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PubMed1971

Inhibition of injured Escherichia coli by several selective agents.

A population of Escherichia coli ML30 cells was exposed to a quaternary ammonium compound, and injury to the cells was measured by a comparison of counts on Trypticase Soy Agar and Violet Red Bile Agar. Substantial injury could not be detected with a minimal medium. The ingredients of Violet Red Bile Agar were tested against damaged cells. The bile salts mixture alone in the medium prevented as many injured cells from growing as did any combination of the selective agents and inhibited as many injured bacteria as were inhibited by Violet Red Bile Agar itself. These dyes and salts were similarly assayed in minimal agar, and comparable results were obtained. Individual bile salts and other potential selective agents were added to the minimal medium, and the media were tested for inhibition of injured E. coli. Sodium deoxycholate was the bile salt most inhibitory to damaged E. coli cells.

Agar↗

PubMed1999

Selectivity of the polyspecific cation transporter rOCT1 is changed by mutation of aspartate 475 to glutamate.

After site-directed mutagenesis, the organic cation transporter rOCT1 was expressed in Xenopus laevis oocytes or human embryonic kidney cells and functionally characterized. rOCT1 belongs to a new family of polyspecific transporters that includes transporters for organic cations and anions and the Na(+)-carnitine cotransporter. When glutamate was substituted for Asp475 (middle of the proposed 11th transmembrane alpha-helix), the V(max) values for choline, tetraethylammonium (TEA), N(1)-methylnicotinamide, and 1-methyl-4-phenylpyridinium were reduced by 89 to 98%. The apparent K(m) values were also decreased (choline by 15-fold, TEA by 8-fold, N(1)-methylnicotinamide by 4-fold) or remained constant (1-methyl-4-phenylpyridinium). After the mutation, the membrane potential dependence of the K(m) value for [(3)H]choline uptake was abolished. The affinity of n-tetraalkyl ammonium compounds to inhibit TEA uptake was increased. This affinity and its increase by the D475E mutation were increased with the length of the n-alkyl chains. After expression in X. laevis oocytes, the IC(50) ratios of wild-type and D475E mutant were 1.7 (tetramethylammonium), 4.3 (TEA), 5.0 (tetrapropylammonium), 5.0 (tetrabutylammonium), and 65 (tetrapentylammonium). Cationic inhibitors with ring structures were differentially affected: the IC(50) value for TEA inhibition by cyanine 863 remained unchanged, whereas it was increased for quinine. The data suggest that rOCT1 contains a large cation-binding pocket with several interaction domains that may be responsible for high-affinity binding of structurally different cations and that Asp475 is located close to one of these interaction domains.

Amino Acid Substitution↗

PubMed1979

Instrument sterilization in orthodontic offices.

1. Three different quaternary ammonium compound solutions remained bactericidal against specific vegetative bacteria in three orthodontic offices over a ten day working period. However, no spore formers or viruses were tested. 2. Bacterial contaminants were cultured on pliers and scalers at the chair at least once in each of three orthodontic offices sampled twice a day for ten working days. 3. Sampled chairside instruments wiped with an alcohol sponge only, between patients, were contaminated an excessive 32.5% of the time, too frequently to be seriously considered for routine disinfection of pliers. 4. Chairside instruments, sampled regardless of other means of disinfection or sterilization used, were contaminated from 3.5 to 15% of the time. Therefore, storage and handling of orthodontic instruments must be evaluated and upgraded to prevent recontamination of previously sterilized instruments. 5. Staff personnel need courses in sterilization and disinfection procedures to prevent cross contamination from patient to patient and to protect themselves. These courses should be related specifically to orthodontic practice procedures.

Bacteria↗

PubMedDate not supplied

[Lipid peroxidation in an experimental study of an erosion-ulcer lesion of the stomach as affected by the new high-protein products and ethonium].

