bacteria Flashcards
what is a prion
abnormal form of normal human protein - no detectable nucleic acid. can change from alpha helical to beta sheet
what are the 3 different classifications of shape and gram stains of bacteria?
cocci, rod/bacilus and coccobacilli
distinguish between gram positive and gram negative bacteria
gram positive have techoic acid, a thicker peptidoglycan wall and are able to stand drying better than gram negative. Some gram positive have spores, negative never have spores. Gram positive bacteria produce exotoxins, gram negative produce endotoxins and some also produce exotoxins; they also have an outer membrane over the peptidoglycans made of polysaccharides
what is a mycobacteria? what are its characteristics?
gram positive in structure but unable to stain due to cell being rich in waxy mycolic acids
considered a weak gram positive
non-spore forming
non-motile ROD
what do you use to stain mycobacteria?
ZN stain - need heat to stain
gram positive cocci found in cluster indicate what?
staph aureus
what do staph aureus make?
exotocins
enterotoxins cause food poisoning
toxic shock toxin cause staphylococcus toxic shock, rash, renal impairment
pneumonia following influenza likely to be what bacteria?
staph aureus
pneumonia most common bacteria is?
streptococci pneumoniae
how to identify staph aureus in lab?
golden colonies on blood agar
what kind of bacteria is staph aureus?
gram positive cocci
what kind of bacteria is streptococci?
gram positive cocci
gram positive cocci found in pairs is what?
streptococci
if slightly elongated typical of streotococcus pneumoniae
what are the main strep bacteria of group a and b and what diseases do they cause?
group a: streptococcus pyogenes - sore throat, impetigo, cellulitis - flesh eating virus
group b: streptococcus agalactiae - neonatal sepsis - carried in the vagina
what diseases can staph aureus cause?
bloodstream infection, endocarditis, osteomyelitis, septic arthritis, pneumonia
where is staph aureus normally located?
skin, nasal lining, eyes, throat, numerous places in human body
where is strep normally found?
in moist openings - oral cavity, genital openings,
what are the three types of gram positive rods?
anaerobic spore forming, aerobic spore forming and non spore forming
what are examples of anaerobic spore forming bacteria and what diseases do they cause?
Clostridium bacteria eg. c. diff (antibiotic associated diarrhoea), c. tetani (causes tetanus), c. botulinum (botulism - patients can die of respiratory failure)
what are examples of aerobic spore forming bacteria and what diseases do they cause?
bacillus species e.g. b.anthracis, b.cereus (food poisoning)
what are examples of non spore forming bacteria and what diseases do they cause?
corynebacterium dipptheria, Listeria (blood stream infection, meningitis and neonatal sepsis)
what are examples of gram negative cocci
Neisseria family - meningitides or gonorrhoea
what kind of bacteria are neisseria bacterias? and what diseases do they cause?
Gram negative cocci
meningitis (can progress to spesis with bloodstream invasion + haemorrhagic rash), gonnorhoea
what are examples of gram negative rods?
Enterobacteriocae - e.coli, klebsiella, salmonella, proteus
pseudomonas aeruginosa
legionella
haemophillus influenza
what are the common enterobacteriacae? and what diseases do they cause?
e.coli, klebsiella, proteus, salmonella
infections of urinary tract, bloodstream; bacterial food poisoning; intraabdominal infections such as appendicitis
when are you likely to have a pseudomonas aeruginosa infection and what does it cause?
in healthcare setting, and in immunocompromised patients
causes bloodstream and urinary tract infections
when are you likely to have a legionella infection and what does it cause?
in poorly maintained water situations - stagnant pools of water contaminated around - cooling system perhaps
causes pneumonia
what kind of bacteria is haemophillus influenza?
gram negative rod
what kind of bacteria is legionella?
gram negative rod
what kind of bacteria is e.coli?
gram negative rod
what kind of bacteria is proteus?
gram negative rod
what kind of bacteria is salmonella?
gram negative rod
what kind of bacteria is pseudomonas?
gram negative rod
how do you identify different streptococci from each other in the lab?
see alpha haemolysis for streptococci pneumonitis, see beta haemolysis for strep agala and strep
when would you use PCR to indentify bacteria?
when other methods are too difficult, insensitive or take too long - can rapidly diagnose many respiratory viruses: RSV, influenza a and b, rhinovirus, parainfluenza
how do you identify chlamydia or neisseria gonorrhoea
with PCR
define SEPSIS
SIRS + caused by known or suspected infection
SIRS requirement: at least 2 of the following
- HR over 90
- RR over 20
- temp over 38 or below 36
- WBC over 12k or below 4k
What are the SEPSIS 6
- give high flow oxygen
- take blood cultures
- give broad spectrum antibiotics (IV if possible)
- give IV fluids
- measure serum lactate and haemoglobin
- measure accurate hourly urine output
must all be done within first hour to double patients chances of survival
define severe sepsis
SEPSIS plus at least 1 organ failure
what components can trigger sepsis?
