Multicenter laboratory evaluation of the bioMérieux Vitek antimicrobial susceptibility testing system with 11 antimicrobial agents versus members of the family Enterobacteriaceae and Pseudomonas aeruginosa.

A four-center study in which a total of 1,082 recent clinical isolates of members of the family Enterobacteriaceae and Pseudomonas aeruginosa were examined versus 11 antimicrobial agents with the bioMérieux Vitek susceptibility test system (Hazelwood, Mo.) and the GNS-F6 card was conducted. In addition, a challenge set consisting of the same 200 organisms was examined in each of the four participating laboratories. Results obtained with the Vitek system were compared to MICs determined by a standardized broth microdilution method. For purposes of comparison, susceptibility categories (susceptible, intermediate, or resistant) were assigned on the basis of the results of both methods. The result of the broth microdilution test was considered definitive. The total category error rate with the Vitek system and the recent clinical isolates (11,902 organism-antimicrobial comparisons) was 4.5%, i.e., 1.7% very major errors, 0.9% major errors, and 1.9% minor errors. The total category error rate calculated from tests performed with the challenge set (i.e., 8,800 organism-antimicrobial comparisons) was 5.9%, i.e., 2.2% very major errors, 1.1% major errors, and 2.6% minor errors. Very major error rates higher than the totals were noted with Enterobacter cloacae versus ampicillin-sulbactam, aztreonam, ticarcillin, and ticarcillin-clavulanate and with P. aeruginosa versus mezlocillin, ticarcillin, and ticarcillin-clavulanate. Major error rates higher than the averages were observed with Proteus mirabilis versus imipenem and with Klebsiella pneumoniae versus ofloxacin. Excellent overall interlaboratory reproducibility was observed with the Vitek system. The importance of inoculum size as a primary determinant in the accuracy of susceptibility test results with the Vitek system was clearly demonstrated in this study. Specifically, when an inoculum density fourfold higher than that recommended by the manufacturer was used, high rates of false resistance results were obtained with cell wall-active antimicrobial agents versus both the Enterobacteriaceae and P. aeruginosa.

Relapsing, bacteremic Klebsiella pneumoniae meningitis in an AIDS patient.

The acquired immunodeficiency syndrome (AIDS) is manifested by severe immunologic (predominantly T-lymphocyte) abnormalities and opportunistic infections. Central nervous system (CNS) infections are frequent. Pathogens causing CNS infections in AIDS patients include parasites, fungi, and viruses and are similar to those reported in other states of impaired cell mediated immunity (CMI). A case of relapsing, bacteremic Klebsiella pneumoniae meningitis in an AIDS patient is presented.

Growth inhibition of Candida albicans by human polymorphonuclear neutrophils: activation by interferon-gamma and tumor necrosis factor.

This study was designed to determine whether anti-fungal activity in human polymorphonuclear neutrophils (PMN) might be under the regulation of cytokines such as tumor necrosis factor (TNF) and interferon-gamma (IFN-gamma). By using a radiolabel microassay developed in our laboratory that makes use of the incorporation of [3H]glucose into residual candida, we demonstrated that PMN were better able to inhibit Candida albicans growth in vitro than peripheral blood lymphocytes (PBL). PMN from normal volunteers added to C. albicans for 24 hr at 37 degrees C in a 96-well microplate inhibited fungal growth almost completely at the 300:1 effector/target ratio and frequently at 100:1. Significant activity was still detected at 10:1. In contrast, PBL from the same donors had less activity than PMN at all the ratios tested and lost all function at the 30:1 ratio. TNF and IFN-gamma added to the PMN/candida cultures additionally enhanced PMN to inhibit candida growth. Both cytokines effectively activated PMN down to 0.1 to 0.01 U/ml, and neither cytokine interfered directly with fungal growth, even up to 1000 U/ml. Concentrations of TNF and IFN-gamma below the level that enhanced PMN function when added together to PMN acted synergistically to significantly enhance their anti-fungal activity. Therefore, TNF and IFN-gamma which are active on lymphoid cells, also appear to have the ability to directly activate PMN, and the synergistic action of the two cytokines at low doses that may be below the toxic range may prove to be of clinical importance in protection of immunocompromised host against opportunistic infections.

