What antibiotics is Klebsiella pneumoniae typically sensitive to and at what percentage?

Antibiotic Susceptibility of Klebsiella pneumoniae

Klebsiella pneumoniae susceptibility varies dramatically based on resistance mechanisms, with carbapenem-susceptible strains showing high susceptibility to carbapenems and third-generation cephalosporins, while carbapenem-resistant strains require novel β-lactam/β-lactamase inhibitor combinations, with specific susceptibility rates depending on the carbapenemase type present.

Susceptibility Patterns by Resistance Mechanism

Non-Resistant K. pneumoniae

• Carbapenems remain the treatment of choice for susceptible strains, with traditional high susceptibility rates to imipenem, meropenem, and ertapenem 1
• Third and fourth-generation cephalosporins (ceftriaxone, cefotaxime, cefepime) are effective first-line treatments for susceptible strains 1

ESBL-Producing K. pneumoniae

• Carbapenems maintain high efficacy as first-line treatment options for ESBL-producing strains 1
• ESBL-producing strains remain intrinsically resistant to ampicillin and other aminopenicillins 2
• These strains acquire resistance to cephalosporins and aztreonam through ESBL production but remain susceptible to carbapenems 2
• In Taiwan data, ertapenem susceptibility was 90% for ESBL-producing K. pneumoniae using older breakpoints, dropping to 78% with newer CLSI 2010 breakpoints 2

KPC-Producing (Carbapenem-Resistant) K. pneumoniae

Novel agents show the following susceptibility rates:

• Ceftazidime/avibactam: Resistance rates range from 0% to 12.8% in KPC-producing isolates, meaning susceptibility is approximately 87-100% 2
• Colistin: Susceptibility approximately 95.5% (resistance rate 4.5%) 3
• Gentamicin: Susceptibility approximately 93% (resistance rate 7%) 3
• Tigecycline: Susceptibility approximately 85% (resistance rate 15%), though it performs poorly in bacteremic patients 3, 2
• Cefiderocol: Susceptibility 96% in carbapenem-resistant VAP isolates 4
• Ceftolozane/tazobactam: Poor activity with 100% resistance in carbapenem-resistant isolates 4

OXA-48-Producing K. pneumoniae

• Ceftazidime/avibactam should be first-line, though specific susceptibility percentages are not well-documented in the provided evidence 2

MBL-Producing K. pneumoniae

• Ceftazidime/avibactam plus aztreonam is preferred, as ceftazidime/avibactam alone shows 79% resistance in carbapenem-resistant isolates 4, 5
• Cefiderocol shows 96% susceptibility and may be considered as an alternative 4, 5

Clinical Outcomes Data

Mortality and Efficacy Comparisons

• 28-day mortality with ceftazidime/avibactam was 18.3% versus 40.8% with other active agents (p=0.005) in KPC-producing K. pneumoniae bloodstream infections 2, 1
• 30-day clinical success rates were significantly higher with ceftazidime/avibactam compared to carbapenem plus aminoglycoside (p=0.04) or carbapenem plus colistin (p=0.009) 2
• Meropenem/vaborbactam demonstrated higher clinical cure rates and decreased mortality compared to best available therapy in the TANGO II study 2, 1

Critical Pitfalls

Testing Considerations

• Some KPC-producing strains have MICs within the susceptible range for carbapenems by routine testing but still cause clinical failures when treated with carbapenems 2, 6
• Modified Hodge Test (MHT) should be performed on carbapenem-susceptible Enterobacteriaceae with elevated MICs, with sensitivity and specificity exceeding 90% for detecting carbapenemases 2
• In one study, 82.6% of carbapenem-resistant isolates were MHT-positive, and 67.4% carried the blaKPC gene 7

Resistance Patterns

• 93.4% of carbapenem-resistant isolates were resistant to meropenem, 73.9% to imipenem, and 65.2% to both in one tertiary care study 7
• Almost all carbapenem-resistant K. pneumoniae isolates are resistant to virtually all commonly used antibiotics except colistin, gentamicin, and tigecycline 3
• Bla NDM was the most prevalent carbapenemase gene (50%), followed by bla OXA-48 (36.5%), then bla KPC (11.5%) in VAP isolates 4