Pathology Infectious Disease Intro: Lecture 14

Front 1

“Emerging” Infectious Diseases:

Back 1

“Emerging” Infectious Diseases aren't really emerging. Instead, they are re-emerging.

- Microorganisms do not change much

- Human behavior changes a lot - Almost everything that we talk about in path has been made worse because of some kind of human behavior

Front 2

PARALYTIC POLIO: Poor Sanitation

Back 2

PARALYTIC POLIO: Poor Sanitation

Poor Sanitation (U.S. in 1800)

Children do get infected so they get childhood diarrhea, gastro-enteritis, and they become immune.

Paralysis is rare in childhood. Why? because children don't have the receptors for polio virus on the anterior horn of their SC, therefore no paralysis.

Front 3

Cause of Polio?

Back 3

Enterovirus

Front 4

PARALYTIC POLIO: Good Sanitation

Back 4

PARALYTIC POLIO: Good Sanitation

Good Sanitation (U.S. in 1900)

Children are not infected and do not become immune, so... young adults are infected.

Young adults do have the receptors for Polio virus on anterior horn cells so paralysis occurs.

Front 5

When do you NOT see polio?

Back 5

You don't see polio:

1. with poor sanitation
2. If there's good sanitation and good immunization

Front 6

Legionnaire’s Disease

Back 6

Legionella is present in fresh water ponds, plumbing systems and aerosols

Sporadic cases occur

American Legion convention with many elderly attendees with chronic lung disease - they all got exposed to Legionella through the air conditioning.

New tools developed to identify Legionella- DFA, urine antigen test and DNA probes

With new tests, we found that there was a lot of Legionnaire's disease in hospitals. But we could rid of it. How? Hyper-chlorination of water in hospitals

Front 7

What is this?

Back 7

Legionella DFA (direct fluorescent antibody)

Front 8

Toxic Shock Syndrome

Back 8

Toxic Shock Syndrome

Staphylococcus aureus with TSST-1 toxin

1980s- Use of hyperabsorbent tampons (RELY brand) caused an epidemic of cases - of left in too long, this was a great environment for the staph aureus to grow and release its toxin.

Toxic shock still seen sporadically caused by both staphylococci and streptococci

Front 9

Clinical presentation of Toxic Shock Syndrome:

Back 9

Clinical presentation of Toxic Shock Syndrome:

1. Hypotension
2. Rash - because of sepsis with staph arureus
3. Skin falling off palms and a lot of the body

Front 10

Lyme Disease

Back 10

Lyme Disease

Caused by a spirochete

Borrelia burgdorferi- rash, arthritis, (meningitis and myocarditis)

Cause: deer tick bite that live on the white-tail deer

Cause in Cali: rat tick and woodrat reservoir in California that live in the palm trees

more deer-more ticks-more people
wildlife protection-housing development

Front 11

Human Papillomavirus

Back 11

Human Papillomavirus

Causes condyloma, dysplasia and cervical carcinoma (we see a lot of carcinoma in-situ, but not a lot on invasive cervical cancer because it can take around 10 years to actually become invasive.)

There is a more sexually active population

The incidence (and prevalence) of CIS is increasing in the U.S. (but mortality is decreasing)

We are also seeing more head and neck tumors cause the HPV because of spread from the mouth and throat.

Front 12

What types of HPV cause cervical CA?

Back 12

HPV DNA Types 16 and 18

Front 13

HPV DNA Types 16 and 18: How do they cause cervical CA

Back 13

HPV Infection produces proteins E6 and E7
p53 protein, RB and p21 protein are inactivated
Apoptosis does not occur and the infected cells are not killed
Dysplasia and cervical cancer may result

Front 14

What is the pathogenesis of HPV?

Back 14

The virus eventually integrates in the human chromosome, it takes over the human cell machinery, shuts down p53 and the brakes on the retinoblastoma gene (RB), so the cells proliferate and become immortal. If they're there long enough, they'll go through mild dysplasia, moderate dysplasia, marked dysplasia, carcinoma in-situ, and then invasive CA. But since it takes so long do this to happen, we can catch it.

Front 15

What is this?

Back 15

Cervical Carcinoma In-Situ

The Number of cases of CIS increases annually, but the number of cases of invasive cervical CA goes DOWN annually

Front 16

Tuberculosis

Back 16

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.

