Infection of burns

The efficacy of honey in inhibiting strains of Pseudomonas aeruginosa from infected burns

Because there is no ideal therapy for burns infected with Pseudomonas aeruginosa, there is sufficient need to investigate the efficacy of alternative antipseudomonal interventions. Honey is an ancient wound remedy for which there is modern evidence of efficacy in the treatment of burn wounds, but limited evidence for the effectiveness of its antibacterial activity against Pseudomonas. We tested the sensitivity of 17 strains of P. aeruginosa isolated from infected burns to two honeys with different types of antibacterial activity, a pasture honey and a manuka honey, both with median levels of activity. All strains showed similar sensitivity to honey with minimum inhibitory concentrations below 10% (vol/vol); both honeys maintained bactericidal activity when diluted more than 10-fold. Honey with proven antibacterial activity has the potential to be an effective treatment option for burns infected or at risk of infection with P. aeruginosa.

Chemical disinfection in the prevention of infection in hospital

Much cross-infection can be prevented by using chemical disinfectants to reduce the numbers of pathogens in sources such as superficial lesions and carrier sites, and by interrupting routes of spread. Examples are given to show the value of using disinfectants in the light of epidemiological knowledge.

THE MECHANISM AND PREVENTION OF CROSS-INFECTION IN DERMATOLOGICAL WARDS

Over a 2-year period a dermatology department was shown to be a valid model for the long-term study of hospital cross-infection. In the absence of specific anti-bacterial measures, consistently high levels of Staph. aureus and Gram-negative bacilli were found throughout the environment. ‘Broadcasts’ of Staph. aureus were particularly evident in the bathrooms, and notable sites of heavy, cumulative contamination were the communal baths, bedding, settled dust, and the hands of the staff.

Cross-infection of lesions occurred in ninety-four of the 233 ‘uncontrolled’ patients—15 cases being due to Gram-negative bacilli. Autogenous infection occurred in another fifteen cases. Nasal carriage of Staph. aureus developed in fifty-one patients after admission.

In one of the two main wards nasal disinfection (with ‘Soframycin’ nebulizers) was used for 4 months, and was effective in the treatment and prevention of nasal carriage; but it produced no change in the level of environmental contamination or in the incidence of cross-infection—even though efficient cleansing of the baths was also instituted. In contrast, during two separate periods of the work disinfection of skin lesions (with ‘Rikospray Antibiotic’) markedly reduced the counts of pathogens in the environment, and virtually abolished both cross-infection and the development of nasal carriage.

A NEW SELECTIVE BLOOD AGAR MEDIUM FOR STREPTOCOCCUS PYOGENES AND OTHER HAEMOLYTIC STREPTOCOCCI

Horse blood agar containing polymyxin B sulphate, neomycin sulphate, and fusidic acid inhibited the growth of Staph. aureus, Ps. pyocyanea, Proteus mirabilis, E. coli, and Klebsiella pneumoniae but allowed good growth of, and haemolysis by, Str. pyogenes. In a comparison with blood agar, blood 4% agar, and gentian violet blood agar, the selective medium (P.N.F.) yielded a significantly higher proportion of streptococci than the other media, both by aerobic and by anaerobic culture, from burn swab extracts deliberately contaminated with Str. pyogenes; P.N.F. culture was more effective with dilute than with heavy inocula of Str. pyogenes, allowing from three to seven times as many recoveries of Str. pyogenes from swabs contaminated with 10(-3) dilution of streptococcal cultures than cultures of the same material on the other media. Haemolytic streptococci of groups A, C, D, G, and others were isolated by aerobic culture from burns in a consecutive series of 1,277 swabs more often on P.N.F. medium than on blood 4% agar. Viable counts of 12 strains (including 11 different serological types) of Str. pyogenes showed some reduction in the numbers of colonies compared with counts on blood agar, and some strains grew more slowly on P.N.F. medium. These limitations, however, were offset and outweighed by the higher final yield of streptococci on the selective medium.

