Infectious Diseases
Terms
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- Escherichia
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Enterobacteriaceae. Gram- rod. Glucose fermenting, oxidase negative, nitrate reducing.
E.coli - most common cause of UTI, commensal of human bowel. Some strains cause diarrhoea. - Shigella
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Enterobacteriaceae. Gram- rod. Glucose fermenting, oxidase negative, nitrate reducing.
S. dysenteriae, S. flexneri - Bacterial dysentry. - Salmonella
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Enterobacteriaceae. Gram- rod. Glucose fermenting, oxidase negative, nitrate reducing.
S. choleraesuis only species. Many serotype names.
S. typhi, S. paratyphi, Non-typhoidal serotypes cause diarrhoea. - Citrobacter
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Enterobacteriaceae. Gram- rod. Glucose fermenting, oxidase negative, nitrate reducing.
C. freundii, C. diversus - nosocomial UTIs, pneumonia. - Klebsiella
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Enterobacteriaceae. Gram- rod. Glucose fermenting, oxidase negative, nitrate reducing. Resistant to multiple antibiotics.
K. pneumoniae - necrotising pneumonia.
K. rhinoscleromatis - Granulomatous infection upper airways, rare.
K. oxytoca, K. ozaenae - nosocomial UTI, RTI etc. - Enterobacter
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Enterobacteriaceae. Gram- rod. Glucose fermenting, oxidase negative, nitrate reducing.
E. aerogenes, E. cloacae - Nosocomial UTI, RTI. - Serratia
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SEnterobacteriaceae. Gram- rod. Glucose fermenting, oxidase negative, nitrate reducing.
S. marcescens, S. liquefaciens - Nosocomial UTI, RTI. - Proteus
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Enterobacteriaceae. Gram- rod. Glucose fermenting, oxidase negative, nitrate reducing.
P. miribilis - 2nd commonest cause UTI. Nosocomial pneumonia.
P. vulgaris - Nosocomial infections. - Morganella
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Enterobacteriaceae. Gram- rod. Glucose fermenting, oxidase negative, nitrate reducing.
M. morganii - UTI, various nosocomial. - Providencia
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Enterobacteriaceae. Gram- rod. Glucose fermenting, oxidase negative, nitrate reducing.
P. stuuartii - Nosocomial infections, UTI. - Yersinia
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Enterobacteriaceae. Gram- rod. Glucose fermenting, oxidase negative, nitrate reducing.
Y. pestis - Plague.
Y. enterocolitica - Abdominal pain/diarrhoea. Contaminated food. - Pseudomonas
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Gram- rod. Non-fermenting.
P. aeruginosa - UTI, otitis externa, skin ulcers/burns, LRTI. Resistant to most antibiotics. - Stenotrophomonas
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Gram- rod. Non-fermenting.
P. maltophilia - LRTI (cystic fibrosis associated), Septicaemia (cancer immunosuppresion associated) - Burkholderia
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Gram- rod. Non-fermenting.
B. pseudomallei - Meliodosis causing pneumonia, soft tissue abscess, septicaemia. Resistant to antibiotics. - Acinetobacter
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Gram- rod. Non-fermenting.
A. baumannii - Nosocomials, community pneumonia.
A. lwoffi - Nosocomials. - Haemophilus
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Gram- rod. Non-fermenting. Small.
H. influenzae - Encapsulated strains a-g. Type b most important - meningitis, septicaemia in infants. Epiglottis inflammation in young. Acute pharyngitis. Non-encapsulated influenzae cause bronchitis, sinusitis. Requires chocolate agar to grow. Commensal.
H. aphrophilus - endocarditis, part of HACEK. - Legionella
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Gram- rod. Non-fermenting. Aquatic environments. Very fastidious, require BCYEa culture.
L. pneumophila - Legionnares. Aerosol spread.
L. longbeachae - Pneumonia. Common in potting mix. - Vibrio
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Gram- comma shaped. Oxidase positive fermenter. Associated with aquatic environment.
V. cholerae - Severe diarrhoea. Type-01 strain responsible for most pandemics.
V. vulnificus - Septicaemia (immunocompromise), cellulitis. - Aeromonas
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Gram- rod, curved. Oxidase positive fermenter. Aquatic environments.
A. hydrophila - Skin infections. - Camylobacter
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Gram- rod.
C. jejuni - Commensal of animals. Diarrhoea, abdominal cramping, fever.
C. coli - Gastroenteritis. - Helicobacter
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Gram- rod.
