Automated blood culture systems

This review compares automated systems of blood culture for the detection of positive bottles, excluding mycobacteria. The performance of different systems is influenced by several key variables, including volume of the blood sample, the use of resins, shaking to increase the recovery of aerobic microorganisms, duration of incubation and final subculture. The Bactec, BacT/Alert, BioArgos and ESP systems require further study and technical improvement. There is no single ideal system of blood culture, and combinations of two or more methods are likely to provide the best results

Post-antibiotic effect of three quinolones against gram negative isolates from urine

he post-antibiotic effect (PAE) is defined as the bacterial growth suppression which persists after a limited exposure to an antimicrobial agent. The PAE and the bactericidal effect of the quinolones ciprofloxacin, norfloxacin and nalidixic acid have been studied against several urinary isolates of Gram-negative bacteria. The PAE was determined after one hour's exposure to the antimicrobial agent using an initial inoculum of 10(5) to 10(6) cfu/ml; the drug was rapidly removed by a 10(-2) dilution technique in antibiotic-free medium. When ciprofloxacin was used at four times its MIC the PAEs were 1.37 +/- 0.09; 2.45 +/- 0.63 and 2.86 +/- 0.15 h against Esch. coli, Klebs. pneumoniae and Pseudomonas aeruginosa, respectively. We found lower values for norfloxacin under the same conditions, and nalidixic acid did not induce a significative PAE. These results could support changes in dosing intervals of norfloxacin and ciprofloxacin, with possibly greater intervals between doses

Reliability of four methods for the diagnosis of acute infection by Epstein-Barr virus

We studied the reliability of new indirect tests in the diagnosis of acute infection by Epstein-Barr virus (EBV). Studied for all samples were method 1, the heterophil antibodies (Abs) (Monolatex, Biokit, Germany); method 2, the IgM Abs to EBV with ELISA tests (antigen pools, Enzygnost, Behring-werke, Germany); method 3, EA (Biotest Diagnostics, Germany); and method 4, the IgG avidity test. The reliability of the four tests for the detection of primary infection by EBV was: sensitivity (method 1: 89.1%; method 2: 100%; method 3: 79.7%; method 4: 99%); specificity (method 1: 98%; method 2: 100%; method 3: 84%; method 4: 100%); positive predictive value (method 1: 97.6%; method 2: 100%; method 3: 73.6%; method 4: 100%), and negative predictive value (method 1: 90.7%; method 2: 100%; method 3: 84%; method 4: 99%). The IgG avidity test (method 4) is simple and automated in the laboratory and is very useful for ascertaining, from a single sample, the time since infection. It is criteria of recent primoinfection higher levels than 55% of IgG with low avidity for the antigen. The investigation of the Abs to antigen pools (method 2) by ELISA of virus had a high reliability, but the investigation of heterophil Abs by latex (method 1) and the Abs IgM to EA (method 2) were lacking in sensibility regarding their use in the diagnosis of the primoinfection

Detection of IgA and low-avidity IgG antibodies for the diagnosis of recent active toxoplasmosis

OBJECTIVE: To determine the clinical value of testing IgA and the avidity of IgG (by two commercial systems) for the detection of recent active toxoplasmosis (RAT), and to study the IgG avidity during the course of infection. METHODS: The IgA was tested by a capture ELISA (Pasteur, France) and the avidity of IgG was determined by two modified commercial indirect ELISA methods (Sorin, Italy; Behringwerke, Germany) in 12 patients who were not immunosuppressed (group I) and 57 healthy subjects with a past infection by Toxoplasma gondii (group II). RESULTS: IgA was present in 75% of patients from group I and 21% of subjects from group II. The reliability for diagnosis of RAT was: sensitivity 75%, specificity 84%, positive predictive value 52.9% and negative predictive value 93.3%. In group I, 91.7% of patients had more than 50% low-avidity IgG, by both methods; in group II, 21% of subjects had low-avidity IgG at levels from 40% to 50%, by both methods. The diagnostic reliability of the two methods for the detection of low-avidity IgG in the first samples of RAT was similar when a breakpoint of 50% was used, with values of: sensitivity 91.7%, specificity 100%, positive predictive value 100% and negative predictive value 98%. CONCLUSIONS: The study of IgA is not on its own adequate for diagnosis of RAT. However, testing the avidity of IgG is more reliable for the diagnosis of RAT, in studies of one serum sample or sequential samples

High incidence of extended-spectrum β-lactamases among outpatient clinical isolates of Escherichia coli: a phenotypic assessment of NCCLS guidelines and a commercial method

The production of extended-spectrum beta-lactamases (ESBLs) among 357 clinical isolates of Escherichia coli and 175 of Klebsiella spp. was studied using both the National Committee for Clinical Laboratory Standards disk diffusion method and the semiautomated Wider system. We highlight the predominance of E. coli (50, 92.6%) among positive samples and the largely outpatient origin of these (40, 80%), including 39 samples of urine (97.5%) and one of urethral exudate. There were only four ESBL-producing isolates of Klebsiella spp. (7.4%), and three were in outpatient urine samples (75%, 2 K. oxytoca and 1 K. pneumoniae). The positive and negative predictive values for the Wider system were 81% and 98.5%, respectively. We stress the high incidence of ESBL in our setting, the predominance of cases in the outpatient setting, and the acceptable detection of ESBL by means of the Wider system in E. coli and Klebsiella spp