THE EGG YOLK REACTION OF STAPHYLOCOCCUS AUREUS ISOLATED FROM BURNS

Staph. aureusfrom burns of in-patients were tested for egg yolk reaction during three periods; in 1958 and in 1960 approximately 80 % of the strains gave a negative reaction (EY-), but in 1962 only 36 % of the strains were egg yolk negative.

Staphylococci of phage group III were more commonly EY- than those of other groups isolated from burns. Within each of groups I and III, however, there were patterns predominantly EY- and others predominantly egg yolk positive (EY+); in group I the majority of strains isolated in 1960 were of phage type 52 and EY-, while those isolated in 1962 were predominantly of phage type 80 or related patterns which were always EY+.

Most of the staphylococci in burns were resistant to penicillin, tetracycline and erythromycin; within groups I and III, the staphylococci which were EY- were also more commonly resistant than EY+ strains to these three antibiotics.

Most of the staphylococci from burns were mercuric chloride resistant (presumptive epidemic strains); of the mercuric chloride sensitive staphylococci, the proportion of EY+ strains was greater than that of EY- strains.

Laboratory data from the surveillance of a burns ward for the detection of hospital infection

Nosocomial infection is a major problem affecting many hospital personnel and patients. Surveillance of intensive care areas such as burns wards is important due to the immunocompromised status of the patients. Since infection has been found to be a major cause of death in our burns ward, bacteriological surveillance of the area was carried out over a 1-year period. This indicated the various sources of infection, which included a contaminated container of disinfectant, and transient pathogenic flora on one of the staff members involved in changing dressings. Pseudomonas aeruginosa was the most commonly isolated pathogen from infected wounds as well as from the blood of patients developing sepsis. Autogenous spread of this organism was confirmed by similar pyocin typing results of the strains isolated from wounds, blood and faeces of the patients. Necessary changes were implemented based on these findings and the infection rate was reduced remarkably. The results suggested that strict vigilance by the personnel involved in the care of burns patients reduces the incidence of invasive sepsis and shortens the hospital stay.

Routine burns bacteriology and proteus

On standard agar media Proteus spp. swarm rendering prompt detection of other organisms difficult. Methods for preventing this have been investigated and a simple system devised suitable for inclusion in routine burns bacteriological investigations. Its merits are discussed.

An epidemiological profile and trend analysis of wound flora in burned children: 7 years' experience

A retrospective chart review was conducted of 5418 culture and sensitivity reports from 93 paediatric burn patients to determine profiles of wound flora and invasive organisms, trend analysis and patterns of antibiotic resistance. Coagulase-positive Staphylococcus was the predominant burn wound pathogenic isolate and the predominant invasive organism for burns less than 60 per cent BSA. Pseudomonads were the predominant invasive organism for burn wounds greater than or equal to 60 per cent BSA. Only 7 per cent of all pathogenic isolates were fungi. A significant association was demonstrated between increasing burn size and an increasing incidence of Gram-negative and invasive organisms. Silver sulphadiazine remains a very effective topical agent for the control of bacterial and fungal growth in burn wounds after 10 years of intensive use in this burn unit. Pseudomonad isolates were routinely multi-drug resistant. Pseudomonad isolates from wounds treated topically with a silver sulphadiazine-cerium nitrate mixture were frequently resistant to aminoglycosides, colistin and carbenicillin. It is concluded from this review that severe restrictions on antibiotic usage within burn units, and strict internal environmental control within burn units may help to decrease the incidence of nosocomial resistant strains and cross infection. Regular monitoring of burn wound flora, and the protocol for wound care used in treating these patients have been effective in preventing septic episodes and death due to sepsis.