H. pylori - Gastric and duodenal ulcers. Associated with adenocarcinoma. - HACEK
- Slow growing fastidious bacteria associated with subacute infective endocarditis. Cause of 'culture negative' (streptococcus negative) endocarditis. Haemophilus aphrophilus, Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, Kingella kingae.
- Pasteurella
- Gram- rod. Animal bite wounds. Skin infections extending to tendon sheathes, joint cavities and bone.
- Bordetella
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Gram- rod.
B. pertussis - Whooping cough. Respiratory droplet spread, highly infectious. Always pathogenic (?). - Brucella
- Gram- coccobacilli. Zoonotic infections. Brucellosis - lymphatic disease with suppurative lesions, febrile symptoms.
- Bartonella
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Gram- rod.
B. henselae - Cat scratch disease. Lymphadenopathy, angiomatosis (aids associated), peliosis (vascular lesions in viscera).
B. quintana - Trench fever. - Neisseria
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Gram- coccus. Diplococcus. N. meningitidis - Serogroups A,B,C&Y cause purulent meningitis, overwhelming septicaemia. Nasopharynx commensal in 10%.
N. gonorrhoeae - Urethritis, cervicitis, pharyngitis.
A number of other Neisseria species are commensals. - Moraxella
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Gram- coccus.
M. catarrhalis - Commensal URT, female genital tract. Otitis media, LRTI. - Staphylococcus
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Gram+ coccus. Catalase positive.
S. aureus - Coagulate positive. Commensal in ~30% nares. Can cause various pyogenic infections - skin lesions, mastitis, bacteraemia/septicaemia. Most common cause of bone, joint and bursae infection. S. Scalded Skin Syndrome (SSSS). STSS.
S. epidermidis - Low virulence, some nosocomial infections and prosthetic joint infections (biofilm).
S. saprophyticus - UTIs. - Streptococcus pyogenes
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Gram+ coccus. Catalase negative.
beta-haemolytic - Complete haemolysis. S. pyogenes (lancefield A) commensal of oropharynx. Pharyngitis, cellulitis, necrotising fasciitis, puerperal sepsis. Rhematic fever, glomerulonephritis, toxic shock like syndrome. - Non-pyogenes Streptococcus
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Gram+ coccus.
S. agalactiae - Lancefield B beta haemolytic. Vaginal coloniser, severe disease in neonates.
Lancefield C-G - Various suppurative infections, animal associated.
alpha haemolytic/viridans strep - S. sanguis, oralis, mitis, mutans - Commensal oropharynx. Endocarditis, dental caries (mutans), abscesses.
S. pneumoniae - Commensal URT 10%. Commonest community pneumonia, commonest meningitis in adults. - Enterococcus
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Gram+ coccus. Commensal human bowel, agglutinate with Lancefield D antiserum.
E. faecalis - Abdominal infections from faecal leakage. UTI, soft tissue infections, bacteraemia, endocarditis.
E. faecium - Similar to faecalis, more resistant to antibiotics. - Bacillus
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Endospore forming gram+ rod.
B. cereus - Food poisoning, enterotoxin.
B. antracis - Resides in soil as spore for decades. Inhalational form: Ingested by alveolar macrophages, haemorrhagic necrosis of lymph nodes. Incubation period ~7 up to 60d. Biphasic: flu like symptoms, resolution, then abrupt fever, hypoxia, septicaemia and meningitis.
GIT form - Meat. lymphadenitis, abdominal pain. ~100% mortality.
Cutaneous form - 20% mortality untreated. Bite-like papule forms to be replaced by black scar with oedema. Penicillin, ciprofloxacin. - Lacrobacillus
- Gram+ rod. GIT and vagina commensal. Facultative anaerobe. Rarely pathogenic.
- Listeria
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Gram+ rod. Facultative anaerobe.
L. monocytogenes - Found in animals, water, soil, produce. Bacteraemia, septicaemia, meningitis. - Erysipelothrix
- Gram+ rod. Facultative anaerobe. Skin infection, rarely septicaemia and endocarditis.
- Corynebacterium
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Gram+ rod. Facultative anaerobe.
C. diptheriae - Diptheria: pharyngitis, airway infection leading to asphyxiation (30% mortality), some strains make exotoxin causing myocarditis and neuritis.
C. jeikeium - Skin commensal, cannula infection, septicaemia.
C. urealyticum - Urea splitting UTI. Produces ammonium crystals causing cystitis. - Nocardia
- Gram+ rod. Opportunistic infections, pneumonitis, haematogenous dissemination from lungs.
- Clostridium
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Gram+ rod. Endospore forming Anaerobe.
