Pigment production, enzymatic activity and antibiotic sensitivity of staphylococci: Subdivision of the pathogenic group

Staphyloxanthin: a potential target for antivirulence therapy

Staphylococcus aureus is an important and common Gram-positive bacteria which causes clinical infections and food-poisoning cases. Therapeutic schedules for treatment of S. aureus infections are facing a challenge because of the emergence of multidrug resistance strains. It is urgent to find new antiinfective drugs to control S. aureus infection. S. aureus strains are capable of producing the golden carotenoid pigment: staphyloxanthin, which acts as an important virulence factor and a potential target for antivirulence drug design. This review is aimed at presenting an updated overview of this golden carotenoid pigment of S. aureus from the biosynthesis of staphyloxanthin, its function, and the genes involved in pigment production to staphyloxanthin: a novel target for antivirulence therapy.

SOME PHYSIOLOGICAL CHARACTERISTICS OF NEOMYCIN AND KANAMYCIN-RESISTANT STRAINS OF STAPHYLOCOCCUS AUREUS

Five hundred and fifty-two strains of Staphylococcus aureus of hospital origin were resistant to penicillin, streptomycin, and tetracycline. Of these, 298 were also resistant to neomycin and kanamycin, and this resistance was related to pigment production on glycerol monoacetate agar, the production of beta-lysin, the absence of fibrinolytic and proteolytic activity, and to phage susceptibility. The use of physiological markers, the inadequacy of phage typing, and the possible reasons for the emergence of neomycin-resistant staphylococci are discussed.

Genetic and biochemical analyses of the biosynthesis of the yellow carotenoid 4,4'-diaponeurosporene of Staphylococcus aureus

The major pigment produced by Staphylococcus aureus Newman is the deep-yellow carotenoid 4,4'-diaponeurosporene; after prolonged cultivation, this pigment is in part converted to the orange end product staphyloxanthin. From this strain a 3.5-kb DNA fragment was identified which after being cloned into Escherichia coli and Staphylococcus carnosus conferred the ability to produce 4,4'-diaponeurosporene. DNA sequencing of this fragment revealed two open reading frames (ORFs) which are very likely cotranscribed. ORF1 encodes a 254-amino-acid hydrophobic protein, CrtM (M(r), 30,121). The deduced sequence of CrtM exhibits in three domains similarities to the sequences of Saccharomyces cerevisiae and human squalene synthases and phytoene synthases of various bacteria. ORF2 encodes a 448-amino-acid hydrophobic protein, CrtN, with an M(r) of 50,853 whose deduced sequence is similar to those of phytoene desaturases of other bacteria. At the N terminus of CrtN a classical FAD-, NAD(P)-binding domain is found. Spectrophotometry and gas chromatography-mass spectrometry analyses of the carotenoid production of E. coli and S. carnosus clones containing either ORF1 or both ORFs together suggest that ORF1 and ORF2 represent the dehydrosqualene synthase gene (crtM) and the dehydrosqualene desaturase gene (crtN), respectively. The results furthermore suggest that the biosynthesis of 4,4'-diaponeurosporene starts with the condensation of two molecules of farnesyl diphosphate by dehydrosqualene synthase (CrtM); it is shown that the reaction product of this enzyme is dehydrosqualene and not squalene. Dehydrosqualene (4,4'-diapophytoene) is successively dehydrogenated by a desaturase (CrtN) to form the yellow main intermediate 4,4'-diaponeurosporene.

Pigments of Staphylococcus aureus, a series of triterpenoid carotenoids

The pigments of Staphylococcus aureus were isolated and purified, and their chemical structures were determined. All of the 17 compounds identified were triterpenoid carotenoids possessing a C30 chain instead of the C40 carotenoid structure found in most other organisms. The main pigment, staphyloxanthin, was shown to be alpha-D-glucopyranosyl 1-O-(4,4'-diaponeurosporen-4-oate) 6-O-(12-methyltetradecanoate), in which glucose is esterified with both a triterpenoid carotenoid carboxylic acid and a C15 fatty acid. It is accompanied by isomers containing other hexoses and homologs containing C17 fatty acids. The carotenes 4,4'-diapophytoene, 4,4'-diapophytofluene, 4-4'-diapophytofluene, 4-4'-diapo-zeta-carotene, 4,4'-diapo-7,8,11,12-tetrahydrolycopene, and 4,4'-diaponeurosporene and the xanthophylls 4,4'-diaponeurosporenal, 4,4'-diaponeurosporenoic acid, and glucosyl diaponeurosporenoate were also identified, together with some of their isomers or breakdown products. The symmetrical 4,4'-diapo- structure was adopted for these triterpenoid carotenoids, but an alternative unsymmetrical 8'-apo-structure could not be excluded.

The identification of staphylococci in clinical and food microbiology laboratories

A comprehensive review of the methods which have been utilized for the identification of staphylococci is presented. Biochemical characteristics which have assisted in the primary isolation of staphylococci, such as pigmentation, hemolytic activity, the egg yolk phenomenon, and deoxyribonuclease and coagulase production, are also analyzed. The potential applicability of advanced techniques to identify staphylococci, such as the detection of enterotoxin production, base ratio analysis, cell wall analysis, phage typing, and serology, is discussed. The following procedures are recommended for routine use: Idnetification of Staphylococcus sp. (clinical laboratories): microscopic observation, catalase activity, coagulase production, lysostaphin sensitivity, and (optional) facultative growth in thioglycolate medium. Identification of Staphylococcus aureus (food laboratories): microscopic observation, catalase activity, coagulase production, thermonuclease production, and (optional) lysostaphin sensitivity.

Mercury resistance and tetracycline resistance in Staphylococcus aureus

Minimum inhibitory concentrations of tetracycline to 256 tetracycline-resistant strains ofStaphylococcus aureuswere determined. M.I.C.'s tetracycline were appreciably higher among mercury resistant than among mercury sensitive strains.

Mercury resistant strains representing various M.I.C.'s tetracycline grew significantly better in peptone water containing a therapeutic concentration of tetracycline than mercury sensitive strains representing the same range of resistance. The experiment was repeated after both groups had been adapted—or ‘trained’—to grow on agar containing tetracycline, 100µg./ml. The mercury sensitive strains now grew better than the mercury resistant group.

The significance of these findings is discussed. It is concluded that tetracycline resistance is more stable and efficient in mercury resistant strains, and that it is probably genetic in origin—the result of mutation and selection. Tetracycline resistance in mercury sensitive strains is possibly the result of ‘training’.

The associations and significance of both mercury resistance and tetracycline resistance inStaphylococcus aureusare discussed.

Cultural characters of a newly recognized group of hospital staphylococci

Members of a newly recognized group of hospital staphylococci, which are believed to have arisen from 83A staphylococci by lysogenization, differ from them in several cultural characters. Some but not all of these characters appear to be determined by the carriage of phage.