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PubMed1998

Chilling and trimming effects on the microbial populations of pork carcasses.

The effects of chilling (normal chill or freeze chill) and trimming (hot fat trim or no fat trim) on the microbial populations of pork carcases were evaluated. In a two-part study, composited ham, loin, belly, and shoulder samples from 30 park carcasses had similar aerobic plate counts, averaging 5.5 log10 CFU/cm2. The nofat trim, normal chill procedure typically used in the industry, however, produced higher coliform and Staphylococcus spp. counts (P < 0.05). The hot fat trim, freeze chill treatment had the lowest lactic acid bacteria counts. Only 1 sample in 60 tested positive for Salmonella spp. Vacuum-packaged hams and loins stored at 4 degrees C for 14 days had similar (P > 0.05) aerobic plate counts, lactic acid bacteria and Staphylococcus spp. counts regardless of trim, chill, or the location of treatment, averaging 5.7, 6.3 and 1.4 log10 CFU/cm2, respectively. Hams had higher counts than loins all three days; however, only the difference on day 2 was significant. The desire to reduce microbial populations on pork carcasses as a food-safety issue and the coming implementation of hazard analysis critical control points (HACCP) programs warrants the use of trimming and chilling methods as critical control points or good manufacturing practices and standard operating procedures in the pork slaughter, processing, and packaging industry.

Abattoirs↗

PubMed2003

Efficacy of a commercial produce wash on bacterial contamination of lettuce in a food service setting.

Many microorganisms (including a number of important foodborne pathogens) can be present on raw fruits and vegetables. Since these products are frequently eaten raw, any pathogens present represent a potential risk to the consumer. The objective of this study was to compare the efficacy of a commercial produce wash with that of water for reducing the total bacterial population on lettuce when used by food service employees in university dining halls. Because this study was carried out in actual food service facilities during their daily operation, we used indigenous produce microflora instead of actual pathogens. Over the course of the study, more than 40 heads of lettuce were divided into thirds, and each section was analyzed for total plate count either before washing, after washing in water, or after washing in Victory produce wash. When initial contamination levels were > or = 100 CFU/g (n = 36 samples), reductions obtained with Victory produce wash (1.8 log CFU/g) were significantly larger (P = 0.0006) than those obtained with water (0.8 log CFU/g). Our results indicate that Victory produce wash is effective in reducing indigenous flora on lettuce during food service preparation. Our results also show that care must be taken in the analysis of microbial reduction data: only a slight reduction in total plate count (ca. 0.1 log CFU/g) and no significant difference in reductions (P = 0.84) were observed when all samples (irrespective of initial contamination level) were compared.

Bacteria↗

PubMed2000

The influence of sulfate-reducing bacteria colonization of 2 different bioresorbable barrier membranes for GTR. An 18-month case-controlled microbiologic and clinical study.

The purpose of the present microbiologic and case-controlled clinical study was to examine the colonization of 2 different resorbable barrier membranes by sulfate-reducing bacteria (SRB). The barrier membranes tested were Guidor matrix barrier and Resolut regenerative material. Ten patients exhibiting 3 Class II furcation defects and 7 intrabony defects were included in the study. The probing depth and the clinical attachment level at 4 surfaces per tooth were taken at the beginning of the study. Microbiologic samples were taken from the experimental sites and from the approximal sites of the adjacent teeth. Both types of resorbable membranes were positive for SRB colonization. The detection of SRB in 2 of 7 intrabony defects and in all defects with furcation involvement before the membrane placement indicated that these organisms are a common inhabitant of sites showing periodontal destruction and are associated with guided tissue regeneration (GTR). According to the clinical criteria for healing tendencies used in this study, the GTR procedures were less successful in the presence of SRB. There were no significant clinical effects of different resorbable membrane materials or membrane layout on attachment level changes for either the intrabony defect or furcation groups after 18 months. There were no statistical differences for sites that became exposed to SRB when compared to sites that remained unexposed after 18 months. The numeric significance of SRB in relation to the total microbial count needs to be determined to gain insight into the ecologic role of membrane resorption rates.

