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Antibiotics
Tamar Barlam
Infectious Disease
Director, Antimicrobial
Stewardship
Why is antibiotic choice
important?
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Safe, broad-spectrum antibiotics are readily
available
One can easily cover most common
infections with excellent therapeutic results
So what’s the big deal?
A Changing Landscape for
Numbers of Approved Antibacterial Agents
16
14
12
Resistance
Number of agents approved
18
10
8
6
4
2
0
0
1983-87
1988-92
1993-97
1998-02
2003-05
2008
Bars represent number of new antimicrobial agents approved by the FDA during the period listed.
Infectious Diseases Society of America. Bad Bugs, No Drugs. July 2004; Spellberg B et al. Clin Infect Dis. 2004;38:1279-1286;
New antimicrobial agents. Antimicrob Agents Chemother. 2006;50:1912
Between 1962 and 2000, no major
classes of antibiotics were introduced
Fischbach MA and Walsh CT Science 2009
Antibiotic Resistance
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Antimicrobial-resistant infections can cause worse
patient outcomes, longer hospital stays, and higher
mortality rates than similar infections with antibioticsusceptible bacteria.
Total costs related to AR infections are estimated as
high as $30 billion.
Inappropriate antibiotic use is believed to be the
major contributor to the development and spread of
AR bacteria.
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Studies have demonstrated approximately 30 to 50% of
antibiotic treatments are inappropriate.
Campaign to Prevent Antimicrobial Resistance in Healthcare Settings
Selection for antimicrobialresistant Strains
Resistant Strains
Rare
Antimicrobial
Exposure
Resistant Strains
Dominant
Choosing an Antibiotic
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What is wrong with the patient?
Is it an infection?
Is it bacterial?
How sick is the patient?
Host factors that might influence likely
pathogens: social history, age, residence,
comorbid conditions
Host factors that might influence drug choice:
allergy, pregnancy, renal/liver function
Attributes of the drug
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What is its spectrum?
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Gram positive or gram negative?
Aerobic or anaerobic or both?
Does it reach adequate levels at site of
infection?
Bacteriostatic or bacteriocidal?
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Endocarditis
Meningitis
Osteomyelitis
How are they different?
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Cefazolin
Ceftriaxone
Cefepime
Ampicillin-sulbactam
Ertapenem
Levofloxacin
Ciprofloxacin
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Ceftriaxone
Cefepime
Piperacillin-tazobactam
Piperacillin-tazobactam
Meropenem
Ciprofloxacin
Cefepime
Case #1
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54 yo female with poorly controlled diabetes
comes to the ED with a buttock abscess with
surrounding erythema. The abscess was
I&D’d and material sent for culture.
Case #1
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Patient was placed on clindamycin and
discharged home.
Case #1
Case #1
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Inducible macrolide resistance.
Encoded by plasmid-borne
gene erm.
Constitutive – all test resistant
Inducible – clindamycin can
test susceptible
Bacteria Isolated from Culture of Abscess Material, Deep Tissue Specimens, or Blood.
Jenkins T C et al. Clin Infect Dis. 2010;51:895-903
© 2010 by the Infectious Diseases Society of America
Case #2
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23 yo healthy male with tibial fracture after
MVA. ORIF performed and patient was
discharged after an uneventful hospital
course. Pain persisted and after six weeks,
there was complete non-union. One month
later, a small pustule formed and drained
purulent material. Patient was seen by ortho
and taken back to OR.
What is the patient’s diagnosis?
Treatment?
Case #2
Case #2
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What if these were the culture results?
Case #3
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47 yo active IVDU, HCV positive, presents
with severe left arm pain and swelling. The
patient had injected heroin into the veins of
that arm 1 day prior.
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On the morning of admission, he had severe
bilateral pleuritic chest pain
Case #3
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Rest of exam: T103 Other VSS
II/VI SEM at LSB, decreased breath sounds
R>L base, rales bilaterally
No HSM
WBC 18,000 w/ 26% B; H/H 13/40, plts 300K
other labs wnl
Case #3
Case #3
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Describe what the patient likely has.
What would you do next?
Antibiotics?
Case #3
Case #3
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Antibiotic?
Duration?
Case #3
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What if patient if this was his isolate: