ID from Rubin's Q and A Flashcards
Cat-scratch disease; bartonella henselae
Self-limited granulomatous lymphadenitis; g- rods difficult to see without silver stain; associated with cats; claws allow organism to enter as do conjuctiva; common childhood infection; suppurative and granulomatous lymphadenitis,nodes enlarged for 3-4 months, usually stays in local lymphnodes; multiply in walls of inoculation site; parinaud oculoglandular syndrome (preauricular adenopathy secondary to conjunctival infection); antibiotics don’t help.
Streptococcus pyogenes
Group A, causes the nonsuppurative diseases rheumatic fever and poststreptococcal glomerulonephritis. Causes suppurative diseases. Causes strep throat, scarlet fever (punctate red rash in pharyngitis, tongue has yellow-white coating, caused by erythrogenic toxin), erysipelas (erythematous swelling of the skin, begins on face, acute inflammatory rxn), impetigo/pyoderma (intraepidermal infection, purulent exudate, red papules then pustules, then honey-colored crust), cellulitis, and puerperal sepsis (post-partum infection of uterine cavity). Can cause sub-acute endocarditis
Bacillus anthracis
Rapidly fatal on dissemination; sheep, goats, cattle and their byproducts. G+ spore forming; spores are highly resistant and can reside in soil; cutanious anthrax can be eliminated if nectrotizing toxin fails to allow dissemination; black scabs with only minor infiltrate; Forms: malignant pustule=95% all anthrax, ulcer with purulent purple/black exudate…pumonary anthrax: super dangerous form.. septicemic anthrax can occur in either case..gastrointestinal anthrax rare
Leishmaniasis
Protozoan infection transmitted by insect bites, particularly sandflies. Localized cutaneous leishmaniasis: Protozoa invade macrophages and ulcerate the overlying skin, which eventually becomes a granuloma. It forms an itching, solitary papule which erodes to become the ulcer with a sharp, raised border. Diffuse cutaneous can form with multiple nodules and look like leprosy. Mucocutaneous leishmaniasis: Leishmania braziliensis; Ulcer expands and resolves, then an ulcer develops at a mucocutaneous junction, like larynx, nasal septum, anus or vulva. It erodes mucosal surfaces, can destroy the nasal septum. Visceral leishmaniasis: Disease spreads tough mononuclear phagocyte system; Liver, spleen, and lymph nodes become enlarged as macrophages get parasitized. Weight loss, hepatosplenomegaly, anemia, thrombocytopenia, and skin darkening.
Rocky Mountain Spotted Fever (rickettsia rickettsi)
Acute, systemic vasculitis transmitted through tick bites. Rash produced by inflammatory damage to cutaneous vessels, spreads to vascular smooth muscle and large vessels. Exudation of fluid and DIC. Rash begins as maculopapular but extends to be petechial, from the distal extremities to the trunk.
Giardiasis (giardia lamblia)
Protozoan infection causing infection of the small intestine. They attach to small bowel epithelia and have no grossly visible alterations. Usually a harmless commensal; can cause acute abdominal cramping and frequent, foul-smelling stools. Chronic infection in children may cause malabsorption.
PCP/Pneumocystis jiroveci
Fungus, causes pneumonia in people with impaired immunity, especially AIDS. Causes progressive consolidation of the lungs. Best visualized with silver. Progressive shortness of breathm, non-productive cough.
Entamoeba histolytica (Amebiasis)
Usually lysis the colon and occasionally the liver. Acquired by ingestion of materials contaminated with human feces. Has pre cyst and infective cyst stages. Grow in the colon, forming lesions and ulcers, sloughing of mucosa. Ameboma occurs when the amebae invade through the intestinal wall. Liquid stools with bloody mucus. If the amebas enter the veins they get to the liver through the portal circulation, killing hepatocytes and producing a necrotic cavity, dark/brown “anchovy paste” material.
C. perfringens (gas gangrene)
Necrotizing, gas forming infection. Myotoxin liquefies muscles, skin becomes tense. Necrosis with few neutrophils which are destroyed. Skin darkens because of hemorrhage and cutaneous necrosis. Discharge with gas bubbles.
Tuberculosis
Mycobacteria tuberculosis, stain with acid fast. Chronic, communicable disease with lungs as the primary target. Causes a spherical granuloma with central caseous necrosis (Ghon focus). Transmitted via aerosolized droplets. Live in macrophages but resist killing by blocking lysosome fusion. Usually self-limited primary TB, Ghon complexes heal, leaving scarring and calcification. In progressive primary TB, Ghon focus enlarges, middle lobe of lung can collapse. Produces fever, weight loss, and night sweats. Miliary TB occurs when infection produces multiple lesions in several organs; seeding. Secondary TB is a proliferation in someone who had previously contained the infection. Immune response leads to necrosis and production of TB cavities. Cough with hemoptysis, night sweats.
Rickettsia typhi (Endemic/Murine Typhus)
Transmitted through fleas, can cause pulmonary infection or attack endothelial cells and cause necrotizing vasculitis. Associated with rat-infested dwellings.
C. difficile
Produces an acute necrotizing colitis after antibiotic administration. Produces exotoxins that kill cells and cause fluid secretion. Pseudomembrane of cellular debris, neutrophils, and fibrin forms over infected areas of colon.