Absorbable Implants↗

PubMed1995

The effect of olestra on breath gas production and faecal microbial counts.

OBJECTIVE: To assess the effect of olestra consumption on breath hydrogen (H2) and methane (CH4) production and faecal microbial counts in humans consuming moderate or high fibre diets. A secondary objective was to assess the effect of olestra consumption on health status. DESIGN: Thirty-six-day parallel, placebo-controlled, double-blind study with baseline low fibre period (3 g/meal, 8 days) and treatment period (28 days). Four treatment groups: moderate (7 g/meal) or high fibre (24 g/meal), with olestra (24 g) or placebo. SETTING: Queen Margaret College, Edinburgh, Scotland. SUBJECTS: Ninety-seven adult subjects (30 males and 67 females) from the hospital staff and student population participated in the study. Ninety-four subjects successfully completed the study. INTERVENTION: Breath H2 and CH4 production were measured and faecal specimens were obtained for faecal microbial viable counts and direct microscopic cell counts at the end of the baseline period and the end of the treatment period. Standard clinical blood and urine assays were performed. Subjects were questioned regarding adverse events. RESULTS: Olestra demonstrated no significant effect on breath H2 or CH4 production following either moderate or high fibre intake. A trend for lower breath H2 production in the high fibre olestra group was seen. No effect of olestra consumption on faecal microbial counts or health status was observed. CONCLUSION: In normal subjects 24 g/d of olestra for 36 days does not interfere with normal intestinal fermentation of dietary fibre and does not significantly alter gut microflora populations.

Adult↗

PubMed2003

Effect of anti-CD14 monoclonal antibody on clearance of Escherichia coli bacteremia and endotoxemia.

OBJECTIVE: To determine the effects of an anti-CD14 monoclonal antibody on the clearance of a bacteremic Escherichia coli challenge in the presence or absence of antimicrobial agents. DESIGN: Prospective randomized animal study. SETTING: University-affiliated research laboratory. SUBJECTS: New Zealand White rabbits weighing 1.5-2.5 kg. INTERVENTIONS: Animals were pretreated with either an anti-lapine CD14 monoclonal antibody (immunoglobulin G2a, 5 mg/kg intravenously) or an isotype control monoclonal antibody. The animals then were challenged with 1 x 10(6) E. coli 018:K1 in the presence or absence of ceftazidime (50 mg/kg intravenously). There were four groups of six animals randomized to receive either anti-CD14 monoclonal antibody without ceftazidime, isotype control monoclonal antibody without ceftazidime, anti-CD14 monoclonal antibody with ceftazidime, or isotype control antibody with ceftazidime. MEASUREMENTS AND MAIN RESULTS: Serial measurement of quantitative bacteremia and endotoxemia was performed over 24 hrs after the administration of the bacterial challenge. Animals also underwent necropsy with quantitative bacterial cultures from multiple organ tissue samples. The anti-lapine CD14 monoclonal antibody significantly impaired the bloodstream clearance of E. coli (p <.01) and increased quantitative counts of E. coli in tissue culture samples when compared with isotype control antibody in the absence of simultaneous administration of ceftazidime. No differences in quantitative bacteremia, endotoxemia, or organ tissue counts were found after anti-CD14 antibody and control antibody-treated animals in the presence of ceftazidime treatment. CONCLUSIONS: Anti-CD14 monoclonal antibody has the capacity to interfere with the innate immune response and systemic microbial clearance in experimental animals with E. coli bacteremia. The concomitant administration of effective antimicrobial therapy eliminated differences in the rate of microbial clearance between the control antibody and the CD14 monoclonal antibody. These results indicate that care should be taken in clinical trials with anti-CD14 monoclonal antibodies to ensure that adequate antimicrobial therapy is administered in the presence of systemic bacterial infection.

Animals↗

PubMed2006

Investigating the heterogeneity of cell growth in microbial colonies by FTIR microspectroscopy.

