Search for primary infection by Pneumocystis carinii in a cohort of normal, healthy infants.

To determine whether Pneumocystis carinii is associated with clinical illness in the competent host, 107 normal, healthy infants were enrolled in a 2-year prospective cohort study in Chile. P. carinii was identified by specific stains and nested--deoxyribonucleic acid (DNA) amplification of the large subunit mitochondrial ribosomal ribonucleic acid gene of P. carinii f. sp. hominis, and seroconversion was assessed by enzyme-linked immunosorbent assay of serum samples drawn every 2 months. P. carinii DNA was identified in nasopharyngeal aspirates obtained during episodes of mild respiratory infection in 24 (32%) of 74 infants from whom specimens were available for testing. Three (12.5%) of those 24 infants versus 0 of 50 infants who tested negative for P. carinii had apnea episodes. Seroconversion developed in 67 (85%) of 79 infants who remained in the study by 20 months of age and occurred in the absence of any symptoms of disease in 14 (20.8%). The study indicates that P. carinii DNA can be frequently detected in healthy infants, and it raises the hypothesis that they may be an infectious reservoir of P. carinii in the community. Further investigation is needed to identify whether P. carinii causes overt respiratory disease in infants.

Oral cefixime is similar to continued intravenous antibiotics in the empirical treatment of febrile neutropenic children with cancer.

Empiric oral antibiotic therapy for febrile neutropenic cancer patients has been suggested as a means to decrease hospitalization, but the safety of this approach has not been adequately studied in children. We compared continued iv antibiotic therapy with switching treatment to orally administered cefixime in a group of selected febrile neutropenic children for whom blood cultures were sterile after 48 h of incubation. Two hundred episodes of febrile neutropenia were studied (156 patients), and 100 episodes were randomized to receive each treatment. Failure to respond to therapy was defined by documented or suspected bacterial infection, recurrent fever, or discontinuation of assigned therapy for any reason before neutropenia resolved. Rates of treatment failure were similar in the oral cefixime group (28%) and in the iv antibiotic group (27%; P=1.0). Results support the safety of oral cefixime therapy for low-risk febrile neutropenic children, a therapeutic approach that would facilitate earlier outpatient management and decrease the costs of treatment.

A rat model for combined Trypanosoma cruzi and Pneumocystis carinii infection.

Dexamethasone treated rats inoculated with Trypanosoma cruzi developed acute parasitemia. In addition, these animals concomitantly developed severe Pneumocystis carinii pneumonia (PCP) and died after 4 weeks of immunosuppression (100%). However, immunocompetent (untreated) rats inoculated with T. cruzi did not acquire P. carinii and recovered from T. cruzi infection. Rats immunosuppressed, but not inoculated with T. cruzi, developed only PCP and died 5-6 weeks later (93%). In contrast, immunocompetent or immunocompromised IRC mice infected with T. cruzi all died of acute parasitemia in only 8-12 days with no detectable PCP infection. In conclusion, rats immunosuppressed and T. cruzi inoculated can serve as a MOPPS model for a single drug evaluation. In addition, T. cruzi infection independently does not provoke P. carinii pneumonia in this model. Finally, patients with Chagas' disease treated with corticosteroids may be at risk for PCP and should be considered for chemoprophylaxis.

Effect of CD40 ligand and other immunomodulators on Pneumocystis carinii infection in rat model.

The corticosteroid-treated animal is well established as an experimental model for the study of Pneumocystis carinii pneumonitis (PCP). Latent or acquired infection with P. carinii in the murine lung progresses to fatal pneumonitis when the host is profoundly immunocompromized. In this study the effects of five immunomodulators; recombinant CD40 ligand (CD40L), bryostatin 1, recombinant FLT3 ligand (FLT3L), recombinant granulocyte colony-stimulating factor (G-CSF) and recombinant interleukin-15 (IL-15) were investigated against PCP in a dexamethasone immunosuppressed Sprague-Dawley rat model. The majority of rats (70%) treated with CD40L at the onset of dexamethasone immunosuppression were protected against PCP. When CD40L was given after 10 days of immunosuppression, only 40% of the rats resolved the infection. However, 95% of the control animals developed PCP. Immunosuppressed rats treated with bryostatin 1, an immune activator had a partial (50%) protection against P. carinii infection. In contrast, daily administration of FLT3L, IL-15 or G-CSF provided no protection against P. carinii infection.

Search for Pneumocystis carinii DNA in upper and lower respiratory tract of humans.

Recent studies suggest that Pneumocystis carinii DNA may be detected by PCR in oropharyngeal secretions in the majority of patients with P. carinii pneumonitis (PCP). However, the prevalence of P. carinii DNA in patients without PCP has not been well established. A prospective study of 258 nasal, pharyngeal, and salivary specimens from 86 individuals with AIDS, cancer or no underlying disease, and without respiratory infection, found no P. carinii DNA in any of the samples. Separately, to validate the PCR for detection of P. carinii DNA, 45 specimens from the lower respiratory tract (bronchoalveolar lavage [BAL] and sputum) from 31 patients with pneumonitis and AIDS or cancer were studied. Eleven had PCP by conventional stains and 20 did not. All patients with PCP, and none without PCP, had P. carinii DNA in BAL, sputum or both. The study indicates the prevalence of P. carinii DNA is low or absent in oropharyngeal secretions in the absence of PCP.

