Randall A. Prince

Antifungal Activity of Amphotericin B, Fluconazole, and Voriconazole in an In Vitro Model of Candida Catheter-Related Bloodstream Infection

ABSTRACT The activity of five simulated antifungal regimens for eradication of catheter-related bloodstream Candida infection was evaluated with an in vitro pharmacodynamic model. Single-lumen central venous catheters were colonized with Candida species by sequentially incubating central venous catheters in plasma and then in growth medium (RPMI plus morpholinepropanesulfonic acid) containing a standardized suspension (105 CFU/ml) of Candida albicans, Candida glabrata, or slime-producing Candida parapsilosis. Colonized central venous catheters were then placed in a one-compartment pharmacodynamic model where five antifungal regimens (plus control) were simulated: amphotericin B, 1.0 mg/kg every 24 h; amphotericin B, 0.5 mg/kg every 24 h; fluconazole, 400 mg every 24 h; fluconazole, 800 mg every 24 h; and voriconazole, 4 mg/kg every 12 h. During exposure to the simulated clinical regimens, samples were serially removed from the model over 48 h for quantitation of viable organisms. All antifungal regimens suppressed fungal counts by both peripheral and catheter sampling versus control (P = 0.001). Overall, antifungal activity ranked amphotericin B (1 mg/kg) > amphotericin B (0.5 mg/kg) ≥ voriconazole > fluconazole (800 mg) ≥ fluconazole (400 mg). No regimen, however, completely eradicated (by culture and electron microscopy) central venous catheter colonization. Regrowth was noted in the model during therapy against C. glabrata and C. parapsilosis but was not associated with an increase in the MICs for the isolates. Lack of in vitro antifungal activity against biofilm-encased organisms appeared to be the primary reason for mycological failure of antifungal regimens in the model.

Itraconazole Preexposure Attenuates the Efficacy of Subsequent Amphotericin B Therapy in a Murine Model of Acute Invasive Pulmonary Aspergillosis

ABSTRACT Antagonism has been described in vitro and in vivo for azole-polyene combinations against Aspergillus species. Using an established murine model of invasive pulmonary aspergillosis, we evaluated the efficacy of several amphotericin B (AMB) dosages given alone or following preexposure to itraconazole (ITC). Mice were immunosuppressed with cortisone acetate and cyclophosphamide. During immunosuppression, animals were administered either ITC solution (50 mg/kg of body weight) or saline by oral gavage twice daily for 3 days prior to infection. Infection was induced by intranasally inoculating mice with a standardized conidial suspension (1 × 108 CFU/ml) of Aspergillus fumigatus strain AF 293. AMB was then administered by daily intraperitoneal injections (0.25, 0.5, 1.0, and 3.0 mg/kg) starting 24 h after inoculation and continuing for a total of 72 h. Drug pharmacokinetics of AMB and ITC in plasma were determined by high-performance liquid chromatography. Four different endpoints were used to examine the efficacy of antifungal therapy: (i) viable counts from harvested lung tissue (in CFU per milliliter), (ii) the whole-lung chitin assay, (iii) mortality at 96 h, and (iv) histopathology of representative lung sections. At AMB doses of >0.5 mg/kg/day, fewer ITC-preexposed mice versus non-ITC-preexposed mice were alive at 96 h (0 to 20 versus 60%, respectively). At all time points, the fungal lung burden was consistently and significantly higher in animals preexposed to ITC, as measured by the CFU counts (P = 0.001) and the chitin assay (P = 0.03). Higher doses of AMB did not overcome this antagonism. ITC preexposure was associated with poorer mycological efficacy and survival in mice treated subsequently with AMB for invasive pulmonary aspergillosis.

Itraconazole-amphotericin B antagonism in Aspergillus fumigatus: an E-test-based strategy.

ABSTRACT We examined an E-test-based strategy for testing the combination of itraconazole and amphotericin B, the latter given either sequentially or concomitantly, in isolates of Aspergillus fumigatus. An antagonistic interaction between the two drugs was noted, especially with the sequential administration of amphotericin B. This in vitro antagonism was reversible.

Voriconazole pre-exposure selects for breakthrough mucormycosis in a mixed model of Aspergillus fumigatus-Rhizopus oryzae pulmonary infection.

Mucormycosis is an uncommon fungal infection that has been increasingly reported in severely immunocompromised patients receiving Aspergillus-active antifungals. Although clinical studies and pre-clinical animal models have suggested a unique predisposition for breakthrough mucormycoses in patients receiving voriconazole, no study has specifically evaluated the selection dynamics of various Aspergillus –active antifungal classes in vivo. We utilized an Aspergillus fumigatus:Rhizopus oryzae (10:1) model of mixed fungal pneumonia in corticosteroid-immunosuppressed mice to compare the selection dynamics of daily liposomal-amphotericin B (L-AMB), micafungin (MCFG) and voriconazole (VRC) therapy. A. fumigatus and R. oryzae lung fungal burden were serially monitored in parallel using non-cross-amplifying quantitative real-time PCR assays for each fungal genus. Additionally, experiments were performed where the R. oryzae component of the mixed inoculum was serially-passed on VRC-containing agar before animal infection. We found prior exposure to voriconazole in vitro, consistently resulted in a 1.5–2 log10 increase in R. oryzae fungal burden by day +5 in vivo relative to animals infected with the non-VRC preexposed inoculum, irrespective of the antifungal-treatment administered in mice (P ≤ 0.02 all treatment groups). Mice infected with the VRC-preexposed inoculum and subsequently treated with saline or VRC had the highest mortality rates (82–86%), followed by MCFG (55%) then L-AMB (39%, P = 0.04 vs. control). However, in vivo treatment alone with voriconazole alone did not consistently increase the virulence of non- voriconazole preexposed R. oryzae versus controls. We conclude that exposure of R. oryzae sporangiospores to voriconazole in vitro modulates the subsequent growth rate and/or virulence of the fungus in vivo, which reduces effectiveness of Mucorales-active antifungals. The mechanisms underlying this phenotypic change are unknown.