Microorganisms rarely occur as individual cells in nature and are, instead, organized in complex multicellular communities such as colonies, fruiting bodies, or biofilms. Interest in the natural microbial life-style has increased during the last decade and a whole plethora of techniques has been used to gain insight into the development, structure and composition of diverse microbial communities. We have developed a technique for investigating the spatial heterogeneity of microbial growth in macro-colonies which essentially entails excision of the colonies with the underlying agar, freezing and subsequent cryotoming of the colonies, then FTIR microspectroscopic mapping of the cryosections. Colonies from Legionella, Bacillus, and Candida strains were chosen as model systems of multi-cellular communities to evaluate the technique. The results obtained indicate pronounced cell population heterogeneity even in relatively young colonies cultivated under laboratory conditions. Spectral data obtained from different positions within, e.g., a colony of Legionella bozemanii 120 h old indicated that levels of the storage material poly-beta-hydroxybutyric acid were significantly higher in cells at the surface of the colonies than in those growing at the bottom next to the agar surface. Similarly, in a 24-h-old macro-colony of Bacillus megaterium significantly more of the capsular compound polyglutamic acid was detected in upper layers than in deeper layers of the colony. Results demonstrate that FTIR microspectroscopy can be an useful tool for investigation of the spatial heterogeneity of cell growth within microbial macro-colonies. It is suggested that the method also can be adapted to the analysis of more complex multicellular communities, for example fruiting bodies, biofilms, or colonies growing under natural conditions.

Bacterial Physiological Phenomena↗

PubMed2002

Effects of diacetyl and carbon dioxide on spoilage microflora in ground beef.

The effect of CO2 and diacetyl, alone or in combination, on spoilage microflora in ground beef was determined. Ground beef was treated with 20, 30, or 40% CO2 for 22 days (study I); 20, 50, or 100 microg/g diacetyl for 26 days (study II); or a combination of 20% CO2 and 100 microglg diacetyl for 40 days (study III). Antimicrobial effectiveness was determined by aerobic plate counts (log10 CFU/g) using plate count agar (total aerobic bacteria), deMan Rogosa Sharpe (MRS) Lactobacillus agar (gram-positive bacteria), MacConkey agar (gram-negative bacteria), pH, and informal organoleptic assessments (by appearance and by odor). In study I, total bacteria and pH increased by day 4 in control meat samples. For all CO2 levels, gram-negative bacteria decreased and gram-positive bacteria increased compared with untreated controls. The pH remained constant for CO2-treated meat. Control samples had an off-odor and a brown appearance, while CO2-treated samples had no off-odor but did have a brown appearance. For samples treated with diacetyl (study II), spoilage was evident by day 7 for samples treated with 0, 20. and 50 microg/g diacetyl for all parameters examined. Ground beef treated with 100 microg/g diacetyl was spoiled on day 12. Diacetyl was detected (by odor) in samples that were treated with 100 microg/g diacetyl and had a brown appearance. Meat samples treated with the combination of CO2 and diacetyl (study III) showed that the addition of diacetyl did not have an additive effect on microbial growth. Combination-treated meat maintained a red appearance and no off-odor. Diacetyl and CO2 could be used in combination to maintain a red color and inhibit spoilage microorganisms.

Animals↗

PubMed1995

Controlling microbial contamination on beef and lamb meat during processing.

The microbiological quality of carcases, meat and environmental surfaces was evaluated in commercial boning rooms processing beef and lamb. There was considerable variation in the level of microbial contamination on both carcases and meat, with counts ranging from less than 20 to 10(8)/cm2 on carcases and to 2 x 10(7)/cm2 on meat. The level of microbial contamination on meat was influenced by the level of carcase contamination at boning and by the boning process itself. Carcase contamination was the major determinant of microbiological quality, as more than 70% of carcase had microbial counts greater than 10(3)/cm2. Cutting boards were a major source for microbial dissemination during boning, particularly when carcase counts were less than 10(3)/cm2. If carcases were heavily contaminated, the contamination of processing surfaces was irrelevant in determining microbial loads on meat. Where carcase contamination was at low to moderate levels, the contribution of the boning process to the contamination on meat assumed increased significance. Under these conditions, improved sanitation of cutting surfaces in the boning room resulted in a significant reduction in microbial contamination on the surface of meat. These results can form the basis for ensuring that improvements made in carcase management before boning, to improve microbiological quality, will be preserved through attention to cutting board hygiene during boning.

