Medical Microbiology Flashcards
non sterile body sites
mouth, oesophagus, lungs, stomach, intestine
sterile body sites
brain, heart, liver, kidney
common specimen types collected to diagnose infection
MSSU (urine), sputum, throat swab, swabs, faeces, blood culture, cerebrospinal fluid, aspirate of pus, bone
what is role of culture microscopy in diagnosis of bacterial infection
non specific but assists provisional diagnosis and empiric antimicrobial therapy
methods of detecting viruses
molecular methods- PCR, antigen detection, serology to determine immunity, electron microscopy, cell or tissue culture
main structures of bacterial cell
chromosome, cytoplasm, cell wall, ribosome, penicillin binding proteins, lipopolysaccharide, capsule, flagella, fimbriae, plasmid, bacteriophage, spores, peptidoglycan
how do bacteria replicate and create genetic variation
binary fission and transfer DNA via plasmids, spontaneous mutation
how is bacteria detected
individual can only be seen with a microscope. use stains like gram stain and fluorescent dyes
lysis
wall is weakened or ruptured so cell swells and bursts due to osmosis
lipopolysaccharide
only present in gram negative bacteria, protects peptidoglycan from bile salts and blocks antibiotics from getting into cell.
lipid A
in lipopolysaccharide. forms endotoxin which may give rise to endotoxin shock if released in bloodstream- fever and low blood pressure
bacteriophages
virus that infects bacteria
what is Svedberg unit
measure of sediment rather than size
how is bacteria cultured
agar. colonies can be seen by eye
main groups of parasites
protozoa(malaria), helminths (tapeworms), ectoparasites (lice)
protozoa
able to multiply in humans. transmitted by faecal- oral route or insect vector. amoebic dysentry and plasmodium causing malaria is example
common diseases caused by enteric and blood borne parasites
Schistosomiasis, malaria, pinworms,
how is parasitic infection diagnosed (3)
identification of parasites in host tissue or faeces or urine. blood microscopy, stool microscopy- look for ova, cysts, parasites. Indirect testing- rapid diagnostic test or serology
nematodes transmission route
faecal oral eg pinworm
cestodes transmission route
eating raw or uncooked meat. use a intermediary host eg beef tapeworm
trematodes transmission route
contact with freshwater where the snail intermediary host is present eg schistosomiasis
virion structure
lipid envelope around the outside with spike projections, protein capsule on inside, virion associated polymerase inside of that
virus replication
enter cell, uncoated, genomic nucleic acid replicated in the nucleus, mRNA synthesis, protein synthesis, newly synthesised virus proteins inserted into membrane and genomic nucleic acid put into virion again and then budded and released with lipid envelope back on. mature and then attach and enter another cell again
types of transmission of virus
blood borne, sexual, airborne, droplet, faecal oral, close contact
why is confection of human and animal or bird strains in one generation dangerous
may lead to recombination and generation of a new strain
consequences of viral infection
clearance of virus (with short, no, or long term immunity), chronic infection, latent infection, transformation
viral latency
after primary infection, viruses lie dormant in cell, viral genome is retained, reactivation of viral replication can occur and this may or may not cause apparent disease. bad for immunocompromised. examples- herpes simplex virus
how can viruses lead to cancer
modulation of cell cycle, modulation of apoptosis, reactive oxygen species mediated damage
all antiviral agents are ____ none are _____
virustatic, virucidal
antivirals can be used for
prophylaxis (to prevent infection), pre-emptive therapy (evidence of infection detected but before symptoms apparent), overt disease, suppressive therapy (to keep viral replication below rate that causes tissue damage)
ways of preventing viral infection
immunisation, prophylactic treatment post exposure, infection prevention and control measures, blood/tissue/organ screening, antenatal screening
what is a fungus
chemo-organotrophic eukaryote that lacks chlorophyll and forms spores. absorbs nutrients
what does a fungal membrane contain as the major sterol
ergosterol
3 major groups of fungi
basidiomycetes, ascomycetes, zygomycetes
dermatophyte fungi that cause skin infections main virulence factor is
enzymes that degrade and utilise keratin as a nutrient source
malassezia species role in health and disease
colonisers of healthy skin, especially sebum rich areas,. can cause superficial infections in susceptible skin and wide range of infections in immunocompromised and premature neonates
host factors that contribute to pathogenicity of fungal infections
favourable microenvironments, broad spectrum antibacterial agents, immunosuppression
forms of immunosuppression of host defences
latrogenic(steroids, anti cancer chemotherapy), disease processes(AIDS leukaemia) or combination of both
candida infections human diseases
oral, penis, vaginal, skin, urinary tract infections
what kind of species are candida species
yeast
what can Candida albicans form
hyphae
thrush is caused by what fungal infection
candida
aspergillosis route of infection
inhalation of conidia which germinate to hyphae in lung tissue. it is angioinvasive also
types of disease caused by aspergillosis
simple asthma, asthma with eosinophilia, aspergilloma
human diseases caused by cryptococcosis
pulmonary cryptococcosis, meningitis, diessemated infection in severely compromised hosts
what is the damage response interaction
fungal infections. means that if the host response to the infection is too strong or too weak, this will result in disease
how to detect fungal infections
direct detection- histopathology, high res CT scans, growth on selective medium
PCR for fungal DNA, detection of circulating antibodies to fungi
problems with anti fungals
cost, static, IV vs oral, toxicity, resistance
types of anti fungal agents
polyenes, azoles, echoinocandins
what type of bacteria form spores
bacilli and clostridium
spirochaetes
spiral shaped bacteria causing syphilis, lames disease, relapsing fever
examples of genera of spirochetes
Spirochaeta, Treponema, Borrelia, and Leptospira
bacterial typing
way of identifying strains of microorganisms
fimbriae and pili
thin protein tubes that extend out of bacteria and help them with adhesion to surfaces. pili are longer and fewer. found in gram negative bacteria but not gram positive
