Use of fluorescently labeled phage in the detection and identification of bacterial species

Phages are viruses whose hosts are bacterial cells. They identify their hosts by specific receptor molecules on the outside of the host cell. Once the phages find their specific receptors, they bind to the bacterial cell and inject their nucleic acid inside the cell. The binding between phage and host can be so specific that only certain strains of a single species can be infected. In this communication, the specificity of phage P22 for Salmonella typhimurium LT2 is exploited to allow the detection of Salmonella in the presence of other bacterial species. In particular, the dsDNA of P22 is bound to SYBR gold, a highly sensitive, fluorescent nucleic acid stain. When multiple phages infect the same cell, the fluorescence emissions of the phage DNA inside the cell allow it to be imaged using an epifluorescence microscope. The advantages of using phages as the bacterial recognition element in a sensor over antibodies are discussed.

Effect of protein binding on the in vitro activity and pharmacodynamics of faropenem

The influence of protein binding upon different aspects of the in vitro activity of faropenem on recently isolated Staphylococcus aureus and respiratory pathogens was determined. The protein binding of faropenem was investigated in inactivated human serum and albumin by ultrafiltration. The effect of the presence of inactivated human serum and albumin on the in vitro activity of faropenem and amoxicillin was established and the influence of protein binding on the pharmacodynamic properties of faropenem and amoxicillin was compared. The protein binding of faropenem was 96% and 95% in pooled inactivated human serum and 99% and 98% in 45 mg/L human albumin, at 8 and 25 mg/L, respectively. The presence of inactivated human serum (20% and 70%) increased the mean faropenem MICs by two dilution steps and albumin increased the mean faropenem MICs by three dilution steps. The mean amoxicillin MICs were less affected than faropenem by the presence of either inactivated human serum or albumin. Faropenem and amoxicillin exhibited similar time-dependent kinetics. Faropenem was bacteriostatic on Moraxella catarrhalis, Haemophilus influenzae and group A streptococci, and bactericidal for Streptococcus pneumoniae (after 4 h with concentrations equivalent to 5 x and 10 x MIC) in Iso-Sensitest broth. In 70% inactivated human serum faropenem was slowly bactericidal against M. catarrhalis, H. influenzae (one strain) and S. pneumoniae (one strain) but not group A streptococci and the other S. pneumoniae strain. A significant inoculum effect was observed with all strains except S. pneumoniae. Both faropenem and amoxicillin appeared more active in 70% inactivated human serum than in Iso-Sensitest broth.

Comparison of the in vitro activities of several new fluoroquinolones against respiratory pathogens and their abilities to select fluoroquinolone resistance

In this study the in vitro activities and pharmacodynamic properties of moxifloxacin, levofloxacin, gatifloxacin and gemifloxacin were compared on recently isolated respiratory pathogens and strains of Streptococcus pneumoniae with known mechanisms of fluoroquinolone resistance. In addition, the resistance selection frequencies of moxifloxacin and levofloxacin on three recently isolated respiratory pathogens and four strains of S. pneumoniae with known mechanisms of fluoroquinolone resistance were investigated. The four fluoroquinolones had similar activities against both Moraxella catarrhalis (MIC(90)s 0.015-0.06 mg/L) and Haemophilus influenzae (MIC(90)s 0.008-0.03 mg/L). More marked differences in activity were noted with S. pneumoniae, with MIC(90)s of 0.25, 1, 0.5 and 0.03 mg/L for moxifloxacin, levofloxacin, gatifloxacin and gemifloxacin, respectively. With the S. pneumoniae strains, the four fluoroquinolones exhibited similar concentration-dependent time-kill kinetics. The resistance selection frequencies of levofloxacin were higher than those of moxifloxacin at concentrations equivalent to those at the end of the dosing interval. Therefore moxifloxacin may have less of an impact on the development of resistance than levofloxacin.

Human duodenal phase III migrating motor complex activity is predominantly antegrade, as revealed by high-resolution manometry and colour pressure plots

