microbiology Flashcards
describe the different stages of pathogenic infection
exposure -> adhesion -> invasion -> colonisation -> toxicity -> tissue damage & disease
any microorganism that has the potential to cause disease
pathogen
likelihood of causing disease
virulence
how do you diagnose infection
history (noticing patterns, differentials)
examination (Review the differential diagnoses)
investigations (radiology, bio chem)
review differential diagnoses further (microbiology - blood urine, stool, wound, tissue culture (CSF, sputum, pus), serology, antigen detection, PCR
name an example of a gram negative bacilli
enterobacterociae
gram positive/negative cocci
streptococcus sp, enterococcus sp
spirochete
H. pylori
What colour does lactose fermenter turn MacConkey agar
pink
gram negative non spore forming grow on a variety of solid media ferment sugars facultative anaerobes mostly motile or non-motile increasing resistance
enterobacteriaceae
what are the different ways in which enterobacteriaceae can cause disease
motility (flagella allows movement, shigella and klebsiella not motile)
colonisation factors (fimbriae - filamentous appendages, shorter than flagellae, bind tight to tissue)
endotoxin (cell wall component)
enterotoxin (shiga toxin)
analyse protein composition of bacterial cell wall
uses a data base
Discriminates between highly genetically similar organisms with identical 16s rRNA
Pathogenic vs non-pathogenic E. coli may be difficult to differentiate
Some species are difficult for MALDI – TOF mass spectrometry differentiation e.g. Salmonella vs E. coli
MALDI-TOF
name some gram positives in the mouth
strep viridans neisseria sp anaerobes candida st staphylococci
name some normal flora of the stomach and duodenum (low pH)
usually sterile
few candida sp. and staphylococci may survive
what is the normal flora of the jejunum
small number of coliforms and anaerobes
what is the normal flora of the colon
large number of coliforms and enterococcus faecalis
T/F are there coliform in bile ducts
F, usually sterile
what anaerobes in the GI tract
WILL NOT grow in the presence of oxygen
Clostridium sp., Bacteroides sp., and anaerobic cocci
Present in large numbers in the large bowel
wider term that includes all agents that act against microorganisms, namely bacteria, fungi, viruses and protozoa
antimicrobials
act only on bacteria. broadly defined, this term encompasses all compounds that act against bacteria including antibiotics
antibacterials
a drug that kills or inhibits the growth of microorganisms
antibiotics
the ability of bacteria to protect themselves against the effects of an antibiotic, for example by pumping it out of the bacterial cell or by producing molecules that can destroy the antibiotic
antibiotic resistance
non-susceptibility to at least 1 agent in 3 of more antimicrobial categories
MDR
non-susceptibility to at least 1 agent in all but 2 or fewer antimicrobial categories (ie bacterial isolates remain susceptible to only 1 or 2 categories)
XDR
non-susceptibility to all agents in all antimicrobial categories (ie no agents tested as susceptible for that organism)
PDR
when microbes are resistant to one or more antimicrobial agents, used to treat infection or as an antiseptic
antimicrobial resistance
how is fighting back against antibiotic resistance carried out
improving antibiotic prescribing and use, aka stewardship
the optimal selection, dosage and duration of antimicrobial treatment that result in the best clinical outcome for the treatment or prevention of infection, with minimal toxicity to the patient and minimal impact on subsequent resistance
antimicrobial stewardship
