1. Introduction to Infectious Disease
T. Davis

2. Sample Question
A marked increase in the incidence of cases of tuberculosis in New York City in the 1980s was due to:
A. multiply drug-resistant M. tuberculosis
B. resistance to INH
C. genes for capsule production
D. virulent strains from Thailand
E. more homeless and AIDS patients

3. Sample question 2
A special stain that will demonstrate bacteria, fungi, parasites and viral inclusions is:
A. Gram stain
B. Acid-fast stain
C. Modified acid-fast stain
D. Giemsa stain
E. Silver (GMS) stain

4. ID Outbreaks in the U.S. Polio Legionnaire’s Disease
Toxic Shock Syndrome
Lyme Disease
Human papillomavirus
Tuberculosis
Hantavirus
SARS and Anthrax
HIV/AIDS
*MRSA
*Clostridium difficile
* often hospital-acquired

5. “Emerging” Infectious Diseases
Microorganisms do not change much
Human behavior changes a lot

6. PARALYTIC POLIO Poor Sanitation (U.S. in 1800) childhood diarrhea
enterovirus infection and immunity
paralysis rare
Good Sanitation (U.S. in 1900)
children not infected and do not become immune
young adults infected
receptors on anterior horn cells- paralysis

7. Red areas exhibit the highest rates of paralytic polio

9. Legionaire’s Disease
Legionella is present in fresh water ponds, plumbing systems and aerosols (humidifiers)
Sporadic cases occur
American Legion convention with many elderly attendees with chronic lung disease
New tools developed to identify Legionella- DFA, urine antigen test and DNA probes
Hyper-chlorination or superheating of water in hospitals prevents Legionaire’s Disease
Hospital water monitored for Legionella

10. Legionella DFA

11. Toxic Shock Syndrome Staphylococcus aureus with TSST-1 toxin
1980s- Use of hyperabsorbent tampons (RELY brand) caused an epidemic of cases
Toxic shock still seen sporadically caused by both staphylococci and streptococci

12. Rash of Toxic Shock Syndrome

14. Lyme Disease
Borrelia burgdorferi- rash, arthritis, (meningitis and myocarditis)
deer tick and white-tail deer reservoir
rat tick and woodrat reservoir in California
more deer-more ticks-more people
wildlife protection-housing development

19. Tuberculosis Mycobacterium tuberculosis
In the U.S. the people at risk are: homeless, elderly in nursing homes, prisoners and AIDS patients
If people are poor, malnourished, and have crowded living conditions, tuberculosis will flourish

21. U.S. Born: Whites and Blacks most common
Foreign Born: Asians and Hispanics most common

22. Tuberculosis is a communicable disease

23. LN
Ghon Lesion
Ghon Complex or Promary Complex (LN and peripheral lesion)

24. TB in the upper lobe- caseous granulomas

25. Hantavirus 4 corners area (SW USA)
flu-like illness to hemorrhagic fever with sudden death (carried by deer mice)
excess rain leads to bumper crop of pinon nuts
deer mice eat nuts and population increases
Navajos harvest pinon nuts

27. The deermouse and family

29. MRSA and C. difficile MRSA Wide use beta-lactams
Poor handwashing- more patients per nurse/doctor
Real-time PCR for diagnosis
Clostridium difficile
Use of Clindamycin
Use of proton pump inhibitors
Use of quinolones (gattifloxacin, moxifloxacin)
Real-time PCR for diagnosis

30. Emerging Diseases ?? The human population changes behavior
Microorganisms do not change behavior

31. How Do Microorganisms Cause Disease?
Direct contact with cell death (Streptococcus produces cellulase)
Release of toxins that enter the blood and kill target tissue (C. diphtheriae)
The host response, such as abscess (staphylococci) or granuloma (TB), that destroys host tissue

32. Release and Transmission
Contact- wound, body fluids or mucosal surfaces (as in STDs)
Cough with aerosol as in TB
Insect vectors as in malaria
Diseases spread from person to person are said to be contagious or COMMUNICABLE
Diseases acquired in the hospital are NOSOCOMIAL

