Nosocomial infection with penicillin-resistant pneumococci in patients with AIDS

Nosocomial infections in patients with HIV disease

Throughout the AIDS epidemic, nosocomial infection in the patient with HIV disease has presented a constant problem--not only for the hospitalized patient but also for the clinic attender. The nosocomial spread of multidrug-resistant tuberculosis has emphasized the need for effective control of infection measures in dealing with the immunodeficient. Increased recognition of nosocomial bacterial pneumonias has raised questions about the place, if any, of antimicrobial prophylaxis in preventing Gram-negative and Legionella infection. The use of long-term indwelling venous catheters for the administration of parenteral therapy is associated with an increased risk of nosocomial bloodstream infection--particularly from staphylococci and Pseudomonas spp. Evidence now exists for the nosocomial spread of opportunistic infections, including Cryptosporidium parvum, Mycobacterium avium complex and Pneumocystis carinii. The delay between exposure and diagnosis, the atypical presentation of infections such as tuberculosis and repeated hospital admissions of AIDS patients can combine to confuse the issue with the result that a nosocomial infection may be mis-classified as community-acquired. It seems likely that the burden of nosocomial infection in HIV disease is continually underestimated.

Nosocomial colonization and infection in persons infected with human immunodeficiency virus

Nosocomial infections appear to be increased in patients with acquired immunodeficiency syndrome (AIDS), compared to individuals with asymptomatic infection due to human immunodeficiency virus (HIV). Risk factors for bacterial colonization and infection include immunosuppression, prior treatment with some antibiotics, increased hospitalizations with longer lengths of stay, greater exposure to invasive devices such as indwelling intravenous or urinary catheters, and the degree of immunosuppression. Data suggest that other infectious agents such as Pneumocystis carinii, Mycobacterium tuberculosis, Mycobacterium avium complex, and Cryptosporidium may be acquired in healthcare facilities. Diagnosis and management of nosocomial infections in HIV-infected persons may be complicated by an atypical presentation, increased rates of relapse following treatment, presence of multiple infections, and early discharge from the inpatient setting. Accurate assessment of nosocomial infections and outbreaks in the hospital is complicated by limited data on the risk of transmission of both traditional and unusual pathogens in this population. Furthermore, some patients may acquire nosocomial pathogens during their initial hospitalization and present later with infections that normally would be classified as community acquired. Therefore, there probably is an underestimation of current nosocomial infection rates, and perhaps "hospital-associated" or "healthcare-facility-associated" might be more accurate terms for these infections.

Bacterial pneumonia in adult patients with HIV infection

Patients with HIV infection are at increased risk for community-acquired bacterial pneumonias, due in part to their defects in B-cell function. Streptococcus pneumoniae is the commonest cause of community-acquired pneumonia, with the second most common bacterial agent being Haemophilus influenzae. These two organisms account for about two-thirds of community-acquired bacterial pneumonias. Frequently bacterial pneumonias appear difficult to distinguish from Pneumocystis carinii pneumonia or other opportunistic lung infections, because of their atypical clinical and radiologic presentations. Community-acquired pneumonias may be recurrent but have low fatality rates. In comparison, nosocomial pneumonias occur primarily in patients with AIDS and are usually due to Staphylococcus aureus, Pseudomonas aeruginosa and other aerobic gram-negative bacilli. Nosocomial pneumonias have high fatality rates. S.aureus is an important cause of morbidity and mortality in patients with AIDS and has emerged as a secondary opportunist in lungs of patients with opportunistic diseases. While appropriate laboratory study is being done, empiric antibiotic therapy should be directed against the microorganisms above described.

