BACTERIOPHAGE THERAPY OF PSEUDOMONAS BURN WOUND SEPSIS

Abul-Hassan H.S., El-Tahan k Massoud B., Gomaa R.

Plastic and Reconstructive Surgery Unit and Bacteriology Department, Faculty of Medicine, Alexandria, Egypt

SUMMARY. Phage therapy was used to control Pseudomonas aerugmosa infection in 30 cases of resistant infections in patients with bum areas ranging from 10-25%. Post-phage cultures showed absence of organisms in 12 patients and their presence in 18. Satisfactory graft take was present in 18 cases only and inferior take in 12 cases. It is not practical to use this technique on a wide scale and it should be restricted to cases with strains resistant to available antibiotics.

Bacterlophages can be used to distinguish bacteria on the basis of the particular phage or phages to which they are susceptible. These phages are able to kill bacteria and at the same time they are harmless to man. Attempts were therefore made to use them to treat bacterial infections. However the great variety of phage-specific strains of bacteria within a species and the rapidity with which phage-resistant forms develop are important limiting factors (1).

The aim of this study is to evaluate the efficacy of bacteriophage therapy in cases of pseudomonal infection of the burn wound, since Pseudomonas aeruginosa is one of the most resistant organisms for antibiotics.

Thirty cases of documented pseudomonas burn wound sepsis were treated by phage. These cases showed resistant Pseudomonas infection to all available antibiotics and chemotherapeutic agents.
The patients were 18 males and 12 females; six were children below the age of nine and the remaining cases had an age range from 18-54 years. The burned surface area ranged from 10-21%.
Swabs were taken from the burned areas and cases which showed resistant Pseudomonas infection were selected for our study. Antibiotics were stopped locally and systemically for 48 hours before swabbing.
Phage stock containing a high number of phages acting specifically on the strains of Pseudomonas originally isolated from the bum wound was prepared to be applied locally on the burn wound. The number of phages/ml stock was calculated according to Miles and Misra (2) to confirm that the phage stock contained a large number of phages (more than 1010/ml). Gauze soaked in phage was applied 3 times per day for each patient.
Assessment of phage application was made by temperature recording, observation of the general look of the patient, the local condition of the raw area and percent of graft take. Another swab was taken at the end of phage therapy.

Results

The application of the phage was needed for 5-7 days in almost 50% of the cases (15-21 dressings) (Tab. 1).
Eight cases showed sterile cultures after these applications and 7 cases positive for Pseudomonas aeruginosa with no control of infection by the phage (Tab. 2).
Tab. 3 demonstrates the amount of discharge, which stopped in 12 cases only, diminished in another 12 and was not affected in the others.
The granulation tissue showed improved criteria and decrease in oedema, a fiery red color, minimal discharge in 15 cases, slight improvement in 9 cases and no effect in 6 cases (Tab. 4).
Graft take was evaluated above 90% in 6 cases, from 60-70% in 12 cases and below 30% in 12 cases (Tab. 5).

The bacteriophages constitute a group of viruses which have various cocci, bacilli and vibrios as their specific hosts. They are found naturally in places where bacteria exist, e.g. the intestines of man, animals, insects, sewage and soil. Their presence can be demonstrated by the lytic action they produce in susceptible bacteria during active growth. They are highly specific agents acting only against one bacterial species or type or a few related types (3).
The ability of bacterial viruses to lyse and kill bacterial cells led to the hope that they would be therapeutically effective in bacterial infections. Many trials have been performed with variable results (4).
Since phages (like all viruses) multiply only within living cells, and since their size precludes direct observation except with the electron microscope, it is necessary to follow their activity by indirect means. For this purpose, advantage is taken of the fact that one phage particle introduced into a crowded layer of dividing bacteria on a nutrient agar plate will produce a more or less clear zone of lysis in the opaque film of bacterial growth. This zone of lysis is called a .. plaque; it results from the fact that the initially infected host cell bursts (lyses) and liberates dozens of new phage particles, which then infect neighbouring cells. This process is repeated cyclically until bacterial growth on the plate ceases as a result of exhaustion of nutrients and accumulation of toxic products. When handled properly, each phage particle produces one plaque; any material containing phage can thus be titrated by making suitable dilution and plating measured samples with an excess of sensitive bacteria. The plaque count is analogous to the colony for bacterial titration (5).
Pseudomonas aeruginosa, which is the most important and dangerous bacterium in burn sepsis and septicaemia, shows variable incidences. Sarsoor (6) found an average of 19.5% which is raised to 26% during hospitalization, and still has a high incidence in burns of the lower half of the body, and full-thickness burns (7). A high incidence was reportedby Thompson (53%) (8) and Ramirez (42%) (9).