From Pseudomonas, P. aeruginosa represents between 60 and 80% of the strains isolated in the clinic, but other species may meet P. putida, P. fluorescens, P. cepacia, P. pseudoalcaligenes, P. paucimobilis, P. acidovorans …The events leading to the isolation of P. aeruginosa hospital also promote swarming other Pseudomonas.
However they have different metabolic potential and pathogenicity less than the B. aeruginosa. Such asPseudomonas they are less important in human pathology. Their isolation is often a function of the local ecology and usually limited to the high risk of infection services. We must also remember that these germs are often multiresistant to antibacterial agents. They can grow from multiple simple or complex hydrocarbon substrates. Because of their specific pathogenicity, two species are placed quite apart P. mallei, glanders and P. pseudomallei or B. Whitmore, an agent of melioidosis.
I – Pseudomonas mallei: THE SNOT
Glanders is a disease that primarily affects horses and is known since antiquity. P. mallei is an obligate parasite of the mucosa of animals or humans. Bacteriological standpoint this germ is always still and accumulate poly-beta-hydroxybutyrate. Glanders is a serious disease transmissible to humans. Disease disappeared in developed countries thanks to advances in veterinary medicine, it still exists in Asia and Africa. Screening for animals affected is through intradermal injection of positivity mallein which causes the slaughter of the infected herd.
II – Pseudomonas pseudomallei: melioidosis
Whitmore and Karischnaswami described in 1912 in Rangoon in Burma a nearby disease glanders they called melioidosis. P. B. pseudomallei or Whitmore is in water and moist soils.
This germ has long been regarded as a characteristic of wetlands in Southeast Asia, where moisture related to a high temperature (40-43 ° C) of rice water achieves optimal growing conditions. However it turns out that this organism is ubiquitous. Its isolation was carried out in France and in several countries inter-tropical areas, so it is present in an area between the parallel twentieth North and South. A better understanding of this disease has been acquired as a result of the wars in Indochina and Vietnam. The transmission of B. Whitmore can be by ingestion of contaminated water, penetration through the excoriated skin (wounds, scrapes, wounds), airborne contamination by dust mobilized by wind or aerosols created by the breath of the blades helicopters. The disease was also observed in France (epidemics in animals in the Jardin des Plantes and aging in Mayenne).
From the clinical point of view, melioidosis is a suppurative infection beyond a simple general description because of the diversity of forms and locations. We meet with acute forms septicopyohémiques secondary locations, but also more frequent subacute and chronic forms. Contracted mainly in the regions of Southeast Asia, at least in recently reported cases, melioidosis can occur long after the contamination, particularly in immunocompromised patients, it must be mentioned during fevers in migrant subjects from these regions. Splenic abscesses have been described, ceftazidime seem the most active.
Bacteriological diagnosis is made from various samples (blood, pus, sputum). The germ can be grown on various media. The differential diagnosis will be made with P. . cepacia, P. stutzeri, P. mallei Experimental pathogenicity is formed in the hamster or guinea pig: after inoculation by intraperitoneally purulent peritonitis is observed, a periorchitis (sign Straus), multisystem suppurations and first pulmonary place.
III – OTHER SPECIES OF INTEREST MEDICAL Pseudomonas:
The genus Pseudomonas includes many other species that can be isolated in humans or in animals but also in plants. The boundary between the plant pathogenic Pseudomonas and those of medical interest is quite imprecise in some cases.
A – Housing and pathogenic natural power:
Because of their very modest nutrient requirements, Pseudomonas can survive and multiply for months in a humid environment: tap water, distilled water, sinks flows, wet, bubblers, misters. The usual habitat of these organisms is water and the soil and plants. Some psychrophilic strains cause the deterioration of foods or organic products kept cold (P ‘. Fluorescens st P. putida example).
Conversely P. cepacia or P. pseudoalcaligenes are relatively resistant to heat and can be found in warm or hot water.
In hospital water contamination in the diversity of their uses is often hidden and it is emphasized that bacterial densities of about 107 cells / ml are not accompanied by visible haze to the naked eye to an aqueous solution. In the hospital environment Pseudomonas contaminate most often the antiseptic solutions, more active on Gram-positive than Gram-negative bacteria, as well as aqueous solutions.
The use of these contaminated solutions is responsible for the occurrence of infection in patients with immune defenses collapsed in high infection risk services (intensive care, hematology-oncology, burn service and cardiovascular surgery).
