Infectious Diseases - MTB Flashcards
B-lactam antibiotics
- Penicillins
- Cephalosporins
- Cabapenems
- Aztreonam
Penicillin: coverage
- Strep viridins
- S. pyogenes
- Oral anaerobes
- Syphillis
- Leptospira
Ampicillin and amoxicillin: coverage
- Penicillin bugs (S. viridins, S. pyogenes, Oral anaerobes, syphillis, leptospira)
- E.coli
- Lyme disease
- Gram- negative bacilli
Amoxillin coverage
HELPS
- H. influenzae
- E.coli
- Listeria
- Proteus
- Salmonella
Penicillin is the best initial therapy for?
- Otitis media
- Dental infection and endocarditis prophylaxis
- Lyme disease limited to rash, joint, and CN VII
- UTI
- Listeria monocytogenes
- Enterococcus infections
Penicillinase- resistant penicillins
- Oxacillin
- Cloxacillin
- Dicloxacillin
- Nafcillin
Penicilinase-resistant penicillins: Treatment
Skin infxns: cellulitis, impetigo, erysipelas
Endocarditis: Meningitis and Staph bacteriemia
Osteomyelitis and Septic arthritis
Not active against MRSA
Why is methicillin never the right answer?
Causes renal failure from allergic interstitial nephritis
- really means oxacillin sensitive or resistant
Penicillin drugs that cover gram negative bacilli (E.coli and Proteus) and pseudomonas
- Piperacillin
- Ticarcillin
- Alzlocillin
- Mezlocillin
Piperacillin, Ticarcillin, Alzocillin, Mezlocillin: best initial therapy for
- Cholecystitis and ascending cholangitis
- Pyelonephritis
- Bacteremia
- Hospital acquired and ventilator associated pneumonia
- Neutropenia and fever
Which organisms are resistant to all forms of cephalosporins?
- Listeria
- MRSA
- Enteroccocus
All cephalosporins cover will organisms
- Group A Strep
- Group B Strep
- Group C Strep
- Strep viridins
- E. coli
- Klebsiella
- Proteus mirabilis
If pt complains of a rash when he takes penicillin?
Cephalosporins
If patient complains of anaphylaxis when he takes penicillin? Next step?
Non B-lactam antibiotic
1st generation cephalosporins: treatment
- Staphylococci: METHICILLIN SENSITIVE = OXACILLIN SENSITIVE = CEPHALOSPORIN SENSITIVE
- Streptococci (except Enterococcus)
- Some gram (-) bacillin: E. coli NOT Pseudomonas
- Osteomyelitis, septic arthritis, endocarditis, cellulitis
1st generation cephalosporins
- Cefazolin
- Cephalexin
- Cephradrine
- Cefadroxyl
2nd generation cephalosporins
- Cefotetan
- Cefoxitin
- Cefaclor
- Cefprozil
- Cefuroxime
- Loracarbef
2nd generation cephalosporin: coverage
Skin: MSSA = oxacillin sensitive = cephalosporin sensitive
Streptococci (except Enterococcus)
Gram (-) bacilli
Anaerobes
Osteomyelitis, Septic arthritis, Endocarditis, Cellulitis
When is cefotetan or cefoxitin the best initial therapy?
Pelvic inflammatory disease (PID) combined with doxycycline
Cefotetan and cefoxitin: adverse effects
Increase risk of bleeding and give disulfiramlike reaction w/ alcohol
When is cefuroxime, loracarbef, cefprozil, cefaclor the best initial therapy?
Respiratory infections such as bronchitis, otitis media, and sinusitis
3rd generation cephalosporins
- Ceftriaxone
- Cefotaxime
- Ceftazidime
Ceftriaxone
- 3rd generation cephalosporin
1st line for pneumoccocus - treats meningitis, CAP (w. macrolides)
- Lyme involving the heart or brain
Why do you avoid ceftriaxone in neonates?