New high-protein vitamin product "Biostim" and bisquaternary ammonium compound etonium have been studied for their effect on the content of endogenic lipids (isolated binary bonds, diene conjugates, ketodienes and conjugated trienes) and reduced glutathione in the stomach and liver tissues under experimental duodenal ulcer with results presented. Maximal effect of "Biostim" on the intensity of the processes of free-radical oxidation in these tissue falls on the 14th day of the experiment, that of etonium on the 10th day, their simultaneous use--on the 6th day of the treatment. It is supposed that the combination of the above drugs takes most pronounced antioxidant effect owing to the fact that etonium activates the operation of glutathione cycle, promotes blocking of formation of free radicals and interacts with them. Under these conditions biosynthetic processes in the cell membranes induced by "Biostim" are more intensive and this, in its turn, promotes free-radical inhibition of lipids and biopolymers.

Animals↗

PubMed1995

[Epidemiology of microbial resistance to biocides].

In order to estimate the distribution of bacteria and fungi with an elevated level of resistance to antimicrobial substances, we have analyzed water samples and surveyed institutions presumably concerned with analyses of microbial resistance (university institutes for hygiene, health authorities) by means of questionnaire. A total of 41 water samples was drawn from various aquatic biotopes in the region of Heidelberg. The samples originated from the effluents of a community sewage treatment plant, from the Neckar river, from drinking water supplies and from public swimming pools. The following substance groups were included in a search for bacteria with an elevated resistance to antiseptics and disinfectants: Aldehydes, biguanides, quaternary ammonium compounds (QAC), phenols and halogen. Upon determination of the maximal tolerated concentrations to these antimicrobial agents, samples of treated wastewater effluents showed a considerably higher prevalence of bacteria resistant to formaldehyde, chlorhexidine and QAC. The highest levels of resistance were found in Pseudomonas aeruginosa, Pseudomonas putida, Pseudomonas fluorescens and Enterobacter species. The maximal tolerated level of 0.06 percent formaldehyde by weight was considerably higher than the levels tolerated by the corresponding ATCC reference strains. The highest levels of resistance to a biguanid/QAC preparation were seen in isolates of Alcaligenes species and Providencia species, with a maximal tolerated level of 0.5 volume percent. In addition, several isolates of E. coli and Klebsiella species were observed which showed a considerably higher level of resistance to the biguanide preparation as compared to the corresponding ATCC reference strains. A questionnaire was mailed to a series of institutions and companies presumably concerned with problems of microbial resistance. Responses were in accordance with our own observations, both with regard to the spectrum of bacteria observed and to the antimicrobial substances concerned.

Aldehydes↗

PubMed1985

Ion pair formation and gastrointestinal absorption of emepronium.

Ion pair forming agents were evaluated in vitro for their ability to form lipophilic ion pairs with the quaternary ammonium compound emepronium and in vivo to enhance its gastrointestinal absorption. A 5- to 100-fold excess of trichloroacetate (TCA), diethylhexylphosphate (DEHPA), heptafluorobutyrate (HFBA), sodium lauryl sulphate (SLS), bromide or chloride all increased the extractability of the emepronium ion into methylene chloride. The additive with the most marked effect on the apparent partition coefficient of emepronium (Kapp) was SLS. At emepronium 10(-4) M, Kapp increased from a basal value of 0.1 to 368 with a 100-fold molar excess. However, the increased partitioning to methylene chloride was not reflected in an increased gastrointestinal absorption of the emepronium ion when this was given orally to mice. When intestinal juice, instead of distilled water or buffer, was used as the aqueous phase, the partition coefficient was markedly higher (Kapp approximately 2) but it was significantly less influenced by addition of sodium lauryl sulphate (Kapp approximately 6). The preexisting positive influence of the intestinal juice on the lipophilic character of emepronium and the rather limited additive effect of agents that form lipophilic complexes with emepronium, lead to the conclusion that the ion pair concept is not a suitable approach to enhance the gastrointestinal absorption of this drug.

