Download Management of Acinetobacter baumannii Reviewed CME

Management of Acinetobacter baumannii Reviewed CME
News Author: Laurie Barclay, MD
CME Author: Laurie Barclay, MD
Complete author affiliations and disclosures, and other CME information, are available
at the end of this activity.
Release Date: November 19, 2008; Valid for credit through November 19, 2009
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Learning Objectives
Upon completion of this activity, participants will be able to:
1. Describe characteristics of and general control measures for Acinetobacter
baumannii infection.
2. Describe antibiotic treatment of Acinetobacter baumannii infection.
Authors and Disclosures
Laurie Barclay, MD
Disclosure: Laurie Barclay, MD, has disclosed no relevant financial relationships.
Brande Nicole Martin
Disclosure: Brande Nicole Martin has disclosed no relevant financial information.
November 19, 2008 — Current strategies for control and treatment of Acinetobacter
baumannii, an antimicrobial drug-resistant infection that occurs in many critically ill
hospitalized patients, are reviewed in the December issue of Lancet Infectious
Diseases.
"The reported incidence of A baumannii infections has substantially increased during
the past decades," write Drosos E. Karageorgopoulos, MD, and Matthew E. Falagas,
MD, from the Alfa Institute of Biomedical Sciences in Athens, Greece. "This increase
could be attributed to a rise in the proportion of the susceptible population as a result
of advancements in medical support of critically ill and frail patients. A substantial
increase in the rates of antibiotic resistance of A baumannii has also been documented
during the past decades."
Environmental sources of A baumannii include soil and foods such as vegetables, meat,
and fish. In healthy humans, skin colonization may occur at a low density and for a
short time, but colonization of the throat, nares, and intestinal tract is rare.
Infections with A baumannii most often occur in critically ill hospitalized patients,
especially those with advanced age, serious underlying diseases, immunosuppression,
major trauma, or burn injuries. Other risk factors are invasive procedures, indwelling
catheters, mechanical ventilatory support, extended hospital stay, and previous
antibiotic administration.
Major clinical syndromes caused by A baumannii infections include pneumonia;
bacteremia; surgical site infection; skin and soft tissue infection; urinary tract infection;
secondary meningitis, particularly in patients with ventricular draining tubes; and
peritonitis in patients undergoing peritoneal dialysis.
Community-acquired A baumannii pneumonia, which is typically severe, occurs
primarily in southeast Asia and tropical Australia in patients with underlying chronic
obstructive pulmonary disease, renal failure, diabetes mellitus, or heavy consumption
of tobacco or alcohol. Wound infections may also occur in patients who have
experienced mass destruction or war conflicts.
Institutional outbreaks of antimicrobial drug–resistant A baumannii are posing an
increasing threat to public health, with the often complex epidemiology of these
outbreaks hindering adequate infection control.
Potential common sources of the outbreak may include contaminated environmental
sites and medical equipment as well as healthcare personnel with skin colonization.
Implementing specific control measures can be facilitated by identifying potential
common sources of an outbreak with surveillance cultures and epidemiologic typing
studies.
To contain an outbreak of A baumannii, appropriate administrative guidance and
support, as well as strict compliance with a series of infection control techniques, are
required. These include environmental cleaning, adequately sterilizing reusable
medical equipment, practicing effective hand hygiene, and using contact precautions.
Ventilator-associated pneumonia, bloodstream infections, and other infections with A
baumannii mandate effective antibiotic treatment. Currently available antimicrobial
classes and agents potentially effective against A baumannii include sulbactam;
antipseudomonal penicillins, cephalosporins, and carbapenems; monobactams,
aminoglycosides, fluoroquinolones, tetracyclines, glycylcyclines, and polymyxins.
High and increasing resistance rates of A baumannii to many of these agents limit the
choice of appropriate antimicrobial therapy. Microbiological surveillance trials have
reported rates of multidrug resistance in A baumannii of approximately 30%, but there
are geographic differences in resistance patterns.
Frequently encountered mechanisms of antimicrobial resistance of this bacterium
include production of β lactamases, efflux pumps, reduced permeability of the outer
membrane, mutations in antibiotic targets (eg, for quinolones), and production of
enzymes inactivating aminoglycosides.
Knowledge concerning the efficacy of various therapeutic options is primarily derived
from retrospective studies or from small, nonrandomized, prospective studies.
Although carbapenems have long been considered to be first-line therapeutic agents
of choice, resistance rates in some areas have dramatically increased.
Serious A baumannii infections have previously responded to sulbactam, but the
efficacy of this drug is decreasing against carbapenem-resistant isolates. Clinical data,
mostly derived from small-sized studies showing favorable clinical outcomes, indicate
reliable antimicrobial activity of polymyxins against extensively drug-resistant isolates
of A baumannii and reduce earlier concerns regarding toxicity.
Preclinical evidence suggests that minocycline, and especially its derivative, tigecycline,
are highly effective against A baumannii. However, clinical trials are lacking. Further
research is therefore needed to elucidate several issues regarding the best therapeutic
options for multidrug-resistant A baumannii infections.
"The role of A baumannii as a pathogen causing serious infections in critically ill
patients has become increasingly clear," Drs. Karageorgopoulos and Falagas conclude.
"Measures to address specific modes of transmission identified during an outbreak and
strict adherence to a variety of infection control measures are typically required for
the containment of an outbreak. Treatment options against multidrug-resistant A
baumannii infections seem to be limited."
