Phagocytes, antibiotics and intracellular parasites: are the experimental data clinically relevant?

Expression of lysostaphin in HeLa cells protects from host cell killing by intracellular Staphylococcus aureus

The Staphylococcus aureus-specific cell wall endopeptidase lysostaphin was used as a model for an intracellular acting bactericidal antibiotic. HeLa cells were transfected with an expression vector directing the heterologous expression of lysostaphin in the cytoplasm. Expression, subcellular localization and enzymatic activity of lysostaphin were investigated by immunoblotting, fluorescent microscopy and agar diffusion assays. Both transiently and stably transfected HeLa cells showed a strong expression of active lysostaphin. After infection with S. aureus, the intracellular number of S. aureus and the host cell viability were determined. This staphylolytic activity resulted in a strong reduction of intracellular S. aureus in a time- and dose-dependent manner. Furthermore, host cells expressing lysostaphin became protected from S. aureus-induced cell death. Our data demonstrate the potential of intracellularly acting cell-wall active drugs or antibiotics that kill S. aureus without causing harm to the infected host cells.

Morphologic evaluation of the pathogenesis of bacterial enteric infections

Current advances in the understanding of the pathogenicity of the agents of diarrheal infections, Vibrio cholerae, diarrheagenic E. coli, Shigella, Salmonella, and enteropathogenic Yersinia, have, to a great extent, become possible due to morphological studies of host-pathogen interactions in natural and experimental infections. Despite a multigenic nature and a diversity of pathogenic features in the bacterial species and even in serogroups of the same species, it is now possible to delineate four major patterns of interaction of enteric pathogens with their cellular targets, the enterocytes, and with the immune apparatus of the gut. These patterns, epicellular cytotonic, epicellular restructuring cytotonic, invasive intraepithelial cytotonic and cytotoxic, and invasive transcellular cytotonic and cytotoxic bacteremic, underlie early pathogenesis and clinical manifestations in the respective diarrheal diseases. In this review, the results of the morphological analyses of these patterns over the last 3 decades as well as some methodological problems encountered in the interpretation of morphological observations are discussed.

Medical management of ocular malakoplakia

A 14-year-old girl had a granulomatous conjunctival lesion, proven histologically to be malakoplakia. This is the first reported case of malakoplakia arising from conjunctiva, although three others have involved the ocular adnexa. Malakoplakia is a rare disease often associated with immunodeficiency and is characterized by the presence of intracellular inclusions and organisms due to deficient intracellular bacteriolysis. Medical management is difficult because an effective antibacterial agent requires three properties: activity against the organism involved, good intracellular penetration, and the capacity to maintain its effectiveness in the intracellular milieu. Escherichia coli was isolated from a biopsy specimen and from conjunctival swabs. Treatment with systemic ciprofloxacin, which has good intracellular penetration and activity, led to rapid resolution of the lesion. This is the first report concerning the successful use of this drug to treat malakoplakia of any organ.