[Clinical laboratory approach for estimating the effective administrative dose of latamoxef. Significance of a 4-category system interpretation of the latamoxef disc susceptibility test].
In vitro activities of latamoxef (LMOX) against 249 clinical isolates were determined using the agar dilution method at an inoculum level of 10(6) CFU/ml. LMOX was highly active against Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis (except 2 out of 30 strains) and Proteus vulgaris with MIC values below 3.13 micrograms/ml. It was also active against Enterobacter aerogenes with MIC80 of 1.56 micrograms/ml. LMOX was less active against Serratia marcescens, inhibiting about 43% of strains at a level of 6.25 micrograms/ml. It was also less active against Staphylococcus aureus and Staphylococcus epidermidis, showing MIC80 of 12.5 and 50 micrograms/ml, respectively. LMOX was not active against Enterococcus faecalis and Pseudomonas aeruginosa. The reliability of the LMOX disc diffusion susceptibility test for quantitative estimation of antimicrobial activities was also investigated using 8 mm diameter discs (Showa) and 6 mm diameter discs (Difco), both of which contained 30 micrograms/disc of LMOX. These disc susceptibility test results were well correlated with MICs, hence the LMOX disc susceptibility test should be useful for the estimation of proper dose levels of LMOX. For the interpretation of LMOX disc test results, if uniform break points of zone diameters were used to test all bacteria, inhibitory zone diameters of Showa discs used on Staphylococcus were relatively large compared to MICs determined, probably due to decarboxylation of LMOX sodium salt in the discs. However, those of Difco discs were not, because Difco discs use LMOX ammonium salt. Both discs also showed relatively large inhibitory zone diameters compared to MICs determined against P. aeruginosa. Using different break points from those used for other bacteria to interpret inhibition zones for Staphylococcus and P. aeruginosa, these disc susceptivility tests should be useful to estimate approximate MICs. A 3 category system for the interpretation of disc test results has been used in USA and Europe, but a 4 category system is generally used in Japan. The 3 category system uses break points to classify bacteria into 3 categories of susceptibility according to MIC values as follows: Resistant (R) MIC greater than or equal to 64 micrograms/ml, intermediate (I) MIC 16-32 micrograms/ml, and susceptible (S) MIC less than or equal to 8 micrograms/ml. The 4 category system uses break points as follows: MIC less than or equal to 3 micrograms/ml, MIC greater than 3-15 micrograms/ml, (+) MIC greater than 15-60 micrograms/ml, (-) MIC greater than 60 micrograms/ml.(ABSTRACT TRUNCATED AT 400 WORDS)
Uete
T
T
Department of Clinical Investigation, Kitano Hospital.
Matsuo
K
K
D004926:Escherichia coli / Q000187:drug effects; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods*; D009070:Moxalactam / Q000008:administration & dosage / Q000494:pharmacology*; D013210:Staphylococcus / Q000187:drug effects
D009070:Moxalactam