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Klebsiella and enterobacter: antibiotic resistance and treatment implications
Emilio Bouza1, Emilia Cercenado
1Servicio de Microbiología Clínica and Enfermedades Infecciosas, Hospital General Universitario "Gregorio Marañón," Universidad Complutense de Madrid, Madrid, Spain. ebouza@microb.net
Abstract:
KLEBSIELLA: spp. and Enterobacter spp. are widespread throughout the environment and also carried by humans. Both genera are well-recognized community and nosocomial pathogens and cause significant infections. They are a common cause of respiratory and nonrespiratory infections. Klebsiella spp. is responsible for 1% to 5% of all cases of community-acquired pneumonia and between 0% to 23% of those acquired in the hospital, and its frequency is greater in alcoholic patients. The majority of cases are unilateral in the posterior segment of the right upper lobe. Lung abscess can occur after a pneumonic process or secondarily to Klebsiella spp. infections and have high rates of morbidity and mortality. K. pneumoniae is one of the most common microorganisms responsible for empyema. Klebsiella spp. and Enterobacter spp. rank fourth and third, respectively, as causes of hospital-acquired pneumonia mainly in patients during the early period of mechanical ventilation. Klebsiella spp. are intrinsically resistant to penicillins and can acquire resistance to third- and fourth-generation cephalosporins owing to the production of plasmid-mediated extended-spectrum beta-lactamases (ESBLs). These plasmids frequently carry aminoglycoside-modifying enzymes. Enterobacter spp. are intrinsically resistant to ampicillin, amoxicillin, amoxicillin-clavulanate, first-generation cephalosporins, and cefoxitin owing to the production of constitutive AmpC beta-lactamase. The derepression of this enzyme is increasingly frequent among clinical isolates and confers resistance to third-generation cephalosporins, and ureido- and carboxypenicillins; fourth-generation cephalosporins retain reasonable activity against depressed strains. Most isolates of Klebsiella spp. and Enterobacter spp. are susceptible to fluoroquinolones, trimethoprimsulfamethoxazole, aminoglycosides, and carbapenems. In some instances, treatment of severe infections caused by these microorganisms may benefit from the combination of beta-lactams (or fluoroquinolones) with aminoglycosides. Because of the high risk for developing resistance during treatment, all severe infections should be carefully watched during therapy.
Insights
Klebsiella and Enterobacter species are common pathogens causing significant respiratory and nonrespiratory infections. Understanding their resistance patterns is crucial for effective treatment, especially in hospital-acquired pneumonia.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Klebsiella spp. and Enterobacter spp. are prevalent environmental and human pathogens.
- These bacteria are significant causes of both community-acquired and hospital-acquired infections, including pneumonia, lung abscess, and empyema.
- Certain patient populations, such as alcoholics and those on mechanical ventilation, are at higher risk.
Purpose of the Study:
- To review the clinical significance and antimicrobial resistance profiles of Klebsiella spp. and Enterobacter spp.
- To highlight their roles in various infections and the challenges in treatment.
- To inform appropriate therapeutic strategies and monitoring.
Main Methods:
- Literature review of Klebsiella and Enterobacter infections and antimicrobial susceptibility.
- Analysis of resistance mechanisms, including extended-spectrum beta-lactamases (ESBLs) and AmpC beta-lactamase production.
- Evaluation of treatment outcomes and recommendations for severe infections.
Main Results:
- Klebsiella spp. and Enterobacter spp. are leading causes of hospital-acquired pneumonia, particularly in ventilated patients.
- Intrinsic and acquired resistance mechanisms, such as ESBLs and AmpC beta-lactamase, confer resistance to common antibiotics like penicillins and cephalosporins.
- Most isolates remain susceptible to fluoroquinolones, trimethoprim-sulfamethoxazole, aminoglycosides, and carbapenems.
Conclusions:
- Effective management of Klebsiella and Enterobacter infections requires awareness of their resistance patterns.
- Combination therapy, such as beta-lactams with aminoglycosides, may be beneficial for severe infections.
- Close monitoring during treatment is essential due to the high risk of resistance development.