Microbiology Quiz on Chlamydia and Pathogenicity

Pathogens

• Pathogens are organisms that cause disease.
• Different types of pathogens and the severity of diseases they cause vary significantly.
• Examples include bacteria, viruses, fungi, and parasites.

Pathogenicity

• Pathogenicity is the ability to cause disease.
• Related terms include virulence, which measures the degree of pathogenicity for a specific organism.
• Key characteristics of pathogenicity include invasiveness, infectivity, pathogenic potential, and toxigenicity.

Determinants of Pathogenicity

• A pathogen must achieve specific steps to cause disease.
• These steps include reaching the host, adhering to/colonizing/invading the host, multiplying in the host, evading host defenses, and damaging the host mechanically, chemically, or molecularly.

Transmission

• Direct contact transmission occurs from host to host (e.g., sneezing).
• Indirect contact involves contamination of inanimate objects.
• Droplet transmission involves coughs and sneezes.
• Food and waterborne transmission is another method.
• Vector transmission uses mosquitos or ticks to carry pathogens.

Route of Entry for Invading Pathogen

• Pathogens can enter through the skin or mucous membranes.

Adhesion and Colonization

• Adhesion is the ability of pathogenic microbes to attach to body cells.
• Adhesins are specialized molecules or structures on pathogens that bind to complimentary receptor sites on host cells.
• Examples of adhesins include glycocalyx, filamentous hemagglutinin, fimbrae, lectin, pili, S-layer, teichoic acids, and lipoteichoic acids.

Entry of Pathogen (Invasion)

• Successful adhesion allows pathogens to invade cells.
• This invasion often involves producing toxins.
• Toxins attack ground substance and basement membranes.
• To penetrate the epithelium, pathogens are involved with cell surface disruption and the degrading of protein-carbohydrate complexes.

Entry of Pathogen (Invasion-2)

• Some pathogens use passive mechanisms to enter cells that aren't directly related to the pathogen itself.
• Lesions or ulcers form in mucous membranes due to external factors other than the pathogen.
• Some organisms can use internalization (endocytosis) to enter host cells.

Toxigenicity (Virulence Factors)

• Exotoxins are among the deadliest substances and are associated with specific diseases.
• Exotoxins include neurotoxins, cytotoxins, and enterotoxins.
• Endotoxins, toxic in large quantities, are highly associated with a host response (i.e., fever, inflammation).
• Endotoxins also can cause shock, blood coagulation, weakness, diarrhea, inflammation, intestinal hemorrhage, and fibrinolysis.

Evasion of Host Immune System

• Pathogens use various mechanisms to evade the host's immune system.
• They can mimic host molecules, develop cysts, and bind to factors in plasma.
• Leukocidins cause degranulation of lysosomes.
• Some bind to immunoglobulins (by the Fc end).
• Lastly, pathogens produce porins to evade phagocytosis.

Infection

• Successful pathogen multiplication leads to infection.
• Infections can be classified as local, focal, or systemic based on their extent.
• Local infection is confined to a small area, often near the entry point (i.e., pneumonia confined to the lungs).
• Focal infection occurs when a localized pathogen or its toxin spreads to a secondary area (i.e., a dental infection spreading).
• Systemic infection is when an infection spreads throughout the body (i.e., multiple STIs spreading).

Sexually Transmitted Infections (STIs)

• STIs include different types of infections caused via sexual contact.
• Examples of bacterial STIs include Chlamydia, Gonorrhea, and Syphilis.
• Examples of viral STIs include Genital Warts, Genital Herpes, HIV/AIDS, and HPV.
• Examples of fungal STIs include Thrush.
• Examples of parasitic STIs include Scabies, Public Lice, and Trichomonas vaginalis.

