A rapid method combining immunofluorescence and flow cytometry for improved understanding of competitive interactions between lactic acid bacteria (LAB) and methicillin-resistant S. aureus (MRSA) in mixed culture.
The increasing frequency of methicillin-resistant Staphylococcus aureus (MRSA) infections in hospital and community settings highlights the need for effective anti-MRSA agents that will not contribute to the growing problem of antibiotic resistance. Lactic acid bacteria (LAB) are known to exclude various pathogens through multiple mechanisms. In vitro models studying interactions of pathogens and LAB in mixed cultures use selective agar plates to quantify changes in target populations. We applied commercially available S. aureus-specific polyclonal antibodies conjugated with fluorescein isothiocyanate (FITC) for this purpose, producing a bright green signal that clearly differentiates S. aureus from LAB species when mixed cultures are analyzed by flow cytometry and fluorescent microscopy. Flow cytometry of mixed cultures revealed a much larger population of MRSA cells than was detectable using selective agar plates. To our knowledge, this is the first time immunofluorescent flow cytometry has been applied to the study of competitive exclusion in mixed bacterial populations over time.
Schellenberg
John
J
Département des sciences biologiques, Université du Québec à Montréal, Pavillon des Sciences, 1200, rue St. Alexandre, Montréal, Québec H3B 3H5 Canada. schellenberg.john@courrier.uqam.ca
Smoragiewicz
Wanda
W
Karska-Wysocki
Barbara
B
D000818:Animals; D000907:Antibodies, Bacterial / Q000737:chemistry; D001431:Bacteriological Techniques / Q000379:methods; D018920:Coculture Techniques; D005434:Flow Cytometry / Q000379:methods*; D016650:Fluorescein-5-isothiocyanate / Q000737:chemistry; D005455:Fluorescent Antibody Technique / Q000379:methods; D006801:Humans; D007778:Lactobacillus / Q000254:growth & development*; D016106:Methicillin Resistance; D008856:Microscopy, Fluorescence; D019936:Probiotics / Q000494:pharmacology; D013211:Staphylococcus aureus / Q000187:drug effects / Q000254:growth & development*
D000907:Antibodies, Bacterial; D016650:Fluorescein-5-isothiocyanate