Reduction In Bacterial Numbers Research Articles

Lysis of tubercle bacilli in fresh and stored sputum specimens: implications for diagnosing tuberculosis in stored and paucibacillary specimens by PCR

BackgroundNucleic acid amplification techniques are being used increasingly in diagnosing tuberculosis. In developing countries clinical samples are often stored for subsequent analysis since molecular tests are conducted at only a limited number of laboratories. This study was conducted to assess the speed at which mycobacteria undergo autolysis and free DNA is detected in the supernatant during low-temperature storage.ResultsEighty-seven smear positive sputa from tuberculosis patients were analysed immediately and after storage at -20°C. Timelines of 1 and 2 months were selected to assess the maximum extent of DNA loss that occurred during storage. All samples remained PCR- and smear-positive at 1 month and only 1 sample turned negative after 2 months. Bacterial lysis in the specimens was demonstrated by PCR analysis of supernatant fractions; 53% of the freshly analysed samples contained mycobacterial DNA in supernatants. PCR positivity increased significantly during storage (to 69% and 77% after 1 and 2 months of storage, respectively, P < 0.0001). Storage-associated bacterial lysis was accompanied by a decrease in smear grade status in 28 of 87 samples (P < 0.0001 after 2 months of storage) and a significant storage-associated reduction in bacterial numbers in the remaining samples.ConclusionWe conclude that (i) freshly isolated sputum contains both intact and lysed mycobacteria, (ii) lysis increased during storage and (iii) supernatant fractions routinely discarded during sample processing contain mycobacterial DNA. We propose that supernatant is a valuable sample for PCR for both fresh and stored specimens, particularly those with a low bacterial load in addition to conventional sediment.

Evaluation of three commonly used cleaning methods for reducing bacterial numbers on hot drinks vending machine mixing bowls artificially contaminated with Bacillus cereus and Staphylococcus aureus

AbstractDuring normal operation, mixing bowls in hot drinks vending machines become soiled with drink powders and water, increasing the risk of microbial growth and survival of microorganisms. The efficacy of three different cleaning protocols against artificially contaminated mixing bowls was investigated. Mixing bowls were soiled using hot chocolate powder and a suspension of either Staphylococcus aureus or vegetative Bacillus cereus giving a final bacterial load of 106 cfu/cm2, and were cleaned using detergent, detergent/sanitiser and dishwasher‐based cleaning protocols. Traditional microbiological methods were used to measure the effect of cleaning. All three cleaning protocols gave a significant (P ≤ 0.05) reduction in bacterial numbers, each achieving approximately a 3‐log reduction. No significant or operational differences were observed between the three methods, although the detergent/sanitiser protocol achieved the greatest log reduction. This study demonstrates that a simple, detergent‐based cleaning protocol is sufficient to achieve a 3‐log reduction in bacterial load of artificially soiled mixing bowls.

Implementation of Compulsory Hazard Analysis Critical Control Point System and Its Effect on Concentrations of Carcass and Environmental Surface Bacterial Indicators in United Kingdom Red Meat Slaughterhouses

Statutory microbiological test results were collected from British meat plants over a 4-year period from June 2002 to May 2006. A total of 49,074 carcass test results from 19,409 cattle, 14,706 sheep, and 14,959 pig swabs and 95,179 environmental test results from surface swabs were obtained. These test results were donated by 94 slaughterhouses, which process about two thirds of the British national annual throughput of cattle, sheep, and pig carcasses. The data were collectively analyzed to determine any historical trends for numbers of total aerobes and Enterobacteriaceae. Significant reductions were observed in the numbers of indicator organisms on carcasses for all three species between 2002 and 2006. Reductions were also observed for numbers of aerobes on environmental and food contact surfaces. There were seasonal differences in bacterial numbers isolated from carcasses. Cattle and sheep carcasses had significantly higher numbers of total aerobes and Enterobacteriaceae in late summer and early autumn, whereas numbers of total aerobes on pig carcasses were higher in winter. Bacterial numbers on environmental surfaces were not influenced by the month that the swab samples were collected. Possible reasons for the observed reductions in bacterial numbers on carcasses and surfaces and the implications for carcass testing for process control purposes are discussed.

