Microbiology Exam 4

What is normal skin microbiota?

microorganisms that are typically found on healthy human skin and are resistant to drying and high salt concentrations

Streptococcal (Group A streptococci (Streptococcus pyogenes)) Skin Infections:

Erysipelas: S. pyogenes infects the dermal layer of the skin, leading to local tissue destruction and sepsis

Necrotizing fasciitis ("flesh-eating" disease): Pyrogenic toxins produced by S. pyogenes act as a superantigen

Streptococcal toxic shock syndrome: Similar to staphylococcal TSS but more deadly, caused by S. pyogenes

Acne: Associated with Cutibacterium (Propionibacterium) acnes, which inhabits hair follicles and causes blockages with shed skin cells and sebum

Cutaneous Diphtheria: Corynebacterium diphtheriae can cause skin ulcers

Staphylococcal Skin Infections

Folliculitis: Infections of the hair follicles

Sty: Folliculitis of an eyelash

Furuncle (boil): A localized region of pus surrounded by inflamed tissue

Carbuncle: Damage and inflammation of deep tissue from a spreading furuncle

Impetigo: Crusting (nonbullous) sores, spread by autoinoculation

Scalded skin syndrome: A toxin causes exfoliation

Bullous impetigo

Toxic shock syndrome (TSS): Fever, vomiting, shock, and organ failure caused by toxin 1 (TSST-1) in the bloodstream

Viral Diseases of the Skin

Warts (Papillomas): Small skin growths, benign tumors, caused by Papillomavirus

Smallpox (Variola): Caused by an Orthropoxvirus

Monkeypox: Related to smallpox, jumps from animals to humans

Chickenpox (Varicella): Caused by Herpesvirus varicella-zoster (Human Herpesvirus 3, HHV-3), resulting in pus-filled vesicles

Shingles (Herpes Zoster): Reactivation of the latent varicella-zoster virus, causing painful pustular lesions over a dermatome

Herpes Simplex: Caused by Simplex virus Human herpesvirus 1 and 2 (HSV-1 and HSV-2), leading to cold sores or fever blisters (HSV-1) and genital herpes (HSV-2)

Measles (Rubeola): A viral disease transmitted by the respiratory route, characterized by a macular rash

German Measles (Rubella): Caused by the Rubella virus (Rubivirus), resulting in a macular rash and light fever

Fungal Diseases of the Skin and Nails (Mycoses)

Cutaneous Mycoses (Dermatomycoses or Tineas/Ringworm): Colonize the hair, nails, and outer epidermis.

Candidiasis: Overgrowth of Candida albicans (yeast) that can occur on the skin.

Arthropod-Associated Skin Diseases

Scabies: Caused by Sarcoptes scabiei mites that burrow in the skin, causing inflammatory skin lesions with intense itching.

Pediculosis (Lice): Caused by Pediculus humanus capitis (head louse) and P. corporis (body louse) that feed on blood and lay eggs on hair shafts.

Eye infections and the pathogens causing them

Conjunctivitis (pink eye): caused by Haemophilus influenza or pseudomonads associated with unsanitary handling of contact lenses.

Inclusion Conjunctivitis: caused by Chlamydia trachomatis. It can be transmitted to a newborn’s eyes during passage through the birth canal or spread through swimming pool water.

Ophthalmia neonatorum: caused by Neisseria gonorrhoeae. It involves the formation of a large amount of pus and can result in ulceration of the corneas leading to blindness. It is transmitted to a newborn’s eyes during passage through the birth canal and is prevented by treating a newborn’s eyes with antibiotics.

Trachoma: caused by Chlamydia trachomatis. The infection causes permanent scarring of the cornea, leading to blindness. It is the leading cause of blindness worldwide. Transmission occurs via hand contact or flies.

Ophthalmic Cysticercosis: occurs when the larvae of tapeworms lodge in the eye.

Terms used in skin diseases

Vesicles: These are defined as small, fluid-filled lesions on the skin

Macules: These are flat, reddened lesions on the skin.

Pustules: These are raised lesions with pus.

Impetigo: This is characterized by crusting (nonbullous) sores and is noted to spread by autoinoculation.

Meningitis by various pathogens

Bacterial Meningitis: Inflammation of the meninges, with initial symptoms of fever, headache, and a stiff neck, followed by nausea and vomiting, and potentially progressing to convulsions and coma. Death can occur from shock and inflammation.

Haemophilus influenzae Meningitis: Caused by Haemophilus influenzae, a gram-negative aerobic bacterium. Pathogenicity is due to capsule antigen type b2 . Occurs mostly in children (6 months to 4 years). Prevented by the Hib vaccine. Treatment involves broad-spectrum third-generation Cephalosporins

Meningococcal Meningitis: Caused by Neisseria meningitidis, an aerobic, Gram-negative diplococcus with a capsule. Transmission occurs via droplet aerosols and contact with secretions. Characterized by a rash that does not disappear when pressed. Symptoms are mostly caused by endotoxin. Treatment involves antibiotics. A vaccine is available.

