Klebsiella oxytocaand K1 enzyme

(indole positive)

• Chromosomal

R/ ampicillin • Mutational hyperproduction

R/ cephalosporins• Less susceptible to clavulanic acid than ESBL

No key holeKey hole not obvious

A Klebsiella oxytoca with basal K1 -lactamase resistant to ampicillin and susceptible to Augmentin, cephalexin and cefotaxime.

A hyperproducer Klebsiella oxytoca with a high level of mutational K1 -lactamase shows resistance to Augmentin, cephalexin and cefotaxime.

Another hyperproducer Klebsiella oxytoca with a high level of mutational K1 -lactamase. Note the tiny "keyhole" between cefotaxime (CTX 5) and Augmentin (AMC 60) and the small inhibitory zone around cephalexin (CL100). The tiny "keyhole“ is a “bonus” as most strains with high K1 activity simply show resistance to Augmentin, cephalexin and cefotaxime.

A hyperproducer Klebsiella oxytoca with a low level of mutational K1 -lactamase. Note the slight synergy between Augmentin (AMC 60) and the cephalosporin discs cephalexin (CL100) and cefotaxime (CTX 5).

A Klebsiella oxytoca with an ESBL. It’s likely that the isolate only has basal K1 -lactamase (large zone around AMC 60).

Reporting

Klebsiella oxytoca hyperproducer of K1

Not ESBL (plasmid mediated)

As per Table 4

R/ ampicillin, cephalexin, cefotaxime…..