Animals↗

PubMed1992

The effects of antimicrobial acrylic strips on the subgingival microflora in chronic periodontitis.

This study investigated the effects of root planing and/or the placement of acrylic strips containing chlorhexidine, metronidazole or tetracycline on the composition and antimicrobial susceptibility of the subgingival flora in chronic periodontitis. 101 periodontal pockets from 73 patients were entered into 6 treatment groups which were, chlorhexidine, metronidazole or tetracycline strips, root planing, root planing followed by metronidazole strips and a control, no treatment group. Total anaerobic counts and anaerobe/aerobe ratios were estimated from samples taken before treatment and 1, 2, 4, 8 and 12 weeks after treatment. In addition, a more detailed analysis of the effects of the treatments on the subgingival flora was carried out on 12 pockets in 12 patients. Tetracycline strips, metronidazole strips and root planing and metronidazole strips were more effective than chlorhexidine strips in causing reductions in total anaerobic count and anaerobe/aerobe ratio. However, the changes in microbial parameters rebounded to approach baseline levels 4 weeks after treatment. Chlorhexidine caused no detectable changes in the composition of the subgingival microflora, while metronidazole had a variable effect. Tetracycline appeared to effect major shifts in the composition of the microflora of treated pockets but caused a marked selection of tetracycline-resistant organisms.

Acrylic Resins↗

PubMed2004

Influence of fruit variety, harvest technique, quality sorting, and storage on the native microflora of unpasteurized apple cider.

Apple variety, harvest, quality sorting, and storage practices were assessed to determine their impact on the microflora of unpasteurized cider. Seven apple varieties were harvested from the tree or the ground. The apples were used fresh or were stored at 0 to 4 degrees C for < or = 5 months and were pressed with or without quality selection. Cider yield, pH, Brix value, and titratable acidity were measured. Apples, postpressing apple pomace, and cider samples were analyzed for aerobic bacteria, yeasts, and molds. Aerobic bacterial plate counts (APCs) of ciders from fresh ground-picked apples (4.89 log CFU/ml) were higher than those of ciders made from fresh, tree-picked apples (3.45 log CFU/ml). Quality sorting further reduced the average APC to 2.88 log CFU/ml. Differences among all three treatment groups were significant (P < 0.0001). Apple and pomace microbial concentrations revealed harvest and postharvest treatment-dependent differences similar to those found in cider. There were significant differences in APC among apple varieties (P = 0.0001). Lower counts were associated with varieties exhibiting higher Brix values and higher titratable acidity. Differences in APC for stored and fresh apples used for cider production were not significant (P > 0.05). Yeast and mold counts revealed relationships similar to those for APCs. The relationship between initial microbial load found on incoming fruit and final cider microbial population was curvilinear, with the weakest correlations for the lowest apple microflora concentrations. The lack of linearity suggests that processing equipment contributed to cider contamination. Tree-picked quality fruit should be used for unpasteurized cider production, and careful manufacturing practices at cider plants can impact both safety and quality of the final product.

Beverages↗

PubMed2002

Phylogenetic analysis of the human gut microbiota using 16S rDNA clone libraries and strictly anaerobic culture-based methods.