This is a communicable disease that is spread from person to person.

As long as people are crowded, malnourished, and don't have good access to medical care, TB will thrive.

Front 17

How is TB spread?

Back 17

Front 18

What is this?

Back 18

TB in the upper lobe- caseous granulomas

This is reactivation TB. When TB reactivates, it does so in the apex of the lung, and it's a much more aggressive disease.

Front 19

T or F: In TB, mycobacterium does the damage to our lungs.

Back 19

FALSE:

In TB, it's not the bacteria that does the damage, it's US. Our cell-mediated response to the organism does the damage.

Therefore, there's more damage in reactivation TB because we already have memory T-cells. There's more necrosis and more cavitation in reactivation TB, compared to primary TB.

Front 20

Hantavirus

Back 20

Hantavirus

A hemorragic fever virus.

4 corners area (SW USA) - Utah, Arizona, Colorado, and New Mexico

flu-like illness to hemorrhagic fever with sudden death (carried by deer mice)

excess rain leads to bumper (extra) crop of pinon nuts. Mice and humans collected the nuts. The mice urinated on the nuts and the people ate these nuts. This caused an outbreak.

deer mice eat nuts and population increases

Navajos harvest pinon nuts for food and decoration

Front 21

What are the two out-breaks of infectious disease that are constant (not seasonal)?

Back 21

MRSA and C. difficile

MRSA:
1. Wide use of beta-lactams - we select for resistant organisms
2. Poor hand-washing- more patients per nurse/doctor (everyone is busy and don't wash their hands as much)

Clostridium difficile
1. Use of Clindamycin
2. Use of proton pump inhibitors
3. Use of quinolones (gattifloxacin, moxifloxacin) - there's a strain of quinolone resistant C. difficile that's very prevalent now.

Front 22

Koch’s Postulates

Back 22

Koch’s Postulates

Microrganism is found in lesions of the disease

Organism is isolated on solid media cultures

Organisms from culture causes lesions in experimental animals

Organisms can be recovered on solid media cultures from lesions in the animals

This is how you prove that something causes infection. BUT, we found that several organisms don't grow on solid media.

Front 23

Problems with Koch’s Postulates

Back 23

Problems with Koch’s Postulates

Viruses, Rickettsiae, Chlamydia etc. do not grow on solid media

DNA Probes and Amplified DNA Probes are more sensitive and more specific than culture (on solid media or tissue culture)

Therefore, the “Gold Standard” is often NOT culture, it's MOLECULAR standards. 2 positive molecular test give a true positive.

Front 24

Categories of Infectious Agents

Back 24

Categories of Infectious Agents

Prions- kuru, C-J Disease, mad cow disease
Viruses
Bacteriophage/Plasmid
Bacteria
Chlamidiae/Rickettsiae/Mycoplasma
Fungi
Parasites (protozoa, worms, ectoparasites)

Front 25

What makes a disease infectious?

Back 25

In order for a disease to become infectious, it has to penetrate some epithelial surface.

It then may go via nerves or may be taken up by phagocytes into the lymphatics or blood stream, and then it's spread to organs.

Front 26

Release and Transmission of Infectious Agents

Back 26

Release and Transmission of Infectious Agents:

1. Contact- wound, body fluids or mucosal surfaces (as in STDs)
2. Cough with aerosol as in TB
3. Insect vectors as in malaria and lyme disease
4. Diseases spread from person to person are said to be contagious or COMMUNICABLE
5. Diseases acquired in the hospital are NOSOCOMIAL. In general, 72 hours after admission, if you get a new infection, it can be considered nosocomial.

Front 27

How Do Microorganisms Cause Disease?

Back 27

How Do Microorganisms Cause Disease?

1. Direct contact with cell death (streptococcus produces cellulase - enzymes that destroy tissue)
2. Release of toxins that enter the blood and kill target tissue (C. diphtheriae - the psuedomembrane in the airway produces an exotoxin that travels to the myocardium, and you get myocarditis.)
3. The host response, such as abscess (staphylococci) or granuloma (TB), that destroys host tissue

Front 28

Viral Surface Protein Receptors

Back 28

Viral Surface Protein Receptors

There are attachment points:
EBV- CD21 (aka CR2) receptor on B-cells and perhaps macrophages, In the peripheral blood smear there are atypical lymphocytes in the blood are mainly CD8+ (T-cells)

Rabies- acetylcholine receptor on neurons

Rhinovirus- ICAM-1 on mucosal cells

HIV- CD4 , CXCR4 or CCR-5

Front 29

Why is HIV so deadly?

