Evaluation of FCE 22101 in experimental meningitis caused by Escherichia coli and Streptococcus pneumoniae

FCE 22101 is a new penem antibiotic with a spectrum of activity suggesting a possible role in the empirical treatment of meningitis. It appears to achieve a mean reduction in bacterial titre in CSF comparable with currently accepted agents for both pneumococcal and Escherichia coli meningitis. Its efficacy may, however, be variable. It does not achieve CSF level/MIC ratios as favourable as imipenem for the pathogens studied. Further studies are necessary to determine its role, if any, in this disease.

Cocaine use and HIV infection in intravenous drug users in San Francisco

We assessed risk factors for human immunodeficiency virus (HIV) infection in 633 heterosexual intravenous drug users. The HIV seroprevalence was 26% in blacks, 10% in Hispanics, and 6% in whites. Intravenous cocaine use significantly increased the risk of HIV infection, with a seroprevalence of 35% in daily cocaine users (odds ratio, 6.4; 95% confidence interval, 3.0 to 13.3). Black subjects were more likely to use cocaine regularly. Drug use in shooting galleries and sharing of drug injection equipment were also associated with HIV infection and were more common in cocaine users. By multivariate analysis, black race, daily cocaine injection by blacks and Hispanics, all other cocaine injection, heavy use prior to entry into methadone treatment by blacks, and use of drugs in shooting galleries were independent predictors of HIV infection. Methadone therapy was associated with substantial reductions in heroin use and some reduction in cocaine use, but 24% of cocaine users receiving methadone began or increased cocaine injection after entry into treatment.

Single, large, daily dosing versus intermittent dosing of tobramycin for treating experimental pseudomonas pneumonia

Single, large, daily aminoglycoside doses in animals are less toxic than conventional dosing, and higher drug concentrations in vitro produce more-rapid bacterial killing. Thus, we compared various aminoglycoside dosing schedules in neutropenic (n = 153) and nonneutropenic (n = 192) guinea pigs with Pseudomonas aeruginosa pneumonia. Equivalent tobramycin dosages were given: 5 mg/kg every 4 h or 30 mg/kg every 24 h. Animals were serially killed during therapy, and quantitative lung cultures were performed. Bacterial titers in lungs dropped rapidly in all tobramycin-treated animals, both neutropenic and nonneutropenic, during the initial 16 h of therapy. In nonneutropenic guinea pigs, lung titers remained constant despite continued 4-h dosing. With subsequent 24-h dosing, titers continued to drop, and by 72 h there were a significant number of animals with sterile lungs (P less than .01). In neutropenic guinea pigs given tobramycin every 24 h, bacterial regrowth occurred; thus, therapy was ineffective. Adding mezlocillin, however, suppressed regrowth; thus, combination therapy was superior (P less than .05).

Influence of granulocytes on brain edema, intracranial pressure, and cerebrospinal fluid concentrations of lactate and protein in experimental meningitis

Brain water content (brain edema), intracranial pressure, and cerebrospinal fluid (CSF) concentrations of lactate and protein increased significantly during 24 h of experimental meningitis due to Streptococcus pneumoniae, but changes were similar in normal and neutropenic rabbits. In sterile meningitis induced by N-formyl-methionyl-leucyl-phenyl-alanine (fMLP), low and high doses of fMLP were equally effective in inducing CSF pleocytosis, whereas only high doses of fMLP caused brain edema. High doses of fMLP injected intracisternally during pneumococcal meningitis also increased brain water content. The fMLP did not significantly increase intracranial pressure or CSF concentrations of lactate or protein in sterile or pneumococcal meningitis, nor did it cause brain edema in neutropenic animals. Thus, granulocytes may contribute to brain edema during meningitis if adequately stimulated, but intracranial pressure and CSF protein and lactate concentrations appear independent of granulocytes. Stimulation does not appear to occur early in meningitis, when granulocytes were without effect on brain edema.

Cholestasis and disseminated cytomegalovirus disease in patients with the acquired immunodeficiency syndrome

A cholestatic syndrome caused by papillary stenosis and sclerosing cholangitis (PS/SC) has been recently described as a complication of the acquired immunodeficiency syndrome (AIDS). Cytomegalovirus has been implicated as an etiologic factor in this syndrome. Consecutive cases of disseminated cytomegalovirus disease and viremia were reviewed for evidence of cholestasis. In 12 of 36 (33 percent) patients with cytomegalovirus infection (gastrointestinal disease [eight of 16 patients] or retinitis [four of 20 patients]), cholestatic liver enzyme abnormalities developed within three months of the diagnosis of cytomegalovirus disease. Radiologic imaging demonstrated biliary dilation in three of nine (33 percent) patients studied. Review of serial liver function tests showed no effect of ganciclovir therapy on the course of cholestatic abnormalities. AIDS patients without CMV end-organ disease were also reviewed for evidence of cholestasis. Six of 15 AIDS patients with positive blood culture results for cytomegalovirus had cholestatic liver enzyme abnormalities compared with four of 36 AIDS patients with negative viral blood culture results (p = 0.023, Fisher's exact test). Patients with cytomegalovirus retinitis, gastrointestinal disease, or viremia appear to be at increased risk for the development of cholestasis. In 3 to 11 percent of patients with cytomegalovirus retinitis or gastrointestinal disease, PS/SC may develop. This clinical association supports an etiologic role for cytomegalovirus in the PS/SC syndrome.

