Bacterial infections.

Non-opportunistic bacterial infections are an important cause of morbidity and mortality for HIV-infected adults and children. Factors associated with increased risk of these include altered B- and T-cell function; altered phagocytic cell function; skin and mucous membrane defects; and use of indwelling vascular catheters, antibiotics, or cytotoxic agents. The pathogens encountered most frequently are S. aureus, S. pneumoniae, H. influenzae, Salmonella sp., and Pseudomonas aeruginosa. Less commonly encountered organisms include Rhodococcus equi, Listeria monocytogenes, Shigella sp., and Nocardia asteroides, Strategies for prevention as well as diagnosis and treatment of these are discussed.

Immunoprophylaxis against klebsiella and pseudomonas aeruginosa infections. The Federal Hyperimmune Immunoglobulin Trial Study Group.

To determine if passive immunization could decrease the incidence or severity of Klebsiella and Pseudomonas aeruginosa infections, patients admitted to intensive care units of 16 Department of Veterans Affairs and Department of Defense hospitals were randomized to receive either 100 mg/kg intravenous hyperimmune globulin (IVIG), derived from donors immunized with a 24-valent Klebsiella capsular polysaccharide plus an 8-valent P. aeruginosa O-polysaccharide-toxin A conjugate vaccine, or an albumin placebo. The overall incidence and severity of vaccine-specific Klebsiella plus Pseudomonas infections were not significantly different between the groups receiving albumin and IVIG. There was some evidence that IVIG may decrease the incidence (2.7% albumin vs. 1.2% IVIG) and severity (1.0% vs. 0.3%) of vaccine-specific Klebsiella infections, but these reductions were not statistically significant. The trial was stopped because it was statistically unlikely that IVIG would be protective against Pseudomonas infections at the dosage being used. Patients receiving IVIG had more adverse reactions (14.4% vs. 9.2%).

Tuberculosis of the breast as a presenting manifestation of AIDS.

Tuberculous infections of the breast are considered rare in the developed world. We describe a case of mammary tuberculosis in a woman who was not initially known to be seropositive for the human immunodeficiency virus (HIV) and who was thought to have a pyogenic breast abscess. This uncommon presentation of extrapulmonary tuberculosis as an AIDS-defining condition highlights the necessity for performing mycobacterial smears and cultures in such cases when patients are at risk for HIV infection.

Stable classes of phenotypic expression in methicillin-resistant clinical isolates of staphylococci.

A collection of coagulase-positive and -negative clinical strains of staphylococci, all of which gave a positive reaction with a mec-specific DNA probe, was analyzed for the mode of phenotypic expression of methicillin resistance by using population analysis on agar plates containing different concentrations of the antibiotic. Strains could be divided into four arbitrary expression classes. Cultures of class 4 strains were composed of uniformly and highly resistant bacteria (MIC greater than or equal to 800 micrograms/ml). In contrast, cultures of strains belonging to classes 1, 2, and 3 were heterogeneous: they were composed of two or more subpopulations of cells that differed from one another in MICs and frequencies. In cultures of strains belonging to expression class 1, most of the cells had methicillin MICs of 1.5 to 3 micrograms/ml, i.e., only two to three times higher than those for truly susceptible strains. In cultures of strains belonging to expression classes 2 and 3, the methicillin MICs for the majority of bacteria ranged from 6 to 12 and up to 50 to 200 micrograms/ml, respectively. While the definition of the expression classes was arbitrary, the modes of phenotypic expression were specific and reproducible: randomly picked colonies of a given strain produced identical population profiles. The strain-specific mode of expression was also retained after numerous single-colony picks and sequential passages in antibiotic-free medium. We suggest that these classes represent stages in an evolutionary sequence leading to progressively improved phenotypic expression of methicillin resistance in staphylococci.