Sequence analysis of an HIV-1 isolate which displays unusually high-level AZT resistance in vitro.

Multiple mutations in the reverse transcriptase (RT) gene were observed in a drug-resistant isolate of human immunodeficiency virus type 1 (HIV1) from an individual having prolonged (greater than 2 years) zidovudine (AZT) therapy. The virus replicated in PBMC's in the presence of very high concentrations of AZT (125 microM). Drug-sensitive strains were curtailed by 0.01 microM AZT. Eleven defined mutations were observed as compared with published sequences of RT for eight strains of HIV1. Eight of these mutations were found in the domain involved in nucleotide recognition and enzyme function. Only one of the mutations, giving a Thr--Tyr change at amino acid 215, matched those previously ascribed (67, 70, 215, and 219) to the generation of high-level resistance to AZT. Therefore additional amino acid changes may have significance in the emergence of super-resistant viruses.

First-exposure adaptive resistance to aminoglycoside antibiotics in vivo with meaning for optimal clinical use.

The first exposure of gram-negative bacilli to an aminoglycoside antibiotic in vitro induces a biphasic bactericidal response and adaptive drug resistance (G. L. Daikos, G. G. Jackson, V. T. Lolans, and D. M. Livermore, J. Infect. Dis. 162:414-420, 1990; G. G. Jackson, G. L. Daikos, and V. T. Lolans, J. Infect. Dis. 162:408-413, 1990). The therapeutic implications were examined in netilmicin treatment of a Pseudomonas aeruginosa infection of normal and neutropenic mice. For 2 h after the first dose, the bactericidal rates were rapid, 0.75, 1.0, and 1.5 log10 CFU/h with doses of 10, 30, and 60 mg/kg, respectively. Each twofold increase in dosage reduced the number of surviving bacteria fivefold. Between 2 and 6 h, the second-phase bactericidal rate was slow, less than or equal to 0.3 log10 CFU/h, regardless of the dose. In a multiple-dose regimen, the same amount of netilmicin given in one dose was 70 and 90% more effective than two or three doses, respectively. Doses calculated to keep the drug level in plasma above the MIC were less effective than regimens giving first exposure to a high drug concentration. Adaptive resistance occurred when doses were given more than 2 h after the start of treatment. Temporary survival of bacteremic neutropenic mice was 60 to 70% greater with a second dose at 2 h than after a longer interval. In a thigh infection of neutropenic mice treated every 2 h, doses 4, 6, and 8 h after the first one showed no bactericidal effect. A drug-free interval of 8 h (20 times the drug half-life) renewed bacterial susceptibility to drug action. The results in vivo confirm the biphasic bactericidal action and induction of adaptive resistance that characterized first exposure of gram-negative bacilli to aminoglycoside antibiotics. The phenomena have meaning for the optimum clinical use of aminoglycosides.

The inductive role of ionic binding in the bactericidal and postexposure effects of aminoglycoside antibiotics with implications for dosing.

Gram-negative bacilli precooled to 4 degrees C to inactivate energy-dependent drug transport were exposed to an aminoglycoside antibiotic to assess the antibacterial effect of passive ionic binding of drug. Removal of free drug and energizing the cells by incubation at 37 degrees C showed the postexposure effect to be bactericidal. The effect was directly related to the amount and concentration of drug in the initial exposure medium proportional to the bacterial density. Binding was nonsaturable at the highest drug:bacteria ratio tested. Elution, exposure of spheroplasts, and inhibition by divalent cations indicated binding sites in the outer bacterial membrane. Different bacterial species had variable efficiency but similar patterns of binding different aminoglycosides reflecting in vitro susceptibility. The self-promoted postexposure internalization of ionically bound aminoglycoside accounts for the early drug-concentration-dependent rapid bactericidal action of aminoglycosides. The phenomenon has implications for effective initial dosing with aminoglycoside antibiotics.

Adaptive resistance to aminoglycoside antibiotics from first-exposure down-regulation.