endotoxins, lipotechoic acid, TLRs, complement and coagulation cascades, depletion of protein c
what makes superantigen trigger sepsis faster?
brings t cells and MHC II together directly leading to faster inflammatory response
what is septic shock
sepsis with persistent REFRACTORY HYPOTENSION or TISSUE HYPOPERFUSION despite adequate fluid resuscitation
what is the most standard treatment for community acquired sepsis? if origin unknown, gut, renal or billiary
co-amoxiclav + gentamicin
beta lactams what are the three classes, what kind of bacteria does it work against and what mechanism does it use?
penincillin, cephalosporin, carbepenems
used for gram positive and negative
mechanism: beta lactems inhibit synthesis of peptidoglycans
penincillin examples? and what are they used for?
penincillin, co-amoxiclav, amoxicillin (gram neg), tazobactam (pseudomonas), flucloxacillin (anti-staph)
cephalosporin examples? + used for what?
cefelaxin (UTI), cefurosime, ceftriaxone/cefotasime (meningitis blind therapy), ceftazidime (gram neg)
carbapenem examples? plus uses?
meropenem (for pseudomonas aeruginosa), ertapenem
beta lactase + PBP?
bacteria’s way to fight beta lactams, beta lactase breaks beta lactam down, and PBP are penincillin binding protein that beta lactams bind to - these can be altered so they are no longer inhibited by drugs e.g. meticillin - flucloxacillin = MRSA, or
how is VRE resistant?
VRE changes cell wall pentapeptide from D-alanine D-alanine to D-alanine D-lactate that vancomycin doesn’t bind to
macrolides? examples plus used for what? how does it work also?
used for gram positive bacteria (Esp if allergic to penincillins) in soft tissue, sore throat, skin infections e.g. CLARITHROMYCIN, azithromycin, erythromycin
works by interfering w protein synthesis through binding of ribosome
tetracyclines? examples plus used for what? how does it work also?
used for gram positive bacteria (like macrolides) for soft tissue and respiratory infections for ppl who are allergic to penincillins e.g. oxytetracycline, doxycycline
work by inhibiting binding of tRNA to ribosome
trimethoprims/co-trimoxazole? used for what? how does it work also?
used for gram positive and gram negative bacteria
trimethoprim used against UTI, cystitis
co-trimoxazole is trimethoprim + sulfamethoxazole - synergistic effect - used for treatment + prophylaxis of pneumocystis jirovecii pneumonia + other immunocompromised associated diseases
side effect of sulfamethoxazole - steven johnson syndrome + bone marrow aplasia
works by inhibiting bacterial nucleotide synthesis
quinalones? examples plus used for what? how does it work also?
used against gram negative bacteria e.g. ciprofloxacin (though newer ones - levoflaxacin+moxifloxacin good at gram pos also - resp quinalones)
works by inhibiting DNA gyrase (that supercoils DNA in bacteria)
aminoglycosides? examples plus used for what? how does it work also?
used against gram-negative bacteria predominantly, used principally in SERIOUS SEPSIS can only be given in hospital because can cause 8th nerve toxicity + renal toxicity - serum levels must be carefully monitored. e.g. GENTAMICIN, amikacin, netilmicin, tobramycin
(synergistic w penincillins e.g. co-amoxiclav)
works by inhibiting reading of mRNA by ribosome
glycopeptides? examples plus used for what?
ONLY WORKS FOR GRAM POSITIVE
main example is VANCOMYCIN used predominantly for treating MRSA and other coagulase neg staph infections. very potent and potentially nephrotoxic can only be given in hospitals where serums can be monitored closely
teicoplanin less toxic can be given as outpatient
metronidazole?
affects nucleic acid - breaks DNA strands, effective against all anaerobes. used esp for intra- abdominal sepsis - leakage of gut content
linezolid?
treats gram positive esp VRE and MRSA
chloramphenicol?
for bone marrow toxicity and occasionally meningitis (W severe pen allergy) and topical treatment of eye infections
fosfomycin?
treats increasingly resistant gram neg bacteria
daptomycin?
treats gram positive, like vancomycin
fusidic acid?
only treats STAHP infections. topical treatment
rifampicin?
treats gram positive infections especially prosthetic valve endocarditis and other prosthetic infections ALWAYS used with vancomycin and is part of 1st line for TB
rifampicin?
