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

Erysipelas

S. pyogenes (Group A streptococci) infects the dermal layer of the skin, leading to local tissue destruction and sepsis

Acne

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

Necrotizing fasciitis ("flesh-eating" disease)

Pyrogenic toxins produced by S. pyogenes (Group A streptococci) act as a superantigen

Streptococcal toxic shock syndrome

Similar to staphylococcal TSS but more deadly, caused by S. pyogenes (Group A streptococci)

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

Cutaneous Mycoses (Dermatomycoses or Tineas/Ringworm)

Colonize the hair, nails, and outer epidermis.

Scabies

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

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.

Mosquito-borne/Arboviral Encephalitis

Caused by arboviruses (arthropod-borne viruses), which are transmitted by mosquitoes.

Ex)

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.

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

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

Prions

Self-replicating infectious proteins that cause normal proteins to become abnormally folded, leading to spongiform degeneration of brain tissue.

Ex)

Scrapie: TSE in sheep.

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

Kuru: TSE in humans caused by cannibalism.

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.

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).

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

Pediculosis (Lice)

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

Candidiasis

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

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.

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.

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

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.

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.

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

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.

Pneumococcal Pneumonia

Caused by Streptococcus pneumoniae, a Gram-positive, encapsulated diplococcus. The infected alveoli of the lung fill with fluids and RBCs, interfering with oxygen uptake. It is treated with macrolides and prevented with a conjugated pneumococcal vaccine.

Mycoplasmal Pneumonia

Caused by Mycoplasma pneumoniae, which lacks a cell wall. It presents with mild but persistent respiratory symptoms, including low fever, cough, and headache. It is common in children and young adults and is also called primary atypical pneumonia or walking pneumonia. It is treated with tetracyclines.

Influenzae Pneumonia

Caused by Haemophilus influenzae, a Gram-negative coccobacillus. Symptoms resemble those of pneumococcal pneumonia. Children under 5 and adults over 65 are at higher risk. The Hib vaccine has significantly reduced its incidence in children. It is treated with third-generation cephalosporins.

Common Cold

Caused by over 200 different viruses, most commonly enterovirus rhinoviruses (30–50%) and coronaviruses (10–15%). Symptoms include sneezing, nasal secretion, and congestion, but it is not accompanied by fever. It can lead to laryngitis and otitis media. Antibiotics are ineffective; relief comes from cough suppressants and antihistamines.

COVID-19

Caused by Beta Coronavirus SARS-CoV-2. It was declared a pandemic in March 2020. The virus has a high mutation rate, leading to antigenic drift and the production of variants. Symptoms are not detailed extensively in this source beyond it being a respiratory syndrome caused by a coronavirus.

Influenza (Flu)

Caused by Influenzavirus, which contains eight RNA segments. Symptoms include chills, fever, headache, and muscle aches.

Influenza Antigenic Drift

Minor antigenic changes in Hemagglutinin (HA) and Neuraminidase (NA) spikes, allowing the virus to elude some host immunity.

Influenza Antigenic Shift

Major antigenic changes due to the reassortment of the eight RNA segments, great enough to evade most immunity and potentially lead to pandemics.

Pertussis/Whooping cough

Caused by Bordetella pertussis, a Gram-negative coccobacillus that produces a capsule. The bacteria attach to ciliated cells in the trachea, destroy them, and shut down the ciliary escalator. Tracheal cytotoxin damages ciliated cells, and pertussis toxin causes systemic symptoms. Prevented by the DTaP vaccine.

Stages:

1. Catarrhal stage: Resembles the common cold.

2. Paroxysmal stage: Characterized by violent coughing and gasping for air (whooping sound) and can last 1–6 weeks.

3. Convalescence stage: Can last for months

Tuberculosis

Caused by Mycobacterium tuberculosis, an acid-fast rod that is an obligate aerobe with a slow 20-hour generation time. Its cell wall lipids make it resistant to drying and antimicrobials.

Pathogenesis:

1. Inhaled organisms are phagocytized by alveolar macrophages, leading to an inflammatory response and the formation of tubercles.

   • If host defenses are adequate, the bacteria are isolated in these walled-off tubercles (latent TB, not infectious).

   • If defenses are inadequate, the tubercle breaks down, releasing bacteria into the lungs and other systems (infectious).

2. Diagnosis involves a tuberculin skin test (Mantoux test), followed by an X-ray or CT exam, acid-fast staining of sputum, and culturing of bacteria.

Cure: Treatment requires a minimum of 6 months of drug therapy due to the slow growth and dormancy of the bacteria. First-line drugs include isoniazid, rifampin, ethambutol, and pyrazinamide. The BCG vaccine (live, attenuated M. bovis) is widely used worldwide.

Histoplasmosis

Caused by Histoplasma capsulatum, a dimorphic fungus found in areas with bird or bat droppings. It forms lung lesions and can become a severe, generalized disease in a small percentage of cases. Treated with itraconazole.

Pneumocystis Pneumonia (PCP)

Caused by Pneumocystis jirovecii fungus, primarily affecting immunocompromised patients and a key indicator of AIDS.

Coccidiomycosis

Also known as Valley/San Joaquin fever, caused by Coccidioides immitis, a dimorphic fungus found in alkaline desert soils of the American Southwest. Most infections are not apparent, but some can cause fever, coughing, and weight loss.

Aspergillosis

Caused by Aspergillus fumigatus, an airborne fungus that can grow in compost piles.