Back 29

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

Front 30

What is the general pathogenesis of viruses?

Back 30

Viruses enter the cell and take over the cell machinery.

Front 31

What is the general pathogenesis of viruses?

Back 31

Viruses enter into the host cell and take over that cells machinery.

Front 32

Bacterial Injury

Back 32

Bacterial Injury

A lot of bacterial have Virulence genes, but some do not. (TB doesn't have any virulence genes, strep does.)

Salmonella and E. coli have similar virulence genes but E. coli lacks genes for attachment and invasion. This means that E. coli lacks the ability to become a serious disease. This is a good thing because E. coli is the most common gram negative bacteria.

Helicobacter pylori (gastric ulcers) and Corynebacterium diphtheria strains that do NOT produce toxins are not pathogenic. they are not pathogenic unless that have the gene to make the toxin. In Corynebacterium, this gene is found in a phage.)

Front 33

Bacterial Adhesins

Back 33

Bacterial Adhesins:

Lipoteichoic acids on G+, Streptococci bind tightly to blood cells and oral epithelial cells

Pili on G- rods and cocci- proteins at the tips of the pili bind sugars

type I- mannose (UTI)
type P- galactose (pyelonephritis)
type S- sialic acid (meningitis)

Front 34

Bacterial Targets

Back 34

Bacterial Targets

Unlike viruses that invade many cell types, bacteria primarily infect epithelial cells (Shigella, E. coli), macrophages (TB) or both (Salmonella, Listeria)

Don't have to know below:
Macrophages- receptors for Ab or C’

Epithelial Cells- many bacteria bind to integrins such as CR3 (complement iC3b)

Front 35

Bacterial Toxins

Back 35

Bacterial Toxins

Endotoxin
Exotoxin
Enterotoxin - affects the gut

Front 36

Diphtheria Exotoxin

Back 36

Diphtheria Exotoxin:

There are 2 parts to the toxin.
1. Fragment B (COOH)- attachment

2. Fragment A (NH2)- enzymatically active

Connected by a S-S bridge

Front 37

What is the pathogenesis for the Diptheria toxin?

Back 37

The Diptheria toxin attaches to cell receptors on myocytes of the myocardium. Then the toxin in split so you get the enzyme activity.

This is an exotoxin. The organism grows in the upper airway, and it releases the toxin that has its affect on the myocardial cells.

Front 38

Immune Evasion

Back 38

Immune Evasion

1. Inaccessibility- C. difficile in the intestinal lumen there are few protective organisms in the intstine- they hide from the immune system
2. Block phagocytosis- S. pneumoniae’s mucopolysaccharide capsule - presents phagocytosis
3. Antigenic Variation- influenza virus and rhinovisus - ex. H1N1 - this virus is a dramatic departure from the influenza viruses that have been seen over the past 50-60 years - it is very different so most of us have luttel immunity to it. Most of the time, the antigenic variation is very minimal so even though we aren't totally immune, we do have some partial protection with immunity. But with H1N1, many young people have NO immunity.
4. Immunosuppression- HIV and EBV - as they infect, they suppress the immune system

Front 39

What are the mechanisms in which organism hide from the immune system?

Back 39

Mechanisms in which organism hide from the immune system

Front 40

Diagnosing Infectious Diseases

Back 40

Diagnosing Infectious Diseases

1. Special Stains
2. Laboratory Culture
3. Nucleic acid probes (DNA probes)
4. Amplified nucleic acid probes
5. Clinical History
6. Blood - serologic testing to look for the presence of Abs

Front 41

Special Stains for Microorganisms

Back 41

Special Stains for Microorganisms

1. Gram Stain- G+ and G- bacteria; Candida, not good for anything else
2. Giemsa Stain- bacteria, fungi (all), viral inclusions, parasites - this will miss acid fast bacteria such as TB
3. Silver Stain (GMS)- fungi and a few bacteria
(Modified)-Acid-Fast Stain- mycobacteria and Nocardia

Front 42

GRAM STAIN

Back 42

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

Front 43

Giemsa Stain or Diff-Quick (rapid Giemsa) Stain

Back 43

Giemsa Stain or Diff-Quick (rapid Giemsa) Stain (very close to being equivalent)

Any tissue or fluid

Works best on smears

Bacteria, fungi, parasites, viral inclusions

Rapid preparation (1 minute)

Front 44

MICROWAVE GMS (Silver)  STAIN

Back 44

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

Front 45

ACID-FAST STAINS(Kinyoun, Ziel-Neelsen, etc.)

