The Cotton Rat as a Model for Staphylococcus aureus Nasal Colonization in Humans - Bacterial Pathogenesis: Methods and Protocols - page 237

Table 3
Recoverable Native Aerobic Flora from Uninstilled and Staphylococcus
aureus -Instilled Cotton Rats Noses

Bacteria ab

Number
colonized/number
instilled

Mean or individual
CFUs recovered

Uninstilled cotton rats
Gram-negative of the
enterobaceriacea family c

5/5 13,390

Streptococcus species c

5/5 730

Streptococcus thoralensis 4/5 810

Staphylococcus muscae d

3/5 128

Staphylococcus xylosus 2/5 1000 and 5

Aerobacter viridans 2/5 160 and 10

Non-typeable Gram+ e

1/5 80

S. aureus -instilled cotton rats
Gram-negative of the
enterobaceriacea family

4/5 22,512

Streptococcus species 5/5 800

Streptococcus thoralensis 5/5 56

Staphylococcus muscae 5/5 71

Staphylococcus xylosus 0/5 n/a f

Aerobacter viridans 4/5 26

Non-typeable Gram+ 3/5 47

S. aureus (instilled) g 5/5 1179

a Bacteria was recovered on blood agar and Chromagar Staph aureus at 37 ºC.
b Bacterial identification confirmed by comparative DNA sequence analysis Accugenix Inc.
(Newark, DE).
c Comparable DNA sequence not available in database.
d Grows as a small purple colony of Chromagar Staph aureus.
e Was not amenable to comparative DNA sequence analysis.
f Not applicable.
g S. aureus strain MBT 5040.

each nasal supernatant 1:10 in PBS by adding 75 μL of supernatant to 675 μL of
PBS and then plate 75 μL of both the primary supernatant and the 1:10 dilution
on separate agar plates to ensure that the resulting colony count is within the
countable range. This will require twice as many agar plates.

Acknowledgements
We acknowledge of the excellent technical assistance of Tanya Chanturiya
and Jimmy Mond for critical reading of this manuscript.