Bacteria Flashcards
define pathogen
micoorganism capable of causing disease
define opportunistic
rarely causes disease in immunocompetent individuals but can cause severe disease in those with weakened immune response
define bacteremia
bacteria in the bloodstream
define sepsis
systemic immune response to the infection
define septic shock
hypotension, organ dysfunction
- common deadly response to gram positive & negative infections
- high mortality rate
Define gram results
purple/blue = gram positive
- thick 2 layer cell wall
- no porin channel or endotoxin
- vulnerable to lysozyme & PCN
pink/red = gram negative
- thin 3 layer cell wall envelope with porin channel
- endotoxin-Lipid A
- resistant to lysozyme & PCN
Describe the coverage & MOA of Beta-Lactams
PCN, cephalosporins (3-5 gen), carbapenems
- inhibit cell wall synthesis
- cover gram negative bacteria
What are the 4 major morphologies of bacteria
- cocci: spherical
- bacilli: rod shaped
- spiral
- pleomorphic: lack distinct shape
can organize together to form pairs, clusters, chains, single bacteria with flagella
Describe some bench tests
used to further differentiate species
- coagulase test: differentiates staph species
- catalase tests: distinguishes staph v strep v enterococci
- oxidase: differentiates gram negative bacilli
- lancefield grouping: used for strep species
Describe some gram positive bacteria
Describe some gram negative bacteria
cocci
- neiserria
- moraxella diplococcus
spirochetes
- treponema pallidum
- borrelia
- leptospira
pleomorphic
- chlamydia
- rickettsia
bacilli/rods
- pretty much everything else (enterics & others)
Which bacteria is neither gram positive or negative?
Mycoplasma, no cell wall
What is referred to as walking pneumonia
mycoplasma pneumonia
- MC cause of atypical pneumonia
- low grade F, dry non-productive cough
- Tx with Azithromycin, doxy, or fluoroquinolone
What are some AEs of fluoroquinolones
QT prolongation, cartilage issues
Describe the difference between aerobic vs anaerobic bacteria
Obligate Aerobes
- uses oxygen
- breaks down oxygen with enzymes
Obligate anaerobes
- hates oxygen
- no enzymes to defend against oxygen
Facultative anaerobes
- aerobics
- ability to be anaerobic but don’t prefer it
Describe endotoxins
proteins released by some Gm+ and Gm- bacteria
describe neurotoxins
acts on nerves (paralysis
- tetanus, botulinum
describe enterotoxins
acts on GI tract (diarrhea)
- vibrio, e coli, campylobacter, shigella
describe pyrogenic endotoxins
lead to rash, fever, toxic shock
- staph aureus, GABHS
Describe tissue evasive endotoxins
allow bacteria to destroy tissues (GABHS)
Which abx lower seizure thresholds
cephalosporins
Describe a sterile site vs non-sterile site for cultures
differentiates if this is a true pathogen or part of the normal flora
- sterile: CSF, pleural fluid, pericardial fluid, synovial fluid, peritoneal fluid (where bacteria is not present usually)
- non-sterile: skin, oropharynx, nose, ears, eyes, throat, perineum
What to consider when interpreting a culture result
- coag negative staph (usually just staph epidermidis - skin contaminant from procedure)
- assess for WBCs, nitrites, leukocyte esterase in UA along with culture
- sputum culture with poor sensitivity & specificity
- squam epithelial cells present reduces likelihood that bacteria is pathogenic
What is the most common organism that causes UTIs
e coli
What are the 3 types of gram+ cocci
streptococcus chains, enterococcus chains, staphylococcus clusters
Describe the types of hemolysis in streptococci (classifications)
- Alpha-hemolytic: incomplete destruction of RBC (strep pneum, strep viridans)
- Beta-hemolytic: complete destruction of RBC (strep pyogenes, GABHS, GBBHS, GDBHS)
- gramma-hemolytic: no destruction of RBC
Which strep viridans species causes dental caries
strep mutans
What pathologies does strep pneumoniae cause
pneumonia, meningitis, otitis media
What pathologies does strep viridians cause
subacute bacterial endocarditis, dental caries, brain or liver abscess
What pathologies does GABHS (strep pyogenes) cause
pharyngitis, scarlet fever, skin infections, toxic shock syndrome, non-suppurative complications
What are the Jones criteria for acute rheumatic fever diagnosis
need 2 major OR one major & two minor sxs
Major: carditis, arthritis, sydenham chorea, erythema marginatum, subQ nodules
Minor: fever, arthralgia, previous RF or rheumatic heart disease, acute phase reactions, prolonged PR interval
What do you treat rheumatic fever with
PCN or cephalosporin
Macrolides if PCN allergy
(early tx of strep is key to prevention, recurrence is common)
What pathologies does GBBHS cause
think B for baby - newborn/neonates
Neonatal meningitis, pneumonia, sepsis
What pathologies does GDBHS cause
subacute bacterial endocarditis, biliary tract infections, UTIs
What do you treat GDBHS with
ampicillin + aminoglycoside (severe)
Ampicillin, amoxicilli for E Faecalis UTI
