Pathogenic Substances, Infections, and Viruses: A Comprehensive Guide

Posted on Aug 6, 2024 in Biology

Pathogenic Substances Produced by Streptococcus Pyogenes

1. What are the pathogenic substances produced by Streptococcus pyogenes?

Invasive &pygenic infection:
Streptococcal sore throat
Streptococcal pyoderma
Cellulitis
Subacute endocarditis
The most common bacterial cause of sore throat
Intoxication
Poststreptococcal sequelae.

Mechanism of Cholera Toxin

2. Explain the mechanism of cholera toxin?

Produce the symptoms of cholera.
A-B type ADP-ribosylating toxin

Sub unit A: ADP-ribosylating activity.

Sub unit B: Bind to a GM1 ganglioside receptor.

Catalyze the ADP ribosylation of the G protein
cAMP
Secretion of electrolyte & water
Massive watery diarrhea without inflammation (20-30l/d)
Dehydration & electrolyte imbalances, shock, acidosis, death.

Culture Medium Interpretation

Please give interpretation to culture medium?

It supports containing appropriate nutrients artificially made for growth of bacteria (or) fungi. i.e., liquid, semisolid, solid medium

Nutrients
pH
Temperature
Aeration
Ionic strength
Osmotic pressure

Clinical Findings of HIV Infection

What are the four stages of clinical findings of HIV infection?

Stage I: Primary

Short, six weeks after infection
No symptoms
Infected person can infect others

Stage II: Asymptomatic

Lasts for an average of 10 years
HIV antibodies are detected in the blood

Stage III: Symptomatic

Symptoms are mild
Immune system deteriorates

Stage IV: HIV — AIDS

Immune system weakens
Opportunistic infection – Pneumocystosis, malignancies — Kaposi’s sarcoma

Bacterial — Tuberculosis, Strep pneumonia

Viral ——– Herpes, Influenza

Parasite —–Pneumocystis carinii pneumonia (PCP)

Fungi ——-Candida, Cryptococcus.

Transformation in Bacteria

Please explain transformation?

Direct uptake of donor DNA by recipient cells depends on their competence.

*Competence: The ability to take up DNA from the environment

*Some species have competence in nature

*Some can enter the competent state by treatment

Tetanus Acquisition and Pathogenesis

How is tetanus acquired? What is its pathogenesis?

Tetanus is acquired through exposure to the spores of the bacterium Clostridium tetani, which are universally present in the soil. The disease is caused by the action of a potent neurotoxin produced during the growth of the bacteria in dead tissues, e.g., in dirty wounds or in the umbilicus following non-sterile delivery.

Pathogenesis:

Infection of wound by spores
Germination of spores to bacilli
Bacilli produce toxin (tetanospasmin)
Toxins affect CNS and inhibit inhibitory mediators which are responsible for relaxation of muscles after contraction
So contraction prolongs

Sterilization vs. Disinfection

What is the difference between sterilization and disinfection?

Sterilization:

Completely destroys or removes all microbial life, including spores.

By physical or chemical process

Disinfection:

Killing, or removal of microorganisms that may cause disease

Viruses Transmitted by Sexual Contact

Which virus can be transmitted by sexual contact?

HIV
HPV
Hepatitis B

Morphological and Cultural Characteristics of Mycobacterium Tuberculosis

Describe the morphological and cultural characteristics of Mycobacterium tuberculosis?

Morphology:

Thin rods, acid-fast bacilli.

Cultural:

Obligate aerobic
Nutrition are high, Lowenstein-Jensen medium
It grows very slow with a generation time of 18 hours, colony, 3-4 weeks.
The rough colonies are granular, dull-yellow, dry.

Infection Sources and Transmission Routes of HBV

Describe the infection sources and transmission routes of HBV?

Infection source:

Patients with hepatitis B
Asymptomatic HBsAg carrier (ASC)

Transmission routes:

Via infected blood (or) blood products
Vertical transmission
Others (tightly contact & sex).

Spore of Bacterium

Please explain spore of bacterium?