Transmission of Pneumocystis carinii DNA from a patient with P. carinii pneumonia to immunocompetent contact health care workers.

The transmission of Pneumocystis carinii from person to person was studied by detecting P. carinii-specific DNA in prospectively obtained noninvasive deep-nasal-swab samples from a child with a documented P. carinii pneumonia (PCP), his mother, two contact health care workers, and 30 hospital staff members who did not enter the patient's room (controls). Nested-DNA amplification was done by using oligonucleotide primers designed for the gene encoding the mitochondrial large subunit rRNA of rat P. carinii (P. carinii f. sp. carinii) that amplifies all forms of P. carinii and internal primers specific for human P. carinii (f. sp. hominis). P. carinii f. sp. hominis DNA was detected in samples from the patient and all of his contacts versus none of the 30 hospital staff members. The results, as previously shown in murine models of P. carinii pneumonia, document that person-to-person transmission of P. carinii is possible. This observation suggests that immunocompromised patients not on PCP prophylaxis should not enter the room of a patient with PCP, and it also raises the question as to whether healthy contacts can transmit the disease to immunocompromised patients at risk.

Single-dose pharmacokinetics and safety of the oral antiviral compound adefovir dipivoxil in children infected with human immunodeficiency virus type 1. The Pediatrics AIDS Clinical Trials Group.

The acyclic phosphonate analog adefovir is a potent inhibitor of retroviruses, including human immunodeficiency virus (HIV) type 1, and, unlike some antiviral nucleosides, does not require the initial phosphorylation step for its activity. Two oral dosages of the adefovir prodrug adefovir dipivoxil were evaluated in a phase I study with children with HIV infection. A total of 14 patients were stratified into age groups ranging from 6 months to 18 years of age. Eight patients received 1.5 mg of adefovir dipivoxil per kg of body weight, and six patients received 3.0 mg of adefovir dipivoxil per kg. Serum samples were obtained at intervals during the 8 h postdosing and were analyzed for adefovir concentrations. Patients were monitored for adverse effects. All samples collected resulted in quantifiable levels of adefovir (lower limit of quantitation, 25 ng/ml) from each patient. The areas under the concentration-versus-time curves (AUCs) were similar (P = 0.85) for the 1.5- and 3.0-mg/kg doses, while the apparent oral clearance (CL/F) was significantly higher (P = 0.05) for the 3-mg/kg dose. Pharmacokinetic parameters differed by patient age. In comparing those children older and younger than the median age of 5.1 years, AUC (P = 0.03), maximum concentration of drug in serum (P = 0.004), and the concentration at 8 h postdosing (P = 0.02) were significantly lower for the younger children. There were no significant differences for apparent volume of distribution and CL/F normalized to body surface area, but there was a suggestive difference in half-life (P = 0.07) among the subjects in the older and younger age groups. No significant adverse events were encountered. These data provide the basis for a multidose phase II study of adefovir dipivoxil in HIV-infected infants and children.

Association of primary Pneumocystis carinii infection and sudden infant death syndrome.

To delineate clinical and histological features of the first Pneumocystis carinii infection affecting the immunocompetent host, P. carinii-specific histological stains were performed on autopsy lung specimens from 534 consecutive pediatric patients (those with AIDS and malignancies were excluded) in Santiago, Chile. P. carinii clusters were found in 4 (25%) of 16 infants who died of no apparent cause at arrival to the emergency department, and in 10 (2.9%) of 342 infants who died of multiple conditions at the hospital (P=.002, Fisher's exact test). This prompted us to analyze additional series of infants with sudden infant death syndrome (SIDS). In 161 additional SIDS cases, 47 (35.1%) of 134 infants from Chile and 4 (14.8%) of 27 infants from Oxford, United Kingdom, were found to have P. carinii clusters in the lungs. The quantity of P. carinii cysts was small compared with the numbers seen in immunocompromised hosts with P. carinii pneumonitis. This study provides histological evidence that primary P. carinii infection is associated with SIDS.

Aspergillosis in children with cancer: A 34-year experience.

A retrospective review of medical records, microbiology and pathology laboratory records, and nosocomial infection surveillance data was undertaken to describe the experience with culture-documented aspergillus infection in pediatric cancer patients at our facility. Sixty-six patients were identified from a 34-year period. The most common underlying diagnosis was leukemia. Risk factors included neutropenia, immunosuppression, and prior antibiotic therapy. On the basis of clinical presentation, 23 patients were believed to have disseminated disease and 43 to have localized disease. The lung was the most frequently affected organ. Despite aggressive medical and surgical management, overall mortality was 85% within the first year after diagnosis. Patients who presented with disease in sites other than the lungs fared better than patients with initial pulmonary involvement (P=.0014). Aspergillosis continues to be associated with poor outcome. Development of improved medical and adjuvant therapies, including surgery, is warranted.

