Anaerobic Gram negative bacteria (other)

• Acidoaminococcus spp
• Alistipes spp
• Alloprevotella spp
• Anaerobiospirillium spp
• Barnesiella spp
• Bilophila spp
• Campylobacter (anaerobic) spp
• Christensenella spp
• Coprobacter spp
• Desulfomicrobium spp
• Desulfovibrio spp
• Dialister spp.
• Fretibacterium spp
• Fusobacterium spp.
• Jonquetella spp
• Leptotrichia spp
• Megamonas spp
• Odoribacter spp
• Paraprevotella spp
• Parasutterella spp
• Phascolarctobacterium spp
• Phocaeicola  spp
• Porphyromonas spp
• Prevotella spp
• Pseudoflavonifractor spp
• Pyramidobacter spp
• Selenomonas spp
• Sneathia spp.
• Succinatimonas spp
• Sutterella spp
• Synergistetes spp
• Tannerella spp.
• Veillonella spp

Clinical Significance

Many species of anaerobic Gram negative bacilli make up the normal flora of the upper respiratory, gastrointestinal, and female genitourinary tracts. 

They may be involved in polymicrobial infections, usually in association with abscess formation.  Infections with some of these organisms include head/neck, pleuropulmonary, skin/soft tissue, intra abdominal, and pelvic infections.  

Fusobacterium spp (especially F. necrophorum) are associated with septic thrombophlebitis (Lemierre’s disease) and retropharyngeal abscesses.

Usual Susceptibility Pattern

Most of these organisms are susceptible to metronidazole, amoxicillin-clavulanate, piperacillin-tazobactam, and carbapenems. 

Linezolid may have activity against some anaerobic Gram negative bacilli. 

Resistance to penicillins, cephalosporins, clindamycin, and moxifloxacin is significant and these agents should not be used empirically for serious anaerobic infections. 

There is a high incidence of penicillin resistance in Fusobacterium varium, Fusobacterium mortiferum, Prevotella spp and Sutterella spp. Sutterella may also be resistant to piperacillin-tazobactam. Dialister spp may be resistant to metronidazole. Metronidazole resistance is also reported in various other anaerobic Gram negative bacilli.