Antimicrobial activities of ceftazidime on fresh clinical isolates]

Antimicrobial activity of ceftazidime (CAZ) was compared with those of other cephem antibiotics against clinically isolated strains sent to us by medical institutions throughout Japan in 1989 and 1991. Those strains separated and identified from samples collected from patients with various infections were also examined, and the following results were obtained. 1. The results suggested that, compared with reports of studies conducted with clinical isolates in early 1980's, MIC90 of CAZ in 1991 were markedly higher against Staphylococcus spp., Streptococcus pneumoniae, Escherichia coli, Enterobacter spp., Serratia marcescens, Proteus vulgaris, Morganella morganii, and Pseudomonas aeruginosa. Also, among other bacteria such as Providencia rettgeri, Providencia stuartii, Xanthomonas maltophilia, and Bacteroides fragilis group, strains resistant to CAZ were observed in high proportions. However, large time-course changes were not observed in microbial activities of CAZ on Streptococcus pyogenes, Klebsiella spp, Proteus mirabilis, Pseudomonas cepacia, Acinetobacter calcoaceticus, Haemophilus influenzae and Anaerobic GPC (Gram-positive cocci). 2. Among the strains used in the study, methicillin-resistant Staphylococcus aureus (MRSA), Benzylpenicillin (PCG)-insensitive S. pneumoniae (PISP), cephamycin and oxime type cephem-resistant Gram-negative bacilli of Enterobacteriaceae and new quinolone-resistant organisms were observed in high proportions. It appears therefore, that CAZ failed to exert sufficient antimicrobial activities to these strains because of combination of resistance in these strains. 3. Antimicrobial activities of CAZ on recent clinical isolates showed problems as mentioned above. However, it was also demonstrated that CAZ maintained effective antimicrobial activities against most of the clinical isolates which could be causative organisms of infectious diseases in the clinical practice. When it is additionally taken into account that CAZ is one of those limited drugs with activity against P. aeruginosa, and it has excellent permeability through outer membrane, it is concluded that CAZ still is one of the clinically useful cephem drugs in 1990's.