Animals↗

PubMed1988

Availability of organic chemicals for biodegradation in settled bottom sediments.

Biodegradation rates for dodecyltrimethylammonium chloride (TMAC), a quaternary ammonium compound, and phenol were measured in settled sediments to determine if adsorbed chemicals were directly available for biodegradation by sediment-associated bacteria. In settled sediment cores, biodegradation rates for TMAC, which is charged at environmental pH, was a function of the amount of unadsorbed chemical; adsorbed material was not directly degraded by the sediment-associated bacteria. However, the rate of biodegradation of adsorbed phenol, a relatively hydrophobic and neutral chemical, was apparently a function of the total concentration of material present, suggesting that at least a fraction of the adsorbed material was directly degraded. These results indicate that chemical structure and, possibly, the mechanism of adsorption may influence biodegradation in sediments. Studies on TMAC biodegradation in completely mixed sediment/water slurries (up to 10 g/liter sediment) showed that TMAC biodegradation in slurries differed from that in settled sediments. Biodegradation in slurries was a function of the total amount of material present, both adsorbed and unadsorbed. These results suggest that biodegradation in settled sediments may be influenced by high concentrations of sediment present and/or the lack of mixing. Thus mixed, low-sediment-level slurries may not be realistic surrogates for modeling biodegradation processes in settled bottom sediments.

Adsorption↗

PubMed2005

[In vitro activity of commercially available disinfectants against Stenotrophomonas maltophilia].

In vitro antibacterial efficacy of 14 commercially available disinfectants against the hospital pathogen Stenotrophomonas maltophilia was tested. The test disinfectants included 5 "pure" quartenary ammonium compounds (QACs) and 9 combination formulations with QACs as the major ingredient. Antibacterial efficacy was expressed as MIC, ED50 and inhibition of the rate of incorporation of radioactive precursors [14C] adenine and [14C] leucine. Based on their activity, the disinfectants were divided into four groups. Group I characterized by high inhibitory activity (MIC 0.045-0.09 microg/ml) comprised benzalconium chloride and Triquart. Group II included formulations with good antibacterial activity (MIC 0.19-0.78 microg/ml) while group III formulations showed MICs between 1.56 and 25 microg/ml. The less active Cetrimid (MIC 50-100 microg/ml) was classified into group IV. When effects on biosynthetic processes expressed as R values (IC50 Ade : IC50 Leu) were tested, R < 1 was only recorded for the following formulations: Hexaquart plus, Diesen forte, Sokrena, Forten, ID 212 and Cetrimid. Lower values of IC50 Ade and IC50 Leu are suggestive of effects on the synthesis of nucleic acids and proteins leading to inhibition of the two precursors. Endogenous respiration was almost 50% inhibited by Cetrimid and Microbac forte at a concentration of 0.78 microg/ml, and 100% inhibited by Almyrol, Diesen forte and Microbac forte at a concentration of 6.25 microg/ml and by FD312, Triquart, Hexaquart plus, Hexaquart S, ID 212, TPH 5225 at a concentration of 12.5 microg/ml.

Disinfectants↗

PubMed2004

Surface fixation of dried blood by glutaraldehyde and peracetic acid.