The clinical expression of the infection caused by these opportunistic pathogens few pathogens themselves, depend essentially on the ground. In these patients local secondary infections can cause bacterial simple but true septicemia with secondary locations, such as endocarditis where opportunities for diagnosis and antibiotic treatment are generally limited.
B – Ecology and meaning of different Pseudomonas species:
P. fluorescens and P. putida isolated for the first time in 1886 in various rots, have as their main habitat soil, water, plants and food spoiled. Hospital water is often contaminated with P. fluorescens, a species that is also very common in natural waters gifted even drinkable. P. fluorescens and P. putida can be found in the flora of the oropharynx. P.putida isolates in small quantities with a frequency equal to one third of that of P. P. aeruginosa and maltophilia,objects and hospital equipment. Both psychrophilic species may also contaminate the blood used in transfusion may be contaminated during collection or through improperly sterilized equipment or infusion bottles. From the point of view of clinical bacteriology P. fluorescens and P. putida are primarily opportunistic pathogens for humans.Virulence is of course almost zero in a healthy individual. The interpretation in isolation of these bacteria, single or repeated, only as the function of the clinical context. Symptoms of sepsis arising in the aftermath of a transfusion or contaminated liquid infusion can be explained by the presence of an endotoxin similar to those of other gram-negative bacilli.
P. stutzeri described for the first time in 1895 was isolated from soil, fertilizer, straw, humus, standing water, cosmetics for the eyes. This species can be found in various pathological products of human origin without being able to relate to specific epidemiological circumstances.
P. mendocina was isolated from soil, water and urine. It has not been implicated as a causative agent in human infections.
P. cepacia (Syn., Pseudomonas multivorans, Stanier) isolated for the first time in 1950 with an onion is remarkable for the variety and number of substrates that can be used as an energy source and carbon.
P. cepacia was originally described in 1950 as a plant pathogen germ but in recent years its isolation in hospital contamination or infection is more frequent.
Nine serotypes 0 and 7 H serotypes are described. Widely distributed in nature, it has been isolated from soil, river water, raw milk or pasteurized, salted duck eggs imported from Taiwan in the US, contaminated cosmetics from tap water.
The hospital environment allows frequently isolate P. cepacia: Instruments, nebulizers, humidifiers, hemodialysis machines, bronchoscopes, urinary catheters, catheters, anesthetic solutions, antiseptic solutions based on quaternary ammonium compounds, cetrimide, povidone iodine, chlorhexidine contaminating skin and instruments, injectable isotonic solution of sodium chloride, pharmaceutical solutions based on antibiotics, albumin, corticosteroids, waters of various origins (tap water, distilled water from commercial sources or prepared in hospital pharmacies, water of water bath used to warm the blood before transfusion).
In hospitalized patients, P. cepacia can be isolated: abscesses, infected wounds, hyperkeratotic lesions macerated toe in soldiers, acute arthritis (after injection of contaminated methyl-prednisolone), lung infections or urinary tract infections (after operation instrumental or surgical), peritonitis. Are more severe infections, transient bacteremia or septicemia, are encountered in patients with impaired immune defenses. Endocarditis have occurred in patients carrying cardiac prostheses or heart background, and occasionally heroin addicts. P. cepacia may be responsible for infectious complications in cardiac surgery. The wide variety of substrates used by P. cepacia is responsible for the variety of potential sources of contamination and infection.
However, it appears to have low virulence and limited invasiveness in healthy humans. It occurs in secondary infections of cystic fibrosis.
P. putrefaciens has the Pseudomonas characters; However, the authors propose to assign the name of Alteromonas putrefaciens because some strains possess a lateral flagellum in addition to the usual polar flagellum.The majority of the strains can grow at 30 ° C, some do not grow at 35 ° C and some psychrophilic. The essential feature of this organism is to produce H2S on usual media for Enterobacteriaceae and this often leads to confusion with Salmonella or Proteus. P. putrefaciens is in the soil, talented and salt water, brine and is widely distributed in nature. It is isolated in food (cod, poultry, milk, eggs). P. putrefaciens is responsible for alterations putrid butter, the production of H2S in herring nets, greenish discoloration of the meat. Medical Bacteriology, this species was isolated in many pathological products but rarely acts as an opportunistic organism although it may be associated with septicemia, otitis and with leg ulcers in diabetic suppurations.
