Gram positive bacteria

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Cocci

Clusters (Staph Species)

  1. Coagulase Positive: Staph aureus
    1. Always consider as true bacteremia (and not a contaminant) due to the danger of delaying treatment[1]
  2. Coagulase Negative:
    1. Staph epidermidis
      1. Most common cause of catheter-related bacteremia[2]
      2. Most common skin contaminant found in blood cultures[3]
    2. Staph saprophyticus
      1. UTIs in women
    3. Staph lugdunensis
      1. Rare cause of endocarditis, meningitis, and Skin and Soft Tissue Infections
    4. Staph haemolyticus
      1. Rare cause of endocarditis, meningitis

Chains or Pairs (Strep Species and Related)

  1. Enterococcus (e.g. Enterococcus faecalis, Enterococcus faecium)
    1. May cause bacteremia in the proper clinical setting (UTI, intra-abdominal infections, infected vascular catheters, and endocarditis)[4]
  2. Strep viridans
      1. In general are low virulence pathogens and likely contaminants (21-50% of positive blood cultures are clinically significant)
      2. Risk factors for VGS bacteremia include: neutropenia, oral mucositis, irradiation to the oral cavity, antibiotic prophylaxis with trimethoprim-sulfamethoxazole and fluoroquinolones, intravenous hyperalimentation, high dose chemotherapy
  3. Streptococcus pneumoniae (Pairs)
    1. Asociated with pneumonia, meningitis, peritonitis and other severe infections
    2. Isolation of this organism is always significant and should be treated[5]
  4. Other Strep Species
      1. ß-hemolytic streptococcus (Group A Streptococcus, Group B Streptococcus, etc)

Rods (Bacilli)

Organism
Cult Morphology

Listeria monocytogenes

Small

Aero
tumbling
Diphtheroids
Small Anaero
pallisades
Actinomyces
Small Anaero
Branching
Propionibac
Small Anaero
clumps/pleo
Lactobacillus
Variable Both
may chain
Clostridium
Large Anaero
Spores
Bacillus Large Aero Spores

Interpretation of Key Phrases

  • “Gram positive cocci in clusters” may suggest Staphyloccocus species.
  • "Gram positive cocci in pairs and chains" may suggest Streptococcus species or Enterococcus species
  • “Branching Gram positive rods, modified acid fast stain positive” may suggest Nocardia or Streptomyces species

