<P> Recently, scientists have been examining the possible genetic basis for P. aeruginosa resistance to antibiotics such as tobramycin . One locus identified as being an important genetic determinant of the resistance in this species is ndvB, which encodes periplasmic glucans that may interact with antibiotics and cause them to become sequestered into the periplasm . These results suggest a genetic basis exists behind bacterial antibiotic resistance, rather than the biofilm simply acting as a diffusion barrier to the antibiotic . </P> <P> Depending on the nature of infection, an appropriate specimen is collected and sent to a bacteriology laboratory for identification . As with most bacteriological specimens, a Gram stain is performed, which may show Gram - negative rods and / or white blood cells . P. aeruginosa produces colonies with a characteristic "grape - like" or "fresh - tortilla" odor on bacteriological media . In mixed cultures, it can be isolated as clear colonies on MacConkey agar (as it does not ferment lactose) which will test positive for oxidase . Confirmatory tests include production of the blue - green pigment pyocyanin on cetrimide agar and growth at 42 ° C. A TSI slant is often used to distinguish nonfermenting Pseudomonas species from enteric pathogens in faecal specimens . </P> <P> When P. aeruginosa is isolated from a normally sterile site (blood, bone, deep collections), it is generally considered dangerous, and almost always requires treatment . However, P. aeruginosa is frequently isolated from nonsterile sites (mouth swabs, sputum, etc .), and, under these circumstances, it may represent colonization and not infection . The isolation of P. aeruginosa from nonsterile specimens should, therefore, be interpreted cautiously, and the advice of a microbiologist or infectious diseases physician / pharmacist should be sought prior to starting treatment . Often, no treatment is needed . </P> <Table> <Tr> <Th> Test </Th> <Th> Results </Th> </Tr> <Tr> <Td> Gram Stain </Td> <Td> - </Td> </Tr> <Tr> <Td> Oxidase </Td> <Td> + </Td> </Tr> <Tr> <Td> Indole Production </Td> <Td> - </Td> </Tr> <Tr> <Td> Methyl Red </Td> <Td> - </Td> </Tr> <Tr> <Td> Voges - Proskaeur </Td> <Td> - </Td> </Tr> <Tr> <Td> Citrate </Td> <Td> + </Td> </Tr> <Tr> <Td> Hydrogen Sulfide Production </Td> <Td> - </Td> </Tr> <Tr> <Td> Urea Hydrolysis </Td> <Td> - </Td> </Tr> <Tr> <Td> Phenylalanine Deaminase </Td> <Td> - </Td> </Tr> <Tr> <Td> Lysine Decarboxylase </Td> <Td> - </Td> </Tr> <Tr> <Td> Motility </Td> <Td> + </Td> </Tr> <Tr> <Td> Gelatin Hydrolysis </Td> <Td> + </Td> </Tr> <Tr> <Td> Acid from lactose </Td> <Td> - </Td> </Tr> <Tr> <Td> acid from glucose </Td> <Td> + </Td> </Tr> <Tr> <Td> acid from maltose </Td> <Td> - </Td> </Tr> <Tr> <Td> acid from mannitol </Td> <Td> + </Td> </Tr> <Tr> <Td> acid from sucrose </Td> <Td> - </Td> </Tr> <Tr> <Td> nitrate reduction </Td> <Td> + </Td> </Tr> <Tr> <Td> DNAse </Td> <Td> - </Td> </Tr> <Tr> <Td> Lipase </Td> <Td> + </Td> </Tr> <Tr> <Td> Pigment </Td> <Td> + (bluish green pigmentation) </Td> </Tr> <Tr> <Td> Catalase </Td> <Td> + </Td> </Tr> </Table>

When is pseudomonas aeruginosum identified as an infectious agent
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