Effect of hydration status on cerebral blood flow and cerebrospinal fluid lactic acidosis in rabbits with experimental meningitis

The effects of hydration status on cerebral blood flow (CBF) and development of cerebrospinal fluid (CSF) lactic acidosis were evaluated in rabbits with experimental pneumococcal meningitis. As loss of cerebrovascular autoregulation has been previously demonstrated in this model, we reasoned that compromise of intravascular volume might severely affect cerebral perfusion. Furthermore, as acute exacerbation of the inflammatory response in the subarachnoid space has been observed after antibiotic therapy, animals were studied not only while meningitis evolved, but also 4-6 h after treatment with antibiotics to determine whether there would also be an effect on CBF. To produce different levels of hydration, animals were given either 50 ml/kg per 24 h of normal saline ("low fluid") or 150 ml/kg 24 h ("high fluid"). After 16 h of infection, rabbits that were given the lower fluid regimen had lower mean arterial blood pressure (MABP), lower CBF, and higher CSF lactate compared with animals that received the higher fluid regimen. In the first 4-6 h after antibiotic administration, low fluid rabbits had a significant decrease in MABP and CBF compared with, and a significantly greater increase in CSF lactate concentration than, high fluid rabbits. This study suggests that intravascular volume status may be a critical variable in determining CBF and therefore the degree of cerebral ischemia in meningitis.

Natural history of disseminated Mycobacterium avium complex infection in AIDS

This study sought to better characterize the natural history of AIDS-associated disseminated Mycobacterium avium complex (MAC) infection. Towards that end two retrospective studies were done: a case-control survival study and a MAC respiratory colonization study. Among 137 consecutive patients who had a sterile body site cultured for mycobacteria within 3 months of their first AIDS-defining episode of Pneumocystis carinii pneumonia, median survival was significantly shorter in those with disseminated MAC infection (107 days; 95% confidence interval [CI] 55-179) than those with negative cultures (275 days; 95% CI 230-318; P less than .01), even after controlling for age, absolute lymphocyte count, and hemoglobin concentration. Among 34 patients with AIDS and respiratory MAC colonization, 22 later developed disseminated infection (65% predictive value for subsequent MAC dissemination). Disseminated MAC infection was associated with significantly shorter survival for patients with AIDS, and the presence of MAC in respiratory specimens has substantial predictive value for subsequent disseminated infection.

Effect of indomethacin on the pathophysiology of experimental meningitis in rabbits

The effects of indomethacin on central nervous system abnormalities in rabbits with experimental pneumococcal meningitis were studied. As expected, prostaglandin E2 levels in cerebrospinal fluid were significantly lower in the indomethacin-treated group, indicating that the drug effectively reduced prostaglandin synthesis. Brain edema was markedly attenuated in the indomethacin-treated group; however, cerebrospinal fluid white blood cell counts, lactate and protein concentrations, and intracisternal pressure were not significantly different between groups. It seems that indomethacin, while effective in reducing brain edema, does not significantly affect other important pathophysiologic alterations in experimental pneumococcal meningitis.

Treatment of tuberculosis in patients with advanced human immunodeficiency virus infection

BACKGROUND AND METHODS

Infection with the human immunodeficiency virus (HIV) increases the risk of tuberculosis and may interfere with the effectiveness of antituberculosis chemotherapy. To examine the outcomes in patients with both diagnoses, we conducted a retrospective study of all 132 patients listed in both the acquired immunodeficiency syndrome (AIDS) and tuberculosis case registries in San Francisco from 1981 through 1988.

