COMPARATIVE STUDIES ON ACTIVITIES OF ANTIMICROBIAL AGENTS AGAINST CAUSATIVE ORGANISMS ISOLATED FROM URINARY TRACT INFECTIONS (1985)

I. SUSCEPTIBILITY DISTRIBUTION

Abstract

It has been more than 4 years since third-generation cephems were introduced into clinical practice. The range of our drug selection definitely tends to increase, because we today have more antibiotics with wider spectrum, antibiotics with strong activities only against Gram-negative strains, such as monobactams, and those with tremendously high activities such as quinolone carboxylic acid derivatives, in comparison to those we had in the past.
Among isolates obtained mainly from sputa of 567 patients with lower respiratory tract infections at 16 institutions throughout Japan between September of 1985 and March of 1986,741 strains were determined to be causative organisms. MIC's of various antimicrobial agents were determined against 67 strains of Staphylococcus aureus, 100 strains of Streptococcus pneumoniae, 199 strains of Haemophilus influenzae, 92 strains of non-mucoid Pseudomonas aeruginosa, 40 strains of mucoid P. aeruginosa, 29 strains of Klebsiella pneumoniae, 10 strains of Escherichia coli and for 42 strains of Branhamella catarrhalis out of the above 741 strains to determine their drug sensitivities.
As for types of lower respiratory tract infections found in 1981-1983, 57.9-64.5% of the infections were chronic respiratory infections; i.e., chronic bronchitis, chronic bronchiolitis and bronchiectasis. These chronic infections, including diffuse panbronchiolitis (DPB), were found in 63.1% of lower respiratory tract infections in 1984. Their incidence dropped to 54.0% in 1985, even through DPB was included; i.e., the incidence of chronic bronchiolitis was 5.5%, that of DPB was 7.1%, and that of bronchial asthma associated with lower respiratory tract infections in 1985 was 8.8% which was twice as much as that found in 1981-1984.
Although bacterial pneumonia was found in 24.8% of all the cases in 1981, its incidence was reduced to 11.0% in 1983, 15.1% in 1984, and 17.6% in 1985. This reduction seemed to have resulted from gradual decreases in the occurrence of bacterial pneumonia among the young population. As with usual years, a high incidence rate in a total lower respiratory tract infections in 1985 was found among older patients; namely, 73.5% was at the age of 50 or over (417/567).
Next, we determined relationships between clinical isolates and isolates from respiratory infections, including chronic bronchitis, chronic bronchiolitis, bronchiectasis and DPB. H. influenzae was isolated from 50.5% of patients with these infections in 1981; however, the detection rate decreased by about 20% to 29.7% in 1985. P. aeruginosa was consistently isolated, between 24.1% and 30.4% every year. S. aureus and S. pneumoniae were isolated from 15.5% in 1981 and 20.3% in 1985, indicating a tendency toward increases. The detection rate for other Gram-negative bacteia also increased to 14.0% from 0%; Although B. catarrhalis was included in the groups of Gram-negative bacteria in 1981, its single detection was counted to be 5.1% in 1984 and 5.9% in 1985.
These results suggested that clinical isolates were more diversified in species year by year.
The trend was similar in bacterial pneumonia, the detection rate of Gram-positive cocci, including S. aureus and S. pneumoniae, being 32.4%.
The relation of antibiotic treatments to the number of isolates, which were then determined to species was examined. A total of 534 strains, mainly consisting of H. influenzae at 35.4% and S. pneumoniae at 17.4%, were isolated before treatment. The number of isolates decreased to 27 strains within 3 days after the start of treatment due to the presence of strong antibiotic effects, as we expected. However, when the treatment was prolonged to over 15 days, 92 strains were isolated and resistant strains increased in number, because infections might have become chronic. P. aeruginosa was isolated from as high as 51.1% of cases treated for a long period of time, proving the intractable nature of this organism.