Microbiology encompasses the study of bacteria, parasites, viruses, and fungi. Bacteriology includes identifying bacterial characteristics, appropriate specimen collection, aseptic technique, culture techniques, colony characteristics, gram staining, and common bacterial infections like bacteremia, meningitis, and those caused by Staphylococcus, Streptococcus, Enterococcus, Candida, Cryptococcus, and E. coli. Identification requires observing bacterial growth, morphology, hemolysis, gram reaction, and automated methods.

1. Microbiology Antonio Rivas PA-C Feb 2008

2. Microbiology Clinical microbiology encompasses Bacteriology Parasitology Virology Mycology

3. Bacteriology Characteristics of bacteria Multiply by fission Grow in colonies Morphology Coccus Bacillus Spiral Growth patterns

4. Specimen collection Collect before antimicrobials are given Specimen collected where the organism is most likely to be found w/o external contamination Stage of the disease Enteric pathogens are present in higher numbers during the acute or diarrheal phase of the infection Sufficient quantity of specimen Prompt delivery to the lab

5. Aseptic Technique

6. Techniques Culture

7. Culture Techniques

8. Bacteriological Growth Media Agar plates contain different components that enhance or inhibit the growth of certain microorganisms Examples: MAC-selective media - inhibits Gram Positive organism HE- selective media- inhibits Gram negative organism

9. Bacteriological Growth Media

10. Incubation - Plates are incubated for : 24-48 hrs at different temperature and O2 concentration- - Most human pathogens grow best at 35-37 degree C

11. Culture Techniques Observing culture after 24 hours Colony characteristics Presence (or absence) of hemolysis Staphylococcus aureus Beta hemolyticus strept.

12. Colony Characteristics Colony size, shape, moist or dry, color, smell Pseudomonas sp. Smells like grapes Neisseria gonorrhea smells like sweaty tennis shoe Shigella is mucoid and purple Presence of hemolysis in blood agar plate (Strep.pyogenes-throat inf.-beta hemolysis) Beta-hemolysis: Lysis of the red cell present in the media showing clear area around the bacterial growth

13. Automated ID

14. Gram Stain Bacterial species divided into two groups according to how they take Gram Stain Gram positive : take up the crystal violet basic stain (stain purple) Gram negative : allow the crystal violet to easily washout with acetone and take up the Safranin dye (stain pink) Related to the cell membrane composition

15. Gram Stain Important for Bacterial identification Antibiotic susceptibility testing Preparing a smear From a swab From a culture

16. Preparing the Bacterial Smear Heat-fixing the smear Smear must be dry Affixes bacteria to slide Do not use excessive heat

17. Gram Stain Primary stain Gram’s iodine Mordant Decolorizer Counterstain

18. Observe the Stained Smear Oil immersion Gram reactions Gram (+) -> purple Gram (-) -> pink

19. Microbiology Bacteremia : transient release of bacteria to the blood stream, indicates the presence of a focus of disease Septicemia or Sepsis : a situation in which bacteria and their products are causing harm to the host Terms are used interchangeable

20. Portals of entry for septicemia: GU Respiratory Abscesses Surgical wound infections Biliary tract Other sites Organisms most commonly isolated from blood are: Gram positive cocci Coagulase neg staphylococci Staphylococcus aureus Enterococcus sp.

21. Meningitis: infection in the subarachnoid space, between the Pia-mater and the Arachnoid Dx by PE, CSF analyisis, and cultures Hematogenous spread Children <5 years Haemophilus influenza Neonates Group B streptococci E.coli Listeria sp. Most common bacteria causing meningitis in children age 6 years and up Haemophilus influenza Neisseria meningitidis Streptococcus pneumoniae

22. Meningitis in adults Neisseria meningitidis(young adults crowded conditions) Pneumococci Listeria monocytogenes Staphylococcus aureus

23. Staphylococcus saprophyticus Gram positive cocci Second cause of UTI in young females after E.coli Symptoms : Burning when urinating Increased urge to urinate Dripping effect Razor like pain in the lower abdomen and during intercourse Treated with Quinolones in the US

24. Enterococcus faecalis Gram positive bacilli Inhabitant in GI tract humans and animals Life threatening nosocomial infections High level antibiotic resistance Can cause endocarditis, bladder, prostate and epididymal infections

25. Streptococcus pyogenes Gram positive cocci in chains Group A, beta hemolytic Strept throat-pharyngitis Impetigo Cellulitis Necrotizing fasciitis Toxic shock Rheumatic fever Glomerulonephritis Sensitive to penicillin

26. Candida albicans Yeast, fungi Opportunistic oral and genital infection in immunocompromised patients Live in human mouth and GI May occur in blood Thrush – immunocompromised

27. Cryptococcus neoformans Encapsulated yeast-like fungus Cryptococcal meningitis in immunocompromissed patients India ink stain used for Dx in CSF

28. E.coli Gram negative rod Virulent strains can cause gastroenteritis, UTI, neonatal meningitis Ascending UTI with fecal contamination