Human urokinase, a serine proteinase, potentiates the in-vitro growth of micro-organisms which commonly infect burn patients

Addition of human urokinase, a serine proteinase, to in-vitro cultures of Pseudomonas aeruginosa strain M2 enhanced bacterial growth. The enhancement of growth depended on the dose of urokinase (10-12,500 units) and the enzymic activity of the protein. Other mammalian proteolytic enzymes (trypsin, chymotrypsin, polymorphonuclear leucocyte elastase, thrombin and plasmin) tested did not affect bacterial growth in vitro. Experiments with clinical isolates of Candida albicans, Klebsiella pneumoniae and Staphylococcus aureus from burn patients indicated that urokinase could enhance the in-vitro growth of all of these micro-organisms. However, some strain-to-strain variation was noted in the extent of this enhancement. These results indicate that urokinase, which could be released into burn injury sites from either damaged tissues or inflammatory cells, is capable of enhancing the growth of several micro-organisms that commonly infect patients with thermal injuries, particularly under oxygen-limited conditions and when few micro-organisms are present.

[Relationship between gut origin bacteria and wound infection after thermal injury]

The pUC19 plasmid vector trace with restriction map analysis and fluorescence labelling bacteria method were applied to study the relationship between the gut origin bacteria and wound infection. According to the characteristic of pUC19 plasmid, a special animal model was designed. 110 Wistar rats received 30% TBSA full thickness burns. On hours 6, 12, 24, 48 and day 12 postburn, injured animal were killed. Subeschar tissue homogenates were examined under fluorescence microscope, and bacterial culture, isolation of plasmids and restriction map analysis were also carried out. The results show that during early stage of burns, 32.5% of fluorescence labelling bacteria and 10.81% of pUC19 plasmid vectors could be detected from the subeschar specimens. 12 day postburn, the detectable rage of pUC19 plasmid vector increased to 62.5%. Beside the factor of early colonization, the contaminative route form gut perineum and then wounds should be considered.

Haematology reports of routine blood films in patients with burns

A retrospective pilot study of 99 peripheral blood films from 27 patients with burns is reported. Abnormalities of the granular leucocyte series were more common in the more extensive burns and usually preceded bacteriological evidence of wound pathogens or a clinical decision to take a blood culture. The evidence suggests that a prospective study is needed to determine the possible clinical value of reporting such granulocyte abnormalities. Abnormalities of the myelo-monocytic and lymphocyte cell lines were sufficiently frequent to permit fundamental research of possible relevance not only to patients with burns but in other host responses such as in sepsis, malaria or AIDS.

Beta-haemolytic streptococcal infections in burned patients

Colonization of burn wounds by beta-haemolytic streptococci can lead to the loss of autografts. The present study investigated the beta-haemolytic streptococcal infections in burned patients treated in the Burns Centre of the Emergency Medical Institute 'N. I. Pirogov'. Sofia during a 12-month period (March 1991-March 1992). As many as 117 beta-haemolytic streptococcal strains were isolated in 114 burned patients (52 children and 62 adults). The distribution of the streptococcal strains according to their serogroup was 64 strains (54.7 per cent) group A; 34 strains (29.1 per cent) group B; nine strains (7.7 per cent) group G; five strains (4.25 per cent) group C and five other strains (4.25 per cent) group F. Antibiotic sensitivity tests demonstrated the presence of some differences among the serogroups, especially between groups A and B. The sources of the streptococcal infections were found in 26 (29.2 per cent) of the patients. Epidemiological relationships were established between the strains from one source and the wound swab. For the successful treatment of beta-haemolytic streptococcal infections in burns it is essential to bear in mind the role of non-group A beta-haemolytic streptococci (45.3 per cent according to our study).

Agar well diffusion assay testing of bacterial susceptibility to various antimicrobials in concentrations non-toxic for human cells in culture

Previously, we showed that microbial susceptibility to antimicrobials in concentrations non-toxic for human cells in culture could be tested using the wet disc topical antimicrobial assay. In this report, wet disc assay and agar well diffusion assay results were compared testing the susceptibility of Ps. aeruginosa isolates from burn patients to concentrations of Polymyxin B non-toxic for cultured cells. Both assays were performed on the same agar plates. No differences in results were observed. Further agar well diffusion assay testing showed that susceptibility/resistance could be demonstrated when testing several antimicrobials in concentrations non-toxic for cultured cells against a variety of bacteria isolated from burn patients. Therefore, the more familiar agar well diffusion as well as the wet disc assay can be used to test microbial susceptibility to these concentrations of antimicrobials.