Back 45

ACID-FAST STAINS(Kinyoun, Ziel-Neelsen, etc.)

If you think you have TB or Nocardia, use this.

Carbolfucsin or fluorescent(more sensitive)

“modified” AFB for Nocardia- weak acid wash

Mycobacteria, Nocardia, Rhodococcus, Cryptosporidium

Sputum must be decontaminated and concentrated for high sensitivity

Front 46

What is this?

Back 46

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

95% of the time when you see cording, it's M. tuberculosis.

Front 47

SPECIAL SILVER STAINS

Back 47

SPECIAL SILVER STAINS

1. Warthin Starry, Dieterle
2. Treponema pallidum
3. Legionella
4. Bartonella

Front 48

DIRECT FLUORESCENT ANTIBODY STAIN

Back 48

DIRECT FLUORESCENT ANTIBODY STAIN

1. Sputum or respiratory washings
2. Legionella, Bordetella persussis Herpes virus and others
3. Currently, we are identifying Influenza A by DFA and most are H1N1 (by PCR)

Front 49

Laboratory Culture

Back 49

Laboratory Culture

1. Solid Media- wounds, throat, urine, sputum
2. Broth- blood and sterile body fluids
3. Tissue Culture- virus, Chlamydia (rare)

These are used less and less are more molecular testing is done.

Front 50

DNA Probes

Back 50

DNA Probes:

1. Gonorrhea and Chlamydia from urogenital specimens
2. ID of bacterial, fungal and mycobacterial growth in broth and on solid media
3. Candida, Gardnerella and Trichomonas from vaginal discharges

The most common type of DNA probe is against rRNA.

Front 51

Amplified DNA Probes

Back 51

Amplified DNA ProbesPCR, LCR, TMA, SDA
GC and Chlamydia- urogenital swabs or urines
M. tuberculosis in respiratory specimens

You take a small part of the organism, you amplify it, and test for it. This increases the sensitivity.

Front 52

Transcription Mediated Amplification (TMA)

Back 52

Transcription Mediated Amplification (TMA)

The test used for amplified TB testing. If a patient has a positive acid fast smear on a sputum, you submit that to a lab and do this test.

This test uses reverse transcriptase and polymerase.

Front 53

MRSA -

Back 53

MRSA:

The problem with methicillin resistant Staph. aureus is that they have a mutation, and the penicillin binding proteins are different, so antibiotics like methicillin and oxacillin and all of the beta-lactams don't work because the target have been modified. The gene responsible is the mecR1 gene.

Front 54

Real-time PCR

Back 54

Real-time PCR

Results in 1-2 hours

Methicillin-resistant Staphylococcus aureus (MRSA) and Group-B streptococcus/ S. agalactiae (GBS) are FDA-approved tests - these can be identified very quickly.

Other tests are ASRs (analyte specific reagents) that must be validated in your own laboratory; NO ready-to-use kits

The reason this real-time PCR works is that you read it before it completes. This is why its so quick.

Front 55

Inflammatory Response to Infectious Diseases

Back 55

Inflammatory Response to Infectious Diseases

Host Dependent- eg. Greatly reduced in AIDS - In pts. with AIDS or who are very immune compromised, there may be no immune response at all so a biopsy will not show classic granulomas.

PMNs- pyogenic response to many bacteria: staphylococci, streptococci, GNRs

Granulomatous- tuberculosis, histoplasmosis (fungi)

Lymphocytes - virus

Therefore:
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)

Cytopathic- viral inclusions in Herpes and CMV or dysplastic changes in HPV

Necrosis- Clostridium perfringens in gas gangrene

Front 56

What's going on in primary TB during granuloma formation?

Back 56

Always remember INF- gamma

Front 57

TB Locations in Lung

Back 57

Primary TB - mid lung fields
Re-Activation TB - apex of lung