Osseous Coagulum Collected in Bone Traps: Potential for Bacterial Contamination and Methods for Decontamination

Because of its excellent osteogenic potential, autogenous bone is the preferred grafting material for dental procedures; however, bone collected in osseous coagulum traps is subject to contamination by oral bacteria. This study assessed bacterial contamination of osseous coagulum and tested treatments for reducing contamination. Fifty bone samples from patients undergoing implant osteotomy procedures were collected in osseous coagulum traps, divided into groups of 10, and rinsed with normal saline, 0.12% chlorhexidine, or 50 mg/mL tetracycline. Twenty control samples received no treatment. The bone samples were plated in triplicate on selective and differential media to assay aerobic and anaerobic bacteria and potential bacterial pathogens, including staphylococci, streptococci, enterics, and black-pigmented bacteria (BPB). Inoculations were performed with an Autoplate 4000, and plates were incubated at 37 degrees C either aerobically or in a Coy anaerobic chamber. Bacteria were isolated from all samples. In control samples, the mean colony-forming units (cfu) per milliliter of suspended osseous coagulum was 6.5 x 10(4) +/- 9.6 x 10(4) in aerobic cultures and 4.8 x 10(4) +/- 6.9 x 10(4) in anaerobic cultures. Viridans streptococci were isolated from 46 samples, with a mean of 2.9 x 10(4) +/- 4.1 x 10(4) cfu/mL. Enterics were in 16 samples with cfu ranging from 200 cfu/mL to 3.4 x 10(4) cfu/mL. Mannitol nonfermenting staphylococci were found in one sample at 106 cfu/mL. BPB were not isolated. A Mann-Whitney U test with significance set at P = .05 determined that the only statistically significant reductions in bacterial numbers occurred in tetracycline-treated samples of anaerobic bacteria (5-fold decrease, P = .02) and aerobic bacteria (6-fold decrease, P = .01). Tetracycline treatments effected a 7-fold decrease in streptococci, but the difference was not significant (P = .07). These data indicate significant bacterial contamination of bone collected in osseous coagulum traps and justify further research into methods for eliminating that contamination.

Efficacy of Contact Lens Multipurpose Solutions Against Serratia Marcescens

To compare the susceptibilities of clinical isolates of Serratia marcescens and the standard ISO ATCC 13880 strain to five contact lens multipurpose disinfection solutions (MPDSs). Five commercially available MPDSs, containing either a polymeric biguanide or polyquaternium, were tested using ISO/CD 14729 stand-alone test for contact lens care products against four ocular isolates of S. marcescens and the strain ATCC 13880. An average log reduction in bacterial numbers at the manufacturer's minimum recommended disinfection time was determined and compared with the criteria for stand-alone disinfection products for each MPDS against each bacterial strain. All the MPDSs tested met the stand-alone criteria of 3-log reduction of viable bacteria against the ATCC strain of S. marcescens. However, there was more variability in their ability to meet disinfection criteria when tested against the clinical isolates. Two of the clinical isolates were significantly more resistant to disinfection than was the recommended ISO strain (p < or = 0.034). Two of the polyquaternium-1-based disinfection solutions (solutions D and E, p < or = 0.005) were less effective overall than the other MPDSs against S. marcescens. The importance of strain selection for the testing of MPDSs is indicated, and the use of a single laboratory strain may be insufficient to provide assurance that the disinfection solution will be effective against clinical isolates. Furthermore, clinical isolates of S. marcescens may show increased resistance to disinfection with polyquaternium.

