Is Klebsiella (formerly Raoultella) a pathogen?

From the Guidelines

Yes, Klebsiella (including the reclassified genus Raoultella) is pathogenic. These gram-negative bacteria can cause various infections in humans, particularly in healthcare settings and immunocompromised individuals. Klebsiella pneumoniae is the most clinically significant species, commonly causing pneumonia, urinary tract infections, bloodstream infections, and wound infections. Raoultella species (formerly classified as Klebsiella) can also cause similar infections though less frequently. These bacteria are concerning because they often carry antibiotic resistance genes, with some strains developing resistance to multiple antibiotics including carbapenems. Treatment typically involves antibiotics based on susceptibility testing, often requiring combinations like piperacillin-tazobactam, carbapenems, or cephalosporins, sometimes with aminoglycosides for synergy in severe cases. The pathogenicity of these bacteria stems from virulence factors including capsular polysaccharides that protect against phagocytosis, lipopolysaccharides that trigger inflammatory responses, and various adhesins that facilitate colonization of host tissues.

Key Points

• Klebsiella pneumoniae is the most clinically significant species, causing various infections in humans, particularly in healthcare settings and immunocompromised individuals 1.
• These bacteria often carry antibiotic resistance genes, with some strains developing resistance to multiple antibiotics including carbapenems 1.
• Treatment typically involves antibiotics based on susceptibility testing, often requiring combinations like piperacillin-tazobactam, carbapenems, or cephalosporins, sometimes with aminoglycosides for synergy in severe cases 1.
• The pathogenicity of these bacteria stems from virulence factors including capsular polysaccharides, lipopolysaccharides, and various adhesins that facilitate colonization of host tissues.

Management and Treatment

• Empiric antibiotic therapy should be started as soon as possible in patients with organ dysfunction and septic shock 1.
• The choice of empiric antibiotic regimens in patients with intra-abdominal infections should be based on the clinical condition of the patients, the individual risk for infection by resistant pathogens, and the local resistance epidemiology 1.
• In patients with complicated intra-abdominal infections, a short course of antibiotic therapy (3-5 days) after adequate source control is a reasonable option 1.

Prevention and Control

• The emergence and spread of carbapenem-resistant Enterobacteriaceae (CRE) and other types of resistant gram-negative bacteria underscore the immediate need for aggressive detection and control strategies 1.
• Local resistance patterns of nosocomial isolates observed in the specific hospital should dictate empiric treatment, and treatment should be altered on the basis of a thorough microbiologic work-up of infected fluid 1.

From the FDA Drug Label

The avibactam component of AVYCAZ is a non-beta-lactam beta-lactamase inhibitor that inactivates certain beta-lactamases that degrade ceftazidime. AVYCAZ demonstrated in vitro activity against Enterobacteriaceae in the presence of some beta-lactamases and extended-spectrum beta-lactamases (ESBLs) of the following groups: TEM, SHV, CTX-M, Klebsiella pneumoniae carbapenemase (KPCs), AmpC, and certain oxacillinases (OXA). Piperacillin has been shown to be active against most strains of the following microorganisms, both in vitro and in clinical infections as described in the INDICATIONS AND USAGE section Aerobic gram-negative microorganisms Klebsiella species

Klebsiella is considered a pathogenic bacterium, as it is listed among the microorganisms that the antibiotics AVYCAZ and piperacillin are active against, both in vitro and in clinical infections 2 3.

• Key points:
  • AVYCAZ has in vitro activity against Klebsiella pneumoniae
  • Piperacillin is active against Klebsiella species These points suggest that Klebsiella is a pathogen that can cause infections that require treatment with antibiotics.

From the Research

Pathogenicity of Klebsiella (Raoultella)

• The genus Raoultella, previously classified as Klebsiella, is known to be opportunistic bacteria that can cause infections in humans, particularly in those with compromised immunity 4, 5.
• Raoultella species are Gram-negative, aerobic, non-motile rods that can be distinguished from Klebsiella by their ability to use histamine as a carbon source and grow at 4°C 4.
• The most frequently encountered human pathogens among the Raoultella genus are Raoultella planticola and Raoultella ornithinolytica, which can cause infections such as biliary tract infections, pneumonia, and bacteraemia 4, 6.
• The epidemiology and clinical relevance of human Raoultella infections are uncertain and require further studies, but it is suggested that Raoultella might be underdiagnosed rather than rare or emerging pathogens 5.
• The introduction of more precise identification techniques, such as mass-spectrometry and molecular methods, has led to an increase in reported cases of Raoultella infections, highlighting the importance of accurate identification of this genus 5, 6.

Infections Caused by Raoultella

• Raoultella infections often occur in patients with underlying conditions, such as malignancy or those who have undergone invasive procedures, and can cause significant morbidity and mortality 4, 6.
• The biliary tract is a common site of infection for Raoultella, and identification of this genus can help clinicians suspect underlying biliary tract disease when bacteraemia occurs 6.
• The use of MALDI-TOF or additional phenotypic tests is recommended for the reliable identification of Raoultella, as most phenotypic identification systems are not optimized for this genus 6.

Treatment of Raoultella Infections

• The treatment of Raoultella infections often involves the use of antibiotics, such as piperacillin-tazobactam or meropenem, but the most effective treatment strategy is still uncertain and requires further study 7, 8.
• The MERINO trial, a randomized controlled trial, aimed to compare the effectiveness of meropenem and piperacillin-tazobactam for the treatment of bloodstream infections caused by ceftriaxone non-susceptible Escherichia coli and Klebsiella spp. 7, 8.