Neurological complications of chlamydial infections: case report and review

We describe a patient with Chlamydia pneumoniae infection who presented with cerebellar dysfunction, followed by respiratory failure requiring mechanical ventilation. C. pneumoniae is an important respiratory pathogen, and other clinical manifestations, including neurological syndromes, are being increasingly recognized. Meningoencephalitis and other neurological complications have also been described in patients with infections due to Chlamydia psittaci and Chlamydia trachomatis. Chlamydial infections should be included in the differential diagnosis of neurological syndromes, including cerebellar dysfunction.

The postantibiotic effect of fusidic acid against gram-positive bacteria

The in-vitro postantibiotic effect (PAE) of fusidic acid was tested for six strains of Staphylococcus aureus and four strains of Streptococcus pyogenes. The maximum PAE that could be achieved was more than 3 h, but at concentrations of antibiotic attainable in humans, the PAE was less than 2 h. Additional experiments were performed in albumin, to examine the effect of the strong protein binding of fusidic acid on the MIC and PAE. MICs were increased, but at the same multiple of the MIC, PAEs were similar to those performed in Mueller-Hinton broth.

The postantibiotic effect of imipenem: relationship with drug concentration, duration of exposure, and MIC

The postantibiotic effect (PAE) of imipenem against Escherichia coli was measured at a wide variety of drug concentrations and times of exposure. We observed that the area under the concentration-time curve of drug exposure (AUC), the product of time of exposure and concentration of drug, is a much better predictor of the duration of the PAE than either parameter alone. We also measured the PAE of imipenem against strains of gram-positive and gram-negative bacteria for which MICs varied widely. The E50, the AUC required to produce 50% of the maximum PAE, is correlated with the MIC and is independent of species. This may explain why the duration of the PAE differs for bacteria of the same species for which MICs are different.

Disc susceptibility testing for thermomphilic campylobacters

The minimum inhibitory concentrations (MICs) and zone diameters around NCCLS strength discs of 100 clinical isolates of thermophilic Campylobacter species, including 79 strains of Campylobacter jejuni subsp. jejuni, 19 of C. coli and two of C. lari, plus three type strains of these species, were determined for erythromycin, clindamycin, nalidixic acid, norfloxacin, ciprofloxacin, ampicillin, piperacillin, cephalothin, ceftriaxone, chloramphenicol, gentamicin and tetracycline. Using error-rate bounded analysis and adjustment of MIC breakpoints to fit natural populations, tentative interpretive zone diameter criteria were set for each of the antimicrobials. Application of these criteria showed that resistance to quinolones was not detected in species other than C. lari. Two strains of C. jejuni subsp. jejuni were susceptible to cephalothin. The type strain of C. lari was susceptible to erythromycin and resistant to clindamycin. Full resistance to erythromycin, chloramphenicol or gentamicin was not found in any strain, while nine strains were resistant to tetracycline. This disc method should provide a simple approach to resistance detection for surveillance or routine testing of invasive isolates.

Selection of optimum laboratory tests for the identification of Moraxella catarrhalis

We evaluated a variety of conventional and rapid tests and examined the erythromycin susceptibility of a collection of Moraxella catarrhalis and commensal neisseria strains in order to determine the optimum method for routine identification. One hundred and fifty three strains were tested by Gram stain, catalase, oxidase, carbohydrate degradation by two methods and the presence of esterases using indoxyl acetate, 4-methylumbelliferyl butyrate (MUB). Tween 80 and tributyrin as substrates. Erythromycin MICs and zone diameters around 1, 5 and 15 micrograms discs were determined by the NCCLS method for 151 of the strains. A combination of Gram stain, oxidase and either indoxyl acetate, spot MUB or tributyrin hydrolysis test proved to be reliable and potentially the most convenient for routine testing. MICs and zone diameters easily distinguished between the erythromycin-sensitive M. catarrhalis and the erythromycin-resistant commensal neisserias and would provide confirmation of identification if used for susceptibility testing.

Bactericidal activity and synergy studies of proton pump inhibitors and antibiotics against Helicobacter pylori in vitro

The bactericidal activity of the proton pump inhibitors omeprazole and lansoprazole alone and in combination with a beta-lactam or macrolide antibiotic were investigated in vitro. Time-kill curves against Helicobacter pylori NCTC 11637 and a recent clinical isolate revealed significant concentration-dependent killing with all drugs other than amoxycillin. Combinations of proton pump inhibitor and erythromycin showed synergic activity. In contrast, proton pump inhibitor plus amoxycillin showed additive activity against the clinical isolate only. Bactericidal investigations of anti-helicobacter drugs in vitro may suggest optimum treatment strategies for this common infectious disease.