Impaired biliary metabolism
Cefotaxime: uses
- superior to ceftriaxone in neonates
- spontaneous bacterial peritonitis
Ceftazidime coverage
Pseudomonal coverage
Ceftaroline
- 1st cephalosporin to cover MRSA
4th generation cephalosporin
Cefepime
Cefepime
- 4th generation cephalosporin
- has better Staph coverage compared to 3rd gen cephalosporins
- used to treat neutropenia and fever
- ventilator associated pneumonia
Cefoxitin and cefotetan: adverse effects
Deplete prothrombin and increase risk of bleeding
Carbapenems
Imipenem
Meropenem
Ertapenem
Doripenem
Carbapenems: mechanism of action
inhibit cell wall synthesis by binding to penicillin binding proteins
Carbapenem coverage
Gram (-) bacilli, including many that are resistant, anaerobes, streptococci, and staphylococci
- used to treat neutropenia and fever
How does ertapenem differs from other carbapenems?
- does not cover Pseudomonas
Aztreonam
- only drug in the class of monobactams
- exclusively for gram- negative bacilli including Pseudomonas
- no cross reaction w/ penicillin
Fluoroquinolones
- block DNA topoisomerases
- Ciprofloxacin
- Gemifloxacin
- Levofloxacin
- Moxifloxacin
Best therapy for community acquired pneumonia, including penicillin-resistant pneumococcus
Fluoroquinolones (e.g ciprofloxacin, gemifloxacin, levofloxacin, moxifloxacin)
Fluoroquinolones: uses
- gram negative rods for urinary and GI tracts (including Pseudomonas)
- best tx for CAP
- Neisseria
- Some gram positive organisms
Fluoroquinolone: treatment uses
- Diverticulitis and GI infxns (must be combined w metronidazole) b/c they don’t cover anaerobes
- MOXIFLOXACIN can be used as single agent for diverticulitis and doesn’t need metronidazole
- CIPROFLOXACIN for cystitis and pyelonephritis
Fluoroquinolones: adverse effects
- BONE GROWTH ABNORMALITIES: in children and pregnant women
- TENDONITIS and Achilles tendon rupture
- Gatifloxacin removed b/c glucose abnormalities
Aminoglycosides
Gentamicin, Tobramycin, Amikacin
- inhibit formation of initiation complex and cause misreading of mRNA
- require oxygen for uptake thus ineffective w/ anaerobes
Aminoglycoside coverage
- gram (-) bacilli (urine, bowel, bacteremia)
- synergistic w/ B-lactam antibiotics for enterococci and staphylococci
- not effective against anaerobes since need to oxygen to work
- NEPHROTOXIC AND OTOTOXIC
Doxycycline
Bacteriostatic: bind to 30S and prevent attachment to aminoacyl-tRNA
- fecally eliminated and can be used in patients w/ renal failure
Doxycycline
- Chlamydia
- Lyme disease limited to rash, joint or CN VII palsy
- Ricksettia
- MRSA of skin and soft tissue
- Primary and secondary syphillis in those allergic to penicillin
- Borrelia, Ehrlichia, and Mycoplasma
Doxycycline: adverse effects
- Tooth discoloration (children)
- Fanconi syndrome (type II RTA proximal)
- Photosensitivity
- Esophagitis/ulcer
Nitrofurantoin : indication
Cystitis especially in pregnant women
Trimethoprim/Sulfamethoxazole
- Cystitis
- Pneumocystis pneumonia treatment and prophylaxis
- MRSA of skin and soft tissue (cellulitis)
Trimethoprim/Suldamethoxazole: adverse effects
- Rash
- Hemolysis (with G6PD deficiency)
- Bone marrow suppression (b/c folate antagonist)
Beta-lactam/B-lactamase combinations
- Amoxicillin/clavulanate
- Ticarcillin/ clavulanate
- Ampicillin/ Sulbactam
- Piperacillin/Tazobactam
Beta-lactamase coverage
- against sensitive staphylococci to these agents
