Classifications of drugs and normal flora Flashcards
3 primary ways to classify antimicrobial drugs
- susceptible organism
- MOA
- drug inhibits bacterial growth (bacteriostatic), or if it is lethal to cells (bacteriocidal)
Narrow vs. broad spectrum
narrow: active only against few microorganisms
broad: active against a wide variety
MOAs
Disruption of bacterial cell wall: penicillins, cephalosporins -> act to weaken cell wall and thereby promote cell lysis
inhibition of enzyme: sulfonamide drugs suppress bacterial growth by inhibiting enzyme required to produce folic acid from PABA.
Disruption of bacterial protein synthesis: disrupt function of bacterial ribosomes
Inhibition of bacterial nucleic acid synthesis
Inhibitors of cell wall synthesis
B-lactam abx: penicilllins, cephalosporins, carbapenems, monobactams
- clavulanic acid, sulbactam, taxobactam
Protein synthesis inhibitors: 30s subunit
Aminoglycosides: gentamicin, tobramycin, amikacin
Tetracyclines: tetracycline, doxycycline, minocycline
Protein synthesis inhibitors: 50s subunit
macrolides: erythromycin, clarithromycin, azithromycin
others: chloramphenicol, clindamycin, linezolid, streptogramins
DNA synthesis inhibitors
Fluoroquinolones: cipro, oflaxacin, norfloxacin, levofloxacin, gatiflocacin, moxifloxacin
Metronidazole
RNA synthesis inhibitors
Rifampin
Mycelia acid synthesis inhibitors
isoniazid
Folic acid synthesis inhibitors
sulfonamides, trimethoprim
Function of normal flora
GI tract: aids in digestion
mucous membranes: mucosal immunity
in general: protects host from colonization with pathogenic microbes
What are opportunistic pathogens?
cause disease when immune defenses are altered,
when they change their usual anatomic location
-the blood, brain, muscle and CSF are normally free of flora
Normal flora of the oral cavity
streptococci viridans Lactobacilli Staph (aureus and epidermidis) corynebacterium sp. bacteroides sp. streptococcus sanguis streptococcus mutans actinomyces sp.
Normal flora of the nose
staphylococcus epidermidis corynebacteria staph aureus Neisseria sp.* Haemphilus sp* strep pneumoniae*
Normal flora of the nasopharynx
non-hemolytic strep alpha-hemolytic strep Neisseria sp. strep pneumoniae strep pyogenes H. influenzae Neisseria meningitidis
Normal flora of lower resp. tract
usually sterile
individual becomes infected by the pathogen descending from the nasopharynx (H. influenzae, and S. pneumoniae)
Normal flora of external ear
staph epidermidis
staph aureus
corynebacterium sp.
Normal flora of GI tract
Enterobacteriaceae enterococci bacteroides staph lactobacilli clostridia
Normal flora of GU tract
staph epidermidis enterococcus faeccalis Alpha-hemolytic strep E coli proteus corynebaceria sp. acinetobacter sp. mycoplasma sp. candida sp mycobacterium smegmatis
Normal vaginal flora
corynebacterium sp. staph nonpyogenic strep (Group B) E coli lactobaciluus acidophilus flavobacterium sp. clostridium sp. viridans strep other enterobacteria
causative organisms of endocarditis and tx
native valve: sterp viridans -> Pen G or Amp+Nafcillin
IV drug user: MSSA, MRSA -> vanco
Prosthetic valve: S. epi, S. aureus, S. viridans -> vanco+rifampin+gentamicin
causative organisms of intra-abdominal infections
Diverticulitis, perirectal abscess, peritonitis-> E. coli, p. aeruginosa, enterococci
tx: TMP-SMX-DS or cipro, or levofloxacin+ metronidazole (outpt)
Skin and soft tissue causative agents
gen. cellulits: staph aureus, strep-> MSSA: cephalexin, MRSA: TMP-SMX-DS or clindamycin
strep: cephalexin
diabetic ulcer: staph, strep or pyogenes-> Doxy or TMP-SMX-DS or clindamycin
Animal bites -> cat: amox-clav (augmentin)
Necrotizing fasciitis: GABS, C. perfringens -> PCN G, cefoxitin, chloramphenicol, clindamycin, metronidazole
Urinary tract causative agents
E. coli, gram - aerobic bacilli, enterococcus, staph saprophyticus -> TMP-SMX-DS
if resistance is >20% to TMP -> use cipro, levo, moxi
Respiratory tract infections (pneumonias)
Aspiration pneumonia: anaerobic or aerobic -> clindamycin or ampicillin-sulbactam or A carbapenem
Lower/hosp acquired: pseudomonas aeruginosa, gram - aerobic bacilli -> imipenem -cilastatin or meropenem + cipro if suspect pseudo
Hx of HIV: pneuomocystis carinii, S. pneumoniae -> Trimethoprim-sulfamethoxazole (Bactrim, Septra)
Respiratory tract causative agents
sinusitis: S. pneumo, H. influenzae, M. catarrhalis, S. auerus, Grp A strep –> peds: amox or amox-clav, pcn allergy: clinda
adult: amox-clav, pcn allergy: levo or doxy
Community acquired pneumonia: all same as sinusitis plus klebsiella, mycoplasma, chlaymdia -> azithro, clarithro, doxycycline
meningitis in kids
child ampicillin + gentamicin
child 2 months - 12 years: strep pneuma, N. meningitis, H. influenza -> vanco + cerfriaxone
Meningitis
1 mo -> 50 years: S. pneumoniae, meningococci: cefotaxime or ceftriaxone+ vanco
amp+cefotaxime or gentamycin
Prophylactic antibiotics b/f surgery
should be admin. before surgery begins via IV
- often used to irrigate surgical site as well
- Cefazolon (Ancef) 30 minutes before incision
for pcn allergies: use vanco
who is at risk at developing endocarditis?
prosthetic heart valves
congenital heart disease
prophylaxis for endocarditis
30-60 minutes prior to dental procedures: amoxicillin 2 gm PO
if PCN allergy: clinda, azithro, clarithro
Complications of antibiotic therapy
toxicity C. diff alt of gut flora and change of Vit K levels leading to difficulty managing warfarin therapy candida overgrowth serious side effects
C diff diarrhea
can be life threatening, sever inflammation of colon, may lead to colectomy, highly contagious
Drugs most likely to cause C. diff
Most frequent: Ampicillin/amoxicillin cephalosporins clindamycin quinolones
