PSEUDOMONAS
Signs and Symptoms
Pseudomonal infections can involve the following parts of the body, with corresponding symptoms and signs:
➤ Respiratory tract (eg, pneumonia)
➤ Bloodstream (bacteremia)
➤ Heart (endocarditis)
➤ CNS (eg, meningitis, brain abscess)
➤ Ear (eg, otitis externa and media)
➤ Eye (eg, bacterial keratitis, endophthalmitis)
➤ Bones and joints (eg, osteomyelitis)
➤ GI tract (eg, diarrhea, enteritis, enterocolitis)
➤ Urinary tract
➤ Skin
Physical findings depend on the site and nature of the infection, as follows:
➤ Endocarditis: Fever, murmur, and positive blood culture findings; peripheral stigmata such as Roth spots, Janeway lesions, Osler nodes, splinter hemorrhages, and splenomegaly
➤ Pneumonia: Rales, rhonchi, fever, cyanosis, retractions, and hypoxia; occasionally shock; with cystic fibrosis, clubbing, increased anteroposterior (AP) diameter, and malnutrition
➤ GI tract: Fever, signs of dehydration, abdominal distention, and signs of peritonitis; physical findings of Shanghai fever
➤ Skin and soft tissue infections: Hemorrhagic and necrotic lesions, with surrounding erythema; subcutaneous nodules, deep abscesses, cellulitis, and fasciitis; in burns, black or violaceous discoloration or eschar
➤ Skeletal infections: Local tenderness and a decreased range of motion; neurologic deficits
➤ Eye infections: Lid edema, conjunctival erythema and chemosis, and evere mucopurulent discharge
➤ Malignant otitis externa: Erythematous, swollen, and inflamed external auditory canal; local lymphadenopathy
➤ Bacteremia: Fever, tachypnea, and tachycardia; hypotension and shock; jaundice
Diagnosis
Laboratory studies that may be helpful include the following:
➨ Complete blood count (CBC)
➨ Blood cultures
➨ In urinary tract infection (UTI), urinalysis
➨ In pneumonia, culture of sputum and respiratory secretions, as well as blood gas analysis
➨ Wound and burn cultures and cultures from other body fluids and secretions according to the clinical scenario
➨ Gram stain and culture of CSF if meningitis is suspected
➥Pseudomonas aeruginosa is member of the Gamma Proteobacteria class of Bacteria. It is aerobic bacterium belonging to the bacterial family Pseudomonadaceae.
GRAM Stain
Pseudomonas aeruginosa is a Gram-negative rod measuring 0.5 to 0.8 µm by 1.5 to 3.0 µm. Almost all strains are motile by means of a single polar flagellum.
Pseudomonas aeruginosa has very simple nutritional requirements. It is often observed "growing in distilled water", which is evidence of its minimal nutritional needs. In the laboratory, the simplest medium for growth of Pseudomonas aeruginosa consists of acetate as a source of carbon and ammonium sulfate as a source of nitrogen.
P. aeruginosa isolates may produce three colony types. Natural isolates from soil or water typically produce a small, rough colony. Clinical samples, in general, yield one or another of two smooth colony types. One type has a fried-egg appearance which is large, smooth, with flat edges and an elevated appearance. Another type, frequently obtained from respiratory and urinary tract secretions, has a mucoid appearance, which is attributed to the production of alginate slime. The smooth and mucoid colonies are presumed to play a role in colonization and virulence.
The oxidase test is a biochemical reaction that assays for the presence of cytochrome oxidase, an enzyme sometimes called indophenol oxidase. In the presence of an organism that contains the cytochrome oxidase enzyme, the reduced colorless reagent becomes an oxidized colored product. The oxidase test often uses a reagent, tetra-methyl-p-phenylenediamine dihydrochloride (or KOVÁCS reagent), as an artificial electron donor for cytochrome c. When the reagent is oxidized by cytochrome c, it changes from colorless to a dark blue or purple compound, indophenol blue. There are many method variations to the oxidase test. These include, but are not limited to, the filter paper test, filter paper spot test, direct plate method, and test tube method.
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