Microbiology 311: Pathogens, Mechanisms, and Clinical Conditions

Comprehensive vocabulary flashcards covering pathogens, clinical signs, mechanisms, and virulence factors for eye, skin, nervous system, and cardiovascular/lymphatic infections from Microbiology 311.

Trachoma

A bacterial eye infection caused by Chlamydia trachomatis that can occur in both eyes; it has a low incidence in the US but remains a major cause of blindness worldwide.

Keratitis

Inflammation and invasion of the cornea caused by viral agents such as HSV-1 and HSV-2 or protozoans such as Acanthamoeba.

River Blindness

A condition caused by the helminth Onchocerca volvulus (a parasitic worm) transmitted by the black fly; endemic to Middle Africa, Mexico, and upper South America.

Meningitis

Inflammation of the protective membrane layers wrapping the brain and spinal cord; the bacterial form presents a rapid, life-threatening onset and is more serious than viral meningitis.

Encephalitis

Inflammation of the brain tissue itself that can lead to severe cognitive shifts, coma, or death.

Meningoencephalitis

Concurrent inflammation affecting both the brain tissue and its surrounding membranes, commonly associated with primary amoebic infections.

Cerebrospinal Fluid (CSF) Circulation

The physiological fluid path where CSF is produced in the choroid plexus and flows out through arachnoid villi to the dural venous sinuses; diagnostic shifts in its clarity, pressure, or WBCs indicate meningitis.

Neisseria meningitidis

Gram-negative diplococci transmitted via respiratory droplets in close contact quarters (such as dorms and barracks); primarily affects teens and releases endotoxin that causes vascular damage, light sensitivity, fever, and a stiff neck.

Streptococcus pneumoniae (Meningitis Profile)

Gram-positive cocci colonizing and crossing into the CNS in teens with reduced overall health; possesses a $30\%$ carriage rate, over $90$ serotypes, and an available preventive vaccine.

Haemophilus influenzae type B

Invasive Gram-negative bacterial pathogen that penetrates nerve cells to enter the CNS in babies; humans are its only reservoir, and it is heavily controlled by the Hib vaccine.

Group B Streptococcus

Gram-positive cocci vertically transmitted from mother to infant during childbirth; represents a primary demographic risk for neonatal sepsis and bacterial meningitis in newborns.

Listeria monocytogenes

Foodborne Gram-positive rod common in soil and water that grows well at refrigerator temperatures; linked to contaminated deli meats and raw milk, causing adult meningitis and spontaneous abortion in pregnant individuals.

Viral Meningitis

Systemic viral migration (most often enteroviruses, HSV, or arboviruses) accounting for $4$ out of $5$ meningitis cases; runs a milder clinical course than bacterial meningitis with a mortality rate of $< 1\%$.

Primary Amoebic Meningoencephalitis (PAM)

A rare but highly fatal CNS condition caused by the amoeba Naegleria fowleri, which enters nasal passages during warm freshwater recreational activities and migrates directly to the brain.

Granulomatous Amoebic Meningoencephalitis (GAM)

An opportunistic CNS infection caused by Acanthamoeba species found in environmental soil and water; produces a subacute or chronic progression of neurological deficits and granulomas.

Arboviral Encephalitis

A mosquito-borne viral encephalitis prevalent during warm summer months ($95\%$ West Nile virus); presents with fever, chills, and headache, and can advance to coma, death, or long-term neurological sequelae.

Coccidioides

A dimorphic environmental fungal pathogen whose inhaled spores cause fungal meningitis; exists as arthrospores at $25\,^{\circ}\text{C}$ and transforms into spherules at $37\,^{\circ}\text{C}$.

Cryptococcus neoformans

An encapsulated airborne yeast associated with dried bird droppings; inhaled spores target immunocompromised individuals to produce cryptococcosis and fungal meningitis.

Botulism

Flaccid paralysis caused by the Gram-positive, obligate anaerobic endospore-former Clostridium botulinum; produces an exotoxin that blocks acetylcholine release at the neuromuscular junction, carries infant risk via honey, and can cause wound infections mimicking gangrene.

Tetanus

A neurological condition caused by Clostridium tetani, an obligate anaerobic Gram-positive soil rod that secretes the neurotoxin tetanospasmin; clinical hallmarks include rigid spasms, opisthotonos (severe back arching), and death via respiratory failure.

Poliomyelitis

A disease caused by poliovirus (a $+\text{ssRNA}$ picornavirus) transmitted through oral ingestion; multiplies in the throat and small intestine before $1\%$ penetrates the CNS to cause paralytic disease lasting up to $6$ months.

Salk Vaccine vs. Sabin Vaccine

The two polio vaccine formulations: Salk ($1955$) is an inactivated injected vaccine requiring multiple doses, while Sabin ($1963$) is an oral live-attenuated vaccine that provides lifelong immunity.

African Sleeping Sickness

A progressive neurological protozoan disease caused by Trypanosoma brucei (gambiense and rhodesiense) and spread by the tsetse fly; evades host immunity via antigenic shift and is treated with Melarsoprol ($1\text{--}5\%$ fatal toxicity) or Eflornithine.

