Zorgani A., Zaidi M., Franka R., Shahen A.

Burns and Plastic Surgery Hospital, Tripoli, Libya

SUMMARY. Over a three-year period, we analysed 77 patients admitted to the burns intensive care unit of the Burns and Plastic Surgery Hospital, Tripoli, Libya, who were clinically and microbiologically proven to be suffering from septicaemia, and their characteristics are presented. The seventy-seven patients altogether suffered 97 episodes of septicaemia: 62 patients had one episode only, while fifteen had multiple episodes. The organisms were detected in blood cultures as early as 48 h post-admission. Of the 97 episodes, 27 (28%) were due to Staphylococcus aureus, five (5%) to coagulase-negative staphylococci, 40 (41%) to Pseudomonas species, two (2%) to streptococci, six (6%) to coliforms, three (3%) to Candida, and 14 (14%) to more than one organism. Once septicaemia was diagnosed, appropriate therapy was instituted. The apparently high mortality rate of 35 patients (45%) was probably due to a combination of several factors: delayed referral to the Burn and Plastic Surgery Hospital, the occurrence of septicaemia quite early with a major degree of burns (3rd-4th degree), inhalation injury, high percentage total body surface area, and multiple episodes with multi-resistant organisms such as methicillin-resistant S. aureus in seven isolates (25%).

Introduction

The burn wound has been considered one of the major health problems in the world. Infection is one of the most frequent and severe complications in patients who have sustained burns, and particularly thuse in which the burned total body surface area (TBSA) burned exceeds 30%.1,2 According to Lutterman et al.,3 infection is the main cause of death in these patients. It is estimated that up to 75% of deaths following burn injury are related to infection.4,5

Many studies have reported the prevalence of P. aeruginosa, S. aureus, E. coli, Klebsiella spp., Enterococcus spp., and Candida spp.5-8 S. aureus is considered to be the most problematic bacterium in traumatic surgical and burn wound infections.8-12 The incidence of infection in the burn wound is much higher than in other forms of trauma because of the extensive skin barrier disruption and the alteration of immune responses.13 Although infection is one of the commonest causes of morbidity, patient factors such as age, extent of injury, and depth of burn, in combination with microbial factors such as type and number of organisms, determine the likelihood of invasive burn wound infection and may be the source of sepsis - and if this occurs, mortality is never far away.14 According to one report, between 63 and 75% of deaths from burn injuries in different centres were due to sepsis.13

The administration of an appropriate modern antibiotic therapy is therefore an important factor in a patient’s survival. The aim of the present study is to determine type of organisms responsible for septicaemia and the factors that may contribute to burn patient mortality.

Methods

The population studied comprises all the patients who were clinically and microbiologically proven to be septicaemic who were admitted to the burns intensive care unit in the Burns and Plastic Surgery Hospital (Tripoli, Libya). This was a three-year retrospective study (August 1999-August 2002). The records of all patients were collected and reviewed for age, sex, TBSA, degree and type of burn, type of bacteria, and antibiotic susceptibility. Blood for culture was obtained under aseptic conditions. At least two sets of blood cultures were collected for each case. Ten ml blood were added to the bottles containing 40 ml blood culture media and incubated at 37 °C for 7 days or until diagnosed positive. All bottles designated positive were smeared and sub-cultured, using standard diagnostic microbiological methods of micro-organism isolation.15 All negative blood culture results were excluded. A single positive blood culture detected was necessary for a diagnosis of blood stream infection. The detection of the organism in one or more blood cultures from the same patient within one week was defined as a single episode.16 The antibiotic susceptibility of each isolate was tested manually according to the NCCLS recommendations for disc diffusion.17 The susceptibility of S. aureus to methicillin was recorded.

All patients received immediate care and resuscitation therapy with the application of broad-spectrum intravenous antibiotics, followed by appropriate treatment.

Results

Of the 77 patients admitted during the three-year period, there were 31 females (40%) and 46 males (60%) (male:female ratio, 1.5:1; mean age, 27 yr (range, 1-80 yr). The majority of patients (64.9%) were under 30 yr old, and only 10 cases were children (� 10 yr) (Table I). The mean TBSA was 50% (range 10-90%) - two patients had only 10% TBSA.

The aetiologies of the episodes are shown in Table II. Fifty-six patients (86.1%) had flame burns, seven had scalds, one had chemical burns (acid), and one had an electrical burn. Sixty-two patients had only one episode of septicaemia, and fifteen had multiple episodes. The majority, i.e. 72 patients (93.5%), suffered their first episode within the first 2 weeks of their hospital stay. The organisms were detected in blood culture as early as 48 h post-admission.

Table III shows the distribution of bacterial isolates in the 97 episodes: 27 (28%) were due to S. aureus, five (5%) to coagulase-negative staphylococci, 40 (41%) to Pseudomonas spp., two (2%) to streptococci, six (6%) to coliforms, three (3%) to Candida, and 14 (14%) to more than one organism. The microbial combinations of the mixed infections were mostly S. aureus, Pseudomonas spp., and Candida. Methicillin-resistant S. aureus was detected in seven (25%) of the S. aureus isolates.