The difficulties of successful prion inactivation by chemical agents has led to changes in recommendations regarding the reprocessing of instruments including flexible endoscopes. One of the changes is the preference for peracetic acid instead of glutaraldehyde in order to avoid fixation of organic material, but the surface fixation by various active agents has not been fully investigated. We used a standardized amount of dried blood soil on metal carriers (on average 22 mg). One part of the carriers was exposed to different disinfectants (four based on peracetic acid, three based on glutaraldehyde, two based on quaternary ammonium compounds (QAC), one based on QAC and amines, one based on phenols and one cleaning agent) and air dried. The difference compared with the non-exposed soiled carrier was taken as the measure of blood removal by exposure to the disinfectants. In addition the other part of the carriers was exposed to a cleaning agent and air dried. The cleaning agent itself was capable of removing more than 99% of the dried blood and served as a control for non-fixation. The rate of fixation of dried blood was calculated as the ratio of the weight of residual soil on 'soiled, disinfected and cleaned' carriers and on 'soiled and disinfected' carriers. All experiments were repeated eight times. Blood removal varied between 90.3% +/- 1.5% (phenol-based disinfectant) and < 10% (glutaraldehyde-based preparations). Fixation of the remainder was between 76.9 +/- 8.4% and 102.5 +/- 1.1% with glutaraldehyde and between 19.2% +/- 3.3% and 78.1% +/- 2.4% with peracetic acid. No other preparations showed a potential for blood fixation (< 1.3%). Our findings underline the potential for blood fixation, not only by glutaraldehyde, but also by peracetic acid, and support the evidence that effective cleaning should precede the chemical disinfection.

Blood↗

PubMed2006

[Mechanisms of removing red tide organisms by organo-clays].

We tested the influence of the preparation conditions of the quaternary ammonium compounds (QACs) modified clays on their capacities to remove red tide organisms, then discussed the mechanisms of the organo-clays removing red tide organisms. Hexadecyltrimethylammonium (HDTMA) improved the capacity of clays to flocculate red tide algae, and the HDTMA in metastable state enhanced the toxicity of the clay complexes to algae. The capacities of the organo-clays correlated with the toxicity and the adsorbed amount of the QACs used in clays modification, but as the incubation time was prolonged the stability of the organo-clays was improved and the algal removal efficiencies of the clay complexes decreased. When the adsorbed HDTMA was arranged in different clays in which the spatial resistance was different, there was more HDTMA in metastable state in the three-layer montmorillonite. Because of the homo-ion effect the bivalent or trivalent metal ions induced more HDTMA in metastable state and the corresponding organo-clays had high capacities to remove red tide organisms. When the reaction temperature was 60 degrees C the adsorbed HDTMA was easily arranged on cation exchange sites, if the temperature rose or fell the metastable HDTMA would increase so that the capacity of the clays was improved.

Adsorption↗

PubMed1987

Gastrointestinal transit rate-related absorption of emepronium: a study in mice.

The gastrointestinal (GI) absorption in mice of the anticholinergic quaternary ammonium compound emepronium, assessed by the urinary excretion of radioactivity and unchanged drug, increased from 1% to 7% and from 0.5% to 5%, respectively, in the dose range 0.1 to 40 mg/kg, whereafter a plateau was reached. Changes in the metabolism were evident at doses exceeding 80 mg/kg when 80% of the radioactivity was excreted as unchanged emepronium, as compared to 50% at lower doses. No dose-dependent urinary excretion of radioactivity was detected following intravenous injection. The increase in the fraction of the dose excreted in the urine after oral administration therefore cannot be easily explained by a dose-dependent metabolism or renal excretion. However, a relationship was seen between the reduced gastrointestinal motility, produced by increasing doses of the drug, and the increased bioavailability. Atropine sulphate given subcutaneously (1-50 mg/kg) more than doubled the urinary recovery of a small pharmacologically inactive oral dose of emepronium (5 mg/kg) and thus confirmed the transit rate-dependent absorption of emepronium. The superimposed effect of the pharmacological action on the GI transit rate, derived from the inherent property of an anticholinergic drug, may be of special significance for a drug with a low degree of absorption and a high variability, such as has been observed in clinical trials with the quaternary drug emepronium (Cetiprin).

Animals↗

PubMed2005

Characterization of cationic liposomes based on dimethyldioctadecylammonium and synthetic cord factor from M. tuberculosis (trehalose 6,6'-dibehenate)-a novel adjuvant inducing both strong CMI and antibody responses.

