on contaminated fabric survived modern drycleaning procedures. Various stages in the process, especially steam pressing, reduced the total number of bacteria, but viable organisms were found on certain areas of garments even after pressing. A significant number of bacteria were redeposited on clean fabric during the washing of ordinary soiled garments in drycleaning units. These bacteria included gram-positive cocci, diphtheroid bacilli, and gram-positive sporeformers. Gram-negative bacilli were seldom found, although some gram-negative bacilli survived drycleaning. The redeposited organisms apparently came mainly from other garments in the same loads, as few bacteria were isolated from the filtered solvent used for washing. The number of bacteria in the drycleaning washwheel was highest shortly after the beginning of the wash, and decreased, with the exchange of solvent in the wheel, to a low level at the end. Although it appears that in most cases several factors combine to reduce to a low level the numbers of bacteria on articles cleaned in a well-operated drycleaning plant, it would seem that under certain conditions pathogenic microorganisms could be disseminated by drycleaning.     

Enteric virus survival during household laundering and impact of disinfection with sodium hypochlorite

This study was conducted to determine whether enteric viruses (adenovirus, rotavirus, and hepatitis A virus) added to cotton cloth swatches survive the wash cycle, the rinse cycle, and a 28-min permanent press drying cycle as commonly practiced in households in the United States. Detergent with and without bleach (sodium hypochlorite) was added to washing machines containing sterile and virus-inoculated 58-cm2 swatches, 3.2 kg of cotton T-shirts and underwear, and a soiled pillowcase designed to simulate the conditions (pH, organic load, etc.) encountered in soiled laundry. The most important factors for the reduction of virus in laundry were passage through the drying cycle and the addition of sodium hypochlorite. Washing with detergent alone was not found to be effective for the removal or inactivation of enteric viruses, as significant concentrations of virus were found on the swatches (reductions of 92 to 99%). It was also demonstrated that viruses are readily transferred from contaminated cloths to uncontaminated clothes. The use of sodium hypochlorite reduced the number of infectious viruses on the swatches after washing and drying by at least 99.99%. Laundering practices in common use in the United States do not eliminate enteric and respiratory viruses from clothes. The use of bleach can further reduce the numbers of enteric viruses in laundry.     

Pheromone-induced reproductive inhibition in young female Peromyscus leucopus

Soiled bedding and urine from adult female white-footed mice (Peromyscus leucopus) were tested for their capacity to inhibit reproduction of young females. Test animals were given either physical or airborne contact with soiled bedding from adult females, adult female urine, clean bedding, or water from 21 to 150 days of age. Results indicate that reproductive inhibition is due to an airborne pheromone emitted by the adult females as a component of their urine. In the second experiment, young female mice were exposed to an adult female for 0, 1, 3, 6, 12, 18, or 24 h/day from 21 to 150 days of age. Results from this experiment show that exposure to adult females of as little as 3 h/day was sufficient to cause reproductive inhibition to occur. This phenomenon has important implications in terms of both female-female reproductive competition and socially mediated population regulation.     

Cleaning and decontamination efficacy of wiping cloths and silver dihydrogen citrate on food contact surfaces

Aims: To test the efficacy of four wipe cloth types (cotton bar towel, nonwoven, microfibre and blended cellulose/cotton) with either quaternary ammonia cleaning solution or silver dihydrogen citrate (SDC) in cleaning food contact surfaces. Methods: Swab samples collected from untreated, cloth‐treated and cloth disinfectant‐treated surfaces were subjected to hygiene monitoring using adenosine triphosphate (ATP) bioluminescence and aerobic total plate counting (TPC) assays. Results: Adenosine triphosphate measurements taken after wiping the surfaces showed poor cleaning by nonwoven cloths (2·89 RLU 100 cm^?2) than the microfibre (2·30 RLU 100 cm^?2), cotton terry bar (2·26 RLU 100 cm^?2) and blended cellulose/cotton cloth types (2·20 RLU 100 cm^?2). The cellulose/cotton cloth showed highest log reduction in ATP‐B RLU values (95%) and CFU values (98·03%) when used in combination with SDC disinfectant. Conclusions: Cleaning effect of wiping cloths on food contact surfaces can be enhanced by dipping them in SDC disinfectant. ATP‐B measurements can be used for real‐time hygiene monitoring in public sector, and testing microbial contamination provides more reliable measure of cleanliness. Significance and Impact of the Study: Contaminated food contact surfaces need regular hygiene monitoring. This study could help to estimate and establish contamination thresholds for surfaces at public sector facilities and to base the effectiveness of cleaning methods.     

