Summary of Clinical Pathogens (homemade/DRAFT) - University of ...

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Summary of Clinical Pathogens (homemade/DRAFT) - University of ...

  1. 1. Aerobes<br /><ul><li>PathogenSite of Infection/ Clinical DiseaseNotes:StaphylococcusMorphology: Cocci in Cluster | Gram: (+)Staphylococcus aureusCoagulase: (+)Hemolytic: BetaSkin:Folliculitis, boils, abscessesImpetigo – usually on face. Yellow crusty presentationCellulitis (require aggressive treatment)Scalded skin syndrome – neonate only. High recovery rate if treatedGI: Food poisoning if left out for too long. Onset in 4-6hrs. Resolves within 24 hrs.Systemic:EndocarditisOsteomyelitisSepticaemia (can be due to wound infection)Found commonly on skin, mucous membranes, and environmentOften carried in nasal naresResistance strains (e.g. MRSA, VRSA) have different virulence when compared between institutional acquired and community acquiredMay cause tunnelling infection on catheters Staphylococcus epidermidisCoagulase: (-)Hemolytic: alpha or gammaSkin:Stitches abscesses and wounds. May cause septicaemia and endocarditisMedical equipmentForms biofilm. May cause tunnelling infection which requires replacement of catheterFound common on skinPredominant staphylococci on skinMay be found in blood culture if skin was not properly cleaned prior to samplingStaphylococcus saprophyticusCoagulase: (-)Genitourinary mucous membrane of healthy, young women (i.e. UTI)Treatment is usually effectiveStreptococciMorphology: Cocci in Chain | Gram: (+)Streptococcus pyogenes (Group A)Hemolytic: betaUbiquitous. Found on throats of asymptomatic carriers. Usually community acquiredURI:Main cause of bacterial tonsillitis (AKA “strep throat”)Viral is the main causes of all tonsillitis Usually self-limiting (within 3 days)May cause rheumatic fever and glomerular nephritis (rare)m which is the reason for antibiotic treatment (caused by M protein)Otitis media (rare)Sinusitis (rare)Skin infectionMain pathogen that causes necrotizing fasciitis Scarlet fever – character fever characterized by sore throat, strawberry color tongue and body rash that excludes the face)CellulitisPyoderma – skin disease that produces pusErysipelas – usually presented on the face, characterized by inflammation of the dermis. Requires immediate treatmentExpressing variety of M Proteins, which are virulence factors that inhibit opsonisation by complementsThe variety of M proteins makes reinfection commonFully sensitive to penicillin (i.e. no resistance)Pharyngitis with pus would likely indicate a “strep throat”. However, treatment should not proceed unless culture is positive for S. pyogenesStreptococcus agalactiae (Group B)Hemolytic: betaAsymptomatic carriers. Located in the gut, vagina and cervix of healthy young womenCarried intermittently MotherPostpartum sepsisNeonate: Neonatal pneumoniaNeonatal sepsisNeonatal meningitisFully sensitive to penicillin (i.e. no resistance)Fast (<24hrs) and High mortality in neonatesProphylaxis treatment of mother is not recommended, unless membrane have rupture for >24hrsStreptococcus pneumoniae (AKA diplococcus, pneumococcus)Hemolytic: alphaPart of the normal flora of the upper respiratory tractMajor cause of otitis media and sinusitis Main cause of bacterial pneumonia Major cause of meningitis in young peopleThis species contain many capsular subtypesVaccination available. Polyvaccines are developed to combat the different subtypesCan easily cross the BBBViridan group of StreptococcusHemolytic: alphaUbiquitous. Normal flora of the mouth and respiratory tract. May causes dental carriesMay cause endocarditis for people with abnormal heart valves. Results in vegetation of the endocardiumNormally, this group does NOT cause diseaseHowever, for patient with abnormal heart valve who are undergoing surgery, antibiotic prophylaxis is recommendedEnterococcusE. faecalisE. faecium (formerly Group D strep)Normal flora of the intestine. May be found in the genitalia (rare)May cause intra-abdominal infection and sepsis from post surgical wound near the GIMay cause endocarditis post-surgically Rarely causes UTIHigh antibiotic resistance; certain strains may be resistant to vancomycinMorphology: Bacilli | Gram: (+)Listeria