Incorporation of the glycolipid trehalose 6,6'-dibehenate (TDB) into cationic liposomes composed of the quaternary ammonium compound dimethyldioctadecylammonium (DDA) produce an adjuvant system which induces a powerful cell-mediated immune response and a strong antibody response, desirable for a high number of disease targets. We have used differential scanning calorimetry (DSC) to investigate the effect of TDB on the gel-fluid phase transition of DDA liposomes and to demonstrate that TDB is incorporated into DDA liposome bilayers. Transmission Electron Microscopy (TEM) and cryo-TEM confirmed that liposomes were formed when a lipid film of DDA containing small amounts of TDB was hydrated in an aqueous buffer solution at physiological pH. Furthermore, time development of particle size and zeta potential of DDA liposomes incorporating TDB during storage at 4 degrees C and 25 degrees C, indicates that TDB effectively stabilizes the DDA liposomes. Immunization of mice with the mycobacterial fusion protein Ag85B-ESAT-6 in DDA-TDB liposomes induced a strong, specific Th1 type immune response characterized by substantial production of the interferon-gamma cytokine and high levels of IgG2b isotype antibodies. The lymphocyte subset releasing the interferon-gamma was identified as CD4 T cells.

Acyltransferases↗

PubMed2002

Inactivation and removal of Bacillus cereus by sanitizer and detergent.

This study was conducted to compare the susceptibility of planktonic cells, attached single cells and biofilm cells of Bacillus cereus to sodium hypochlorite and Spartec, a quaternary ammonium compound (QAC). Removal of B. cereus biofilm by simulating clean-in-place (CIP) procedures employing 1.5% Spec-Tak 1000, an alkaline detergent; 0.65% Dilac, an acid detergent and 1.5% Diverform Plus, a sodium hypochlorite containing alkaline detergent was also examined. The results show that B. cereus cells in a biofilm were most resistant to chemical sanitizers followed by the attached single cell and cells in a planktonic state. When B. cereus cells were in a planktonic state, 25 ppm hypochlorite or 100 ppm QAC induced a more than 5.0 log CFU/ml reduction of cell numbers within 15 s. However, the same sanitizer used in this study showed little effect on cells in a biofilm even when the exposure time was extended to 5 min. The sanitizers tested were less effective against cells in biofilm formed on milk pre-soiled than on unsoiled stainless steel chips. It was also noted that Spec-Tak 1000 treatment at 70 degrees C for 10 min and water rinse in the first step of the long-hot CIP procedure can effectively remove the biofilm B. cereus cells from the milk pre-soiled stainless chip. With this long-hot CIP procedure, the biofilm cells of B. cereus were removed by ca. 6.10 log CFU/chip compared to ca. 1.47 log CFU/chip noted in the control procedure.

Bacillus cereus↗

PubMed2005

Deletion of pT181-like sequence in an smr-encoding mosaic plasmid harboured by a persistent bovine Staphylococcus warneri strain.

OBJECTIVES: The aim was to study the persistence and characteristics of Staphylococcus warneri strains resistant to quaternary ammonium compounds (QACs), including sequencing and analysis of two plasmids proved to carry the smr gene. METHODS: During a 3.5 year period quarter milk samples were collected on three occasions from all lactating cows in a dairy herd. The samples were screened with regard to QAC-resistant bacteria using a selective medium. Thirty randomly selected QAC-resistant S. warneri were typed by PFGE and subjected to plasmid isolation and analysis followed by gene detection using PCR. Two smr-containing plasmids in S. warneri isolates were sequenced. RESULTS: All isolates from the initial collection of quarter milk contained smr residing on a 5.8 kb plasmid (pSW174), which contained regions with high similarities to various plasmids, including pT181, pSK108 and pPI-2. The pT181-like sequence was flanked by 148 bp direct repeats, denoted ISLE49, with high similarity to previously reported sequences of approximately 148 bp, including ISLE39 flanking the insertion sequence IS257 in methicillin-resistant Staphylococcus aureus. All isolates from subsequent collections of quarter milk harboured a smaller smr-containing plasmid (pSW49). Sequence analyses revealed pSW49 (3552 bp) to be an in-part deleted version of pSW174 (5767 bp). CONCLUSIONS: The IS-associated elements found in this study may have a wider role in the integration and excision of DNA sequences in staphylococci than previously reported. The mosaic plasmid structure based on genetic elements of various origins contributes to further knowledge on the flexibility of smr-encoding plasmids.