Adaptive resistance to the bactericidal effect of an aminoglycoside antibiotic was induced in Pseudomonas aeruginosa and other aerobic gram-negative bacilli by initial exposure to the drug. Both subinhibitory and inhibitory concentrations produced resistance in bacterial cells surviving the effects of the initial ionic binding. Development of drug refractoriness required an adaptive period of growth, was enhanced by the continued presence of drug, and reversed after several hours of growth in drug-free medium. Unstable resistance was not explained by selection of mutants. The mechanism of adaptive resistance was down-regulation of aminoglycoside uptake during the period of accelerated energy dependent drug transport (EDP II). Down-regulation induced by gentamicin or tobramycin produced cross-resistance to other aminoglycosides. The kinetics of unstable first-exposure resistance suggests that a continuous drug level might not provide the most effective therapy with aminoglycosides and gives rationale to larger initial and longer interval bolus dosing.

Fungal and mycobacterial infections in patients infected with the human immunodeficiency virus.

Fungal and mycobacterial infections are among the most common opportunistic infections in patients infected with human immunodeficiency virus (HIV). Candida infections are the bell-wether of progression to symptomatic HIV infection and candida oesophagitis often marks the onset of the acquired immunodeficiency syndrome (AIDS). More than 80% of AIDS patients have candida disease. Candida infections remain local and respond to treatment but tend to recur. Cryptococcal infections initially affect few HIV positive patients but involve 10-30% with AIDS. Meningitis is the usual presentation and dissemination is common. Amphotericin usually produces improvement but cure is infrequent, and maintenance therapy is advisable. Mycobacteria cause intracellular infections increasing in parallel with immunodeficiency. Mycobacterium avium-intracellulare is predominant, occurring with other opportunistic pathogens causing systemic and local symptoms with high bacterial density in infected cells. Multidrug treatment is best, but the results are disappointing. Tuberculosis is prevalent in certain groups of patients. It often presents with atypical clinical and pathological features. Anti-tuberculous treatment is effective and prophylaxis should be considered. Endemic fungi with mycobacteria cause sporadic infections. Opportunistic infections are the lethal arm of HIV infection. Diligent diagnosis and persistent treatment offer benefit to HIV-infected patients.

Passive immunoneutralization of human immunodeficiency virus in patients with advanced AIDS.

Infusions of 55-500 ml plasma from one of two donors selected for high anti-p24 antibody titre and neutralising capacity were given to six patients with advanced AIDS. Human immunodeficiency virus (HIV) antigenaemia cleared immediately and the recipients' serum acquired the HIV antibody profile of the donor together with HIV neutralising activity. The passive antibody effects persisted for up to eleven weeks depending upon the volume of plasma given, which had a half-life of about 12 days. The infusions were followed by fewer symptoms, a transient increase in T lymphocytes, a reduction in the frequency of opportunistic infections, and a decline in the rate at which HIV could be cultured from plasma or lymphocytes.

Nasal-secretion leukocyte populations determined by flow cytometry during acute rhinovirus infection.

Leukocyte populations in the secretions of volunteers challenged by intranasal inoculation with rhinovirus serotype 25 were evaluated by means of flow cytometry. With the light-scatter properties of peripheral blood leukocytes as the standard of reference, significant increases (P less than .05) of both lymphocytes and phagocytes (polymorphonuclear leukocytes plus monocytes) were detected in the nasal secretions of persons infected by the viral challenge. There was a direct correlation of nasopharyngeal symptom severity with both the percentage of lymphocytes (P less than .05) and the percentage of phagocytes (P less than .001). Monoclonal antibodies for specific cell-membrane antigens identified the lymphocytes and phagocytes as leukocytes and also demonstrated the presence of a population of monocytic cells during the phase of maximal symptoms. The panel of monoclonals chosen did not unequivocally identify a lymphocyte population except in the presence of nosebleed. However, the results show that flow cytometry can be used to investigate nasal-secretion cell populations during the rhinovirus common cold.

Intravenous and intraocular ganciclovir for CMV retinitis in patients with AIDS or chemotherapeutic immunosuppression.

