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Unit #5E – Clinical Laboratory Testing – Basic Clinical Microbiology Includes study of bacteria (bacteriology), parasites (parasitology), viruses (virology) and fungi (mycology) Cecile Sanders, M.Ed., MLS(ASCP) Unit #5E – Clinical Laboratory Testing - Basic Clinical Microbiology – Bacteriology Study of a large diverse group of single celled prokaryote microorganisms which multiply by fission to form a “colony” (on solid media), which can be observed for characteristic appearance. Bacteria cannot be seen with the naked eye. They can only be seen after staining them with special dyes and observing them under a microscope. Unit #5E – Clinical Laboratory Testing - Basic Clinical Microbiology – Bacterial Microscopic Morphology Coccus - round (cocci = plural) – Example: Streps, staphs, Neisseria Diplococcus - cocci in pairs (diplococci = plural) – Example: Strep. pneumoniae Bacillus or rods - parallel sides (bacilli = plural) – Example: E. coli Spirochetes - curved or spiral organisms – Example: Treponema pallidum Unit #5E – Clinical Laboratory Testing - Basic Clinical Microbiology – Cocci/Diplococci – Bacilli/Rods Unit #5E – Clinical Laboratory Testing - Basic Clinical Microbiology – Spirochetes Unit #5E – Clinical Laboratory Testing - Basic Clinical Microbiology – Gram Stain http://www.uphs.upenn.edu/bugdrug/antibiotic_manual/Gram3.htm Most bacteria fall into one of two categories: – Gram-positive = microorganisms that stain purple Example: Streps, staphs – Gram-negative = microorganisms that stain pink or red - Example: E. coli, Neisseria Purpose of Gram Stain: Provides valuable information for physician to start antibiotic therapy, as antibiotics act differently on gram (+) vs. gram (-) organisms Unit #5E – Clinical Laboratory Testing - Basic Clinical Microbiology – Gram Positive Cocci Unit #5E – Clinical Laboratory Testing - Basic Clinical Microbiology – Gram Positive Bacilli – Gram Negative Cocci Unit #5E – Clinical Laboratory Testing - Basic Clinical Microbiology – Gram Negative Bacilli Unit #5E – Clinical Laboratory Testing - Basic Clinical Microbiology – Clinical Bacteriology Terms Pathogens / pathogenic – capable of causing disease Communicable - capable of being transferred from one person to another Normal flora - natural micro-inhabitants of the body Opportunists / Opportunistic pathogens – organisms that only cause disease in compromised individuals Antibiotic susceptibility testing – tests for sensitivity of organism against various antibiotics Unit #5E – Clinical Laboratory Testing - Basic Clinical Microbiology Specimen collection - Body sites / fluids cultured to grow microorganisms – Fastidious organisms - require special medium / conditions to grow – Aerobic - organisms which require oxygen to grow or live – Anaerobic - organisms which live and grow only in absence of oxygen. http://www.shellab.com/bactron.html Unit #5E – Clinical Laboratory Testing - Basic Clinical Microbiology – Microbiological Safety Cabinets - H(igh) E(fficiency) P(article) A(ir filter) “HEPA” Air moves away from worker, over specimen, through filter, and vented to outside http://www.terrauniversal.com/laminarflow-hoods/laboratory-hoods-x.php Unit #5E – Clinical Laboratory Testing - Basic Clinical Microbiology – Disinfectants - chemicals used on working areas to kill or control growth of organisms in their active or vegetative stages (NOT resting stages, such as spores). Some harsh disinfectants will kill spores, too EXAMPLE: 10% bleach, phenols – Antiseptics - chemicals used to control microorganisms on living tissue EXAMPLE: 70% isoprophyl alcohol, Betadine Unit #5E – Clinical Laboratory Testing - Basic Clinical Microbiology – Sterilization - methods used to kill all organisms and their resting stages