principles of infectious disease

�Principles of Infectious Disease�

Dr. Ezra Levy

CSU+6 06PA Program

I. Microbiology

(1) morphology (e.g., cocci, bacilli)

(2) growth characteristics (e.g., aerobic vs anaerobic)

(3) other qualities (e.g., Gram’s stain positive or Gram’s stain negative)

Choice of Antimicrobial

Therapy

•  based on the morphology and growth patterns of microorganisms

II. Empirical Therapy

•  empirical therapy is often based on a working knowledge of the most likely pathogens expected to be found at the site of infection

•  certain organisms are predictably associated with infection at certain tissue sites and not in others

•  certain host factors such as age, immunosuppression, prior antibiotic usage, and environment help to predict the most likely organism

II. Empirical Therapy (cont.)

III. Selection of an Antimicrobial Agent

•  selection of an antimicrobial agent for some infections can await the results of

appropriate culture and susceptibility (C & S) testing

III. Selection of an Antimicrobial Agent (cont.)

C & S Testing

III. Selection of an Antimicrobial Agent (cont.)

ANTIMICROBIAL MECHANISMS OF ACTION

Treatment of Uncomplicated UTI (Outpatient)

Pathogens E. Coli Proteus mirabilis Klebsiella pneumoniae Enterococcus faecalis Staph saprophyticus

Oral Antibiotic(s) of Choice Bactrim DS / Septra DS Sulfamethoxazole / Trimethoprim OR: 1st general CEPH e.g., cephalexin (Keflex) OR: Fluoroquinolone e.g., Ciprofloxacin (Cipro) or Levofloxacin (Levaquin)

Complicated UTI (ESBL pathogens) meropenem (Merrem) 500 mg IV Q6H ertepenem (Invanz) 1 gm IV/IM Q24H

FloroquinoloneAdverse Effectsa tendonitis myalgiab QT interval prolongation

Treatment of Pyelonephritis (Inpatient)

Pathogens E. Coli Klebsiella pneumoniae Enterobacter sp. Pseudomonas aeruginosa

Oral Antibiotic(s) of Choice Ceftriaxone (Rocephin) 1 GM IV Q24H OR: Ciprofloxacin 400 mg IV Q12H*

Levofloxacin 500 mg IV/PO Q24H OR: AGLY**: Gentamicin / Tobramycin

5 – 7 mg/kg/day IV once daily

* Ciprofloxacin 500 mg PO BID

** AGLY = aminoglycoside

Y

CAGLY AdverseEffects

1 nephrotoxicity2 ototoxicity

Tx of Community-Acquired Pneumonia (Inpatient)

Pathogens S. pneumoniae (12 - 68%)

H. influenza (2.5 - 45%)

Mycoplasma pneumoniae Chlamydia pneumoniae Legionella species

Antimicrobial Drug(s) of Choice Ceftriaxone 1 GM IVPB Q24H

PLUS Azithromycin 500 mg IVPB 24H

OR Levofloxacin 500-750 mg IVPB Q24H

a ae

can be switchedto Po outpatient Rx

AzithromycinAdverse Effectprolongs QT interval

Tx of Hospital (Nosocomial) Acquired Pneumonia (HAP)

Pathogens Staphylococcus aureus Klebsiella pneumoniae E. Coli Psuedomonas aeruginosa

Antibiotic(s) of Choice Vancomycin 15 mg/kg/dose IV Q12H

AND

Cefepime 2 GM IVPB Q8H OR Ceftazidime 2 GM IVPB Q8H OR Zosyn (Piperacillin-Tazobactam) 4.5 GM IVPB Q6H

OR Levofloxacin 500 MG IVPB Q24H

Ceftazidime (Fortaz), Cefepime (Maxipime), Levofloxacin (Levaquin), clindamycin (Cleocin)

Aspiration Pneumonia ! ! ! ADD: Clindamycin 600 mg IVPB Q8H

j

covers anaerobes G bugs

Treatment of Meningitis (Community-Acquired)

Pathogens Streptococcus pneumoniae (pneumococcus) Neisseria meningitidis (meningococcus)

Antibiotics of Choice Ceftriaxone 2 GM IV Q12H

PLUS Vancomycin 15 mg/kg IV Q8H

PLUS Acyclovir 10 mg/kg/dose IV Q8H

Ceftriaxone (Rocephin), Acyclovir (Zovirax)

higherdosesto penetratemeninges

Vancomycin AdverseEffects added to cover17nephrotoxicityca ototoxicity viral meningitis

pending Cx results

Treatment of Intra-Abdominal Sepsis (e.g., Peritonitis, Cholecystitis)

Pathogens Gram-negative bacteria Streptococci, anaerobic bacteria: Clostridium sp. Bacteroides sp.

Antibiotics of Choice Zosyn (Piperacillin-Tazobactram) 4.5 GM IV Q6H OR Ertapenem (Primaxin)

1 GM IV Q24H

G 0 enteric bugslAnaerobesrose

Treatment Helicobacter pylori (H. pylori)

PrevPac ! Lansoprazole (Prevacid) 30 mg PO BID x 10 days ! Amoxicillin (Amoxil) 1000 mg PO BID x 10 days ! Clarithromycin (Biaxin) 500 mg PO BID x 10 days

Treatment of Cellulitis / Osteomyelitis Cellulitis ! Cephalexin (Keflex) 500 mg PO QID, AND

! SMX-TMP (Bactrim DS) PO BID Osteomyelitis ! Vancomycin 15 mg/kg/dose IV Q12H, AND

! Clindamycin 600 mg IV Q8H

f Staphepidermitis

MRSA

MRSAanaerobes