monocytogenes (Corynebacteraciae family)Ubiquitous in natureFound on gut and nasopharynxCauses diarrhea, influenza-like symptoms, upper respiratory tract infection In immunocompromised patients, may cause septicaemia, endocarditis and meningitis Uncooked foodUsually only cause disease in babies or immunocompromised patients Intracellular infectionBacillus Anthracis (Anthrax)Spores in soilInfected animals (infect cattle, goat, sheep)Infected meat Eating infected meat cause gastrointestinal anthrax. This is associated with higher rates of systemic infection compared to cutaneous anthraxSpores of animal hides May cause inhalation anthrax (high mortality) May cause cutaneous anthrax, which has low mortality. There is a characteristic black-scar lesionThe site of infection and the clinical presentation depends on site of entryIn bioterrorism, milled spores of anthrax can penetrate the lungs (inhalation anthrax). These spores are uptaken to the mediastinal node. The release of toxin is the cause of mortality; it does NOT cause pneumoniaNeisseriaMorphology: Cocci | Gram: (-)Neisseria gonorrhoeae (Gonococcus)Infected individuals. May infectGenital tractIn male, it causes painful urethritis, which can lead to infertilityIn female, it can cause cervicitis, leading to salpingitis, finally leading to pelvic inflammatory disease and infertilityMay infect neonate if baby was born thru infected genital tract. This causes ophthalmia (inflammation of the eye). Treat prophylactically Rectum/anus (from anal sex)Nasopharynx (from oral sex)May cause septic arthritis at a single jointIt DOES NOT live very well on inanimate objectsIntracellular infectionNeisseria meningitides (Meningococcus)Nasopharynx of infected patient or asymptomatic carrierSpread via droplets form the nasopharynxClinically, can cause:MeningitisMeningoccemia (Meningococcal septicaemia) – sepsis accompanied by breakdown of blood vessel wall, leading to widespread petechial lesion (which are coagulation of blood on skin)Vaccine has been developed for this pathogenIntracellular infectionMeningoccemia may require amputation in severely affected organs Moraxella catarrhalis (formerly Neisseria catarrhalis, Branhamella catarrhalis)Upper Respiratory TractDeveloped as pneumonia in immunocompromised patients, COPD and hospitalized patientsMay cause laryngitis and tracheitis Can occasionally cause otitis media and sinusitisMorphology: coccobacilli | Gram: (-)Hemophilus influenzaeNormal flora of the upper respiratory tract, esp. the mucous membraneDevelop as pneumonia and bronchitis in immunocompromised and COPD patientsEpiglottitis may also developed, which may cause rapid obstruction of airway. Drooling is the hallmark of airway obstructionMay cause otitis media and sinusitis (in children)Vaccination now available for children Prior to this, H. influenzae was the most common cause of meningitis and epiglottitis in childrenLegionella pneumophilaUbiquitous. Usually found in greater amounts in humid areasIntracellular infectionMorphology: bacilli | Gram: (-)Bordetella pertussisInfected humanAirborne spreadcauses Whooping cough (AKA Pertussis)Can be fatal in infant due to the toxin produced. It secretes an exotoxin (pertussis toxin)Vaccination available for children for >2monthsthis is an acellular vaccine that does not cause seizure as compared to older vaccineEnterobacteriaceae (order)Morphology: bacilli | Gram: (-)Escherichia coliNormal flora of the intestine, infected foodMost frequent cause of UTIIn immunocompromised patient and neonates, can cause pneumonia and meningitismeningitis in neonates is caused by strain that produce K1 capsular antigenOne cause of traveller’s diarrhea (by ETEC – enterotoxigenic E. coli)Several strains may cause Hemolytic uremic syndrome, characterized by hemolysis, thrombocytopenia, and transient renal failureE. coli are have pili that allows it to attach to GI wallsperitonitis is only usually seen in GI rupture or GI surgerySurgical wounds may also be infected by E. coliMany strain produce A/B toxinsKlebsiella pneumoniaeNormal flora of the nose, mouth and intestinePathogenesis usually occurs in immunocompromised patients may cause Klebsiella pneumoniamay infect wounds and cause bacteremiaA common cause of UTI in elderly