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We tested 53 clinical isolates of Branhamella catarrhalis recovered from patients with respiratory symptoms to determine the susceptibility of the isolates to 25 antimicrobial agents, including the newer I8-lactam antibiotics. Of the 53 strains, 46 (86.7%) were P-lactamase producers. All the strains were susceptible to the majority of the new penicillins and cephalosporins.-The combinations of amoxacillin-clavulanic acid and ticarcillin-clavulanic acid were also very active against the P-lactamase-prodiicing strains.Branhamella catarrhalis, formerly known as Neisseria catarrhalis, is generally considered a harmless oropharyngeal commensal bacterium. However, in the past few years it has been recognized as the etiologic agent of otitis media in children (9) and has been isolated in pure culture from patients with acute bronchitis and pneumonia (2,7,10,12,16,17), acute laryngitis (15), acute sinusitis (1), septicemia (3), meningitis (3, 13), and endocarditis (6, 14). P-Lactamase production by B. catarrhalis has occurred in 4 to 100% of isolates (5, 7-9, 16). Despite this fact, very little information is available on the susceptibility of B. catarrhalis to antimicrobial agents, especially the newer 1B-lactam antibiotics.We report here on the antimicrobial susceptibility and the incidence of 1-lactamase in 53 clinical isolates of B. catarrhalis from hospitalized patients with respiratory disease. Organisms. A total of 53 clinical isolates of B. catarrhalis were obtained from hospitalized patients with lower respiratory symptoms admitted to the Veterans Administration Medical Center, Johnson City, Tenn. The isolates were obtained from blood, transtracheal aspirates, and expectorated sputum from patients with pneumonia or acute exacerbation of chronic bronchitis. The clinical isolates were identified by conventional methods previously described (4): gram-negative diplococci, oxidase production, growth on 5% sheep blood agar incubated at 37°C under humidified 10% C02, lack of pigmentation, failure to produce acid from glucose, maltose, and sucrose, and reduction of nitrate to nitrite. P-Lactamase production. The production of ,B-lactamase was determined in each strain by the use of the chromogenic cephalosporin disk nitrocefin (Cefinase; BBL Microbiology Systems, Cockeysville, Md.).Antibiotics. Antibiotics were kindly provided by the manufacturers as reagent-grade powders and included penicillin

Isolates of Branhamela catarrhalis from 13 patients with pneumonia, 6 patients with tracheobronchitis, and 8 patients who were colonized with the organism were studied with respect to susceptibility to the bactericidal action of normal human serum (NHS), glass slide hemagglutination (HA) of group O human erythrocytes, (P-lactamase production, and susceptibility to selected antimicrobial agents and laboratory drugs. A total of 18 of 27 isolates were serum resistant, 22 of 27 produced HA, and 21 of 27 were P-lactamase positive. Statistically significant correlations were found between susceptibility to NHS and susceptibility to trypsin (r = +0.47; P = 0.01) and between susceptibility to NHS and HA (r =-0.48; P = 0.009). Significant correlations were also observed among several pairs of antimicrobial drugs. Analysis of variance showed that mean ampicillin MICs correlated with isolate group (r =-0.49; P = 0.03) in that the pneumonia isolates had higher MICs. Some phenotypic characteristics appeared to be independent of each other. These data suggest that important differences exist among clinically significant B. catarrhalis strains and that these differences may be due to differences in the cell wall envelope of the organism. * Corresponding author. 903 '.w,~t 'a "~~~~0 O FIG. 1. B. catarrhalis ATCC 25238 after growth for 4 h in Muller-Hinton broth with shaking; one drop was air dried and stained with crystal violet. Bacterial aggregates of different sizes are shown. Magnification, x935.

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A selective medium with DNase test agar and incorporating vancomycin (10 ,ug/ml), trimethoprim (8 ,ug/ml), and amphotericin B (2 ,ig/ml) supported the growth of 305 Branhamella catarrhalis isolates. A modified toluidine blue O technique was used after 48 h of incubation in C02 to overlay suspected B. catarrhalis colonies. A metachromatic color change was observed in 15 min, indicating DNase production. In 200 unselected sputum samples of hospitalized patients, this method was compared with routine microbiologic procedures; 31 B. catarrhalis isolates were recovered with the method, compared with 22 isolated from the clinical laboratory.