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The effect of growth atmosphere on the ability of Listeria monocytogenes to survive exposure to acid, proteolytic enzymes and bile salts.

Four isolates of Listeria monocytogenes from food, human and environmental sources were grown separately in broth (pH 6.0 at 8 degrees C) under atmospheres of air, 100% N(2), 40% CO(2):60% N(2) or 100% CO(2). Exponential and stationary phase cells were harvested to determine if growth atmosphere and growth phase influenced this pathogen's ability to survive exposure to an acid environment coupled with proteolytic enzymes, and the activity of bile salts. In general, isolates were more resistant to the acid environment than the bile salts environment and stationary phase cells were significantly more resistant to both environments than exponential phase cells. Irrespective of prior growth atmosphere, none of the isolates when in exponential phase remained detectable following full exposure to the acid environment (110 min at 37 degrees C) or the bile environment (3 h at 37 degrees C). With the exception of one isolate grown under the atmosphere of 40% CO(2):60% N(2), all isolates when in stationary phase were detectable following full exposure to the acid environment but death rates varied significantly. Stationary phase cells of all isolates grown under 40% CO(2):60% N(2) and 100% CO(2) were highly susceptible to the bile salts environment: cells were not detectable after a 2-min exposure whereas stationary phase cells grown under air or 100% N(2) were recovered following full exposure to the bile environment. Survival curves were characterised by a population decline of at least 3 log(10)/ml (from an initial level of 7 log(10) CFU/ml) in the first 15 min; thereafter a constant population number of approximately 4 log(10)/ml was maintained over the remaining exposure period. No survival was observed when stationary phase cells of L. monocytogenes FRRB 2538 grown in air and 100% N(2) were subjected to the acid environment followed by immediate exposure to the bile salts environment. The results showed that growth atmosphere and growth phase could influence survival of this pathogen against conditions that imitate the extremes of the most important nonspecific defence mechanisms against microbial infection: the acid environment of the stomach coupled with the activity of proteolytic enzymes, and the activity of bile salts in the small intestine.

Acids↗

Subgingival microbiota of periodontally untreated Mexican subjects with generalized aggressive periodontitis.

BACKGROUND AND AIM: Specific microbial profiles that may distinguish between generalized aggressive-periodontitis (GAgP) and generalized chronic-periodontitis (GCP) have, to date, not been described. The purpose of the present study was to describe the subgingival microbial composition of Mexican subjects with GAgP and compare it with that of individuals with GCP and periodontal health (PH). MATERIAL AND METHODS: Seventy-seven subjects with GAgP (n=19), GCP (n=39) and PH (n=19) were selected. Clinical measurements included plaque accumulation, gingival erythema, bleeding on probing, suppuration, pocket depth and attachment level. Up to 28 subgingival plaque samples were obtained from each subject and analysed using the checkerboard DNA-DNA hybridization technique. RESULTS: GAgP and GCP subjects harboured significantly higher levels and/or proportion of Porphyromonas gingivalis, Tannerella forsythia (levels: p<0.001, proportion: p<0.01), Prevotella nigrescens (p<0.05 levels) and "red" complex species (p<0.001 proportion) than PH subjects. All GAgP subjects were carriers of P. gingivalis and P. nigrescens. No significant differences in any of the 40 microbial species tested were detected between GAgP and GCP subjects. CONCLUSIONS: Our results revealed that the microbial differences between GAgP and GCP subjects were only discrete and none of the bacterial species tested seemed to specifically differentiate the subgingival microbial profile of either periodontitis group.

Actinomyces↗

Microbial diversity in bighorn sheep revealed by culture-independent methods.

We investigated the effectiveness of culture-independent molecular methods for determining host-associated microbial diversity in bighorn sheep (Ovis canadensis). Results from bacterial culture attempts have been the primary source of information on host-associated bacteria, but studies have shown that culture-based results significantly underestimate bacterial diversity in biological samples. To test the effectiveness of culture-independent methods, we extracted DNA from nasal and oropharyngeal swab samples collected from bighorn sheep in four different populations. From these samples, we amplified, cloned, and sequenced small subunit (16S) ribosomal DNA (rDNA) to identify the scope of microbial diversity in bighorn respiratory tracts. Phylogenetic analysis of these rDNA gene sequences revealed organismal diversity an order of magnitude higher than was determined by culture methods. Pasteurellaceae bacteria were the most diverse phylogenetic group in live bighorn sheep, and members of bacterial genera often associated with respiratory disease were found in all the samples. Culture-independent methods were also able to directly detect leukotoxin (lktA) gene sequences in swab and lung tissue samples. Overall, our results show the power of culture-independent molecular methods for identifying microbial diversity in bighorn sheep and the potential for these methods to detect the presence of virulence genes in biological samples.