Use of animal models in evaluation of the quinolones

Discriminative animal models of infection are important in helping to define the role of new antibacterial drugs in the treatment of human diseases. Several animal models have been used to compare the efficacies of quinolones with those of standard therapies against selected bacterial pathogens. In animal models of endocarditis, pefloxacin, enoxacin, and ciprofloxacin have been shown to be equivalent to standard therapies against methicillin-sensitive Staphylococcus aureus and as effective as vancomycin against methicillin-resistant strains. Difloxacillin has been shown to be equivalent to vancomycin in a model of osteomyelitis due to S. aureus. Ciprofloxacin is as effective as the combination of ceftazidime and tobramycin in a model of pseudomonal meningitis, although the levels of ciprofloxacin (6 mg/L) in serum required to produce a bactericidal effect in the cerebrospinal fluid are higher than those usually obtained in humans. Ciprofloxacin and other quinolones are also effective therapy for pseudomonal infections in neutropenic animals with pneumonia, peritonitis, osteomyelitis, and endocarditis. Data obtained from these animal studies suggest that the quinolones may have an important role in the treatment of endocarditis, meningitis, osteomyelitis, and other serious infections in humans caused by S. aureus and Pseudomonas aeruginosa.

Antibiotic therapy, endotoxin concentration in cerebrospinal fluid, and brain edema in experimental Escherichia coli meningitis in rabbits

We investigated the effect of cefotaxime and chloramphenicol on endotoxin concentrations in cerebrospinal fluid (CSF) and on the development of brain edema in rabbits with Escherichia coli meningitis. Both antibiotics were similarly effective in reducing bacterial titers. Cefotaxime, but not chloramphenicol, induced a marked increase of endotoxin in CSF, from log10 1.5 +/- 0.8 to log10 2.8 +/- 0.7 ng/ml (P less than .01). This result was associated with an increase in brain water content (405 +/- 12 g of water/100 g of dry weight compared with 389 +/- 8 g in untreated controls; P less than .01), whereas in animals treated with chloramphenicol, brain water content was identical to controls. The cefotaxime-induced increase in endotoxin concentration and brain edema were both neutralized by polymyxin B, which binds to the lipid A moiety of endotoxin, or by a monoclonal antibody to lipid A. These results indicate that treating gram-negative bacillary meningitis with selected antibiotics induces increased endotoxin concentrations in CSF that are associated with brain edema.

Risk of transmitting the human immunodeficiency virus, cytomegalovirus, and hepatitis B virus to health care workers exposed to patients with AIDS and AIDS-related conditions

This prospective cohort study was designed to evaluate the risk of occupational transmission of human immunodeficiency virus (HIV), hepatitis B virus (HBV), and cytomegalovirus (CMV) to health care workers with intensive exposure to HIV-infected patients. Seventy-five percent of the 270 subjects had been exposed to patients with AIDS and AIDS-related conditions (ARC) for at least one year before enrollment, 18% worked in specialized AIDS units, and 35% sustained a total of 342 accidental parenteral exposures to HIV-infected body fluids. At the time of enrollment, none had antibody to HIV, and none of the 175 subjects retested 10 months later had acquired antibody. No evidence of increased risk of acquiring CMV or HBV was obtained. These results indicate that health care workers are at minimal risk for HIV, CMV, and HBV transmission from occupational exposure to patients with AIDS or ARC, even when intensively exposed for prolonged periods of time.

Efficacy of ciprofloxacin in animal models of infection: endocarditis, meningitis, and pneumonia

