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Category: Clinical Microbiology
Pseudomonas, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555816728/9781555814632_Chap40-1.gif /docserver/preview/fulltext/10.1128/9781555816728/9781555814632_Chap40-2.gifAbstract:
As polyphasic taxonomy continues to advance, more changes will doubtlessly arise; a clinical laboratory must keep abreast of such changes, in order to differentiate these isolates from the more clinically important Pseudomonas species. Healthy individuals are resistant to serious infections by all Pseudomonas species, including P. aeruginosa. Immunocompromised hosts are occasionally infected with one of the many non-aeruginosa species, including (but not limited to) P. fluorescens, P. putida, P. stutzeri, P. oryzihabitans, P. luteola, P. alcaligenes, P. mendocina, and P. veronii. Historically, typing of P. aeruginosa for epidemiological purposes has relied upon phenotypic characteristics of the bacteria. The most widely used method was based upon differences in LPS O polysaccharide (LPS serotyping). Several genotypic methods have been developed over the past two decades for typing P. aeruginosa for epidemiological purposes. Isolates from sites of chronic infection, such as cystic fibrosis (CF) respiratory sites, often exhibit multiple morphotypes that can make identification difficult. Molecular methods increasingly are finding a role in the identification of this organism, especially for epidemiological studies. Susceptibility testing of P. aeruginosa is difficult, especially for mucoid isolates, due to increasing resistance, lack of reproducibility of results, and lack of clinical correlation. A basic understanding of the multiple mechanisms of resistance, both intrinsic and acquired, is essential to interpret susceptibility testing results and give therapeutic recommendations to physicians. Other Pseudomonas species are infrequently isolated in the laboratory and are usually not clinically significant. Clinical correlation and correlation with the Gram stain are essential before further workup is undertaken.
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Characteristics of Pseudomonas species found in clinical specimens a
a Results are given as percentage of positive strains; percentages in parentheses represent strains with delayedreactions. Data are from references 25, 32, 34, and 72.
b Oxidative-fermentative basal medium with 1% carbohydrate.
c ND, no data.
d P. stutzeri-like organisms (formerly CDC group 3b) arearginine dihydrolase positive.
e Growth at 3 to 5% NaCl but not at 7% NaCl.
f V, variable; many strains can grow at 41oC: See comment intext under identification.
Characteristics of Pseudomonas species found in clinical specimens a
a Results are given as percentage of positive strains; percentages in parentheses represent strains with delayedreactions. Data are from references 25, 32, 34, and 72.
b Oxidative-fermentative basal medium with 1% carbohydrate.
c ND, no data.
d P. stutzeri-like organisms (formerly CDC group 3b) arearginine dihydrolase positive.
e Growth at 3 to 5% NaCl but not at 7% NaCl.
f V, variable; many strains can grow at 41oC: See comment intext under identification.