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-signs and symptoms, including fever, elevated WBC count, and site specific symptoms (ex: dysuria with UTI)
-diagnostic findings, such as culture results, xrays, and markers of inflammation (procalcitonin)
the presence of infection is determined by: clinical evaluation and laboratory tests.
-the infection site and likely organisms
-infection severity and risk of multidrug resistant (MDR) pathogens (ex: community vs hospital acquired infections)
-antibiotic characteristics (ability to penetrate site of infection)
-patient characteristics (age, weight, allergies, renal/hepatic function, comorbidities, recent abx use, pregnancy, etc)
-treatment guidelines
antibiotic selection is based on:
streptococcus pneumoniae, neisseria meningitidis, haemophilus influenzae, Group B streptococcus/ E. coli, Listeria
Common pathogens that cause CNS/Meningitis infection
streptococcus pyogenes, streptococcus pneumoniae, haemophilus influenzae, moraxella catarrhalis
Common pathogens that cause upper respiratory infections
staphylococcus aureus (including MRSA), staphyloccus epidermidis, streptococci, enterococci
Common pathogens that cause heart/endocarditis infections.
staphylococcus aureus, staphylococcus epidermidis, streptococcus pyogenes, pasteurella multocida, + aerobic/anaerobic GNR (in diabetes)
Common pathogens that cause skin and soft tissue infections.
staphylococcus aureus, staphylococcus epidermidis, streptococci, neisseria gonorrhoeae, GNR (in specific situations)
Common pathogens that cause bone/joint infections.
mouth flora (peptostreptococcus), anaerobic gram negative rods, (prevotella, others), Viridans group streptococci
Common pathogens that cause mouth infections.
streptococcus pneumoniae, haemophilus influenzae, atypicals (legionella, mycoplasma, chlamydophila), enteric gram negative rods (alcohol use disorder)
Common pathogens that cause lower respiratory (community) infections
staphylococcus areus (including MRSA), pseudomonas aeruginosa, acinetobacter baumannii, enteric gram negative rods (including ESBL +, Multi drug resistant), streptococcus pneumoniae
common pathogens that cause lower respiratory (hospital) infections
enteric GNR, enterococci, streptococci, bacteroides species
Common pathogens causing intra-abdominal infections.
E. coli, proteus, Klebsiella, staphylococcus saprolyticus, enterococci
Common pathogens causing urinary tract infections.
Proteus, E coli, Klebsiella, enterobacter, serratia
enteric gram negative rods
empiric treatment
usually broad spectrum (covers several types of bacteria) and can be guided by local resistance patterns (antibiogram)
gram positive organisms
have a thick cell wall and stain dark purple or blue from the crystal violet stain
gram negative organisms
have a thin cell wall and take up the safranin counterstain resulting in a pink color
atypical organisms
do not have a cell wall and do not stain well
staphylococcus spp (MSSA/MRSA)
gram positive cocci- clusters
streptoccoccus pneumoniae (diplococci), streptococcus spp. (including strep pyogenes), enterococcus spp. (including VRE)
gram positive cocci- pairs and chains
listeria, monocytogenes, corynebacterium spp.
gram positive rods
peptostreptococcus, propionibacterium acnes, clostridium difficile, clostridium spp.
gram positive anaerobes
neisseria spp.
gram negative cocci
proteus mirabilis, E coli, klebsiella spp., serratia spp., enterobacter cloacae, citrobacter spp.
gram negative rods that colonize in the gut (enteric)
H pylori, campylobacter spp. , treponema spp., borrelia spp., leptospira spp.
curved or spiral shaped gram negative rods
pseudomonas aeruginosa, haemophilus influenzae, providencia spp
gram negative rods that do not colonize in the gut
acinetobacter baumannii, bordetella pertussis, moraxella catarrhalis
gram negative coccobacilli
bacteroides fragilis, prevotella spp.
gram negative anaerobes
staph aureus
stahpylococcus species that is coagulase positive
minimum inhibitory concentration
minimum concentration of each antibiotic that inhibits bacterial growth
aminoglycosides + beta lactams: beta lactam breaks down cell wall and aminoglycoside reaches intracellular target at safe doses
synergistic treatment for certain invasive gram positive infections such as infective endocarditis
intrinsic resistance
resistance is natural to the organism (E coli is resistant to vancomycin because this antibiotic is too large to penetrate the cell wall of E coli.)
selection pressure
resistance occurs when antibiotics kill susceptible bacteria, leaving behind more resistant strains to multiply. (normal GI flora includes enterococcus; when abx eliminate susceptible enterococci, VRE can become predominant.)
acquired resistance
bacterial DNA containing resistant genes can be transferred between species and/or picked up from dead bacterial fragments in the environment
antibiotic degradation
bacterial enzymes break down the antibiotic (beta lactamases)
Klebsiella pneumoniae (ESBL, CRE)
E coli (ESBL, CRE)
Aceinetobacter baumannii
Enterococcus faecalis, enterococcus faecium (VRE)
Staph aureus (MRSA)
Pseudomonas aeruginosa
*Kill Each And Every Strong Pathogen*
Common Resistant Pathogen
clostridium difficile
when an antibiotic kills GI flora along with the targeted pathogen it can result in an overgrowth of _____________, which can produce toxins that inflame the GI mucosa
mild (loose stools to abdominal cramping) to severe (pseudomonas colitis that can require a colectomy or be fatal) symptoms
symptoms of c. diff
broad spectrum penicillins and cephalosporins, quinolones, carbapenems, and clindamycin
antibiotics with the highest risk of c.diff infection
folic acid synthesis inhibitors
sulfonamides, trimethoprim (often combined with sulfamethoxazole to overcome resistance), dapsone
cell wall inhibitors
beta lactams, monobactams (aztreonam), vancomycin, dalbavancin, telavancin, oritavancin
protein synthesis inhibitors
aminoglycosides, macrolides, tetracyclines, clindamycin, linezolid, tedizolid
cell membrane inhibitors
polymixins, daptomycin, televancin, oritavancin
DNA/RNA inhibitors
quinolones (DNA gyrase, topoisomerase IV), metronidazole, tinidazole, rifampin)
aminoglycosides, quinolones, daptomycin
concentration dependent abx
vancomycin, macrolides, tetracyclines, polymyxins
exposure dependent abx
beta lactams
time dependent abx