Animals↗

The microbial outcome observed with polymerase chain reaction in subjects with recurrent periodontal disease following local treatment with 25% metronidazole gel.

The aim of this study was to evaluate the microbial outcome in patients with recurrent periodontal disease following treatment with 25% metronidazole gel using the polymerase chain reaction (PCR). Twenty subjects in a maintenance care program but with recurrent periodontal disease participated. Three months after scaling and root planing a total of 40 sites, 2 in each patient, with pocket probing depth of > or = 5 mm were selected. One site randomly selected was treated with 25% metronidazole gel (test) and the other site with a placebo gel (control). A bacterial sample was collected on paperpoint from each test and control site at baseline and 12 weeks after treatment. The following pathogens were analysed and detected with PCR:Actinobacillus actinomycetemcomitans (A.a.), Porphyromonas gingivalis (P.g.) and Prevotella nigrescens (P.n.). At baseline, A.a., P.g. and P.n. were detected in 30, 60 and 70% of all test sites and in 32, 58 and 21% of all control sites. There was a statistically significant difference between the test and control sites for P.n. at baseline. The major difference after treatment with 25% metronidazole gel was the increase of positive control sites for P.g. and P.n. However, there were no statistically significant differences in the occurrence rate of A.a., P.g. and P.n. at test and control sites after treatment. This study has shown that 25% metronidazole gel treatment did not seem to influence the microbial outcome, when PCR was used to analyse the presence/absence of A.a., P.g. and P.n. in this group of subjects with recurrent periodontal disease.

Adult↗

An evaluation of five protocols for surgical handwashing in relation to skin condition and microbial counts.

Five protocols for surgical handwashing (scrubbing) were evaluated for their efficiency of removal of micro-organisms and their drying effect on the skin. The scrubbing protocols tested were: (1) an initial scrub of 5 min and consecutive scrubs of 3.5 min with chlorhexidine gluconate 4% (CHG-5); (2) an initial scrub of 3 min and consecutive scrubs of 2.5 min with chlorhexidine gluconate 4% (CHG-3); (3) an initial scrub of 3 min and consecutive scrubs of 2.5 min with povidone iodine 5% and triclosan 1% (PI-3); (4) an initial scrub of 2 min with chlorhexidine gluconate 4% followed by a 30 s application of isopropanol 70% and chlorhexidine gluconate 0.5%, and a 30 s application of isopropanol 70% and chlorhexidine gluconate 0.5% for consecutive scrubs (IPA); and (5) an initial scrub of 2 min with chlorhexidine gluconate 4% followed by a 30 s application of ethanol 70% and chlorhexidine gluconate 0.5%, and a 30 s application of ethanol 70% and chlorhexidine gluconate 0.5% for consecutive scrubs (EA). A convenience sample of 23 operating theatre nurses completed each scrub protocol for one week in a randomized order. A week of normal work activities intervened between each protocol. Subjects were assessed before commencing and after completing the week of each protocol to determine changes in the microbial counts and skin condition of the hands. Specimens for microbial analysis were collected before, immediately after and 2 h after an initial scrub, and 2 h after a consecutive scrub. The CHG-5, CHG-3 and PI-3 protocols, which used detergent-based antiseptics only, were compared with protocols incorporating an alcohol-based antiseptic (IPA and EA). The protocols incorporating alcohol-based antiseptics and the CHG-5 protocol were generally associated with the lowest post-scrub numbers of colony forming units (cfu). No difference between the CHG-5 protocol and the alcohol-based antiseptics was found at the beginning of the test week, but after exclusive use of the respective protocols for a week, the alcohol-based antiseptics were associated with significantly lower cfu numbers in two out of the three post-scrub samples (P = 0.003, P = 0.035). Although virtually no statistically significant differences in skin condition were found, many subjects reported the alcohol-based antiseptic protocols to be less drying on the skin. The findings of this study support the proposition that a scrub protocol using alcohol-based antiseptics is as effective and no more damaging to skin than more time-consuming, conventional methods using detergent-based antiseptics.

