Staphylococcus aureus nasal carriage rate and associated risk factors in individuals in the community.

The increasing prevalence of Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) strains together with their disease impact on hospital patients and individuals in the community has posed a major challenge to healthcare workers. This study examined the prevalence of S. aureus nasal carriage, antimicrobial susceptibility patterns, and possible risk factors in the community. Of 500 studied subjects (aged from 6 to 65 years) in Lebanon, the overall S. aureus nasal carriage rate was 38.4%, the highest (57.1%) being in children aged 6-10 years. Only eight individuals (1.6%) were carriers of MRSA. Risk factors for S. aureus nasal colonization were male gender, young age, contact with healthcare workers, use of needle injections, and having asthma. A significant decrease in colonization rate was associated with nasal wash with water, use of nasal sprays, and the presence of acne. These findings may assist in better understanding of control measures to decrease nasal colonization with S. aureus in Lebanon and elsewhere.

Cholesterol protects Acholeplasma laidlawii against oxidative damage caused by hydrogen peroxide.

The aim of this study was to determine whether cholesterol, added to the cell growth medium or to cell suspension buffer, could protect Acholeplasma laidlawii cells against the toxic effects of hydrogen peroxide (H(2)O(2)). Variable concentrations of cholesterol (0.05-1.0 mg/ml) were added to the A. laidlawii suspension buffer and to the growth medium. Cells were then washed carefully and incubated with 0.001% (v/v) H(2)O(2) at 37 degrees C for 30 min and the viability was determined. The results indicated that cells were more viable in the presence of cholesterol than were cells grown in the absence of cholesterol. In addition, the oxygen uptake rate resulting from the oxidation of 5.5 mmol/L glucose was 2-fold and 4-fold higher for cells grown in medium supplemented with 0.05 and 0.50 mg/ml cholesterol, respectively, compared to cells grown in a medium with no added cholesterol. These findings indicate that cholesterol might play a role in protecting Mollicutes against the oxidative damage caused by H(2)O(2).

The pattern and kinetics of substrate metabolism of Campylobacter jejuni and Campylobacter coli.

AIMS: The main aim was to investigate the patterns and kinetics of substrate oxidation by Campylobacter jejuni and C. coli. METHODS AND RESULTS: Substrate oxidation profiles by 100 strains were determined using oxygen electrode system. All the isolates tested oxidized formate, l-lactate, cysteine, glutamine and serine with high oxidation rates and high affinity but varied in their ability to oxidize citric acid cycle intermediates, aspartic acid and serine. CONCLUSIONS: Based on the oxidation ability of alpha-ketoglutarate, succinate, fumarate and aspartic acid, Campylobacter strains tested were divided into three distinct metabolic categories. The first group was able to metabolize alpha-ketoglutarate, succinate, fumarate and aspartic acid; the second group was unable to oxidize alpha-ketoglutarate; and the third group was unable to oxidize, succinate, fumarate, and aspartic acid. Furthermore, serine oxidation rate enabled the differentiation of C. jejuni and C. coli. SIGNIFICANCE AND IMPACT OF THE STUDY: Overall, the results highlights the extensive metabolic diversity between and within Campylobacter species. In addition, the kinetic data of oxidized substrates obtained may improve the isolation procedures of the organism.

Evaluation of the COBAS AMPLICOR MTB test for the detection of Mycobacterium tuberculosis complex.

We evaluated the COBAS AMPLICOR polymerase chain reaction (PCR) based test for the detection of Mycobacterium tuberculosis complex in 866 respiratory and non-respiratory samples. Acid-fast staining and culture on Lowenstein-Jensen medium were also performed on all samples. Of the 866 samples tested, 87 (10.0%) were PCR-positive compared to 94 (10.9%) culture positive. There were no false positive results but 7 PCR-negative, culture-positive samples were, considered false negatives after reviewing medical records of patients. A PCR inhibitory rate of 2.0% (17/866) was observed in respiratory samples only. Sensitivity, specificity, and positive and negative predictive values for this test were 92.5%, 100%, 100% and 99.1% respectively. This test is a valuable diagnostic tool for today's mycobacteriology laboratory.

