Pathogenic Bacteria Flashcards
Staph aureus? Characteristics?
Gram positive cocci:
- abscess-forming bacteria
- can also cause internal infection at joints, discs, pneumonia and infective endocarditis
- can also live harmoniously
- sticks well to prostheses
Coagulase enzyme +ve:
- converts fibrinogen to fibrin (clotting - camouflage)
- resistant to penicillin due to beta-lactamase presence
Common shapes of bacteria? Description?
Cocci:
+ve; circular with peptidoglycan layer
-ve; circular with lipopolysaccaride layer
Rod:
+ve; long rod-shaped peptidoglycan later
-ve; long rod-shaped lipopolysaccardie layer
Cocci? Gram classifications? Examples?
+ve: strep and staphy
-ve: neisseria meningitidis/gonorrhea and moraxella catarrhalis
Rods? Gram classifications? Examples?
+ve: listeria, clostridium difficile/botulinium/perfringens/tetani and bacillus anthracis
-ve: salmonella, E.coli, campylobacter, shigella, pseudomonas, haemophilus influenza and bacteriodetes
Antibiotics? Ranges? Examples?
Broad spectrum: eliminates all bacteria (good and bad)
Narrow spectrum: eliminates a specific type of bacteria
Gentamycin: -ve rods
Coamoxiclav: +ve cocci and -ve rods
Amoxicillin: +ve cocci
Streptococci? subtypes?
alpha-haemolytica: (turn blood agar green) pneumoniae; causes infective endocarditis
beta-haemolytica: (urn blood agar clear) A-G
Strep throat: can cause rtheumatic/scarlet fever
- abs cross react with the tissue causing problems
Beta-haemolytic streptococci? subtypes, characteristics and examples?
A: pyogenes; sore throat and necrotising fasciitis
B: agalactiae; neonatal sepsis (meningitis), carried in genital tract
D: enterococcus faecalis; non-haemolytic in gut but can cause UTI
Clostridium difficile? Characteristics?
- Present in healthy gut (+ve)
- causes of diarrhoea (toxin production)
- increased risk with antibiotic use (disrupt gut flora)
- detect by ELISA
Clostridium perfringens? Characteristics?
- present in soild and commensal in human gut and faeces
- pathogenic in food casuing food-poisoning (enterotoxin)
- cause gangrene
Clostridium tetani? Characteristics?
- toxins cause tetanus (uncontrolled msucle spams due to loss of inhib at NMJ
- modified toxin used for immunisation
Neisseria meningococcus? Characteristcs?
- causes meningitis (inflammed meninges)
- important when isolated from a sterile site (CSF)
- PCR available
- ve
Neisseria gonorrhoeae/ Characteristics?
- causes urethritis (men) and pelvic inflam (women)
- sexual contact
- ve
Moraxella catarrhalis? Characteristics?
- cause resp tract infect
- especially in underlying lung pathology
- ve
E.coli? Characteristics?
- human and animal reservoirs
- virulence mech via pili, capsule, endo.exotoxins produced
- ferments lactose
- 160 serotypes
- cause UTIs
- Enterotoxogenic: traveller’s diarrhoea
- Enterohaemorrhagic: bloody diarrhoea
Salmonella enterica? Characteristics?
- self limiting enterocolitis with or without diarrhoea
- 2nd most common cause of bacteria diarrhoea
Salmonella typhi? Characteristics?
- causes typhoid fever
- fever and constipation
- vaccine available
Shigella? Characteristics?
- causes diarrhoea and dysentery
- travel related
Campylobacter? Characteristics?
- microaerophilic (low o2)
- source from domesticated animals and chickens
- faecal-oral route
- foul smelling then bloody diarrhoea
Helicobacter pylori? Characteristics?
- normal commensal in human gut
- damages mucosa and causes ulcers
Haemophilus infleunzae? Characteristics?
- cocco-bacilli apperance
- resp tract infection
- capsulate form
Pseudomonas? Characteristics?
- water and soil organisms
- contaminate medical equipment
- hospital acquired causes of sepsis
- resp infection in CF
- sensitive to limited range of antibiotics
Oral anaerobes? Examples?
- Prevotella
- Porphyromonas
- Pasteurella
- Capnocytophyga
Mycobacterium tuberculosis? Characteristics?
- TB
- link HIV
- non and TB version of mycobacterium
Leprosy? Characteristics?
- Mycobacterium leprae
- attacks peripheral nerves
Spirochaetes? Characteristics?
- long spiral shaped bacteria
- not easily culturable
- diagnosed by serology
Syphilis? Characteristics?
- Primary syphilis: non-painful skin lesion (chancre) at the site of infection (skin or mucous membranes)
- Secondary syphilis (6-8 weeks after primary symptoms): generalised systemic illness and rash
- Latent phase: symptomatic episodes may occur
- Tertiary syphilis (years after primary symptoms): central nervous system
- Congenital syphilis: stillbirth, neonatal death or disease
- Diagnosis – serology, nucleic acid amplification tests (NAAT)
- Management – antibiotics, contact tracing and screening, antenatal screening
Lyme disease? Characteristics?
Transmitted by ticks
- Stage 1: Skin rash (erythema chronicum migrans) appears at the site of the tick bite
- Stage 2: Systemic illness occurs in some patients weeks or months later when patients suffer cardiac or neurological and musculoskeletal symptoms
- Stage 3: Chronic disease, occurring years later when patients present with chronic skin, nervous system or joint abnormalities
- Diagnosed by clinical assessment and serology (antibody detection)
Leptospirosis? Characteristics?
- Infects animals and concentrates largely in the kidneys
- Spread is via infected urine and other body fluids and tissues
- At-risk groups:
sewerage workers
watersports - Range of clinical presentations:
Weil’s disease – febrile illness with systemic upset, liver and renal failure, aseptic meningitis, 10 % mortality
Chlamydia? Characteristics?
- Obligate intracellular bacteria
- Culture only in cell lines (do not grow on agar)
- Respiratory Infection:
Chlamydophila pneumoniae
Chlamydophila psittaci (psittacosis)
Ophthalmic and genital tract infection
Chlamydia trachomatis:
- Trachoma (tropical eye infections)
- Genital and neonatal infection
Diagnosis of Chlamydia trachomatis:
- nucleic acid amplification tests (NAAT) on first void urine or vulval/vaginal swabs