1-Propanol↗

Effect of broiler age, feed withdrawal, and transportation on levels of coliforms, Campylobacter, Escherichia coli and Salmonella on carcasses before and after immersion chilling.

A study was conducted to determine effects of bird age at slaughter, feed withdrawal, and transportation on levels of coliforms, Campylobacter, Escherichia coli, and Salmonella on carcasses before and after immersion chilling. Broilers were processed at 42, 49, and 56 d of age after a 12-h feed withdrawal period or a 0-h feed withdrawal period (full fed). At each age, broilers were processed from two commercial farms previously identified as Campylobacter positive. One week before slaughter, broilers were gavaged with nalidixic acid-resistant Salmonella. During bleeding, cotton plugs were inserted into the cloaca of each carcass. Whole-carcass rinses (WCR) were performed before and after immersion chilling with 20 ppm sodium hypochlorite, and rinses were analyzed for coliforms, Campylobacter, E. coli and Salmonella. Log10 counts for coliforms, Campylobacter, and E. coli were (P < 0.05) affected by bird age at slaughter. Feed withdrawal (FW) affected only Campylobacter on carcasses of older broilers (56 d of age). Chilling with sodium hypochlorite resulted in log10 reductions of 1.2, 1.3, 1.4, and 0.5 for coliforms, Campylobacter, E. coli, and Salmonella, respectively. Under the conditions of this experiment, it appears that contamination on the exterior of birds entering the processing facility is critical to carcass bacterial counts. Moreover, carcass bacterial counts did not vary when microbial counts of broilers were comparable. FW may increase prechill carcass counts for E. coli and Campylobacter, but it appears to have no effect on postchill carcass counts when sodium hypochlorite is used in the chilling operation.

Aging↗

Plaque pH and microflora of dental plaque on sound and carious root surfaces.

Given the hypothesis that root caries is the result of acid formation by acidogenic micro-organisms, the present study was performed to relate sucrose-induced pH response of dental plaque on root surfaces to the microbial composition of the overlying plaque. Seventeen caries-active elderly Chinese with poor oral hygiene and with both sound and carious root surfaces were examined. Plaque pH was measured before and up to one hour after a controlled sucrose mouthrinse. Plaque samples for microbiologic analyses were collected from 2 sound and 2 or 3 carious pH-measurement sites in each subject. The prevalence of the following micro-organisms was assessed as % of total viable counts on Brucella agar: Prevotella intermedia, Prevotella melaninogenica, Fusobacterium nucleatum, Campylobacter rectus, Capnocytophaga spp., Actinomyces viscosus, Actinomyces naeslundi, Streptococcus spp., S. sanguis, S. mitis, S. mutans, S. sobrinus, Lactobacillus spp., and Candida spp. There was no difference in plaque pH response on sound and carious root surfaces. The plaque pH response was more pronounced in the maxilla than in the mandible for both sound and carious sites. There was no difference in microbial composition of dental plaque on sound and carious root surfaces. The pH response to sucrose was the same regardless of the presence or absence of mutans streptococci. Our results thus do not readily support the traditional concept of caries formation.

Aged↗

Combined effects of lactic acid and nisin solution in reducing levels of microbiological contamination in red meat carcasses.

Changes in bacterial counts on beef carcasses at specific points during slaughter and fabrication were determined, and the effectiveness of nisin, lactic acid, and a combination of the lactic acid and nisin in reducing levels of microbiological contamination was assessed. Swab samples were obtained from the surfaces of randomly selected beef carcasses. Carcasses were swabbed from the neck, brisket, and renal site after skinning, splitting, and washing. Treatments involving lactic acid (1.5%), nisin (500 IU/ml), or a mixture of nisin and lactic acid were applied after the neck area was washed. A control group was not sprayed. Results indicated that the highest prevalence of aerobic plate counts (APCs), total coliforms, and Escherichia coli was found in the neck site after splitting, and the lowest level of microbial contamination was found after skinning. Washing with water did not significantly reduce the bacterial load. The largest reduction in APCs, total coliforms, and E. coli occurred on carcasses treated with a mixture of nisin and lactic acid. A mixture of nisin and lactic acid can be applied to beef carcasses through spray washing and can reduce bacterial populations by 2 log units.

