Influence of Sub-Inhibitory Concentrations of Penicillin G on Surface Properties of Iron-Deprived Staphylococcus Aureus NCTC 6571

Abstract

The surface properties of batch cultures of Staphylococcus aureus NCTC 6571 (OXFORD) grown with 48- and 24-minute doubling times in iron-depleted Tryptone Soy Broth were studied after treatment with 1/16 MIC of penicillin G.

Growth rate influenced surface hydrophobicity. Slow-grown phenotypes, particularly iron-poor ones, had low contact angles generally, but these were increased by iron excess and/or penicillin. Opsonisation also significantly increased contact angles. All fast-grown phenotypes had much higher, uniform contact angles regardless of iron or penicillin status.

Low numbers (10–20 cocci:1 neutrophil) of the slow-grown iron-poor phenotype provoked the least chemiluminescence, had the lowest neutrophil association values, and were least susceptible to whole blood killing. The other phenotypes behaved in a manner that generally reflected their relative hydrophobicities.

Alterations in growth rate significantly affected Protein A production and adherence to polyvinyl chloride catheters, whilst iron deprivation and/or penicillin induced minor changes. Little effect was noted upon the production of staphylocoagulase and alpha-haemolysin.

Immunoblotting profiles were greatly simplified by iron deprivation and/or penicillin treatment. Growth rate alterations had no effect. Non-immune sera recognised the iron-poor preparations better than the iron-rich. Analysis of iron-poor and iron-rich preparations of S. aureus Hopewell, an endocarditis isolate, using the patient’s immune serum, also confirmed this trend in both immunoblotting and ELISA.

Date of Award	1986
Original language	English
Awarding Institution	Aston University