Comparison of TEMPO® BC with Spiral Plating Methods for the Enumeration of Bacillus cereus in Cosmetic Products Either Naturally Preserved or Preserved with Phenoxyethanol

Background: The U.S. Food and Drug Administration's (FDA) Bacteriological Analytical Manual (BAM) uses Bacillus cereus rapid agar (BACARA) and Mannitol-yolk-polymyxin (MYP) agar for the enumeration of the members of B. cereus group. Objective: The automated TEMPO Most Probable Number system was compared with the FDA BAM method for the detection of B. cereus group members in cosmetic products. Methods: We inoculated a range of cosmetic products with pure B. cereus spore suspensions (density = 0.5 McFarland) at high (6 log CFU/mL), medium (5 log CFU/mL), and low (4 log CFU/mL) levels. Test portions were aged for 72 h. Five replicates per sample were analyzed; uninoculated test portions served as controls. We also evaluated whether TEMPO BC erroneously detected non-B. cereus or other adulterant organisms. Results: No significant differences (P > 0.05) were found among the TEMPO BC and the BAM spiral plating methods. Correlations between TEMPO BC - BACARA and TEMPO BC - MYP were 0.895 and 0.893 for powder type products, 0.834 and 0.846 for cream and oil-based products, and 0.929 and 0.923 for liquid products, respectively. Non-B. cereus strains were not detected by TEMPO BC. Conclusions: The TEMPO BC method can be used for the detection of B. cereus in cosmetic products without preservatives, or those preserved with either phenoxyethanol or other organic substances.

Development of compost maturity and Actinobacteria populations during full-scale composting of organic household waste

AIMS

This study investigates changes in microbiological and physicochemical parameters during large-scale, thermophilic composting of a single batch of municipal organic waste. The inter-relationships between the microbial biomass and community structure as well as several physicochemical parameters and estimates of maturation were evaluated.

METHODS AND RESULTS

Analyses of signature fatty acids with the phospholipid fatty acid and ester-linked methods showed that the total microbial biomass was highest during the early thermophilic phase. The contribution of signature 10Me fatty acids from Actinobacteria indicated a relatively constant proportion around 10% of the microbial community. However, analyses of the Actinobacteria species composition with a PCR-denaturing gradient gel electrophoresis approach targeting 16S rRNA genes demonstrated clear shifts in the community structure.

CONCLUSIONS

This study demonstrates that compost quality, particularly maturity, is linked to the composition of the microbial community structure, but further studies in other full-scale systems are needed to validate the generality of these findings.

SIGNIFICANCE AND IMPACT OF THE STUDY

The combination of signature lipid and nucleic acid-based analyses greatly expands the specificity and the scope for assessing the microbial community composition in composts. The results presented in this study give new information on how the development of the compost microbial community is connected to curing and maturation in the later stages of composting, and emphasizes the role of Actinobacteria in this respect.

Microbial inactivation by microwave radiation in the home environment

The study reported here looked at the survival of microorganisms (heterotrophic plate counts, total coliforms, E. coli, and bacterial spores) in a consumer-type microwave oven. Kitchen sponges, scrubbing pads, and syringes were experimentally contaminated with wastewater and subsequently exposed to microwave radiation. At 100 percent power level, it was found that the heterotrophic plate count (i.e., total bacterial count) of the wastewater was reduced by more that 99 percent within 1 to 2 minutes, and the total coliform and E. coli were totally inactivated after 30 seconds of microwave radiation. Bacterial phage MS2 was totally inactivated within 1 to 2 minutes. Spores of Bacillus cereus were more resistant than the other microorganisms tested, and were completely eradicated only after 4-minute irradiation. Similar inactivation rates were obtained in wastewater-contaminated scrubbing pads. Microorganisms attached to plastic syringes were more resistant to microwave irradiation than those associated with kitchen sponges or scrubbing pads. It took 10 minutes for total inactivation of the heterotrophic plate count and 4 minutes for total inactivation of total coliform and E. coli. A 4-log reduction of phage MS2 was obtained after 2 minutes; 97.4 percent reduction was observed after 12 minutes. The authors also observed a higher inactivation of B. cereus spores in syringes placed in a ceramic container than of spores in syringes placed in a glass container. This finding could have some implications for the design of containers to be used in exposure of medical devices to microwave radiation. The article discusses the implications of these findings for consumer safety in the home environment.

