Microbiology Lesson 1: Introduction to Microbiology

1. 45 Microbiology Lesson 1: Introduction to Microbiology

2. Lesson Objectives Upon completion of this lesson, students should be able to: • Define and spell the terms to learn for this chapter. • Define microbiology and its importance in patient care. • Explain how microorganisms are classified.

3. Lesson Objectives Upon completion of this lesson, students should be able to: • Explain the differences among bacteria, viruses, protozoa, fungi, and parasites. • Identify three different shapes of bacteria and a disease caused by each. • Identify a disease caused by each of the five categories of pathogens.

4. Field of Microbiology • Microbiology • Study of microorganisms (living organisms too small to be seen with naked eye) • Van Leeuwenhoek's invention of microscope in 1674 allowed people to observe microbes for the first time

5. Field of Microbiology • Louis Pasteur, father of microbiology, developed methods for culturing and identifying microbes in the laboratory • Study of microorganisms has advanced the field of medicine; allows individuals to live longer, healthier lives • To successfully treat a patient, it is important to first discover the exact cause of the problem.

6. Field of Microbiology • Offending microorganisms may be identified by evaluating body fluid samples, then effective treatment is prescribed.

7. Field of Microbiology • Bacteria • Not all bacteria are bad. • Bacteria in the environment help us to decompose and recycle waste. • Normal flora on our bodies consist of beneficial bacteria that help us resist pathogens.

8. Field of Microbiology • Bacteria • Bacterium that is harmless in one area may be pathogenic in another, especially in large amounts or in an area that is normally sterile.

9. Role of the Medical Assistant in Microbiology • MAs frequently come in contact with blood and body fluids. • Collecting and preparing specimens • Observe standard precautions to prevent contamination and the spread of infection. • Safety must come above all else.

10. Classifications of Microorganisms • Pathogens (able to cause disease) • Only 1% to 2% are pathogenic • Nonpathogens (not able to cause disease) • Most microbes are nonpathogenic (98% to 99%)

11. Classifications of Microorganisms • Naming Microorganisms • Binomial system used to name all living organisms—animals, plants, bacteria, fungi, and protozoa • Genus (always capitalized) • Species (lowercase) • For example, organism that causes strep throat is known as Streptococcus pyogenes

12. Classifications of Microorganisms • Naming Microorganisms • Convention • Spell out entire name at first mention; then abbreviate with initial of genus followed by species name (e.g., S. pyogenes). • MA not expected to learn all genus and species names

13. Classifications of Microorganisms • Naming Microorganisms • Understanding system of nomenclature is necessary when MA receives lab reports over the phone or reads patient chart

14. Classifications of Microorganisms • Retention of Dyes • Bacteria characterized by their reactions to certain stains • Stain • Dye used in coloring microorganisms to allow for visibility under a microscope

15. Classifications of Microorganisms • Retention of Dyes • Gram stain • A commonly used method of staining bacteria • Gram-positive bacterium retains the violet color of the stain used in the staining of the microorganism

16. FIGURE 45-1 Gram positive S. pyogenes bacteria in chains.

17. Classifications of Microorganisms • Retention of Dyes • More common gram-positive bacteria are Staphylococcus aureus and Streptococcus pneumoniae • Gram-negative bacterium has pink color of counterstain used in Gram's method of staining microorganisms

18. Classifications of Microorganisms • Retention of Dyes • Most common gram-negative bacteria are Escherichiacoli, Neisseriagonorrhoeae, and Salmonellatyphimurium

19. FIGURE 45-2 Gram negative N. gonorrhoeae.Kwangshin Kim/Getty Images

20. Classifications of Microorganisms • Retention of Dyes • Some organisms do not stain well with Gram stain and require a special stain (e.g., acid-fast stain used for the organism that causes tuberculosis).

21. Classifications of Microorganisms • Use of Oxygen • Aerobes survive in an oxygen-rich environment. • Anaerobes die in the presence of oxygen.

22. Classifications of Microorganisms • Use of Oxygen • Facultative anaerobes • Flexible and can live with some oxygen • Successful culturing requires understanding of oxygen requirements of bacteria • To grow and identify sample of organism causing disease, provide proper oxygen, moisture, nutrition, and temperature in laboratory setting

23. Classifications of Microorganisms • Other Identifying Characteristics • Differences in cell structures (presence or absence of organelles) • If capable of movement, their means of motility is unique to specific categories of microorganisms. • May possess flagella (long whiplike extensions of the cytoplasm) or cilia (fine hairlike extensions); for example, Trichomonas vaginalis

24. Classifications of Microorganisms • Other Identifying Characteristics • Bacteria can be categorized by their ability to hemolyze (burst) red blood cells in blood agar. • Biochemical analysis provides microbiologist with information that assists in identification of certain pathogens

25. Types of Microorganisms • Bacteria • Singular: bacterium • Small, unicellular microorganisms capable of rapid reproduction • Overgrowth of bacteria can cause an imbalance and lead to disease or pathology. • Most bacteria thrive in warm, dark, moist environment; bacteria can easily thrive and grow in human body

26. Types of Microorganisms • Bacteria • Reproductive ability explains how some infections become overwhelming in a short period of time and can be dangerous • May be named for their morphology (shape) • Cocci (spherical) • Bacilli (rod-shaped) • Spirilla (spiral-shaped)

27. FIGURE 45-3 Bacteria may be named for their morphology (shape): cocci (spherical), bacilli (rod shaped), or spirilla (spiral shaped).