Trichosporon beigelii septicaemia in a burn patient

A patient with Trichosporon beigelii sepsis secondary to a 31 per cent burn is reported. Good results were obtained by treatment with amphotericin B. No other reports of septicaemia due this organism in burn patients have been found by us, although the organism has been reported as a cause of sepsis in cancer patients.

[Delayed fluid resuscitation induced bacterial translocation after lethal thermal injury: role of oxygen free radical injury of intestinal mucosa]

The Present investigation was undertaken to examine the effect of delayed fluid resuscitation (DFR), after lethal thermal injury on oxygen free radical (OFR) injury of intestinal mucosa and its relationship to bacterial translocation. Four groups of gnotobiotic rats with 5 strains of bacteria were studied: sham injury group (control) (n = 6): early fluid resuscitation (EFR) group (n = 24) receiving resuscitation (Parkland) immediately after scald (40% TBSA, third degree); DFR group (n = 24) receiving resuscitation 6 hours after scald; treatment group (n = 12), rats with DFR receiving VitE and VitC treatment before resuscitation 12, 24, 48 and 72 hours after injury, animals (n = 6, at each point) were sacrificed. Plasma endotoxin level, mucosal SOD, GSHPx, MDA and diamine oxidase (DAO) of ileum were determined, and cultures of the mesenteric lymph nodes (MLN), liver, spleen, heart, lung, kidney and blood were done. The level of mucosal MDA and plasma endotoxin and the incidence of bacteria translocation (IBT) to tissues were significantly higher and mucosal SOD, GSHPx, DAO activity significantly lower in DFR group as compared with that in EFR group at most of the time points. In DFR group, mucosal MDA content was negatively correlated with mucosal DAO activity, which correlated positively with plasma endotoxin level and IBT. After treatment with VitE and VitC, mucosal MDA content was decreased, plasma endotoxin level and IBT were significantly decreased, and mucosal DAO activity was significantly increased. Our data indicated that DFR in cases of burn shock can result in OFR injury of intestinal mucosa, disrupting mucosal barrier and promoting translocation of intestinal bacteria and endotoxin.

Molecular epidemiologic study of burn wound infection caused by Staphylococcus aureus in children

115 children with burn injuries were admitted to the Children's Hospital of Chongqing Medical University. Of the 1554 samples, 276 strains of staphylococcus aureus were isolated from the burn wounds and other sites. The rate of burn wound infection caused by S. aureus was 25.2% (29/115). The 54 epidemic strains of S. aureus all carried 1.6 and 1.9 Md plasmid DNAs belonging to phage type 618, and were resistant to at least 10 antimicrobial agents, including oxacillin, cephalothin and cephaloridine, but sensitive to tobramycin and amikacin. Identical plasmid profiles and phage types of isolated S. aureus indicated that a patient carrying a multi-resistant strain of S. aureus in his anterior nares caused an epidemic of S. aureus wound infection in 13 patients. S. aureus isolated from burn wounds of 8 cases were derived from the contaminated hands of their family members.

[Study on puji ointment in treating 628 cases with second and third-degree burns and its decrustative effect]

The treatment of second and third-degree burns in small range with Puji ointment (PJO) application showed an obvious advantage over conventional medicine in ceasing exudate, antihydropism and decrustation (P < 0.01). Experiments on rabbits with third-degree burns treated by PJO with vaseline gauze as control revealed that the pH of the tested animal group became neutral more quickly than the control group, and the same as the healing of burns (P < 0.01). PJO application was found to be markedly effective in reducing exudate, antihydropism, preventing infection and speeding up healing. It also demonstrated that the specific decrustative function existed on third-degree burns in small size.

Gut failure and translocation following burn and sepsis

Sepsis with multisystem organ failure is a major cause of morbidity and mortality in burns. We studied the anatomic, physiologic, and metabolic changes of gut mucosa as a normal barrier against sepsis and systemic inflammatory response after burn and sepsis in the chronic porcine model. Flow probes were placed on the mesenteric and hepatic arteries and portal vein. Catheters were placed in the pulmonary artery (Swan-Ganz), aorta, superior mesenteric, and hepatic veins. After 5 days, baseline data were collected and studied after a 40%, third degree burn. They were resuscitated with Ringer's lactate solution (Parkland formula). Eighteen hours later, Escherichia coli endotoxin (100 micrograms/kg) was administered. All animals were sacrificed after 30 hr. The data were compared to a group of sham animals. Following thermal injury the cardiovascular status was stable. Endotoxin administration decreased systemic vascular resistance index and mean arterial pressure, but increased cardiac index. Mesenteric blood flow, vascular resistance, and oxygen consumption showed a transient fall after endotoxin infusion with 20, 23, and 40% reduction, respectively. These changes were associated with a rise in plasma levels of conjugated dienes. The intestinal ornithine decarboxylase activity was elevated at the end of the experiment, evidence of gut repair. Gut bacteria translocated into mesenteric lymph nodes, spleen, and burn wounds in 50% of the animals. We concluded that bacterial translocation into mesenteric lymph nodes, spleen, and wound is due to gut mucosal failure after burn trauma and sepsis. These pathophysiologic changes may be the result of mesenteric ischemia and reperfusion injury.