- cover anaerobes
- first choice for mouth and GI abscess
Best initial therapy for gram positive cocci
- Oxacillin, Cloxacillin, Dicloxacillin, Nafcillin
- 1st gen cephalosporins: cefazolin, cephalexin
- Fluoroquinolones
- Macrolides (e.g. azithromycin, erythromycin) - 3rd line
Oxacillin (Methicillin-Resistant) Staphylococcus
Best treated with:
- vancomycin
- linezolid: reversible bone marrow toxicity
- daptomycin: elevated CPK
- tigecycline
- ceftraroline
Minor MRSA infections of skin are treated w/
- TMP/SMX
- Clindamycin
- Doxycycline
- Linezolid
Anaerobes
Oral (above diaphragm)
- Penicillin (G, VK, ampicillin, amoxicillin)
- Clindamycin
Abdominal/ gastrointestinal
- Metronidazole, beta-lactam/lactamase combinations
Gram Negative Bacilli
e.g. E.coli, Klebsiella, Proteus, Pseudomonas, Enterobacter, Citrobacter
- cause infections of bowel (peritonitis, diverticulitis)
- urinary tract (pyelonephritis)
- liver (cholecystis, cholangitis)
Gram- negative bacilli: treatment
- Quinolones
- Aminoglycosides
- Carbapenems
- Piperacillin, Ticarcillin
- Aztreonam
- Cephalosporins
Most appropriate tx for E.coli bacteremia.
- Quinolones
- Aminoglycoside
- Carbapenems
- Piperacillin, Ticarcillin
- Aztreonam
- Cephalosporin
Pt presents w/ fever, stiff neck, photophobia, meningismus. Likely dx?
Meningitis
Pt presents with fever and confusion. Likely dx?
Encephalitis
Pt presents with fever and focal neurological findings. Likely dx?
Abscess
Meningitis
- infection or inflammation of covering or meninges of CNS
Common causes of meningitis
- S. pneumonia (60%)
- Group B Strep (14%)
- Haemophilus influenzae (7%)
- N. meningitides (15%)
- Listeria (2)
Meninigitis bug associated with neurosurgery
S. aureus
Meningitis: presentation
- Fever, headache, neck stiffness (nuchal rigidity) and photophobia
Meningitis with AIDS patient < 100 CD4 cells. Likely organism?
Cryptococcus
Meningitis with camper/hiker, rash shaped like target, joint pain, facial palsy, tick remembered in 20%. Likely organism?
Lyme disease
Meningitis w/ camper/hiker, rash moves from arms/legs to trunk, tick remembered in 60%. Likely organism?
Rocky Mountain spotted fever (Ricksettia)
Meningitis w/ pulmonary TB in 85%. Likely organism?
Tuberculosis
Meningitis with no presentation.
Viral
Meningitis in adolescent with petechial rash. Likely organism?
Neisseria
Best initial and most accurate test for meningitis
Lumbar puncture
Bacterial meningitis: CSF
- 1000s, neutrophils
- elevated protein
- decreased glucose
- stain: 50 - 70%
- culture: 90%
Cryptococcus, Lyme, Ricksettia: CSF
- 10s - 100s lymphocytes
- possibly elevated protein
- possibly decreased glucose
- negative stain and culture
Tubercolosis: CSF
- 10s - 100s lymphocytes
- markedly elevated protein
- may be low glucose
- negative stain and culture
Viral meningitis: CSF
- 10s - 100s lymphocytes
- usually normal protein
- usually normal glucose
- negative stain and culture
When is head CT the best initial test for meningitis?
Head CT prior to an LP only if there is the possibility that a space occupying lesion may cause herniation
Head CT first when any of the following present:
- Papilledema (blurred, fuzzy disc margin from intracranial pressure)
- Seizures
- Focal neurological abnormalities
- Confusion interfering w/ neuro examination
If there is a contraindication to immediate LP in meningitis patients, what’s the next step?