RESULTS

At the time of the diagnosis of tuberculosis, 78 patients (59 percent) did not yet have a diagnosis of AIDS, 18 patients (14 percent) were given a concomitant diagnosis of AIDS (as determined by the presence of an AIDS-defining disease other than tuberculosis), and the remaining 36 patients (27 percent) already had AIDS. The manifestations of tuberculosis were entirely pulmonary in 50 patients (38 percent), entirely extrapulmonary in 40 patients (30 percent), and both pulmonary and extrapulmonary in 42 patients (32 percent). The treatment regimens were as follows: isoniazid and rifampin supplemented by ethambutol for the first two months, 52 patients; isoniazid and rifampin supplemented by pyrazinamide and ethambutol for the first two months, 39 patients; isoniazid and rifampin, 13 patients; isoniazid and rifampin supplemented by pyrazinamide for the first two months, 4 patients; and other drug regimens, 17 patients. The intended duration of treatment for patients whose regimen included pyrazinamide was six months, and for patients who did not receive pyrazinamide, nine months. Seven patients received no treatment because tuberculosis was first diagnosed after death. Sputum samples became clear of acid-fast organisms after a median of 10 weeks of therapy. Abnormalities on all chest radiographs taken after three months of treatment were stable or improved except for those of patients who had new nontuberculous infections. The only treatment failure occurred in a man infected with multiple drug-resistant organisms who did not comply with therapy. Adverse drug reactions occurred in 23 patients (18 percent). For all 125 treated patients, median survival was 16 months from the diagnosis of tuberculosis. Tuberculosis was a major contributor to death in 5 of the 7 untreated patients and 8 of the 125 treated patients. Three of 58 patients who completed therapy had a relapse (5 percent); compliance was poor in all 3.

CONCLUSIONS

Tuberculosis causes substantial mortality in patients with advanced HIV infection. In patients who comply with the regimen, conventional therapy results in rapid sterilization of sputum, radiographic improvement, and low rates of relapse.

General principles of therapy of pyogenic meningitis

In bacterial meningitis, several pharmacodynamic factors determine therapeutic success-when defined as sterilization of the CSF: (1) Local host defense deficits in the CNS require the use of bactericidal antibiotics to sterilize the CSF. (2) CSF antibiotic concentrations that are at least 10-fold above the MBC are necessary for maximal bactericidal activity. Protein binding, low pH, and slow bacterial growth rates are among the factors that may explain the high antibiotic concentrations necessary in vivo. (3) High CSF peak concentrations that lead to rapid bacterial killing appear more important than prolonged suprainhibitory concentrations, probably because very low residual levels in the CSF prevent bacterial regrowth, even during relatively long dosing intervals. (4) Penetration of antibiotics into the CSF is significantly impaired by the blood-brain barrier and thus, very high serum levels are necessary to achieve the CSF concentrations required for optimal bactericidal activity. Beyond these principles, recent data suggests that rapid lytic killing of bacteria in the CSF may have harmful effects on the brain because of the release of biologically active products from the lysed bacteria. Since rapid CSF sterilization remains a key therapeutic goal, the harmful consequences of bacterial lysis present a major challenge in the therapy of bacterial meningitis. Currently, dexamethasone represents that only clinically beneficial approach to reduce the harmful effects of bacterial lysis, and novel approaches are required to improve the outcome of this serious infection.

The role of human immunodeficiency virus infection in pneumococcal bacteremia in San Francisco residents

Human immunodeficiency virus (HIV) is an important risk factor for invasive pneumococcal disease, but information on clinical course and infecting serotypes is limited. To help develop strategies to reduce the morbidity due to invasive pneumococcal disease, episodes of pneumococcal bacteremia were identified by retrospective review of microbiology records (November 1983-November 1987) at 10 San Francisco hospitals and, for patients 20-55 years old living in San Francisco, HIV antibody status was determined by review of medical records. Pneumococcal isolates from one hospital were serotyped. Of 294 patients with pneumococcal bacteremia identified, 32 (11%) had AIDS at the time pneumococcal bacteremia was diagnosed and another 43 (15%) were HIV-infected but did not have AIDS; 12 HIV-infected patients developed AIDS after the episode of pneumococcal bacteremia. The rate of pneumococcal bacteremia in AIDS patients was estimated to be 9.4/1000 patient-years. Serotypes of 27 (82%) of 33 pneumococcal isolates from HIV-infected patients and 107 (90%) from 119 patients without known HIV infection were among the 23 serotypes included in the currently available polysaccharide vaccine. The rate of pneumococcal bacteremia is approximately 100-fold greater in AIDS patients in San Francisco than rates reported before the AIDS epidemic, but more than half the episodes of pneumococcal bacteremia in HIV-infected patients occurred in patients without AIDS. Data on pneumococcal serotypes causing invasive disease in HIV-infected patients suggest that the current pneumococcal vaccine, if effective in this population, could provide significant protection against pneumococcal disease.