Effectiveness of domestic antibacterial products in decontaminating food contact surfaces

Four commercially available antibacterial products (two wipes and two sprays) were tested under laboratory conditions on a range of food contact surfaces (wood, glass, plastic, Microban ® incorporated plastic). The products’ effectiveness at preventing cross-contamination of Escherichia coli and Staphylococcus aureus and the influence of surface type and drying time were assessed. Survival of the bacterial culture (approximately 400 colonies per 8 cm 2) on the above preparation surfaces was determined using an in situ nitroblue tetrazolium (NBT) method. In the absence of any antibacterial products, both bacteria survived up to 120 min on all test surfaces with glass and plastic showing no reduction in bacterial number. The order of survival is: glass>plastic⪢Microban ® incorporated plastic>wood (<8%). The length of drying time did not affect the survival of either bacterium on glass and plastic surfaces. On wood and Microban ® incorporated plastic, E. coli appeared to be more sensitive to drying time than S. aureus. Only plastic appeared to affect the effectiveness of the antibacterial products, where the reduction in bacterial number was significantly lower than the other test surfaces ( p < 0.05 ). The overall results suggest the antibacterial products are effective in disinfecting food preparing surfaces, provided products instructions are carefully followed.

Effect of Different Forms of Adenylate Cyclase Toxin ofBordetella pertussison Protection Afforded by an Acellular Pertussis Vaccine in a Murine Model

Four recombinant forms of the cell-invasive adenylate cyclase toxin (CyaA) of Bordetella pertussis were compared for the ability to enhance protection against B. pertussis in mice when coadministered with an acellular pertussis vaccine (ACV). The four forms were as follows: fully functional CyaA, a CyaA form lacking adenylate cyclase enzymatic activity (CyaA*), and the nonacylated forms of these toxins, i.e., proCyaA and proCyaA*, respectively. None of these forms alone conferred significant (P > 0.05) protection against B. pertussis in a murine intranasal challenge model. Mice immunized with ACV alone showed significant (P < 0.05) reductions in bacterial numbers in the lungs after intranasal challenge compared with those for control mice. When administered with ACV, both CyaA and CyaA* further reduced bacterial numbers in the lungs of mice after intranasal challenge compared with those for ACV-immunized mice, but the enhanced protection was only significant (P < 0.05) with CyaA*. Coadministration of CyaA* with ACV caused a significant (P < 0.05) increase in immunoglobulin G2a antibody levels against pertactin compared with those in mice immunized with ACV alone. Spleen cells from mice immunized with ACV plus CyaA* secreted larger amounts of interleukin-5 (IL-5), IL-6, gamma interferon (IFN-gamma), and granulocyte-macrophage colony-stimulating factor (GM-CSF) than did cells from mice immunized with ACV plus CyaA or ACV alone after stimulation in vitro with a mixture of B. pertussis antigens. Spleen cells from mice immunized with ACV plus CyaA* also secreted larger amounts of IFN-gamma and GM-CSF than did cells from mice immunized with CyaA* alone after stimulation in vitro with CyaA*. Macrophages from mice immunized with ACV plus CyaA* produced significantly (P < 0.05) higher levels of nitric oxide than did macrophages from mice immunized with CyaA* alone, ACV alone, or ACV plus CyaA after stimulation in vitro with a mixture of B. pertussis antigens or heat-killed B. pertussis cells. These data suggest that the enhancement of protection provided by CyaA* was due to an augmentation of both Th1 and Th2 immune responses to B. pertussis antigens.

The efficacy of antibiotics against Propionibacterium acnes biofilm infections on spinal implant material

Treated groups One group of mature biofilms was exposed to Penicillin G alone and the other with combination of Penicillin G with Rifampicin for 96 hrs respectively. Again, the discs were retrieved, sonicated and the number of viable bacteria were counted by chemilumiluminesence and culture Results All P.acnes biofilms responded to treatment with a significant reduction in bacterial numbers. Combination therapy was more effective and produced greater reductions (96.6%) of viable bacteria populating the biofilms than penicillin alone, 93.3% (p < 0.01). Complete eradication of the biofilm was not achieved in any cases.