Animals↗

The effect of surgical handwashing routines on the microbial counts of operating room nurses.

Many factors may affect the efficiency of handwashing techniques. This study examined two interdependent factors: the time taken to wash the hands and the type of antiseptic solution used. A 3-minute initial scrub and 30-second consecutive scrub regimen was compared with a current standard regimen of a 5-minute initial scrub and a 3-minute consecutive scrub. Chlorhexidine gluconate 4% and povidone-iodine 7.5% were the antiseptics used in the two regimens. The sample (n = 34) was drawn from nurses employed in the operating room suite of a 950-bed hospital. Chlorhexidine gluconate was found to be responsible for lower numbers of colony-forming units of bacteria than povidone-iodine. The duration of the scrub had no significant effect on the numbers of bacteria when povidone-iodine was used. The optimal regimen was found to be the 5-minute initial and 3-minute consecutive scrubs with chlorhexidine gluconate.

Chlorhexidine↗

Exposure to bioaerosols: allergic reactions and respiratory function in Polish hop growers.

BACKGROUND: The aim of the study was to assess the prevalence of work-related symptoms in hop growers and their relation to bioaerosols exposure. The study group comprised 69 hop growers and 58 office workers as controls. The examination included: physician-administrated questionnaire, PEF measurements, skin prick test, agar-gel precipitation test, and migration inhibition test. Microbiological air sampling was performed on all farms. RESULTS: The concentrations of total airborne microflora ranged from 2.08 to 129.6 x 10(3) CFU/m3. Airborne endotoxin and dust concentrations ranged from 26 to 6250 ng/m3 and 0.2-31.7 mg/m3, respectively. Altogether 52.2% of farmers complained of work-related symptoms. Positive skin reactions to microbial allergens were significantly more frequent in a group of hop growers with work-related respiratory symptoms compared to the rest of the farmers (18% vs 2%, P <0.05). Positive reactions in agar-gel precipitation test and in the leukocyte migration inhibition test were not correlated with the occurrence of work-related symptoms. The mean daily PEF values in farmers were lower compared to controls (469.7 +/- 127.5 vs 562.9 +/- 123.8; P <0.001). PEF (amp%mean) was higher in farmers compared to controls (9.3% vs 8.1%; P <0.05). CONCLUSION: Despite relatively lower exposure to bioaerosols, compared to farmers in other branches of agriculture, over 50% of hop growers complained of work-related symptoms. This may be partly due to the effects of microbial allergens and toxins and partly to the irritant or allergic properties of hop plant itself.

Adolescent↗

Microorganisms associated with natural fermentation of Prosopis africana seeds for the production of okpiye.

Okpiye is a food condiment prepared by the fermentation of Prosopis africana seeds. The traditional process for the production and microbiological characteristics of the condiment were investigated. During laboratory fermentation that lasted 96 h, the mesquite seeds underwent a natural fermentation that was characterised by the growth of microorganisms to 10(6)-10(8) cfu/g. Several species of bacteria especially B. subtilis, B. licheniformis, B. megaterium, Staphylococcus epidermidis and Micrococcus spp were found to be the most actively involved organisms. However, significant contributions to the microbial ecology were made by Enterobacter cloacae and Klebsiella pneumoniae. Lactobacillus spp were present in low numbers towards the end of the fermentation. The presence of Proteus and Pseudomonas spp in traditional fermented samples demonstrate the variability which may exist in the microflora of individual fermented samples. Variations in the important microbial groups show that Bacillus spp were the most prevalent species and occurred until the end of fermentation. Temperature, pH and titratable acidity varied with time and were influenced by the metabolic activities of the microorganisms.

Bacillus↗

[Bone collected with a bone collector during dental implant surgery].