Cryptococcal meningitis in the acquired immunodeficiency syndrome

Cryptococcosis is the most common, deep-seated fungal infection in AIDS patients, and cryptococcal meningitis is the most frequently observed syndrome. AIDS patients with cryptococcal meningitis usually have an indolent presentation and nonspecific findings on physical examination. Routine laboratory tests are of little assistance in diagnosing cryptococcal meningitis. Cerebrospinal fluid (CSF) white blood cell counts tend to be low, and glucose and protein levels are nonspecific. Serum cryptococcal antigen (CRAG) is a sensitive test for cryptococcal meningitis, and CSF CRAG is usually also positive. Definitive diagnosis is made by culture of the CSF. Therapy of cryptococcal meningitis is changing to antifungal agents that are easy to administer as outpatient therapy. Amphotericin B continues to be the primary antifungal used in initial treatment of cryptococcal meningitis; addition of flucytosine is of no benefit. Recent data suggest oral fluconazole is effective as primary therapy, and may be superior to amphotericin B as maintenance therapy. Maintenance therapy decreases the incidence of relapse and increases survival.

The pharmacokinetics of teicoplanin in varying degrees of renal function

The pharmacokinetics of teicoplanin, a new glycopeptide antibiotic with activity against aerobic gram-positive bacteria, were characterized after intravenous administration of a single 3 mg/kg dose in five healthy volunteers and six patients with various degrees of stable renal insufficiency. Serum and urine samples were collected during a 15-day period and drug concentrations were assayed microbiologically. The mean elimination half-life of teicoplanin was 162.6 +/- 69.8 hours in healthy volunteers and was prolonged with decreased renal function. The mean plasma and renal clearances of teicoplanin in healthy subjects were 11.4 +/- 1.5 ml/min and 10.0 +/- 1.0 ml/min, respectively. Both values decreased in patients with renal failure and correlated significantly with measured creatinine clearances (r2 = 0.938 and 0.884, respectively). A nomogram for dosage adjustment in patients with varying degrees of renal failure is presented.

Loss of cerebrovascular autoregulation in experimental meningitis in rabbits

The present study was designed to determine whether cerebrovascular autoregulation is intact in experimental meningitis and to examine the relationship between fluctuations in cerebral blood flow (CBF) and increased intracranial pressure (ICP). Measurements of CBF were determined by the radionuclide microsphere technique in rabbits with experimental Streptococcus pneumoniae meningitis with simultaneous ICP monitoring via an implanted epidural catheter. CBF and ICP measurements were determined at baseline and when mean arterial blood pressure (MABP) was artificially manipulated by either pharmacologic or mechanical means. CBF was pressure passive with MABP through a range of 30-120 torr, and ICP directly correlated with CBF. These findings indicate that autoregulation of the cerebral circulation is lost during bacterial meningitis, resulting in a critical dependency of cerebral perfusion on systemic blood pressure, and that the parallel changes in ICP and in CBF suggest that fluctuations in CBF may influence intracranial hypertension in this disease.

Treatment of right-sided Staphylococcus aureus endocarditis in intravenous drug users with ciprofloxacin and rifampicin

A combination of ciprofloxacin (intravenous then oral) and oral rifampicin was tested in 14 intravenous drug users with right-sided Staphylococcus aureus endocarditis. All 10 patients who completed therapy were cured based on resolution of symptoms and negative blood cultures at 4 weeks post therapy.

