Postneurosurgical meningitis due to Proteus penneri with selection of a ceftriaxone-resistant isolate: analysis of chromosomal class A beta-lactamase HugA and its LysR-type regulatory protein HugR.

We report on a case of a postneurosurgical meningitis due to ceftriaxone-susceptible Proteus penneri, with selection of a ceftriaxone-resistant isolate following treatment with ceftriaxone. The isolates presented identical patterns by pulsed-field gel electrophoresis and produced a single beta-lactamase named HugA with an isoelectric point of 6.7. The ceftriaxone-resistant isolate hyperproduced the beta-lactamase (increase in the level of production, about 90-fold). The sequences of the hugA beta-lactamase gene and its regulator, hugR, were identical in both P. penneri strains and had 85.96% homology with those of Proteus vulgaris. The HugA beta-lactamase belongs to molecular class A, and the transcriptional regulator HugR belongs to the LysR family.