Use of fluorescent lectin probes for analysis of footprints from Pseudomonas aeruginosa MDC on hydrophilic and hydrophobic glass substrata

Microbial footprints of Pseudomonas aeruginosa MDC attached for 1 h to clean or silanized glass were analyzed with fluorescently labeled lectin probes. Footprint composition varied, depending on cell physiology and substratum surface chemistry. This suggests that substratum physicochemistry affected the structure of cell surfaces of adsorbed organisms.     

Enteric Virus Survival during Household Laundering and Impact of Disinfection with Sodium Hypochlorite

This study was conducted to determine whether enteric viruses (adenovirus, rotavirus, and hepatitis A virus) added to cotton cloth swatches survive the wash cycle, the rinse cycle, and a 28-min permanent press drying cycle as commonly practiced in households in the United States. Detergent with and without bleach (sodium hypochlorite) was added to washing machines containing sterile and virus-inoculated 58-cm² swatches, 3.2 kg of cotton T-shirts and underwear, and a soiled pillowcase designed to simulate the conditions (pH, organic load, etc.) encountered in soiled laundry. The most important factors for the reduction of virus in laundry were passage through the drying cycle and the addition of sodium hypochlorite. Washing with detergent alone was not found to be effective for the removal or inactivation of enteric viruses, as significant concentrations of virus were found on the swatches (reductions of 92 to 99%). It was also demonstrated that viruses are readily transferred from contaminated cloths to uncontaminated clothes. The use of sodium hypochlorite reduced the number of infectious viruses on the swatches after washing and drying by at least 99.99%. Laundering practices in common use in the United States do not eliminate enteric and respiratory viruses from clothes. The use of bleach can further reduce the numbers of enteric viruses in laundry.     

Use of Fluorescent Lectin Probes for Analysis of Footprints from Pseudomonas aeruginosa MDC on Hydrophilic and Hydrophobic Glass Substrata

Microbial footprints of Pseudomonas aeruginosa MDC attached for 1 h to clean or silanized glass were analyzed with fluorescently labeled lectin probes. Footprint composition varied, depending on cell physiology and substratum surface chemistry. This suggests that substratum physicochemistry affected the structure of cell surfaces of adsorbed organisms.     

The influence of pheromones produced by freely growing laboratory populations on the reproductive maturation of prairie deermice following prenatal and postnatal exposure

Significantly more females reared on bedding soiled by different populations reproduced by 100 days of age than those reared on bedding soiled by the same populations (P<.1) or on clean bedding (P<.025) whereas the latter two groups did not differ significantly. Significantly greater percentages of females reproduced in both treatments maintained on soiled bedding than was true in the populations from which the bedding came. There were no significant differences between treatments in the weights of the reproductive organs (testes, seminal vesicles, ovaries, uteri) or in the numbers of corpora lutea or mature follicles in the ovaries of nulliparous females. The data suggest that if there were reproductively inhibiting pheromones influencing the population animals, they were altered or dissipated immediately after removal of the bedding from the population enclosures or that they were nonfunctional in the absence of the population animals. These data further suggest that the reproductive inhibition of population young is due to the presence of the populaton animals and that sociobiological factors within the populations act to prevent the reproductively stimulating influence of materials which may be present.     