Evaluation of the COBAS AMPLICOR MTB test for the detection of Mycobacterium tuberculosis complex

We evaluated the COBAS AMPLICOR polymerase chain reaction [PCR] based test for the detection of Mycobacterium tuberculosis complex in 866 respiratory and non-respiratory samples. Acid-fast staining and culture on Lowenstein-Jensen medium were also performed on all samples. Of the 866 samples tested, 87 [10.0%] were PCR-positive compared to 94 [10.9%] culture positive. There were no false positive results but 7 PCR-negative, culture-positive samples were, considered false negatives after reviewing medical records of patients. A PCR inhibitory rate of 2.0% [17/866] was observed in respiratory samples only. Sensitivity, specificity, and positive and negative predictive values for this test were 92.5%, 100%, 100% and 99.1% respectively. This test is a valuable diagnostic tool for today's mycobacteriology laboratory

Alternative to fluorescence assays to monitor fusion between Acholeplasma laidlawii cells and liposomes.

AIMS: To develop a new technique as an alternative to the fluorescence assays and electron microscopy for the purpose of monitoring the cell-liposome fusion. METHODS AND RESULTS: Acholeplasma laidlawii whole cells did not oxidize Glucose-6-phosphate (G6P) or Fructose-1,6 diphosphate (F1,6DP) as free (unentrapped) substrates, at concentrations 47 and >270 mM, respectively. Lysed A. laidlawii cells oxidized G6P and F1,6DP at lower concentration of 0.8 and 15 mM, respectively. When these substrates were entrapped inside liposomes, at a final concentration of 1.5 mM, and interacted with A. laidlawii whole cells, in an oxygen electrode chamber, an increase in oxygen uptake was evident. This interaction does not have any effect on cell viability. SIGNIFICANCE AND IMPACT OF THE STUDY: The experimental system described here is advantageous over classical fluorescence assays in determining the fate of liposome-entrapped material and raises the possibility of studying the kinetics of metabolic substrates, which are normally excluded from the cell by the cell membrane.

Legionella drozanskii sp. nov., Legionella rowbothamii sp. nov. and Legionella fallonii sp. nov.: three unusual new Legionella species.

Seven strains of Legionella-like amoebal pathogens (LLAPs) were characterized on the basis of their cultural and staining characteristics, biochemical reactions, serology, cellular fatty acids (CFAs), isoprenoid quinone composition, total DNA relatedness, analysis of 16S rRNA and macrophage infectivity potentiator (mip) gene sequence analyses. All seven strains exhibited limited growth on buffered charcoal yeast extract alpha (BCYE) agar, required cysteine for growth and contained branched-chain CFAs and quinones typical of Legionella species. The bacilli were Gram-negative and catalase-positive. There were varying degrees of serological cross-reactions between these LLAP strains and other previously described Legionella species. Results from the various tests revealed that four LLAP strains represent three unusual new species of Legionella: Legionella drozanskii sp. nov., type strain LLAP-1T; Legionella rowbothamii sp. nov., type strain LLAP-6T; and Legionella fallonii sp. nov., type strain LLAP-10T. Three other LLAP strains, designated LLAP-7FL, LLAP-7NF and LLAP-9, were shown to be members of the species Legionella lytica. The deductions made from the phenetic characteristics of these bacteria were consistent with the phylogenetic relationships inferred from 16S rRNA and mip gene sequence analyses. This study is the first to speciate LLAP strains on the basis of data including quantitative DNA hybridization.

Kinetics and distribution of alcohol oxidising activity in Acholeplasma and Mycoplasma species.

Alcohol metabolism by Acholeplasma and Mycoplasma cell suspensions was determined using changes in dissolved oxygen tension to monitor oxygen uptake. All seven Acholeplasma test species oxidised ethanol and (where tested) propanol, butanol and pentanol. The rate of oxidation, at any particular substrate concentration, decreased with increasing alcohol molecular mass. Amongst 20 Mycoplasma species tested, M. agalactiae, M. bovis, M. dispar, M. gallisepticum, M. pneumoniae and M. ovipneumoniae oxidised ethanol. Propanol was also oxidised by M. dispar and isopropanol by M. agalactiae, M. bovis and M. ovipneumoniae. Isopropanol was oxidised at particularly high rates (V(max)100 nmol O(2) taken up min(-1) mg cell protein(-1)) and with a relatively high affinity (K(m) value<2 mM); oxygen uptake was consistent with oxidation to acetone. The significance of alcohol oxidation is unclear, as it would not be predicted to lead to ATP synthesis.