A comparison of the effectiveness of TiO 2 photocatalysis and UVA photolysis for the destruction of three pathogenic micro-organisms

TiO 2 photocatalysis has demonstrated efficacy as a treatment process for water contaminated with chemical pollutants. When exposed to UVA light TiO 2 also demonstrates an effective bactericidal activity. The mechanism of this process has been reported to involve attack by valence band generated hydroxyl radicals. In this study when three common bacterial pathogens, Escherichia coli, Salmonella enterica serovar Enteritidis and Pseudomonas aeruginosa, were exposed to TiO 2 and UVA light a substantial decrease in bacterial numbers was observed. Control experiments in which all three pathogens were exposed to UVA light only resulted in a similar reduction in bacterial numbers. Moreover, exposure to UVA light alone resulted in the production of a smaller than average colony phenotype among the surviving bacteria, for all three pathogens examined, a finding which was not observed following treatment with UVA and TiO 2. Small slow growing colonies have been described for several pathogenic bacteria and are referred to as small colony variants. Several studies have demonstrated an association between small colony variants and persistent, recurrent and antibiotic resistant infections. We propose that the production of small colony variants of pathogenic bacteria following UVA treatment of drinking water may represent a health hazard. As these small colony variants were not observed with the UVA/TiO 2 system this potential hazard is not a risk when using this technology. It would also appear that the bactericidal mechanism is different with the UVA/TiO 2 process compared to when UVA light is used alone.

Surface disinfection of cod Gadus morhua and haddock Melanogrammus aeglefinus eggs with bronopol

Using current practice of immersion, the survival of cod eggs disinfected with 50 mg l − 1 to 500 mg l − 1 bronopol (as Pyceze [50%W/V bronopol], Novartis Animal Vaccines Ltd.) for 45 s, was higher (83–89%) when compared with negative controls (48%). Hatching larvae survived exposure to Pyceze but not to Kickstart (25% peracetic acid/hydrogen peroxide, CIDLines UK), a common disinfectant in United Kingdom marine finfish hatcheries. Bacterial numbers on cod eggs were 30 CFU ml − 1 following contact with 50 mg l − 1 bronopol and zero at 1000 mg l − 1 compared with 14,000 CFU ml − 1 with no disinfection. Although survival to hatch of haddock eggs in 50 mg − 1 bronopol (71.6%) was higher than in non-disinfected eggs (62.4%) this was not significant. Haddock eggs required a concentration of 500 mg l − 1 bronopol to achieve a significant reduction in bacterial numbers, 352 cf. 1546 CFU ml − 1 in seawater controls. Alternative techniques to immersion were assessed to reduce repeated handling and possible damage to eggs. A flow-through system utilising a peristaltic dosing pump was ineffective in achieving the target concentration of Pyceze and contact time, but use of a static immersion technique in an incubation unit, with 30 min daily exposure to 50 mg l − 1 bronopol, gave 63% survival to hatch compared with 35% with a negative control. Bacterial numbers of 892 CFU ml − 1 following treatment with Pyceze were significantly lower than the 91,400 CFU ml − 1 in negative controls. In target animal safety studies with 250 mg l − 1 bronopol, namely × 5 target concentration for 2× exposure time, survival of haddock eggs of 88.7% was significantly higher when compared with 53.1% in non-disinfected.

