What antibiotics (abx) are sensitive to Klebsiella (Enterobacter) aerogenes?

From the Guidelines

For the treatment of infections caused by Klebsiella (Enterobacter) aerogenes, carbapenems such as meropenem or imipenem are recommended as first-line options, due to their high efficacy against this organism 1.

Key Considerations

• Third and fourth-generation cephalosporins like ceftriaxone, cefepime, or ceftazidime may also be effective, though resistance through extended-spectrum beta-lactamases (ESBLs) is increasingly common 1.
• Fluoroquinolones such as ciprofloxacin or levofloxacin can be used if susceptibility is confirmed 1.
• Aminoglycosides like gentamicin or amikacin are often effective and may be used in combination therapy for synergistic effects, particularly in severe infections 1.

Treatment Approach

• For patients with severe infections, carbapenem-based therapy is preferred, with options including meropenem or imipenem 1.
• For patients with non-severe infections, piperacillin-tazobactam, amoxicillin/clavulanic acid, or quinolones may be considered, taking into account antibiotic stewardship principles 1.
• Combination therapy, such as a carbapenem plus an aminoglycoside, may be necessary for complicated infections 1.

Duration and Monitoring

• Treatment duration typically ranges from 7-14 days, depending on infection severity and site 1.
• Obtaining culture and sensitivity testing before initiating therapy is essential, as resistance patterns vary geographically and are evolving 1.
• Monitoring clinical response is crucial, as Enterobacter species have inducible AmpC beta-lactamases that can develop resistance during treatment with certain beta-lactams 1.

From the FDA Drug Label

The following in vitro data are available, but their clinical significance is unknown: Levofloxacin exhibits in vitro minimum inhibitory concentrations (MIC values) of 2 mcg/mL or less against most (≥ 90%) isolates of the following microorganisms; however, the safety and effectiveness of levofloxacin in treating clinical infections due to these bacteria have not been established in adequate and well-controlled clinical trials ... Enterobacter aerogenes Ciprofloxacin exhibits in vitro minimum inhibitory concentrations (MICs) of 1 μg/mL or less against most (≥ 90%) strains of the following microorganisms; however, the safety and effectiveness of ciprofloxacin in treating clinical infections due to these microorganisms have not been established in adequate and well-controlled clinical trials ... Enterobacter aerogenes

• Levofloxacin and Ciprofloxacin have in vitro activity against Enterobacter aerogenes (also known as Klebsiella aerogenes).
• The MIC values for these antibiotics against Enterobacter aerogenes are ≤ 2 μg/mL for Levofloxacin and ≤ 1 μg/mL for Ciprofloxacin.
• However, the clinical significance of these in vitro data is unknown, and the safety and effectiveness of these antibiotics in treating clinical infections due to Enterobacter aerogenes have not been established in adequate and well-controlled clinical trials 2 3.

From the Research

Antibiotic Sensitivity of Klebsiella (Enterobacter) aerogenes

• The sensitivity of Klebsiella (Enterobacter) aerogenes to various antibiotics has been studied in several research papers 4, 5, 6, 7, 8.
• A study published in 2020 found that meropenem-vaborbactam has shown decreased rates of resistance to KPC versus ceftazidime-avibactam 4.
• Another study published in 2023 found that third-generation cephalosporins may be susceptible in vitro to Enterobacter spp. and Klebsiella aerogenes, and definitive 3GC therapy for susceptible Enterobacter spp. and Klebsiella aerogenes bacteremia is as clinically effective and valuable as non-3GC therapy 5.
• A study published in 2015 reported that Enterobacter aerogenes and E. cloacae have been described as important opportunistic and multiresistant bacterial pathogens for humans, and the dissemination of Enterobacter sp. is associated with the presence of redundant regulatory cascades that efficiently control the membrane permeability ensuring the bacterial protection and the expression of detoxifying enzymes involved in antibiotic degradation/inactivation 6.
• A study published in 2021 found that piperacillin-tazobactam demonstrated significant inoculum-dependent killing against Klebsiella aerogenes, warranting dose optimization studies 7.
• Another study published in 2021 found that the combination of cefepime or meropenem with the new beta-lactamase inhibitor taniborbactam showed promising activity against Klebsiella pneumoniae and Pseudomonas aeruginosa metallo-beta-lactamase-producing clinical isolates 8.

Specific Antibiotics

• Meropenem-vaborbactam: has shown decreased rates of resistance to KPC versus ceftazidime-avibactam 4.
• Ceftazidime-avibactam: has shown considerable improvement in safety and efficacy as compared with traditional polymyxin-based combination therapy for the treatment of KPC infections 4.
• Third-generation cephalosporins: may be susceptible in vitro to Enterobacter spp. and Klebsiella aerogenes, and definitive 3GC therapy for susceptible Enterobacter spp. and Klebsiella aerogenes bacteremia is as clinically effective and valuable as non-3GC therapy 5.
• Piperacillin-tazobactam: demonstrated significant inoculum-dependent killing against Klebsiella aerogenes, warranting dose optimization studies 7.
• Cefepime-taniborbactam and meropenem-taniborbactam: are promising alternative treatment options for infections by MBL-producing isolates 8.