Toxoplasmosis

A condition caused by the spore-forming protozoan Toxoplasma gondii, which cycles through sporozoite, tachyzoite, and bradyzoite stages; produces slow-onset subacute encephalitis and poses severe hazards to fetuses and immunocompromised individuals.

Transmissible Spongiform Encephalopathies (TSE)

Fatal, chronic neurodegenerative disorders caused by abnormally folded prion proteins aggregating in brain tissue and forming microscopic holes; examples include Kuru, Creutzfeldt-Jakob Syndrome (CJD), Scrapie, Mad Cow Disease, and Chronic Wasting Disease.

Zika Virus

A Flaviviridae mosquito-borne and sexually transmitted virus that causes joint pain and rash; associated with Guillain-Barré syndrome and Congenital Zika Syndrome resulting in fetal microcephaly.

Rabies Virus

A neurotropic Rhabdovirus transmitted via animal bites that migrates through peripheral nerves to the CNS; manifests in furious or paralytic forms and requires post-exposure passive and active immunization.

Sepsis / Septicemia

A systemic inflammatory response triggered by circulating pathogens or toxins, presenting with elevated WBC counts, RBC lysis, and lymphangitis; Gram-negative cases are driven by LPS-induced blood pressure drops, while Gram-positive cases are mediated by exotoxins.

Septic Shock

A downstream critical collapse of the vascular system resulting from uncontrolled loss of blood pressure during systemic infection; includes puerperal sepsis (childbirth fever).

Lyme Disease

A tick-borne infection caused by the spirochete Borrelia burgdorferi transmitted by Ixodes ticks; progresses through three stages: $1^{\text{st}}$ stage (bullseye rash and flu-like symptoms), $2^{\text{nd}}$ stage (irregular heartbeat, neurological deficits, and meningitis), and $3^{\text{rd}}$ stage (arthritis).

Infectious Mononucleosis

A viral infection caused by the Epstein-Barr Virus (EBV) transmitted through saliva and shared drinks; selectively targets B-lymphocytes, leading to fatigue, splenomegaly, and swollen lymph nodes.

Yersinia pestis

A Gram-negative rod causing the Plague (Black Death), transmitted from rats to humans by the flea vector Xenopsylla cheopis; activates both endotoxins and exotoxins to induce high fever and buboes across bubonic, septicemic, and pneumonic forms.

Tularemia

A zoonotic infection caused by the Gram-negative bacillus Francisella tularensis, acquired through infected animal contact, vector bites, or inhalation; nicknamed 'lawnmower disease' due to aerosol risks and classified as a potential bioterrorism agent.

Staphylococcus aureus (Skin Presentations)

Gram-positive, hemolysin-positive, and coagulase-positive bacterium that utilizes streptokinase, hyaluronidase, and lipases to produce localized cutaneous lesions and crusting impetigo sores.

Necrotizing Fasciitis

A rapidly destructive deep-tissue infection caused by Staphylococcus and Streptococcus species; driven by tissue-degrading enzymes and superantigens, leading to extensive tissue death and extreme pain.

Group A Strep (GAS)

An aggressive bacterial lineage that employs surface M-protein to resist host acidity and evade phagocytosis; causes invasive systemic disease with an estimated $40\%$ mortality rate.

Toxic Shock Syndrome (TSS)

Acute systemic shock triggered by toxigenic strains of Staphylococcus aureus producing TSST-1 (a superantigen); characterized by high fever, vomiting, diffuse rash, rapid organ failure, and death.

Gas Gangrene

Soft tissue necrosis resulting from interrupted blood supply (ischemia) and infection by Clostridium perfringens; the anaerobic, spore-forming rod degrades collagen, invades the bloodstream, and ferments tissue into gas.

Human Papillomavirus (HPV)

A family of over $50$ distinct viral types that infect epithelial cells, generating benign skin warts; includes three specific viral types noted on abnormal Pap smears for their association with cervical tissue changes.

Varicella-Zoster Virus (HHV-3)

A neurotropic virus that causes chickenpox upon initial infection and establishes long-term latency in thoracic nerves ($\text{T1 to T12}$); reactivates as shingles, producing a crawling sensation and localized painful rash.

Smallpox Virus (Variola)

A virulent orthopoxvirus that replicates extensively in internal organs before erupting into cutaneous lesions; divided into Variola Major ($20\%$ mortality) and Variola Minor ($< 1\%$ mortality).

Measles Virus

A highly contagious $-\text{ssRNA}$ Paramyxoviridae virus that causes a severe rash, erases host immune memory, and risks late-onset fatal complications $7\text{--}10$ years later; responsible for approximately $400$ daily deaths in developing nations.

Leishmania Species Spectrum

Sandfly-transmitted protozoan parasites presenting in three distinct forms: L. donovani (visceral leishmaniasis damaging internal organs), L. tropica (cutaneous ulcerative lesions), and L. braziliensis (mucocutaneous degradation of oral and nasal membranes).

Dermatophytes (Tineas)

Specialized pathogenic fungi that infect keratinized tissue (hair, nails, stratum corneum); categorized clinically into Tinea capitis (scalp), Tinea cruris (groin/jock itch), and Tinea pedis (feet/athlete's foot).

Candida albicans

An opportunistic yeast that colonizes mucous membranes when normal flora is disrupted (such as after antibiotic courses), producing oral thrush marked by thick white patches on the tongue.