Antimicrobial activity of ultrasonic cleaners

This study assessed the antimicrobial activity of two cleaning solutions and tap water after varying periods of use in one ultrasonic cleaner. Testing involved filling the cleaner's tank and a centred glass beaker with the same test solution. An aluminium foil strip test first determined that no significant differences in cavitational activity existed inside the beaker compared with outside. Standardized solutions of Staphylococcus aureus, Pseudomonas aeruginosa and Salmonella choleraesuis were left at room temperature for 10 min. Aliquots were exposed to both cleaning solution and ultrasonic action. Unused test solution was removed from the tank, filter-sterilized, mixed with bacterial suspension and placed into a sterile beaker. Cleaning was allowed for 10 min. The beaker was removed and its contents examined. The tank was allowed to cool for 30 min and the process was repeated four times. The entire experimental set was repeated once. Exposure to test solution alone in all but one case produced reductions in bacterial numbers from initial >/=2 x 10(9) by 19.9-52.6%. Application of both chemical exposure and ultrasonic cleaning produced greater bacterial kill (46.4-99.7% reductions). However, kill became less effective on repeated use of a commercial cleaning solution. Reduction was highest when fresh ultrasonic cleaning solutions were used. In no case did complete sterilization occur. As well as removing adherent material, ultrasonic cleaning may also markedly reduce the number of viable organisms present.

Legionella pneumophilaEvades Gamma Interferon-Mediated Growth Suppression through Interleukin-10 Induction in Bone Marrow-Derived Macrophages

We examined the roles of Th1-Th2 cytokine cross talk in Legionella pneumophila-infected bone marrow-derived (BM) macrophages in the presence of costimulation with interleukin-12 (IL-12) and IL-18. Treatment with gamma interferon (IFN-gamma) alone or treatment with IL-12 in combination with IL-18 resulted in a 3- or 2-log reduction in bacterial numbers, respectively, in BM macrophages, whereas treatment with IL-12 or IL-18 alone had no effect. Significant amounts of IFN-gamma were detected in the culture supernatants of infected macrophages stimulated with IL-12 and IL-18 in combination but not independently. Neutralization of IFN-gamma by antibody completely abolished the growth inhibitory effects of IL-12 and IL-18. Interestingly, higher infectivity ratios of L. pneumophila or the addition of increasing concentrations of heat-killed bacteria (HKB) suppressed the production of IFN-gamma, which resulted in the increased intracellular growth of bacteria. Significant amounts of IL-10 were detected in culture supernatants when Legionella-infected macrophages were cocultured with HKB. Furthermore, neutralization of IL-10 by antibody resulted in an increase in IFN-gamma production by infected BM macrophages when cocultured with HKB. Treatment of HKB with trypsin but not polymyxin B attenuated the growth-promoting effects of HKB, suggesting the involvement of a protein component(s) in regulation of the growth of L. pneumophila. These findings demonstrate a crucial role of Th1-Th2 cross talk in L. pneumophila-infected BM macrophages. Our results also suggest that L. pneumophila modulates the cytokine balance from IFN-gamma-driven Th1 to more Th2 responses, likely through the induction of IL-10 by a bacterial protein component(s). These data provide new insights not only into the cellular mechanisms of Th1-Th2 cross talk in Legionella-infected macrophages but also into the pathogenesis of L. pneumophila pneumonia in humans.

Bacterial diversity promotes community stability and functional resilience after perturbation

The relationships between bacterial community diversity and stability were investigated by perturbing soils, with naturally differing levels of diversity, to equivalent toxicity using copper sulfate and benzene. Benzene amendment led to large decreases in total bacterial numbers and biomass in both soils. Benzene amendment of an organo-mineral/improved pasture soil altered total soil bacterial community structure but, unlike amendment of the mineral/arable soil, maintained genetic diversity, based on polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis targeting DNA and RNA, until week 9 of the perturbation experiment. Assuming equivalent toxicity, the genetic diversity of the naturally more diverse soil was more resistant to benzene perturbation than the less diverse soil. The broad scale function (mineralization of 14C-labelled wheat shoot) of both benzene- and copper-treated soil communities was unaffected. However, narrow niche function (mineralization of 14C-labelled 2,4-dichlorophenol) was impaired for both benzene-polluted soils. The organo-mineral soil recovered this function by the end of the experiment but the mineral soil did not, suggesting greater resilience in the more diverse soil. Despite a large reduction in bacterial numbers and biomass in the copper-treated soils, only small differences in bacterial community diversity were observed by week 9 in the copper-polluted soils. The overall community structure was little altered and functionality, measured by mineralization rates, remained unchanged. This suggested a non-selective pressure and a degree of genetic and functional resistance to copper perturbation, despite a significant reduction in bacterial numbers and biomass. However, initial shifts in physiological profiles of both copper-polluted soils were observed but rapidly returned to those of the controls. This apparent functional recovery, accompanied by an increase in culturability, possibly reflects adaptation by the surviving communities to perturbation. The findings indicate that, although soil communities may be robust, relationships between diversity and stability need to be considered in developing a predictive understanding of response to environmental perturbations.

