Adherence of gram-negative bacteria (GNB) to epithelial surfaces is important for GNB colonization to occur. Pili, rodlike structures projecting from the outer membrane of GNB, and GNB surface hydrophobicity have been shown to enhance GNB adherence. We investigated the types of pili and the hydrophobicity of aerobic GNB colonizing the stomach, oropharynx, and trachea of critically ill patients. Piliation and hydrophobicity of oral, tracheal, and gastric GNB were compared with that of commensal GNB isolated from patients' rectums. Significantly more oropharyngeal than rectal GNB were piliated, and the most common type of pili present was type 1, or mannose-sensitive pili. Mannose-resistant and P pili were present less often, and no colonizing GNB had S pili. Colonizing GNB were hydrophilic rather than hydrophobic, and no differences in hydrophobicity were noted between colonizing GNB and rectal isolates. Our results suggest that pili may be important for oropharyngeal GNB colonization.
A case of Listeria monocytogenes induced spontaneous bacterial peritonitis (SBP) is reported in a patient with primary biliary cirrhosis. It is an indolent illness and may not show a neutrophil reaction in peritoneal fluid. Enrichment broth was required to isolate L monocytogenes in the patient. This is not routinely used in the UK and therefore isolates may be missed. L monocytogenes remains sensitive to ampicillin, penicillin and gentamicin, but is resistant to cephalosporin antibiotics. The rising incidence of listeriosis in the population suggests that the incidence of SBP from L monocytogenes is likely to increase.
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