Induction of the mar operon by miscellaneous groceries

AIM

To investigate the potential of non-antibacterial consumer products to act as inducers of the multiple antibiotic resistance (mar) operon of Escherichia coli SPC105.

METHODS AND RESULTS

Wells were cut into chemically defined agar medium (CDM) contained within Petri dishes. Molten agar slurries were prepared by mixing known quantities of 35 consumer products with molten CDM and these were pipetted into each well. Plates were overlaid with molten CDM (5 ml), containing 40 microg ml(-1) X-gal and approx. 1000 CFU ml(-1) of an overnight culture of E. coli SPC105 containing a chromosomal marOII::lacZ fusion. After incubation (37 degrees C, 24 h), plates were examined for zones of growth inhibition and the presence of a blue coloration, indicative of mar (marOII::lacZ) induction. Of the 35 products tested (nine herbs and spices, 19 food and drinks and seven household products), 24 (69%) of the items produced inhibitory zones and 22 (63%) of the items induced mar expression. Apple puree was inhibitory but did not induce marOII::lacZ. Mustard, chilli and garlic were shown to be powerful inducers of marOII::lacZ. Overall six products were shown to be powerful marOII::lacZ inducers. None of these made hygiene claims.

CONCLUSIONS

In addition to induction by specific biocides and antibiotics, mar is induced by the exposure of bacteria to natural substances, many of which are common to a domiciliary setting.

SIGNIFICANCE AND IMPACT OF THE STUDY

Concern that the overuse of antibacterials within consumer products might select for mar-mediated resistance is shortsighted and fails to recognize the ubiquity of inducers in our environment.

Investigation of antibiotic and antibacterial agent cross-resistance in target bacteria from homes of antibacterial product users and nonusers

AIM

To describe the relationship between antibiotic and antibacterial resistance in environmental and clinical bacteria from home environments across geographical locations, relative to the use or nonuse of antibacterial products, with a focus on target organisms recognized as potential human pathogens.

METHODS AND RESULTS

In a randomized study, environmental and clinical samples were collected from the homes of antibacterial product users (n=30) and nonusers (n=30) for the isolation of target bacteria for antibiotic and antibacterial testing in three geographical areas (in USA and UK). Isolates were tested for antibiotic susceptibility, with selected antibiotic-resistant and antibiotic-susceptible isolates tested against four common antibacterial agents (triclosan, para-chloro-meta-xylenol, pine oil and quaternary ammonium compound). Prequalified users and nonusers at each location were randomly selected after meeting exclusionary criteria. Of 1238 isolates, more target bacteria were recovered from nonuser than user homes. Of Staphylococcus aureus isolates (n=33), none showed resistance to oxacillin or vancomycin; for Enterococcus sp. (n=149), none were resistant to ampicillin or vancomycin; and for Klebsiella pneumoniae (n=54)and Escherichia coli (n=24), none were resistant to third generation cephalosporins. Antibiotic resistance to one or more of the standard test panel drugs for Gram-positive and Gram-negative target bacteria was comparable between nonuser and user homes for both environmental and clinical isolates [e.g. resistance of environmental coagulase-negative (CN) Staphylococcus sp. was 73.8% (124/168) from nonuser homes and 73.0% (111/152) from user homes, and Enterobacteriaceae other than E. coli, 75.9% (186/245) from nonuser homes compared with 78.0% from user homes]. Of 524 Gram-negatives tested against preferred/alternative drugs, 97.1% (509/524) were susceptible to all antibiotics, across both groups. Isolates of S. aureus, Enterococcus sp. and CN Staphylococcus sp. susceptible to all preferred treatment drugs showed comparable antibacterial minimum inhibitory concentration (MIC) results between nonuser and user home isolates. For Gram-positives resistant to one or more preferred drugs, greatest resistance to antibacterial active ingredients was found in the nonuser group. For Gram-negatives, the antibacterial MIC data were comparable for isolates that were fully susceptible and resistant to one or more preferred/alternative treatment antibiotics.