Pneumococcal vaccine and HIV infection: report of a vaccine failure and reappraisal of its value in clinical practice

A clinical failure of pneumococcal vaccine is reported. A 22 year old African woman was given 23-valent pneumococcal vaccine at her initial presentation with HIV infection. She was asymptomatic and had a CD4+ lymphocyte count above 500 cells/mm3. Eighteen months later she died of meningitis and septicaemia due to Streptococcus pneumoniae type 9 (an antigen included in the 23-valent vaccine). Pneumococcal antibody levels performed on stored blood demonstrated no serological response to the vaccine. This is the first reported case of clinical failure of pneumococcal vaccine in an HIV infected patient who received vaccine whilst at the asymptomatic stage of HIV infection and with relatively intact immune function. The literature pertaining to pneumococcal vaccination in the context of HIV infection was reviewed. Pneumococcal vaccination is recommended for HIV positive patients in the UK by the Departments of Health. It is likely that many physicians are not aware of these recommendations or are concerned about the poor efficacy of the vaccine, and it may consequently be underused in clinical practice. But the potential gain to the HIV positive patient is such that the vaccine should be offered to all HIV positive patients as soon as they present for medical care, irrespective of the stage of HIV disease. Physicians and patients should be aware that the vaccine is not fully protective and that episodes of sepsis, pneumonia and meningitis could still be pneumococcal in origin and should be treated appropriately. Awareness of the substantial risks of pneumococcal disease in HIV infected patients with prompt diagnosis and effective treatment is the most important strategy to decrease morbidity and mortality.

Management of infections caused by antibiotic-resistant Streptococcus pneumoniae

The increasing resistance of S. pneumoniae to antimicrobial agents is a cause for concern. Although a number of therapeutic strategies are possible, local patterns of resistance must be considered. It is essential to determine the susceptibility of individual strains to penicillin and other antimicrobial agents that could be used for therapy. Communication between the clinician and the laboratory is vital to determine the best therapeutic options. The recent recognition of cephalosporin-resistant strains emphasizes the need to determine susceptibility to cephalosporins. Clinical laboratories should be aware of the recently proposed changes in the definition of cephalosporin resistance, and clinicians need to be aware of how these changes affect the choice of antibiotic therapy. Until pneumococcal disease can be effectively prevented, we can expect resistant pneumococcal infections to continue to pose therapeutic difficulties.

Co-existent cross-infection with Streptococcus pneumoniae and group B streptococci on an adult oncology unit

An outbreak of respiratory infection in an adult oncology unit is described where there was evidence of co-existent cross-infection with Streptococcus pneumoniae serotype 14 and Lancefield group B streptococcus type Ia. The presumed route of transmission was droplet spread from patient to patient. No further cases arose after the ward had been closed to new admissions and all symptomatic patients were treated with erythromycin. We suggest that patients with pneumococcal pneumonia on units housing elderly debilitated patients should be isolated. Infection control teams should be aware of the ability of Lancefield group B streptococci to spread by cross-infection among adult patients.

Pneumococcal polysaccharide vaccines: indications, efficacy and recommendations

Streptococcus pneumoniae is the primary cause of community-acquired pneumonia, meningitis in adults and otitis media in infants and children and the third cause of meningitis in infants and children. Despite the availability of effective therapeutic agents against this pathogen, mortality has remained high, particularly for infections complicated by bacteremia. For many years, there has been a plea for vaccination. The first steps, using whole bacterial vaccines, were taken during the early decades of this century in the gold mining camps of South Africa, where pneumonia was endemic. The efficacy of purified pneumococcal polysaccharide vaccines has since been demonstrated in young adults, such as gold miners and military recruits, as well as for several other groups at risk, such as institutionalized elderly, patients with sickle cell anemia or those who have undergone a splenectomy, and elderly patients with underlying conditions such as chronic obstructive pulmonary disease and chronic cardiovascular disease, but not in infants and severely immunocompromised patients. Serological studies on the immune response to inoculation of pneumococcal polysaccharide antigens have demonstrated a severely impaired antibody response in the last two groups. Therefore, development of more highly immunogenic vaccines, e.g. by linking pneumococcal polysaccharides or parts of them to protein carriers, should be continued in an attempt to offer adequate protection to those who are insufficiently protected by the current 23-valent polysaccharide vaccine. Opportunities to immunize other patients who are at risk for pneumococcal infection and are capable of responding to the current vaccine should not be missed.