PubMed · 6727434
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C M Johnson, K H Rhodes, J A Katzmann. 1984. Neutrophil function tests.. https://doi.org/10.1016/s0025-6196(12)61469-4
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Freshly isolated gonococci upon subculture are readily lysed by normal human serum although a few strains remain inherently resistant to the complement activity. The sensitive gonococci can be converted to serum resistance by incubation with a host derived factor referred to as cytidine 5'-monophospho-N-acetylneuraminic acid (CMP-NANA). These gonococci resist complement mediated killing due to their sialylation of an epitope structure on a component of lipo-oligosaccharide (LOS). In the present study, the kinetics of conversion to serum resistance by the action of sialyltransferase (STase) in Neisseria gonorrhoeae was followed with very low concentrations of CMP-NANA. This conversion could not be perceived at 2 x 10(-3) nmol.ml-1 but was fully attainable from 8 x 10(-3) to 2 x 10(-2) nmol.ml-1 CMP-NANA. When pretreated up to 100 min in presence of the very low concentration of 2 x 10(-3) nmol.ml-1, a potentiating effect on the conversion of gonococci by 2 x 10(-2) nmol.ml-1 was observed in relation to the time of preincubation. This action was abolished after exposure to a subinhibitory concentration of chloramphenicol (0.5 microgram.ml-1). The gonococci recovered their ability to convert to serum resistance following adequate washing. The potential for increase in STase activity should be of interest for understanding the conversion from a serum sensitive to a serum resistance state.
H. influenzae type b strains show phase variation between opaque (O) and translucent (T) colony phenotypes. These phenotypic differences have been related to differences in virulence for infant rats. This study shows that the switch between O and T colony phenotypes is associated with variation in the amount of cell-associated capsule in the serotype b strains Rd:b+:01, RM7004 and Eagan. O colonies comprised organisms which were more serum resistant and had more cell-associated polyribosyl ribitol phosphate (PRP) than organisms from T colonies. Strain Rd, the non-encapsulated parent of the encapsulated transformant Rd:b+:01, was constitutively translucent, consistent with its lack of capsule expression. Since previous studies had correlated O-T switching with differences in the relative molecular weight of lipopolysaccharide (LPS), LPS phenotypes of Rd and Rd:b+:01 were compared and correlated with opacity phenotype at the individual colony level. Both strains showed phase variation between higher and lower molecular weight LPS oligosaccharide structures but the prevalence of higher molecular weight LPS was greater for the capsule-deficient Rd than encapsulated Rd:b+01. Capsule-deficient mutants of strains Rd:b+:01, RM7004 and Eagan produced constitutively translucent colonies and each had a greater prevalence of higher molecular weight LPS than their encapsulated parents. These findings indicated an incomplete association between capsular O-T phase variation and LPS expression.
Porphyromonas gingivalis, a periodontal pathogen, can invade primary cultures of gingival epithelial cells. Optimal invasion occurred at a relatively low multiplicity of infection (i.e., 100) and demonstrated saturation at a higher multiplicity of infection. Following the lag phase, during which bacteria invaded poorly, invasion was independent of growth phase. P. gingivalis was capable of replicating within the epithelial cells. Invasion was an active process requiring both bacterial and epithelial cell energy production. Invasion was sensitive to inhibitors of microfilaments and microtubules, demonstrating that epithelial cell cytoskeletal rearrangements are involved in bacterial entry. P. gingivalis, but not epithelial cell, protein synthesis was necessary for invasion. Invasion within the epithelial cells was not blocked by inhibitors of protein kinase activity. Invasion was inhibited by protease inhibitors, suggesting that P. gingivalis proteases may be involved in the invasion process. Low-passage clinical isolates of P. gingivalis invaded with higher efficiency than the type strain. Serum inhibited invasion of the type strain but had no effect on the invasion of a clinical isolate. Invasion of gingival epithelial cells by P. gingivalis may contribute to the pathology of periodontal diseases.