C. perfringens - In soil. Clostridial myonecrosis (gas gangrene), food poisoning, necrotising bowel disease.
C. tetani - Soil. Neurotoxin blocks inhibitory signals to motor neurons causing tetanus.
C. botulinum - Soil and food. Neurotoxin causes cranial and muscular neuropathies.
C. difficile - In nature, common in infants, faeces of hospitalised. Causes antibiotic associated diarrhoea, pseudomembranous colitis. - Chlamydia
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Obligate intracellular parasites. Two forms, Elementary body extracellular sporelike form, reticulate body intracellular form. No peptidoglycan cell wall. Not cultured on agar media.
C. trachomatis - Lymphogranuloma venerum biovar and trachoma biovar (ocular trachoma and genital disease) - Chlamydophila
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C. pneumoniae
C. psittaci - Pneumonia, typhoidal fever, flu like symptoms. Parrot associated. - Mycoplasma
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Very small, lack cell wall, fastidious.
M. pneumoniae - atypical pneumonia (patchy consolidation, not routinely cultured, no penicillin response).
M. hominis - Commensal vagine 10%. Vaginosis (with other bacteria), pelvic inflammatory disease.
M. genitalium - non-genococcal urethritis. - Ureaplasma
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Molluscite, similar to mycoplasma.
U. urealyticum - NGU - Mycobacterium
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Very slow growers. Contain mycolic acid, resistant to drying. Detected with ZN stain.
M. tuberculosis - Inhalation, lymph spread. Infection usually asymptomatic but latent.
M. leprae - Inhalational or contact. Strong CMI result in tuberculoid leprosy. Weak CMI lepromatous leprosy.
M. avium-intracellulare - Lung disease and lymphadenitis in immunocompromised. - Treponema
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Spirochate.
T. pallidum - Syphilis: Latent , Primary (chancre), secondary (rash, warts, meningitis), tertiary (cario, neuro symptoms). - Borrelia
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Spirochate.
B. recurrentis - Lice spread. Fever, rigors, jaundice, hepatosplenomegaly.
B. burgdorferi - Lyme disease. - Leptospira
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Spirochate.
L. interrogans - Animal urine. Leptospirosis causing septicaemic phase and immune phase (low grade fever, headache, rash). - Spirillum
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Spirochate.
S. minor - rat bite fever. - Penicillin
- Betalactam. Streptococcus, cellulitis (S. pyogenes), endocarditis, meningitis (N. meningitidis, S. pneumoniae)
- Flucloxacillin, Dicloxacillin
- Penicillinase resistant. Oral, IV. S. aureus (cellulitis, osteomyelitis, arthritis)
- Amoxycillin, Ampicillin
- Oral, IV. S. pneumoniae, L. monocytogenes. UTIs.
- Augmentin
- Amoxycillin+clav. Chest infections, UTI, diabetic foot infections.
- Ticarcillin
- P. aeruginosa (or piperacillin).
- Timentin
- Ticarcillin+clav. Pneumonia (particularly where gram negatives), peritonitis, diabetic foot infections.
- Piperacillin
- P. aeruginosa (or ticarcillin).
- Tazocin
- Pizarcillin + tazobactam. Pneumonia is severely ill patients.
- Cephalexin, Cephalothin
- 1st generation cephalosporin. S. aureus (penicillin allergy). Some GNB UTI.
- Cefaclor, Cephamandole, Cefuroxime, Cefuroxime axetil.
- 2nd generation cephalosporin. RTI, otitis media, sinusitis. Mainly cefaclor.
- Cefotaxime, Ceftriaxone
- Third generation cephalosporin. Gram negative infections. Bacterial meningitis. Serious pneumonia. ESCAPPM are resistant.
- Cefrazidime
- Third generation cephalosporin. ESCAPPM are resistant. Serious P. aeruginosa.
- Cefepime, Cefpirome
- Fourth generation cephalosporin. Hospital use, empirical for serious infection. Very broad spectrum.
- Imipenem, Meropenem, Ertapenem
- Carbapenem (beta lactam). Broadest spectum antibiotic, expensive. Last resort in seriously infected patients.
- Aztreonam
- Monobactam (beta lactam). Gram negative bacteria.
- Erythromycin
- Macrolide (inhibit protein synthesis). Skin infections (strep), whooping cough (B. pertussis), Diarrhoea (campylobacter), atypical pneumonia (mycoplasma).
- Roxithromycin, Azithromycin, Clarithromycin
- Macrolide (inhibit protein synthesis). Chlamydia (azithromycin). RTI.