A rapid [3H]glucose incorporation assay for determination of lymphoid cell-mediated inhibition of Candida albicans growth.

[3H]glucose uptake by Candida albicans after interaction with lymphoid effector cells was used to provide a quick, accurate and objective assessment of the growth inhibitory potential of lymphoid cells on candida. After 18 h coincubation of effector cells with candida, [3H]glucose was added for 3 h and the amount of radiolabel incorporated into residual candida was measured. The results showed that [3H]glucose uptake was proportional to the number of candida organisms left in the microwell and is dose dependent on the effector/target (E/T) ratio. At an E/T ratio of 300/1, complete inhibition of candida was seen, with significant inhibition still present at 30/1. In addition, monocytes and polymorphonuclear cells were found to be the primary cells responsible for eliminating candida.

Pulmonary mucormycosis as a complication of chronic salicylate poisoning.

Mucormycosis is an often-fatal opportunistic fungal infection caused by members of the class Zygomycetes (Phycomycetes), order Mucorales. Most cases are diagnosed by histologic examination, through the identification of mucormycotic hyphae in infected tissues. Chronic debilitating conditions accompanied by acidosis such as diabetes mellitus, as well as leukemia, lymphoma, and immunodeficient states, predispose to the development of this type of opportunistic infection. This report describes a hitherto undescribed finding, the presence of structures consistent with sporangia in tissue sections, in a case of pulmonary mucormycosis occurring in a nondiabetic patient with metabolic acidosis secondary to chronic salicylate poisoning.

Increased sensitivity of a new coagglutination test for rapid identification of Haemophilus influenzae type b.

A newly developed rapid coagglutination test for identifying Haemophilus influenzae type b organisms isolated from clinical specimens correlated 100% with the slide agglutination test but was 100- to 200-fold more sensitive.

Evaluation of povidone-iodine as vesical irrigant for treatment and prevention of urinary tract infections.

This is a preliminary study evaluating diluted solutions of povidone-iodine (PVP-I) as urinary bladder irrigants for the treatment and prevention of urinary tract infection. Diluted povidone-iodine solutions were used as indwelling catheter irrigants and as instillations into the urinary bladder following intermittent catheterization. The diluted PVP-I solutions had no efficacy in either the treatment or prevention of urinary tract infections when used as indwelling urethral or suprapubic catheter irrigants. There was a suggestion of a slight decrease in the incidence of urinary tract infections during the use of PVP-I in the intermittent catheterization group in this uncontrolled study, but the percentage of positive urine cultures was greater than desired. The absence of any unfavorable data has led us to conclude that the diluted PVP-I caused no undesirable side effects in any of the patients treated with this agent, PVP-I bladder irrigation warrants further investigation in special cases such as lower urinary tract fungal infections.

Characteristics of cells present in peritoneal fluids of mice injected intraperitoneally with Bordetella pertussis.

Peritoneal fluids obtained from mice after the intraperitoneal administration of Bordetella pertussis vaccine, heated vaccine, an extract of the organisms, killed Escherichia coli, or thioglycolate medium were examined in terms of total cells and percentage that adhered to glass cover slips during 2-h incubation period. All these substances were found to increase the number of leukocytes in peritoneal fluid within 1 to 2 days after the injection. This increase appeared to be due to an influx of macrophages and polymorphonuclear leukocytes with relative proportions at a given time dependent upon the material involved in the induction of the response. The initial increases after pertussis vaccine seemed to be due mainly to an influx of monomuclear cells, whereas with E. coli neutrophils constituted the major portion of the cell population. The percentage of peritoneal cells that attached to glass was also found to be markedly reduced in preparations obtained from mice after the injection of B. pertussis or E. coli. There appeared to be differences in persistence of this phenomenon, with preparations containing the histamine-sensitizing factor being the most active in affecting adherence properties. Thus these data would suggest that the action of B. pertussis on macrophages (or precursors) and neutrophils is not expressed in terms of suppression of emigration properties, as has been reported by others for lymphocytes, but is manifested in the alteration of glass-adherence characteristics. Within experimental limitations, it is believed that macrophages are possibly more involved in terms of altered function than are the polymorphonuclear cells.