Protection of macaques against Mycobacterium tuberculosis infection by a subunit vaccine based on a fusion protein of antigen 85B and ESAT-6

Various new tuberculosis (TB) vaccine candidates in combination with new delivery systems, including subunit vaccines, are currently being evaluated by a number of laboratories. One vaccine candidate that has shown promising protective capacity in mice and guinea pigs is a fusion of Ag85B and ESAT-6. In this study, we have investigated the efficacy of this Ag85B–ESAT-6 fusion protein vaccine in a non-human primate model for TB. Vaccination of cynomolgus monkeys with the Ag85B–ESAT-6 fusion protein in two different adjuvant (DDA/MPL, AS02A) resulted in a reduction in bacterial number and/or lung pathology in animals challenged with Mycobacterium tuberculosis. Vaccination prevented an increase in C-reactive protein serum levels, general activation of CD4 and CD8 subsets and boosted development of humoral and cellular immune responses to a spectrum of mycobacterial antigens on exposure to M. tuberculosis infection. We show, in two independent experiments, that vaccination of primates with Ag85B–ESAT-6 induces protective immune responses, suggesting that Ag85B–ESAT-6 is a strong candidate for further clinical evaluation. As far as we are aware this is the first report of protection in primates with a subunit vaccine.

Microbiological changes associated with dental prophylaxis

Despite the common application of dental prophylaxis as part of patient therapy, there is little reported that describes the microbiological impact of this treatment. The authors gave 20 healthy college-aged subjects three dental prophylaxes with a fluoride-containing prophylaxis paste during a two-week period and instructed them in oral hygiene. They evaluated the microbiological composition of dental plaque samples collected before and after treatment using DNA probe analysis. They analyzed 40 representative bacterial species in seven bacterial complexes by checkerboard DNA-DNA hybridization assay techniques. After three dental prophylaxes, the patients' mean Gingival Index score decreased from 0.82 to 0.77, the mean Plaque Index score decreased from 0.72 to zero, and the total number of bacteria per tooth decreased to approximately one-third of the original number. The authors computed two different measures of bacterial presence. The reduction in bacterial numbers was statistically significant and occurred in many species. Bacterial proportion (DNA percentage or percentage of the bacteria per tooth) did not change significantly. Greater reductions in bacterial count occurred in species that showed high numbers before treatment. The total bacterial count decreased by approximately 72 percent of its original level before prophylaxis was initiated. Professional dental prophylaxis did not target any particular bacteria or bacterial groups but removed bacteria nonspecifically and in proportion to their initial numbers. Repeated dental prophylaxes effect a reduction in bacterial amount that is commensurate with the initial amount, but they do does not alter composition. This suggests that mild gingivitis may be a bacterially nonspecific effect of plaque accumulation and emphasizes the need for regular plaque removal to maintain optimal gingival health.

Manual versus automated methods for cleaning reusable accessory devices used for minimally invasive surgical procedures