Animals↗

PubMed2005

Widespread distribution of disinfectant resistance genes among staphylococci of bovine and caprine origin in Norway.

We demonstrate here a widespread distribution of genes mediating efflux-based resistance to quaternary ammonium compounds (QACs) in staphylococci from unpasteurized milk from 127 dairy cattle herds and 70 dairy goat herds. QAC resistance genes were identified in 21% of the cattle herds (qacA/B, smr, qacG, and qacJ) and in 10% of the goat herds (qacA/B and smr). Further examination of 42 QAC-resistant bovine and caprine isolates revealed the following genes: qacA/B (12 isolates) was present in four different species of coagulase-negative staphylococci (CoNS), smr (27 isolates) was detected in eight different CoNS species and in Staphylococcus aureus on a previously reported plasmid (pNVH99), qacG (two isolates) was detected on two plasmids (pST94-like) in Staphylococcus cohnii and Staphylococcus warneri, and qacJ (two isolates) was found in Staphylococcus hominis and Staphylococcus delphini on a plasmid (pNVH01) previously found in equine staphylococci. Isolation of indistinguishable pulsed-field gel electrophoresis (PFGE) CoNS types from tank milk and mammary quarter milk samples in a dairy cattle herd suggested that these QAC-resistant staphylococci were of intramammary origin. Indistinguishable or closely related PFGE types of bovine QAC-resistant CoNS were observed in different herds. One particular bovine S. warneri PFGE type was isolated repeatedly from samples collected during a 30-month period in a herd, showing long-term persistence. In conclusion, it seems that the widespread distribution of staphylococci carrying QAC resistance genes in Norwegian dairy cattle and goat herds is the result of both the intra- and interspecies spread of QAC resistance plasmids and the clonal spread of QAC-resistant strains.

Animals↗

PubMed2004

Effects of quaternary-ammonium-based formulations on bacterial community dynamics and antimicrobial susceptibility.

Quaternary ammonium compounds (QACs) are widely used as adjuncts to hygiene in domestic cleaning products. Current concern that the increased use of such biocides in consumer products might contribute to the emergence of antibiotic resistance has led us to examine the effects of a QAC-containing domestic cleaning fluid on the population dynamics and antimicrobial susceptibility of domestic sink drain biofilm communities. QAC susceptibilities of numerically dominant, culturable drain bacteria (15 genera, 17 species) were determined in vitro before and after repeated QAC exposure (14 passages). A fully characterized drain microcosm was then exposed to short-term (12 days) and long-term (3 months) dosing with a QAC-containing domestic detergent (QD). QAC exposure of isolated cultures caused both increases (three species) and circa twofold decreases (six species) in QAC susceptibility. The susceptibility of Ralstonia sp. was considerably decreased following 14 consecutive QAC passages. Control drain microcosm biofilms maintained dynamic stability, as evidenced by culture and denaturing gradient gel electrophoresis (DGGE) analysis. Bacterial population densities were largely unaffected during short-term exposure to use levels of QD, although 50% QD caused circa 10-fold viability reductions. DGGE analysis supported these observations; identified the major microcosm genera as Pseudomonas, Pseudoalteromonas, Erwinia, and Enterobacter, and showed that aeromonads increased in abundance under 10 to 50% QD. Long-term exposure of the microcosms to QD did not significantly alter the pattern of antimicrobial susceptibility. These data demonstrate the recalcitrance of domestic drain biofilms toward QAC and that although repeated QAC exposure of drain isolates in pure culture results in susceptibility change in some test bacteria, such changes do not necessarily occur within complex communities.