BACKGROUND: Simultaneous implantation and augmentation using autogenous bone collected during implant surgery is a well-established procedure in oral implantology. The aims of this study were (1) to identify any bacterial contamination of bone obtained with a bone collector, and (2) to verify the antimicrobial effect of rinsing the bone collector with a 0.1% chlorhexidine solution prior to augmentation. MATERIAL AND METHODS: A total of 39 patients undergoing a simultaneous implantation and augmentation procedure were examined. All patients rinsed their mouths with a 0.1% chlorhexidine solution for 2 min prior to surgery. Bone was collected with the Osseous Coagulum Trap, while saliva was collected with a separate suction tip. Once bone collection was complete a microbiological swab was taken from the bone collector (sample 1); before the bone was taken from it 200 ml of a 0.1% chlorhexidine solution was aspirated into the collector, after which the bone was removed and the collector sieve was (sample 2) sent for microbiological analysis which included aerobic and anaerobic cultivation of microorganisms and their identification and semiquantitative assessment of microbial growth. RESULTS: Before the collector was rinsed with chlorhexidine microbial contamination was found in 34 (82.7%) of the 39 samples, and 37 different microbial species were identified in cultures. When the collector had been rinsed with 200 ml 0.1% chlorhexidine a significantly lower rate of microbial contamination was found: 66.7% of the samples were sterile. CONCLUSIONS: Despite separate suction techniques for bone dust and saliva and preoperative use of a chlorhexidine mouthwash, bacterial contamination of bone obtained from the mouth with a bone collector has to be anticipated. Not only the physiological bacteria of the oral flora, but also the microorganisms frequently associated with implant failure can be found. Rinsing the bone collector with 200 ml of a 0.1% chlorhexidine solution significantly reduces microbial contamination. The effects on bone vitality must be studied before routine rinsing with chlorhexidine can be recommended.

Adult↗

In vivo antimicrobial activity of 2% chlorhexidine used as a root canal irrigating solution.

The aim of the present study was to evaluate the in vivo antimicrobial activity of 2% chlorhexidine gluconate (FCFRP-USP) used as a root canal irrigating solution in teeth with pulp necrosis and radiographically visible chronic periapical reactions. Culture techniques and measurement of the inhibition zone were used. Twenty-two root canals of incisors and molars of 12 patients were used. After accessing the canal, the first root canal sample was collected with two sterile paper points that were transferred to a tube containing reduced transport fluid. The root canal was instrumented using chlorhexidine solution. A small sterile cotton pellet was placed at the root canal entrance, and the cavity was sealed with zinc oxide-eugenol cement. The canals were maintained empty for 48 h. Three sterile paper points were then introduced to absorb the root canal fluid (second sample). One paper point was placed on an agar plate inoculated with Micrococcus luteus ATCC 9341 and incubated for 24 h at 37 degrees C, and the other two were submitted to microbiological evaluation. Present in 10 cases at baseline, mutans streptococci was reduced by 100% at the second assessment. Treatment showed an efficiency of 77.78% for anaerobic microorganisms at the second assessment. These data suggest that chlorhexidine prevents microbial activity in vivo with residual effects in the root canal system up to 48 h.

Adolescent↗

Evaluation of a simplified semi-quantitative protocol for the estimation of Vibrio vulnificus in bathing water using cellobiose-colistin agar: a collaborative study with 13 municipal food controlling units in Denmark.

A simplified semi-quantitative method using pre-enrichment in alkaline peptone water supplemented with polymyxin B and plating onto cellobiose-colistin (CC) agar for the estimation of Vibrio vulnificus in bathing water was evaluated. This protocol was tested in a collaborative study with 13 food controlling laboratories in Denmark during the 1999 bathing season in periods when water temperatures exceeded 20 degrees C. The average percentage of yellow colonies larger than 1 mm in diameter on CC agar that could be identified as V. vulnificus by colony hybridization with a species-specific DNA probe was 79%. This high percentage of specificity demonstrated that by using CC agar in estimating the level of V. vulnificus in bathing water, recognition of yellow colonies larger than 1 mm is sufficient for the identification of V. vulnificus with no further characterization needed. The simplified protocol may be included in the routine control of the microbial quality of bathing water done by the local food controlling laboratories, since it involves simple traditional and low-cost microbiological methods with no use of molecular skills or sophisticated equipment.