DNA amplification of nasopharyngeal aspirates in rats: a procedure to detect Pneumocystis carinii.

The diagnosis of Pneumocystis carinii pneumonia (PCP) requires invasive methods of bronchoalveolar lavage and lung biopsy. In this study, we examined efficacy of polymerase chain reaction (PCR) compared to Giemsa and silver ammoniacal staining to detect P. carinii in easily accessible extrapulmonary sites as well as lung. Samples were collected from lung, nasal and pharyngeal aspirates, gastric contents, urine and blood from dexamethasone treated or untreated virus-free Sprague-Dawley rats. All immunosuppressed lung samples were P. carinii positive by PCR analysis and both stains. Respectively DNA fragments of P. carinii were found in 93%, of nasal and 75% of pharyngeal aspirates, and 0% of sera, urine or gastric aspirates from immunosuppressed rats. However, no P. carinii cysts or trophozoites were found in nasal and pharyngeal aspirates (extrapulmonary sites) by silver ammoniacal or Giemsa staining. In comparison, none of the specimens from immunocompetent rats were PCR positive at any sites tested including the lungs. Therefore, PCR amplification products of nasal and pharyngeal aspirates showed that immunosuppressed rats with PCP can carry P. carinii DNA fragments in their upper respiratory tracts, but immunocompetent animals without PCP, are free of the organism and this suggests an approach to be investigated in humans with PCP.

Pharmacokinetics of azithromycin administered alone and with atovaquone in human immunodeficiency virus-infected children. The ACTG 254 Team.

To evaluate if atovaquone (ATQ) interacts pharmacokinetically with azithromycin (AZ) in human immunodeficiency virus-infected children, 10 subjects (ages, 4 to 13 years) were randomized in a crossover study to receive AZ (5 mg/kg/day) alone (ALONE) or AZ (5 mg/kg/day) and ATQ (30 mg/kg/day) simultaneously (SIM) prior to receiving AZ and ATQ staggered by 12 h. Despite a lack of significant difference in the mean AZ pharmacokinetic parameters, the steady-state values of AZ's area under the concentration-time curve from 0 to 24 h and maximum concentration in serum were consistently lower (n = 7 of 7) for the SIM regimen than they were for the ALONE regimen. A larger study will be required to determine if ATQ affects AZ pharmacokinetics and efficacy in a clinically significant manner.

Use of dapsone in the prevention and treatment of Pneumocystis carinii pneumonia: a review.

Dapsone, with or without trimethoprim or pyrimethamine, has strong anti-Pneumocystis carinii activity, as demonstrated by in vitro methods, animal studies, and clinical trials. The drug blocks folic acid synthesis of P. carinii by inhibition of dihydropteroate synthetase activity. Dapsone is efficiently absorbed (70%-80%) from the gastrointestinal tract, reaches peak serum concentration in 2-6 hours, and is adequately distributed to the fluid of the alveolar spaces. Synergistic effects against P. carinii are noted when trimethoprim is combined with dapsone. This combination is recommended for therapeutic use for P. carinii pneumonia (PCP) as an alternative for patients who cannot take trimethoprim-sulfamethoxazole (TMP-SMZ). Evidence from more than 40 studies of dapsone as prophylaxis for PCP in AIDS patients shows that dapsone, either alone or in combination with pyrimethamine, is as effective as aerosolized pentamidine or atovaquone but slightly less effective than TMP-SMZ. Adverse effects include rash, anemia, methemoglobinemia, agranulocytosis, and hepatic dysfunction. Desensitization can be accomplished with many cases. Dapsone is the most cost-effective prophylaxis currently available for PCP.

Effects of aerosolized synthetic surfactant, atovaquone, and the combination of these on murine Pneumocystis carinii pneumonia.

An immunosuppressed rat model was used to determine the pharmacokinetics of aerosolized atovaquone (administered with and without a synthetic surfactant) and to evaluate the efficacy of inhaled atovaquone in the prevention and treatment of Pneumocystis carinii pneumonia (PCP). After a single dose by aerosol, mean peak concentrations of atovaquone averaged 52 microg/mL in plasma and 31 microg/g in lungs of rats infected with P. carinii. When atovaquone was combined with surfactant, mean peak concentrations of 94 microg/mL in plasma and 51 microg/g in lung were achieved. Aerosolized synthetic surfactant alone significantly increased survival of rats with PCP and, when combined with atovaquone, increased plasma and lung concentrations of the drug and eradication of the organism.

Current issues in the epidemiology, transmission, and reactivation of Pneumocystis carinii.

Issues related to the epidemiology, transmission, and reactivation of Pneumocystis carinii remain controversial. In this article, current studies related to geographic variations in the prevalence of P. carinii pneumonia are reviewed. In addition, extensive investigations show that exposure to P. carinii occurs early in life, followed by seemingly complete clearance of the organisms. Recent molecular techniques show that P. carinii pneumonia during periods of immune suppression can occur either by reactivation or by acquisition of new organisms. These studies are analyzed and a composite model of P. carinii infection is proposed.