ABSTRACT

Gram negative non-fermentative bacteria constitute a complex group of taxonomically unrelated genera and species or provisionally designated taxa. They share the fundamental characteristic that, when tested using classic microbiological methods such as by Triple Sugar Iron (TSI) or Kligler's agar, they lack the ability to ferment carbohydrates. Glucose non-fermenting Gram negative bacteria (GNFGNB) may either utilize substrates via oxidative pathways or are inherently unable to either ferment or oxidize carbohydrates (1). Certain GNFGNB are serious pathogens which can be associated with both epidemics or sporadic infections. They include risk level 3 bacteria (e.g., Burkholderia pseudomallei, B. malleI) as well as risk level 2 pathogens (e.g., Pseudomonas aeruginosa, B. cepacia, Acinetobacter spp., and Stenotrophomonas maltophilia), all of which may be resistant to multiple antibiotics and disinfectants (2) and may cause serious, debilitating disease that can be associated with significant mortality. Most GNFGNB, however, are uncommon opportunistic pathogens which, when isolated, must be carefully evaluated for clinical relevancy in order to assess if full identification to genus and species or taxon group is justified. Such relevancy should include considerations for underlying patient disease, immune status, and recovery of the pathogen from normally sterile body sites or in highly significant numbers from other clinical sources. The taxonomy, risk factors for infection, and virulence markers of GNFGNB have been the subject of intense study in recent years. This work has resulted in greater precision for defming virulence factors as well as a dramatic increase in the number of genera and species and provisional taxa with which the microbiologist must contend. The pathogens described in this chapter have all been associated with disease in humans (rather than being recovered solely from animals, plants, or the environment). (Table I) Using that criterion, B. mallei, which is derived from equine disease, is not further discussed here.