Pneumococcal Meningitis: Caused by Streptococcus pneumoniae, a Gram-positive, encapsulated diplococcus. Most common in children (1 month to 4 years). Prevented by a conjugate vaccine. Treatment involves antibiotics.

Listeriosis: Caused by Listeria monocytogenes, a Gram-positive rod, usually through foodborne transmission. Can lead to sepsis and can infect pregnant women, crossing the placenta. Treatment is with Penicillin.

Viral Meningitis: More common and generally mild compared to bacterial meningitis.

Amoebic Meningoencephalitis: Caused by Naegleria fowleri, a protozoan that infects the nasal mucosa from swimming water, penetrates the brain, and feeds on brain tissues. It causes primary amebic meningoencephalitis (PAM), which is 100% fatal

Other Nervous System Diseases:

Leprosy (Hansen’s disease): Caused by Mycobacterium leprae and M. lepromatosis, acid-fast rods that grow best at 30°C. They grow in peripheral nerves and skin cells. Transmission requires prolonged contact. Symptoms include loss of sensation in skin areas (tuberculoid form) and disfiguring nodules over the body (lepromatous form) Diagnosed with a skin biopsy or smear. Treatment involves antibiotics (Dapsone, Rifampin, and Clofazimine) for 6 to 24 months.

Tetanus: Caused by Clostridium tetani, a Gram-positive, endospore-forming, obligate anaerobe. The tetanospasmin neurotoxin is released, blocking the relaxation pathway in muscles, causing muscle spasms. Death can occur from spasms of respiratory muscles. Prevented by vaccination with a tetanus toxoid (DTaP). Treatment includes tetanus immune globulin (TIG) and removal of infected tissue.

Rabies: Caused by the rabies virus (Lyssavirus). Usually transmitted by the saliva of an animal bite. The virus travels through the PNS to the brain cells, causing encephalitis. Negri bodies form in the brain stem. Initial symptoms include muscle spasms of the mouth and pharynx; hydrophobia. Diagnosed from bodily fluids with the direct fluorescent-antibody (DFA) test. There is a post-exposure prophylaxis involving rabies immunoglobulin and vaccine.

Botulism: Caused by Clostridium botulinum, a Gram-positive, endospore-forming, obligate anaerobe. Intoxication comes from ingesting the botulinal exotoxin, causing flaccid paralysis. Death usually results from respiratory or cardiac failure. Treatment includes respiratory assistance and antitoxins. Prevented with proper canning and the use of nitrites in foods. Infant botulism is associated with honey.

Mumps: Caused by Orthorubulavirus (mumps virus), targeting the salivary glands, causing painful swelling. Transmitted in saliva and respiratory secretions. May cause orchitis, meningitis, ovary inflammation, pancreatitis, and hearing loss. Prevented with the MMR vaccine.

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Diphtheria: Caused by Corynebacterium diphtheriae, a Gram-positive rod. Begins with sore throat and fever and forms a tough grayish membrane in the throat that can block breathing. An exotoxin damages the heart and kidneys. Cutaneous diphtheria forms skin ulcers. Treatment includes antibiotics + antitoxin. Prevented by the DTaP vaccine (Diphtheria toxoid).

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Cholera: Caused by Vibrio cholerae, a curved, gram-negative rod. Bacteria grow in the small intestine and produce cholera toxin, which causes host cells to secrete electrolytes and water, leading to “rice water stools” and severe fluid loss (12-20 liters per day). This can cause shock, collapse, organ failure, and death. Treatment includes IV fluid replacement. Prevention involves proper sanitation, water storage, and handwashing.

Mosquito-borne/Arboviral Encephalitis: Caused by arboviruses (arthropod-borne viruses), which are transmitted by mosquitoes.

Examples include Eastern equine encephalitis (EEE) and western equine encephalitis (WEE), which can cause brain damage, deafness, and neurological damage, with EEE having a high mortality rate.

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West Nile virus (WNV) is maintained in a bird-mosquito-bird cycle and can cause encephalitis.

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Zika Virus Disease is transmitted primarily by infected Aedes spp. mosquitoes and can cause conjunctivitis. Infection during pregnancy can lead to microcephaly.

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Prevention of arboviral encephalitis primarily involves controlling mosquito populations

Fungal and Protozoal Diseases

Fungal Meningitis (Cryptococcosis): Caused by Cryptococcus neoformans (as well as C. grubii and C. gattii), a soil fungus associated with pigeon and chicken droppings. Transmitted via the respiratory route and can spread to the CNS in immunocompromised individuals.

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Candidiasis: Caused by an overgrowth of the yeast Candida albicans on the skin and mucous membranes.

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Cutaneous Mycoses (Ringworm/Tineas): Caused by fungi that colonize the hair, nails, and outer epidermis. Examples include tinea capitis (scalp), tinea pedis (athlete's foot), and tinea unguium (nails)

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Histoplasmosis: Caused by the dimorphic fungus Histoplasma capsulatum, acquired from airborne conidia in areas with bird or bat droppings, causing lung lesions.