Produce wide spectrum beta lactamaseProteus mirabilisIndole: (-)Found in water and soilColonizes the GI tractPathogenesis usually occurs in immunocompromised patientsPneumonia, septicaemiaWould infectionsA common cause of UTI in elderly, esp. t hose with urinary cathetersWhen plating, produces distinct colony that is described as “swarming proteus colony” – where single colony looks like bull’s eye with rings of alternating colony followed clearingProteus VulgarisIndole: (+)Colonizes the GIPathogenesis usually occurs in immunocompromised patientsUTI and bacteremiaSerratia marscesensColonizes respiratory and urinary tract in immunocompromised patients (usually hospital patients)Opportunistic infection in the lower respiratory tract, urinary tract and surgical woundsOpportunistic infection Enterobacter cloacaeColonizes the GIOpportunistic infection in burns and wounds, respiratory tract, urinary tractsOpportunistic infectionSalmonella – S. typhi, S. enteritidisS. typhimuriumUbiquitous in nature. GI tracts of mammals, reptiles, birds and insectsAsymptomatic carriers (in gallbladder)Usually infection (in North America) is gastroenteritis – which is caused by S. enteritidis and S. typhimurium.Self-limiting. Do not require treatmentS. typhi may cause typhoid fever, which is characterized by GI perforation by bacteria, resulting in sepsis and delirium (typhoid state), which has high mortality if untreatedMay cause bloody diarrhea S. typhi is the only strain that is exclusively carried by humans ONLYTransmitted by fecal-oral route, contaminated waterShingella – S. boydii, S. flexneri, S. sonnei, S. dysenteriaeCan cause traveller’s diarrheaNOT normally found in the GI tractDiarrhea highly infectious Cause of diarrhea is due to shinga toxinTransmitted by contaminated water and from person to personTransmitted by fecal-oral route, contaminated waterInfection usually acquired in third world countries Requires very low bacteria count (i.e. 1 to 10 units) for parthenogenesis Intracellular infectionProduces A/B toxins (Shinga toxin), much like O157:H7 E. coli (which causes hamburger disease)PseudomonasMorphology: bacilli | Gram: (-)Pseudomonas aeruginosaFound on moist area, including soil, water, animals, and body parts (perineum, axilla, ear)Usually infected immunocompromised patients. Usually found in intensive care unitsMajor pathogen of nosocomial (i.e. hospital acquired) pneumonia, and UTIMajor cause of surgical infection Major cause of gram (-) infectionMajor cause of pneumonia in cystic fibrosis patients May cause dermatitis and otitis externa in healthy individuals in infected bath tubsCell culture has distinct mucoid appearance, due to the production of polysaccharide capsuleEncapsulated bacteriaInherent multidrug resistance</li></ul>Anaerobes<br />Note: that these anaerobes have distinct, unpleasant smell. This is due to the production of gases during its metabolism<br />Note: cultures must be collected in anaerobic conditions!<br /><ul><li>PathogenSite of Infection/ Clinical DiseaseNotes:Gram: (-)Bacteroides fragilisFlora of the intestine and vagina. Most abundant colonizerCommon cause of GI abscesses.May be found in diabetic ulcersMay be found in intra-abdominal and pelvic infections May cause of gram (-) bacteremiaPorphyromonas spp. (formerly Bacteroides)Flora of the oropharynx, GI and GU tract Odontogenic infection (teeth infection)Periodontal infection (infection of tissues surrounding teeth)may also cause infection in GI abscesses Prevotella spp. (formerly Bacteroides)Flora of the oropharynx, GI and GU tractusually causes head and neck infection as a results of abscess from odontogenic infectionsmay cause anaerobic pleuropulmonary infection(infection of the lungs and plura)Gram: (+)Clostridium(genus)Found in soil, human and animals intestineC. perfringens – causes gas gangrene (muscle gangrene with gas production in infected area) C. tetani – causes tetanusC. difficile - causes pseudomembranous colitis (has a distinct horse feces smell)This genus contain strains that produce variety of toxins, including neurotoxins, enteric toxins, etc. EIA can be used to detect the A/B toxin produced by C. difficileSpiral and Curved BacteriaGram stain no possible because bacterium is too smallTreponema