The human gut microbiota from three healthy subjects were compared by the use of a sequence analysis of 16S rDNA libraries and a culture-based method. Direct counts ranged from 1.9 X 10" to 4.0 X 10" cells/g (wet weight), and plate counts totaled 6.6 X 10(10) to 1.2 X 10(11) CFU/g (wet weight). Sixty to seventy percent of the bacteria in the human intestinal tract cannot be cultured with currently available methods. The 16S rDNA libraries from three subjects were generated from total community DNA in the intestinal tract with universal primer sets. Randomly selected clones were partially sequenced. All purified colonies detected from the surface of the agar plate were used for a partial sequencing of 16S rDNA. On the basis of sequence similarities, the clones and colonies were classified into several clusters corresponding to the major phylum of the domain Bacteria. Among a total of 744 clones obtained, approximately 25% of them belonged to 31 known species. About 75% of the remaining clones were novel "phylotypes" (at least 98% similarity of clone sequence). The predominant intestinal microbial community consisted of 130 species or phylotypes according to the sequence data in this study. The 16S rDNA libraries and colonies included the Bacteroides group, Streptococcus group, Bifidobacterium group, and Clostridium rRNA clusters IV, IX, XIVa, and XVIII. Moreover, several previously uncharacterized and uncultured microorganisms were recognized in clone libraries and colonies. Our results also showed marked individual differences in the composition of intestinal microbiota.

Adult↗

PubMed2005

Adhesion of Pseudomonas aeruginosa and Staphylococcus epidermidis to silicone-hydrogel contact lenses.

PURPOSE: The purpose of this study is to compare the adhesion capabilities of the most important etiologic agents of microbial ocular infection to the recently available silicone-hydrogel lenses with those to a conventional hydrogel lens. METHODS: In vitro static adhesion assays of Pseudomonas aeruginosa 10,145, Staphylococcus epidermidis 9142 (biofilm-positive), and 12,228 (biofilm-negative) to two extended-wear silicone-hydrogel lenses (balafilcon A and lotrafilcon A), a daily wear silicone-hydrogel lens (galyfilcon A) and a conventional hydrogel (etafilcon A) were performed. To interpret the adhesion results, lens surface relative hydrophobicity was assessed by water contact angle measurements. RESULTS: P. aeruginosa and S. epidermidis 9142 exhibited greater adhesion capabilities to the extended wear silicone-hydrogel lenses than to the daily wear silicone- and conventional hydrogel lenses (p < 0.05). No statistical differences were found between the adhesion extent of these strains to galyfilcon A and etafilcon A. The biofilm negative strain of S. epidermidis adhered in larger extents to the silicone-hydrogel lenses than to the conventional hydrogel (p < 0.05), but in much lower amounts than the biofilm-positive strain. The water contact angle measurements revealed that the extended wear silicone-hydrogel lenses are hydrophobic, whereas the daily wear silicone- and conventional hydrogel lenses are hydrophilic. CONCLUSIONS: As a result of their hydrophobicity, the extended wear silicone-hydrogel lenses (lotrafilcon A and balafilcon A) may carry higher risk of microbial contamination than both the hydrophilic daily wear silicone-hydrogel lens, galyfilcon A and the conventional hydrogel lens, etafilcon A.

Bacterial Adhesion↗

PubMed2004

Atmospheric contamination during ultrasonic scaling.

OBJECTIVE: The aim of this study was to determine the microbial atmospheric contamination during initial periodontal treatment using a piezoelectric ultrasonic scaler in combination with either high-volume evacuation (HVE) or conventional dental suction (CDS). METHODS: The study included 17 treatment sessions, consisting of a 40-min episode of continuous plaque and calculus removal using an ultrasonic unit (EMS). The treatment sessions were carried out in six patients with generalized adult periodontitis and ranged from two to four sessions per patient according to their needs. The use of HVE and CDS was randomly assigned over the sessions within each patient. Before each treatment, the operating room was not used for 15 h. To measure baseline microbial air pollution two Petri dishes containing blood agar were exposed for 10 min to the air. At the start of each treatment session, two Petri dishes were exposed for 5 min at a distance of 40 cm from the mouth of the patients. After 20 min, this procedure was repeated. At a distance of 150 cm, two Petri dishes were exposed for 20 min followed by exposure of two new Petri dishes for the rest of the session. The plates were cultured aerobically and anaerobically for 3 and 7 days, respectively. RESULTS: The mean colony forming units (CFU) before treatment never exceeded 0.6 colonies per plate. At 40 cm, the mean CFU, when considering a period of 40 min, was 8.0 for HVE and 17.0 for CDS. The mean CFU at 150 cm during this period was 8.1 with HVE and 10.3 with the CDS. With reference to the Air Microbial Index the operatory atmosphere was considered to be in a good condition during 40 min of continuous use of the ultrasonic scaler in combination with both HVE and CDS. CONCLUSION: Within the restrictions of this study, only limited atmospheric microbial contamination is produced when using a piezoelectric ultrasonic scaler.

