Effect of sub-inhibitory concentrations of tigecycline and ertapenem on the adherence of pseudomonas aeruginosa to polyvinyl chloride intravenous catheters

Abstract

Background: Sub-inhibitory concentration refers to any concentration of an antibiotic that is below the minimum inhibitory concentration. Although sub-inhibitory concentrations of many antibiotics are insufficient to kill or inhibit bacterial growth; accumulating evidence suggests that they are able to trigger some important changes within bacterial virulence factors. The objective of the present study was to investigate the effects of sub-inhibitory concentrations of Tigecycline and Ertapenem on the adherence of Pseudomonas aeruginosa to intra-venous catheters. Materials & Methods: Minimum inhibitory concentrations and Sub-inhibitory concentrations of Tigecycline and Ertapenem on clinical strains of Pseudomonas aeruginosa, Staphylococcus aureus, and coagulase-negative Staphylococci were determined using the macro-broth dilution method using a freshly prepared Mueller Hinton Broth. Bacterial adherence to catheters was quantified via a sonicator bath and subsequent plating of the adhered and non-adhered bacteria to Intra-venous catheters were performed. Results: Generally, sub-inhibitory concentrations of Tigecycline significantly decreased the adherence of Pseudomonas aeruginosa (10 strains) to Intra-venous catheters; whereas, sub-inhibitory concentrations of Ertapenem considerably increased adherence of Pseudomonas aeruginosa (10 strains) to intra-venous catheters. Furthermore, this research work revealed that bacterial adherence profile is affected in response to the sub-inhibitory concentrations of antibiotics regardless whether the bacteria are resistant or susceptible to Tigecycline or Ertapenem. Discussion: The obtained results suggest that Tigecycline and Ertapenem at the subinhibitory concentrations trigger changes of the outermost architecture of P.aeruginosa that results in an increase or decrease of bacterial adherence to intra-venous catheters. Finally, further genotyping techniques should be performed in order to identify the adhesion genes that are influenced by the sub-inhibitory concentrations of Tigecycline and Ertapenem.