Dr. Falagas has received speaker fees from Wyeth, AstraZeneca, Merck, Cipla, and
Grunenthal. Dr. Karageorgopoulos has disclosed no relevant financial relationships.
Lancet Infect Dis. 2008;8:751-762.
Learning Objectives for This Educational Activity
Upon completion of this activity, participants will be able to:
1. Describe characteristics of and general control measures for Acinetobacter
baumannii infection.
2. Describe antibiotic treatment of Acinetobacter baumannii infection.
Clinical Context
Infections with A baumannii are on the rise, especially in hospital settings in critically ill
patients, in part attributed to the ability of this organism to cause outbreaks.
Acinetobacter species may survive for 1 to 5 months on dry, inanimate surfaces, and A
baumannii has several mechanisms enhancing its ability to colonize patients or
equipment used in medical care.
One of the most important factors allowing persistence of Acinetobacter infections in
healthcare settings is resistance to antimicrobial agents. Although several classes of
antibiotics are potentially effective against A baumannii, increasing multidrug
resistance is a growing problem.
Study Highlights
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A baumannii infections usually occur in critically ill hospitalized patients.
Risk factors include advanced age, serious underlying diseases,
immunosuppression, major trauma, burn injuries, invasive procedures,
indwelling catheters, mechanical ventilation, prolonged hospital stay, and
recent antibiotic use.
Clinical syndromes include pneumonia; bacteremia; and infections of surgical
sites, skin and soft tissue, and the urinary tract.
Secondary meningitis may occur in patients with ventricular draining tubes.
Patients undergoing peritoneal dialysis may acquire A baumannii peritonitis.
Institutional outbreaks of antimicrobial drug–resistant A baumannii pose a
growing threat to public health. These outbreaks usually stem from
contaminated environmental sites and medical equipment, or healthcare
personnel with skin colonization.
Surveillance cultures and epidemiologic typing studies can help identify
potential common sources and institute appropriate control measures.
Useful infection-control techniques include environmental cleaning, adequately
sterilizing reusable medical equipment, effective hand hygiene, and contact
precautions.
Currently available antimicrobials potentially effective against A baumannii
include sulbactam; antipseudomonal penicillins, cephalosporins, and
carbapenems; monobactams; aminoglycosides; fluoroquinolones; tetracyclines;
glycylcyclines; and polymyxins.
Resistance rates of A baumannii to many of these agents are high
(approximately 30%) and are increasing, limiting effective treatment options.
Carbapenems were initially thought to be therapeutic agents of choice for A
baumannii, but resistance rates in some areas have dramatically increased.
Because of resistance, sulbactam is not as effective against A baumannii as it
had been, according to previous research studies.
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Polymyxins appear to be effective against extensively drug-resistant isolates of
A baumannii and are not as toxic as previously thought.
Preclinical evidence suggests that minocycline and tigecycline are highly
effective against A baumannii, but clinical trials are lacking.
Further research is therefore needed to determine the best therapeutic options
for multidrug-resistant A baumannii infections.
Combining carbapenems with other antimicrobial agents may help overcome
carbapenem resistance.
In vitro, imipenem plus sulbactam have shown synergistic activity, but clinical
usefulness in patients infected with carbapenem-resistant A baumannii is not
well established.
Pearls for Practice
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A baumannii infections usually occur in critically ill hospitalized patients with
patient-related and treatment-related risk factors. Institutional outbreaks of
antimicrobial drug–resistant A baumannii, usually arising from contaminated
environmental sites and medical equipment, or healthcare personnel with skin
colonization, are increasingly common.
Currently available antimicrobials potentially effective against A baumannii
include sulbactam; antipseudomonal penicillins, cephalosporins, and
carbapenems; monobactams; aminoglycosides; fluoroquinolones; tetracyclines;
glycylcyclines; and polymyxins. However, resistance rates of A baumannii to
many of these agents are high and are increasing, limiting effective treatment
options.
According to the review by Karageorgopoulos and Falagas, which of the following
statements about A baumannii infections in healthcare settings is not correct?
Secondary meningitis may occur in patients with ventricular draining tubes
Risk factors include advanced age, serious underlying diseases, and
immunosuppression
Contaminated food is the usual source for institutional outbreaks
Useful infection-control techniques include environmental cleaning, adequately
sterilizing reusable medical equipment, effective hand hygiene, and contact
precautions
According to the review by Karageorgopoulos and Falagas, which of the following
statements about antibiotic treatment of A baumannii infections is correct?
Resistance to carbapenems is infrequent
Severe toxicity precludes polymixin use
Large numbers of clinical trials support use of minocycline and tigecycline
Further research is needed to determine the best therapeutic options for
multidrug-resistant A baumannii infections
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Target Audience
This article is intended for infectious disease specialists, intensivists, public health
specialists, and other specialists who care for patients with Acinetobacter baumannii
infection.
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The goal of this activity is to provide medical news to primary care clinicians and other
healthcare professionals in order to enhance patient care.
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News Author
Laurie Barclay, MD
is a freelance reviewer and writer for Medscape.
Disclosure: Laurie Barclay, MD, has disclosed no relevant financial relationships.
CME Author
Laurie Barclay, MD
is a freelance reviewer and writer for Medscape.
Disclosure: Laurie Barclay, MD, has disclosed no relevant financial relationships.
Brande Nicole Martin
is the News CME editor for Medscape Medical News.
Disclosure: Brande Nicole Martin has disclosed no relevant financial information.
Medscape Medical News 2008. ©2008 Medscape
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