Infectious disease, General Pathology

Microbes can enter the host by breaching:

Epithelial surfaces

Inhalation

Ingestion

Sexual transmission

Most GI pathogens are transmitted by:

Food or drink contaminated with fecal material when hygiene fails, causing diarrheal disease

Normal gut microbiota inhibits the:

colonization and overgrowth by potential pathogens

Antimicrobial defensins in gut epithelial cells and IgA antibodies secreted into the gut lumen, can both do what to pathogens?

Neutralize them

This bacteria can deliver a powerful exotoxin during its growth in contaminated food, which is responsible for food poisoning.

Staph. aureus

This bacteria binds to intestinal epithelium and multiplies, overlying mucous layer they are delivering potent exotoxins responsible for disease:

E. coli

These bacteria will invade intestinal mucosa and the lamina propria and cause ulceration, inflammation, and hemorrhage that manifests clinically as dysentery.

Shigella

Salmonella enterica

Campylobacter jejuni

Entamoeba histolytica

This bacteria will invade superficially into the oral esophageal squamous mucosa in immunocompromised host causing thrush.

Candida albicans

this virus has an envelope of proteins called hemaglutinins that bind to sialic acid on the surface of epithelial cells. The attachment leads the host cell to endocytosis of the virus, leading to viral replication and injury.

Influenza virus

These two bacteria release toxins that enhance their ability to establish infection by impairing their ciliary activity (in respiratory tract)

Mycoplasma pneumonia

Bordetella pertussis

This bacteria effects the infectivity by surviving within the lysosomes of the macrophages (respiratory tract).

Mycobacterium

Other types of organisms that infect the respiratory tract due to immunosuppression of it’s host (AIDS patients)

Pneumocystis jirovecii (AIDS)

The urinary tract is protected from many bacteria due to:

frequent emptying of bladder

urine containing small numbers of low virulence bacteria

Urinary tract pathogens gain access via the:

urethra

Urinary tract pathogens must be able to adhere to the urothelium before:

being washed away

Why are women more predisposed to UTI’s?

Shorter urethra (5 cm)

Obstruction to urinary flow predisposes the host to UTI’s, an example of this is:

Prostatic hyperplasia

Vertical transmission refers to the transmission of microbes from:

mother to fetus

This virus infection during the FIRST TRIMESTER can lead to heart malformations, intellectual disability, cataracts, or deafness

Rubella

In the first trimester, a rubella infection can cause heart malformations, intellectual disability, cataracts, or deafness. In the 3rd trimester, an infection with the rubella virus has little effect. Why?

The time at which the infection occurs has influence on the consequences of the infection

Postnatal transmission in maternal milk can transmit these viruses:

cytomegalovirus (CMV)

Human immunodeficiency virus (HIV)

Hepatitis B virus (HPV)

Transmission during birth can occur by contact with infectious agents during the passage to the birth canal, some examples are:

Gonococcal

Chlamydial conjuctivitis

The most common and efficient microbial dissemination is through the:

Blood stream

Dissemination can spread through the lymphatics, which will:

deposit microbes into the lymph nodes, where they can further spread to the blood

Certain viruses can spread through the CNS by infecting peripheral nerves and traveling across axons, what are examples?

1. Rabies

2. Poliovirus

3. Varicella-zoster

Dissemination can manifest as what symptoms?

Fever

Low BP

Coagulopathies

Organ failure, death

Release of microbes may be accomplished by:

skin shedding

coughing

sneezing

voiding of urine or feces

during sexual contact

through insect bites

Shedding and transmission can occur most commonly during:

periods of host infection

Shedding by asymptomatic carriers can occur:

for long periods of time in certain diseases

What are some examples of waterborne pathogens?

