3. Electronic Theses and Dissertations (ETDs) - All submissions

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Antibiotic resistance in viridans streptococci
(1994) Potgieter, Elsa
Viridans streptococci are aetiological agents of endocarditis, bacteraemia, dental caries and abscesses of the liver, brain and joints. Viridans streptococci had until recently generally been considered to be uniformly susceptible to antimicrobial agents active against Gram-positive cocci. The susceptibility of 211 viridans streptococci isolated from blood in South Africa between 1988-1991 to eight antimicrobial agents was determined. Thirty-eight percent of the isolates were found to be resistant to penicillin (MICs >0.25 /Mg/ml). Five Streptococcus mitis isolates exhibited increased (MIC 64 and 128 ^g/ml) or high-level (MIC >500 /Mg/ml) resistance to gentamicin. In vitro synergy between penicillin and gentamicin was not demonstrated with these isolates.
Effect on oral streptococci of exposure to penicillin and its relevance in infective endocarditis prophylaxis
(1996-03) Mclure, William . Peter. John
The survival of bacteraemic isolates of viridans streptococci, after the administration to subjects of prophylactic antibiotic cover, has been widely reported in the literature. This study demonstrated that the cause of bacteraemia was as a result of phenotypic tolerance amongst populations of bacteria, and both proposed a mechanism responsible for the appearance of this form of tolerance and the design of a model to evaluate candidate drugs for infective endocarditis (IE) prophylaxis