Comparative study on antagonistic effects of low pH and cation supplementation on in-vitro activity of quinolones and aminoglycosides against Pseudomonas aeruginosa

The antagonistic effects of physiological levels of Ca++ and Mg++ on the in-vitro activity of aminoglycosides and quinolones against Pseudomonas aeruginosa were studied at both pH 7.4 and 5.5. Adding Mg++ and Ca++ (100 mg/l) to commercial media deficient of these cations increased the MICs and MBCs of ciprofloxacin and enoxacin four-fold (2 P < 0.01), which was significantly less than the 16-fold increase found for gentamicin and netilmicin (2 P < 0.01). However, the activity of both aminoglycosides and quinolones was similarly affected by reducing the pH to 5.5 (giving eight-fold increases in MICs) or by the combination of both low pH plus cation supplementation (giving 16-fold increases in MICs). These data raise the question whether antagonizing factors should be considered not only for aminoglycosides, but also for quinolones during routine susceptibility tests on P. aeruginos

Long term accuracy of fluorescence polarization immunoassays for gentamicin, tobramycin, netilmicin and vancomycin

External quality control was performed during six years to determine the accuracy over time of the Abbott TDx fluorescence polarization system for assaying antibiotics. Unknown spiked serum samples of gentamicin, tobramycin, netilmicin and vancomycin were provided monthly by the British national external quality assessment scheme. Comparison of the 209 assay results with the target concentrations showed good correlations in all four assays. No significant deviations from linearity, from slope 1·0, and from intercept 0·0 were detected by regression analysis. Relative deviations were <10% and <15% for 78% and 90% of all specimens, respectively. On an average the same calibration curves could be used over a period of 19 weeks . Fluorescence polarization immunoassays provided rapid and reliable results over the entire study perio

Intestinal Coinfection with Enterocytozoon bieneusi and Cryptosporidium in a Human Immunodeficiency Virus-Infected Child with Chronic Diarrhea

The microsporidian Enterocytozoon bieneusi has been recognized as an important cause of chronic diarrhea in severely immunodeficient adults infected with human immunodeficiency virus (HIV). We report the first case of intestinal E. bieneusi infection in a child. The 9-year-old boy with connatal HIV infection presented with failure to thrive, chronic diarrhea, and intermittent abdominal pain. His CD4 lymphocyte count was 0.05 × 109/L and dropped to 0.01 × 109/L. No HIV-associated opportunistic infection other than oral hairy leukoplakia and oral candidiasis had been found before microsporidia were detected. Treatment of microsporidiosis with albendazole was of no benefit. During follow-up, the boy also developed intestinal cryptosporidiosis. Evaluation of chronic diarrhea in severely immunodeficient HIV-infected children should include examination for intestinal microsporidia. We recommend the use of a new coprodiagnostic technique that allows detection of microsporidial spores in stool specimens. Furthermore, consideration of dual or even multiple parasitic infections in the differential diagnosis of chronic diarrhea may have both important clinical and epidemiological implication

Extrapulmonary and Disseminated Infections Due to Mycobacterium malmoense: Case Report and Review

Mycobacterium malmoense is a potentially pathogenic species that was first described in 1977. During the past decade M. malmoense has been recognized with increasing frequency as a pulmonary pathogen. More than 180 cases of M. malmoense infection have been reported. Most of these infections affected a previously damaged lung. Other infection sites included the skin, lymph nodes, and bursae. Five cases of disseminated infection have been reported. The antituberculous drugs associated with the most favorable susceptibility patterns are rifampin and ethambutol. Because of the slow growth of M. malmoense on conventional, egg-based bacteriologic media, the incubation time should be >6 weeks; special solid and liquid media are recommended. We report a case of disseminated pulmonary and gastrointestinal infection due to M. malmoense in a patient with AIDS, who was treated successfully with a combination of rifabutin (ansamycin), clofazimine, and isoniazid. In addition, we review the characteristics of extrapulmonary and disseminated infections due to M. malmoens

A Method for the Quantification of Intracellular Zidovudine Nucleotides

An assay to quantify the phosphorylation products of zidovudine (AZT) in peripheral blood mononuclear cells (PBMC) was developed. Extracts of PBMC were separated by high-performance liquid chromatography. Eluted AZT mono- (MP), di- (DP), and triphosphate (TP) were collected in separate portions. Treatment with alkaline phosphatase yielded equimolar amounts ofAZT, which after solid-phase enrichment were assayed by radioimmunoassay. Detection limit was 0.1 pmol/106 PBMC for each nucleotide. Recoveries of 102%-118% were observed. AZT nucleotides were measured in samples from three patients receiving 250 mg ofAZT every 12 h. Intracellular concentrations of AZT-MP after 1-2 h ranged from 0.9 to 1.4 pmol/106 PBMC and then declined to 0.3-1.1 pmol/106 PBMC after 4 h. AZT-DP and AZT-TP reached concentrations of 0.3-0.5 pmol/106 PBMC after 1-2 h and could not be detected after 4 h in any of the three patients. Duplicate determinations deviated by <20

Predictive Value of Bronchoalveolar Lavage in Excluding a Diagnosis of Pneumocystis carinii Pneumonia During Prophylaxis with Aerosolized Pentamidine

We assessed the negative predictive value of bronchoalveolar lavage (BAL) for Pneumocystis carinii pneumonia (PCP) during prophylaxis with aerosolized pentamidine. On the basis of the assumption that undiagnosed and untreated PCP would progress and become clinically apparent, for 3 months we prospectively followed 34 consecutive cases in which BAL had not detected PCP. All patients were immunodeficient, had a symptomatic human immunodeficiency virus infection, and were evaluated for possible PCP during prophylaxis with aerosolized pentamidine. No transbronchial biopsies were performed. In 32 of 34 cases, a diagnosis of PCP could be excluded because of other definite diagnoses or improvement during the follow-up. Despite negative results of an examination of their BAL fluid, two patients received empirical treatment that was active against PCP; these patients were regarded as possibly having undiagnosed PCP. Thus, the negative predictive value of BAL alone was at least 94% (32 of 34 cases) in excluding a diagnosis of PCP during prophylaxis with aerosolized pentamidin

Human Immunodeficiency Virus Type 1 p24 Concentration Measured by Boosted ELISA of Heat-Denatured Plasma Correlates with Decline in CD4 Cells, Progression to AIDS, and Survival: Comparison with Viral RNA Measurement

Human immunodeficiency virus type 1 (HIV-1) RNA and p24 antigen concentrations were determined in plasma samples from 169 chronically infected patients (median CD4 cell count, 140 cells/μL; range, 0-1500 cells/μL). p24 quantification involved heat-mediated immune complex dissociation and tyramide signal amplification—boosted ELISA, which has a diagnostic sensitivity similar to that of RNA quantification by a commercial polymerase chain reaction kit. In Cox's proportional hazard models adjusted for CD4 cell count, both RNA (P < .005) and p24 (P = .043) levels were significant predictors of progression to AIDS. Measurement of p24 was superior to measurement of RNA in the model for survival (P = .032 vs. P = .19). p24 level was a significant predictor of CD4 cell decline in models adjusted for CD4 cell counts and was superior or equivalent to RNA level, depending on the group analyzed. Stratification by CD4 cell counts at baseline showed that the superiority of p24 measurement was more pronounced at lower levels of CD4 cells (<200/μL). p24 level may be of interest as a simple and inexpensive predictive marker of disease progressio