Adult↗

PubMed2004

Involvement of the lectin pathway of complement activation in antimicrobial immune defense during experimental septic peritonitis.

A critical first line of defense against infection is constituted by the binding of natural antibodies to microbial surfaces, activating the complement system via the classical complement activation pathway. In this function, the classical activation pathway is supported and amplified by two antibody-independent complement activation routes, i.e., the lectin pathway and the alternative pathway. We studied the contribution of the different complement activation pathways in the host defense against experimental polymicrobial peritonitis induced by cecal ligation and puncture by using mice deficient in either C1q or factors B and C2. The C1q-deficient mice lack the classical complement activation pathway. While infection-induced mortality of wild-type mice was 27%, mortality of C1q-deficient mice was increased to 60%. Mice with a deficiency of both factors B and C2 lack complement activation via the classical, the alternative, and the lectin pathways and exhibit a mortality of 92%, indicating a significant contribution of the lectin and alternative pathways of complement activation to survival. For 14 days after infection, mannan-binding lectin (MBL)-dependent activation of C4 was compromised. Serum MBL-A and MBL-C levels were significantly reduced for 1 week, possibly due to consumption. mRNA expression profiles did not lend support for either of the two MBL genes to respond as typical acute-phase genes. Our results demonstrate a long-lasting depletion of MBL-A and MBL-C from serum during microbial infection and underline the importance of both the lectin and the alternative pathways for antimicrobial immune defense.

Animals↗

PubMed1997

Efficacy of a chlorhexidine and a chlorhexidine-fluoride varnish mixture to decrease interdental levels of mutans streptococci.

The aim of the present study was to evaluate and compare the efficacy of a chlorhexidine/thymol-containing (CHX) and a chlorhexidine/thymol/fluoride-containing (CHX + F) varnish to decrease interdental levels of mutans streptococci (MS). Eighty-two healthy schoolchildren (11-13 years) with high scores of salivary MS were selected by a screening procedure and randomised into two groups. MS were enumerated at all mesial interdental sites of the first permanent molars with the aid of a modified chair-side technique. The interdental molar and premolar sites were treated with either a 1% CHX varnish (Cervitec) or a 1:1 mixture of the CHX varnish and a fluoride varnish containing 0.1% w/w difluorsilane (Fluor Protector; CHX + F) on two occasions within a 2-week period. The varnishes were applied with a small brush after cleaning with dental floss and drying with air. Follow-up samples from the interdental areas were collected after 1 and 3 months. Both groups exhibited a similar statistically significant (p < 0.05) reduction of interdental MS after 1 month when compared with baseline. After 3 months, a significant reduction (p < 0.05) was still found in the CHX + F varnish group but not in the CHX varnish group. In conclusion, the results suggest that the addition of fluoride to an antibacterial varnish might improve the long-term efficacy in diminishing the cariogenic microbial challenge. Thus, the mixed varnish concept should be further developed and warrants an implementation of clinical studies.

Adolescent↗

PubMed2001

Development of a multiple-step process for the microbial decontamination of beef trim.

