Bacteriology and Organisms + Treatments

(all first line)

Folliculitis

Staphylococcus aureus (MSSA)

Topical Mupirocin

Hot Tub Folliculitis

Pseudomonas aeruginosa

Self-limited (5-10 days)

Furuncle (Boil)

Staphylococcus aureus (MSSA/MRSA)

I&D (+ warm compresses)

Carbuncle

Staphylococcus aureus (MRSA)

I&D

Cellulitis

Streptococcus pyogenes (GAS) + Staphylococcus aureus (MSSA)

Cephalexin

Erysipelas

Streptococcus pyogenes (GAS)

Penicillin VK or Amoxicillin

Necrotizing Soft Tissue Infection (“Nec Fasc”)

Streptococcus pyogenes (GAS) ± Polymicrobial (anaerobes, gram-negatives

Emergent Surgical Debridement + Broad Spectrum IV Antibiotics (Vancomycin + Piperacillin/Tazobactam)

Gas Gangrene

Clostridium perfringens (anaerobic)

Emergent surgical debridement + IV Penicillin G + Clindamycin

Osteomyelitis

Staphylococcus aureus (MSSA > MRSA)

Antistaphylococcal therapy:

• Naficillin or Oxacillin (IV)

Septic Arthritis

Staphylococcus aureus (MSSA > MRSA), Neisseria Gonorrhoeae (young, sexually active)

Nafcillin or Oxacillin (IV) + Arthroscopic or open drainage and washout

Infective Endocarditis (due to Staphylococcus aureus (MC))

Nafcillin/Oxacillin (IV) or Cefazolin (for MSSA)

Infective Endocarditis (due to Viridians Group Streptococci)

Penicillin G (IV) or Ceftriaxone (IV)

Infective Endocarditis (due to Enterococcus species)

Ampicillin (IV) + Ceftriaxone (IV)

Infective Endocarditis (due to HAECK group)

Ceftriaxone (IV)

Infective Endocarditis (Culture Negative)

Coxiella, Bartonella, Brucella, Fungi

Directed therapy based on suspected pathogen

Toxic Shock Syndrome (TSS)

Staphylococcus aureus

• Clindamycin (IV) + Vancomycin (IV)

• Supportive care (fluids, vasopressors)

Scarlet Fever

Streptococcus pyogenes

Penicillin V (PO) (or Amoxicillin PO)S

Staphylococcal Scalded Skin Syndrome

Staphylococcus aureus

Nafcillin or Oxacillin IV

Diptheria

Corynebacterium diphtheriae

Diphtheria antitoxin (DAT) V + Penicillin G IV (or Erythromycin IV)

Tetanus

Clostridium tetani

Tetanus immune globulin (TIG) IM + Metronidazole IV + Supportive care

Cholera

Vibrio cholerae

Aggressive rehydration (oral or IV) + Doxycycline PO (or Azithromycin PO)

Staphylococcal Food Poisoning

Staphylococcus aureus

Supportive care

• oral/IV fluids

• Antiemetics

• No antibiotics needed

Botulism

Clostrium botulinum

Botulinum Antitoxin (IV) ASAP + Supportive Care (especially respiratory support)

Bacillus cereus food poisoning

Bacillus cereus

Supportive care

• oral/IV fluids

• antiemetics

• No antibiotics needed

Clostridium perfringens food poisoning

Clostridium perfringens

Supportive care

• oral/IV fluids

• No antibiotics needed

Vibrio parahaemoluticus

Vibrio parahaemolyticus

Supportive care

• oral/IV fluids

  • Antibiotics rarely needed unless severe

Pharyngitis

GAS, Viral

Streptococcal:

• Penicillin V PO or Amoxicillin PO

Viral:

• Supportive care (analgesics, hydration)

Otitis Media (acute)

Streptococcus pneumoniae. Non-typeable H. influenzae, Moraxella catarrhalis

Amoxicillin PO (high dose)

Otitis Externa (Swimmers Ear)

Pseudomonas aeruginosa, Staphylococcus aureus, Fungi (Aspergillus, Candida)

Topical fluoroquinolone (Ciprofloxacin drops) or Ofloxacin otic dropsEp

Epiglottis

H. influenzae type b (Hib)

• Ceftriaxone IV or Cefotaxime IV

• Supportive care and airway monitoring

  • Hospitalize

Sinusitis

Streptococcus pneumoniae, H. influenzae, Moraxella catarrhalis

Amoxicillin-clavulanate PO

Typical CAP (Commonly Acquired PNA)

Streptococcus pneumoniae, H. influenzae, Moraxella catarrhalis

Amoxicillin PO (if no comorbidities) or Amoxicillin-clavulanate PO

Atypical CAP (“Walking PNA”)