Antibiogram

Category Organism Strep. Group A, B, C, G Strep. Pneumoniae Viridans strep Strep. anginosus gp Enterococcus faecalis Enterococcus faecium MSSA MRSA CA-MRSA Staph. Epidermidis C. jeikeium L. monocytogenes
Penicillins Penicillin G S S I S S I R R R R R S
Penicillin V S S I S S I R R R R R R
Anti-Staphylocccal Penicillins Methicillin S S I S R R S R R S R R
Nafcillin/Oxacillin S S I S R R S R R S R R
Cloxacillin/Diclox. S S I S R R S R R S R R
Amino-Penicillins AMP/Amox S S I S S I R R R R R S
Amox-Clav S S I S S S S R R R R X2
AMP-Sulb S S I S S S S R R R R S
Anti-Pseudomonal Penicillins Ticarcillin S S I S I I R R R I R S
Ticar-Clav S S I S I I S R R I R X2
Pip-Tazo S S I S S I S R R S X1 X2
Piperacillin S S I S S I R R R R R S
Carbapenems Doripenem S S S S I R S R R S X1 S
Ertapenem S S S S R R S R R S R I
Imipenem S S S S S I S R R S R S
Meropenem S S S S I R S R R S X1 S
Aztreonam R R R R R R R R R R R R
Fluroquinolones Ciprofloxacin I I R R U R S R I S R S
Ofloxacin I I R R U R S R X1 S R R
Pefloxacin R R X1 X1 R R S R X1 S X1 R
Levofloxacin S S S S S R S R I S X1 S
Moxifloxacin S S S S S I S I I S X1 S
Gemifloxacin S S S S S I S I I S X1 S
Gatifloxacin S S S S S I S I I S X1 S
1st G Cephalo Cefazolin S S S X1 R X1 S R R I R R
2nd G. Cephalo Cefotetan S S S X1 R X1 S R R I R R
Cefoxitin S S S X1 R X1 S R R I R R
Cefuroxime S S S X1 R X1 S R R I R R
3rd/4th G. Cephalo Cefotaxime S S S X1 R X1 S R R I R R
Cefizoxime S S S X1 R X1 S R R I R R
CefTRIAXone S S S X1 R X1 S R R I R R
Ceftaroline S S S X1 S X1 S S S S X1 X1
CefTAZidime S S I X1 R X1 I R R I R R
Cefepime S S S X1 R X1 S R R I X1 R
Oral 1st G. Cephalo Cefadroxil S S S X1 R X1 S R R I R R
Cephalexin S S S X1 R X1 S R R I R R
Oral 2nd G. Cephalo Cefaclor/Loracarbef S S S X1 R X1 S R R I R R
Cefproxil S S R X1 R X1 S R R I R R
Cefuroxime axetil S S S X1 R X1 S R R I R R
Oral 3rd G. Cephalo Cefixime S S S X1 R X1 R R R R R R
Ceftibuten S I R X1 R X1 R R R R R R
Cefpodox/Cefdinir/Cefditoren S S S X1 R X1 S R R I X1 R
Aminoglycosides Gentamicin R R X1 X1 S S S R X1 I R S
Tobramycin R R X1 X1 S R S R X1 I R S
Amikacin R R X1 X1 S R S R X1 I R S
Chloramphenicol S S X1 X1 I I I R X1 R R S
Clindamycin S S X1 X1 R R S R I R R X1
Macrolides Erythromycin I I X1 X1 R R I R I I R S
Azithromycin I I X1 X1 R R S R I R R S
Clarithromycin I I X1 X1 R R S R I R R S
Ketolide Telithromycin S S X1 X1 I R S R I R R S
Tetracyclines Doxycycline I S X1 X1 R R I I S R R S
Minocycline S S X1 X1 R R S I S R R S
Glycylcycline Tigecycline S S X1 X1 S S S S S S S S
Daptomycin S X23 X1 X1 S S S S S S S I
Glyco/Lipoclycopeptides Vancomycin S S X1 X1 S I S S S S S S
Teicoplanin S S X1 X1 S I S S S I S S
Telavancin S S X1 X1 S S S S S S S S
Fusidic Acid I I X1 X1 S X1 S S S S S X1
Trimethoprim S I X1 X1 S R I I S S R S
TMP-SMX X22 S X1 X1 X22 R S S S I R S
Urinary Agents Nitrofurantoin S S X1 X1 S S S S S X1 R X1
Fosfomycin X1 S X1 X1 S I S S S X1 X1 R
Other Rifampin S S X1 X1 I R S S S S S S
Metronidazole R R X1 X1 R R R R R R R R
Quinupristin dalfoppristin S S X1 X1 R S S S S S S S
Linezolid S S X1 X1 S S S S S S S S
Colistimethate R R X1 X1 R R R R R R R R

Clinical Identification Chart

Gram-Positive Classification.png

Table Overview

See Also

Source

  1. Antibiotic Therapy for Positive Blood Cultures. Perez-Jorge EV, et al. Antimicrobe. http://www.antimicrobe.org/new/e38rev2.asp
  2. Antibiotic Therapy for Positive Blood Cultures. Perez-Jorge EV, et al. Antimicrobe. http://www.antimicrobe.org/new/e38rev2.asp
  3. Antibiotic Therapy for Positive Blood Cultures. Perez-Jorge EV, et al. Antimicrobe. http://www.antimicrobe.org/new/e38rev2.asp
  4. Antibiotic Therapy for Positive Blood Cultures. Perez-Jorge EV, et al. Antimicrobe. http://www.antimicrobe.org/new/e38rev2.asp
  5. Antibiotic Therapy for Positive Blood Cultures. Perez-Jorge EV, et al. Antimicrobe. http://www.antimicrobe.org/new/e38rev2.asp