Animal models of infection are very useful tools for identifying those situations in which antibacterial drugs, including the quinolones, may play special roles, i.e., for positioning a drug correctly for its role in the treatment of human disease. Ciprofloxacin has been studied extensively in discriminative animal models of infection, and its efficacy in the treatment of these infections has been compared with that of standard therapy. In a rabbit model of staphylococcal endocarditis, ciprofloxacin was as effective as nafcillin alone, as well as nafcillin and gentamicin in combination, in treating rabbits with methicillin-susceptible Staphylococcus aureus endocarditis. Additionally, its activity was equal to that of vancomycin in reducing vegetation titers in rabbits with methicillin-resistant staphylococcal endocarditis. In a rabbit model of pseudomonal meningitis, ciprofloxacin was as effective as the combination of ceftazidime and tobramycin in lowering bacterial titers. However, in this model, serum levels of ciprofloxacin (6 micrograms/ml) necessary to achieve a bactericidal effect in the cerebrospinal fluid were slightly higher than levels targeted for humans. In a model of pseudomonal pneumonia in neutropenic guinea pigs, the efficacy of ciprofloxacin was compared with that of tobramycin and ceftazidime, both alone and in combination: ciprofloxacin was as effective in lowering bacterial counts as was the combination of ceftazidime plus tobramycin and its activity was superior to that of either drug alone. Thus, data from studies of ciprofloxacin in the treatment of endocarditis, meningitis, and pneumonia in animal models of infection suggest that this quinolone may play an important role in the therapy of these difficult-to-manage infections in humans.

Evaluation of combination chemotherapy in a lightly anesthetized animal model of Pseudomonas pneumonia

Gram-negative bacillary pneumonia is a major cause of morbidity and mortality in hospitalized patients. The use of synergistic combinations of aminoglycosides and beta-lactams for therapy of this infection has been recommended but remains controversial. We designed a new model of Pseudomonas pneumonia in a lightly sedated guinea pig by using a long-acting anesthetic to impair natural respiratory defenses. We used this model to compare the efficacy of ceftazidime and tobramycin alone and in combination in the therapy of Pseudomonas pneumonia. The two antibiotics were shown to be synergistic in vitro for the strain of Pseudomonas aeruginosa tested. Treated animals receiving both antibiotics had fewer viable bacteria remaining in lung tissues (P less than 0.05) and exhibited a trend towards improved survival in comparison to animals receiving a single drug. In this model of Pseudomonas pneumonia, in vitro synergy was reflected by increased efficacy in vivo.

Ciprofloxacin in experimental Pseudomonas aeruginosa meningitis in rabbits

The potential of ciprofloxacin for the therapy of Pseudomonas aeruginosa meningitis was evaluated in an animal model by determining the penetration of the drug into CSF, its concentration-dependent killing characteristics in vivo, and its relative efficacy compared with ceftazidime and tobramycin. Meningitis was produced in 40 rabbits by intracisternal injection of 3 X 10(7) organisms. The drugs were administered intravenously over seven hours, and simultaneously serum and CSF samples were taken at 0, 1, 3, 5, and 7 h for determination of drug concentration and CSF bacterial counts. The percentage penetration of ciprofloxacin (18.4 +/- 12.3; mean +/- standard deviation) in infected rabbits was substantially increased over that found in uninfected rabbits (4.1 +/- 1.3). The rate of bacterial killing for animals treated with ceftazidime (100 mg/kg/h) and high doses of tobramycin (2.5 mg/kg/h) was -0.51 +/- 0.13 (log10 cfu/ml/h). This was similar to the rate of killing (-0.48 +/- 0.2) found when ciprofloxacin was infused at 5 mg/kg/h, a dose that produced a mean serum level of 6.7 +/- 4.6 mg/l, which corresponds to concentrations achievable in humans. As dosages were increased (15 and 30 mg/kg/h), the rate of bacterial killing also increased (-0.70 +/- 0.1 and -0.89 +/- 0.4 respectively; r = 0.7407; P less than 0.01). The drugs shows promise in the treatment of pseudomonas meningitis.

Efficacy of ciprofloxacin for experimental endocarditis caused by methicillin-susceptible or -resistant strains of Staphylococcus aureus

The efficacy of ciprofloxacin for experimental aortic valve endocarditis in rabbits infected by either a methicillin-susceptible or a methicillin-resistant strain of Staphylococcus aureus was compared with standard therapy of nafcillin or vancomycin, respectively. After 4 days of therapy, ciprofloxacin reduced the counts of organisms in aortic valve vegetations as effectively as the standard regimen for both susceptible and resistant strains. Mean concentrations of ciprofloxacin in serum achieved 1 h after a dose exceeded the MBC for each strain by twofold or less. In these experiments ciprofloxacin was as efficacious as standard regimens currently used to treat staphylococcal infections in humans.

Limitations of animal models in predicting beta-lactam efficacy for endocarditis and meningitis

Animal models are important in predicting the efficacy in humans of antimicrobial agents for various disease conditions, including endocarditis and meningitis. Screening models are useful in assessing antibiotic effectiveness and toxicity; their advantages include simplicity, a reproducible course of infection, a well-defined therapeutic end point, and low cost. However, the inoculum size, the virulence of the organism, and the production of beta-lactamases can have important effects on outcome and must be considered in the interpretation of data obtained from such models. Discriminative models are those designed to mimic human disease as closely as possible with respect to infectious inoculum, host response, and course of disease. Each drug's pharmacokinetics must be carefully documented before being extrapolated to humans. Rigid criteria must be established to minimize misinterpretation of results from animal studies before conclusions from in vivo animal models are applied to human disease.

