initial therapy - mc microb - antib

Question 1

Meningitis, bacterial,

community-acquired

Answer 1

Streptococcus pneumoniae
(pneumococcus),1 Neisseria
meningitidis
(meningococcus)

Cefotaxime,2 2–3 g intravenously every 6 hours or ceftriaxone, 2 g
intravenously every 12 hours; plus vancomycin, 15 mg/kg intravenously
every 8 hours

Question 2

Meningitis, bacterial, age > 50,

community-acquired

Answer 2

Pneumococcus, meningococcus,
Listeria monocytogenes,3
gram-negative bacilli, group B
streptococcus

Ampicillin, 2 g intravenously every 4 hours, plus cefotaxime, 2–3 g
intravenously every 6 hours or ceftriaxone, 2 g intravenously
every 12 hours, plus vancomycin, 15 mg/kg intravenously every
8 hours

Question 3

Meningitis, postoperative

(or posttraumatic)4

Answer 3

S aureus, gram-negative bacilli,
coagulase-negative staphylococci,
diphtheroids (eg, Propionibacterium
acnes)
(uncommon) pneumococcus
(in posttraumatic)
Vancomycin4, 15 mg/kg intravenously every 8 hours, plus cefepime,
3 g intravenously every 8 hours

Question 4

Brain abscess Mixed anaerobes, pneumococci,

streptococci

Answer 4

Penicillin G, 4 million units intravenously every 4 hours, plus metronidazole,
500 mg orally every 8 hours; or cefotaxime, 2–3 g intravenously
every 6 hours or ceftriaxone, 2 g intravenously every
12 hours plus metronidazole, 500 mg orally every 8 hours

Question 5

Pneumonia, acute, communityacquired,
non-ICU hospital
admission

Answer 5

Pneumococci, M pneumoniae,
Legionella, C pneumoniae
Cefotaxime, 2 g intravenously every 8 hours (or ceftriaxone, 1 g
intravenously every 24 hours or ampicillin 2 g intravenously every
6 hours) plus azithromycin 500 mg intravenously every 24 hours;
or a fluoroquinolone5 alone

Question 6

Endocarditis, acute (including

injection drug user)

Answer 6

S aureus, E faecalis, gram-negative
aerobic bacteria,	
viridans streptococci
Vancomycin, 15 mg/kg intravenously every 12 hours, plus gentamicin,
1 mg/kg every 8 hours

Question 7

Septic thrombophlebitis eg, IV tubing, IV shunts)

Answer 7

S aureus, gram-negative aerobic
bacteria
Vancomycin, 15 mg/kg intravenously every 12 hours, plus ceftriaxone,
1 g intravenously every 24 hours

Question 8

Osteomyelitis

Answer 8

S aureus Nafcillin, 2 g intravenously every 4 hours; or cefazolin, 2 g intravenously
every 8 hours

Question 9

Septic arthritis

Answer 9

S aureus, N gonorrhoeae Ceftriaxone, 1–2 g intravenously every 24 hours

Question 10

Pyelonephritis with flank pain and
fever (recurrent urinary tract
infection

Answer 10

E coli, Klebsiella, Enterobacter,
Pseudomonas
Ceftriaxone, 1 g intravenously every 24 hours; or ciprofloxacin,
400 mg intravenously every 12 hours (500 mg orally); or levofloxacin,
500 mg once daily (intravenously/orally)

Question 11

Fever in neutropenic patient

receiving cancer chemotherapy

Answer 11

S aureus, Pseudomonas,
Klebsiella,
E coli
Ceftazidime, 2 g intravenously every 8 hours; or cefepime, 2 g intravenously
every 8 hours

Question 12

Intra-abdominal sepsis (eg, postoperative,
peritonitis,
cholecystitis)

Answer 12

Gram-negative bacteria,
Bacteroides,
anaerobic
bacteria,
streptococci,
clostridia
Piperacillin-tazobactam, 4.5 g intravenously every 6 hours, or
ertapenem, 1 g every 24 hours

Question 13

Erysipelas, impetigo,
cellulitis,
ascending
lymphangitis

Answer 13

Group A streptococcus Phenoxymethyl penicillin,
0.5 g orally four times daily
for 7–10 days
Cephalexin, 0.5 g orally four times daily for
7–10 days; or azithromycin, 500 mg on
day 1 and 250 mg on days 2–5

Question 14

Furuncle with
surrounding
cellulitis

Answer 14

Staphylococcus aureus Dicloxacillin, 0.5 g orally four times
daily for 7–10 days for MSSA.
However, in many areas of the
United States, CA-MRSA has
become predominant; TMP-SMZ
two double-strength tablets
twice daily for 7–10 days; or
clindamycin 0.3 g orally four
times daily for 7–10 days
Cephalexin, 0.5 g orally four times daily for
7–10 days for MSSA. For CA-MRSA, tetracyclines,
but not fluoroquinolones, are
reasonable alternatives

