PSEUDOMONAS

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ALT CULTURE CLUB



Topic: Microbes in Petri Dish - They Live Among Us

PSEUDOMONAS

PSEUDOMONAS maybe the nearest thing to spontaneous generation - living things coming out of non-living things.  The ever present danger of Pseudomonas aeruginosa cross infection is most typically exemplified by the situation arising in cases of burns.  Hardly any burn case with over 30 percent of body surface affected and staying in hospital long enough will escape colonization or infection by Pseudomonas aeruginosa.  Airborne Pseudomonas infection is relatively uncommon, that is the isolation of Pseudomonas from the air.  In a study, eight plates were exposed for 24 hours round the clock, changing them every few hours in a small cubicle occupied by a patient with Pseudomonas.  Not a single Ps. aeruginosa colony was found.  Pseudomonas can be found first of all where there is moisture.  This leads us to the role of drainage and plumbing system - that is, sinks, washbasins and traps, swimming pools, jacuzzis and other reservoir can become a source of cross infection.  Pseudomonas aeruginosa, which can grow and multiply at relatively lower temperature, thus enjoys excellent breeding conditions.  Being a motile organism, it "wriggles" its way upwards into the basin, finding en route and excellent hiding place which is inaccessible to cleaning from below and flushing from above which can't be sterilized.  Strains of Pseudomonas aeruginosa which could have come only from the trap, were frequently isolated from washbasins.  Washing with water does not eliminate the danger of contamination.  This was shown experimentally by seeding the trap and plughole area with a fluorescent dye and Serratia marcescens.  Both the dye and the organism could be recovered from the hands, obviously due to backflash.  A potentially dangerous sources of cross infection - thermometers (disposable thermometers preferred) and fresh flowers in hospital rooms.  When contaminated, active dissemination occurs when the thermometer is shaken or the flowers removed or handled.  It is also found that Pseudomonas is not sensitive to drying.  In fact, on the floor of the hospital room, it will survive for 72 hours.  Under experimental condition in a fan ventilated oven, temperature of 65 C for many hours and up to 95C for shorter periods of time failed to kill a broth suspension of Pseudomonas dried onto a lino tile.

On a number of occasions patient's raw areas were colonized or infected by strains isolated from the traps of washbasins previous to the patient's admission.  The strains belong to rare Pyocyanea groups (pyocin, serological and phage-typing where submicroscopic, usually viral organism that destroys bacteria), and in one case the strain was a rubrum type, which increased the chance of positive identification.  A patient become infected with this strain after ward had been closed, washed and fumigated 2 weeks prior to admission and thorough bacteriological check revealed the presence of the strain only in the washbasin trap.  Pseudomonas is extremely difficult to eliminate once it is established in the trap. 

Disinfectants in 10% concentration are capable of killing Pseudomonas under suitable conditions given sufficient concentration and time, but if the killing is longer than the drying out or evaporation time of the disinfectant applied to the surface, the whole exercise is pointless.  It is not so much the type of disinfectant which matters but the way it is used.

LAB CULTURE

Trypticase Soy Agar  (TSA) Plate/Broth - Green pigment

Odor - Grapelike, sweet smell

Motile

Isolated from: Burn victims, ear drainage

Resistance to antimicrobial agents - Very resistant

OBSERVATION

Positive Ps. aeruginosa in Blood Cultures - Massive invasion indicative of patient about to expire.

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