Susceptibility of Bacteria Isolated from the Patients with Lower Respiratory Tract Infections to Antibiotics (1987)

Since 1981, in cooperation with research institutions across the nation, Ikemoto, et al. have been collecting clinical isolates from patients with respiratory tract infections and conducting an annual retrospective survey of patients' background factors and of isolated strains and their sensitivities to various antibacterial agents and antibiotics. In the period from October, 1987 to September, 1988, 17 institutions participated in the survey and a total of 706 strains which were demonstrated to be causative organisms were isolated from 562 patients with respiratory tract infections. Strains were mostly isolated from the sputum. The taxonomic breakdown of these strains was: Staphylococcus aureus (69 strains), Streptococcus pneumoniae (120), Haemophilus influenzae (170), Mucoid-producing Pseudomonas aeruginosa (42), Non-mucoid-producing P.aeruginosa (87), Escherichia coli (11), Klebsiella pneumoniae (35), Brahamella catarrharis (72), etc. Of these strains, 629 were used to determine MICs of various antibacterial agents and antibiotics for susceptibility analyses. Relationships between patient backgrounds and diagnoses and between infections diseases and causative organisms were also investigated. Most of the major causative organisms, such as H. influenzae and P. aeruginosa, showed no substantial changes from previous years, with regard to their sensitivities to antibiotic agent, but S. aureus, particularly methicillin/cephem-resistant strains of S. aureus (MCRSA) showed somewhat lower sensitivity to β-lactams and, as in recent years, to ofloxacin, a new quinolone drug, as well. Regarding background factors of patients, the age distribution was heavily concentrated in age brackets of 50 years and older, thus patients in these age group accounted for 75.2% of all the patients, which was comparable to 11.5% in 1985 and 11.9% in 1986. Among infections encountered, bacterial pneumonia was most frequent at 28.3%,followed by chronic bronchitis (21.2%) and bronchiectasis (16.0%). Bacterial pneumonia was actually the most frequent, throughout the entire age groups accounting for 34.3% of patients up to 29 years, 26.6% in the group of 30~69 years and 30.7% in patients aged 70 years and older. Chronic bronchitis was next most frequent and accounted for 20.0%, 26.4% and 30.7% among the three age groups, respectively. Breaking down clinical isolates by diagnosis, H. influenzae, S. pneumoniae and P. aeruginosa were isolated frequently from most of the infectious diseases. Among 331 strains isolated as causative organisms at during symptomatic periods of infection in bronchiectasis, chronic bronchitis and diffuse panbronchiolitis, H. influenzae, P. aeruginosa and S. pneumoniae were frequent, accounting for 29.6%, 23.9% and 16.6% of all the isolates, respectively. In bacterial pneumonia, S. aureus was frequently detected in addition to the above species. Chronologically, the frequency of H. influenzae has been declining year by year, while the frequency of S. pneumoniae has been steadily increasing. Among Gram-negative bacteria, B. catarrhalis is gradually gaining ground thus demanding our attention. Regarding the bacteria isolated before the first administration of antibacterial agents or antibiotics and the classification of the isolates by the duration of treatment, H. influenzae and S. pneumoniae were most frequent, accounting for 29.8% and 18.6%, respectively, but the incidence of both declined gradually in accordance with the duration of treatment. Conversely, the frequency of P. aeruginosa increased from 15.2% prior to administration to 39.0% on day 15 of treatment. This retrospective survey will be continued, taking into account new antibacterial and antibiotic agents that will be developed in the years to come.