Hepatitis A

Poliovirus

Rotavirus

Vibrio cholera

Shigella species

Clostridium jejuni

Staphylococcus enterica

Less common routes of spread can occur through saliva, replicating in the salivary glands or the oropharynx. An example of a virus that does this:

Epstein-Barr virus

Some important human pathogens are protozoa that can spread through the blood meals taken by arthropod vectors such as:

mosquitos, ticks, mites

Zoonotic infections are transmitted from animals to humans either by direct contact, including:

animal bites

use of animal products via an invertebrate vector

The outcome of an infection depends on:

virulence of the pathogen

The nature of the host response can be positive or negative:

Positive: elimination of infection

Negative: cause tissue damage

Pathogens have developed strategies to evade host defenses, such as:

capsular variation

resistance to antimicrobial peptides, change hydrophobicity

carbohydrate capsule to evade phagocytosis

Resistant to phagosomes

High mutation rates

Latent periods

Carbohydrate capsule of certain bacteria can allow the bacteria to:

evade phagocytosis

Staph. Aureus has protein A that binds to the Fc portion of antibodies, which:

inhibit phagocytosis

Antigenic variation produces capsular variation to:

elude opsonization

What is an example of a virus that has a high mutation rate that allows it to avoid detection to then infect and kill immune cells?

HIV

This microbe has an establishment of latent infections to avoid detection.

Herpes simplex

Defects in Toll like receptors predispose the patient to pyogenic bacteria, such as:

Strep pneumoniae

childhood HSV encephalitis

Antibody deficiencies can lead to increase infections with extracellular bacteria, such as:

Staph. A

Hemophilus influenza

Viruses can bind and enter the cell by using the cells:

surface proteins that are normally used to cellular functions

The presence of some receptors on certain cells will make them a target for certain viruses, a property known as:

Tropism

What is an example of ‘tropism’?

HIV glycoprotein gp120 attaches to the CD4 receptor on T cells

EBV binds to complement receptor 2 on B-cells

What are 3 ways the host can be damaged by microbes (viral)?

1. Direct cytopathic effects

2. Antiviral immune response

3. Transformation of infected cells

How can direct cytopathic effects damage the host?

1. Prevent synthesis of critical host macromolecules (DNA, RNA)

2. Activate death receptors, to trigger apoptotic machinery

In an antiviral immune response, host lymphocytes can identify a virus infected cells and kill them, but in the process:

it will cause tissue damage

How can the transformation of infected cells cause host damage?

1. Viruses stimulate proliferation of cells by producing viral proteins that inactivate host cell anti-oncogenes

2. Insert viral genes into host DNA

Virulence genes are transmitted in mobile genetic elements such as:

plasmids

bacteriophages

Some bacteria produce certain proteins only when they reach a high concentration is a process called:

quorum sensing

In quorum sensing, it will initiate a production of:

toxins

What are some examples of quorum sensing?

1. biofilms where bacteria produce polysaccharides, attaching to devices such as IV catheters or artificial joins to avoid immune detection or destruction

Bacteria express surface proteins that allow the bacteria to bind to host cells:

adhesions

What are some examples of bacteria and adhesions?

1. Strep pyogenes using adhesion protein F and teichoic acid to bind to fibronectin on the surface of cells

These are filamentous structures on the surface of bacteria, that consist of repeating protein subunits. The length will grant the bacteria BINDING SPECIFICITY.

Pili

This bacteria has pili that vary in length to evade detection.

Neisseria gonorrhea

What is the mechanism that allows intracellular bacteria to enter the cell?

Enter via cell surface receptors

eg. mycobacteria use host receptors for opsonins (antibodies and C3) to enter the cell

Mycobacteria prevent the fusion of the endosome to the lysosome to:

avoid destruction and continue to proliferate in the cell

Shigella and E. coli inhibit protein synthesis and then:

proliferate rapidly to cell lysis within hours

Listeria monocyogenes produce pore-forming protein (listeriolysin o and twwo phospholipases that degrade the:

phagosome and allow entry into the cytoplasm

What are endotoxins?

Lipopolysaccharides in the outer membrane of gram-negative bacteria that stimulate host response and cause tissue damage

what is the mechanism with LPS and septic shock?

Bind to CD14, then bind to TLR4 to activate host immunity, but in high levels this will cause septic shock

Exotoxins are secreted by:

bacterial proteins that cause cell injury

What are some examples of exotoxins and what do they cause?

1. Enzymes that degrade cell walls

2. Toxins that interfere with cellular functions

3. Superantigens stimulate large number of T cells that secrete high levels or injurious cytokines

How does Clostridium tetani toxins interfere with cellular function?