Assessment of burn wound sepsis by swab, full thickness biopsy culture and blood culture--a comparative study

Fifty patients with burns ranging from 30 to 50 per cent of their body surface area were monitored for sepsis throughout their hospital stay using swab, blood and full thickness biopsy culture techniques. The relative merits of these techniques in the diagnosis of burn wound sepsis were evaluated. Only 62.5 per cent of the patients with a positive surface culture showed signs of clinical sepsis, while 87.5 per cent of the patients with significant bacterial count on biopsy culture showed signs of clinical sepsis. A decrease in bacterial count on follow up correlated with clinical improvement while a count of 10(8) orgs/gm indicated a bad prognosis. Wound surface cultures, though the simplest method gave poor indication of the organisms invading into the burn wound. Blood cultures were of only prognostic value. Full thickness biopsy culture and quantification of the number of bacteria in the burn wound was felt to be the best method for rapid diagnosis and for assessing the progress of burn wound infection.

Staphylococcal sepsis in a burns unit

An outbreak of staphylococcal sepsis in a burns unit occurred between January 1976 and May 1978. Many patients and members of staff had boils, and a number of patients also developed septicaemia. Most of the boils in the early period of the trial and a large proportion of boils in patients during the later period yielded Staphylococcus aureus resistant to penicillin, tetracycline and erythromycin only (PTE), and were shown to be of phage type 95 in the early period while strains were phage typed. From blood cultures, most strains in the early period were of resistance pattern PTE and phage type 95, but in the later period other resistance patterns were predominant. Strains from burns were usually multiresistant (PTEKNML) and of the phage pattern 29/77, which had been endemic in the Unit, but during the early period of the outbreak there was an increased proportion of strains in burns with the resistance pattern PTE and of phage type 95. Staphylococcal sepsis has for many years been very infrequent in the burns unit. This outbreak seems to have been initiated by a strain of phage type 95 and resistance pattern PTE, but during the course of the outbreak the endemic strain of type 29/77 and some other staphylococci seem to have developed enhanced ability to cause clinical infections, conceivably by transduction from the epidemic strain of phage type 95.

"Methicillin-resistant" Staphylococcus aureus: reassessment by controlled trial in burns unit

A controlled trial of oral flucloxacillin (250 mg six-hourly for four days) was performed in 34 patients treated by the covered method whose burns had yielded a heavy or moderate growth of Staphylococcus aureus resistant to methicillin at 30 degrees C but moderately sensitive at 37 degrees C. Staph aureus was eliminated in nine of the 17 patients treated with flucloxacillin but in none of the 17 controls; the proportion of patients from whose burns sensitive Staph aureus was eliminated in an earlier trial of cloxacillin was greater than this. Strains of Staph aureus commonly described as methicillin-resistant and showing heterogeneous growth at 37 degrees C of many sensitive and very few resistant bacterial cells should, in the light of these findings, be called moderately sensitive to flucloxacillin. Such "heteroresistant" strains showed consistent moderate sensitivity in replicate diffusion sensitivity tests at 37 degrees C, but very inconsistent results in replicate dilution tests, especially with flucloxacillin. These studies showed that 18-hour diffusion sensitivity tests indicate the clinical value of treatment with flucloxacillin for staphylococcal infections of moderate severity more correctly at 37 degrees C than at 30 degrees C.

New horizons in surgical immunobiology. Host defence mechanisms in burns

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Protective isolation in a burns unit: the use of plastic isolators and air curtains