Distribution of bacteria on hands and the effectiveness of brief and thorough decontamination procedures using non-medicated soap.

Our perception of the role of hand washing in the clinical situation is based on experimental studies in which test-bacteria are usually inoculated onto the skin surface and removed using hand washing preparations containing antiseptics. In this study, we have investigated the distribution of bacteria on the hands of volunteers and the effectiveness of long (3 minute) and brief (10 second) washes in removing both naturally-occurring and artificially-inoculated bacteria (Micrococcus sp.), using only soap and water. There was a tenfold reduction in median counts of artificially inoculated bacteria following both long and brief washes. However, less than 50% of naturally-occurring bacteria were removed and, for hands previously disinfected by immersion in 70% ethanol, the washing procedure increased bacterial counts. In both unwashed hands, and hands washed following a strict protocol, the mean variation in counts of naturally-occurring bacteria at different sites (wrists, dorsal surface, palmar surface, fingertips and interdigital spaces) was only two-fold. The efficiency of recovery of naturally-occurring organisms was estimated by repeated swabbing, to be more than 60%. The data question the value of typical hand wash procedures recommended by many authorities for use in clinical situations and of the perfunctory hand washes frequently adopted by nursing staff in busy wards. Experimental evidence is required to justify procedures and to identify the precise circumstances in which they are of value.

An in situ method for determining bacterial survival on food preparation surfaces using a redox dye.

A simple method is described for the direct enumeration of viable bacteria dried on test surfaces. Inoculated surfaces were overlayed with agar and after incubation nitroblue tetrazolium solution (pale yellow) was used to stain colonies (purple) at the agar-test surface interface. Stained colonies could be readily detected and counted even against the opaque background of ceramic tile or stainless steel or when present within opaque films of milk or serum. Recovery of bacterial by this method was approximately fivefold greater than using a conventional swabbing procedure. The method was used to demonstrate the marked effect of the composition of the suspension fluid, in which bacteria were dried, and the length of surface exposure upon bacterial survival.

Nisin resistance distinguishes Mycoplasma spp. from Acholeplasma spp. and provides a basis for selective growth media.

The sensitivity of 11 Mycoplasma and 5 Acholeplasma species to the bacteriocin nisin was determined. When applied on filter paper discs to lawns of acholeplasma cells, nisin (20 nmol per disc) gave 3.5- to 7.0-mm zones of growth inhibition. The inclusion of 0.2 mM nisin in agar medium reduced the number of Acholeplasma laidlawii colonies by a factor of more than 10(6), and in a salts solution, 75 microM nisin killed more than 99.9% of cells within 1 min. Under similar conditions, nisin had no significant effect upon the growth or survival of Mycoplasma species. At low concentrations (1 to 3 microM), nisin stimulated glucose oxidation by A. laidlawii and Acholeplasma oculi. However, in comparison with carbonyl cyanide m-chlorophenylhydrazone (CCCP), a recognized protonophore and uncoupler of respiration, the maximum extent of stimulation was low, < or = 20%, compared with up to 180% for CCCP. Also, in contrast to results obtained with CCCP, at concentrations only slightly above those causing stimulation of acholeplasma oxygen uptake, nisin strongly inhibited respiration. Inhibition of oxygen uptake was greater for A. laidlawii cells grown in the absence of cholesterol, and on agar medium, growth inhibition by nisin decreased with increasing concentrations of cholesterol. Nisin resistance may be a valuable characteristic in the selection and identification of Mycoplasma spp.

Ultra-structure and localisation of formazan formed by human neutrophils and amoebae phagocytosing virulent and avirulent Legionella pneumophila.

Legionella pneumophila (LP) strains of differing virulence were incubated with a solution of nitroblue-tetrazolium (NBT) at a concentration of 1 mg.ml-1 in the presence of Acanthamoeba polyphaga or human polymorphonuclear neutrophils (PMN). Reduction of NBT to formazan occurred at a faster rate in the presence of virulent strains. Reduction appeared to be temperature dependent; at 37 degrees C the reaction rate was higher than at 20 degrees C. On microscopic examination, deposits of formazan around Legionella cells were observed inside amoebae similar to those deposited in human neutrophils. Electron microscopy revealed electron-dense particles surrounding virulent legionellae, which appeared to be associated with formazan formation. Formazan formation inside amoebae may suggest the presence of a respiratory burst against LP, which is more intense with virulent strains.