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Pneumocystis Pneumonia (PCP): Caused by the fungus Pneumocystis jirovecii, primarily affecting immunocompromised individuals.

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African Trypanosomiasis: Caused by trypanosomes, flagellated protozoa transmitted by tsetse flies, leading to CNS deterioration.

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Giardiasis: Caused by the flagellated protozoan Giardia duodenalis, causing prolonged diarrhea.

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Amebic Dysentery (Amebiasis): Caused by Entamoeba histolytica, leading to dysentery and potential liver abscesses31 ....

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Trichomoniasis: Caused by the protozoan Trichomonas vaginalis, a normal inhabitant that can cause vaginitis33 .

Diseases by Prion7 ...:

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Prions are self-replicating infectious proteins that cause normal proteins to become abnormally folded, leading to spongiform degeneration of brain tissue7 . These diseases are chronic and fatal34 .

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Examples include:

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Scrapie: TSE in sheep34 .

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Creutzfeldt-Jakob disease (CJD): TSE in humans34 .

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Kuru: TSE in humans caused by cannibalism34 .

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Bovine spongiform encephalopathy (BSE): Mad cow disease34 .

Some Fungal and Protozoal Diseases:

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Fungal Meningitis (Cryptococcosis): Caused by Cryptococcus neoformans (as well as C. grubii and C. gattii), a soil fungus associated with pigeon and chicken droppings23 . Transmitted via the respiratory route and can spread to the CNS in immunocompromised individuals23 .

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Candidiasis: Caused by an overgrowth of the yeast Candida albicans on the skin and mucous membranes24 ....

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Cutaneous Mycoses (Ringworm/Tineas): Caused by fungi that colonize the hair, nails, and outer epidermis26 . Examples include tinea capitis (scalp), tinea pedis (athlete's foot), and tinea unguium (nails)26 .

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Histoplasmosis: Caused by the dimorphic fungus Histoplasma capsulatum, acquired from airborne conidia in areas with bird or bat droppings, causing lung lesions27 ....

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Pneumocystis Pneumonia (PCP): Caused by the fungus Pneumocystis jirovecii, primarily affecting immunocompromised individuals28 .

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African Trypanosomiasis: Caused by trypanosomes, flagellated protozoa transmitted by tsetse flies, leading to CNS deterioration29 .

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Amoebic Meningeocephalitis: Caused by Naegleria fowleri, as mentioned earlier7 .

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Giardiasis: Caused by the flagellated protozoan Giardia duodenalis, causing prolonged diarrhea30 ....

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Amebic Dysentery (Amebiasis): Caused by Entamoeba histolytica, leading to dysentery and potential liver abscesses31 ....

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Trichomoniasis: Caused by the protozoan Trichomonas vaginalis, a normal inhabitant that can cause vaginitis.

Diseases by Prion

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Prions are self-replicating infectious proteins that cause normal proteins to become abnormally folded, leading to spongiform degeneration of brain tissue7 . These diseases are chronic and fatal34 .

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Examples include:

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Scrapie: TSE in sheep

Creutzfeldt-Jakob disease (CJD): TSE in humans.

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Kuru: TSE in humans caused by cannibalism.

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Bovine spongiform encephalopathy (BSE): Mad cow disease

Pharyngitis: sore throat. caused by Streptococcus pyogenes (Strep throat), leading to local inflammation, fever, tonsillitis, and enlarged lymph nodes.

Laryngitis is listed as one of the self-limiting diseases of the upper respiratory system.

Epiglottitis is described as the most life-threatening disease of the upper respiratory system and can be caused by opportunists such as Haemophilus influenzae type b.

Sinusitis is listed as one of the self-limiting diseases of the upper respiratory system.

What is otitis media?

infection of the middle ear. It involves the formation of pus that puts pressure on the eardrum. It can be caused by Streptococcus pneumoniae, nonencapsulated Haemophilus influenzae, Moraxella catarrhalis, S. pyogenes, and respiratory syncytial viruses. It is common in childhood due to the smaller auditory tube.

Respiratory diseases caused by Streptococcus pyogenes (group A):

Pharyngitis (Strep throat): Characterized by local inflammation, fever, tonsillitis, and enlarged lymph nodes. Diagnosis is through throat culture or rapid antigen detection tests.

Scarlet fever: Caused by S. pyogenes that produce an erythrogenic toxin due to lysogenization.

Diseases caused by *Corynebacterium diphtheriae

Diphtheria: Begins with a sore throat and fever. A tough grayish membrane forms in the throat, potentially blocking airflow. An exotoxin produced by lysogenized bacteria can circulate in the blood and damage the heart and kidneys. Cutaneous diphtheria can also occur, forming skin ulcers. Treatment involves antibiotics and antitoxin. It is prevented by the DTaP vaccine (Diphtheria toxoid).