Bacterial Infection Flashcards
What are sterile sites?
Places where bacteria exist only pathologically:
- blood
- CSF
- urine
- peritoneal fluid
- pleural fluid
How do bacteria cause disease?
- direct: rupture, obstruction, pressure, cell destruction
- exotoxins
- pathogenic activation of immune system
What makes pathogenic bacteria distinct from the natural flora?
- acquire virulence factors
- gain access to deeper tissues
- immunocompromised patients
Name a bacterium that is always pathogenic
M. tuberculosis
Name three bacteria that are usually part of the gut flora but which may acquire virulence factors
- E. coli
- Staph aureus
- N. meningitidis
What were Koch’s postulates?
- Pathogen present in bacterial disease
- Culture grown
- Disease replicated through inoculation of susceptible healthy host
- Pathogen recoverable from 2nd host
What’s the difference between colonisation & infection?
Infection - invasion & growth
Colonisation - presence & replication WITHOUT interaction with host
What is the difference between Gram +ve and Gram -ve bacteria?
+ve: thick peptidoglycan, purple stain
-ve: thin peptidoglycan, pink stain
Gram -ve rods
Reservoir: gut
Path site: biliary tree, urine
e.g.: E.coli, shigella, Klebsiella
Gram +ve rods/bacilli
Reservoir: soil
Path site: wounds
e.g.: C.diff, listeria, gardnerella, bacillus
Gram -ve cocci
Reservoir: (depends)
Path site: urogenital, URT
e.g.: pasturella, neisseria
Gram +ve cocci
Reservoir: skin, genitourinary
Path site: systemic, fascia, skin
e.g.: staph aureus, streptococci
Spirochaetes
Reservoir: free living/host
Path site: genitourinary
e.g.: leptospirosis, syphylis
Rickettsia
Reservoir: zoonoses
Path site: endothelial, lungs
e.g.: Q fever, scrub typhus
Mycobacteria
Reservoir: environment & ppl
Path site: lungs, skin
e.g.: TB, M.leprae
Which diseases are commonly caused by infection with Gm- bacilli?
Endogenous:
- biliary sepsis
- urinary sepsis
- peritonitis
Exogenous:
- GE (ETEC, EPEC, shigella, salmonella)
- typhoid
Why are Gm -ve rods typically treated with broad-spectrum Abx?
Plasmid exchange of resistance genes & virulence factors = broad spectrum resistance & high pathogenicity
What infections are commonly caused by Gm+ve cocci?
Skin & soft tissue:
- cellulitis
- osteomyelitis
- septic arthritis
- discitis
- endocarditis
How does MRSA present?
- skin infections (cellulitis)
- Cx infections (pneumonia)
- endocarditis
- osteomyelitis
- bacteraemia
- death
How does C.diff present?
- watery diarrhoea
- abdo pain
- pseudomembranous colitis
- dehydration
- bowel perf
- death
How is C.diff treated?
- metronidazole
- vancomycin, po
- fidaxomicin
- donor faecal transplant (FMT)
Which bacteria are in the enterobacteriaceae family? (Gut flora)
- E.coli
- klebsiella
- enterobacter
- proteus
- salmonella
- serratia
- citrobacter
Name the most common carbapenemases
- KPC
- OXA-48
- NDM
- VIM
Who is at risk of MDR acinetobacter?
MILITARY - Iraq & Afghanistan
(Gm-ve bacillus) ?colistin, tigecycline
- biofilms on wound & equipment
- withstands desiccation
- VAP & wound colonisation due t battlefield trauma
