Using antibiotic concentrations in middle ear fluid to predict potential clinical efficacy

Background, The effectiveness of an antibiotic in eradicating an infection within an anatomic compartment is related to both its availability (penetration) and the susceptibility of the causative pathogen, Antimicrobial penetration can be assessed by measuring concentrations in serum or tissue, However, to assess antibiotic effectiveness in the treatment of otitis media, both antibiotic concentrations and pathogen profiles in middle ear fluid (MEF) should be considered, Tympanocentesis is required to access fluid in the middle ear compartment, This paper considers data on (MEF) antibiotic concentrations obtained with this procedure, Methods, Data on MEF antibiotic concentrations were considered in relation to the antibiotic susceptibility profiles of the more common otitis media pathogens, Results, Amoxicillin peaches MEF concentrations that exceed MICs for penicillin-susceptible and penicillin relatively resistant Streptococcus pneumoniae, but not for beta-lactamase-producing Haemophilus influenzae. Several betalactamase-stable drugs, e,g, cefixime and amoxicillin/clavulanate, however, achieve MEF concentrations that easily exceed their respective MIC(90)s for both beta-lactamase-producing and nonproducing H, influenzae but at ordinary doses may not exceed MIC(90)s for penicillin relatively resistant S, pneumoniae, Conclusion, Ongoing observation of organisms and their antibiotic resistance patterns in patients failing initial therapy of acute otitis media indicate that stability to beta-lactamase remains an essential quality for effective second line therapies, However, when possible tympanocentesis with culture is the ideal method of targeting specific therapy for patients failing multiple consecutive antibiotic regimens.