title: Pseudomonas aeruginosa inhibits in-vitro Candida biofilm development.
abstract: BACKGROUND
  Elucidation of the communal behavior of microbes in mixed species biofilms may have a major impact on understanding infectious diseases and for the therapeutics. Although, the structure and the properties of monospecies biofilms and their role in disease have been extensively studied during the last decade, the interactions within mixed biofilms consisting of bacteria and fungi such as Candida spp. have not been illustrated in depth. Hence, the aim of this study was to evaluate the interspecies interactions of Pseudomonas aeruginosa and six different species of Candida comprising C. albicans, C. glabrata, C. krusei, C. tropicalis, C. parapsilosis, and C. dubliniensis in dual species biofilm development.
  
  
  RESULTS
  A significant reduction in colony forming units (CFU) of C. parapsilosis (90 min), C. albicans and C. tropicalis (90 min, 24 h and 48 h), C. dubliniensis and C. glabrata, (24 h and 48 h) was noted when co-cultured with P. aeruginosa in comparison to their monospecies counterparts (P < 0.05). A simultaneous significant reduction in P. aeruginosa numbers grown with C. albicans (90 min and 48 h), C. krusei (90 min, 24 h and 48 h),C. glabrata, (24 h and 48 h), and an elevation of P. aeruginosa numbers co-cultured with C. tropicalis (48 h) was noted (P < 0.05). When data from all Candida spp. and P. aeruginosa were pooled, highly significant mutual inhibition of biofilm formation was noted (Candida P < 0.001, P. aeruginosa P < 0.01). Scanning Electron Microscopy (SEM) and Confocal Laser Scanning Microscopy (CLSM) analyses confirmed scanty architecture in dual species biofilm in spite of dense colonization in monospecies counterparts.
  
  
  CONCLUSIONS
  P. aeruginosa and Candida in a dual species environment mutually suppress biofilm development, both quantitatively and qualitatively. These findings provide a foundation to clarify the molecular basis of bacterial-fungal interactions, and to understand the pathobiology of mixed bacterial-fungal infections.
authors.affiliation: Faculty of Dentistry, The University of Hong Kong, Oral Biosciences, 5/F, Prince Phillip Dental Hospital, 34, Hospital Road, Sai Ying Pun, Hong Kong.
authors.forename: H M H N
authors.initials: HM
authors.lastname: Bandara
authors.forename: J Y Y
authors.initials: JY
authors.lastname: Yau
authors.forename: R M
authors.initials: RM
authors.lastname: Watt
authors.forename: L J
authors.initials: LJ
authors.lastname: Jin
authors.forename: L P
authors.initials: LP
authors.lastname: Samaranayake
mesh_terms: D000898:Antibiosis; D018441:Biofilms / Q000254:growth & development*; D002175:Candida / Q000254:growth & development / Q000502:physiology*; D018920:Coculture Techniques; D015169:Colony Count, Microbial; D050296:Microbial Viability; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D011550:Pseudomonas aeruginosa / Q000254:growth & development / Q000502:physiology*