Risk factors for adverse cutaneous reactions associated with intravenous vancomycin

We retrospectively studied adverse cutaneous reactions associated with intravenous vancomycin therapy over a 14-month period when two different brands of vancomycin were used. Of 224 adults, 12 (5.4%) had infusion-related reactions; ten of 174 patients who received more than one day of vancomycin (5.7%) had delayed cutaneous reactions. Age less than 40 years was a risk factor for both infusion-related and delayed reactions by both univariate and multivariate analysis. Duration of therapy greater than 7 days was a risk factor for delayed reactions. There was a significant increase in adverse cutaneous reactions associated with the use of a particular batch of vancomycin, although analytical testing of this batch failed to identify any difference from other batches associated with routine rates of adverse reactions. Awareness of vancomycin-associated infusion-related and delayed cutaneous reactions is necessary, and the risk factors associated with these reactions may have important clinical implications.

Oxygen concentration influences proton pump inhibitor activity against Helicobacter pylori in vitro

Omeprazole and lansoprazole are proton pump inhibitors that have shown activity against Helicobacter pylori and other Helicobacter species when tested by agar dilution. Lansoprazole was more active against H. pylori than was omeprazole, and the activity was independent of urease production. Disk susceptibility tests and agar dilution MIC determinations were performed to investigate the effects of incubation under different sets of atmospheric conditions on H. pylori inhibition. Oxygen concentration was found to influence proton pump inhibitor activity in vitro, with higher concentrations leading to greater susceptibility. The method of testing is important in determining the anti-Helicobacter activity of proton pump inhibitors.

Disk diffusion interpretive criteria for fusidic acid susceptibility testing of staphylococci by the National Committee for Clinical Laboratory Standards method

Fusidic acid is used in many countries for the treatment of multiresistant staphylococcal infection, especially multiresistant Staphylococcus aureus infection (MRSA). We collected consecutive fusidic acid-resistant isolates of staphylococci from the routine laboratory over several years, and compared these strains with fusidic acid-susceptible staphylococci to establish interpretive criteria for disk diffusion testing by National Committee for Clinical Laboratory Standards (NCCLS) methods. The minimum inhibitory concentrations (MICs) and zone diameters for strains of S. aureus (n = 102), including MRSA, S. saprophyticus (n = 20) and other coagulase-negative staphylococci (n = 115) were determined by NCCLS agar dilution and disk diffusion tests using a 2.5-micrograms disk of fusidic acid. MICs were bimodally distributed. No isolates had MICs of 0.5 or 1 microgram/ml; thus, we chose these values to define strains of intermediate susceptibility. The error-rate-bounded method was used to determine interpretive zone diameters for disk testing. Interpretive zone diameter criteria were found to be: susceptible > or = 22 mm, intermediate 18-21 mm, and resistant < or = 17 mm. All S. saprophyticus were intrinsically resistant to fusidic acid (MIC > or = 2 micrograms/ml).

A meta-analysis of studies on the safety and efficacy of aminoglycosides given either once daily or as divided doses

We performed a meta-analysis of randomised clinical studies in which the efficacy and toxicity of the same total daily dose of aminoglycosides administered once-daily was compared with multiple divided daily dosing for treating human infections. Of twenty-eight publications identified from a literature search using Medline 19 publications of 20 study comparisons involving 2881 patients met the criteria for analysis. Netilmicin was investigated in 11 studies, amikacin in seven studies and gentamicin in two studies but no studies of tobramycin met the inclusion criteria. The meta-analysis showed that there was a small, statistically significant difference in clinical efficacy of 3.5% (95% confidence intervals 0.5% to 6.5%, P = 0.027) in favour of once-daily administration but no significant differences in bacteriological efficacy or nephrotoxicity were detected. Auditory and vestibular toxicity rates were low for all agents and no differences in these toxicities were identified between once-daily or multiple-dose administration regimens either clinically or by audiometry or electronystagmography. Aminoglycosides can be given once-daily without loss of efficacy or increased toxicity offering greater simplicity and potentially improved cost-effectiveness than can be achieved by giving these drugs in divided doses.

Evolution of resistance in Staphylococcus aureus in Australian teaching hospitals. Australian Group on Antimicrobial Resistance (AGAR)

OBJECTIVE

To assess the changes in antibiotic resistances in Staphylococcus aureus, both methicillin-susceptible and methicillin-resistant strains, in Australia.

DESIGN

Retrospective review of data collected annually.

SETTING

Twenty metropolitan teaching hospitals in the six States of Australia and the Australian Capital Territory from 1988 to 1994.

OUTCOME MEASURES

Changes in prevalence and resistance rates of methicillin-resistant S. aureus (MRSA) and methicillin-susceptible strains, based on antibiotic susceptibility testing of clinical isolates of S. aureus.

RESULTS

Prevalence of MRSA has remained constant on the eastern seaboard of Australia. A distinctive strain of MRSA emerged in Western Australia which had different antimicrobial susceptibilities. Resistances emerged in MRSA strains from eastern Australia, principally to ciprofloxacin and rifampicin, while resistance to fusidic acid remained stable and resistance to chloramphenicol significantly declined. Resistances in methicillin-susceptible strains remained fairly stable, except for a decline in resistance levels for tetracycline. High levels of resistance were seen to penicillin, moderate levels to erythromycin and low levels to trimethoprim and fusidic acid in methicillin-susceptible strains.