The use of plastic isolators and of an ;air curtain' isolator for protection of patients against infection was studied in a burns unit.Preliminary bacteriological tests showed that very few airborne bacteria gained access to a plastic ventilated isolator; even when the filter and pre-filter were removed from the air inflow, settle-plate counts inside the isolator were much lower than those in the open ward, but the difference was smaller in tests made with an Anderson air sampler, which showed also that fewer large bacteria-carrying particles appeared inside the isolator than outside it. An open-topped isolator allowed virtually free access of bacteria from ambient air. The numbers of airborne bacteria inside an air curtain were appreciably lower than the counts of airborne bacteria in the open ward, but not as low as those in the plastic ventilated isolator.Controlled trials of isolators were made on patients with fresh burns of 4-30% of the body surface; the patients were given no topical chemoprophylaxis against Staphylococcus aureus or Gram-negative bacilli. Patients treated in plastic isolators showed a significantly lower incidence of infection with Pseudomonas aeruginosa than those treated in the open ward; this protective effect was shown by isolators with or without filters or with an open top. Ventilated isolators, which protected patients against personal contact and airborne infection, gave a limited protection against multi-resistant ;hospital' strains of Staph. aureus, but no such protection was given by an open-topped isolator, which protected only against personal contact infection, or by air curtains, which protected only against airborne infection; the air curtain gave no protection against Ps. aeruginosa, and there was no evidence of protection by any isolator against Proteus spp. and coliform bacilli.Both the controlled trials and evidence from the bacteriology of air, hands, fomites and rectal and nasal swabs taken on admission and later, supported the view that Ps. aeruginosa is transferred mainly by personal contact, Staph. aureus probably by air as well as by contact and coliform bacilli mainly by self infection with faecal flora, many of which are first acquired from the hospital environment in food or on fomites.The use of plastic isolators is cumbersome, and of limited value except in the control of infection with Ps. aeruginosa. For this reason and because of the effectiveness of topical chemoprophylaxis such isolators are unlikely to have more than an occasional use in the treatment of burns. Though air curtains greatly reduce airborne contamination, their use in a burns unit does not appear to protect patients against infection when the alternative (and, for Ps. aeruginosa, more important) routes of contamination by personal contact and fomites are left open.

Gram-negative bacilli in burns

In a period of two years, 865 strains of Gram-negative bacilli other than Pseudomonas aeruginosa isolated from burns were identified by a range of tests. The commonest species were Proteus mirabilis, Escherichia coli, and Enterobacter cloacae. Many strains of Klebsiella aerogenes, Enterobacter aerogenes, and Bacterium anitratum were also found.A large proportion of the strains were tested for sensitivity to nalidixic acid, ampicillin, kanamycin, chloramphenicol, tetracycline, and carbenicillin, and smaller numbers of strains were tested for sensitivity to cephaloridine, polymyxin, streptomycin, sulphadiazine, sulfamylon, and trimethoprim. The proportion of strains sensitive and resistant to different antibacterial agents varied widely with species of bacteria. A large proportion of the strains of E. coli and P. mirabilis were resistant to ampicillin, which was much used in treatment; resistance appeared least often towards nalidixic acid, kanamycin, trimethoprim, and gentamicin. Multiple resistance occurred less often among strains of E. coli than among Klebsiella spp, Enterobacter spp, and P. mirabilis. Phage and serological typing of Ps. aeruginosa showed that most infections of burns with this organism were due to strains previously found in other patients in the same ward. Taken with other evidence, this supported the view that most infections with Ps. aeruginosa were not acquired from the patient's own flora but from sources in the hospital environment.

Antiseptic and aseptic prophylaxis for burns: use of silver nitrate and of isolators

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Use of an improved cetrimide agar medium and other culture methods for Pseudomonas aeruginosa

In a comparison of two selective media for Ps. aeruginosa containing 0.03% cetrimide, stronger fluorescence was obtained from growth on the medium prepared with King's medium B as the base (CTA 2); although Ps. aeruginosa was not isolated more frequently from burns on this medium than from cetrimide agar made with a Lemco base (CTA 1), results were easier to assess and there were fewer cases of doubtful fluorescence on CTA 2 than on CTA 1. Pyocyanin production on CTA 1 was better than on CTA 2, but for demonstration of pyocyanin production Wahba and Darrell's medium was preferable and showed the pigment in 455/497 (92%) of fluorescent strains of Ps. aeruginosa from burns.A series of tests on 99 strains of Ps. aeruginosa or presumptive Ps. aeruginosa, on 30 strains of other species of Pseudomonas, and on 68 strains of other species of Gram-negative rods showed the value of growth on cetrimide agar and on triphenyl tetrazolium chloride medium, of slime production in gluconate broth, of gas production from nitrate, and of growth at 42 degrees C. as diagnostic aids in the recognition of Ps. aeruginosa.