Z Infection types of bacteria Flashcards
Community-Acquired Pneumonia (CAP)
S. pneumonia, H.influenza, Intracellular atypical organisms (Mycoplasma pneumoniae, Chlamydophila pneumoniae, Legionella), Respiratory viruses.
- S.aureus if IV drug user, recent influenza.
- Pseudomonas if structural lung disease (e.g. bronchiectasis, COPD with frequent steroid use).
Hospital, Healthcare- Associated, or Ventilator-Associated Pneumonia
(HAP, HCAP, VAP)
S.aureus (including MRSA) and aerobic gram negative rods including Pseudomonas aeruginosa, E.coli, Klebsiella pneumonia, and Enterobacter species. Multi-drug resistant (MDR) gram negatives are common in ICU patents.
*Role of anaerobes, even in nosocomial aspiration pneumonia, is unclear (but reasonable to add anaerobic coverage in that scenario).
Aspiration Pneumonia
Oral anaerobes, enteric gram negative rods, S.aureus, Streptococcus species
Appendicitis, Diverticulitis, Intraabdominal Abscess, Secondary Peritonitis
Polymicrobial GI flora including gram negative rods (especially E.coli) and anaerobes (especially Bacteroides).
For bowel perforation, microbiology depends on site. Upper GI tract (e.g. perforated duodenal ulcer) mainly Streptococcus species. Lower GI tract mainly gram negative rods and anaerobes.
Enterococcus and Candida species usually less important, except in healthcare-associated cases.
Spontaneous Bacterial Peritonitis (SBP) in patients with ascites
Gram negative rods including E.coli, Klebsiella, Enterobacter. Also, enteric Streptococci and Enterococci.
Cholangitis
Polymicrobial GI flora. Anaerobes if biliary-enteric anastomosis.
Enterococcus coverage usually not required.
Acute cystitis
E.coli is most common, followed by also other gram negatives (Proteus, Klebsiella, Serratia, Enterobacter) and Staph saphrophyticus
Acute pyelonephritis
Same as for acute cystitis
Complicated UTI (defined by presence of anatomic or functional abnormality in GU tract, or urinary catheter)
More likely to be due to resistant gram negatives including ESBL’s and Pseudomonas. Staph aureus is possible if chronic urinary catheters or stents. Also: Enterococcus, Candida.
Cellulitis
Streptococcus species (most commonly Group A), S.aureus including MRSA. More unusual pathogens are possible depending on risk factors (i.e. water exposures, animal bites, neutropenia).
Infected Diabetic Foot Ulcer
Streptococcus species, S.aureus including MRSA, Gram negative rods (E.coli, Klebsiella, Proteus, Pseudomonas), anaerobes.
Necrotizing Fasciitis
Type I is polymicrobial (Streptococci, Gram negatives) and also involves anaerobes.
Type II is due to beta-hemolytic strep (usually group A strep), less commonly CA-MRSA.
Septic Arthritis
S.aureus including MRSA, Streptococcus species (especially Group B strep in diabetics), N.gonorrhoeae (triad of pustular skin lesions, tenosynovitis, arthritis), Gram negative rods (Pseudomonas if IVDU).
Bacterial Meningitis, Community-Acquired
S.pneumo, N.meningitidis, H.influenza species.
Listeria if risk factors: Age >50, Immunocompromised
Nosocomial Meningitis
S.aureus, Coagulase-negative staph, Gram negative rods including P.aeruginosa