Introduction to Microbiology & Handwashing Beverley Gallacher SOHCS

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

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

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

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

Examples of bacteria Staphyococcus aureus Escherichia coli Salmonella typhimurium

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

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

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

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

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

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

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

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)

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

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

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

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

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)

References Rahman M & Chattopadhyay B (2000) Handashing: unanswered questions and compliance J Hosp Infection 45 249-50 Mims C et al (1998) Medical Microbiology Mosby International Ltd. London http://www.engenderhealth.org/ip/index.html Handwashing http://www.engenderhealth.org/ip/handwash/index.html