Evaluation of the clinical usefulness of C. difficile toxin testing in hospitalized patients with diarrhea.

Although numerous studies have evaluated the sensitivity and specificity of different assays for Clostridium difficile toxin, none has evaluated how physicians utilize these tests or respond to test results. Therefore, we assessed patient characteristics, clinical findings, and physician responses to positive and negative assay results at two university-affiliated hospitals, one of which used a cell cytotoxicity assay to test for C. difficile toxin and the other of which used an enzyme immunoassay. Two hundred one patient samples at Hospital A and 199 samples at Hospital B were assessed. Positive toxin assays were more frequent at Hospital A than at Hospital B (p < 0.001), at least in part due to the fact that patients tested at Hospital A were more likely to have fever (p < 0.001), an abnormal abdominal exam (p < 0.001), an abnormal leukocyte count (p < 0.001), and a history of prior antibiotic use (p < 0.001). Empiric therapy for C. difficile before results of the toxin assay was more common (p < 0.001) at Hospital A (83/201, 41. 3%) than at Hospital B (25/199, 12.5%). Once empiric therapy was started, most physicians continued therapy despite negative test results (Hospital A, 76%; Hospital B, 69%). Patients who were treated empirically were more likely than patients not treated empirically to have positive toxin assay results and to have fever (p < 0.001), an abnormal abdominal exam (p = 0.003), or an abnormal leukocyte count (p < 0.05). Physicians seldom ordered repeat toxin assays (Hospital A, 14%; Hospital B, 10%) if the initial assay result was negative. In logistic regression analysis, predictors of a positive toxin assay were prior antibiotic therapy, an abnormal abdominal exam, residence at Hospital A, and age >/= 60 years. Predictors of empiric therapy were residence at Hospital A and prior antibiotic therapy. Because physicians electing to empirically treat inpatients with diarrhea rarely alter therapy based on C. difficile toxin assay results, a more cost-effective management strategy may be not to obtain a toxin assay at all in such situations. Testing should be limited to patients who have received antibiotics within the prior month and who have significant diarrhea and/or abdominal pain.

Immunochemical specificity of human antibodies to lipopolysaccharide from the J5 rough mutant of Escherichia coli O111:B4.

Antibody to the core region of lipopolysaccharide (LPS) of Escherichia coli O111:B4 (J5) is reported to cross-react with LPS from other gram-negative bacteria. We used an enzyme-linked immunosorbent assay to test various LPSs and their constituents for their ability to inhibit binding of human IgG antibody to J5 LPS to J5 LPS. Results were expressed as the concentration of inhibitor required to cause 50% inhibition of binding (I50). I50 values of antibody to J5 LPS for J5 LPS ranged from 5 x 10(-7) M to 8 x 10(-9) M. I50 values for Salmonella minnesota (Rc) were higher (2 x 10(-4) M to 2 x 10(-7) M). Other rough LPS failed to inhibit to 50% (up to 2 x 10(-4) M). J5 lipid A and core oligosaccharide inhibited, with I50 values ranging from 2 x 10(-5) M to 3 x 10(-8) M. Fifty percent inhibition was not achieved by smooth LPS (8 x 10(-5) M), heterologous lipid A (3 x 10(-4) M), or core LPS constituents (5 x 10(-3) M). These data suggest that IgG J5 LPS antibodies are specific for the Rc chemotype of the core of LPS.

Clinical comparison of an agar slide blood culture bottle with tryptic soy broth and a conventional blood culture bottle with supplemented peptone broth.

The Roche Septi-Chek biphasic blood culture system with tryptic soy broth was compared with a conventional blood culture bottle with supplemented peptone broth in 6,956 paired blood cultures from adult patients. Both systems were inoculated with equal volumes of blood (5 ml) and incubated aerobically (vented) for 2 weeks. More clinically important bacteria and fungi, including Staphylococcus aureus, S. epidermidis, Escherichia coli and other Enterobacteriaceae, Pseudomonas aeruginosa, and Candida albicans and C. tropicalis were recovered from the biphasic system (P less than 0.001). In contrast, more clinically important anaerobic bacteria (P less than 0.001) and Gardnerella vaginalis (P less than 0.05) were recovered in conventional supplemented peptone broth. Staphylococci (P less than 0.01), Enterobacteriaceae other than E. coli (P less than 0.05), and fungi (P less than 0.001) were detected 1 or more days earlier in the biphasic system, whereas streptococci (P less than 0.001) were detected earlier in the conventional bottle. The overall superiority of the agar slide blood culture system compared with conventional blood culture bottles was confirmed by this evaluation. For optimal detection of anaerobic bacteremia, however, the agar slide bottle should be paired with an anaerobic bottle.

Controlled evaluation of Trypticase soy broth in agar slide and conventional blood culture systems.