The influence of pheromones produced by freely growing laboratory populations on the reproductive maturation of prairie deermice following prenatal and postnatal exposure

Summary Significantly more females reared on bedding soiled by different populations reproduced by 100 days of age than those reared on bedding soiled by the same populations (P<.1) or on clean bedding (P<.025) whereas the latter two groups did not differ significantly. Significantly greater percentages of females reproduced in both treatments maintained on soiled bedding than was true in the populations from which the bedding came. There were no significant differences between treatments in the weights of the reproductive organs (testes, seminal vesicles, ovaries, uteri) or in the numbers of corpora lutea or mature follicles in the ovaries of nulliparous females. The data suggest that if there were reproductively inhibiting pheromones influencing the population animals, they were altered or dissipated immediately after removal of the bedding from the population enclosures or that they were nonfunctional in the absence of the population animals. These data further suggest that the reproductive inhibition of population young is due to the presence of the populaton animals and that sociobiological factors within the populations act to prevent the reproductively stimulating influence of materials which may be present.     

A comparison of contact plate and calcium alginate swab techniques for quantitative assessment of bacteriological contamination of environmental surfaces

A contact plate method for enumeration of bacteriological contamination at 9 environmental sites in 64 homes was compared with swab sampling techniques. Contamination levels of 100 or more organisms/21-25 cm2 were demonstrated more frequently using swab methods, but for some sites where low numbers of organisms were present, higher recovery rates were obtained using contact plates. When contamination levels from contact plate and swab techniques were compared according to rank order a good correlation was obtained. Results of this investigation indicate that the contact plate method is satisfactory for differentiation of hygiene levels at environmental sites whilst facilitating handling of large numbers of samples in a field survey.     

Bacterial primary colonization and early succession on surfaces in marine waters as determined by amplified rRNA gene restriction analysis and sequence analysis of 16S rRNA genes

The nearly universal colonization of surfaces in marine waters by bacteria and the formation of biofilms and biofouling communities have important implications for ecological function and industrial processes. However, the dynamics of surface attachment and colonization in situ, particularly during the early stages of biofilm establishment, are not well understood. Experimental surfaces that differed in their degrees of hydrophilicity or hydrophobicity were incubated in a salt marsh estuary tidal creek for 24 or 72 h. The organisms colonizing these surfaces were examined by using a cultivation-independent approach, amplified ribosomal DNA restriction analysis. The goals of this study were to assess the diversity of bacterial colonists involved in early succession on a variety of surfaces and to determine the phylogenetic affiliations of the most common early colonists. Substantial differences in the representation of different cloned ribosomal DNA sequences were found when the 24- and 72-h incubations were compared, indicating that some new organisms were recruited and some other organisms were lost. Phylogenetic analyses of the most common sequences recovered showed that the colonists were related to organisms known to inhabit surfaces or particles in marine systems. A total of 22 of the 26 clones sequenced were affiliated with the Roseobacter subgroup of the alpha subdivision of the division Proteobacteria (alpha-Proteobacteria), and most of these clones were recovered at a high frequency from all surfaces after 24 or 72 h of incubation. Two clones were affiliated with the Alteromonas group of the gamma-Proteobacteria and appeared to be involved only in the very early stages of colonization (within the first 24 h). A comparison of the colonization patterns on the test surfaces indicated that the early bacterial community succession rate and/or direction may be influenced by surface physicochemical properties. However, organisms belonging to the Roseobacter subgroup are ubiquitous and rapid colonizers of surfaces in coastal environments.     

Puberty in pine voles, Microtus pinetorum, and the influence of chemosignals on female reproduction

We investigated the reproductive biology of an induced ovulator, the pine vole (Microtus pinetorum). Male puberty, measured as age at first impregnation, was found to occur as early as 44 days of age. Female puberty measured as age at first conception, was found to occur as early as 32 days of age, considerably earlier than previously reported. Females paired with stud males exhibited a doubling of uterine weight within 12 h, and vaginal sperm were present after 48 h. This indicates that although behavioral responses to males--including mating--require prolonged contact, physiological responses to males occur rapidly. Chemosignals from males slightly increased uterine and ovarian weights of females, but chemosignals from other females did not. Young females paired with stud males for 48 h in the presence of soiled bedding from the female's family had significantly smaller increases in ovarian and uterine weights than similar females paired on clean bedding. Suppression of reproduction in female offspring while they remain with the extended family unit is discussed as a life-history tactic and as a possible mechanism for inbreeding avoidance.