pallidumSpread person to person. Causes syphilis in humans, which undergoes THREE stagesPrimary syphilis – painless lesion Secondary syphilis – patient experience flu like symptoms. Hallmark of this stage is rash on palms of hands and soles of feet Tertiary syphilis – (requires years) neurosyphilis in the CNS, resulting in mental retardation and motor skill weakness. This is usually accompanied by a skin infectionMay cause congenital syphilis if mother is infected when carrying childCongenital syphilis results in long lasting physical deformities and CNS effectscongenital syphilis is often due to secondary syphilius of the motherBorrelia burgdorferiDeer ticks (lxodes) are the carrier of this disease. Causes lyme disease in human (in North American)Initial bite results in a distinct skin infection known as erythema chronicum migrans, which has a distinct appearance of rings of alternating erythema and clear skin, much like a bull's eye Usually self-limiting and may resolve with or without flu like symptomsIn some individual, if untreated, may result in neurological symptoms including neuropathic pain, concentration and attention impairment, and physical coordination problemsFor those who are hiking, it is recommended to wear long pants and sleeve, with socks over pants. Also, use DEET, and check for signs of ticks attachment after going indoorsMorphology: Spiral and Curved | Gram: (-)Helicobacter pylori (formerly Campylobacter pylori)Found in human GIMay cause duodenal and gastric ulcersEsophagitis and gastritis Chronic infection may result in gastric adenocarcinoma Asymptomatic carrierCampylobacter jejeuniInfected animals and infected food sourcesCommon cause of bacterial diarrheaNote: most gastroenteritis is caused by viral meansVibro choleraInfected water Occurs more frequently in third would cultures where flooding occursCholera toxins produces severe watery diarrhea and dehydrationAsymptomatic carrierRehydration is the primary treatmentMycoplasmaMorphology: No peptidoglycan cell wall.Mycoplasma pneumoniaSpread person to personCauses atypical pneumonia in healthy, young individualsThere is usually no SOB, no/low fever, some headacheUsually self-limiting, but may persist of r along timeCell culture have characteristic of “fried egg” shapeMycoplasma hominisSpread person to person. May be found in GU tractCauses STDOpportunistic infectionCell culture have characteristic of “fried egg” shapeUreaplasma urealyticumFlora of the GU tractCauses post-partum fever in womenOpportunistic infection Cell culture have characteristic of “fried egg” shapeChlamydiaeGram: (-).Chlamydia trachomatisSpread person to person.Causes STDResults in urethritis and pelvic inflammatory disease which can lead to infertility May result in neonatal trachoma if baby is born thru infected cervixObligate intracellular parasites – Cannot reproduce outside of host’s cells#1 cause of blindness in the world due to neonatal trachomaCommon in third world countriesChlamydia pneumophilaSpread person to personNOT an STDUsually present as atypical pneumonia in young, healthy individualsObligate intracellular parasites – Cannot reproduce outside of host’s cellsMycobacteriumMorphology: contains mycolic acid cell wallMycobacterium tuberculosis(TB)Spread person to person, infected animals Spread from dropletsCauses tuberculosisPulmonary lesions causes formation of cavities in the lungs as granulomasAs it spreads, it takes on distinct droplet like lesions on organs. This stage is known as miliary TBDue to the fact that it is highly continuous, requires isolationGranulomas usually contain a large amount of TB cells. The large concentration of cells allows selection of antibiotic resistant strain when only one antibiotic is used. Mycobacterium avium Spread person to personUsually infected immunocompromised patientsm esp. HIV and transplant patientsResults in diarrhea and pneumoniaUsually does NOT infected healthy indivdiualsMycobacterium lepraeSpread person to personCauses leprosy - development of granuloma tissues in the peripheral, causing damage to peripheral nerves, skin lesion and damage to the mucosa of the upper respiratory tract Requires isolation of infected individuals

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