Abstract Late phase III migrating motor complex activity has been said to be primarily retroperistaltic but has not been assessed with high resolution manometry or three-dimensional colour pressure plots (pressure/time/distance). Duodenal phase III was examined in healthy young volunteers (seven male, two female) with a 20-lumen assembly. With the most proximal sidehole in the distal antrum, after a 4.5-cm interval 18 sideholes at 1.5-cm intervals spanned the duodenum with a final sidehole 3 cm beyond. Fasting pressures were recorded until phase III occurred. Comparisons were made between proximal (P) and distal (D) duodenum during early (E) (first 0.5-1 min) and late (L) (last 0.5-1 min) phase III. With colour pressure analysis, 121 of 180 pressure wave (PW) sequences were purely antegrade, two purely retrograde and 57 bidirectional. Ten of fifty-seven bidirectional PW sequences were complex, branching to become two separate sequences. Bidirectional sequences occurred more frequently in late than early phase III (L 43 vs. E 14 of 57), but their occurrence did not differ between proximal and distal duodenum (P31 vs. D 24 of 57). Antegrade propagation velocity was faster in late compared with early phase III (L 28.50 vs. E 17.05 mm s(-1); P = 0.006), but did not differ between proximal and distal duodenum. Colour pressure analysis also indicated an intermittent segmental pattern to phase III, with each subject exhibiting a change in velocity or direction, or a relative failure of peristalsis somewhere along the duodenum during part of phase III. Duodenal phase III is not homogenous and, in contrast with previous studies, does not primarily constitute a retroperistaltic pump. Colour pressure analysis is useful in interpreting intraluminal pressure profiles and may improve the sensitivity and specificity of clinical studies.

In vitro activities of peptide deformylase inhibitors against gram-positive pathogens

The activities of six peptide deformylase (PDF) inhibitors against 107 respiratory tract pathogens were studied and compared to those of ciprofloxacin and amoxicillin-clavulanate. Against Streptococcus pneumoniae, BB-83698 and BB-83815 were the most active PDF inhibitors (MIC at which 90% of the organisms tested were inhibited [MIC(90)], 0.25 microg/ml). Five of the agents showed similar activity against Moraxella catarrhalis (MIC(90), 0.12 microg/ml). All PDF inhibitors were less active against Haemophilus influenzae; BB-3497 was the most active agent (MIC(90), 2 microg/ml). Five agents were studied against Chlamydia spp. and showed activity similar to that of ciprofloxacin (MIC, 0.5 to 4 microg/ml). This study demonstrates that PDF inhibitors have the potential to be developed for the treatment of respiratory tract infections.

The in vitro activity of BMS-284756, a new des-fluorinated quinolone

The in vitro activity of BMS-284756 (previously T-3811ME), a des-fluoro(6) quinolone, was investigated and compared with those of six other antimicrobial agents. Susceptibility tests were performed on 919 Gram-positive, Gram-negative (including nine quinolone-resistant Escherichia coli) and anaerobic bacteria, three Chlamydia isolates and four Mycobacteria spp. BMS-284756 was marginally less active against the Enterobacteriaceae, but was the most active quinolone against staphylococci, enterococci and peptostreptococci. Against Streptococcus pneumoniae, BMS-284756 and gemifloxacin were more active than other quinolones. The MIC(90) of BMS-284756 was > or = 2 mg/L for the following bacteria: E. coli (MIC(90) 16 mg/L), Acinetobacter spp. (8 mg/L), Pseudomonas aeruginosa (64 mg/L) and Enterococcus faecium (4 mg/L). The MIC of BMS-284756 for Mycobacterium spp. was within one dilution of the MIC of ciprofloxacin. BMS-284756 was markedly more active than ciprofloxacin against the Chlamydia isolates tested.

Pharmacokinetics and inflammatory fluid penetration of intravenous daptomycin in volunteers

The lipopeptide antimicrobial daptomycin was administered intravenously at a dose of 4 mg/kg of body weight to seven healthy male volunteers. The concentrations of daptomycin in plasma, cantharidin-induced inflammatory fluid, and urine were measured by a microbiological assay. The mean +/- standard deviation peak concentrations in plasma and inflammatory fluid were 77.5 +/- 8.3 and 27.6 +/- 9.5 microg/ml, respectively; the mean terminal elimination half-lives were 7.74 and 13.2 h, respectively. The overall penetration of total drug into the inflammatory fluid (measured by ratio of the area under the concentration-time curve from 0 to 24 h for inflammatory fluid compared with that for plasma) was 68.4%. The mean urinary recovery over 24 h was 59.7%.