Table IV shows the overall mortality, i.e. 35 patients (45%), and the combination of factors that may have contributed to their death. Mortality was higher among patients who presented a high percentage (Ž 50%) of burned TBSA (20/40), delay in referral to our hospital (5/7), inhalation injury (11/15), occurrence of multiple episodes (10/15), a high degree (3rd-4th) of burn (5/5); and isolation of multi-resistant bacteria (8/15).

Discussion

Septicaemia is still common in burns patients, even if the aetiological agents of infection in burn patients have changed, as in other nosocomial infections, from a predominance of gram-positive bacteria to a predominance of gram-negatives, such as Pseudomonas, and the presence of yeast, as a consequence of the greater selective pressure of antibiotics.1,18 The occurrence of blood stream infection has increased among hospitalized patients.19

The majority of the population studied (64.9%) were under 30 years old. The mean burned TBSA was 50% (range, 10-90%). Only two patients had a TBSA of only 10% - the great majority had a high percentage. The main cause of burns was fire (88.3%), followed by scald burns (9%).

The study showed that the majority (93.5%) of the burn patients suffered only single episodes of septicaemia, which in most cases occurred during the first two weeks post-burn, as in other findings.20 In all the patients who had multiple episodes of septicaemia, this may have been be due to prolonged hospital stay.

Patients colonized by MRSA are at greater risk of developing septicaemia, which can lead to significant morbidity and mortality.21 This study showed that 25% of cases of S. aureus bacteraemia were due to MRSA, a result comparable with other studies. Among cases of S. aureus bacteraemia reported in England and Wales,22,23 the proportion due to MRSA increased significantly from 2% in 1989 to 13% by 1995, 21% in 1996, and 32% in 1997. In the United States, approximately 25% of cases of S. aureus bacteraemia are caused by MRSA.24 Sanyal et al. found that 92% of septicaemia episodes in Kuwait were caused by MRSA.25 In Saudi Arabia, MRSA was found in 29% cases of S. aureus bacteraemia.26 Our study found that Pseudomonas, which has long been recognized as an important pathogen in burn infection, was responsible for 40% of the burn infections.27 These findings show that Pseudomonas is the leading cause of septicaemia in our burns centre and that this is likely to be due to a general evolving trend of nosocomial infections that are specific only for burns. The majority of Pseudomonas isolates were susceptible to imipenem.

The overall mortality reported in our study was 45%, which is higher than the 35% reported by Pittet et al.28 As said, the apparently high mortality rate was probably due to a combination of several factors that may have contributed to the death of these patients: delays in referral to the Burns and Plastic Surgery Hospital, the occurrence of early septicaemia in major degree burns, inhalation injury, a high percentage of burned TBSA, occurrence of multiple episodes of infection (suggesting the probability of a relationship with prolonged hospital stay), and the presence of multi-resistant organisms (possibly owing to the fact that burn patients are generally immunocompromised and therefore susceptible to infections, as observed by Still et al.).29 Our study suggests that mortality was mainly associated with patients suffering a high percentage of burned TBSA (Ž 50 %), which may have been the main contributing factors to the patients’ death.

Conclusion

Adequate bacteriological surveillance and monitorization from the moment of admission into the burns intensive care unit, in order to diagnose any infection and study the colonization flora, is an important measure in the assessment of the more pathogenic or multi-resistant organisms, such as methicillin-resistant Staphylococcus aureus.

RESUME. Pendant une période de trois ans, les Auteurs ont analyse 77 patients hospitalisés dans l’unité réanimation de l’Hôpital de Brûlures et Chirurgie Plastique à Tripoli, Libye, qui à l’examen clinique et microbiologique résultaient atteints de septicémie. Les caractéristiques des patients sont décrites. Les soixante-dix-sept patients ont eu globalement 97 épisodes de septicémie: 62 patients ont eu un seul épisode, et quinze des épisodes multiples. Il était possible d’observer les organismes dans les cultures du sang même 48 h après l’hospitalisation. Sur les 97 épisodes, 27 (28%) étaient causés par Staphylococcus aureus, cinq (5%) par des staphylocoques négatifs à la coagulase, 40 (41%) à des espèces de Pseudomonas, deux (2%) aux streptocoques, six (6%) aux coliformes, trois (3%) à Candida, et 14 (14%) à plus d’un organisme. Une fois diagnostiquée la septicémie, les Auteurs ont commencé à administrer la thérapie la plus appropriée. Le taux de mortalité apparemment élevé de 35 patients (45%) était probablement dû à une combinaison de facteurs: l’envoi tardif du patient à l’Hôpital de Brûlures et Chirurgie Plastique; la manifestation plutôt précoce de la septicémie associée à un degré élevé de brûlure (3ème-4ème degré); les lésions par inhalation; le pourcentage élevé corporel brûlé; et les épisodes multiples avec des organismes multi-résistants, comme S. aureus résistant à la méticilline, dans sept composés isolés.

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