Anti-Bacterial Agents↗

PubMed2004

Molecular epidemiology and disinfectant susceptibility of Listeria monocytogenes from meat processing plants and human infections.

We have investigated the molecular epidemiology of Listeria monocytogenes from the meat processing industry producing cold cuts and from cases of human listeriosis by discriminative pulsed-field gel electrophoresis (PFGE). A subset of the isolates was also investigated for susceptibility to a disinfectant based on quaternary ammonium compounds (QAC) frequently used in the meat processing industry. The purpose of this investigation was to obtain knowledge of sources, routes of contamination and genetic types of L. monocytogenes present along the production line in the meat processing industry, and to compare meat industry isolates and human isolates. Of the 222 isolates from four meat-processing plants, 200 were from two plants responsible for nearly 50% of the production of cold cuts in the Norwegian market. The strain collection included historical routinely sampled isolates (1989-2002) and isolates systematically sampled through a one year period (November 2001 to November 2002) from fresh meat and production environments in three plants. No isolates were obtained in samples from employees (throat, faeces). Human strains included all available reported isolates from Norwegian patients in selected time periods. The L. monocytogenes PFGE data showed a large genetic heterogeneity, with isolates separated into two genetic lineages and further subdivided into 56 different PFGE profiles. Certain profiles were observed on both sides of production (before and after heat treatment) indicating contamination of end products by fresh meat or fresh meat environments. While fresh meat isolates almost exclusively grouped within lineage I, isolates from end products showed a more balanced distribution between lineages I and II. Ten profiles were common among isolates from human and meat industry. Typing of human isolates identified a previously unrecognised outbreak. Generally, a higher QAC resistance incidence was observed among isolates from the meat processing industry than among human isolates although large plant to plant differences were indicated. No correlation between resistance and PFGE profile or resistance and persistence was observed.

Animals↗

PubMed1998

Bacterial penetration into eggs washed with various chemicals and stored at different temperatures and times.

Eggs were washed with one of three commercial egg-washing chemicals, including a quaternary ammonium compound (QAC, pH 7.5), sodium carbonate (Na2CO3, pH 12), and sodium hypochlorite (NaOCl, 100 ppm, pH 7.5). One hundred fifty intact-shell eggs were washed at 43.3 degrees C with each of three chemicals. A control group was washed with tap water (H2O, pH 7.0). The washed eggs then were inoculated by immersion for 3 min into an aqueous suspension of Salmonella enteritidis at 10(4) colony-forming units/ml and dried for 30 min. The washed and inoculated eggs were stored at 4 degrees C or 23 degrees C, and bacterial penetration was checked at 0-, 7-, 14-, and 21-day intervals. The effects of egg-washing chemicals on microstructural changes of eggshell and postwash inoculation were examined using electron microscopy and conventional culture methods. Fifteen eggs were used in each sample. The results of microbial tests showed that both QAC and sodium hypochlorite treatments reduced bacterial penetration (less than 3.4% and 6.7%, respectively, on day 1 and 16.7% on day 21). The sodium carbonate treatment facilitated bacterial penetration during egg storage (less than 30% on day 1 and 76.7% on day 21). The eggs washed with tap water had a bacterial penetration rate of less than 6.7% on day 1 and 20% on day 21. As the storage intervals increased to 21 days, the bacterial penetration rate increased. Different storage temperatures (4 degrees C and 23 degrees C) did not cause a significant difference in bacterial penetration rates within 21-day interval. The results of electron microscopy showed that QAC and sodium hypochlorite at 100 ppm resulted in microbiologically clean eggs and did not destroy eggshell surfaces, which protected the eggs against future bacterial recontamination. The alkaline sodium carbonate produced visually clean eggs but altered the eggshell surface, which allowed bacterial recontamination.

Animals↗