The efficacy and toxicity of ganciclovir given by intravenous or intravenous plus intravitreal injection were studied in nine patients with cytomegalovirus (CMV) retinitis; seven with AIDS and two with drug induced immunodeficiency. Five patients had retinitis with macular involvement in six sighted eyes; six patients had only peripheral retinitis in seven eyes. In two patients (two eyes) with macular involvement intravenous plus intravitreal injection of ganciclovir preserved sight; intravenous infusion alone did not in four eyes of three other patients. In seven eyes (six patients) with peripheral retinitis vision was retained regardless of the route of ganciclovir treatment. Following intravenous ganciclovir drug levels in the vitreous fluid were 1.4-2.2 mmol/l, that is, 44 and 65% of the concomitant serum concentration. Clinically and at necropsy three eyes showed no evidence of toxicity from intravitreal injection of ganciclovir. All of five patients with AIDS who received intravenous ganciclovir for more than one week developed leucopenia. CMV retinitis of the macula may be benefited with minimal drug toxicity by intravitreal injection of ganciclovir. Treatment of peripheral CMV retinitis in patients with AIDS may be optional.

Alterations in outer membrane proteins of Pseudomonas aeruginosa associated with selective resistance to quinolones.

Electrophoresis of outer membrane proteins in three ciprofloxacin-resistant strains of Pseudomonas aeruginosa isolated during therapy and their in vitro revertants indicated that diminution or loss of a 31- to 32-kilodalton outer membrane protein correlated with resistance in two of the three isolates. Resistance was unstable and caused no cross-resistance with other antibiotics.

Acute respiratory illness among immunized and nonimmunized patients with high-risk factors during a split season of influenza A and B.

A prospective survey of acute respiratory illness (RI) was made among 329 vaccinated and unvaccinated ambulatory patients with high-risk factors for influenza. Surveillance for virus during the influenza season revealed the predominance of influenza A and B in sequential periods. During the influenza A period, febrile RI was greatest among patients with chronic pulmonary disease; among 66 patients, vaccination significantly reduced RI. Age greater than 65 y (199 patients) and heart (90 patients) and metabolic diseases (151 patients) did not increase the relative frequency of febrile RI, and vaccine administration caused no apparent reduction in frequency of RI. During the influenza B period, no differences in RI were observed between the groups, and the frequency of RI was unrelated to vaccination. Variability in virus and vaccine specificities may have been important. Except for one subset of specific virus and host conditions, no overall reduction in influenza-like or total RI was observed from vaccinating ambulatory, high-risk patients.

Long-term oral ciprofloxacin: experience in the treatment of incurable infective endocarditis.

Acute septic infective endocarditis caused by Pseudomonas aeruginosa, in two patients with conditions that made it incurable, was treated with long-term orally administered ciprofloxacin. Bacteremia and symptoms cleared, resulting in subjective well-being without cure for three and one half and 22 months, respectively. Large amounts of ciprofloxacin, 150 and 1,440 g, respectively, were given continuously without apparent adverse reactions. Blood isolates of P. aeruginosa after treatment had limited progression of resistance to ciprofloxacin. Use of orally administered ciprofloxacin provides new opportunities for the long-term treatment of serious infections with restricted risk of bacterial drug resistance and no appreciable side effects.

Human immunodeficiency virus (HIV) antigenemia (p24) in the acquired immunodeficiency syndrome (AIDS) and the effect of treatment with zidovudine (AZT).

Infection with human immunodeficiency virus (HIV) may cause viral antigenemia, detected primarily as p24 viral core protein. Among 16 patients with the acquired immunodeficiency syndrome (AIDS) or AIDS-related complex studied serially, 12 had or developed antigenemia ranging from 16 to 3006 pg/mL in plasma. The level could be categorized as high (greater than 100 pg/mL) or low (15 to 65 pg/mL). Three patients with anti-p24 antibody had no antigenemia. Zidovudine (AZT), 200 or 250 mg every 4 hours, reduced antigenemia by about 90%; other regimens were less effective. Leukocyte cultures were positive for HIV from patients with antigenemia, and in one third of samples in the absence of antigenemia. High levels of antigenemia correlated with symptoms, CD4 cell count, and prognosis. Drug toxicity requiring a lower dose was followed by increased antigenemia, recurrent symptoms, and decreased CD4 cells, suggesting lymphocyte toxicity. Monitoring antigenemia can be useful in evaluating patients with HIV infection and in evaluating the effect of antiviral chemotherapy.

