Literature suggests MBL producers are not able to hydrolyze Aztreonam (Monobactam) but during my thesis work I found most of the MBL producer Pseudomonas aeruginosa isolates are resistant to Aztreonam and some other researchers has also reported aztreonam resistance MBL producer Pseudomonas. Does anybody have idea of this type of resistance mechanism?
Even the Psedomonas aeruginosa which are not consider multi-resistant can have a certain level of resistance due to efficient efflux pumps.
Hi, Saroj,
you shall keep in mind that producing a MBL does not exclude the presence of other mechanisms of resistance. As a general rule, MBLs do not hydrolize monobactams, but P. aeruginosa isolates producing MBLs can be also resistant to aztreonam by producing other beta-lactamases such as ESBLs (unlikely in Pseudomonas), by efflux pumps of by outer membrane impermeability. You can check it by studying the outer membrane proteins.
While going through the literature most of the researchers suggest derepression of AmpC and /or up-regulated efflux beyond aztreonam resistance in MBL producer Pseudomonas aeruginosa but I did not found specific literature regarding it.
Thank you Catherine Chaput and Jaun Luis sir for your suggestion.
this might be due to the decreased ring strain as azetreonam is monocyclic and not attached to any other ring.
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