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Published on: September 25, 2014
Association of capsular polysaccharide locus 2 with prognosis of Acinetobacter baumannii bacteraemia
Jia-Ling Yang1, Chia-Jui Yang2,3, Yu-Chung Chuang1
1Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan.
Abstract:
Acinetobacter baumannii causes healthcare-associated infections worldwide. Capsular polysaccharide (CPS) is shown an important virulence factor of A. baumannii both in vitro and in vivo. Capsule locus 2 (KL2) for CPS is the most common KL type and is associated with carbapenem resistance. It is unclear whether KL2 is related to the clinical outcome of invasive A. baumannii infection. Here we had followed patients with A. baumannii bacteraemia prospectively between 2009 and 2014. One-third of the unduplicated blood isolates were randomly selected each year for microbiological and clinical studies. The KL2 gene cluster was identified using polymerase chain reaction. A total of 148 patients were enrolled randomly. Eighteen isolates (12.2%) carried KL2, and 130 isolates (87.8%) didn't. Compared with non-KL2 isolates, KL2 isolates had significantly higher resistance to imipenem, sulbactam, and tigecycline. Compared with the non-KL group, in the KL2 group, the hospital stay before development of bacteraemia was longer (P < 0.001), a higher percentage had pneumonia (P = 0.004), and the white blood cell count was lower (P = 0.03). Infection with KL2 A. baumannii predicted mortality (adjusted hazard ratio [aHR], 2.03; 95% confidence interval [CI], 1.09-3.78; P = 0.03), independently of the Pitt bacteraemia score (aHR, 1.34; 95% CI, 1.23-1.46; P < 0.001) and leucopenia (aHR, 2.16; 95% CI, 1.30-3.57; P = 0.003). Thrombocytopenia contributed to the effect of KL2 on mortality in bacteraemia (Sobel test P = 0.01). Large-scale studies are warranted to confirm these findings and the underlying mechanisms deserve further investigation.
Insights
Capsule locus 2 (KL2) in Acinetobacter baumannii is linked to increased resistance and poorer patient outcomes, including higher mortality risk. Further research is needed to confirm these findings and explore mechanisms.
Area of Science:
- Microbiology
- Infectious Diseases
- Clinical Medicine
Background:
- Acinetobacter baumannii is a significant cause of healthcare-associated infections globally.
- Capsular polysaccharide (CPS) is a key virulence factor in A. baumannii.
- Capsule locus 2 (KL2) is the most prevalent CPS type and is associated with carbapenem resistance.
Purpose of the Study:
- To investigate the association between the KL2 gene cluster and clinical outcomes in patients with A. baumannii bacteremia.
- To determine if KL2 influences patient mortality independently of other clinical factors.
Main Methods:
- Prospective follow-up of patients with A. baumannii bacteremia from 2009-2014.
- Random selection of blood isolates for microbiological analysis, including PCR identification of the KL2 gene cluster.
- Clinical data collection and statistical analysis, including survival analysis and assessment of contributing factors like thrombocytopenia.
Main Results:
- Eighteen percent of A. baumannii isolates carried the KL2 gene cluster.
- KL2 isolates exhibited significantly higher resistance to imipenem, sulbactam, and tigecycline compared to non-KL2 isolates.
- Patients infected with KL2 isolates had longer hospital stays, higher rates of pneumonia, and lower white blood cell counts.
- Infection with KL2 A. baumannii was an independent predictor of mortality, with thrombocytopenia contributing to this effect.
Conclusions:
- The KL2 gene cluster in A. baumannii is associated with increased antimicrobial resistance and adverse clinical outcomes, including higher mortality.
- KL2 may represent a significant risk factor for severe invasive A. baumannii infections.
- Further large-scale studies are warranted to validate these findings and elucidate the underlying pathogenetic mechanisms.
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