Mycoplasma pneumoniae (MC), Chlamydophila pneumoniae, Legionella pneumophila, Klebsiella pneumoniae (MC), Respiratory viruses

Azithromycin PO or Doxycycline PO

Aspiration PNA (Community Onset)

Anaerobic bacteria, Oral aerobic flora (Streptococcus spp., Staphylococcus aureus, H. influenzae), Gram-negative bacilli

Amoxicillin-clavulanate PO or Ampicillin-sulbactam PO

HAP

Gram-negative bacilli (Klebsiella, Pseudomonas, Enterobacter, E. coli), Staphylococcus aureus (MSSA or MRSA), Enterococcus species

Piperacillim-tazobactam IV or Cefepime IV or Levofloxacin IV/PO or Vancomycin or Linezolid (both IV and for MRSA risk)

VAP

Pseudomonas aeruginosa, Acinetobacter baumannii, MRSA, Gram-negative bacilli (Klebsiella, Enterobacter, E. coli)

Piperacillin-tazobactam IV or Cefepime IV or Meropenem IV + Vancomycin or Linezolid (if MRSA risk factors)

Meningitis (Neonatal <1 Month)

GBS, E. coli, Listeria monocytogenes

Ampicillin IV + Cefotaxime IV

Meningitis (Infant/child 1 month - 18 years)

Streptococcus pneumoniae, Neisseria meningitidis, H. influenzae type b (if unvaccinated)

Ceftriaxone IV + Vancomycin IV

Meningitis (Adult 18-50 years)

Streptococcus pneumoniae, Neisseria meningitidis

Vancomycin IV + Ceftriaxone IV

Meningitis (Older adult/immunocompromised >50 years)

Streptococcus pneumoniae, Listeria monocytogenes, Gram-negative bacilli

Vancomycin IV + Ceftriaxone IV + Ampicillin IV (for Listeria coverage)

Secretory Diarrhea (Vibrio cholerae)

Doxycycline PO or Azithromycin PO

• Mainstay of therapy: Aggressive oral/IV rehydration

Secretory Diarrhea (Enterotoxigenic E. coli (ETEC))

Azithromycin PO or Rifaximin PO

Secretory Diarrhea (Clostridioides difficile)

Fidaxomicin PO or Vancomycin PO

Inflammatory diarrhea (Shigella spp.)

Azithromycin PO or Ceftriaxone IV (if severe disease)

Inflammatory diarrhea (Salmonella (non-typhoidal))

• Supportive care (for most immunocompetent patients)

• Oral rehydration

Inflammatory diarrhea (Campylobacter jejuni)

Azithromycin PO

Inflammatory diarrhea (Shiga toxin-producing E. coli (STEC/EHEC))

• Supportive care only

• Aggressive oral/IV hydration

• Monitor for HUS

Inflammatory diarrhea (Yesinia entercolitica)

• Supportive care

• Oral rehydration

Inflammatory diarrhea (Clostridioides difficile)

Fidaxomicin PO or Vancomycin PO

Inflammatory diarrhea (Entamoeba histolytica)

Metronidazole PO + Paromomycin (luminal agent)

Tularemia (Francisella tularensis)

Gentamicin IV/IM or Streptomycin IM

Brucellosis (Brucella spp.)

Doxycycline PO + Rifampin PO

Plague (Yersinia pestis)

• Gentamicin IV

• Streptomycin IV/IM

• Doxycycline PO/IV

Cat Scratch Disease (Bartonella henselae)

Azithromycin PO

Pasteurellosis (Pasteurella multocida)

Amoxicillin-clavulanate PO

Psittacosis (Chlamydia psittaci)

Doxycycline PO

Anthrax

Bacillus anthracis

Ciprofloxacin IV or Doxycycline IV/PO + Additional agents for systemic disease: consider adding Clindamycin IV (to inhibit toxin production)

UTIs (E. coli)

• Nitrofurantoin

  • Fosfomycin (single dose)

UTIs (Proteus mirabilis)

• TMP-SMX (if susceptible)

• β-lactam (ex. ampicillin, cefazolin)

UTIs (Enterococcus faecalis)

Amoxicillin/Ampicillin (if susceptible)UTIs

UTIs (Klebsiella pneumoniae)

Ceftriaxone (if susceptible)

UTIs (Staphylococcus saprophyticus)

Nitrofurantoin

UTIs (Pseudomonas aeruginosa)

Piperacillin-tazobactam (if susceptible)UTIs

UTIs (Serratia marcescens)

Cefepime (if susceptible)