Or is "acronymic" the correct adjective? In any case, the college loves to repeat this question. Recent iterations have included Question 3.3 from the first paper of 2014, Question 25.2 from the first paper of 2009 and Question 25.2 from the second paper of 2008.
The following is a list of Gram-negative organisms who might occasionally appear to be sensitive to β-lactam antibiotics, but who in fact develop a resistance rapidly, owing to the overexpression of induceable chromosomal AmpC cephalosporinase/β-lactamase enzymes.
The linked article on this topic also identifies Chromobacterium violaceum, Enterobacter, E. coli, Hafnia alvei, Lysobacter lactamgenus, Ochrobactrum anthropi, Proteus rettgeri, Pseudomonas aeruginosa, Psychrobacter immobilis, Rhodobacter sphaeroides and Yersinia enterocolitica as carriers of the AmpC cephalosporinase/β-lactamase.
An intelligent person would not be satisfied with a mere list, and would go on to ask the question,
George A. Jacoby puts it best in his excellent article, which is the primary resource for this topic:
"AmpC β-lactamases are clinically important cephalosporinases encoded on the chromosomes of many of the Enterobacteriaceae and a few other organisms, where they mediate resistance to cephalothin, cefazolin, cefoxitin, most penicillins, and β-lactamase inhibitor-β-lactam combinations"
In addition to the ESCAPPM bunch, in 2009 the Infectious Diseases Society of America launched another acronym to describe the group of pathogens which - over the coming decades - are going to pose the greatest threat to mankind by virtue of their antimicrobial resistance:
Panic regarding the "post-antibiotic era" is spread further by anxious reports of such nightmarish creatures as a pan-drug-resistant Acinetobacter, which apparently reproduces quite comfortably in a pot of boiling meropenem.
These are a bunch of oropharyngeal Gram-negatives which had previously been thought to be frequently responsible for infective endocarditis, but are now known to be fairly rare, responsible for only about 3% of native valve endocarditis.
Why care about them, if they are such rare pathogens? Well. The slow growth of these organisms means the cultures are usually negative. Vegetations will be visible, and PCR testing will reveal the relevant pathogen, but the cultures will remain negative. Fortunately, most of them are sensitive to bog-standard ceftriaxone.