Prevalence of Moraxella catarrhalis infections of the lower respiratory tract in elderly patients.

Objectives: To determine: • rate of isolation of Moraxella catarrhalis in elderly patients having lower respiratory tract infection • The antibiotic susceptibility pattern of Moraxella catarrhalis isolates. • The predisposing factors responsible for Moraxella catarrhalis infections of lower respiratory tract. Material and Method: This is a prospective study carried out at Manipal Teaching Hospital, Pokhara during May 2002 to April 2003. A total of 716 sputum samples collected from patients with suspected lower respiratory tract infection were investigated. The samples were subjected to Gram stain, culture and sensitivity. Sputum samples were inoculated on blood and chocolate agar and incubated at 37 0 C for 18 to 24 hours in candle jar containing 3-5% Co2. For the identification of bacterial isolates, the cultural and colonial characteristics were recorded and identified with the use of biochemical test. The susceptibility of bacterial isolates to antimicrobial agent was performed following Kirby-Bauer method. Result: Out of the 716 samples, 355 (49.58%) grew normal commensals of the upper respiratory tract. Respiratory pathogens were recovered from 361 (50.41%) samples. The most common respiratory pathogen was H. influenzae (26. 86%), followed by S. pneumoniae (21.16%). Moraxella catarrhalis accounted for 6.90%. Rate of isolation of Moraxella catarrhalis was higher in males than in females. Out of 25 isolates 16 were from males and 9 were from females. Frequency of isolation of Moraxella catarrhalis was more frequently seen in age group 61-70 years. It was most commonly recovered in winter. The most effective antibiotics were amoxicillin-clavulanate and ceftriaxone and least was ampicillin. Conclusion: Moraxella catarrhalis isolation from sputum especially in persons above 60 years of age and in the absence of other well established pathogens should not be disregarded as they can cause lower respiratory tract infection in these individuals.