A commercially available biphasic blood culture system that utilizes an attachable agar slide paddle and Trypticase soy broth (BBL Microbiology Systems, Cockeysville, Md.) was compared with a conventional Trypticase soy broth blood culture bottle in 6,867 paired blood cultures from adult patients. Both systems were inoculated with equal volumes of blood (5 ml) and incubated aerobically (vented) for 2 weeks. More clinically important bacteria and fungi, including Staphylococcus epidermidis, streptococci, Escherichia coli, Klebsiella spp., other Enterobacteriaceae, and Pseudomonas aeruginosa, were recovered from the biphasic system (P less than 0.001). In contrast, more anaerobic bacteria of importance were recovered in the conventional bottle (P less than 0.01). Staphylococci (P less than 0.001), gram-negative facultative and aerobic bacteria (P less than 0.001), and fungi (P less than 0.001) were detected 1 or more days earlier in the biphasic system, whereas pneumococci (P less than 0.05) were detected earlier in the conventional bottle. Of 603 clinically important microorganisms that grew in the biphasic system, 601 (99.7%) were detected by day 7 of incubation, but only 403 of 490 microorganisms (82.2%) were detected by day 7 in the conventional bottle. Overall, the biphasic system was superior to the conventional bottle. For optimal detection of anaerobic bacteremia, however, the biphasic system should be used in conjunction with a complementary anaerobic conventional bottle.

Multicenter collaborative evaluation of a standardized serum bactericidal test as a prognostic indicator in infective endocarditis.

One hundred twenty-nine patients with bacterial endocarditis were evaluated in a multicenter collaborative study to determine whether a standardized serum bactericidal test could predict the outcome of the infection. All centers used a microdilution test method that defined all known test variables, including inoculum size, culture medium, dilution technique, incubation time, method of subculture, and bactericidal endpoint. Peak serum bactericidal titers of 1:64 or more and trough serum bactericidal titers of 1:32 or more predicted bacteriologic cure in all patients. The traditionally recommended serum bactericidal titer of 1:8 had statistically significant predictive accuracy at trough antibiotic levels only. The serum bactericidal test was a poor predictor of bacteriologic failure and ultimate clinical outcome, which depends on many factors. Wider recognition by physicians and clinical microbiologists that this in vitro test of antimicrobial activity can accurately predict bacteriologic success but cannot accurately predict either bacteriologic failure or clinical outcome could lead to a better consensus about its appropriate use. On the basis of the results of this study, peak serum bactericidal titers of 1:64 or more and trough serum bactericidal titers of 1:32 or more are recommended to provide optimal medical therapy for infective endocarditis.

Salmonella mediastinitis--a rare disease.

A case report is presented of a young man who was seen because of pleuritic chest pain and fever. CT cross sectional imaging defined a mediastinal mass. Diagnosis of acute mediastinitis due to Salmonella java was made from culturing material at mediastonotomy.

Antibiotic bonding to polytetrafluoroethylene with tridodecylmethylammonium chloride.

Polytetrafluoroethylene (PTFE) treated with the cationic surfactant, triodecylmethylammonium chloride (TDMAC), binds 14C-penicillin (1.5 to 2 mg antibiotic/cm graft), whereas untreated PTFE or PTFE treated with anionic detergents shows little binding of antibiotic. TDMAC-treated PTFE concomitantly binds penicillin and heparin, generating a surface that potentially can resist both infection and thrombosis. The retention of these biologically active molecules is not due to passive entrapment in the PTFE but reflects an ionic interaction between the anionic ligands and surface-bound TDMAC. Penicillin bound to PTFE is not removed by exhaustive washing in aqueous buffers but is slowly released in the presence of plasma or when the PTFE is placed in a muscle pouch in the rat. Muscle tissue adjacent to the treated PTFE shows elevated levels of antibiotic following implantation. PTFE treated with TDMAC and placed in a muscle pouch binds 14C-penicillin when it is locally irrigated with antibiotic or when penicillin is administered intravenously. Thus, the TDMAC surface treated either in vitro or in vivo with penicillin provides an effective in situ source for the timed release of antibiotic.

Levamisole in chronic pyoderma.

Eleven patients, 8 females and 3 males, aged 17-53 years with chronic recurrent pyoderma (mean duration of 8.4 years) unresponsive to a variety of therapeutic modalities, were treated with oral levamisole 1 . 5-2 . 5 mg/kg/day (100-200 mg daily) for 2 consecutive days every week. Five out of eleven patients (3 males and 2 females) demonstrated one or more host defense abnormalities including impaired polymorphonuclear (PMN) chemotaxis, impaired bactericidal activity against Staphylococcus aureus, decreased in vitro lymphocyte response to Phytohaemagglutinin (PHA) and low serum IgM and IgA. Seven of eleven patients showed clinical improvement following levamisole administration for 4-11 months. Two showed complete clearance of skin lesions while on levamisole and for a year thereafter; three showed marked clearance of lesions during levamisole therapy but recurred with mild disease 6 months after termination of levamisole therapy; and two showed improvement of lesions during therapy but recurred immediately after levamisole discontinuation. Levamisole treatment was also associated with complete in vitro correction of PMN bactericidal abnormality, improvement of PMN chemotactic abnormality and augmentation of in vitro lymphocyte response to PHA. Correlation between in vitro potentiation of host defense mechanisms and clinical response was noted. Significant probable side-effects necessitating discontinuation of therapy included transient elevation of liver enzymes in 2 patients and extensive hemorrhagic skin rash in one.

Simplified assay for gentamicin in the presence of other antibiotics.

Gentamicin concentration was estimated by using a clinical isolate of a multiple antibiotic-resistant strain of Staphylococcus epidermidis in an agar well diffusion assay. The presence of clinically attainable concentrations of cephalothin, ampicillin, carbenicillin, clindamycin, or chloramphenicol did not affect the assay.