- Clindamycin
- Lincosamide (block protein synthesis). Aspiration pneumonia, foot infection, GPB skin infection, gas gangrene (C. perfringens), acne.
- Tetracycline, Doxycycline
- Tetracycline (inhibit protein synthesis at 30s and block RNA binding). Broad spectrum, RTI, chlamydia, acne, typhus, malaria prophylaxis.
- Sulfamethoxazole
- Sulfonamide (Blocks DNA production). Part of cotrimoxazole.
- Cotrimoxazole
- Sulfamethoxazone (block DNA synthesis) and Trimethoprim (same). RTI, UTI, Salmonella, Shigella, Nocardiosis.
- Ciprofloxacin, Norfloxacin
- Quinolone (interfere with DNA gyrase). Gram negative (UTI, pneumonia) where cephalosporins or gentamicin can't be used, or caused by ESCAPPM. P. aeruginosa. Prostatitis. Gonorrhoea.
- Gentamicin
- Aminoglycoside (protein synthesis inhibition 30s and 50s). Used with ciprofloxacin for serious GNB such as ESCAPPM or aeruginosa.
- Rifampicin
- Rifamycin (block RNA polymerase). Antituberculosis. Bone or joint infections (S. epidermidis).
- Vancomycin, Teicoplanin
- Glycopeptide (Block cell wall, RNA synthesis, membrane permeability alteration). MRSA, S. epidermidis, Enterococci.
- Mentronidazole, Tinidazole
- Nitromidazole (free radical production inside bacteria). Protozoal infections or bacterial vaginosis.
- Synercid
- Streptogramin (quinupristin+dalfopristin)(protein synthesis inhibition). VRE or MRSA.
- Linezolid
- Oxazolidinone (block protein synthesis early stage). MRSA, VRE, Penicillin resistant S. pneumoniae.
- Giardia lamblia
- Protozoan Flagellate. Two forms, trophozoite (feeding form) and cyst (external). Attaches to duodenal lining. Diarrhoea, nausea. Stool or aspirate diagnosis. Treatment metronidazole.
- Entamoeba histolytica
- Protozoa. Trophozoite (feeding) and cyst (external) form. Feeds on mucosa of large intestine, causing ulcers, dysentry. Can become invasive. Diagnosis stools, sigmoidoscopy, serological. Treatment metronidazole.
- Cryptosporidium parvum
- Protozoa. Zoonotic infection occupying bowel crypts. Diarrhoea, nausea. Self-limiting.
- Balantidium coli
- Protozoan ciliate, pig associated.
- Ascaris lumbricoides
- Nematode (roundworm). 15-30cm worm living in small intestine. 200,000 eggs per day, passed into faeces and mature in soil. Infection orally, duodenul>lung> trachea>intestine. Pneumonitis, fever, abdominal symptoms, colicky pain. Diagnosis stool. Treatment mebendazole.
- Enterobius vermicularis
- Nematode (roundworm). Pinworm. 5-13mm worm, inhibit caecum and appendix. Females detach and lay eggs perianal region at night. Oral>intestine infection. Minor intestinal symptoms, haemorrhage, occasionally appendicitis. Treatment combantrin.
- Trichuris Trichiura
- Nematode (roundworm). Whipworm. 3-5cm worms attaching to caecum. Oral>intestine, 5k eggs into stool/day. Usually asymptomatic, appendicitis, colitis, anaemia. Diagnosis stool, treatment mebendazole.
- Hookworms
- Ancylostome duodenale and Necator americanus. 10mm worm living in small intestine. Oral>intestine >lung>intestine migration. Allergic reactions, pneumonitis, anaemia. Treatment mebendazole.
- Strongyloides stercoralis
- Nematode (roundworm). Free-living 1mm form in soil. Can transition to filariform larvae, surviving until infection through human skin. Carried to lungs, travel to intestine. Can auto-infect. Dermatitis, pneumonitis, allergy, abdominal pain, diarrhoea. Treatment Thiabendazole.
- Dracunculus medinensis
- Nematode. Guinea worm. up to 70cm worm living under skin. Lives in water.
- Trichinella spiralis
- 1-3mm zoonotic worm in ileum. Larvae enter blood and encyst in skeletal muscle. Trichinosis. Fever, muscle tenderness, diarrhoea. Biopsy biceps of gastrocnemius diagnosis. Treatment steroids, thiabendazole.
- Echinococcus granulosus
- Cestode (tapeworm). 3-6mm worm living in small intestine. Larvae ingested orally and penetrate to liver and lungs. Forms cysts (hydatid disease). Treatment mebendazole, surgery to remove cysts.