E. coli diarrhea
Gram. neg. Enterotoxigenic: traveler’s diarrhea Enteropathogenic: diarrhea in poor tropical area, deforms microvilli. enterohemorrhagic: bloody diarrhea from contaminated meat or milk, hemolytic-uremic syndrome, destroys epithelial cells. Enteroinvase: dysentery, inflammation and erosion of mucosae, similar to Shigella.
Respiratory Syncytial Virus
RNA,Bronchiolitis or pneumonitis in children, wheezing, cough, respiratory distress. Causes most problems in children, mild illness in adults
Syphilis (Treponema pallidum)
Spirochete; STD; chronic; systemic infection; proliferates at site of infection, enters lymph, then blood, long term systemic damage; Stages: Primary Syphilis: Chancres at site of entry with luetic vasculitis; Secondary Syphilis: systemic spread with maculopapular rash on trunk/extremities (palms and soles), see lesion types; Tertiary syphilis: disease goes dormant for years or decades then focal ischemic necrosis is responsible for many damaged sites Syphilitic aortitis: aortic media nectrosis and aneurysm danger likely and aortic valve insufficiency; Neurosyphilis: damage meninges and CNS via progressive infection (see damage types); Benign tertiary syphillis: Gummas of coagulative (granulomatous) necrosis (dont significantly damage); Congenital syphilis is transmitted from an infected mother to the fetus: stillbirth, neonatal illness or death: snuffles and deformed bones/teeth Rx: penicillin
Salmonella typhi (typhoid fever)
Acute systemic illness spread by contaminated water and food (dairy and shellfish). Attaches to small-bowel mucosa, invades ileum over Peyer patches. Multiply within macrophages. Systemic dissemination leads to typhoid nodules, granulomas in liver and spleen that are aggregates of macrophages. Malaise, headache, abdominal pain, fever, spleno and hepatomegaly, GI bleeding.
Chagas disease (Trypanosoma cruzi)
Protozoa replicate in macrophages and invade cardiac myocytes and brain. Forms localized nodular inflammatory lesions, called chagomas. Acute: enlarges heart, hemorrhagic myocardium, can invade meninges. Chronic: chronic inflammation damages organs; chronic myocarditis, deviated interventricular septum, can cause heart failure. Megaesophague and megacolon can develop because the parasympathetic ganglia and myenteric plexus get destroyed. Congenital: leads to spontaneous abortion or fatal encephalitis
Parvovirus
DNA, causes benign erythema infectiosum/5th disease (slapped-cheek, lacy rash), interrupts erythropoiesis. If pt has chronic hemolytic anemia (sickle cell) can cause a potentially fatal anemia called transient aplastic crisis. Nuclei are enlarged with glassy eosinophilic material nuclear inclusion bodies
Strep pneumoniae (pneumococus)
Gram positive, causes lobar pneumonia with rust colored sputum, otitis media, sinusitis, and meningitis. Organism gains access to sterile sites, usually after a viral infection. Capsule prevents alternative complement pathway, no phagocytes.
Haemophilus Influenzae
Gram negative coccobacillus. Leading cause of meningitis in children under 2. Unencapsulated spread to sterile sites after a virus has destroyed defense mechanisms, eliciting inflammatory responses. Encapsulated bacteria invade tissues, causing bacteremia, bronchopneumonia or lobar pneumonia (lime-green sputum), epiglottitis, septic arthritis, and facial cellulitis (hot, red-blue colored area in cheek or above eye). Vaccine. Childhood.
Legionella pneumophila (Legionnaire’s and Pontiac fever)
Gram neg, stains poorly. In water, inhaled aerosols, cooling towers. Bacteria phagocytosed by macrophages, replicate and protect themselves by blocking lysosomes from fusing. They are released and infect new macrophages. Causes acute atypical bronchopneumonia, obtunded and hypoxia may be prominent. Pontiac fever is a flu-like illness, no evidence of consolidation.
MAI; mycobacterium avium and intracellulare
In immunocompetent people, produces a granulomatous pulmonary disease, resembling TB but progressing much more slowly. Causes pulmonary nodules, cavities, and caseating granulomas. COPD predisposes to it, cough is common but missing other TB symptoms. Opportunistic infection in AIDS (3rd most common opportunistic) due to lack of T cells. Infected macrophages accumulate everywhere. Symptoms similar to TB, including small-bowel involvement with pain and diarrhea.
Trichonosis (trichinella spiralis)
Roundworm, acquired by eating inadequately cooked pork that contains skeletal muscle with larvae. Cysts in muscle cause myositis, and extreme eosinophilia. Most infections are asymptomatic, symptomatic is self-limited. Abdominal pain and diarrhea are possible. Infection of the brain and myocardium are also possible.
E. coli UTI, pneumonia, sepsis, and meningitis.
Fecal contamination of UT, sexual intercourse. Ascends from distal urethra, adhere to epithelium. Can ascend to kidneys and cause pyelonephritis. Pneumonia: opportunistic, make salivary protease that degrades fibronectin so gram-neg can overcome gram-positive flora in mouth, proliferation of aspirated organisms. Sepsis: most common cause of enteric gram-neg; opportunistic, neutrophils cant phagocytose bacteria. Also can cause meningitis