Three-year study of antibody to Borrelia burgdorferi in southern Spain

The prevalence of anti-Borrelia burgdorferi antibodies was studied in Granada, Spain, between January 1991 and November 1993 in 354 patients with suspected Lyme disease (group 1); in 50 patients either with syphilis (n = 32) or without syphilis but with a positive Rapid Plasma Reagin test (n = 18) (group 2); and in 150 healthy subjects (group 3). In addition, intrathecal antibody production was evaluated by EIA in CSF samples obtained from 117 patients in group 1. Anti-Borrelia burgdorferi antibodies were detected by EIA in 58 patients (16.4%) in group 1, 29 (8.2%) of whom were positive by Western blot. Intrathecal antibody production was detected in one patient. In group 2, 8 (16%) patients had a positive EIA result, but none of these was confirmed by Western blot. western blot was negative for all subjects in group 3. The results of this study indicate that anti-Borrelia burgdorferi antibodies are not uncommon in our area, although Lyme disease is rare

Antibodies to Borrelia burgdorferi in European populations

We compared the antibodies to B. burgdorferi in three different populations in order to evaluate the diagnostic reliability of Lyme borreliosis serologic analysis. The subjects included 25 patients with Lyme borreliosis (Group 1); 50 patients with diseases of unknown cause, B. burgdorferi ELISA-positive in serum and without B. burgdorferi infection (Group 2); and 1,251 individuals without Lyme borreliosis (Group 3). All samples were tested for B. burgdorferi B31 and B. afzelii antigens using ELISA. The positive results of the ELISA B. burgdorferi B31 assay were confirmed with Western blot for the same strain. In Group 3, 162 (12.9%) patients were ELISA positive for B. burgdorferi B31, while only 6 (0.6%) patients had IgG ELISA antibodies to B afzelii. Bands in WB were detected in 104 (8.4%) of the Group 3 subjects. The bands found to be most reliable for the identification of strain B. burgdorferi B31 by IgG WB were those representing the 93, 39, 34, and 23-kDa proteins. Our results show that serologic diagnosis of Lyme borreliosis is far from clearly established. To date, the only reliable criteria are clinical ones correlated with laboratory evidence

Chlamydia pneumoniae DNA in the arterial wall of patients with peripheral vascular disease

Background: Chlamydia pneumoniae is a human respiratory pathogen that has recently been related to the genesis of symptomatic atherosclerosis. C. pneumoniae has been studied more widely in relation to coronary atherosclerosis than to peripheral arterial occlusive disease (PAOD). The present study aimed to retrospectively analyze the presence of C. pneumoniae DNA in patients with PAOD. Materials and methods: A seminested PCR method was applied on 85 samples from 71 patients with PAOD secondary to surgical treatment. The control group comprised 50 patients with chronic superficial venous insufficiency who required varicose resection surgery. Results: The number of patients, number of samples studied and percentage of patients found to be positive in the PCR study were 17, 18 and 59%, respectively, for arteries of the lower extremities; 15, 16 and 60% for aneurysm of the abdominal aorta; 22, 23 and 73% for carotid stenosis and 17, 18 and 65% for aortic stenosis. C. pneumoniae DNA was found in six external pudendal arteries (12%) of the control group, significantly lower than the incidence in the patient group (p < 0.0001). Conclusion: A causal relationship between chronic C. pneumoniae infection and PAOD cannot be ruled out. On the contrary, the high incidence of C. pneumoniae DNA detected in our patients suggests that C. pneumoniae infection may play some role in the pathogenesis of peripheral vascular disease

Activity in vitro of twelve antibiotics against clinical isolates of extended-spectrum beta-lactamase producing Escherichia coli

Twelve beta-lactam and non-beta-lactam antibiotics were evaluated against 115 clinical isolates of extended-spectrum beta-lactamase-producing (ESBLs) Escherichia coli using a broth microdilution test in accordance with the CLSI guidelines. Susceptibility was 100% with imipenem, ertapenem and amikacin, 95.7% with piperacillin-tazobactam, 91.3% with cefoxitin, 87% with tobramycin, 81.7% with amoxicillin-clavulanate, 80% with cefepime, 67.8% with ceftazidime, 27.8% with ciprofloxacin, 27% with levofloxacin and 13% with ceftriaxone. Ertapenem was the antibiotic with the lowest minimum inhibitory concentrations (MICs) for all isolates. There were no clinically relevant differences in the activity of the antibiotics in the presence of CTX-M-9 or SHV enzymes

Multiple sclerosis and human herpesvirus 6

This study was supported by the Health Council of Andalusian Regional Goverments, project 141/2001 and the Spanish Federation of Multiple Sclerosis.Background: A possible but as yet unproven relationship has been proposed between the onset or persistence of multiple sclerosis (MS) symptoms and herpesviruses, including, most recently, human herpesvirus 6 (HHV-6). A study was conducted to investigate the presence of HHV-6 DNA and the synthesis of antibodies against HHV-6, cytomegalovirus (CMV) and Epstein-Barr virus (EBV) in serum and cerebrospinal fluid (CSF) of patients with MS. Materials and methods: PCR and ELISA were used to detect HHV-6 DNA and specific antibodies against HHV-6, CMV and EBV in 211 samples (139 sera and 72 CSF). There were three groups of samples: group I, paired samples of serum and CSF from 41 MS patients; group II, paired samples of serum and CSF from 31 patients with neurological diseases other than MS (OND); group III, 67 serum samples from 27 different MS patients undergoing serologic follow-up. Results: No HHV-6 DNA was found in any sample. Group I sera showed elevated anti-HHV-6 IgG and IgA levels. In group II, anti-CMV IgG was detected in one CSF sample and anti-HHV-6 IgM in one serum sample. Group III sera showed high concentrations of anti-HHV-6 IgG, IgA and IgM. Conclusion: Given the clinical implications of the presence of antibodies against HHV-6 in MS patients, a viral reactivation cannot be excluded as an environmental factor.Health Council of Andalusian Regional Goverments, project 141/2001Spanish Federation of Multiple Sclerosi