We undertook a simulated-use study using quantitative methods to evaluate the cleaning efficacy of ported and non-ported accessory devices used in minimally invasive surgery. We chose laparoscopic scissors and forceps to represent worst-case devices which were inoculated with artificial test soil containing 10 6 cfu/mL Enterococcus faecalis and Geobacillus stearothermophilus and allowed to dry for 1 h. Cleaning was performed manually, as well as by the automated SI-Auto Narrow lumen cleaner. Manual cleaning left two- to 50-fold more soil residuals (protein, haemoglobin and carbohydrate) inside the lumen of non-ported versus ported laparoscopic accessory devices. The SI-Auto Narrow lumen cleaner was more efficient than manual cleaning and achieved >99% reduction in soil parameters in both non-ported (using retro-flushing) and ported laparoscopic devices. Only the automated cleaning of ported devices achieved 10 3–10 4–fold reduction in bacterial numbers. Sonication alone (no flushing of inner channel) did not effectively remove soil or organisms from the inner channel. Our findings indicate that non-ported accessory devices cannot be as reliably cleaned as ported devices regardless of the cleaning method used. If non-ported accessory devices are reprocessed, they should be cleaned using retro-flushing in an automated narrow lumen cleaner.

Nutritional and bacterial profiles of juvenile Artemia fed different enrichments and during starvation

Biochemical and bacterial profiles of juvenile Artemia (1.5 mm, 5 days old) were examined in two experiments designed to manipulate their nutritional composition. In Experiment 1, Artemia were enriched for up to 36 h with the diatom Chaetoceros muelleri, the chromist Schizochytrium (Algamac 3050®) or a squid oil emulsion. In Experiment 2, Artemia were enriched with the same diets for 6 h, and then starved for 24 h at 4, 18 or 28 °C. Artemia did not survive beyond 24 h enrichment on Algamac and survival was low on oil emulsion, contrasting with the rapid growth and high survival on C. muelleri. Fatty acid (FA) content of Artemia increased marginally after enrichment with C. muelleri, with a marked increase over 36 h enrichment in the percent long-chain polyunsaturated FA (LC-PUFA). FA content increased by 60% and 140% after enrichment with Algamac and squid oil emulsion, respectively, and %LC-PUFA also increased. FA content and %LC-PUFA in starved Artemia declined by up to 57% at 28 °C whereas the proportional loss was <30% at 4 °C. Ascorbic acid (AsA) content in Artemia increased four-fold over 36 h enrichment with C. muelleri and declined or did not change with the other enrichments. AsA was retained during starvation of 6 h-enriched Artemia with all treatments. α-Tocopherol (α-T) concentration increased three-fold to a peak after 6 h on oil emulsion and increased two-fold after 24 h on C. muelleri while decreasing by 50% during 12 h on Algamac. α-T declined during starvation by up to 50% (depending on temperature) following enrichment with oil emulsion although there was no change with C. muelleri or Algamac. For Artemia enriched 12 h on C. muelleri or 6 h on oil emulsion, bacterial abundance was not elevated but further enrichment resulted in increases by two- to three-fold. Bacterial abundance in Artemia enriched for 6 h on Algamac increased four-fold and by 24 h, most Artemia had perished. Total numbers of heterotrophic bacteria and Vibrio spp. were similar after enrichment for 6 h with C. muelleri or oil emulsion and after 24 h starvation at 18 or 28 °C. Starvation at 18 or 28 °C after Algamac enrichment increased bacterial numbers up to four-fold. For Artemia starved at 4 °C for 24 h, there was a marked reduction in bacterial numbers for all enrichments, indicating that cool temperatures may be bactericidal. Enrichment of juvenile Artemia for 6 h achieved substantial biochemical improvement while minimising bacterial contamination, and is regarded as a suitable protocol before feeding to target species such as spiny lobster phyllosoma larvae.

Influence of partial liquid ventilation on bacterial growth and alveolar expansion in newborn rabbits with group B-streptococcal pneumonia.

