tigecycline is a drug, with few, if any side effects, the dose may be increased without adverse
effects if administered in sufficient volume and if givenslowlyintravenously. For MDR
Klebsiellaurosepsis/UTI, “high dose” tigecycline has been successfully used. Tigecycline may
be given in “high dose” as 400 mg (IV)one dose followed by 200 mg q24h. Since urinary
levels of tigecycline are*25% of simultaneous serum levels, higher serum concentrations
result in higher urine concentrations thatmaybe effective against MDRK. pneumoniaeurinary
isolates with relatively high MICs. For the oral antibiotic therapy ofK. pneumoniaeCAB,
fosfomycin is usually effective after urinary catheter removal/replacement (6,19,20).
MDR A. baumannii
Epidemiologic Considerations
A. baumanniiare skin organisms that also thrive in aqueous environments.A. baumanniiare
organisms of low virulence with minimal invasive potential. For these reasons,A. baumannii
commonly colonize but may infect patients in the CCU. Common sites of colonization are
respiratory secretions and urine (21–24).
A. baumannii Infections
As withP. aeruginosa, A. baumanniicolonization of respiratory secretions in ventilated patients
is often a diagnostic consideration.A. baumanniiinfections are a rare cause of NP.Acinetobacter
baumanniiNP occurs most commonly in clusters or outbreaks in the CCU (4,5).Acinetobacter
colonization of aqueous solutions in respiratory support equipment is usually responsible for
A. baumanniioutbreaks of NP. IsolatedA. baumanniiNP is distinctly unusual. Clinicians must
be careful to distinguish as withP. aeruginosathe clinical significance ofA. baumanniiin
respiratory secretions of ventilated patients with fever, leukocytosis, and pulmonary infiltrates.
In excluding outbreaks, nearly alwaysAcinetobacterisolates recover from respiratory secretions,
represent colonization rather than infection indicative ofA. baumanniiNP, and should not be
“covered” with antimicrobial therapy (7,10).A. baumanniicommonly colonize the skin and
expectedlyA. baumanniiis occasionally are implicated in central IV line infections.
Antibiotic Therapy of A. baumannii Infections
A. baumannii, unlike P. aeruginosaand K. pneumoniae, has, by definition always been a
MDR GNB. There have always been fewer antibiotics effective againstAcinetobacterthan
P. aeruginosaorK. pneumoniae. Few strains ofA. baumanniiare susceptible to third-generation
cephalosporins or cefepime. Some strains ofA. baumanniiare susceptible to meropenem or
ertapenem. The most commonAcinetobacterinfection encountered in the CCU are CVC
infections and CAB. The primary therapeutic intervention in treating CVC infections,
regardless of the infecting organism, is removal or replacement. It cannot be emphasized
too strongly that antibiotics will not be effective even if reported as susceptible without CVC
removal. Similarly for CAB, removal/replacement of the urinary catheter is the key
therapeutic intervention without which antibiotics will rarely be effective in eradicating the
bacteriuria (6,10).
For MDRA. baumanniicentral venous catheter (CVC) infections, meropenem, ampicillin,
sulbactam, and tigecycline have been effective. The optimal antibiotics for MDRA. baumannii
in this setting are ampicillin/sulbactam in penicillin-allergic patients, or meropenem or
doripenem may be useful. Nearly all isolates remain susceptible to colistin or polymyxin B. For
CAB due to pan-resistantA. baumannii,fosfomycin is often the only oral antibiotic that may be
effective after urinary catheter removal/replacement.
The antibiotic resistance concerns are intimately connected with the development of
MDR GNBs that are common colonizers and infrequent pathogens in the CCU. The first
consideration is not to cause or worsen resistance in the CCU by the use of high-resistance
potential antibiotics for overzealous empiric therapy particularly of NP. The second important
consideration is to eliminate an existing resistance problem due to MDR GNBs. This is best
achieved by formulary substitutions involving the replacement of high-resistance potential
antibiotics with those of low resistance potential that are effective against the MDR strain
problematic to the CCU/institution, i.e.,P. aeruginosa,K. pneumoniae,orA. baumannii(1,2). This
Antibiotic Therapy of MDRP. aeruginosa, K. pneumoniae, andA. baumanniiin CCU 517