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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.
Trichonosis (trichinella spiralis)
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.
C. perfringens (gas gangrene)
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.
C. difficile
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
Chagas disease (Trypanosoma cruzi)
DNA, congenital and opportunistic infection. Fetal: transmitted across the placents, affects brain, inner ears, eyes, causing neurological or hearing defects. Immunocompromised/transplant: varied reaction. Pathology: owl eyed appearance of cells due to giant nucleus with a central inclusion surrounded by a clear zone
Cytomegalovirus
Greatest worm cause of morbidity. Hatches in water, enters snail, then penetrates human skin. Basic lesion is a circumscribed granuloma or a cellular infiltrate of eosinophils and neutrophils around an egg. S. mansoni: inferior mesenteric vein, distal colon and liver. S. haematobium: veins of rectum, bladder, and pelvic organs S. japonicum: superior mesenteric vein, damaging small bowel, ascending colon and liver. Mansoni and japonicum cause liver disease with fibrosis and portal hypertension. Haematobium: inflammatory reaction may obstruct urine flow, cause squamous cell carcinoma of the bladder.
Schistosomiasis
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.
Cat-scratch disease; bartonella henselae
Mosquito-borne, hemolytic, febrile illness caused by protozoa. Destroys RBC, causing chills, dever, anemia and splenomegaly. P. falciparum causes malignant malaria; no hepatic stage, parasitizes RBC of any age, not just old or young, so there is marked parasitemia and anemia. There may be several parasites per cell. Causes infected RBC to adhere to endothelial cells, obstruction produces ischemia. Hepatosplenomegaly as RBC are sequestered. Paroxysms of chills and high fever.
Malaria. Plasmodium vivax, ovale, falciparum, malarie.
Transmitted through fleas, can cause pulmonary infection or attack endothelial cells and cause necrotizing vasculitis. Associated with rat-infested dwellings.
Rickettsia typhi (Endemic/Murine Typhus)
Spirochete C. Trachomatis: genital epithelial infections; urethritis, up to PID in women. Can also cause inclusion conjunctivitis Many infections are asymptomatic. Also can cause lymphogranuloma venereum; genital ulcer that spreads to lymph nodes and causes a necrotizing lymphadenitis. Can cause trachoma blindness. C. psittaci: pneumonia transmitted to humans from birds. C. pneumoniae: usually causes mild respiratory infections, only continuing to severe pneumonia if there is an underlying pulmonary condition.
Chlamydia
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.
E. coli diarrhea
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
E. coli UTI, pneumonia, sepsis, and meningitis.
RNA, causes URI and LRI, causes croup, characterized by stridor on inspiration and a “barking” cough due to edema of laryngotracheitis.
Parainfluenza
Gram neg bacilli, nosocomial necrotizing lobar pneumonia with currant jelly sputum, inhaled into lungs, exudate accumulates, compressed and necrotic walls; leads to cavitation. Thick mucoid sputum forms.
Klebsiella and Enterobacter
Release of toxin after organism from soil infects deep wound. Toxin passes thru ventral roots, binds to motor neurons, cleaves protein to mediate exocytosis of synaptic vesicles; release of inhibitory neurotransmitters is blocked, contraction of muscles (tetany). Lockjaw after 1-3 weeks, risus sardonicus (fixed grin) and opisthotonos (backward arching)
C. tetani
Gram-negative rod, spread by polluted water. Produes the exotoxin cholera toxin, does not invade mucosa of intestine. Toxin increases cAMP, causing secretion of sodium and water into lumen of small bowel. Stools are flecked with mucus (rice-water), oral rehydration is necessary. Vibrio parahaemolyticus causes acute gastroenteritis from poorly cooked seafood.
Vibrio cholerae (Cholera)
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
Bacillus anthracis
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.
MAI; mycobacterium avium and intracellulare
Causes neonatal pneumonia, meningitis, and sepsis. Normally in some women’s vaginal flora, spreads to infants during childbirth. Causes pyogenic infections, especially in premies and babies with low IgG.
Group B streptococci
Intestinal nematodes that infect the small bowel, lacerating it and causing heavy blood loss and anemia. Penetrate skin, go into veins to lungs, burst through alveoli, migrate up trachea to glottis and are swallowed to get to the bowel. Most important cause of chronic anemia worldwide.
Hookworm (necator americanus and ancylostoma duodenale)
RNA, A is the most common type, strains IDed by hemagglutin and neuraminidase types. Spread by respiratory droplets and secretions. Presents with fever, chills, myalgia, headaches, weakness, nonproductive cough. URI and LRI. Predispose to bacterial pneumonia.
Influenza
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. Spread through mononuclear phagocytes
Leishmaniasis
Intestinal nematode, most common in young children. Deposits eggs in perianal skin, which can be transmitted person to person. Causes perineal itching.
Pinworm (enterobius vermicularis)