Chlamydia

• One of the most common STIs in the UK.
• Gram-negative bacterium that lacks peptidoglycan.
• Non-motile.
• Smallest bacterium with two forms: Elementary Bodies (EB) and Reticulate Bodies (RB).
• Intracellular pathogen that requires host cells for ATP production.
• Three species cause disease (Chlamydia trachomatis, Chlamydia pneumoniae, and Chlamydia psittaci).
• Infects via abrasions/lacerations and limited cell arrays.

Chlamydia Life Cycle

• Alternates between intracellular, non-infectious Reticulate Body (RB) and extracellular, infectious Elementary Body (EB).

Elementary Bodies

• Small (0.2-0.4 µm).
• Dormant; resistant to environmental extremes.
• Infective form, enter via abrasions/lacerations.

Reticulate Bodies

• Larger (0.6-1.5 µm).
• Non-infective, intracellular form.
• Replicates through binary fission within phagosomes.

Chlamydia Disease

• Enters host cells via abrasions and lacerations.
• Infection leads to inflammatory response at the infection site.
• Can lead to blindness, sterility, or other sexual dysfunction.
• Symptoms: usually asymptomatic in women with an unusual vaginal discharge, pain when urinating, low abdominal pain, and bleeding between periods.
• Symptoms in men: typically symptomatic (75%), include a white/cloudy watery discharge, pain or burning sensation when urinating, and testicular pain or swelling.

Gonorrhea

• Gram-negative diplococci, True pathogen, Second most common STI.
• Infects mucosal membranes of genitals, urethra, digestive tract, cervix, vagina, uterus, rectum, and/or pharynx.
• Spreads through the bloodstream and causes infections of joints, heart, and meninges.
• Can be passed to a child at birth, infecting the cornea.
• Usually sexually transmitted.
• Symptoms in men: Insufferably symptomatic, Acute inflammation, Painful urination, Purulent discharge.
• Symptoms in women: Often asymptomatic, Often mistaken for bladder infection, Infects cervix.

Syphilis

• Specific group work questions in lectures.

Non-Gonococcal Urethritis

• Inflammation causes a painful/burning sensation when urinating.
• Tip of penis becomes irritated and sore.
• White or cloudy discharge.

Genital Herpes

• Caused by human herpes viruses (HHV).
• Double-stranded DNA, icosahedral capsid, enveloped.
• 150-200 nm diameter.
• HSV-1 (15%) and HSV-2 (85%) cause genital lesions.
• Active lesions are a usual source of infection.
• The virus enters the body through a break in tissue or a laceration.
• Binds to epithelial cells and enters the host cell to reproduce.
• Reproduction causes inflammation and cell death.
• Infected cells fuse to neighboring uninfected cells. (forming a syncytium), causing a painful lesion.
• Type 1 (HSV-1) is usually spread verbally and causes oral herpes.
• Type 2 (HSV-2) is usually spread sexually and causes genital herpes.
• Neonatal herpes is a concern with fetus and birth; 30% fatality if the infection spreads to cutaneous/oral cells and 80% fatality if the infection spread to central nervous system.

Diagnosis & Treatment for Viral STIs

• Diagnosis is based on characteristic lesions.
• Direct examination of tissue reveals syncytia.
• Serology testing for antibodies to specific viral antigens helps with accurate diagnosis.
• Treatment involves antiviral drugs (e.g., acyclovir, valaciclovir, iododeoxyuridine, etc).
• Treatment effectiveness is generally 6–12 months after infection.
• People with lesions should abstain from sexual intercourse.

Diagnosis & Treatment for Bacterial STIs

• Diagnosis includes urine tests or swabs to detect bacteria in host cells.
• Treatment commonly involves antibiotics (e.g., azithromycin, doxycycline, erythromycin).

Additional Notes

• Group activities cover topics like why penicillin and cephalosporins aren't suited for chlamydia treatment, microbe identification, disease spread and prevention, and treatment plans.

Test your knowledge on chlamydia infection symptoms, treatments, and the characteristics of various pathogens. This quiz covers essential concepts in microbiology, including virulence and pathogenicity. Perfect for students studying infectious diseases and microbiological principles.