Mechanistic understanding of Phenyllactic acid mediated inhibition of quorum sensing and biofilm development in Pseudomonas aeruginosa.

Pseudomonas aeruginosa depends on its quorum sensing (QS) system for its virulence factors' production and biofilm formation. Biofilms of P. aeruginosa on the surface of indwelling catheters are often resistant to antibiotic therapy. Alternative approaches that employ QS inhibitors alone or in combination with antibiotics are being developed to tackle P. aeruginosa infections. Here, we have studied the mechanism of action of 3-Phenyllactic acid (PLA), a QS inhibitory compound produced by Lactobacillus species, against P. aeruginosa PAO1. Our study revealed that PLA inhibited the expression of virulence factors such as pyocyanin, protease, and rhamnolipids that are involved in the biofilm formation of P. aeruginosa PAO1. Swarming motility, another important criterion for biofilm formation of P. aeruginosa PAO1, was also inhibited by PLA. Gene expression, mass spectrometric, functional complementation assays, and in silico data indicated that the quorum quenching and biofilm inhibitory activities of PLA are attributed to its ability to interact with P. aeruginosa QS receptors. PLA antagonistically binds to QS receptors RhlR and PqsR with a higher affinity than its cognate ligands N-butyryl-L-homoserine lactone (C4-HSL) and 2-heptyl-3,4-dihydroxyquinoline (PQS; Pseudomonas quinolone signal). Using an in vivo intraperitoneal catheter-associated medaka fish infection model, we proved that PLA inhibited the initial attachment of P. aeruginosa PAO1 on implanted catheter tubes. Our in vitro and in vivo results revealed the potential of PLA as anti-biofilm compound against P. aeruginosa.

Faecal carriage rate of extended-spectrum ß-lactamase-producing Enterobacteriaceae in hospitalised patients and healthy asymptomatic individuals coming for health check-up.

The prevalence of extended-spectrum ß-lactamase-producing Enterobacteriaceae (ESBL-PE) in hospitalised and community patients is of significant public health concern. The aim of this study was to estimate the faecal carriage rate of ESBL-PE in hospitalised patients and healthy asymptomatic individuals coming for health check-up. Non-repetitive, consecutive stool samples from 480 adults (260 healthy individuals and 220 hospitalised patients) aged ≥18 years from November 2011 to July 2013 were screened using MacConkey agar supplemented with ceftazidime. All screen-positive isolates were identified to species level and were tested for ESBL production. Representative ESBL-PE isolates were subjected to susceptibility testing and multiplex ESBL PCR. The faecal carriage rate of ESBL-PE was found to be 62.7% among hospitalised patients and 33.8% among healthy asymptomatic individuals. The most common ESBL-PE was Escherichia coli (70.3% and 78.4% in hospitalised patients and healthy individuals, respectively), followed by Klebsiella pneumoniae (26.8% and 17.0%). ESBL-PE showed the highest sensitivity to carbapenems (85% and 100%, respectively), followed by amikacin (67.2% and 98%), cefoperazone/sulbactam (27.8% and 88.2%) and piperacillin/tazobactam (18% and 74.5%). Ciprofloxacin exhibited a high level of resistance among both groups. Molecular analysis for ESBL genes showed a predominance of the CTX-M gene. In conclusion, the faecal carriage rate of ESBL-PE among hospitalised patients was almost double that of healthy individuals. Carriage of carbapenem-resistant isolates is emerging among hospitalised patients. The spread of these organisms in the community merits radical measures to improve sanitation and implement antibiotic stewardship.