Table 1 Summary of studies using different techniques for quantification of bacterial biofilms.

Biofilm dry weight measurement²⁷

Acrylic slides

S. epidermidis

Up to 72 hr

To quantify differences in biofilm growth using batch and fed-batch culture methods

Impedance measurement⁴¹

24 well plate

P. aeruginosa

24 hr

To investigate the ability of impedance microsensors to detect biofilm presence using the impedance spectroscopy method.

Brief shaking and sonication in PBS^a supplemented with 0.05% Tween80⁴²

24-gauge polyurethane IV catheter used as a urinary catheter

No inoculation but multiple spp. biofilms formed naturally

2–6 weeks

Establishing a rat model to mimic the actual clinical environment and to study biofilm development on urinary catheters

Real time PCR^b 43

6-well polystyrene tissue culture plates

S. aureus clinical isolates

Up to 48 hr

To study transcriptional profiles of specific genes during biofilm production on polystyrene plates

Using nitrous oxide for biofilm dispersal⁴⁴

Glass tubing, 96- well plate, petri dish with glass slide

Pseudumonas aeruginosa

6 days and 24 hr

To examine if reactive oxygen or nitrogen intermediates help in biofilm dispersal

Swabbing vigorously with sterile cotton swab⁴⁵

Silicone-treated latex 8 Fr urethral catheters

No inoculation but multiple spp. biofilms formed naturally

Up to 5 days

To evaluate the efficacy and safety of a gentamicin sulphate coated urethral catheter

Fluorescence microscopy automatic counting system¹⁴

24 well plate

S. epidermidis strains

Up to 72 hr

To investigate the effects of sonication on the elimination of bacterial cell clusters from biofilms grown overtime

Sonication followed by vortex vs Roll plate method¹¹

Central venous catheters

Not described

Mean 55 days (range, 4 to 469 days)

To compare the yields of 2 techniques to detect catheter tip colonization in patients with long-term tunnelled catheters

Sonication vs swabbing¹⁰

PVC^c slides

Salmonella typhimurium or Pseudomonas fluorescens

24 hr

To compare techniques for assessing biofilm populations