The new API 20C yeast identification system together with appropriate microscopic morphology determinations achieved a 97% correlation with a rapid conventional method. Whereas a group composed of Candida, Torulopsis, Saccharomyces, and Rhodotorula was identified with ease (98% overall correlation), a second group, containing Cryptococcus, Trichosporon, and Geotrichum species, appeared to give the system the most difficulty (90% correlation). Within this group particular difficulty was encountered in identifying varieties of Cryptococcus albidus, C. terreus, C. laurentii, Trichosporon beigelli, and Geotrichum spp. as to species. The API 20C system should be incubated the full 72 h prescribed by the manufacturer. However, when used in conjunction with appropriate morphological tests, presumptive identifications of some Candida and Torulopsis species may be made at 24 to 48 h. To facilitate identifications of the more difficult group of yeasts, ancillary tests for determining nitrate reductase, urease, and phenol oxidase activities should be considered as additions to the strip. Incorporating the phenol oxidase test would be especially important for identification of Cryptococcus neoformans, a yeast which should be identified as quickly and as accurately as possible. The API 20C system with computer assistance has proved to be an easy-to-inoculate, versatile, and fairly rapid method of yeast identification, giving results comparable to those obtained by conventional methodologies.

2-Chlorotyrosine and 2-bromotyrosine, as well as the previously reported 2-fluorotyrosine, were synthesized by hydrolysis of the condensation products from the appropriate benzyl bromide and ethyl acetamidomalonate and were compared with the corresponding 3-halotyrosines as growth inhibitors of Escherichia coli 9723, Streptococcus faecalis 8043 and Lactobacillus plantarum 8014. In contrast to the 2- and 3-fluorotyrosines which were equally effective as growth inhibitors, the 2-chloro- and 2-bromotyrosines were much more effective than the 3-chloro- and 3-bromotyrosines in inhibiting the growth of the three microorganisms. For each of the assay organisms, the growth inhibitions of all three 2-halotyrosines were reversed competitively in varying degrees by tyrosine.

The effects of a chloro substituent upon the microbiological activities of 3-amino-3,4-dihydro-1-hydroxycarbostyril were determined. The 5-, 6-, and 7-chloro analogs were synthesized by reductive cyclizations of the appropriately chloro-substituted o-nitrophenylalanines, while the 8-chloro analog was obtained from the N-trifluoroacetyl-3-chloro-2-nitrophenylalanine ethyl ester. All of these compounds were observed to inhibit the growth of Escherichia coli 9723, Leuconostoc dextranicum 8086, and Lactobacillus plantarum 8014. The relative inhibitory activities of the chloro analogs were 7-Cl greater than 6-Cl greater than 8-Cl greater than 5-Cl in E. coli and 7-Cl greater than 6-Cl greater than 8-Cl = 5-Cl in L. dextranicum and L. plantarum. In each of the three microorganisms, the 7-Cl analog was a more effective growth inhibitor than the parent unsubstituted compound. The growth inhibitory activities of this class of compounds were demonstrated to be much more effective than those of the four corresponding lactams, the 5-, 6-, 7-, and 8-chloro analogs of 3-amino-3,4-dihydrocarbostyril.

When examined in an amino acid supplemented inorganic salts – glucose medium, the morphological development of Candida albicans 5865 is inhibited or delayed by several drugs common to cancer chemotherapy protocols. Yeast phase growth is inhibited by actinomycin D (100 μg/mL), bleomycin (500 μg/mL), 5-fluorouracil (1000 μg/mL), and hydroxyurea (1000 μg/mL). Germ tube formation was also inhibited by actinomycin D (100 μg/mL), and vincristine (100 μg/mL), doxorubicin and bleomycin (each at 500 μg/mL), and 5-fluorouracil, cyclohexamide, hydroxyurea, and vinblastine at 1000 μg/mL, respectively. Following a 3-h exposure to the above drugs supplemented with sublethal concentrations of amphotericin B (AMB), yeast germination and chlamydospore formation were delayed 60–96 h. Culturing yeasts for 24 h in the presence of both AMB and actinomycin D resulted in a 90% loss in viability. Two antimetabolites not common to chemotherapeutic protocols also showed fungistatic and fungicidal activity. At 24 h, pentamidine isethionate (100 μg/mL) alone had a 90% kill rate which increased to greater than 99.99% when combined with AMB. A cyclic hydroxaneic acid, 7-chloro-3,4-dihydro-1-hydroxycarbostyril (7-Cl ADHC), demonstrated the lowest minimum germ tube inhibitory concentration (1 μg/mL). A 90% kill rate was obtained after culturing yeasts for 24 h in 7-Cl ADHC (100 μg/mL) supplemented with AMB.

Against Enterobacter aerogenes 13048, Serratia marcescens 13880, Klebsiella pneumoniae 10031, Pseudomonas aeruginosa 10145, Escherichia coli 9723, Lactobacillus casei 7469, Lactobacillus plantarum 8014, Leuconostoc dextranicum 8086, and Streptococcus faecalis 8043, the mean minimal inhibitory concentrations of three cyclic hydroxamic acids, 3-amino-3,4-dihydro-1-hydroxycarbostyril, the 6-chloro analog, and the 7-chloro analog, were 0.6, 0.6, and 0.2 ug/ml, and those of the corresponding lactams, 3-amino-3,4-dihydrocarbostyril, the 6-chloro analog, and the 7-chloro analog, were 60, 60, and 6 ug/ml, respectively. Under the same assay conditions the mean minimal inhibitory concentrations of chloramphenicol and kanamycin were both 2 pug/ml. In addition, the cyclic hydroxamic acids but not the lactams inhibited the growth of Candida albicans at miniimal inhibitory concentrations ranging from 20 to 200 pg/ml, at pH 7, as compared with that of amphotericin B, at 2 pg/ml.