P. and P. alcaligenes pseudoalcaligenes were described in 1928 and 1966. These two species are very close, were isolated from water, swimming pools, contaminated milk and various human disease products. Their incidence in human disease is extremely low, and only a few isolated cases of contamination or secondary infection have been described.
P. diminuta and P. vesicularis are two rare species described in 1954 to one in 1971. These Pseudomonas are characterized by their requirements biotin, pantothenic acid, cyanocobalamin and further cysteine P. diminuta.Isolated also water and some pathological products, or their role as opportunistic pathogens is uncertain and their rare isolation.
P. and P. acidovorans testosteroni two species are close by the high degree of homology existing between their nucleic acids. Their biochemical characteristics are very similar and predominantly negative. P. acidovorans was isolated from urine, blood, pus, respiratory tract in humans and animals. Its role in human disease is questionable. P.testosteroni is responsible for rare cases of bacteremia.
Other Pseudomonas species are rarely encountered in medical bacteriology. These are essentially stem from the environment. They often pose differential diagnosis.
P. pickettii described in 1973, has been isolated from various medical products.
P. paucimobilis akin to Xanthomonas. It was isolated in blood cultures of CSF, urine, sputum, vaginal smears and can highlight common in the waters of the natural or hospital environment.
C – Bacteriological Diagnosis:
To identify these Pseudomonas of medical interest, the bacteriologist can take several paths by contacting either traditional methods, or miniaturized galleries ready to use. However it is good to remember that a correct orientation of the diagnosis must be made from the start paying special attention to the bacillus morphology and in particular to determine the type of cilia which is polar in the genus Pseudomonas, or monotriche multitriche . Staining flagella, using the methods of Rhodes or Leifson, is of obvious utility. Colony morphology is important. For example, colonies pleated “rough” are characteristic for a trained eye, P. stutzeri. pigment production on A and B circles King, yellow or pink pigmentation of colonies of some species on nutrient agar are guidance.
Finally, the reaction of the oxidase is important as well as the determination of the respiratory type deep agar containing no nitrates.
Conventional methods use conventional identification characters strict aerobic count (the usual methods for Enterobacteriaceae is inadequate): ADH, LDC; hydrolysis of glycosides: esculin, ONPG; cultures at 4 ° C and 41 ° C;nitrate broth; deep nitrate agar; search for enzymatic activities (gelatinase, amylase, Tween 80 esterase Lecithinase, DNase); accumulation of poly-beta-hydroxybutyric acid; Search the production of H2S, seeking a tetrathionate reductase. The additional characters are based:
– Or the study of carbon substrates used as the sole source of carbon and energy (auxanogramme in liquid medium M 63: lactate, acetamide, arginine, glucose, maltose, trehalose, mannitol, inositol, added growth factor methionine )
– On the study of the oxidation of sugars leading to the production of acid in the media (glucose, fructose, mannose, lactose, maltose, mannitol …). Other biochemical tests adapted to Pseudomonas, such as the study of the cleavage diphenols are described in the literature. The following table shows a schematic and quick orientation key to the identification of some common Pseudomonas.
Convenient identification galleries miniaturized for use are currently available (Pseudomonas-Diagnostics Pasteur Gallery Oxi-Ferm Tube-Roche, NC Flow Tek Gallery API 20 NE). They allow identification in 24 to 48 hours while traditional methods require 2-4 days.
D – Sensitivity to antibiotics:
The search for the sensitivity of the Pseudomonas antibiotic in addition to its interest in medical bacteriology used to provide assistance to the bacteriological diagnosis avoiding confusion between some species of Pseudomonas. For example it is easy to focus the differential diagnosis between X. maltophilia and P. cepacia recalling that the first is resistant to novobiocin and sensitive to colistin and P. cepacia the reverse.
The susceptibility of these Pseudomonas species is sometimes paradoxical although having neighboring characters than P. aeruginosa; data on the latter are not always applicable to other Pseudomonas sensitivity to aminoglycosides is variable depending on the species, almost all strains of P.. cepacia, X. maltophilia, P. acidovorans are resistant.
Colistin is active on these Pseudomonas except P. cepacia, P. pickettii, P. pseudomallei. Despite the usual multidrug resistance of these bacteria, with the new penicillins (carboxypénicillines) and third-generation cephalosporins (except cefsulodine), have come new therapeutic possibilities. It is useful to note that some Pseudomonas species possess inactive antibiotic sensitivity P. aeruginosa as trimethoprim-sulfamethoxazole.