CONCLUSIONS

The continued high prevalence of and increasing resistance in MRSA in some Australian hospitals have meant that some strains are now untreatable with oral antibiotics.

Synthesis and Antibacterial Activity of Some 'Bisquinolones'

Ten ' bisquinolones' were prepared by joining two molecules of norfloxacin, or 1,8-naphthyridine and benzo [c][1,8] naphthyridine derivatives, with various aliphatic linkers. These were tested against 17 bacteria strains but none showed more than slight activity (MIC ≥ 10 mg/l). However, a 'monoquinolone' derived from benzo [c][1,8] naphthyridine showed greater activity than norfloxacin against a strain of Acinetobacter.

Evaluation of API Campy in comparison with conventional methods for identification of thermophilic campylobacters

API Campy was compared with conventional biochemical methods for its ability to identify 100 thermophilic campylobacter isolates. When the results were read according to the manufacturer's instructions, API Campy showed 92% agreement with conventional methods. Extended incubation of the assimilation strip resulted in the correct identification of an additional two isolates. Discrepant results occurred for six isolates. Overall, API Campy offered no advantages over conventional methods.

Pharmacodynamic (kinetic) considerations in the treatment of moderately severe infections with cefotaxime

Information about the pharmacodynamics of beta-lactams has accumulated rapidly over the last 20 years, and their application to cefotaxime are discussed in this review. Application of pharmacodynamics requires an integration of the pharmacokinetic and in vitro properties of the agent. Cefotaxime is similar to other beta-lactams in that it has little concentration-dependent killing and produces no postantibiotic effect against Gram-negative bacteria. However, it has a microbiologically active metabolite, deascetylcefotaxime, which can show synergy, partial synergy, or an additive effect in combination with the parent drug. More than any other technique, animal models have been able to elucidate the pharmacokinetic parameters that predict efficacy in vivo. They have shown that for beta-lactams it is the time that levels exceed the minimum inhibitory concentration (MIC) that is the most important determinant of efficacy. For bacteria to have no postantibiotic effect, plasma levels need to exceed the MIC for the whole of the dosing interval to achieve maximum killing at the site of infection. When applying these concepts as the most stringent criteria for efficacy using pharmacokinetic values from young, healthy volunteers, it can be shown that organisms with MICs of < or = 0.03 microgram/ml for a 1-g dose and 0.06 microgram/ml for a 2-g dose to achieve optimum efficacy with 12-h dosing of cefotaxime. However, two clinical studies have demonstrated trough levels much greater than would be predicted from these pharmacokinetic values, as a result of the effects of decreased renal function accompanying sepsis and older age. These studies showed that organisms with MICs < or = 1 microgram/ml for a 1-g dose or 2 micrograms/ml for a 2-g 12-h dose were covered for the whole of the dosing interval. Thus, all strains of Enterobacteriaceae and pathogenic Neisseria spp. that lack resistance mechanisms to third-generation cephalosporins would be covered using 12-h dosing schedules.

The postantibiotic effect of antifungal agents against common pathogenic yeasts

A total of ten strains of Candida spp. and Cryptococcus neoformans were examined for the presence of the postantibiotic effect (PAE) after 0.5-2 h exposure to amphotericin B, 5-fluorocytosine, miconazole and ketoconazole. Significant PAEs were observed for amphotericin B and 5-fluorocytosine, but none for the imidazoles. The duration of the PAEs of amphotericin B ranged from 0.5-10.4 h for the Candida spp. and 2.8-10.6 h for the cryptococcos, while 5-fluorocytosine induced PAEs from 0.8-7.4 h and 2.4-5.4 h, respectively. Even though no PAEs were demonstrated for the imidazoles, the growth rate was persistently reduced by continuous exposure to concentrations as low as 1/1000 of the MIC of these agents. These findings may have implications for dosing antifungal agents in systemic yeast infections.

Investigation of hematuria at a printing company

An investigation was undertaken at a printing company into an apparently high prevalence of trace dipstick hematuria discovered during routine medical examinations. In both the printing employees (n = 225) and a control group (n = 118) from other industries, the prevalence of hematuria exceeded that described in most previous reports (31% and 25%, respectively, using the criterion of > 12 glomerular red cells or > 2 nonglomerular red cells/microliter of urine). No focus of abnormality was identified within the printing plant and no association was identified between reported exposure to potentially toxic substances and the degree of hematuria. An occupational hygiene inspection and medical follow-up of selected workers did not reveal any significant abnormalities. The limitations of available information concerning "normal" urinalysis results suggests that hematuria may not be a useful test for the screening of occupational groups at risk of bladder cancer.