treats gram positive infections especially prosthetic valve endocarditis and other prosthetic infections ALWAYS used with vancomycin and is part of 1st line for TB
name a few anti-fungals
give azoles like itraconazole, voricaonazole, posconazole… if very severe go for liposomal amphotericin B
name a few anti-fungals
give azoles like itraconazole, voricaonazole, posconazole… if very severe go for liposomal amphotericin B
causes of meningitis in neonates? early and late
for both think strep agalactiae
within first week of life think e.coli, listeria monocytogenes
within 1-6 weeks think l. monocytogenes and gram negative bacilli
main causes of meningitis?
highest cause globally from children to adults is strep. pneumoniae or pneumonoccal meningitis and also think meningococcal meningitis (neisseria meningitidis)
in elderly and immunocompromised also think l.mono
viral causes more likely from 20s-40s : enterovirus, herpes simplex, mumps
cause of meningitis in elderly?
strep pneu, neis menin and l.mono
cause of meningitis in immunocompromised?
strep pneu, n. meningitidis, l. monocytogenes
nosocomial cause of meningitis?
staph aureus, s. epidermidis, gram negative bacilli
viral causes of meningitis?
viral causes more likely from 20s-40s : enterovirus, herpes simplex, mumps
symptoms of meningitis?
main 4:
- fever
- headache
- stiff neck
- altered mental state
95% have at least 2/4
others:
- photophobia!!!
- nausea
- vomiting
- lethargy, irritability
how to diagnose meningitis?
with lumbar puncture
see elevated opening pressure, elevated white cells, elevated proteins, reduced glucose
can use it to culture organism
turbid CSF is what type of meningitis?
bacterial
neutrophils>lymphocytes in CSF is what type of meningitis? opposite is?
bacterial
opposite is TB or viral
raised protein in CSF is what type of meningitis?
mildly raised: viral,
raised: bacterial,
markedly raised: TB
raised opening pressure of CSF only mildly raised is what type of meningitis?
viral
cloudy CSF is what kind of meningitis?
TB
how to differentiate TB from bacterial meningitis?
both have raised opening pressure and very low plasma glucose ratio BUT TB has higher CSF protein levels, is cloudy not turbid and has lymphocytes not neutrophils
what are red flag signs of septicaemia in kids?
limb pain, cold hands and feet, pale or mottled skin, fast/laboured breathing, diarrhoea
in older kids: thirst
younger people shouldn’t get drowsy - mental status holds out until last possible stage so if you see this be worried
how does meningitis damage the body?
endotoxins released - inflammatory response –> widespread vasodilation –> myocardial damage/vessel damage –> hypoperfusion of tissues
abnormal clotting - blocked areas leading to gangrene requiring amputation - disseminated intravascular coagulation in meningococcal septicaemia
what’s most likely to happen if infected with TB
90-95% of the time it leads to latent TB and inly 10% get reactivation 2-50 years later. so most of the time nothing happens
5% can’t contain initial infection and will progress straight to classical pulnomary TB (primary TB)
what APCs recognise MTB TB?
TL2 and TL4
what cytokines are produced in TB?
IL-2, TNF, INF
describe immunopathology of TB
infection in alveoli. APCs activate t cells to produce cytokines, macrophages also cause phagocytosis and O/N mediated killing. CD8/NK cells also cause tissue destruction.
what are the different strains of TB?
Oshkosh - hypervirulent in humans, bad outbreak, 10% get reactivation
CLADE variations:
- Beijing lineage: most common strain, low macrophage uptake and cytokine induction, high replicative potential
- Haarlem lineage: high uptake, cytokine induction and growth rate
- EAI: low uptake, cytokine production and replicative potential
what are the symptoms of TB?
malaise, fatigue + constitutional symptoms: fever, night sweats, weight loss
COUGH is non-productive, might be haemoptysis
might have SOB in late TB
pleural effusion can be seen in in later stages as well
what is the treatment for TB?
Combination of 4 drugs:
- rifampicin
- isoniazid
- ethambutol
- pyrazinamide
if you see a cervical lymph node collar stud abscess think what and nothing else?
TB
what is a common infective cause of Addison’s
TB
what are the big five HCAI
- MRSA
- C.Diff
- Norovirus
- MPR gram negative bacteria
- VRE
which drugs are most likely to lead to c.diff?
lincozimides and cephalosporins
how to treat MRSA?
vancomycin
if that fails can also try linezolid or damptomycin
how to treat VRE?
Linezolid
maybe damptomycin???????
how to treat MDR gram neg bacteria?
colistin or fosfomycin ???
