Auxotrophic Actinobacillus pleurpneumoniae grows in multispecies biofilms without the need for nicotinamide-adenine dinucleotide (NAD) supplementation.
BACKGROUND
Actinobacillus pleuropneumoniae is the etiologic agent of porcine contagious pleuropneumonia, which causes important worldwide economic losses in the swine industry. Several respiratory tract infections are associated with biofilm formation, and A. pleuropneumoniae has the ability to form biofilms in vitro. Biofilms are structured communities of bacterial cells enclosed in a self-produced polymer matrix that are attached to an abiotic or biotic surface. Virtually all bacteria can grow as a biofilm, and multi-species biofilms are the most common form of microbial growth in nature. The goal of this study was to determine the ability of A. pleuropneumoniae to form multi-species biofilms with other bacteria frequently founded in pig farms, in the absence of pyridine compounds (nicotinamide mononucleotide [NMN], nicotinamide riboside [NR] or nicotinamide adenine dinucleotide [NAD]) that are essential for the growth of A. pleuropneumoniae.


RESULTS
For the biofilm assay, strain 719, a field isolate of A. pleuropneumoniae serovar 1, was mixed with swine isolates of Streptococcus suis, Bordetella bronchiseptica, Pasteurella multocida, Staphylococcus aureus or Escherichia coli, and deposited in 96-well microtiter plates. Based on the CFU results, A. pleuropneumoniae was able to grow with every species tested in the absence of pyridine compounds in the culture media. Interestingly, A. pleuropneumoniae was also able to form strong biofilms when mixed with S. suis, B. bronchiseptica or S. aureus. In the presence of E. coli, A. pleuropneumoniae only formed a weak biofilm. The live and dead populations, and the matrix composition of multi-species biofilms were also characterized using fluorescent markers and enzyme treatments. The results indicated that poly-N-acetyl-glucosamine remains the primary component responsible for the biofilm structure.


CONCLUSIONS
In conclusion, A. pleuropneumoniae apparently is able to satisfy the requirement of pyridine compounds through of other swine pathogens by cross-feeding, which enables A. pleuropneumoniae to grow and form multi-species biofilms.
['Loera-Muro|Abraham|A|', 'Jacques|Mario|M|', 'Avelar-González|Francisco J|FJ|', 'Labrie|Josée|J|', 'Tremblay|Yannick D N|YD|', 'Oropeza-Navarro|Ricardo|R|', 'Guerrero-Barrera|Alma L|AL|']
D000117:Acetylglucosamine D000189:Actinobacillus Infections D016977:Actinobacillus pleuropneumoniae D000818:Animals D018441:Biofilms D016950:Bordetella bronchiseptica D003470:Culture Media D003850:Deoxyribonuclease I D019286:Endopeptidase K D004926:Escherichia coli D017404:In Situ Hybridization, Fluorescence D018613:Microscopy, Confocal D009243:NAD D009536:Niacinamide D009537:Nicotinamide Mononucleotide D016979:Pasteurella multocida D011725:Pyridines D011726:Pyridinium Compounds D013045:Species Specificity D013211:Staphylococcus aureus D013234:Stem Cells D017011:Streptococcus suis D013552:Swine D013553:Swine Diseases
Biofilms Actinobacillus pleuropneumoniae Pyridine compounds Streptococcus suis Bordetella bronchiseptica Pasteurella multocida Staphylococcus aureus Escherichia coli