The concept of indirect pathogenicity by beta-lactamase production, especially in ear, nose and throat infection.

A recent increase in numbers of beta-lactamase-producing strains of aerobic and anaerobic Gram-negative bacteria in upper respiratory tract infections has been associated with increased failure rates of penicillins in eradication of these infections. These organisms include Staphylococcus aureus, Haemophilus influenzae, Branhamella catarrhalis and Bacteroides spp. These infections include chronic otitis media, chronic sinusitis and mastoiditis, and chronic recurrent tonsillitis. The indirect pathogenicity of these organisms is apparent through their ability not only to survive penicillin therapy but also to protect penicillin-susceptible pathogens from these drugs. The direct and indirect virulence characteristics of these bacteria require the administration of appropriate antimicrobial therapy directed against all pathogens in mixed infections.