Infectious Diseases I: Background and antibiotics by drug class

-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