Gram-negative bacilli resistant to third-generation cephalosporins: beta-lactamase characterization and susceptibility to XXXX .

@entity5503 @entity16397 @entity2892 @entity2756 @entity4028 @entity7660 @entity3524 @entity2893 @entity581 @entity12301 @entity3400 @entity2891 @entity5646 @entity5505 @entity25054 @entity3399
We studied 192 recent clinical isolates, comprising six species of Gram-negative bacilli resistant either to @entity3524 or latamoxef ( @entity3399 ), from several hospitals. All isolates were resistant to several other third-generation cephalosporins or a @entity16397 . Two to five types of chromosomal beta-lactamases, as defined by isoelectric focusing, were readily identified in each species. Isolates of Citrobacter, Enterobacter and Serratia produced higher levels of chromosomal beta-lactamase than corresponding @entity3524 -susceptible strains. In addition, 20 of 57 produced one or two plasmid-determined beta-lactamases, @entity25054 , OXA-2, or a novel enzyme, OHIO-1. The penem and @entity2893 antibiotics, @entity12301 and @entity2892 , were more active than @entity3524 , @entity5505 , @entity2756 , @entity3399 and @entity5646 against isolates of Acinetobacter, Citrobacter, Ent. aerogenes, Ent. cloacae and Morganella, whereas @entity2892 , @entity5505 , and @entity5646 were more active against Serratia isolates. The addition of plasmid-determined beta-lactamase increased resistance to @entity3400 , @entity2891 and @entity5503 but not to @entity3524 , @entity5505 , @entity2756 , latamoxef, @entity5646 , @entity12301 , or @entity2892 . Of 24 strains susceptible to @entity581 , none produced a plasmid-determined beta-lactamase, whereas 20 were found among the 33 strains resistant to @entity581 . Resistance of clinical isolates to newer @entity7660 appears to be due primarily to a high level of chromosomal cephalosporinase present without inducing agents. The plasmid-determined beta-lactamases, @entity25054 and OHIO-1, contributed little to resistance to most of the newer @entity7660 but were strongly associated with @entity4028 resistance in these selected isolates. The greater in-vitro efficacy of the penem and @entity2893 antibiotics, @entity12301 and @entity2892 , against most of these isolates makes them promising candidates as first line agents against these pathogens.