Single-dose pharmacokinetics and penetration of BMS 284756 into an inflammatory exudate

The pharmacokinetics of a single dose of BMS 284756 were determined following oral administration of a 600-mg dose to eight healthy male volunteers. Concentrations of the drug were measured in plasma and a cantharidine-induced inflammatory exudate by a microbiological assay. The mean peak concentration in plasma of 10.4 microg/ml (standard deviation [SD], 1.3 microg/ml) was attained at a mean time of 1.2 h (SD, 0.5 h) after the dose. The penetration into the inflammatory exudate was 82% (SD, 15.7%). A mean peak concentration of 7.2 microg/ml (SD, 2.4 microg/ml) was attained in the inflammatory exudate at 5.3 h (SD, 1.5 h). The elimination half-lives from plasma and inflammatory fluid were 9.8 h (SD, 1.1 h) and 8.5 h (SD, 1.9 h), respectively. The areas under the concentration-time curves for plasma and inflammatory fluid were 96.7 microg x h/ml (SD, 10.3 microg x h/ml) and 77.9 microg x h/ml (SD, 19.2 microg x h/ml), respectively.

Activity of daptomycin against Gram-positive pathogens: a comparison with other agents and the determination of a tentative breakpoint

The in vitro activity of daptomycin was studied in comparison with other agents active against 328 recent clinical isolates of Gram-positive pathogens. MIC data showed that the addition of calcium ions to a final concentration of 50 mg/L enhanced the activity of daptomycin generally by eight- to 16-fold. In the presence of calcium ions daptomycin was uniformly active against the strains of Staphylococcus spp. and Streptococcus spp. studied with a MIC90 of < or = 1 mg/L. Enterococcus faecalis and Enterococcus faecium were slightly less susceptible (MIC90 2 mg/L). Vancomycin-, fluoroquinolone- and quinupristin/dalfopristin-resistant strains were all susceptible to daptomycin. The presence of serum reduced the apparent activity of daptomycin to only a moderate extent. Employing the BSAC methodologies, a tentative breakpoint of 2 mg/L for daptomycin is proposed.

Effect of a lacto-ovo vegetarian diet on fasting small intestinal motility

BACKGROUND

Changes in diet can alter gastric and small intestinal (SI) motility. The effects of a vegetarian diet on fasting SI motility are unknown.

METHODS

Manometric studies were performed in 9 lacto-ovo vegetarians (7 women) and 9 omnivores (7 women) of similar age and body mass index. On each study day, manometry was used to assess SI motility for 5 h, or 3 complete cycles of the interdigestive motor complex (IDMC). Lacto-ovo vegetarians were studied once: omnivores were studied twice, on their usual diet, and after consuming a 14-day lacto-ovo vegetarian diet. Diet diaries were kept for 5 days prior to each manometric study. Data were analysed for dietary composition and for cycle length and duration of each phase (I, II and III) of the IDMC.

RESULTS

Dietary intake did not differ between chronic vegetarians and chronic omnivores apart from a trend to higher fibre intake (29 +/- 3 versus 20 +/- 3 g/day; P = 0.058). Omnivores eating a vegetarian diet showed a trend to decreased alcohol consumption (P = 0.068), but did not increase their fibre intake (20 +/- 3 versus 21 +/- 3 g/day). Neither cycle length nor duration of each IDMC phase differed between chronic vegetarians and chronic omnivores. After 14 days of a vegetarian diet, omnivores had a reduction in cycle length (128 +/- 19 versus 86 +/- 12 min; P = 0.02), with a non-significant reduction of Phase II (99 +/- 20 versus 50 +/- 8 min: P = 0.066).

CONCLUSIONS

A chronic vegetarian diet has no major effect on fasting SI motility; but acute dietary change may alter the cycle length and component phases of the IDMC.

Determination of minimum inhibitory concentrations

Minimum inhibitory concentrations (MICs) are defined as the lowest concentration of an antimicrobial that will inhibit the visible growth of a microorganism after overnight incubation, and minimum bactericidal concentrations (MBCs) as the lowest concentration of antimicrobial that will prevent the growth of an organism after subculture on to antibiotic-free media. MICs are used by diagnostic laboratories mainly to confirm resistance, but most often as a research tool to determine the in vitro activity of new antimicrobials, and data from such studies have been used to determine MIC breakpoints. MBC determinations are undertaken less frequently and their major use has been reserved for isolates from the blood of patients with endocarditis. Standardized methods for determining MICs and MBCs are described in this paper. Like all standardized procedures, the method must be adhered to and may not be adapted by the user. The method gives information on the storage of standard antibiotic powder, preparation of stock antibiotic solutions, media, preparation of inocula, incubation conditions, and reading and interpretation of results. Tables giving expected MIC ranges for control NCTC and ATCC strains are also supplied.

