Bacteria Flashcards
characteristics of prokaryotes
- no DNA within nuclear membrane
- no DNA associated with histones
- no membrane bound organelles
- no mitotic divisions
- 1 chromosome
- 70 s = chromosome size
- cell wall containing peptidoglycan present
characteristics of gram positive bacteria and stains
- thick, multiple peptidoglycan layers
- contains teichoic acid which constitutes major surface antigens
- stains blue to purple-blue because decolorization does not get rid of primary stain
Characteristics and causes of positive gram bacteria Staphylococcus aurens
found in areas with hair (nasal cavity, groin, inguinal area, axilla, hairline)
causes a lot of infections
causes:
- pneumonia
- osteomyelitis
- infective endocarditis
- soft tissue infections
- septicemia
- food poisoning
Characteristics and causes of positive gram bacteria Coagulase negative Staph
found in normal skin commensals
causes opportunistic infections in patients with:
- catheters
- IV fusions
- orthopedic prosthesis
- artificial cardiac valves
Characteristics and causes of positive gram bacteria streptococci
found in URT
streptococcus pyogens
- rheumatic fever and heart disease (autoimmune disease if not treated)
- otitis media
- pharyngotonsilitis
- soft tissue infection
- scarlet fever
streptococcus pheumoniae
- common cause of pneumonia in HIV/AIDS patients
- children used to struggle before there was a vaccine
- pneumonia
- meningitis
- sinusitis
Characteristics and causes of positive gram bacteria Enterococci
found in GIT
causes:
- enterococcus faecalis
- enterococcus faecium
- UTI and infective endocarditis
- wound infections
Characteristics of gram negative bacteria and stains
stains pink/red
- discoloration causes primary stain to disappear and bacteria takes on second stain
contains 2 layers:
1. thin peptidoglycan layer
2. outer-membrane containing porines
- lipopolysaccharide containing lipid portion and polysaccharide chain
- NB because when released from cell wall it is toxic to mammals and causes:
- fever
- changes in white blood cell count
- cytokine release
- disseminated intravascular coagulation
- decreased BP leading to vascular collapse, shock and death
what are some clinically NB gram positive bacilli
spore forming
- bacillus
- clostridium
non-spore forming
- corynebacterium
- listeria
- lactobacillus
bacilli with branching filaments
- actinomyces
- nocardia
defirium
- life threatening, causing URTI
- medical emergency
characteristics of non-spore forming positive bacteria bacilli listeria
- one of causes of neonatal sepsis/ meningitis (mom to child infection)
- not killed by cold temperatures
Characteristics and causes of gram negative bacteria pseudomonas
- bacilli
- likes moist environments
- common cause of infection in burns patients
found in - soil, water, sewage
- usually hospital acquired
causes - LRTI
- chronic otitis externa
- secondary eye infections
- infections on pressure sores, varicose veins. ulcers
- catheters (UTI)
- mechanical ventilation
Characteristics and causes of gram negative bacteria Acinetobacter
- bacilli
- resistant to multiple antibiotics
- can survive for long periods in an environment
found in - environmental organisms
- infections in hospitalised and immunocompromised patients, especially those in ICU
causes - colonizes intravascular catheters or other invasive devices
Characteristics and causes of gram negative bacteria escherichia coli
- bacilli
found in - normal flora of GIT
causes - UTI
- wound infections
- peritonitis
- septicemia
- neonatal meningitis
Characteristics and causes of gram negative bacteria Klebsiella
- bacilli
found in - normal GIT flora
- saprophyte in soil, water and plant material
- hospital wash basins and baths
causes - most NB: Klebsiella pneumoniae
- UTI
- septicemia
- meningitis esp. neonates, young children
- abscessess
- pneumonia
Characteristics and causes of gram negative bacteria Shigella
- bacilli
found in - not normal flora
- person to person transmission
- highly infectious
causes - dysentery
- high secondary attack rate
Characteristics and causes of gram negative bacteria Salmonella
found in
- non-typhoidal is acquired via ingestion of contaminated animal products
- Salmonella typhi (reservoir, person to person transmission)
causes
- non-typhoidal: GIT disease
- salmonella typhi: enteric fever
- salmonella species can also cause focal infections
Characteristics and causes of gram negative bacteria proteus species (especially proteus mirabilis), enterobacter species
found in normal flora of GIT
causes
- HAI
- wound infections
- line infections
- UTI
- ear infections
Characteristics and causes of gram negative bacteria neiserra meningitidis (meningococcus)
- diplococcus
- transmitted by droplet spread
- causes meningitis, sepsis and focal infections
- high mortality if not treated immediately and appropriately
- highly contagious
- notifiable disease
- isolation, standard and droplet precautions
- pep given
- vaccine available but not part of immunization program
characteristics of normal flora
non-pathogenic microorganisms found on mucosal surface and skin
relationships:
- mutualism
- commensalism
delays in transporting a specimen to the lab for processing impacts on culture results as normal flora overgrows preventing proper diagnosis of infections
Advantages and Disadvantages of GIT normal flora
advantages
- assist digestion of food
- protect from colonialization by pathogens
- activate immune response
disadvantages
- cause disease when entering sterile site
- opportunistic pathogens
What factors affect normal flora
- antibiotic treatment
- diet
- stress
- host response to flora
define commensals
organisms living in a relationship in which one organism derives benefits e.g. nutrients from another without harming it
define colonization
continued presence of organism on body sites without causing damage/invasion
define infection
damage/invasion of host tissues associated with organisms
define infection by primary pathogen
cause infection in patients with normal immunity and is highly virulent
define infection by opportunistic pathogen
cause infections in patients with depressed immunity/ when normal flora gain entry into sterile site
define virulence
ability of an organism to cause disease: mainly evading/ overstimulating host immune response
define reservoire
where an organism/ pathogen lives and multiplies
define source
site from which an organism/ pathogen spreads to host, objects
What is infection control and prevention
Inventions/measures, practices, guidelines protocols aimed at
- prevention
- early identification
- control of infections in health care settings and/or community
What are community acquired infections
Infections due to everyday exposure to microorganisms in the community