EXAMPLE: Autoclaving Unit #5E – Clinical Laboratory Testing - Basic Clinical Microbiology Processing of Specimens – Agars - solid medium made of seaweed extract; bacteria grow on these agars and appear as small to large dots Enrichment agars for growth – contain extra nutrients – Example: Blood Agar Unit #5E – Clinical Laboratory Testing - Basic Clinical Microbiology Differential agars – differentiate organisms by color or growth pattern – Example: MacConkey Agar – inhibits the growth of gram positive organisms while allowing gram negative organisms to grow Unit #5E – Clinical Laboratory Testing - Basic Clinical Microbiology Selective agars – Inhibit the growth of certain microorganisms while allowing other organisms to grow Unit #5E – Clinical Laboratory Testing - Basic Clinical Microbiology Antibiotic Sensitivity (Susceptibility) Testing – Kirby-Bauer Method – MIC – Minimum Inhibitory Concentration – Provides information on weakest dose of antibiotic that would be effective Unit #5E – Clinical Laboratory Testing - Basic Clinical Microbiology Parasitology – – Common human parasites Enterobius vermicularis “Pin Worm” Giardia lamblia Trichomonas vaginalis – O & P (Ova and Parasites) - Detection of Intestinal Parasites Helminths - flatworms, round worms, flukes, or hookworms Amoeba in cyst or trophozoite stage Unit #5E – Clinical Laboratory Testing - Basic Clinical Microbiology Life cycle of Giardia Unit #5E – Clinical Laboratory Testing - Basic Clinical Microbiology Life cycle of Ascaris (round worm) Unit #5E – Clinical Laboratory Testing - Basic Clinical Microbiology Life cycle of amoeba parasite Unit #5E – Clinical Laboratory Testing - Basic Clinical Microbiology Stool samples - usually collected X3 and at least 24 hours apart Most common preservative = ParaPak (has two vials, one with Polyvinyl Alcohol [PVA] and the other with formalin) Unit #5E – Clinical Laboratory Testing - Basic Clinical Microbiology “Wet Prep” for detection of Trichomonas vaginalis Unit #5E – Clinical Laboratory Testing - Basic Clinical Microbiology Virology – Characteristics – Intracellular parasites Too small to be seen with light microscopy Contain either DNA or RNA, but not both Common viral infections include the common cold, influenza, measles, chickenpox, hepatitis. Others viral infections include polio, HIV, bird flu, West Nile virus. Unit #5E – Clinical Laboratory Testing - Basic Clinical Microbiology – Virus Detection Most detected by testing for specific antibodies (review #5C PowerPoint) Some viruses can be cultured – Anatomy of a virus particle – check this website: http://www.freebase.com/view/wikipedia/im ages/en_id/16233765 Unit #5E – Clinical Laboratory Testing - Basic Clinical Microbiology Mycology - study of fungus. Infection with fungus is called a mycosis – Types of Specimens for Fungal Cultures – Skin scrapings Nail clippings Scalp scrapings Sputum Blood Bone marrow Lung biopsies Fungi (plural of fungus) are either “molds” or “yeasts” Unit #5E – Clinical Laboratory Testing - Basic Clinical Microbiology – Molds - filamentous fungi Assorted molds culture Unit #5E – Clinical Laboratory Testing - Basic Clinical Microbiology – Yeasts - unicellular Usually egg-shaped Reproduce with buds Pasty in appearance Unit #5E – Clinical Laboratory Testing - Basic Clinical Microbiology Photos from clinical microbiology laboratories: Unit #5E – Clinical Laboratory Testing - Basic Clinical Microbiology Resources – Basic Clinical Laboratory Techniques, Estridge and Reynolds, Thomson/Delmar Learning, Fifth Edition, 2008 – http://www.uphs.upenn.edu/bugdrug/antibiotic_ma nual/Gram3.htm – http://www.shellab.com/bactron.html – http://www.terrauniversal.com/products/glovebox es/accessories_gbx/filtrationmodules.php – http://www.freebase.com/view/wikipedia/images/e n_id/16233765