Granulocyte macrophage colony-stimulating factor improves survival in two models of gut-derived sepsis by improving gut barrier function and modulating bacterial clearance

OBJECTIVE

The effect of recombinant murine granulocyte macrophage colony-stimulating factor (rmGM-CSF) on survival and host defense was studied using two clinically relevant models of infection that included transfusion-induced immunosuppression.

SUMMARY BACKGROUND DATA

Granulocyte macrophage colony-stimulating factor improves resistance in several models of infection, but its role in transfusion-induced immunosuppression and bacterial translocation (gut-derived sepsis) has not been defined.

METHODS

Balb/c mice were treated with 100 ng of rmGM-CSF or placebo for 6 days in a model of transfusion, burn, and gavage, or cecal ligation and puncture (CLP). Translocation was studied in the first model.

RESULTS

Survival after transfusion, burn, and gavage was 90% in rmGM-CSF-treated animals versus 35% in the control group (p < 0.001). After CLP, survival was 75% in the rmGM-CSF group versus 30% in the control group (p = 0.01). Less translocation and better killing of bacteria was observed in the tissues in animals treated with rmGM-CSF.

CONCLUSION

The ability of rmGM-CSF to improve gut barrier function and enhance killing of translocated organisms after burn injury-induced gut origin sepsis was associated with improved outcome. Granulocyte macrophage colony-stimulating factor also improved survival after CLP.

Thymopentin increases the survival of mice after allogeneic blood transfusion, bacterial gavage, and burn injury

OBJECTIVE

To investigate the effect of blood transfusion on mortality and the incidence of bacterial translocation in mice subjected to thermal burn or bacterial gavage, or both, and to assess the influence of thymopentin on mortality.

DESIGN

Randomly controlled experiments.

SETTING

University departments of surgery, immunology and nuclear medicine.

MATERIAL

235 Balb/c (H-2d) and C3H/HeJ (H-2k) mice.

INTERVENTIONS

8 groups of 20 mice each received: saline infusion (controls), blood transfusion (BT) alone, 20% burn alone, gavage with 1 x 10(10) Escherichia coli alone, BT and gavage, BT and burn, burn and gavage, or BT, burn, and gavage. A further 3 groups of 10 mice were all gavaged with 111In-biotin labelled E coli and randomised to additional BT and burn, BT alone, or burn alone. 98 mice that had had BT, burn, and gavage, were then randomised to receive thymopentin 0, 0.1, 1, or 5 mg/kg/day for 15 days. The impact of the pretreatment with thymopentin on PGE2 concentration was also evaluated in a separate group of 45 mice that received BT, burn, and gavage; or burn and gavage.

MAIN OUTCOME MEASURES

Survival, degree of translocation.

RESULTS

The highest mortality (75%) was in the BT, burn, and gavage group. BT alone significantly reduced survival in burned mice, whereas BT alone or associated with gavage had no effect. Thermal injury had the most influence on bacterial translocation, whereas BT did not increase it. Thymopentin significantly improved survival, particularly in the higher doses. The pretreatment with thymopentin significantly reduced PGE2 concentration after BT, burn and gavage.

CONCLUSION

Burn injury significantly increased mortality in the presence of immune deficiency caused by BT. Thymopentin reduced mortality, possibly by immunomodulation.

Supplementation of an elemental enteral diet with alanyl-glutamine decreases bacterial translocation in burned mice

Although there are many reports of the importance of early enteral feeding in maintaining gastrointestinal integrity and preventing bacterial translocation (BT) following burn injury, no diet has been shown clinically to protect the GI tract postburn. Several studies suggest that glutamine (GLN) may benefit gut integrity following injury, shock and other stress. Unfortunately, the free amino acid GLN is unstable in solution. Alanyl-glutamine (ALA-GLN), a soluble form of GLN, maintains long-term stability in solution and could be supplemented to conventional liquid enteral diets. We studied the effects of ALA-GLN supplementation of the elemental diet Vivonex TEN on effecting BT in mice following 32 per cent TBSA full skin thickness burns. Groups A-D were burned. Group A (30 mice) was fed standard rodent chow, which contains extremely high (clinically non-useable) levels of protein. Group B (51 mice) was fasted 24 h, then fed chow 24 h. Group C (64 mice) was fed Vivonex TEN, and Group D (65 mice) received Vivonex TEN plus ALA-GLN (GLN equivalent, 14 g/l). A control group (Group E) consisted of 22 normal mice (no burn injury, chow diet). Mice were assessed for BT by sterile harvesting and plating of mesenteric lymph node tissue, 48 h postburn. Plates were considered positive if any bacterial growth was noted. Non-burned mice exhibited no BT, while burn-fasted mice showed a 64.3 per cent incidence of BT (P = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Post injury hypermetabolic response and magnitude of translocation: prevention by early enteral nutrition

