Longitudinal epidemiology of multidrug-resistant (MDR) Acinetobacter species in a tertiary care hospital
Ji Hoon Baang1, Peter Axelrod, Brooke K Decker
1Section of Infectious Diseases, Temple University School of Medicine, Philadelphia, PA, USA.
Background:
Acinetobacter species are well-known causes of health care-associated infections. The longitudinal epidemiology of this species in the hospital setting is poorly understood. A sudden, persistent increase in multidrug-resistant (MDR) A baumannii infections occurred beginning in June 2006 at Temple University Hospital in Philadelphia. An analysis was done to describe the longitudinal molecular epidemiology of MDR A baumannii in a tertiary care hospital.
Methods:
This was an epidemiologic investigation using repetitive extragenic palindromic-PCR (rep-PCR) of patients with a positive culture for MDR A baumannii admitted to the hospital between February 2006 and January 2010. MDR A baumannii were defined as susceptible only to colistin and/or tigecycline.
Results:
The incidence rate of MDR A baumannii rose from 0.36 cases per 1,000 patient-days (pre-epidemic) to 0.86 cases per 1,000 patient-days, due mainly to an increase in the surgical intensive care unit. Enhanced infection control measures were implemented, but waves of MDR A baumannii continued to be documented through routine surveillance. Of 32 strains collected in 2006-2007, a single predominant clone and 2 minor clones accounted for almost all of the cases of MDR A baumannii studied. Of 24 strains collected in 2008-2009, another clone, different from those studied in the earlier period, predominated, and was accompanied by 3 minor variants.
Conclusion:
Following an outbreak in the surgical intensive care unit, MDR A baumannii persisted in our institution for a 3-year period despite rigorous infection control measures. An unexpected strain replacement occurred during this period, with the original predominant strain disappearing completely and new minor clones displacing the original minor clones.
Insights
Multidrug-resistant Acinetobacter baumannii (MDR A. baumannii) infections persisted in a hospital for three years. A significant strain replacement occurred, with new clones emerging despite infection control efforts.
Area of Science:
- Medical Microbiology
- Infectious Diseases
- Epidemiology
Background:
- Acinetobacter species are significant causes of healthcare-associated infections.
- The long-term epidemiology of Acinetobacter in hospitals is not well understood.
- A sustained rise in multidrug-resistant (MDR) Acinetobacter baumannii infections was observed starting in June 2006.
Purpose of the Study:
- To describe the longitudinal molecular epidemiology of MDR A. baumannii in a tertiary care hospital.
- To analyze the genetic relatedness and evolution of MDR A. baumannii strains over time.
Main Methods:
- Epidemiologic investigation utilizing repetitive extragenic palindromic-PCR (rep-PCR).
- Analysis of MDR A. baumannii strains from patients admitted between February 2006 and January 2010.
- MDR A. baumannii defined as resistant to all but colistin and/or tigecycline.
Main Results:
- Incidence of MDR A. baumannii increased from 0.36 to 0.86 cases per 1,000 patient-days, primarily in the surgical ICU.
- Despite enhanced infection control, MDR A. baumannii waves continued.
- In 2006-2007, one predominant clone and two minor clones were identified.
- In 2008-2009, a new predominant clone emerged, along with three minor variants, indicating strain replacement.
Conclusions:
- MDR A. baumannii persisted for three years post-outbreak, challenging infection control measures.
- An unexpected replacement of the predominant A. baumannii clone occurred.
- New clones emerged and displaced original minor clones, highlighting evolving resistance patterns.
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