Antimicrobial Penetration into Cerebrospinal Fluid

The complex physiology of the blood-brain barrier and the characteristics of an antimicrobial which govern its distribution into the brain are poorly understood. Likewise, available data regarding CSF antimicrobial concentrations after extra-CNS administration, as tabulated in this review, are inadequate. Because of the potentially dire consequences that result from inappropriately treated CNS infections, large cooperative studies using standardized methodology are needed. Suggestions for such methods are outlined.

Clinical Trial of Topical Erythromycin in Inflammatory Acne

Sixty-nine informed subjects participated in a split-face, double-blind trial of topical erythromycin base 2% in Vehicle/N® versus Vehicle/N® alone. All subjects had grades II or III acne as described by Pillsbury. Study solutions were assigned to a randomly selected side of the subjects face. Solutions were applied twice daily. Inflammatory lesion counts were performed by the same investigator during the eight weeks of study at biweekly intervals. The difference in inflammatory lesion counts from beginning to end of study for each side of the face was compared utilizing Students paired t-test There was not a statistically significant difference in mean inflammatory lesions at the end of eight weeks (D̅ = 1.46, t = 1.36, df 68). There was, however, a significant difference at two and six weeks (D̅ = 2.59, t = 3.72, df 68; D̅ = 1.41, t = 2.03, df 68). Observed differences in lesion counts were not considered to be clinically significant.

Side-Effect Profiles of Newer-Generation Cephalosporins

FOR MANY YEARS, cephalosporins as a class have been considered safe compounds for clinical use, with the possible exception of cephaloridine. Aside from hypersensitivity phenomena, cephalosporins produced only uncommon instances of clinically significant adverse effects. Comparatively speaking, with regard to adverseeffect profiles, a cephalosporin is a cephalosporin is a cephalosporin. For the most part, side-effect differentiation was attempted on the basis of the incidence of phlebitis with intravenous administration and the degree of pain encountered with intramuscular administration. Cephalothin apparently was responsible for a significantly greater degree of phlebitis and pain when administered intramuscularly than were other competitive cephalosporins, such as cephapirin and cephradine. However, this seemingly significant difference in side effects has become a mute point since the reformulation of cephalothin several years ago. Until recently, there was little difference in toxicity among the available cephalosporins. However, the advent of the newergeneration cephalosporins (i.e., cefotaxime, moxalactam, and cefoperazone) clearly has demonstrated that these cephalosporins differ significantly in side effect profiles, such that therapeutic decisions regarding their use must include consideration of the differences in adverse effects. That is not to say that the differences in clinical adverse effects are the sole consideration in selecting a cephalosporin, but that prior to the introduction of the newer-generation cephalosporins, little regard to comparable side effects was necessary in the cephalosporin-selection process. Of the newer cephalosporins, specifically cefotaxime, moxalactam, and cefoperazone, the latter two agents have demonstrated adverse-effect profiles that distinguish them from cefotaxime. Although each of the newer cephalosporins has been associated with superinfection, there is no documentation demonstrating significant differences in superinfection potential or occurrence. Considerable noncomparative work and clinical impressions suggest that the overall prevalence of superinfection ranges between 1 and 10 percent for each of these agents. Since moxalactarus release for clinical use in the U.S., adverse effects of ever-increasing frequency and

Bacterial Meningitis: Despite advances in specific antimicrobial therapy and rehabilitative measures, bacterial meningitis remains one of most serious of infectious diseases

BACTERIAL MENINGITIS Important Information about Bacterial Meningitis Pursuant to SB 1107 enacted by the State of Texas and SB 62 thereafter, all new students enrolling in the Health Science Center must provide proof that the meningitis vaccination was administered at least 10 days prior to the first day of the term. Vaccinations must have been received or renewed within the last 5 years. The legislation provides two exceptions:

Effect of a Dual-Lumen Peripheral Catheter on the Delivery of Known Incompatible Medications

OBJECTIVE: To determine the degree to which a dual-lumen peripheral catheter prevented precipitation of solutions known to be incompatible due to pH during simultaneous infusion in an in vitro model. METHODS: An in vitro model was devised to simulate peripheral venous blood flow from an antecubital source to systemic circulation. Ondansetron was simultaneously infused with fluorouracil, aminophylline, sodium bicarbonate, and ampicillin sodium in concentrations reflective of clinical conditions into the Twin Cath 20/22 (the dual-lumen catheter used in this experiment). Study solutions were primed with the prepared drug solution and administered for 15 minutes. Phase I used Normosol-R as the diluent to gather preliminary data; phase II used human plasma. All samples were obtained immediately before the start of the infusion and at 5, 10, and 15 minutes during the infusion, and 5 minutes after the infusion. Samples were visually inspected at each time point for precipitation and analyzed in duplicate by the appropriate stability-indicating HPLC method (except for sodium bicarbonate). Compatibility was defined as no visual evidence of precipitation and no more than 15% mean change in final versus initial concentration. RESULTS: Phase I experiments showed immediate precipitation in Normosol-R within the venous flow. However, in phase II, because of the buffering capacity that plasma proteins add to plasma, no precipitation occurred. All the drug combinations used in this study have been reported to be incompatible at the concentrations tested; however, we detected no incompatibilities. CONCLUSIONS: The results of this study indicate that using a dual-lumen peripheral catheter, such as the Twin Cath, may allow solutions incompatible due to pH to be administered simultaneously.