Antibiotics
Bacterial Antigen Detection (Latex Agglutination Tests)
- similar to gram stain
- antigen detection methods are positive, they are specific
- if antigen detection methods are negative, person could still have infecition
When is a bacterial antigen test indicated?
Pt has received antibiotic prior to LP and culture may be falsely negative
What is the most accurate test for TB meningitis
- Acid fast stain and cx on 3 high volume LP
- centrifuge the specimen to concentrate the organisms
- has highest CSF protein level
Most accurate for Lyme and Rickettsia meningitis?
Specific serologic testing
ELISA
Western blot
PCR
Most accurate test for cryptococcus meningitis
India ink (60 - 70% sensitive) Cryptococcal antigen is more than 95% and specific
Most accurate test for viral meningitis
Generally a diagnosis of exclusion
Best initial treatment for bacterial meningitis
- Ceftriaxone, vancomycin, and steroids
- base your treatment answer on cell count*
- *** Gram stain is good if positive, protein and glucose levels are too nonspecific **
Thousands of neutrophils on CSF. Tx?
Ceftriaxone, Vancomycin, and Steroids
- add ampicillin if immunocompromised for Listeria
Listeria monocytogenes
- resistant to all cephalosporins but sensitive to penicillins
- add ampicillin to ceftriaxone and vancomycin if case describes risk factors for Listeria
Risk factors for Listeria monocytogenes
- Elderly
- Neonates
- Steroid use
- AIDS or HIV
- Immunocompromised
- Pregnant
Neisseria meningitides: Additional management
- ceftriaxone
- respiratory isolation
- rifampin, ciprofloxacin, or ceftriaxone to close contacts (household contacts, kissing, or sharing cigarettes, or eating) to decrease nasopharyngeal carriage
Man comes to ED with fever, severe headache, neck stiffness and photophobia. On exam, he is found to have weakness of is left arm and leg. Most appropriate next step in management of patient?
Ceftriaxone, vancomycin, and steroids
Most common neuro deficit of untreated bacterial meningitis
Eighth cranial nerve deficit or deafness
Encephalitis
- acute onset of fever and confusion
- herpes simplex is by far the most common cause
- must do head CT first b/c of presence of confusion
Most accurate test for herpes encephalitis?
PCR of CSF
** blood serology from routine cold sore, genital herpes, or encephaltis**
Encephalitis: Treatment
Acyclovir - best initial therapy for herpes encephalitis
** Foscarnet used in acyclovir-resistant herpes**
Woman is admitted for herpes enecephalitis confirmed by PCR. After 4 days of acyclovir her creatinine level begins to rise. Most appropriate next step in management?
Reduce the dose of acyclovir and hydrate
– can’t use foscarnet because has more renal toxicity
Otitis Media
- presents with redness, immobility, bulging, and decreased light reflex of tympanic membrane
- pain is common
- decreased hearing and fever also occur
Most sensitive physical finding for otitis media?
Immobility
- fully mobile TM essentially excludes otitis media
Otitis Media: Diagnostic Tests
- Tympanocentesis - if there are multiple recurrents or if no response to multiple abx
Otitis Media: Treatment
Amoxicillin (best initial therapy)
If patient w/ otitis media doesn’t respond to amoxicillin, what’s the next best therapy?
- Amoxicillin/ clavulanate
- Azithromycin, clarithromycin
- Cefuroxime, loracabef
- Levofloxacin, gemifloxacin, moxifloxacin
34 y/o women presents w/ facial pain, discolored nasal discharge, bad taste in mouth, and fever. On physical exam, she has facial tenderness. Which of the following is most accurate diagnostic tests?
Sinus biopsy or aspirate
- need microbiological diagnosis for treatment
- ** never culture nasal discharge **