Related Experiment Video
Updated: Apr 6, 2026
Isolation and Identification of Waterborne Antibiotic-Resistant Bacteria and Molecular Characterization of their Antibiotic Resistance Genes
Published on: March 3, 2023
What Contributes to the Minimum Inhibitory Concentration? Beyond β-Lactamase Gene Detection in Klebsiella pneumoniae
Alyssa K W Maclean1,2, Stacey Morrow1,2, Fang Niu3
1Department of Medical Microbiology and Immunology, CRISS 2.
Background:
Klebsiella pneumoniae is capable of resistance to β-lactam antibiotics through expression of β-lactamases (both chromosomal and plasmid-encoded) and downregulation of outer membrane porins. However, the extent to which these mechanisms interplay in a resistant phenotype is not well understood. The purpose of this study was to determine the extent to which β-lactamases and outer membrane porins affected β-lactam resistance.
Methods:
Minimum inhibitory concentrations (MICs) to β-lactams and inhibitor combinations were determined by agar dilution or Etest. Outer membrane porin production was evaluated by Western blot of outer membrane fractions. β-lactamase carriage was determined by whole genome sequencing and expression evaluated by real-time reverse-transcription polymerase chain reaction.
Results:
Plasmid-encoded β--lactamases were important for cefotaxime and ceftazidime resistance. Elevated expression of chromosomal SHV was important for ceftolozane-tazobactam resistance. Loss of outer membrane porins was predictive of meropenem resistance. Extended-spectrum β-lactamases and plasmid-encoded AmpCs (pAmpCs) in addition to porin loss were sufficient to confer resistance to the third-generation cephalosporins, piperacillin-tazobactam, ceftolozane-tazobactam, and meropenem. pAmpCs (CMY-2 and DHA) alone conferred resistance to piperacillin-tazobactam.
Conclusions:
Detection of a resistance gene by whole genome sequencing was not sufficient to predict resistance to all antibiotics tested. Some β-lactam resistance was dependent on the expression of both plasmid-encoded and chromosomal β-lactamases and loss of porins.
Insights
Klebsiella pneumoniae resistance to beta-lactam antibiotics involves beta-lactamases and porin loss. Understanding their interplay is key to predicting and combating antibiotic resistance effectively.
Area of Science:
- Microbiology
- Molecular Biology
- Pharmacology
Background:
- Klebsiella pneumoniae exhibits resistance to beta-lactam antibiotics via beta-lactamase expression and reduced outer membrane porin production.
- The synergistic interaction between these resistance mechanisms remains incompletely understood.
Purpose of the Study:
- To investigate the combined impact of beta-lactamases and outer membrane porins on the beta-lactam resistance phenotype in Klebsiella pneumoniae.
Main Methods:
- Minimum inhibitory concentrations (MICs) were determined using agar dilution and Etest.
- Outer membrane protein expression was analyzed via Western blot.
- Whole genome sequencing and RT-qPCR were employed to identify and quantify beta-lactamase genes and their expression.
Main Results:
- Plasmid-encoded beta-lactamases conferred resistance to cefotaxime and ceftazidime.
- Elevated chromosomal SHV expression was crucial for ceftolozane-tazobactam resistance.
- Loss of outer membrane porins predicted meropenem resistance, and combined with ESBLs/pAmpCs, led to resistance against multiple beta-lactams.
Conclusions:
- Genetic detection of resistance genes alone is insufficient for predicting antibiotic resistance.
- Beta-lactam resistance in Klebsiella pneumoniae is often a result of combined expression of chromosomal and plasmid-encoded beta-lactamases and porin downregulation.
More Related Videos
Related Concept Videos
01:15Determination of Multiple Dosing Parameters: Steady-State, Minimum and Maximum Concentrations
01:27Pharmacodynamic Models: Overview
01:29Factors Influencing Microbial Growth: pH
01:28Antimicrobial Effectiveness
01:25Mechanism of Antibiotic Resistance in MRSA
01:25Clinical Significance of Antibiotic Resistance