Inhibits nerve transmission resulting in paralysis

This inflammation is characterized by increased vascular permeability and leukocyte infiltration (predominantly neutrophilic)

Suppurative (purulent) inflammation

What are characteristics of suppurative inflammation?

1. Neutrophils are attracted to the site of infection by chemo attractiveness by pyogenic bacteria

2. Most are gram-positive cocci and gram-negative rods

3. Masses of dying neutrophils and liquefactive necrosis of the tissue form pus

4. Site of these accumulations vary, microscopic to entire lobeo f lung

the destructiveness of suppurative inflammation is variable because:

of what bacteria is causing it

Spirochetes and helminths can provoke what responses?

mononuclear responses

This is a form of mononuclear inflammation evoked by infection organisms that resist eradication.

Granulomatous inflammation

What are some examples of bacteria that can cause mononuclear and granulomatous inflammation?

Mycobacterium tuberculosis

histoplasma capsulatum

This type of inflammation is characterized by accumulation and aggregation of activated macrophages (epitheloid macrophages)

Granulomatous inflammation

These lesions are characterized by cell necrosis of cell proliferation usually with sparse inflammatory cells.

Cytopathic-cyto-proliferative reactions

Herpes virus and adenovirus will replicate with cells and make viral aggregates that are visible as:

inclusion bodies

Focal cell damage in skin may cause epithelial cells to become detached forming:

blisters

some viruses cause epithelial cells to proliferate to form: (2 things, viruses)

Warts, HPV

Umbilicated papules, molluscum contagiosum

This parasite causes colonic ulcers and liver abscesses that are characterized by extensive tissue necrosis with inflammatory infiltrate.

Entamoeba histolytica

Clostridium perfringens and corynebacterium diptheriae secrete powerful toxins that cause:

rapid and severe necrosis (gangrenous necrosis), where tissue damage is a prominent feature

Both of these viruses replicate in the skin and mucous membranes where they produce infectious variants and cause vesicular lesions of the epidermis.

HSV 1 and HSV 2

HSV1 and HSV2 can spread to:

sensory neurons that innervate the skin and mucous membranes (primary sites)

HS1 and HS2 mechanism:

1. Replicate in the skin and mucous membranes

2. Can spread to sensory neurons that innervate these sites

3. Viral nucleocapsids transport along axons to neuronal cell bodies where the virus establishes latent infection.

Clinical manifestations of SARS-Co-V-2 (COVID-19)

mild to severe respiratory disease

flu-like symptoms leading to a full recovery

Histological analysis of COVID-19 in the lung:

diffuse alveolar damage and inflammation with mainly mononuclear cells

This virus is a flavivirus that is transmitted by Aedes mosquitoes in tropical and subtropical regions.

Dengue virus

What are the symptoms of dengue?

Mild with fever, headache, macular rash, severe myalgias

severe, hemorrhagic fever

The zika virus is what type of virus?

Flavivirus

Manifestations of zika virus:

Mild, fever, myalgia, arthralgia, conjuctivitis, maculopapular rash lasting a few days to a week

In a few cases, Zika virus can also cause:

Guillain-Barre syndrome

Perinatal transmission of the Zika virus can cause:

Fetal death

moderate to severe brain defects of the fetus (microcephaly)

How is the Zika virus transmitted?

Mosquito, Aedes egypti

Ebola has two specific mechanism to evade the immune response, which are:

VP24

VP35

How does the Ebola virus evade the immune response?

The two viral proteins inhibit the action of the type 1 interferon

Ebola carries about a 40%:

mortality rate

Viral hemorrhagic fever is caused by envelope of RNA viruses belonging to 4 different genre:

1. Arenairidae

2. Filoviridae

3. Bunyaviridae

4. Flaviviridae

Viral hemorrhagic fever viruses are:

Ebolma

Marburg

Lassa

Humans are incidental hosts of viral hemorrhagic fever, so how do humans contract it?

Coming in contact with infected hosts, typically rodents, mosquitoes, and ticks

Symptoms of viral hemorrhagic fever:

mild to life-threatening fever, headache, myalgia, rash, neutropenia, thrombocytopenia

The West Nile Virus is usually asymptomatic but can cause:

fever

headache

myalgia

fatigue

anorexia

Nausea