1. Introduction to Microbiology & Handwashing
Beverley Gallacher SOHCS

2. Learning Outcomes
Describe the main classifications of bacteria, naming medically important examples
Describe the role of “normal flora” (commensals)
Describe viruses and how they are classified
Identify the most important route of transmission for microorganisms
Describe the “Ayliffe” technique for handwashing

3. Organisms that cause infectious diseases can be grouped into 6 main categories:
Arthropods
Helminths
Protozoa
Fungi
Bacteria
Viruses

4. Characteristics of viruses
Sub cellular particles
Nucleic acid core DNA RNA
Protein coat
Require the “machinery” of a living cell to replicate
Some have an outer envelope

5. Classification based on:
Presence of envelope
Nucleic acid type - DNA or RNA
“Shape” of coat - icosahedral, helical, complex
Organism affected by virus, e.g.animal,plant, bacteria
Tissue / organ affected by the virus

6. Examples of bacteria Staphyococcus aureus Escherichia coli
Salmonella typhimurium

7. Bacterial classification
Shape: morphology:
Metabolism:
Aerobic (Mycobacterium tuberculosis)
Anaerobic - Clostridium
Facultative anaerobe (E coli.)
Gram stain:
positive or negative

8. Diplococci Streptococci Staphylococci Streptococcus pyogenes
Plane of division
Diplococci
Streptococci
Streptococcus pyogenes
Tortora G.J. Funke B.R. & Case C L. (1998)
Staphylococci
Staphylococcus aureus

9. Single bacillus Diplobacilli Streptobacilli Coccobacillus
Tortora G.J. Funke B.R. & Case C L. (1998)

10. Gram Stain
Coloured stains are applied to bacteria in the Gram stain process.
Two different colours can arise:
Red Gram - Purple Gram +
Cell wall
Cell membrane

11. Medically important bacteria
Clostridium difficile
Staphylococcus aureus
Streptococcus pyogenes
Clostridium tetani
Gram +
Escherichia coli
Pseudomonas aeruginosa
Salmonella spp.
Gram -
Campylobacter spp.

12. Normal flora Commensalism In commensalism one species of organism
uses the body of
a larger species
A collection of species are
routinely found in the normal
healthy individual

13. Normal Flora Where do they come from?
The environment. Acquired from birth
How many are there?
Estimated 10 cells in human body, with 10 bacteria associated with them
Where are they found?
Parts of the body that are exposed to or communicate with the external environment

14. The Role of Normal flora
Prevent colonisation by potential pathogens. They compete for resources, attachment sites with potential pathogens
“The sheer number of bacteria present in the normal flora of the intestine means that almost all of the available ecological niches become occupied; these species therefore outcompete others for living space”
“Gut bacteria……also produce B vitamins and vitamin K in amounts that are large enough to be valuable if the diet is deficient” (Mims et al 1998)

15. Some organisms that make up the normal flora
Staphylococcus aureus
Staphylococcus epidermidis
Escherichia coli
Clostridium difficile
Pseudomonas aeruginosa
Klebsiella spp
Salmonella spp
Candida albicans (a yeast)
Found on
the skin

16. Infection Control is to prevent microorganisms
The basic purpose of
Infection Control is to
prevent microorganisms
reaching a susceptible site
on a patient in sufficient
numbers or of sufficient
virulence to cause an
infection

17. Patient - to patient
transmission via the
hands of the staff
is regarded as the
most important route
Handwashing is the single most important means of preventing the spread of infection

20. Contact with different
Hands should be washed
Before
Invasive procedures
Caring for patient in high
risk groups,
e.g.immunocompromised
and newborns
Preparing handling or
eating food
Rahman M & Chattopadhyay B (2000)
After:
Hands visibly soiled or dirty
Contact with mucous membrane,
blood or body fluids
Touching contaminated objects,
linen or waste
Contact with patient in source
isolation or an infected or
colonised patient
Visiting toilet or taking patient to
toilet
Removing gloves
Before & After
Touching wounds
Contact with different
patients in high risk
areas

21. Hand Rub “The Hand Hygiene Liaison Group now
recommends the use of alcohol glycerol
handrubs between every patient contact
when there has not been actual soiling
of hands” Teare L et al (2000)

22. References
Rahman M & Chattopadhyay B (2000) Handashing: unanswered questions and compliance J Hosp Infection
Mims C et al (1998) Medical Microbiology Mosby International Ltd. London
Handwashing