BSAC standardized disc susceptibility testing method

For nearly a decade microbiologists have used the MIC breakpoints published in the BSAC Guide to Susceptibility Testing to interpret susceptibility. Historically, and unlike the rest of Europe, the UK and Ireland have used a comparative method of disc testing to interpret susceptibility rather than one based on a correlation between MIC and zone of inhibition. Although innovative when introduced in the 1970s, Stokes' comparative method has evolved ad hoc and it has become increasingly apparent that there is a need for a standardized method of disc testing that is correlated with BSAC MIC breakpoints. The method described here, like all other standardized methods of disc testing, cannot be adapted by the user, and interpretative criteria are only applicable if the method is adhered to fully. A major advantage of this approach to susceptibility testing is that data from several sources can be combined for surveillance of resistance, a task that has been made much easier by the introduction of this method and coincides with the availability of automated zone measuring devices. It is hoped that the method described here will provide the core document for standard operating procedures; however, changes will necessarily occur over time as the method is developed and refined.

The development of the BSAC standardized method of disc diffusion testing

The BSAC Working Party on Susceptibility Testing has developed a standardized method of disc susceptibility testing that has been 'field tested' in 19 diagnostic laboratories in the UK and Ireland. The method employs semi-defined media, a semi-confluent inoculum and relates zones of inhibition with BSAC-specified MIC breakpoints to interpret susceptibility. The bacteria selected for the trial included clinical isolates and control strains from the ATCC and NCTC national collections. Organisms were chosen because they had known attributes, such as being fully susceptible or having a demonstrated mechanism of resistance. The results from this survey are very encouraging. With the commonly isolated Enterobacteriaceae, specifically Escherichia coli, Proteus mirabilis and Klebsiella spp., no major problems were observed except with gentamicin and cefuroxime. In the case of gentamicin, problems were associated with resistant strains of P. mirabilis, with MICs of 2 mg/L, being falsely reported as susceptible. For cefuroxime, it is not unexpected that results were unreliable, as the MIC distribution straddles the in vitro breakpoint concentration (following the results of this study the MIC and zone diameter breakpoints have been amended to improve reporting). No major problems were encountered for Pseudomonas aeruginosa with the agents studied. The 'field survey' has shown that disc testing is unreliable for determining the susceptibility of coagulase-negative staphylococci to teicoplanin, and that the detection of glycopeptide resistance in enterococci is improved by incubation for a full 24 h. Inconsistencies observed with fastidious organisms were associated with incorrect inocula. Zone diameter data for the control strains studied provide information that can be utilized by diagnostic laboratories to monitor the daily performance of testing.

Lung concentrations of telithromycin after oral dosing

Concentrations of telithromycin were measured in plasma, bronchial mucosa (BM), epithelial lining fluid (ELF) and alveolar macrophages (AM) following multiple oral doses. Concentrations were determined using a microbiological assay. There were 20 subjects in the study, allocated to three nominal time periods: 2, 12 and 24 h. Mean concentrations in plasma, BM, ELF and AM for 2, 12 and 24 h were as follows: 2 h, 1.86 mg/L, 3.88 mg/kg, 14.89 mg/L and 69.32 mg/L; 12 h, 0.23 mg/L, 1.41 mg/kg, 3.27 mg/L and 318.1 mg/L; and 24 h, 0.08 mg/L, 0.78 mg/kg, 0.97 mg/L and 161.57 mg/L. These concentrations of telithromycin in BM and ELF exceeded for 24 h the mean MIC90s of the common respiratory pathogens Streptococcus pneumoniae (0.12 mg/L) and Moraxella catarrhalis (0.03 mg/L), as well as the atypical microorganism Mycoplasma pneumoniae (0.001 mg/L), and suggest that telithromycin may be effective for the treatment of community-acquired pneumonia and chronic obstructive pulmonary disease.

Pharmacokinetics and tissue penetration of gemifloxacin following a single oral dose

The pharmacokinetics and tissue penetration of gemifloxacin were determined during a 24 h period following oral administration of a single 320 mg dose to each of 10 healthy male volunteers. Concentrations of the drug in plasma, inflammatory blister fluid and urine were determined using a microbial assay. A peak plasma concentration (mean +/- S.D.) of 2.33 +/- 0.5 mg/L was reached at 1.20 +/- 0.4 h. Mean penetration into inflammatory fluid was 61.19 +/- 10.4%. A peak concentration of 0.74 +/- 0.3 mg/L was reached in the inflammatory fluid at a mean time of 3.40 +/- 1.7 h. The mean elimination half-life from serum and inflammatory fluid was 5.94 +/- 0.4 and 6.27 +/- 2.4 h, respectively. Urinary excretion of the drug at 24 h post-dose was 36.11% of the total given. These results demonstrate that gemifloxacin penetrates into the site of inflammation and reaches sufficient concentrations to inhibit many pathogens.