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Infectious Diseases


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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.
Enterobacteriaceae. Gram- rod. Glucose fermenting, oxidase negative, nitrate reducing.
S. dysenteriae, S. flexneri - Bacterial dysentry.
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.
Enterobacteriaceae. Gram- rod. Glucose fermenting, oxidase negative, nitrate reducing.
C. freundii, C. diversus - nosocomial UTIs, pneumonia.
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.
Enterobacteriaceae. Gram- rod. Glucose fermenting, oxidase negative, nitrate reducing.
E. aerogenes, E. cloacae - Nosocomial UTI, RTI.
SEnterobacteriaceae. Gram- rod. Glucose fermenting, oxidase negative, nitrate reducing.
S. marcescens, S. liquefaciens - Nosocomial UTI, RTI.
Enterobacteriaceae. Gram- rod. Glucose fermenting, oxidase negative, nitrate reducing.
P. miribilis - 2nd commonest cause UTI. Nosocomial pneumonia.
P. vulgaris - Nosocomial infections.
Enterobacteriaceae. Gram- rod. Glucose fermenting, oxidase negative, nitrate reducing.
M. morganii - UTI, various nosocomial.
Enterobacteriaceae. Gram- rod. Glucose fermenting, oxidase negative, nitrate reducing.
P. stuuartii - Nosocomial infections, UTI.
Enterobacteriaceae. Gram- rod. Glucose fermenting, oxidase negative, nitrate reducing.
Y. pestis - Plague.
Y. enterocolitica - Abdominal pain/diarrhoea. Contaminated food.
Gram- rod. Non-fermenting.
P. aeruginosa - UTI, otitis externa, skin ulcers/burns, LRTI. Resistant to most antibiotics.
Gram- rod. Non-fermenting.
P. maltophilia - LRTI (cystic fibrosis associated), Septicaemia (cancer immunosuppresion associated)
Gram- rod. Non-fermenting.
B. pseudomallei - Meliodosis causing pneumonia, soft tissue abscess, septicaemia. Resistant to antibiotics.
Gram- rod. Non-fermenting.
A. baumannii - Nosocomials, community pneumonia.
A. lwoffi - Nosocomials.
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.
Gram- rod. Non-fermenting. Aquatic environments. Very fastidious, require BCYEa culture.
L. pneumophila - Legionnares. Aerosol spread.
L. longbeachae - Pneumonia. Common in potting mix.
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.
Gram- rod, curved. Oxidase positive fermenter. Aquatic environments.
A. hydrophila - Skin infections.
Gram- rod.
C. jejuni - Commensal of animals. Diarrhoea, abdominal cramping, fever.
C. coli - Gastroenteritis.
Gram- rod.
H. pylori - Gastric and duodenal ulcers. Associated with adenocarcinoma.
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.
Gram- rod. Animal bite wounds. Skin infections extending to tendon sheathes, joint cavities and bone.
Gram- rod.
B. pertussis - Whooping cough. Respiratory droplet spread, highly infectious. Always pathogenic (?).
Gram- coccobacilli. Zoonotic infections. Brucellosis - lymphatic disease with suppurative lesions, febrile symptoms.
Gram- rod.
B. henselae - Cat scratch disease. Lymphadenopathy, angiomatosis (aids associated), peliosis (vascular lesions in viscera).
B. quintana - Trench fever.
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.
Gram- coccus.
M. catarrhalis - Commensal URT, female genital tract. Otitis media, LRTI.
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
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
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.
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.
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.
Gram+ rod. GIT and vagina commensal. Facultative anaerobe. Rarely pathogenic.
Gram+ rod. Facultative anaerobe.
L. monocytogenes - Found in animals, water, soil, produce. Bacteraemia, septicaemia, meningitis.
Gram+ rod. Facultative anaerobe. Skin infection, rarely septicaemia and endocarditis.
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.
Gram+ rod. Opportunistic infections, pneumonitis, haematogenous dissemination from lungs.
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.
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)
C. pneumoniae
C. psittaci - Pneumonia, typhoidal fever, flu like symptoms. Parrot associated.
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.
Molluscite, similar to mycoplasma.
U. urealyticum - NGU
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.
T. pallidum - Syphilis: Latent , Primary (chancre), secondary (rash, warts, meningitis), tertiary (cario, neuro symptoms).
B. recurrentis - Lice spread. Fever, rigors, jaundice, hepatosplenomegaly.
B. burgdorferi - Lyme disease.
L. interrogans - Animal urine. Leptospirosis causing septicaemic phase and immune phase (low grade fever, headache, rash).
S. minor - rat bite fever.
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.
Amoxycillin+clav. Chest infections, UTI, diabetic foot infections.
P. aeruginosa (or piperacillin).
Ticarcillin+clav. Pneumonia (particularly where gram negatives), peritonitis, diabetic foot infections.
P. aeruginosa (or ticarcillin).
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.
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.
Monobactam (beta lactam). Gram negative bacteria.
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.
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.
Sulfonamide (Blocks DNA production). Part of 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.
Aminoglycoside (protein synthesis inhibition 30s and 50s). Used with ciprofloxacin for serious GNB such as ESCAPPM or aeruginosa.
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.
Streptogramin (quinupristin+dalfopristin)(protein synthesis inhibition). VRE or MRSA.
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.
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.
Blood flukes. Zoonotic, penetrate human skin (from water). Fibrosis caused by eggs failing to hatch into blood, diarrhoea, cystitis, hepatomegaly, renal failure. Praziquantel.
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.
Trichophyton, Microsporum, Epidermophytom. May also cause onychomycosis or tinea unguium.
Mainly yeast form fungus. Ubiquitous opportunistic fungus. Skin rahses, balantitis, oral plaques, vaginal inflammation (usually commensal), GIT, candidaemia.
Sporothrix shenckii. Nodular skin lesions breaking down to chronic ulcer. Lymphatic spead may cause suppurative abscesses.
Many are ubiquitous. Pulmonary (asthma, alveolitis), aspergilloma (fungus ball), disseminated (immunocompromise).
Hyaline hyphomycetes causing infections in immunocompromised.
Ubiquitous, sinusitis, pulmonary, disseminated symptoms in immunocompromised.
Cryptococcus neoformans. Pathogenic fungus inhaled and causing respiratory and CNS symptoms. Common in immunocompromised, but many normal infections also.
Dimorphic fungi causing pulmonary disease.
Antifungal inhibiting conversion of lanosterol to ergosterol. Clotrimazole (candida), ketoconazole (broad), fluconazole (triazole, broad), itraconazole (triazole, broad including aspergillus).
Antifungal distrupting plasma membrane. Nystatin (mucosal candidiasis), amphotericin B (very broad spectrum, highly nephrotoxic).
Antifungal inhibiting squalene>lanosterol conversion. Terbinafine (dermatophyte onychomycosis where topical treatment failed).
Glucan synthesis inhibitors

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