Partial liquid ventilation (PLV) with perfluorocarbons has been considered as an alternative therapy for severe inflammatory lung disease. The present study was performed to test whether PLV influences bacterial growth and lung histology in a rabbit model of congenital pneumonia caused by group B streptococci. Near-term newborn rabbits were tracheotomized, inoculated via the airways with group B streptococci, and subsequently ventilated for 5 h with either PLV or conventional ventilation. At 30 min after group B streptococci administration, animals in the PLV group (n = 16) received 30 mL/kg body weight of perfluorocarbon (PF 5080) via the tracheal tube. Evaporative losses were substituted with 20 mL/kg perfluorocarbon at hourly intervals. Identical volumes of air were injected in control animals at the same times (n = 15). The number of colony-forming units in left lung homogenate, evaluated at the end of the experiments, tended to be lower in PLV-treated animals than in controls (6.8 x 109 versus 6.4 x 1010 colony-forming units/g body weight; p = 0.06). Comparison of these numbers with the colony-forming units injected at the beginning of the experiments revealed a reduction in bacterial number in the PLV group and proliferation in the controls (-2.2 x 108 versus +5.6 x 1010 colony-forming units/g body weight; p < 0.05). Histologic examination demonstrated less inflammation and more homogeneous lung expansion in PLV-treated animals. Two animals in the PLV group had focal interstitial emphysema. Our results suggest that PLV with PF 5080 reduces bacterial proliferation in experimental group B streptococcal pneumonia.

Antibacterial activity of bactericide-immobilized filler for resin-based restoratives

This study examined the antibacterial activity of prepolymerized resin filler, in which the bactericide quaternary ammonium was immobilized. The experimental filler was prepared by grinding prepolymerized resin blocks of methacrylate monomers, silica particles, and the antibacterial monomer methacryloyloxydodecylpyridinium bromide (MDPB). The number of Streptococcus mutans after incubation for 18 h in contact with the experimental filler with or without protein adsorption by saliva treatment was determined, and adherence of bacteria to the filler surface was evaluated by scanning electron microscopy. Elution of unpolymerized MDPB from the filler and its influence on bacterial growth were also investigated. The growth of S. mutans was completely inhibited by contact with the experimental filler without saliva treatment. Although the effects were attenuated, the saliva-treated filler still exhibited growth inhibition at >99.9%. Less bacteria attached to the experimental filler than the control filler without MDPB, indicating that the reduction in bacterial number after contact with the experimental filler was not due to bacterial adherence to the particles. Unpolymerized MDPB at 1 μg/ml was eluted from the filler particles but was confirmed to have little effect on bacterial growth. The results indicate that the bactericide-immobilized filler containing MDPB shows significant bacteriostatic effects without releasing antibacterial components, and is useful for incorporation into various resin-based restoratives.

Simulated in vitro Quinolone Pharmacodynamics at Clinically Achievable AUC/MIC Ratios: Advantage of IE over Other Integral Parameters

To compare the antimicrobial effects of clinically achievable ratios of area under the curve (AUC) to MIC, a clinical isolate of Moraxella catarrhalis was selected with MICs corresponding to the MIC₅₀s of four quinolones. Monoexponentially declining concentrations observed in human plasma after oral administration of 1,000 mg of ciprofloxacin (as two 500-mg doses at a 12-hour interval), 320 mg gemifloxacin, 500 mg levofloxacin or 400 mg moxifloxacin (each as a single dose) and were simulated in an in vitro dynamic model. The respective half-lives were 4, 7.4, 6.8 and 12.1 h, and the AUC/MICs were 730, 1,130, 920 and 690 h. The time-kill/regrowth curves yielded similar patterns with the four quinolones: a rapid reduction in bacterial numbers followed by bacterial regrowth that occurred later with moxifloxacin than with ciprofloxacin, gemifloxacin, and levofloxacin. The total antimicrobial effect of moxifloxacin as expressed by the I_E parameter (area between the control growth and time- kill curves from time zero to the time when bacterial counts on the regrowth curve achieve the same maximal numbers as in the absence of antimicrobial) was 30, 55, and 120% greater than gemifloxacin, levofloxacin and ciprofloxacin, respectively. Unlike I_E, the other integral indices determined over a fixed time (24 h) – the area between the control growth and time-kill curves, area above the time-kill curve and area under the time-kill curve were similar for the four fluoroquinolones, thus precluding their differentiation.