Parts of digestive tract

mouth → pharynx (throat) → esophagus → stomach (fewest microbes) → and small and large intestine (most microbes). Accessory structures include the teeth, tongue, salivary glands, liver, gallbladder, and pancreas

Shigellosis

Caused by the genus Shigella, these are facultatively anaerobic, gram-negative bacilli. Transmission is person-to-person. Shigella produces the Shiga toxin, which destroys tissue. It has a small infectious dose. The bacteria attach to M cells, invade, and spread to other cells, causing damage to the intestinal wall. Symptoms include diarrhea, abdominal cramps, and fever

Salmonellosis

Caused by Salmonella enterica, which are gram-negative rods and facultative anaerobes found in human and animal intestinal tracts. Salmonella invades the intestinal mucosa and multiplies. It passes through M cells and enters the lymphoid and cardiovascular systems, replicating in macrophages. Symptoms, appearing after a 12 to 36-hour incubation, include fever, nausea, pain and cramps, and diarrhea. Salmonellosis is estimated to cause 1.35 million cases and 420 deaths annually. It is often associated with commercial chicken and egg production

Typhoid Fever

Caused by Salmonella serotype Typhi. It is spread only by human feces. The bacteria spread throughout the body in phagocytes, releasing the organism into the bloodstream. This can lead to high fever, headache, intestinal wall ulceration, and can be life-threatening. Diarrhea typically does not appear until the 2nd or 3rd week of the disease

Gingivitis

inflammation and infection of the gums, caused by Streptococci and Actinomycetes

Periodontitis

involves the destruction of the bone and tissue supporting the teeth caused by Porphyromonas

Ergot poisoning

Caused by mycotoxins produced by Claviceps purpurea, a fungus occurring in grains. Symptoms include restricting blood flow (leading to gangrene) and causing hallucinations.

Aflatoxin poisoning

Caused by mycotoxins produced by Aspergillus flavus which are found on peanuts. It causes liver cirrhosis and liver cancer.

GALT (Gut-associated lymphoid tissue)

70% of the immune system is located in the intestinal tract. Includes lymph nodes and Peyer’s patches

How does Helicobacter pylori effect the stomach?

It grows in the stomach acid by producing "Urease," which disrupts stomach mucosa, causing inflammation. This disruption leads to gastric and duodenal ulcers. Infection is also associated with an increased incidence of gastric cancer and ulceration.

Hepatitis B Virus

General symptoms can include fatigue, jaundice, nausea, and abdominal pain. Transmitted via the blood and bodily fluids. Can be prevented by a vaccine.

Dane particles: infectious complete virions

Spherical particles and filamentous particles lack DNA and are noninfectious. These particles contain hepatitis B surface antigen (HBsAg).

Normal biota of vagina

includes predominant microbes like Lactobacilli, Streptococci, anaerobes, some gram-negatives, and the yeast Candida albicans

Candidiasis

Fungal disease of the genital system caused by Candida albicans, which grows on the mucosa of the mouth, the intestinal tract, and the genitourinary tract.

C. albicans is an opportunistic pathogen, and its overgrowth can be precipitated by factors such as antibiotic use, diabetes, and hormones. A decrease in the number of Lactobacillus bacteria in the vagina tends to favor the growth of Candida albicans.

Vulvovaginal candidiasis results in a yeasty, thick, yellow discharge.

Cystitis

inflammation of the urinary bladder commonly caused by E. coli and Staphylococcus saprophyticus. Symptoms include dysuria and pyuria.

Predisposing factors in women include the short length of the urethra and its proximity to the anal opening

Pyelonephritis

inflammation of one or both kidney from an infection moving up the urinary tract. 75% of pyelonephritis cases are caused by E. coli4 . Symptoms include fever and back or flank pain. It generally results in bacteremia and can form scar tissue in the kidneys, becoming life-threatening

Urinary Tract Infection

Can include urethritis (inflammation of the urethra), cystitis (inflammation of the urinary bladder), ureteritis (infection of the ureters), and pyelonephritis (inflammation of one or both kidneys). Most are due to Escherichia coli and Staphylococcus saprophyticus

Genital Warts (condyloma acuminata)

Caused by human alpha papillomaviruses. Treatment includes removal of warts, podofilox and imiquimod. Can be prevented with the nine-valent HPV vaccines.

Chancroid (Soft Chancre)

Caused by Haemophilus ducreyi, a Gram-negative rod. Occurs most often in tropical areas.Symptoms include painful ulcers of the genitals and swollen lymph nodes in the groin. Factors in the sexual transmission of HIV. treated with Azithromycin or ceftriaxone

Gonorrhea

Caused by Neisseria gonorrhoeae, a Gram-negative diplococcus8 . Attaches to the epithelial mucosa by fimbriae and invades spaces between columnar epithelial cells (pharynx, eyes, rectum, urethra, cervix, external genitalia of prepubertal females), causing inflammation and forming pus. Treated with Ceftriaxone

Complications: If left untreated, it may disseminate and become systemic, causing Endocarditis, Meningitis, or Arthritis. Ophthalmia neonatorum is an infant eye infection acquired at birth if the mother has a genital infection.

African Trypanosomiasis

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

Giardiasis

Caused by the flagellated protozoan Giardia duodenalis, causing prolonged diarrhea

Amebic Dysentery (Amebiasis)

Caused by Entamoeba histolytica, leading to dysentery and potential liver abscesses

Trichomoniasis

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