Susceptibilities of bacteria isolated from patients with respiratory infectious diseases to antibiotics (1991)

Isolated bacteria from respiratory tract infections were collected since 1981 in cooperation with institutions located throughout Japan, and have been investigated for their sensitivities to various antibacterial agents and antibiotics and reported by Ikemoto, et al. Relationships between these isolates and backgrounds of the patients were also studied each year. These results are discussed in detail in this report. In 20 institutions around the entire Japan from October 1991 to September 1992, 631 strains of bacteria were isolated mainly from sputa of 529 patients with respiratory tract infections and tentatively determined to be etiological agents. MICs of various antibacterial agents and antibiotics against 96 strains of Staphylococcus aureus, 112 strains of Streptococcus pneumoniae, 111 strains of Haemophilus influenzae, 114 strains of Pseudomonas aeruginosa (non-mucoid), 41 strains of Moraxella subgenus Branhamella catarrhalis, 39 strains of Pseudomonas aeruginosa (mucoid), Klebsiella pneumoniae and some others, were determined, and the drug sensitivities of these strains were determined except for the strains that had been killed during transportation. 1. S. aureus S. aureus strains for which MICs of methicillin were higher than 4 µg/ml (methicillin-resistant S. aureus) accounted for 58.3% and the frequency of the drug resistant bacteria increased over previous year's 42.5%. As shown by the MICs, arbekacin was active as vancomycin against all the strains on S. aureus. 2. S. pneumoniae Benzylpenicillin among the penicillins showed a potent activity against S. pneumoniae. Cefuzonam, cefmenoxime, cefozopran and cefotaxime among the cephems showed excellent antimicrobial activities against S. pneumoniae. Imipenem; a penem antibiotic, showed the most potent activity with MIC₈₀ of 0.03 µg/ml. 3. H. influenzae Activities of all drugs were excellent against H. influenzae strains tested. Ampicillin showed MIC₈₀ of 1 µg/ml against H. influenzae. Cefuzonam showed the most potent activity among cephems, it completely killed all bacteria at MIC 0.06 µg/ml. Cefotaxime and cefmenoxime showed next most potent activities with MIC₈₀s of 0.06 µg/ml. The antimicrobial activity of ofloxacin was equvalent to those of cephems. 4. P. aeruginosa (mucoid) Ciprofloxacin and tobramycin showed the most potent activities against P. aeruginosa (mucoid), and their MIC₈₀s were 4 µg/ml. 5. P. aeruginosa (non-mucoid) Similarly, ciprofloxacin and tobramycin showed the most potent activities against P. aeruginosa (non-mucoid) with MIC₈₀ of 2 µg/ml. Comparing to activities against P. aeruginosa (mucoid), all the drugs tested showed lower activities against P. aeruginosa (non-mucoid). 6. K. pneumoniae The activities of all drugs except for penicillins were very high against K. pneumoniae. Flomoxef and Cefixime showed the most potent activities and their MIC₈₀s were 0.06 µg/ml. 7. M.(B.) catarrhalis Imipenem; a penem antibiotic, showed the most potent activity against M.(B.) catarrhalis with MIC₈₀ of 0.06 µg/ml. Cephems, cefmetazole and cefotaxime, all showed MIC₈₀ of 1 µg/ml. Also, we investigated annual changes in the background of patients. Types of respiratory infectious diseases, and their etiological bacteria were also studied. As for the patients backgrounds, many infectious diseases were found in patients in the high age bracket, and the patients over age of 60 accounted for 64.9% of the diseases. As for the distribution by respiratory tract infections, chronic bronchitis and bacterial pneumonia accounted for the greatest numbers of cases with 37.2%, 32.1%, respectively, followed by bronchiectasis at 9.5%. As for the frequency of etiologic bacteria by respiratory tract infections, S. pneumoniae (23.5%), and H. influenzae (20.5%) were the most frequent in chronic bronchitis, and S. aureus (19.9%) and P. aeruginosa non-mucoid type (19.4%) in bacterial pneumonia. Regarding effects of administration of antibiotics and isolates obtained on the day after infection, those bacteria that were isolated before antibiotics administration but decreased upon administration included S. pneumoniae, H. influenzae and M.(B.) catarrhalis. Frequencies of S. aureus and P. aeruginosa (mucoid and non-mucoid), however, increased after administration of antibiotics.