33. Viral Surface Protein Receptors
EBV- **CD21 (CR2) receptor on B-cells and perhaps macrophages; atypical lymphocytes in blood are mainly CD8+**
Rabies- acetylcholine receptor on neurons
Rhinovirus- ICAM-1 on mucosal cells
HIV- CD4 , CXCR4 or CCR-5

34. FIGURE 8-5
Robbins

35. HIV Kills CD4 (Helper) T- Lymphocytes
Only 1/100,000 CD4 lymphocytes are infected
Infected cells induce non-infected cells to commit suicide by APOPTOSIS and other mechanisms

36. Bacterial Injury Virulence genes
Salmonella and E. coli have similar virulence genes but E. coli lacks genes for attachment and invasion
Helicobacter pylori and Corynebacterium diphtheriae strains that do NOT produce toxins are not pathogenic

37. Bacterial Adhesins (Robbins Figure 8-2)
Lipoteichoic acids on Streptococci bind tightly to blood cells and oral epithelial cells
Pili on GN rods and cocci- proteins at the tips of the pili bind sugars

38. FIGURE 8-2 Robbins

39. Bacterial Targets
Unlike viruses that invade many cell types bacteria primarily infect epithelial cells (Shigella, E. coli), macrophages (TB) or both (Salmonella, Listeria)
Macrophages- receptors for Ab or C’
Epithelial Cells- many bacteria bind to integrins such as CR3 (complement iC3b)

40. Bacterial Toxins
Endotoxin
Exotoxin
Enterotoxin

43. Immune Evasion
1. Inaccessibility- C. difficile in the intestinal lumen
2. Block phagocytosis- S. pneumoniae’s mucopolysaccharide capsule
3. Antigenic Variation- influenza virus and rhinovirus
4. Immunosuppression- HIV and EBV

44. Diagnosing Infectious Diseases
Special Stains
Laboratory Culture
Nucleic acid probes (DNA probes)
Amplified nucleic acid probes
Clinical History

45. Special Stains for Microorganisms
Gram Stain- G+ and G- bacteria; Candida
Giemsa Stain- bacteria, fungi (all), viral inclusions, parasites
Silver Stain (GMS)- fungi and a few bacteria
(Modified)-Acid-Fast Stain- mycobacteria and Nocardia

46. GRAM STAIN Any fluid or tissue Screen for or identify bacteria
30 minute turnaround
GPC, GPR, GNC, GNR and yeast
Poor sensitivity for filamentous fungi, mycobacteria, parasites and viral inclusions

47. Gram-negative bacilli

48. Gram stain of Clostridium perfringens

49. Gram Stain of Candida albicans

50. Giemsa Stain or Diff-Quick (rapid Giemsa) Stain
Any tissue or fluid
Works best on smears
Bacteria, fungi, parasites, viral inclusions
Rapid preparation (1 minute)

51. Giemsa Stain of a perispinal abscess shows many intracellular cocci

52. Giemsa stain of Histoplasma capsulatum

53. Giemsa stain of Cytomegallo Virus (CMV)

54. *
Giemsa Stain of Bronchoalveolar Lavage- * Pneumocystis cyst with 8 trophozoites

55. MICROWAVE GMS (Silver) STAIN
Any tissue or fluid- 30 minutes
All fungi including Pneumocystis
Histoplasma, Cryptococcus, Mucor, Aspergillus
Most sensitive stain for fungi
Poor for bacteria and mycobacteria
O.K. for Nocardia and Actinomyces

57. Silver Stain of H. capsulatum

58. GMS Stain- Cryptococcus neoformans in a chest wall biopsy

59. GMS (silver) Stain

60. Empty spherule
Endospores
Spherule with endospores
GMS (silver) Stain of C. immitis

61. GMS Stain shows cysts (“cups, targets, grooves”)

63. ACID-FAST STAINS (Kinyoun, Ziel-Neelsen, etc.)
Carbolfucsin or fluorescent (more sensitive)
“modified” AFB for Nocardia- weak acid wash
Mycobacterium, Nocardia, Rhodococcus, Cryptosporidium
Sputum must be decontaminated and concentrated for high sensitivity