Baths↗

Reagentless detection of microorganisms by intrinsic fluorescence.

Quick and accurate detection of microbial contamination is accomplished by a unique combination of leading-edge technologies described in this and the accompanying paper. In this contribution, a hand-held prototype instrument is described which is capable of statistically sampling the environment for microbial contamination and determining cell viability. The technology is sensitive enough to detect very low levels ( approximately 20 cells/cm(2) or cm(3)) of microbes in seconds.

Bacteria↗

Microbial inactivation of paprika by a high-temperature short-X time treatment. Influence on color properties.

High-temperature short-time (HTST) treatments have been used to destroy the bioburden of paprika. With this in mind, we have designed a device to treat samples of paprika with a gas whose temperature, pressure, and composition can be selected. Temperatures and treatment times ranged from 130 to 170 degrees C and 4 to 6 s, respectively. The survival of the most commonly found microorganisms in paprika and any alteration in extractable and superficial color were examined. Data showed that the optimum HTST conditions were 145 degrees C, 1.5 kg/cm2 of overpressure, 6 s operation time, and a thermal fluid of saturated steam. No microbial growth was detected during storage after thermal treatment. To minimize the color losses, treated (HTST) paprika samples should be kept under refrigeration.

Capsicum↗

A national study on the residential impact of biological aerosols from the land application of biosolids.

AIMS: The purpose of this study was to evaluate the community risk of infection from bioaerosols to residents living near biosolids land application sites. METHODS AND RESULTS: Approximately 350 aerosol samples from 10 sites located throughout the USA were collected via the use of six SKC Biosamplers. Downwind aerosol samples from biosolids loading, unloading, land application and background operations were collected from all sites. All samples were analysed for the presence of HPC bacteria, total coliform bacteria, Escherichia coli, Clostridium perfringens, coliphage, enteroviruses, hepatitis A virus and norovirus. Total coliforms, E. coli, C. perfringens and coliphage were not detected with great frequency from any sites, however, biosolids loading operations resulted in the largest concentrations of these aerosolized microbial indicators. Microbial risk analyses were conducted on loading and land application operations and their subsequent residential exposures determined. CONCLUSIONS: The greatest annual risks of infection occurred during loading operations, and resulted in a 4 x 10(-4) chance of infection from inhalation of coxsackievirus A21. Land application of biosolids resulted in risks that were <2 x 10(-4) from inhalation of coxsackievirus A21. Overall bioaerosol exposure from biosolids operations poses little community risk based on this study. SIGNIFICANCE AND IMPACT OF THE STUDY: This study evaluated the overall incidence of aerosolized micro-organisms from the land application of biosolids and subsequently determined that microbial risks of infection were low for residents close to biosolids application sites.

Aerosols↗

Bacteriophage migration via nematode vectors: host-parasite-consumer interactions in laboratory microcosms.

Pathogens vectored by nematodes pose serious agricultural, economic, and health threats; however, little is known of the ecological and evolutionary aspects of pathogen transmission by nematodes. Here we describe a novel model system with two trophic levels, bacteriophages and nematodes, each of which competes for bacteria. We demonstrate for the first time that nematodes are capable of transmitting phages between spatially distinct patches of bacteria. This model system has considerable advantages, including the ease of maintenance and manipulation at the laboratory bench, the ability to observe many generations in short periods, and the capacity to freeze evolved strains for later comparison to their ancestors. More generally, experimental studies of complex multispecies interactions, host-pathogen coevolution, disease dynamics, and the evolution of virulence may benefit from this model system because current models (e.g., chickens, mosquitoes, and malaria parasites) are costly to maintain, are difficult to manipulate, and require considerable space. Our initial explorations centered on independently assessing the impacts of nematode, bacterium, and phage population densities on virus migration between host patches. Our results indicated that virus transmission increases with worm density and host bacterial abundance; however, transmission decreases with initial phage abundance, perhaps because viruses eliminate available hosts before migration can occur. We discuss the microbial growth dynamics that underlie these results, suggest mechanistic explanations for nematode transmission of phages, and propose intriguing possibilities for future research.

Animals↗