Viridans-Group Streptococci

Background

• A Gram Positive Bacteria in the Streptococcus Genus
• In general, low virulence pathogens and likely contaminants (21-50% of positive blood cultures are clinically significant) unless risk factor (see below)

Types

• • Streptococcus milleri
  • Streptococcus sanguis
  • Streptococcus mitis
  • Streptococcus bovis

Risk Factors Viridans Bacteremia

• neutropenia
• oral mucositis
• irradiation to the oral cavity
• antibiotic prophylaxis with trimethoprim-sulfamethoxazole and fluoroquinolones
• intravenous hyperalimentation
• high dose chemotherapy

Antibiotic Sensitivities

Organisms	'	Viridans strep
Penicillins	Penicillin G	+/-
	Penicillin V	+/-
Anti-Staphylocccal Penicillins	Methicillin	+/-
	Nafcillin/Oxacillin	+/-
	Cloxacillin/Diclox.	+/-
Amino-Penicillins	AMP/Amox	+/-
	Amox/Clav	+/-
	AMP-Sulb	+/-
Anti-Pseudomonal Penicillins	Ticarcillin	+/-
	Ticar-Clav	+/-
	Pip-Taxo	+/-
Carbapenems	Piperacillin	+/-
	Doripenem	+
	Ertapenem	+
	Imipenem	+
	Meropenem	+
	Aztreonam	0
Fluroquinolones	Ciprofloxacin	0
	Ofloxacin	0
	Pefloxacin
	Levofloxacin	+
	Moxifloxacin	+
	Gemifloxacin	+
	Gatifloxacin	+
1st G Cephalosporin	Cefazolin	+
2nd G. Cephalosporin	Cefotetan	+
	Cefoxitin	+
	Cefuroxime	+
3rd/4th G. Cephalosporin	CefoTAXime	+
	Cefizoxime	+
	CefTRIAXone	+
	Ceftobiprole	+
	Ceftaroline	+
	CefTAZidime	+/-
	Cefepime	+
Oral 1st G. Cephalosporin	Cefadroxil	+
	Cephalexin	+
Oral 2nd G. Cephalosporin	Cefaclor/Loracarbef	+
	Cefproxil	0
	Cefuroxime axetil	+
Oral 3rd G. Cephalosporin	Cefixime	+
	Ceftibuten	0
	Cefpodox/Cefdinir/Cefditoren	+
Aminoglycosides	Gentamicin
	Tobramycin
	Amikacin
	Chloramphenicol
	Clindamycin
Macrolides	Erythromycin
	Azithromycin
	Clarithromycin
Ketolide	Telithromycin
Tetracyclines	Doxycycline
	Minocycline
Glycylcycline	Tigecycline
Glyco/Lipoclycopeptides	Vancomycin
	Teicoplanin
	Telavancin
	Fusidic Acid
	Trimethoprim
	TMP-SMX
Urinary Agents	Nitrofurantoin
	Fosfomycin
Other	Rifampin
	Metronidazole
	Quinupristin dalfoppristin
	Linezolid
	Daptomycin
	Colistimethate

Key

• S susceptible/sensitive (usually)
• I intermediate (variably susceptible/resistant)
• R resistant (or not effective clinically)
• S+ synergistic with cell wall antibiotics
• U sensitive for UTI only (non systemic infection)
• X1 no data
• X2 active in vitro, but not used clinically
• X3 active in vitro, but not clinically effective for Group A strep pharyngitis or infections due to E. faecalis
• X4 active in vitro, but not clinically effective for strep pneumonia

See Also

• Microbiology (Main)