Treat with Vanco if resistent
Describe the MOA, coverage, and AEs for vancomycin
MOA: inhibits cell wall synthesis (not a beta lactam)
Coverage: gram+, MRSA, c. diff
AEs: nephrotoxic, red man syndrome (slow infusion can avoid)
What do you treat VRE with
vancomycin resistant enterococcus
daptomycin or linezolid
Which gram+ staphylococci are coagulase positive v negative
Coag positive: staph aureus
Coag negative: staph epidermidis, staph saprophyticus
Which pathologies does staph aureus cause
- acute bacterial endocarditis
- osteomyelitis
- pneumonia
- septic arthritis
- skin infections
- blood & catheter infections
- Toxic shock syndrome
What pathologies does staph epidermidis cause
UTI in sexually active, pathogenic in prosthetic joints & heart valves
What are the 2 classes of MRSA and how do you treat skin/soft tissue infections
HA-MRSA & CA-MRSA (hospital vs community acuired)
Tx with oral abx: SMX-TMP, tetracycline, clindamycin
Tx with parenteral abx: vanco, dapto
What is an example of an acid0fast gram+ bacilli
mycobacterium
Describe the etiology & treatment of bacillus antracis
anthrax
- only bacteria with a capsule made of protein, aerobe, forms endospores, makes exotoxins
Treat with cipro or another FQ, antitoxin (prognosis excellent for cutaneous, poor for inhaled/GI anthrax)
Describe the etiology of clostridium botulinum
botulism
- produces extremely lethal neurotoxins that block Ach release
- foodborne, infant spores in honey, wound injection site
Describe the clinical presentation & treatment of botulism
- symmetric descending weakness
- CN dysfunction: diplopia, nystagmus, ptosis, dysphagia, dysarthria, facial weakness
- respiratory paralysis
- no mental status change
- floppy baby syndrome
Treat with antitoxin from the CDC, intubation, supportive care
Describe the etiology of tetanus
Clostridium tetani
Classically follows a puncture wound by rusty nail
Spores deposited in the wound & endotoxin released
Describe the clinical presentation of tetanus
Pain & tingling at site of inoculation, sustained contraction of skeletal muscles, severe muscle spasm, trismus, grinning expression, death
Describe the treatment for tetanus
IM tetanus immunoglobulin, supportive care, mechanical ventilation
PCN
Describe the etiology of clostridioides difficile
Aka c diff
Common nosocomial infection, typically follows use of broad spectrum abx (ampicillin, clindamycin, FQs, cephalosporins)
Releases exotoxins
Describe the diagnostic testing for C. diff
CBC - leukocytosis
Toxin testing in stool
Colonoscopy may reveal red inflamed mucosa & areas of white exudate (pseudomembranes)
Describe the treatment for c. diff
D/c original antibiotic, infection control
Oral vancomycin or fidaxomicin
+/- fecal microbiota transplantation
Describe the etiology of diphtheria
Cornybacterium diphtheria
Transmitted by respiratory secretions & colonizes pharynx, releases exotoxins
Describe the clinical presentation of diphtheria
Gray pseudomembrane that bleeds when picked, myocarditis & neuropathy d/t exotoxins in bloodstream
Describe the treatment for diphtheria
Horse serum antitoxin
PCN or azithromycin/ erythromycin, DPT vax
Describe the clinical presentation of syphilis
Primary: painless chancre on genitals
Secondary: rash on palms & soles, condyloma latum (wart), Systemic sxs: fever & LAD, may affect CNS, eyes, bones, kidneys, joints
Tertiary: develops over 6-40 years, gummas of skin & bond, CV (aortic aneurysm), neurosyphilis
Latent: sxs resolved, serologic testing still positive
What is the treatment for syphilis
PCN G (Benzathine) IM x1
Describe the clinical presentation of lyme
Stage 1: localized
- erythema migrans rash
Stage 2: disseminated
- smaller rashes
- neuro: meningitis, CN palsies, peripheral neuropathy
- cardiac: myocarditis
- arthritis: brief, large joints
Stage 3: late stage
- chronic arthritis
- encephalopathy
What is the treatment for lime
doxycycline
Describe the etiology of rocky mountain fever
Rickettsia rickettsii
Obligate intracellular parasite
More common in SE US
Describe the clinical presentation of rocky mountain spotted fever
Presents 1 week after bite from wood tick or dog tick
Fever, conjunctival redness, severe HA, rash on palms, soles & wrists moving to ankles & trunk
What is the treatment for rocky mountain spotted fever
prompt doxycycline
Describe the etiology of pertussis/Whooping Cough
Bordatella pertussis
highly contagious
Describe the clinical presentation of pertussis
Stage 1: Catarrhal, gradual onset of cough mostly at night, cold sxs, most infectious stage
Stage 2: paroxysmal, classic whoop
Stage 3: convalescent, decrease in frequency & severity of sxs, usually 4 weeks after onset
Describe the diagnostic testing of pertussis
nasopharyngeal swab & culture
describe the treatment for pertussis
Macrolide - Azithromycin, treat household contacts
What is the treatment for legionnaire’s disease
Azithromycin
