Using bacteriophages to reduce formation of catheter-associated biofilms by Staphylococcus epidermidis

Abstract

Use of indwelling catheters is often compromised as a result of biofilm formation. This study investigated if hydrogel-coated catheters pretreated with a coagulase-negative bacteriophage would reduce Staphylococcus epidermidis biofilm formation. Biofilms were developed on hydrogel-coated silicone catheters installed in a modified drip flow reactor. Catheter segments were pretreated with the lytic S. epidermidis bacteriophage 456 by exposing the catheter lumen to a 10-log-PFU/ml culture of the bacteriophage for 1 h at 37 degrees C prior to biofilm formation. The untreated mean biofilm cell count was 7.01+/-0.47 log CFU/cm2 of catheter. Bacteriophage treatment with and without supplemental divalent cations resulted in log-CFU/cm2 reductions of 4.47 (P<0.0001) and 2.34 (P=0.001), respectively. Divalent cation supplementation without bacteriophage treatment provided a 0.67-log-CFU/cm2 reduction (P=0.053). Treatment of hydrogel-coated silicone catheters with an S. epidermidis bacteriophage in an in vitro model system significantly reduced viable biofilm formation by S. epidermidis over a 24-h exposure period, suggesting the potential of bacteriophage for mitigating biofilm formation on indwelling catheters and reducing the incidence of catheter-related infections.

FIG. 1.

Modified drip flow reactor, showing catheter segments in each of the four chambers.

FIG. 2.

Model system used for evaluating the effect of phage treatment on biofilm formation. The various parts are labeled as follows: 1, magnetic stirrer; 2, batch culture; 3, sterile medium reservoir; 4, peristaltic pump; 5, mDFR; 6, waste reservoir.

FIG. 3.

Effect of phage pretreatment of catheter surface on biofilm formation. ♦, mean log CFU/cm² of viable S. epidermidis 414 recovered from hydrogel-coated catheters; ▪, mean log CFU/cm² of viable S. epidermidis 414 recovered from hydrogel-coated catheters pretreated with phage 456; ○, mean log CFU/cm² of viable S. epidermidis 414 recovered from hydrogel-coated catheters pretreated with phage 456 (MHB supplemented with divalent cations). Error bars represent ±standard deviation (n = 3).

FIG. 4.

Effect of heat-inactivated phage and divalent cations on biofilm formation on catheter surface. ♦, mean log CFU/cm² of viable S. epidermidis 414 recovered from hydrogel-coated catheters; ▪, mean log CFU/cm² of viable S. epidermidis 414 recovered from hydrogel-coated catheters (MHB supplemented with divalent cations); ○, mean log CFU/cm² of viable S. epidermidis 414 recovered from hydrogel-coated catheters pretreated with heat-inactivated phage 456; □, mean log CFU/cm² of viable S. epidermidis 414 recovered from hydrogel-coated catheters pretreated with heat-inactivated phage 456 (MHB supplemented with divalent cations). Error bars represent ±standard deviation (n = 3).

FIG. 5.

Viable phage recovered from catheter lumens. ▪, mean log PFU/ml of viable phage 456 recovered from phage- pretreated hydrogel-coated catheters during biofilm formation; ○, mean log PFU/ml of viable phage 456 recovered from phage-pretreated hydrogel-coated catheters during biofilm formation (MHB supplemented with divalent cations); ▴, mean log PFU/ml of viable phage 456 recovered from phage-pretreated and subsequently serum-coated, hydrogel-coated catheters during biofilm formation (MHB supplemented with divalent cations). Error bars represent ±standard deviation (n = 3).

FIG. 6.

(A) Scanning electron micrograph of the surface of a section of a Lubri-sil hydrogel-coated all-silicone Foley catheter after biofilm formation by S. epidermidis 414 for 24 h (×3,000 magnification). Attached cells are clearly visible in large quantities on the surface. (B) Surface of a section of a Lubri-sil hydrogel-coated all-silicone Foley catheter pretreated with phage 456 after biofilm formation by S. epidermidis 414 for 24 h (×3,000 magnification) with divalent cation-supplemented MHB. No biofilm matrix or clusters of attached cells are visible (images represent typical fields of view).