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Evaluation of Acinetobacter Infection
Sarah Nelson, Pharm.D.Pharmacy Practice Resident
Acinetobacter• Non-fermenting, non-motile, aerobic gram
negative coccobacilli
• Isolated from soil, water, animals, and humans
• Colonizes on inanimate objects with high stability
•Ventilators, mattresses, pillows, bed rails, urine collection jugs, IV equipment, nebulizers, etc.Giamarellou, H. et al. Acinetobacter baumannii: a universal threat to public health?
International Journal of Antimicrobial Agents.2008;32:106-119
Clinical Manifestations
•Pulmonary
•Bacteremia
•Skin & skin structure infections
•Urinary tract infections
•Post surgical meningitis
Giamarellou, H. et al. Acinetobacter baumannii: a universal threat to public health? International Journal of Antimicrobial Agents.2008;32:106-119
Mechanisms of Resistance
Munoz-Price, L. et al. Acinetobacter Infection. N Engl J Med. 2008;358(12):1271-81
Current Treatment Options
•Sulbactam based β-lactams
•Carbapenems
•Tigecycline
•Colistin
Background• 29 critically ill patients with pneumonia or
bacteremia causes by MDR Acinetobacter baumanii– Treatment: IV Colistin (2 million IU three times
daily) PLUS IV rifampicin (10mg/kg every 12 hours)
– Mean duration of treatment: 17.6 days (+/- 10.4)
– Clinical & microbiological response: 76% (22 pts)
– Infection-related mortality: 21% (6 pts)– Nephrotoxicity: 10% (3 pts)
Colistin and rifampicin in the treatment of multidrug-resistant Acinetobacter baumannii infections. J Antimicrob Chemother. 2008;61(2):417-420
Background
Kwon, KT et al. Impact of imipenem resistance on mortality in patients with Acinetobacter bacteremia. J antimicrob Chemother. 2007;59:525-530
• Higher 30 day mortality with:
• MDR strain of Acinetobacter caused infection (57.5% vs. 27.5%)
• Inappropriate empiric treatment was utilized (60% vs. 20%)
Objectives
• Characterize the extent of Acinetobacter infection at VCUHS
• Identify common treatment regimens currently utilized at VCUHS
• Delineate adverse effects associated with the most utilized treatment regimens
• Provide education regarding selection of treatment regimen if deemed necessary
Methods
• Retrospective– July 1, 2007- July 31, 2008
• Quality Improvement Project
• IRB Approval, expedited
Patients
• Inclusion Criteria– Adults (≥18 years of age)– ≥ 1 positive culture of Acinetobacter
calcoaceticus-baumannii complex– Received antimicrobial treatment for ≥ 2
days
• Exculsion Criteria– Infection with other species of Acinetobacter
•A. lwoffii•Undifferentiated specimens
Data Collection
• Demographics
• Specimen information•Source, sensitivities
• Antimicrobial Therapy•Empiric & final drug therapy
• Adverse Reactions•Serum Creatinine & BUN
Data Collection• Efficacy Outcomes
– Favorable vs. unfavorable response•Favorable:
– Signs & symptoms resolved within 48 hours of end of therapy
– Negative repeat culture
•Unfavorable:– Signs & symptoms persisted >48
hours after therapy ended– Required additional antibiotic therapy– Positive repeat culture
Statistical Analyses
• Descriptive statistics were used to describe variables
• Chi-squared test was used to identify significant outcomes
• Logistic regression was used to determine independent risk factors for favorable outcomes
Study Subjects
• 207 patients with ≥ 1 positive culture for Acinetobacter calcoaceticus-baumannii complex– 83 patients excluded
•Other species•<18 years old•Outpatients•23 hour observation
– 12 charts not available
• 112 patients included in study
Demographics
Overall
(n=112)Favorable
Outcome (n=76)Unfavorable
Outcome (n= 34)
Male 59 (53%) 38 (50%) 20 (59%)
Age (years) 52.6 51.4 57.1
LOS (days) 28.5 27.5 32
Days to positive culture
2.5 2.5 2.6
>1 source of Acinetobacter
22 (20%)
Source of Infection
0
10
20
30
40
50
Blood Urine Respiratory Wound Other
Locality of Infection
MRICU
Surgery/Trauma
NSICU
CTSICUBURN
General Medicine
SurgeryOncology
OrthoRehab Other
0
5
10
15
20
25
30MRICU BURN Ortho
Rates of ResistanceAntimicrobial 2007
AntibiogramStudy Group
Amikacin --- 72%
Cefepime 60% 74%
Ciprofloxacin 65% 76%
Gentamicin 58% 68%
Imipenem 31% 56%
TMP/SMX 50% 64%
Piperacillin/Tazobactam
48% 70%
Tigecycline --- 31%
Colistin --- 0%
Empiric Therapy• Appropriate empiric therapy is associated with a
favorable outcome (p<0.0001)
• 29 patients (26%) were treated with appropriate empiric therapy– 28 (97%) had a favorable outcome
• Inappropriate empiric therapy accounts for 33 of the 34 unfavorable outcomes (97%)
• 17% of patients were not started on empiric antimicrobial therapy
Tailored Antimicrobial Therapy
• Appropriate tailored therapy is associated with a favorable outcome (p<0.0001)
• 79 (72%) patients were treated with appropriate antimicrobial therapy– 65 (82%) patients had a favorable outcome
• Average duration of tailored antimicrobial therapy was 12.4 days
• Most common final antimicrobial therapy included imipenem (18), colistin (17), tigecycline (12), & piperacillin/tazobactam (10)– 14 patients were treated with combination therapy
Colistin
• 17 patients were treated with colistin– Never used as empiric therapy– Used as monotherapy in 9 (53%) patients– Most commonly used with tigecycline for
combination therapy
• Intravenous route most common; inhalation also utilized for respiratory infections
• 3 (18%) patients experienced an increase in serum creatinine & 4 (25%) patients experienced an increase in BUN
Limitations
• Retrospective analysis– Documentation of assessment and plan
• Evaluation of only Acinetobacter calcoaceticus-baumannii complex
• Withdrawl of care promoted an unfavorable endpoint
Conclusion
• Selection of correct empiric antimicrobial therapy is necessary for a favorable outcome
• No independent risk factors exist that demonstrate a favorable outcome
• Nosocomial strains of Acinetobacter calcoaceticus-baumannii complex exhibit increased resistance to common antimicrobials
• Colistin is an effective and safe antimicrobial with 100% susceptibility to the MDR Acinetobacter baumanii-calcoaceticus complex
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