Direct identification of Staphylococcus aureus in blood culture fluid with a commercial latex agglutination test

Abstract

A kinetic study of induction of the enzymes of the lactose operon was carried out under conditions known to affect the kinetics of derepression of the enzymes of the histidine operon. The results show that the lactose system is similar to the histidine system in its responsiveness to conditions thought to affect the formylating capacity of the cell. This was demonstrated in the following ways: (i) trimethoprim, which is known to reduce the formylating capacity of the cell, gives rise to a relatively long interval between the times of induction of 3-galactosidase and transacetylase; (ii) under conditions in which the histidine operon is derepressed, chloramphenicol causes a prolongation of the interval between the times of induction of the two enzymes, and this prolongation is reversed by adenine, methionine, and serine, compounds known to enrich the one-carbon pool of the cell; and (iii) 4-amino-5-imidazolcarboxamide ribonucleoside, a compound which may act as a drain for formyl groups, reverses the effect of the latter compounds. The finding that the interval between the times of induction of the two enzymes is shortened under conditions expected to maintain a relatively high intracellular fo rmylating capacity suggests that under certain conditions translation of the polycistronic messenger ribonucleic acid of the lactose operon may be initiated at more than one site or may proceed more rapidly from the operator end. From previous studies on the kinetics of derepression of the histidine enzymes in a wide variety of histidine auxotrophs of Salmonella typhimurium, it was concluded that derepression may occur either simultaneously or sequentially, depending upon the formylating capacity of the cell (8). The enzymes became derepressed simultaneously in those mutants with an adequate formylating capacity, whereas they became derepressed in a temporal sequence, corresponding to the order of the genes in the histidine operon, in those mutants with a reduced formylating capacity. The reason for the differences in formylating capacity among the various histidine auxotrophs is that those mutants with a block in any of the last four steps of the histidine pathway produce phosphoribosyl aminoimidazole carboxamide (PR-AIC) as a byproduct of the path

Direct testing of blood culture for detection of the serotype 5 and 8 capsular polysaccharides of Staphylococcus aureus

“…Rapid identification of bacteria in blood cultures is of utmost importance for diagnosis and treatment of bacteremia. Latex agglutination of particles coated with human plasma (5) and a lysostaphin sensitivity test (15) have been applied for rapid identification of S. aureus in blood cultures.…”

Evaluation of various rapid agglutination methods for the identification of Staphylococcus aureus

“…The primary advantage to each of these methods is that test results are available within minutes after primary isolation procedures. The sensitivities of these rapid agglutination methods have been outlined in previous reports, and discrepancies have been noted (1,4,5,6,9).…”

Rapid detection of oxacillin-resistant Staphylococcus aureus in blood cultures by an impedance method

“…Although some coagulase-negative staphylococci (e.g., S. intermedius, S. hyicus, and S. delphini) (8) were found to produce thermonuclease, these species are rarely found in blood cultures (unpublished data, National Cheng Kung University Hospital) and were not misidentified as S. aureus in this study. A more simple latex agglutination test also can be used to rapidly identify S. aureus in blood cultures (11); however, the bacterial cells in the culture broth need to be concentrated by centrifugation before the latex test can be performed. A 2-h tube coagulase test also can be used to rapidly identify S. aureus from blood culture bottles (19).…”

“…The five most common isolates from blood cultures were Escherichia coli Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Streptococcus pneumoniae (5). S. aureus, when found in blood cultures, is usually representative of significant clinical disease (11), and prompt action is necessary.…”