Infections with Cryptococcus neoformans in the acquired immunodeficiency syndrome

We reviewed the records of 106 patients with cryptococcal infections and the acquired immunodeficiency syndrome (AIDS) treated at San Francisco General Hospital. We examined four issues: the efficacy of treatment with amphotericin plus flucytosine as compared with amphotericin alone, the efficacy of suppressive therapy, the prognostic clinical characteristics, and the course of nonmeningeal cryptococcosis. In 48 of the 106 patients (45 percent), cryptococcosis was the first manifestation of AIDS. Among the 89 patients with cryptococcal meningitis confirmed by culture, survival did not differ significantly between those treated with amphotericin plus flucytosine (n = 49) and those treated with amphotericin alone (n = 40). Flucytosine had to be discontinued in over half the patients because of cytopenia. Long-term suppressive therapy with either ketoconazole or amphotericin was associated with improved survival, as compared with survival in the absence of suppressive therapy (median survival, greater than or equal to 238 vs. 141 days; P less than 0.004). The only clinical features independently associated with a shorter cumulative survival were hyponatremia and a positive culture for cryptococcus from an extrameningeal source. The 14 patients with nonmeningeal cryptococcosis had a median survival (187 days) and rate of relapse (20 percent) similar to those in the patients with meningitis (165 days and 17 percent, respectively). From this retrospective study of cryptococcal infections in patients with AIDS we conclude that the addition of flucytosine to amphotericin neither enhances survival nor prevents relapse, but long-term suppressive therapy appears to benefit these patients.

Community-acquired bacteremia in patients with acquired immunodeficiency syndrome: clinical presentation, bacteriology, and outcome

PURPOSE

Community-acquired bacteremia is an easily treatable infection occurring in patients with acquired immunodeficiency syndrome (AIDS). Although other studies have reported bacterial infections in AIDS patients, none have clearly described the clinical presentation of these patients. In this survey, we sought to define how frequently AIDS patients presented to our institution with community-acquired bacteremia; which organisms and sources of bacteremia were involved; the frequency that these patients presented with abnormal vital signs and white blood cell counts; and the in-hospital outcome of these patients.

PATIENTS AND METHODS

We retrospectively identified patients with AIDS hospitalized at San Francisco General Hospital in the 16 months between August 1986 and December 1987 in whom a positive blood culture was drawn within 24 hours of admission. Each of the patient's charts was reviewed for demographic data, relevant past medical history, clinical admission information, laboratory data, and discharge status.

RESULTS

We identified 44 episodes of community-acquired bacteremia in 38 patients with AIDS. These episodes represented approximately 5% of the admissions of patients with AIDS. The patients were young (mean age, 38 +/- 7 years), homosexual (43 of 44), and in some cases intravenous drug users (nine of 44). On admission, only 57% of the patients were febrile (temperature greater than 38.3 degrees C) and 23% of the patients presented with normal vital signs. Twenty-seven percent were neutropenic (less than 1,000 neutrophils/mm3). The most common sources of the bacteremia were pneumonia (10), an indwelling central venous line (eight), and cellulitis (seven). A total of 14 patients had no apparent source. Staphylococcus aureus, Streptococcus pneumoniae, and Escherichia coli were the most common organisms. Only four of the 44 patients died during their hospitalization.

CONCLUSION

We conclude that patients with AIDS and community-acquired bacteremia can present to the hospital without abnormal vital signs or white blood cell counts. Clinicians cannot depend on these data to assist them in excluding the possibility of bacteremia in patients with AIDS. In addition, due to the variety of organisms found in our survey, we recommend that broad-spectrum antibiotics should be the empiric therapy in patients with a suspected bacterial infection.

Influence of antibiotic dose, dosing interval, and duration of therapy on outcome in experimental pneumococcal meningitis in rabbits

We examined the influence of several pharmacokinetic parameters on cure rates in rabbits with experimental pneumococcal meningitis. When the duration of treatment was kept constant, cure rates improved as the individual dose of ampicillin was increased. On the other hand, when four doses of ampicillin at 60 mg/kg of body weight, producing peak concentrations in cerebrospinal fluid (CSF) of approximately 40 times the MBC, were administered at intervals of 24 instead of 4 h and the duration of therapy was thus prolonged from 12 to 72 h, cure rates also increased (85 versus 25%; P less than 0.01). These high cure rates were achieved even though bacterial titers in CSF 24 h after the first dose had reached levels similar to those present at the beginning of therapy. Cure in these animals was explained by the fact that the second ampicillin dose reduced bacterial titers in CSF significantly more than did the first dose (5.2 versus 2.5 log10 CFU/ml; P less than 0.02). The clinical relevance of these observations remains to be determined.