Antimicrobial Susceptibility Testing (AST) for Klebsiella species

Advanced Antimicrobial Susceptibility Testing (AST) for Klebsiella species – From MIC Determination to Resistance Mechanism Profiling

If you are searching for a reliable Klebsiella susceptibility test, you likely need to determine the antibiotic resistance profile of a clinical, environmental, or food isolate – whether for patient management, infection control, veterinary guidance, or regulatory surveillance. Standard disk diffusion provides only qualitative (susceptible/intermediate/resistant) results and misses low‑level resistance. We provide a comprehensive Klebsiella antimicrobial susceptibility testing (AST) service that delivers quantitative minimum inhibitory concentrations (MICs), extended‑spectrum beta‑lactamase (ESBL) and carbapenemase phenotyping, and molecular resistance gene detection – all performed under CLSI or EUCAST guidelines.

What We Measure – Quantitative MICs & Expanded Antibiotic Panels

We determine MIC values (µg/mL) using the broth microdilution reference method (ISO 20776‑1) in 96‑well format, covering up to 30 antibiotics per isolate. Our standard panel for Klebsiella pneumoniae and Klebsiella oxytoca includes: beta‑lactams (ampicillin, amoxicillin‑clavulanate, piperacillin‑tazobactam, cefazolin, cefuroxime, ceftriaxone, ceftazidime, cefepime, aztreonam), carbapenems (imipenem, meropenem, ertapenem), aminoglycosides (gentamicin, tobramycin, amikacin), fluoroquinolones (ciprofloxacin, levofloxacin), tigecycline, colistin (polymyxin E), fosfomycin, trimethoprim‑sulfamethoxazole, and chloramphenicol. For veterinary or food isolates, we also include florfenicol and ceftiofur. We report MIC50/MIC90 for isolate panels and categorical interpretation according to current CLSI M100 or EUCAST clinical breakpoints. The assay detects MICs ranging from 0.008 – 256 µg/mL with inter‑run precision ±1 two‑fold dilution.

Deep Technical Capabilities – Resistance Phenotyping & Genotyping

Routine AST does not distinguish resistance mechanisms. For all Klebsiella isolates showing reduced susceptibility to cephalosporins or carbapenems, we perform confirmatory phenotypic tests: double‑disk synergy test (DDST) for ESBL production (using ceftazidime + clavulanate), modified carbapenem inactivation method (mCIM) with EDTA‑mCIM for metallo‑beta‑lactamase (MBL) detection, and combined disk test with boronic acid for KPC carbapenemase. Using these methods, we identify ESBL‑producers, AmpC hyperproducers, KPC, NDM, VIM, IMP, and OXA‑48‑like carbapenemases. For definitive molecular characterisation, we perform multiplex PCR and real‑time PCR targeting the most prevalent resistance genes: bla_CTX‑M (groups 1, 2, 9), bla_SHV, bla_TEM, bla_KPC, bla_NDM, bla_VIM, bla_IMP, bla_{OXA‑48‑like}, mcr‑1 to mcr‑9 (colistin resistance), and plasmid‑mediated quinolone resistance (qnrA, qnrB, qnrS). For outbreak investigation, we offer whole‑genome sequencing (WGS) of Klebsiella isolates to identify multilocus sequence types (MLST), resistance gene allelic variants, and phylogenetic relationships – with a turnaround of 7‑10 days.

Advanced AST Capabilities – Combination Testing & Biofilm Susceptibility

For multidrug‑resistant (MDR) or extensively drug‑resistant (XDR) K. pneumoniae isolates, we go beyond single‑agent MICs to provide synergy testing using checkerboard broth microdilution for antibiotic combinations (e.g., ceftazidime‑avibactam, meropenem‑vaborbactam, colistin‑rifampicin, fosfomycin‑meropenem). The fractional inhibitory concentration index (FICI) is calculated, with FICI ≤0.5 defined as synergy – guiding effective combination therapy. Additionally, because Klebsiella often forms biofilms on medical devices, we offer a biofilm MIC (bMIC) assay using a Calgary Biofilm Device (CBD) or 96‑well peg lid system: minimum biofilm eradication concentration (MBEC) is determined for up to eight antibiotics, typically 10‑ to 1000‑fold higher than planktonic MICs. This service is critical for catheter‑associated or implant‑related infections. We also perform time‑kill kinetics (log reduction over 24 h) for selected antibiotics and combinations, providing visual kill curves.

Why Choose Our Klebsiella Susceptibility Testing Service

Comprehensive, guideline‑aligned, and rapid. Our AST workflows follow CLSI M100‑Ed32 and EUCAST v13.0 breakpoints, updated quarterly. We hold ISO 17025:2017 accreditation for antimicrobial susceptibility testing of Enterobacteriaceae. Turnaround: preliminary MIC results in 18‑24 hours (broth microdilution), confirmatory synergy testing in 48 hours, and full WGS‑based resistance profiling in 7‑10 days. Strain diversity: We have tested >2,500 Klebsiella isolates – including clinical (blood, urine, respiratory), environmental (water, hospital surfaces), and food isolates – with an extensive internal MIC database for quality control (QC strain K. pneumoniae ATCC 700603 and ATCC 13883). Matrix expertise: Validated for pure cultures, mixed cultures (after selective isolation), and direct testing from positive blood cultures (short incubation) upon request. QC rigor: Each AST run includes recommended QC strains (E. coli ATCC 25922, K. pneumoniae ATCC 700603, P. aeruginosa ATCC 27853) and controls for each antibiotic – MIC values must fall within acceptable ranges.

Detailed Deliverables – From MIC Tables to Clinical/Research Reports

Your final report includes: quantitative MIC values for each antibiotic tested, categorical interpretation (S/I/R) with breakpoint version cited, phenotypic resistance mechanism (ESBL, carbapenemase type), genotypic resistance gene profile (PCR or WGS), and recommended alternative agents or combinations based on synergy testing. For biofilm‑forming isolates, we provide MBEC values and a biofilm susceptibility score. For research customers, raw data (microdilution plates, PCR gels or qPCR amplification plots, sequencing files) are available on request. All data are delivered as a signed PDF with chain‑of‑custody, and optional GLP/CLIA‑compliant formats for clinical use (requires additional laboratory certification). Our lab offers express AST for urgent clinical isolates (MICs within 6 hours using rapid automated systems – VITEK® 2 compact) as a supplementary service.

Struggling with a resistant Klebsiella isolate – unsure of the optimal antibiotic or combination? Need to characterise resistance determinants for an outbreak or regulatory submission? Contact our AST core for a free consultation. We will help you select the appropriate antibiotic panel, synergy testing strategy, and molecular follow‑up based on your isolate origin and clinical or research objectives.