Question 15

Pharyngitis

Answer 15

Group A streptococcus Phenoxymethyl penicillin, 0.5 g
orally four times daily, or amoxicillin,
0.5–1 g orally three times
daily, for 10 days
For patients with history of non-anaphylactic
penicillin allergy, cephalexin, 0.5 g orally
four times daily for 10 days; for patients
with more severe penicillin allergy,
clindamycin, 300 mg orally four times
daily for 10 days; or azithromycin, 500 mg
on day 1 and 250 mg on days 2–5; or clarithromycin
or azithromycin for susceptible
isolates

Question 16

Otitis media

Answer 16

Streptococcus pneumoniae,
Haemophilus influenzae,
Moraxella catarrhalis
Amoxicillin, 0.5–1 g orally
three times daily for 10 days
Augmentin,2 0.875 g orally twice daily;
or cefuroxime, 0.5 g orally twice daily;
or cefpodoxime,
0.2–0.4 g daily; or doxycycline,
100 mg twice daily; or TMP-SMZ,1
one double-strength tablet twice daily
(all regimens for 10 days)

Question 17

Acute sinusitis

Answer 17

S pneumoniae,
H influenzae,
M catarrhalis
Augmentin,2 0.875 g orally
twice daily,
For patients allergic to penicillin, doxycycline,
100 mg twice daily for 10 days, or
some fluoroquinolones5 can be considered.
Due to increasing resistance among
pneumococci, monotherapy with a macrolide,
a cephalosporin, or TMP-SMZ is not
recommended

Question 18

Aspiration

pneumonia

Answer 18

Mixed oropharyngeal flora,
including anaerobes
Clindamycin, 0.3 g orally four
times daily for 10–14 days
Phenoxymethyl penicillin, 0.5 g orally four
times daily for 10–14 days

Question 19

Pneumonia

Answer 19

S pneumoniae, Mycoplasma
pneumoniae,
Legionella pneumophila,
Chlamydophila
pneumoniae
Doxycycline, 100 mg orally twice
daily, or azithromycin (erythromycin,
clarithromycin), 0.5 g
orally on day 1 and 0.25 g on
days 2–5
Amoxicillin, 0.5–1.0 g orally three times daily.
Due to increasing resistance to doxycycline
and macrolides among pneumococci,
a fluoroquinolone5 for 10–14 days
(or doxycycline plus amoxicillin)

Question 20

Cystitis

Answer 20

Escherichia coli, Staphylococcus
saprophyticus,
Klebsiella pneumoniae,
Proteus species, other
gram-negative rods or
enterococci
Nitrofurantoin monohydrate macrocrystals
100 mg twice daily for
5–7 days (unless pregnant); fosfomycin
3 g orally as a single dose
Cephalexin, 0.5 g orally four times daily
for 7 days, for uncomplicated cystitis.
Due to increasing resistance, TMP-SMZ
and fluoroquinolones should not be used
as first-line therapy for empiric treatment

Question 21

Pyelonephritis

Answer 21

E coli, K pneumoniae,
Proteus species,
S saprophyticus
Fluoroquinolones4 for 7 days if prevalence
of resistance among uropathogens
is

Question 22

Gastroenteritis

Answer 22

Salmonella, Shigella,
Campylobacter,
Entamoeba histolytica
3The diagnosis should be confirmed by culture before therapy. Salmonella gastroenteritis does not require therapy. For susceptible Shigella
isolates, give ciprofloxacin, 0.5 g orally twice daily for 5 days; or TMP-SMZ double-strength tablets twice daily for 5 days; or ampicillin, 0.5 g
orally four times daily for 5 days. For Campylobacter infection, give azithromycin, 1 g orally times one dose, or ciprofloxacin, 0.5 g orally twice
daily for 5 days. For E histolytica infection, give metronidazole, 750 mg orally three times daily for 5–10 days, followed by diiodohydroxyquinoline,
600 mg orally three times daily for 3 weeks.

Question 23

Urethritis,

epididymitis

Answer 23

Neisseria gonorrhoeae,
Chlamydia trachomatis
Ceftriaxone, 250 mg intramuscularly
once plus azithromycin (or doxycycline)
for N gonorrhoeae;
azithromycin 1 g orally once, or
doxycycline, 100 mg orally twice
daily for 7 days, for C trachomatis
Cefixime 400 mg orally once for
N gonorrhoeae6

Question 24

Pelvic inflammatory

disease

Answer 24

N gonorrhoeae,
C trachomatis, anaerobes,
gram-negative rods
Levofloxacin 500 mg orally daily,
or ofloxacin, 400 mg orally twice
daily, for 14 days, plus metronidazole,
500 mg orally twice daily, for
14 days
Cefoxitin, 2 g intramuscularly, with probenecid,
1 g orally, followed by doxycycline,
100 mg orally twice daily for 14 days;
or ceftriaxone, 250 mg intramuscularly
once, followed by doxycycline, 100 mg
orally twice daily for 14 days

Question 25

syphilis

Answer 25

Early syphilis (primary,
secondary,
or latent of
 1
year’s duration or
cardiovascular
syphilis
T pallidum Benzathine penicillin G, 2.4 million
units intramuscularly once a week
for 3 weeks (total: 7.2 million
units)
Doxycycline, 100 mg orally twice daily,
for 4 weeks

Neurosyphilis T pallidum Aqueous penicillin G, 12–24 million
units/day intravenously
for 10–14 days