Oral ribavirin treatment of influenza A and B.

A loading dose and short-term administration of oral ribavirin significantly improved symptoms and signs of influenza type A or B infection in 25 patients. The antiviral effect was not significant. No adverse clinical effects or significant laboratory values were observed. Oral treatment of patients with influenza A or B infection might be possible with ribavirin.

Comparison of ciprofloxacin and beta-lactam antibiotics in the treatment of urinary tract infections and alteration of fecal flora.

Ciprofloxacin treatment of urinary tract infections in 23 patients (16 with and seven without urorenal abnormalities) was compared with beta-lactam antibiotic therapy given orally to 10 comparable patients. The alteration of aerobic gram-negative fecal flora was monitored. Ciprofloxacin eliminated bacteria from the urine of all patients; beta-lactam antibiotics failed in two of 10 patients. There were no relapses one week following ciprofloxacin treatment; six of nine patients experienced a relapse following beta-lactam treatment (p less than 0.01). By four to six weeks, all patients infected with gram-positive cocci had a relapse. Six of 14 patients with urorenal abnormalities in whom cures had been achieved acquired new infections. Before treatment, the bowel flora of 80 percent of the patients was resistant to amoxicillin, 20 percent was resistant to cefixime, and none was resistant to ciprofloxacin. Penicillin and cefixime increased the incidence of resistant flora to 93 and 36 percent, respectively. Ciprofloxacin suppressed aerobic bowel flora, and no resistant strains persisted after treatment. Ciprofloxacin promises effective short-term oral treatment of complicated urinary tract infections with minimal risk of drug-resistant recurrences.

Acute-phase decrease of T lymphocyte subsets in rhinovirus infection.

Populations of peripheral blood leukocytes were enumerated in 15 volunteers challenged by intranasal inoculation with rhinovirus serotype 25. The results demonstrated a significant decrease in total lymphocyte count among infected persons on the third day after challenge with the virus (P less than .01). The change in lymphocyte count was associated with a significant decrease in total T cells, as determined by monoclonal antibodies (both T11+ and T3+, P less than .02), but not in B cells (B7+). Among the subsets of T cells, T4+ (T helper/inducer) and T8+ (T suppressor/cytotoxic) lymphocytes both declined in number, but only the change in the T4+ subset was significant. For each of the lymphocyte populations that decreased significantly (T3+, T11+, and T4+) there was a strong correlation with increased severity of symptoms. Persons who had the greatest decrease in total lymphocyte count also shed virus most frequently. The number of nonlymphocyte leukocytes increased with the severity of the symptoms. These data show that T lymphocytes (particularly the T4+ population) are related to both the progression of infection and the symptoms of the rhinovirus common cold.

Prevention of herpesvirus infections in renal allograft recipients by low-dose oral acyclovir.

Forty patients with serum antibody against herpes simplex virus (HSV) were enrolled in a randomized, placebo-controlled, double-blind investigation of acyclovir given orally in a low dosage as prophylaxis against recurrent HSV infection after renal transplantation. During 30 postoperative days of medication, 14 of 21 placebo-treated and one of 19 acyclovir-treated patient(s) developed reactivation of HSV infection. Eleven of the former, but not the latter, had herpetic lesions. The protection against active infection with HSV during the period of prophylaxis with acyclovir is statistically highly significant. From 30 to 90 days after transplantation when no antiviral medicine was given, 60% (3/5) of the remaining placebo recipients and 44% (7/16) of the acyclovir patients developed active HSV infections. Herpetic lesions occurred in two of three and two of seven of infected people in the respective groups. No adverse effects of the drug were observed. The results show that HSV infections in immunosuppressed renal allograft recipients can be safely prevented, deferred, and ameliorated by an initial period of prophylaxis with a low dose of oral acyclovir.