64. Fluorescent Acid-Fast Stain of M. tuberculosis

65. Mycobacterium avium in a lymph node biopsy; Acid-fast Stain

66. Acid-fast Stain of M. tuberculosis demonstrating “cording”

67. Nocardia is partially acid-fast and may grow on “TB” media

68. Filamentous Nocardia on a Gram Stain (gram positive filaments)

69. Nocardia demonstrated by a modified-acid-fast stain

70. SPECIAL SILVER STAINS Warthin Starry, Dieterle Treponema pallidum
Legionella
Bartonella

71. Dieterle/Warthin-Starry Stain shows Treponema pallidum

72. DIRECT FLUORESCENT ANTIBODY STAIN
Sputum or respiratory washings
Legionella, Bordetella persussis Herpes virus and others
**Currently we are identifying Influenza A by PCR or DFA and most are H1N1 (by PCR)

73. Fluorescent antibody stain demonstates Herpes-infected cells

74. Laboratory Cultue Solid Media- wounds, throat, urine, sputum
Broth- blood and sterile body fluids
Tissue Culture- virus, Chlamydia (rare)

75. DNA Probes
GC and Chlamydia from urogenital specimens *(including Pap Smears)
ID of bacterial, fungal and mycobacterial growth in broth and on solid media
Candida, Gardnerella and Trichomonas from vaginal discharges

76. DNA Probe

77. DNA Probe

78. Amplified DNA Probes PCR, LCR, TMA, SDA
GC and Chlamydia- urogenital swabs or urines
M. tuberculosis in respiratory specimens- we now offer a direct PCR that identifies M. tuberculosis and Rifampin/INH resistance

79. SDA

80. TMA

81. Real-time PCR for MRSA, GBS and C. difficile
Results in 1-2 hours (short as 45 minutes)
Methicillin-resistant Staphylococcus aureus, C. difficile (MRSA) and Group-B streptococcus/ S. agalactiae (GBS) are FDA-approved tests that are done directly on the specimen (no culture)

83. IDI-MRSA™ Provides a Definitive Result
MSSA
SCCmec
orfX
Primers
Junction Region for Detection
Staphylococcal
Chromosomes
DNA detection of the SCCmec-orfX junction found only in MRSA provides definitive identification of MRSA
Only molecular method to definitively identify MRSA in specimens which contain methicillin-resistant coagulase negative Staphylococci and mecA negative S. aureus. Normally such a combination would yield false-positives in other PCR methods
Detects both HA-MRSA and CA-MRSA strains (i.e. USA300)

84. Rapid IDI-MRSA/MSSA Assay*
Assay under development, allowing the direct detection of MRSA and MSSA in under 2 hours of laboratory time
Plan to validate four different specimen types:
Positive blood bottles, wound swabs, nasal swabs,
and rectal swabs
MRSA Positive
MSSA Positive
Standard Antibiotics
Definitive On-screen Results
Swab of Suspect Site
MRSA/MSSA
Analysis
* Under development

85. Inflammatory Response to Infectious Diseases
Host Dependent- eg. Greatly reduced in AIDS
PMNs- pyogenic response to many bacteria: staphylococci, streptococci, GNRs
Granulomatous- tuberculosis, histoplasmosis

86. Inflammatory Response To Infection
Bacteria- usually neutrophils (PMNs); liquefactive necrosis; abscess
Fungi- usually macrophages/lymphocytes; granulomas
Virus- usually lymphocytes; may show cytopathic effect (CPE)
Immune Deficient Host- there may be absence of the normal inflammatory response and high numbers of microorganisms (eg. M. avium in AIDS)

87. Bacterial abscess in the brain

88. Giemsa Stain of a perispinal abscess shows many intracellular cocci

90. TB Granuloma

93. Inflammatory Response (2)
Cytopathic- viral inclusions in Herpes and CMV or dysplastic changes in HPV
Necrosis- Clostridium perfringens in gas gangrene

94. Koilocytosis of HPV

95. Giemsa stain of Cytomegallovirus (CMV)* *
* Viral inclusions in the nuclei