28. Types of Microorganisms • Cocci • Round bacteria that are arranged in various configurations • Staphylococci • Gram-positive, grape-like clusters of cocci, some of which are pathogenic • Nonpathogenic staphylococci - found on our skin and in many of our body orifices, or openings

29. Types of Microorganisms • Staphylococci • S. aureus (staph) is a major pathogen of this genus; may be found as normal flora in the nose and on the skin • Causes infection especially when resistance is lowered by a break in the skin or in the mucous membranes

30. Types of Microorganisms • Staphylococci • S. aureus (staph) is a major pathogen of this genus; may be found as normal flora in the nose and on the skin • Skin is most common site of infection • Produces infections such as impetigo in children; associated with infection of wound sites and surgical incisions

31. Types of Microorganisms • S. aureus • Causes pus-producing abscesses such as boils, carbuncles, and folliculitis • Common cause of nosocomial infections • May also cause pneumonia, meningitis, and septicemia in individuals with reduced resistance • Toxic shock syndrome caused by this virulent organism

32. FIGURE 45-5 Carbuncles caused by S. aureus.

33. Types of Microorganisms • S. aureus • Produces one type of enteritis (food poisoning) that occurs within in a few hours of eating improperly refrigerated food contaminated with the toxin produced by the bacteria • Coagulase positive, meaning it produces an enzyme that can be used to help differentiate S. aureus from other species of this organism

34. Types of Microorganisms • Superbugs • Term refers to various microorganisms that are mutating to produce antibiotic-resistant forms

35. Types of Microorganisms • Methicillin-resistant Staphylococcus aureus (MRSA) • Form of S. aureus • Produces an enzyme that makes the organism resistant to penicillins and cephalosporins normally used for treatment and renders these antibiotics ineffective

36. Types of Microorganisms • Methicillin-resistant Staphylococcus aureus (MRSA) • Vancomycin-resistant enterococci (VRE) and carbapenem-resistant enterobacteriaceae (CRE) also becoming more prevalent • Tests available to indicate presence or absence of enzyme and help determine the most favorable treatment

37. Types of Microorganisms • Methicillin-resistant Staphylococcus aureus (MRSA) • Antibiotic resistance is major concern for health care providers; experienced worldwide

38. Types of Microorganisms • Streptococci • Round, gram-positive bacteria arranged in chains • Some are nonpathogenic; others are dangerous to humans

39. Types of Microorganisms • Streptococci • Part of the normal flora of the upper respiratory tract and skin • One classification of these organisms is based on type of hemolysis the organisms cause on blood agar plates

40. Types of Microorganisms • Streptococci • Also classified serologically with antisera specific for antigens in cell walls that are specific for each group (A–H and K–V) • Identification of specific group of strep organisms important in epidemiology (study of outbreaks)

41. FIGURE 45-7 Streptococci: Individual bacteria that have a rounded shape and have clumped together to form a chain.Denis Finnin and Jackie Beckett/DK Images

42. Types of Microorganisms • Group A beta-hemolytic Streptococcus pyogenes • Causes variety of disease ranging from strep throat to necrotizing fasciitis

43. Types of Microorganisms • Group A beta-hemolytic Streptococcus pyogenes • Causes other infections including: • Pneumonia • Tonsillitis • Scarlet Fever • Rheumatic fever • Acute glomerulonephritis

44. FIGURE 45-6 A patient with necrotizing fasciitis to the feet, caused by group A beta-hemolytic strep.

45. Types of Microorganisms • Infections caused by Group A beta-hemolytic Streptococcus pyogenes: • Bacterial endocarditis • Abscesses • Wound infections • Bacteremia

46. Types of Microorganisms • Group A beta-hemolytic Streptococcus pyogenes • Commercial kits available for rapid detection in the office or laboratory setting • Negative test should be followed up by a culture that includes bacitracin sensitivity

47. Types of Microorganisms • Group A beta-hemolytic Streptococcus pyogenes • Commercial kits available for rapid detection in the office or laboratory setting • Sensitivity to bacitracin is a useful tool to separate group A beta-hemolytic strep from other strep organisms.

48. Types of Microorganisms • S. pneumoniae • Also called Pneumococcus or Diplococcuspneumoniae • Frequently found as normal flora in the throat • Frequent cause of bacterial pneumonia particularly in the older population, middle ear infections in children, and meningitis in older children and adults

49. Types of Microorganisms • Diplococci • Occur in pairs • Some are gram positive, such as S. pneumoniae (causes bacterial pneumonia) • Some are gram negative, such as N. gonorrhoeae (causes gonorrhea, an STI) and Neisseria meningitidis (causes a form of bacterial meningitis and septicimia)

50. Types of Microorganisms • Diplococci • Normally found in areas such as the upper respiratory tract