A convenient and reliable identification scheme for P. aeruginosa involves the following conventional tests and Iferact eristics:
P. aeruginosa, P.fluorescens, P. putida, P. veronii, and P. monteilii comprise the group known as the fluorescent pseudomonads. P. aeruginosa can be distinguished from the rti rs in this group by its ability to grow at 42° C. Mucoid strains of P. aeruginosa from patients with cystic fibrosis may not exhibit the characteristic pigment and ma react slower in biochemical tests than nonmucoid trains. Therefore, standard biochemicals should be held w the complete 7 days before being recorded as nega-ve. This slow, biochemical activity is often what prevents the identification of mucoid P. aeruginosa by commerdal systems. P. monteilii can be distinguished oin P. putida by its inability to oxidize xylose. Both can ^ distinguished from P. fluorescens by their inability to liquefy gelatin.
Burkholderia cepacia should be suspected whenever a Honfermentative organism that decarboxylates lysine
is encountered. Lysine decarboxylation is positive in 80% of strains. Correct identification of the occasional strains that are lysine-negative (20%), or oxidase-negative (14%), requires full biochemical profiling. Pan-doraea spp. may be differentiated from B. cepacia by their failure to decaiboxylate lysine and their inability to liquefy gelatin. They do not hydrolyze TWeen 80, unlike Ralstonia paucula, which does.
The presumptive identification of other spedes in this chapter is fairly straightforward using the key characteristics given in Table 24-4. However, there are a few notable exceptions. First, when B. cepacia complex is identified by a commerdal system in a cystic fibrosis patient, it should be reidentified by a combination of phenotypic and genotypic methods. This is also true if a rapid system identifies an organism as B. gladioli or R. pickettii. There are nine genomovars in the B. cepacia complex and appropriate spedation is very important.
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