Bacteriology

Bacterial culture results are provided in two to three days after submission. For urgent cases, preliminary results will be phoned to the clinician, as soon as they are available.

Alongside standard aerobic, anaerobic and microaerophilic cultures, we also screen, when necessary, for specific pathogens such as Mycoplasma spp., Bordetella spp. and Clostridium difficile. Where appropriate, samples are screened for methicillin resistant Staphylococcus aureus (MRSA), S. pseudintermedius (MRSP) or S. schleiferi (MRSS), extended spectrum β-lactamase (ESBLs) producing bacteria and vancomycin resistant enterococci (VRE). All suspected methicillin resistant staphylococci (MRSA, MRSP, MRSS) isolates are tested by PCR for confirmation of mecA/mecC carriage.

Antimicrobial susceptibility testing is provided by disc diffusion and automated reading of inhibition zones  (SIRScan, I2A, France) and by determining Minimum Inhibitory Concentration (MICs) by broth microdilution (SENSITITRE OPTIRED, TREK Sensititre System).

Bacterial identification is performed by matrix-assisted laser desorption/ionisation time-of-flight (MALDI-TOF or MALDI) mass spectrometry and the first results, including bacterial culture findings with species identification, are issued one day after the specimens arrive at the laboratory.

Interpretation of susceptibility testing is performed by applying the Clinical and Laboratory Standards Institute (CLSI) and the European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints.

The bacteriology test range includes:

  • Routine aerobic, anaerobic and microaerophilic bacterial culture
  • Identification of bacterial isolates at species level
  • Bacterial identification by 16S rRNA (PCR and sequencing)
  • Antimicrobial susceptibility testing (disc diffusion where the reading is performed automatically with SirScan reader)
  • Antimicrobial susceptibility testing, minimal inhibitory concentrations (MIC) by broth microdilution with TREK Sensititre
  • E coli serotyping
  • Salmonella spp. serotyping
  • Beta-haemolytic Streptococci serotyping
  • Faecal culture (screening for Salmonella spp., Campylobacter spp., Cl. perfringens, Cl. difficile, Yersinia spp., E. coli 0157)
  • Direct smear examination (Gram staining, Ziehl-Neelsen staining, India ink staining)
  • Gram staining of gastric biopsy tissue for Helicobacter spp. detection

Phenotypic and molecular methods for the detection of antibiotic resistance mechanisms in Gram positive and Gram negative bacteria, include:

  • MRSA/MRSP detection (chromogenic media and mecA and mecC detection via PCR)
  • Inducible clindamycin resistance (including confirmation of erm genes)
  • Resistance to 3rd generation cephalosporins via extended spectrum beta-lactamase (ESBL) or AmpC production (phenotypic and genotypic detection)
  • Detection of plasmid mediated resistance to fluoroquinolones (qnr genes), carbapenems (NDM, OXA, KPC-like), colistin (mcr-1 and mcr-2)

Please contact us for more information and prices: vpserve@liv.ac.uk or 0151 795 6294.