Challenging conventional aminoglycoside dosing regimens. The value of experimental models

Although newer antimicrobials look promising for the treatment of serious gram-negative infections, aminoglycosides still remain part of the mainstay of their therapy. Traditional intermittent therapy is based upon the premise that high serum aminoglycoside concentrations are toxic. However, the rate of bacterial killing for aminoglycosides is also a concentration-dependent phenomenon. Two animal models of Pseudomonas pneumonia were utilized to examine the efficacy of non-traditional aminoglycoside dosing regimens, i.e., single, high daily doses versus the conventional, intermittent low doses of aminoglycosides. Other recent data suggest that toxicity might also be less with the large, single daily dose regimen. The current dosing strategy used for aminoglycosides may not be maximizing their therapeutic potential, nor minimizing their toxicities.

Clinical aspects of adult epiglottitis

Epiglottitis in adults has been considered a medical rarity. Recent evidence suggests that this disorder is seen in adults regularly, though uncommonly, in clinical practice. We present 14 cases of adult epiglottitis. Most cases were blood culture-negative; Hemophilus influenzae was isolated from blood cultures in two cases and Hemophilus parainfluenzae in one case. There were no deaths. Epiglottitis in adults differs from pediatric epiglottitis in the mode of presentation, bacterial cause and clinical course.

Influence of body temperature on bacterial growth rates in experimental pneumococcal meningitis in rabbits

We examined the role of fever as a host defense in experimental pneumococcal meningitis in rabbits. Twelve hours after intracisternal inoculation of an encapsulated type 3 Streptococcus pneumoniae strain, body temperature was manipulated by using two different anesthetic drugs: pentobarbital, which did not affect temperature, and urethane, which mitigated the febrile response to infection. Growth rates of pneumococci in cerebrospinal fluid were dramatically influenced by modification of the febrile response. Rabbits whose fever was not suppressed had mean bacterial doubling times of 2.76 +/- 1.43 h. Animals with a blunted febrile response had a significantly faster mean bacterial growth rate (doubling time = 1.10 +/- 0.27 h; P less than 0.02). When the antipyretic effect of urethane was counteracted by raising the ambient temperature, animals also showed a marked reduction in pneumococcal growth rates. In vitro, the pneumococci grew well at 37 degrees C in Trypticase soy broth (doubling time = 0.61 +/- 0.05 h) and in pooled rabbit cerebrospinal fluid (doubling time = 0.85 +/- 0.07 h). However, at 41 degrees C neither medium supported growth. Thus, body temperature appears to be a critical determinant of pneumococcal growth rates in experimental meningitis, and fever could be a host defense in this disease.

Serum bactericidal activity of rifampin in combination with other antimicrobial agents against Staphylococcus aureus

Because rifampin-resistant strains of Staphylococcus aureus emerge during monotherapy with this drug, a search was made for potentially useful companion drugs. Bactericidal titers of spiked serum were determined, and time kill studies were performed for 10 strains of methicillin-susceptible S. aureus. We tested rifampin in combination with nafcillin, vancomycin, clindamycin, pefloxacin, ciprofloxacin, trimethoprim, teicoplanin, or erythromycin. The bactericidal activity of nafcillin, vancomycin, and teicoplanin was significantly reduced (P less than 0.05) when rifampin was added to the drug regimen. In contrast, the addition of rifampin to clindamycin or erythromycin significantly increased bactericidal activity as measured by both bactericidal titers in serum and 6-h killing rates (P less than 0.02). Bactericidal activity in serum was also increased by the addition of rifampin to trimethoprim, but rifampin-resistant strains emerged with this combination.

Evaluation of pefloxacin in experimental Escherichia coli meningitis

The therapeutic efficacy of the fluoroquinolone pefloxacin mesylate was compared with those of cefotaxime and chloramphenicol in a rabbit model of Escherichia coli meningitis. The mean percent penetration (+/- the standard deviation) of pefloxacin (range, 1 to 30 mg/kg per h) into cerebrospinal fluid of infected rabbits was 51.3 +/- 14.0 compared with 11.1 +/- 1.0 for cefotaxime (100 mg/kg per h) and 22.3 +/- 1.5 for chloramphenicol (60 mg/kg per h). The rate of bacterial killing (delta log10 CFU/ml per h) did not change over a dosage range of 1 to 15 mg/kg per h (-0.37 +/- 0.15, 20% sterile). At 30 mg/kg per h, the rate achieved (-0.77 +/- 0.18, 100% sterile) was comparable to that of cefotaxime (-0.88 +/- 0.23, 100% sterile) and superior to that of chloramphenicol (-0.10 +/- 0.14, 0% sterile).