Antibiotic Overuse – how much does it matter?
Thursday 1/17/08
Spread of resistance
Antibiotic pressure
Human to human transmission
Mechanisms by which Antibiotic use can induce resistance
Lipsitch & Samore EID 2002
Antibiotic selection of resistant mutants
Ab treatment => outgrowth of resistant subpopulations or acquire de novo resistance
Antibiotic pressure => increased load or resistant bacteria
By eradicating a susceptible strain making the host more susceptible to new acquisition of
strains
Indirect effect – reduced transmission of susceptible strains to other susceptible hosts
Antibiotics are drugs with externalities (like pollutants)
• By treating an individual with antibiotics – other individuals in the society are influenced
• Antibiotic treatment – maybe beneficial for an individual but deleterious for society.
Types of studies that examine the relationship between Ab use and Ab
resistance• Ecological studies
• Individual level studies– Case-control– Quasi-experimental studies– Longitudinal studies
• Mathematical models
Total Ab use in 26 European countries in 2002/ Goosens et al. Lancet 2005
Total Ab use in 2004 / Goosens CID 2007
Correlation between Pen use and PRSP / Goosens et al. Lancet 2005
Do all antibiotic classes induce resistance similarly? The pneumococcus paradigm / Dagan et
al. PIDJ 2006
Antibiotic use as a risk factor for MRSA (in ED) / Moran et al. NEJM 2006
Antibiotic consumption and MRSA, an ecologic study (EID 2004)
FQ use and FQ-R MRSA and E. coli (community and HA)/ MacDougall et al. CID 2005
Is there overuse/non-judicious use of antibiotics?
• ~50% of Ab prescriptions are non-judicious
• What is non-judicious use?– Ab for viral infections– Wrong dose– Wrong duration– Wrong Ab class – Broad ab class when narrow is as good
Why is there non-judicious use?
• Lack of knowledge
• Patient demand
• Uncertainty (of Dx, of risks and benefits)
• Medico-legal issues – fear from lawsuit
• Low awareness to Ab resistance problem
Effect of antibiotic use in agriculture
• Over 50% of Ab produced in US are used for agricultural purposes
• Use for growth promotion and treatment of food animals
• FQ used to treat chicken:– Identical strains of FQ-R Campylobacter found in
raw chicken as those in humans
Agriculture use and Ab resistance: Quantifying the effect
• Animal use can be a selective force responsible for the assembly of resistant gene clusters
• Reservoir for resistance-encoding plasmids (or other genetic elements) in animal commensal bacteria
• Bacteria that are shared by food animals and humans (VRE).
Is it not too late?
• Regulation now may have little or no effect.
• Waiting for conclusive evidence may result in a missed opportunity to prevent damage!