- Taenia saginata
- Cestode (tapeworm). In small intestine, up to 5m formed from thousands of proglottids. Each produce eggs. Migrate duodenum>muscles in animals. Niclosamide treatment.
- Taenia solium
- Pork cestode (tapeworm). Human can be intermediate carrier, giving rise to systemic symptoms (muscle, CNS). Stool or radiology diagnosis (cysts calcified). Treatment niclosamide.
- Hymenolepsis nana
- Dwarf cestode (tapeworm). Common in Au. 2-4cm worm in inttestine. Treatment praziquantel.
- Diphyllobothrium layum
- Fish cestode (tapeworm). up to 10m, causing megaloblastic anaemia. Treatment niclosamide.
- Opisthorchis sinensis
- Trematode (fluke. Worm living in biliary passages. Diarrhoea, jaundice. Praziquantel.
- Trypansoma brucei gamviense. T. b. rhodesiense.
- Blood protozoa. Fly vectors. Enter CNS, leading to death and coma. Treatment Suramin (arsenic derivative).
- Trypansoma cruzi
- Blood protozoan. Infest cardiac tissue. Suddent cardiac failure, gut dilatations. Treatment nifurtamox.
- Lesimania donovani, braziliense, tropica
- Blood protozoan. Sandfly vectors. Kala Azar disease (donovani) invades liver and spleen, causing fever, anaemia and death in months-years. Mucocutaneous (braziliense) infection causes disfigurement. Treatment stibogluconate.
- Toxoplasma gondii
- Sporozoan blood parasite. 2 stages. Sexual phase in intestinal cells of felines. Asexual phase in humands, usually asymptomatic. Infection in pregnancy causes teratogenic CNS effects. Treatment pyrimethamine.
- Pneumocystis carinii
- Blood ?protozoan. Interstitial cell pneumonia, AIDS related. Treatment trimethoprim.
- Trichomonas vaginalis
- Protozoan, associated with sexual activity and STDs. Asymptomatic in men. Vulvo-vaginitis, discharge. 5-nitroimidazole treatment.
- Wuchereria bancrofti & Brugia malayi
- Mosquito vectors. Blood nematode (roundworm). Larvae migrate to lymph and multiply. Often asymptomatic, lymphadenitis, lymphangitis, rarely elephantiasis. Treatment Ethylcarbamazine.
- Schistosomes
- Blood flukes. Zoonotic, penetrate human skin (from water). Fibrosis caused by eggs failing to hatch into blood, diarrhoea, cystitis, hepatomegaly, renal failure. Praziquantel.
- Piedra
- Fungal hair shaft infection. Trichosporon beigelii (white) and Piedraia hortae (black)
- Tinea nigra
- Skin infection, exophiala werneckii.
- Pityriasis versicolor.
- Superficial infection, Malassezia furfur. Pink/coppery appearance in pale skin, lighter appearance on tanner skin.
- Dermatophytosis
- Trichophyton, Microsporum, Epidermophytom. May also cause onychomycosis or tinea unguium.
- Candidiasis
- Mainly yeast form fungus. Ubiquitous opportunistic fungus. Skin rahses, balantitis, oral plaques, vaginal inflammation (usually commensal), GIT, candidaemia.
- Sporotrichosis
- Sporothrix shenckii. Nodular skin lesions breaking down to chronic ulcer. Lymphatic spead may cause suppurative abscesses.
- Aspergillosis
- Many are ubiquitous. Pulmonary (asthma, alveolitis), aspergilloma (fungus ball), disseminated (immunocompromise).
- Hyalohyphomycosis.
- Hyaline hyphomycetes causing infections in immunocompromised.
- Zygomycosis.
- Ubiquitous, sinusitis, pulmonary, disseminated symptoms in immunocompromised.
- Cryptococcosis
- Cryptococcus neoformans. Pathogenic fungus inhaled and causing respiratory and CNS symptoms. Common in immunocompromised, but many normal infections also.
- Blastomycosis
- Dimorphic fungi causing pulmonary disease.
- Azoles.
- Antifungal inhibiting conversion of lanosterol to ergosterol. Clotrimazole (candida), ketoconazole (broad), fluconazole (triazole, broad), itraconazole (triazole, broad including aspergillus).
- Polyenes
- Antifungal distrupting plasma membrane. Nystatin (mucosal candidiasis), amphotericin B (very broad spectrum, highly nephrotoxic).
- Allylamines
- Antifungal inhibiting squalene>lanosterol conversion. Terbinafine (dermatophyte onychomycosis where topical treatment failed).
- Glucan synthesis inhibitors
- Caspofungin.