title: Shaken or stirred?: Comparison of methods for dispersion of Mycoplasma pneumoniae aggregates for persistence in vivo.
abstract: Mycoplasma pneumoniae (Mpn), one of the smallest self-replicating prokaryotes, is known to readily adhere to host cells and to form aggregates in suspension. Having only one cell membrane and no cell wall, mycoplasmas present questions as to optimal aggregate disruption method while minimizing cell death in vitro. We compared conventional vortex mixing with other methods for disruption of bacterial aggregates and for its effect on cell viability.
  
  
  
  Strain UAB PO1, a clinical Mpn isolate, was dispersed using a conventional vortex mixer with or without nonionic detergent (0.1% and 0.01% Tween-20), a probe-type ultrasonicator, or repeated passage through a 27-gauge needle. The resulting suspensions were assayed for recoverable colony-forming units (CFU). Flow cytometric assays were carried out to examine particle size and membrane integrity with the transmembrane potential dye DiBAC4. Wet Scanning Transmission Electron Microscopy (Wet-STEM) was performed for high resolution imaging of the resultant cell suspensions. Additional Mpn strains and other human mollicute species were assayed in a similar manner. Mice were infected with either vortexed or sonicated UAB PO1 and bacterial persistence was examined via Mpn-specific 16S qPCR.
  
  
  
  Comparison between dispersion methods showed a 10-fold enrichment of recoverable Mpn CFU with sonication compared to other methods. Time-course analysis showed significantly lower bacterial CFU with vortexing compared to sonication at all time points. Flow cytometric analysis showed increased cellular membrane damage via DiBAC4staining in sonicated suspensions, but a decreased particle size. Wet-STEM imaging showed markedly improved dispersion with sonication compared to conventional vortex treatment, and surprisingly vortexing for 30s produced up to a 100-fold drop in CFU. Results similar to UAB PO1 were obtained with three additional Mpn strains and other Mollicutes species, although they exhibited differential susceptibilities to disaggregation by sonication. Finally, increased persistence of the organism in a mouse model of infection was observed using sonicated suspensions for initial infection.
  
  
  
  Sonication is superior to vortexing with or without nonionic detergent or repeated 27-gauge needle passage for dispersion of Mpn aggregates while preserving cell viability. Preparation of Mpn suspensions for in vivo experiments is best accomplished using brief sonication due to the dramatic increase in CFU produced by sonication. Dispersion methods may affect the final experimental results and should be an important consideration for future research involving mycoplasma species.
authors.affiliation: Dept of Pediatrics, 1720 2nd Ave South, Shelby 472, University of Alabama at Birmingham (UAB), Birmingham, AL 35294, USA. Electronic address: ahtotten@uab.edu.
authors.forename: Arthur H
authors.initials: AH
authors.lastname: Totten
authors.affiliation: Dept of Medicine, 1720 2nd Ave South, Shelby 472, University of Alabama at Birmingham (UAB), Birmingham, AL 35294, USA. Electronic address: lixiao@uabmc.edu.
authors.forename: Li
authors.initials: L
authors.lastname: Xiao
authors.affiliation: Dept of Pathology, Diagnostic Mycoplasma Laboratory, 1720 2nd Ave South, Shelby 407, University of Alabama at Birmingham (UAB), Birmingham, AL 35294, USA. Electronic address: dcrabb@uabmc.edu.
authors.forename: Donna M
authors.initials: DM
authors.lastname: Crabb
authors.affiliation: Dept of Pathology, Diagnostic Mycoplasma Laboratory, 1720 2nd Ave South, Shelby 407, University of Alabama at Birmingham (UAB), Birmingham, AL 35294, USA. Electronic address: amyratliff@uabmc.edu.
authors.forename: Amy E
authors.initials: AE
authors.lastname: Ratliff
authors.affiliation: Dept of Genetics, 720 20th Street South, Kaul Building 720A, University of Alabama at Birmingham, AL 35294, USA. Electronic address: dybvig@uab.edu.
authors.forename: Kevin
authors.initials: K
authors.lastname: Dybvig
authors.affiliation: Dept of Pathology, Diagnostic Mycoplasma Laboratory, 1720 2nd Ave South, Shelby 407, University of Alabama at Birmingham (UAB), Birmingham, AL 35294, USA. Electronic address: kwaites@uabmc.edu.
authors.forename: Ken B
authors.initials: KB
authors.lastname: Waites
authors.affiliation: Dept of Pediatrics, 1720 2nd Ave South, Shelby 472, University of Alabama at Birmingham (UAB), Birmingham, AL 35294, USA. Electronic address: PAtkinson@peds.uab.edu.
authors.forename: T Prescott
authors.initials: TP
authors.lastname: Atkinson
mesh_terms: D000818:Animals; D001422:Bacterial Adhesion; D001431:Bacteriological Techniques; D015169:Colony Count, Microbial; D004195:Disease Models, Animal; D005260:Female; D054884:Host-Pathogen Interactions; D008168:Lung / Q000382:microbiology; D051379:Mice; D008807:Mice, Inbred BALB C; D050296:Microbial Viability; D017348:Microscopy, Electron, Scanning Transmission; D009177:Mycoplasma pneumoniae / Q000145:classification / Q000302:isolation & purification*; D010316:Particle Size; D011019:Pneumonia, Mycoplasma / Q000175:diagnosis / Q000382:microbiology; D012329:RNA, Bacterial / Q000235:genetics / Q000302:isolation & purification*; D013010:Sonication; D008973:Tenericutes / Q000302:isolation & purification
chemical_list: D012329:RNA, Bacterial
keywords: Bacterial persistence; Dispersion; Mollicutes; Mycoplasma pneumoniae; Sonication