Formed in response to adverse conditions
Sporulation occurs when nutrients are depleted
Inside the cell, mother cell autolysis
Contains bacterial DNA, a small amount of cytoplasm, cell membrane, peptidoglycan, very little water, a thick coat
A thick, keratin-like coat: responsible for the remarkable resistance of the spore to heat, dehydration, radiation, and chemicals.
Is a resting cell, the spore has no metabolic activity and remains dormant for many years
When returned to a favorable environment, the spore germinates to produce a single vegetative cell

Sterilization cannot be achieved by boiling
Patients can be infected by spore-forming organisms

Antigenic Shift and Antigenic Drift of Influenza Virus

Describe the antigenic shift and antigenic drift of influenza virus?

Antigenic shift:

Reassortment of genes is a common feature of influenza virus A, but not B or C
When two different”” viruses infect the same cell, their RNA segments can become mixed during replication
New viruses produced in this way may survive due to a selective advantage within the population

Antigenic drift:

Constant mutations in the RNA of influenza virus which lead to polypeptide mutations
Changes are less dramatic than those induced by shift
If these mutations affect HA or NA they may cause local epidemics.

Pathogenic Substances Produced by Staphylococcus Aureus

What are the pathogenic substances produced by Staphylococcus aureus?

Coagulase and clumping factor

Cause plasma to clot

Initiate fibrin polymerization deposit

Fibrin on the surface of bacteria

S. aureus is distinguished from the others primarily by coagulase production

Exotoxins
Toxic shock syndrome toxin
Enterotoxins

Diseases Caused by Salmonella

What disease can be caused by Salmonella?

Typhoid fever

Pathogenic Substances Produced by Meningococcus

What are the pathogenic substances produced by Meningococcus?

Localized infections

In men: Urethritis with dysuria and purulent discharge

In women: Purulent vaginal discharge, intermenstrual bleeding, ascending infection of the uterine tube, ectopic pregnancy (or) infertility.

Disseminated infection

– Arthritis

– Pustules

Newborn infants

– Purulent conjunctivitis

Neurotoxins

Which toxins are neurotoxins?

Botulinum toxin
Tetrodotoxin
Tetanus toxin
Nitric oxide
Chlorotoxin
Conotoxin
Lead
Ethanol
Glutamate
Arsenic mercury

Pathogenesis of Treponema Pallidum

Describe the pathogenesis of Treponema pallidum.

– Natural infection with T. pallidum occurs only in human beings

–Habitat: The human skin (or) mucous membrane

–Transmission:

Intimate contact (sexual contact), pregnant women to fetus via placenta.

– Produce no important toxins (or) enzymes.

–Diseases:- Syphilis (STD)

Acquire syphilis (venereal syphilis) – sexual contact

Primary syphilis – nontender ulcer

Secondary lesion – maculopapular rash

Tertiary syphilis – gumma

Congenital syphilis

Viruses Associated with Nasopharyngeal Carcinoma and Cervical Cancer

Which virus is associated with nasopharyngeal carcinoma, cervical cancer?

Nasopharyngeal — Epstein-Barr virus, CMV
Cervical cancer —-HPV

Viruses Causing Vertical Transmission

Which virus causes vertical transmission?

From mother to offspring through placenta, delivery, and suckling, such as HBV, HIV & HSV

Viruses Causing Congenital Malformations

Which viruses are the cause of congenital malformations?

Rubella, CMV, Herpes

Rabies Virus: Shape, Transmission, and Prevention

What shape of rabies virus, describe the transmission routes of rabies virus, how to prevent rabies?

Shape: Bullet
Transmission routes:

By biting or scratching of animals (through saliva)

Airborne (bats)

Prevention:

Handling the biting site – complete washing with solvent water, usage of disinfectant

Anti-viral sera

Usage of vaccine

Asepsis and Disinfection

What are asepsis and disinfection?

Asepsis:

Absence of pathogenic microbes

The technique that prevents bacteria from going to the body (or) other objects.