Unwashed and Washed Hand Prints

With the emergence of antibiotic resistance bacteria and discoveries of new and emerging viral diseases the importance of hand washing has become increasingly more important in disease prevention.  


Bacterial handprints done durning the summer in a Stem Class.  The unwashed hands, washed with soap and water, showed environmental contamination of both bacterial and yeast.  Hand prints were done using large TSA Kirby Bauer plates.  Plates were incubated at 37 degree's C for 24 hrs then 48 hrs at room temperature and finally held at refrigerated temperatures for a week or longer.

Unwashed bacterial hand print showing large colonies of Bacillus mycodies (large rhizoid colony on the left) and other Bacillus spp as well as numerous environmental yeast (yellow) and normal body flora (white circular colonies, Staph spp).  Seeing Bacillus mycodies in the warmer months is unusual and normally seen in the cooler months.

Close up of the Bacillus mycodies seen in the unwashed hand.  This specific Bacillus is rhzoid and always bends/swirls in the same direction and is a characteristic  morphology for this bacterial species

Enlarged view of same hand after hand washing.  Notice that the hand print has fewer Bacillus spp and compared to the unwashed hand print.

Bacterial Hand Print before hand washing.  Bacillus spp are the only colonies that grew on this hand print leading to what looks like a hulk hand.  Bacillus tend to grow faster, spreads and can have antibiotic properties that inhibit the growth of other bacteria/yeast.

Same hand after hand washing.  Bacillus spp is mostly gone and replace with normal body flora with a few environmental bacteria/yeast

Below are images of interesting colony morphologies seen on varies plates from unwashed hand prints.  Several things to note is that these prints were done in the warm summer months which is when we see the more vibrant colors form the environmental yeasts.  These students also came from different areas, some form the coast, mountain's, as well as farming communities:

Branching fungal colony, red yeast (Rhodutrula) seen bleeding into another colony which is more then likely a Bacillus spp (brain like colony), yellow environmental yeast, as well as white Stahpylococcus spp.  Interesting note is that this was seen on the finger print from a student that worked on a farm raising chickens and the student had just come from work.


(a) Rhodutrula was subcultured.  There was no growth at 37 degree's C but good growth seen at 4 degree's C

(a)

Numerous yellow yeast and white Stahpylococcus spp colonies.  Interesting yellow basket shaped growth in the upper corner, possible yeast or Bacillus spp,

Yellow colonies were (a) subcultured and grew at 37 degree's C as well as 4 degree's C and Gram stained (b).  Gram stain showed large oval budding cells, arrangement looked like Mickey mouse ears.

(a)

(b)

Gram stain was done on the light orange colonies, G+ rods, and was seen heavily through out this hand print.

Light orange colonies were subcultured (a) and (b) gram stained.  Colonies grew at 37 degree's C after 24 hrs and had a G+ gram stain with showing thin G+ rods.

(a)

(b)

Colorful mix of yeast (yellow) or Micrococcus (smaller colonies), Staphylococcus (white) and various shades of orange (bright orange being Rhodutrula) on this finger print.  Note:  the large yellow colonies continue to grow at refrigerated temperatures.

As can be seen by both sets of unwashed and washed bacterial hand prints environmental bacteria and yeast are reduced in the washed print.  The washed print mainly has normal body flora (Staphylococcus spp) with a few colonies of yeast and or Bacillus spp.  The physical act of scrubbing seems to be removing the environmental bacteria/yeast, especially Bacillus, as well as dead skin.  What is left in a washed hand is exposed bacteria normally found on the exposed skin.

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All images copyright Sturm.