CONCLUSIONS

The results showed a lack of antibiotic and antibacterial agent cross-resistance in target bacteria from the homes of antibacterial product users and nonusers, as well as increased prevalence of potential pathogens in nonuser homes.

SIGNIFICANCE AND IMPACT OF THE STUDY

It refutes widely publicized, yet unsupported, hypotheses that use of antibacterial products facilitates the development of antibiotic resistance in bacteria from the home environment.

Products containing biocides: perceptions and realities

The mechanisms of action for chemical germicides and antibiotics for inactivating microorganisms are significantly different and methods for determining resistance by microorganisms to these agents are also different. Chemical germicides usually have multiple targets and the mechanisms for inactivation and resistance are not measured in absolute terms but rather in the rapidity with which they reduce levels of microorganisms. The term tolerance is much more suited for germicides than the term resistance. The mechanism of resistance to chemical germicides is often dependent on the concentration of the germicide. At high concentrations multiple cellular and metabolic targets are involved, and at low concentrations fewer cellular targets. In contrast antibiotics usually have a singular cellular or metabolic target and resistance implies the ability of the microorganism to grow in the presence of the antibiotic, and in a clinical sense, to initiate or continue infection in the presence of the antibiotic. When methods used to assess resistance to antibiotics are applied to chemical germicides, inappropriate interpretations can be made regarding the ability of microorganisms to develop resistance to antibiotics as a result of developing resistance to chemical germicides. The use of chemical germicides in health-care institutions and especially the home setting has increased in recent years. Although there may be an overuse of germicides in these settings the consequence is a cost issue and not one that involves the development of antibiotic resistant microorganisms.

Effects of antibacterial dishwashing liquid on foodborne pathogens and competitive microorganisms in kitchen sponges

In response to increasing concern about home hygiene, the use of antibacterial products to reduce microorganisms in kitchen sponges and cleaning cloths is strongly promoted by some producers of detergent for domestic use. The effects of an antibacterial dishwashing liquid on Escherichia coli, Salmonella Enteritidis, Staphylococcus aureus, and Bacillus cereus were investigated in a modified suspension test and in used sponges with and without food residues under laboratory conditions. A limited study was conducted in households to assess the efficacy of antibacterial dishwashing liquid as used by the consumer. In the suspension tests, S. aureus and B. cereus were shown to be susceptible to low concentrations of antibacterial dishwashing liquid (0.5%), whereas E. coli and Salmonella Enteritidis maintained their initial numbers for at least 24 h at 25 degrees C. At higher concentrations (2 to 4%), all test organisms decreased to below the detection limit after 24 h. Over a 24-h period, the antibacterial dishwashing liquid did not significantly reduce these organisms in used sponges in which food residues were present. The antibacterial product did not reduce the competitive microorganisms either. Similar results were found for sponges involved in daily household use. The results of this study demonstrate that the antibacterial dishwashing liquid was effective in reducing pathogens in the suspension test but not in the used sponges. This finding indicates that to determine the efficacy of antibacterial products, their use in a household setting must be considered.

Automated screening method for determining optimum preservative systems for personal and home care products

A procedure was designed to determine the minimum preservative level (MPL) for personal and home care products. A highly preserved sample and an unpreserved sample were combined at different concentrations within a 96-well microtiter plate by using an autodilutor. A unique tip design made it possible to accurately deliver viscous test materials that cannot be dispensed using vacuum- or fluid-filled systems. After inoculation, the sample was evaluated at a specified time interval for the presence of surviving bacteria, yeast, and mold. The lowest concentration of preservative with no microbial growth is the recommended level of preservative for the product. Because sample turbidity may interfere with determination of the endpoint, a colorimetric endpoint was used to indicate growth of microorganisms and to differentiate product from growth. The predicted levels were tested with a modified Cosmetic, Toiletry, and Fragrance Association method. The method successfully predicted effective preservative levels in many personal and home care products with a broad range of viscosities.