A multiple-hurdle antimicrobial process for beef trim was developed. The microbial profiles of inoculated lean beef trim tissue (BTL) and fat-covered lean beef trim (BTF) were monitored during prolonged refrigerated storage following the application of successive multiple antimicrobial treatments applied to inoculated beef trim on a processing conveyor belt set at a belt speed of 1 cm/s. Beef trim (meat size approximately 15 by 15 cm) was preinoculated with bovine feces before all treatments that included the following: control, no treatment; water wash at 65 psi for five passes; water plus lactic acid (2% [vol/vol] room temperature lactic acid wash at 30 psi for three passes); combination treatment 1 (water plus 65 degrees C hot water at 30 psi for one pass plus hot air at 510 degrees C for four passes plus lactic acid), combination treatment 2 (water plus hot water at 82 degrees C for one pass plus hot air at 510 degrees C for five passes plus lactic acid), and combination treatment 3 (water plus hot water at 82 degrees C for three passes plus hot air at 510 degrees C for six passes plus lactic acid). The effects of treatments on bacterial populations were monitored by enumerating mesophilic aerobic bacteria (APC), presumptive lactic acid bacteria (PLAB), psychrotrophic bacteria (PCT), coliforms, and Escherichia coli biotype 1 on product stored for up to 7 days at 4 degrees C. In the case of BTL, the numbers of APC, PCT, and PLAB increased during storage at 5 degrees C, whereas the numbers of coliform and E. coli decreased on average by 1.8 log CFU/cm2, then remained constant following the initial reduction. Negligible effects on color quality were observed from multihurdle treatment combination 1. In the case of the BTF, the microbial reductions by treatments were much greater than the reduction on BTL. The pH of treated BTF increased more slowly than the pH of treated BTL, resulting in further reduction of the microflora on BTF. Except for control and water treatments, all sample treatments involving lactic acid resulted in continuously decreasing microbial populations. Based on microbial reduction and quality aspects, it was concluded that successively applied combination antimicrobial treatments for meat trim could offer potential food safety benefits.

Animals↗

PubMedDate not supplied

The expanded application of most probable number to the quantitative evaluation of extremely low microbial count.

This paper is about the evaluation of the extremely low microbial counts from the field by expanding the most probable number (MPN) methodology when the data follow Poisson distribution in order to achieve more accurate estimation with limited number of data. Several data sets with extremely low microbial counts from pharmaceutical clean room and laboratory clean bench monitoring were found with good Poisson distribution fitness by chi2 test (P < 0.05), and the MPN calculations were conducted for these data by using the Halvorson and Ziegler equation. The MPN values are generally larger than the arithmetic average, indicating a higher sensitivity of the data assay. This approach is justified because Poisson distribution is the mathematical background of the MPN procedure, with the Halvorson and Ziegler equation as its foundation. It is considered that the MPN methodology has a potential application for quality control in the extremely low level microbial counting environment in the clean rooms levels ISO class 7 or above. Further studies on the precision of this method and development of a sampling plan based on careful mathematical analysis will help to refine the approach.

Air Microbiology↗

PubMed2006

Endotoxin, (1 --> 3)-beta-D-glucans and fungal extra-cellular polysaccharides in New Zealand homes: a pilot study.

Bacterial endotoxin, fungal (1 --> 3)-beta-D-glucans, and extracellular polysaccharides from Aspergillus and Penicillium (EPS-Asp/Pen) have been suggested to be stable markers of microbial exposure. This paper describes a pilot study in which we measured endotoxin, (1 --> 3)-beta-D-glucans, EPS-Asp/Pen and mite allergen in house dust collected in 32 homes in Wellington, New Zealand. Endotoxin (GM 60,295 EU/g; GSD 2.4) and glucan (GM 2,687 microg/g; GSD 1.5) levels were higher in comparison to previous international studies, whereas EPS-Asp/Pen levels (37,347 Units/g; GSD 1.9) appeared comparable. Concentrations expressed per square meter were highly correlated among the measured components (p < 0.05). When expressed per gram of dust only (1 --> 3)- beta -D-glucans and EPS-Asp/Pen were correlated (r=0.55, p < 0.01; n=32). Endotoxin and glucan levels were higher (borderline statistically significant; p < 0.10) in homes with self-reported water damage. A positive association (p < 0.10) was also found for dust mite and a combination of self-reported mould, dampness and water damage. EPS levels were higher in homes where residents indicated the presence of mould spots on the wall, but this did not reach statistical significance. In conclusion, levels of microbial contaminants in a small random sample of New Zealand homes were high and weakly associated with water damage.

Air Pollution, Indoor↗