The relationship between hypermetabolism and bacterial translocation was investigated in guinea pigs receiving a 40% burn. Animals were infused intragastrically with a complete enteral diet or Ringer's solution for 48 h, given 10(10) 14C-labeled Escherichia coli intragastrically, and killed 4 h later. Resting metabolic expenditure (RME), translocation (dpm of the 14C-labeled E. coli) to the portal blood and ileal mucosa, plasma cortisol, and urinary vanillylmandelic acid (VMA) were determined. Enterally fed animals had significantly lower RME, cortisol, VMA, and dpm, but higher mucosal and body weight than the Ringer's group. Disintegrations per minute (dpm) in the blood were positively correlated with RME (r = 0.856), cortisol (r = 0.872), VMA (r = 0.759), and dpm mucosa (r = 0.836) and inversely correlated with mucosal weight (r = -0.883). We conclude that bacterial translocation is reduced by early feeding and is an important cause of hypermetabolism and stress hormone production after burn injury.

The role of systemic antibodies against intestinal Escherichia coli in the prevention of bacterial translocation of Escherichia coli in a burn model in mice

Bacterial translocation (BT) from the gastrointestinal (GI) tract has been proposed to play a role in the pathogenesis of septic complications in severely burned patients. It is well known that severely ill patients such as thermally injured patients may acquire new potential pathogenic microorganisms in the GI tract. Because these patients have no antibodies directed against these acquired microorganisms, BT may be facilitated in these patients. To investigate this hypothesis in a burn model, a study was performed in which two groups of C3H-HeN mice underwent a different period of intestinal overgrowth by a single neomycin-resistant (NR) Escherichia coli strain after oral neomycin-bacitracin treatment. Group I underwent a short period (5 days) and group II experienced a long period (44 days) of intestinal overgrowth before a thermal injury was executed. Two days postburn, plasma antibody titers of IgA, IgG, and IgM isotype against NR E. coli were measured by indirect immunofluorescence (IIF) and BT to various organs was determined by culturing. Although there were no significant differences of BT to organs between the groups, the IgG antibody titer against the NR E. coli strain was significantly increased in group II. Antibody titers of IgA and IgM were not significantly different between the groups. Titers of plasma antibodies of IgG isotype against the intestinal NR E. coli did not correlate with BT. We conclude that increased IgG titers against the NR E. coli used are the result of a longer intestinal overgrowth period and are not associated with prevented or decreased BT.

Hospital-acquired infections in pediatric burn patients

To determine the epidemiologic characteristics of hospital-acquired infections (HAI) in pediatric burn patients, we retrospectively reviewed hospital charts of pediatric burn patients from two similar burn units. All patients less than 18 years of age admitted to the burn unit from January 1, 1980 to July 10, 1988, were enrolled. Charts were analyzed for age, sex, burn injury (type, depth, burn surface area), and hospital course (burn wound therapy, use of indwelling catheters or tubes, infectious complications, antibiotic use, cause of death if patient died). Statistical analysis was done using a logistic regression model. Of the 224 children admitted, 32 (14%) had 58 infections during their stay in the burn unit. There was no significant difference in age, sex, race, burn type or use of wound excision between patients with or without infection. Patients who acquired an infection were more likely to have sustained a > or = 20% full-thickness burn (14/32 vs 3/192 without infection), a smoke inhalation injury (10/32 vs 8/192), or have an indwelling device (29/32 vs 77/192). Thirteen (22%) of the 58 infections were burn wound infections due to Staphylococcus aureus or Pseudomonas aeruginosa, 12 (21%) were urinary tract infections due to Enterobacteriaceae, 11 (19%) were pneumonias caused by S aureus, Streptococcus pneumoniae or Pseudomonas sp, and 10 (17%) were bacteremias caused by S aureus or coagulase-negative staphylococci. The infection rate in pediatric patients hospitalized for burn injury in our study was significantly lower than the infection rate described for adult burn patients. As in adult patients, burn wound infections, pulmonary infections, and catheter-associated bacteremias are the most common infections in burned children. However, urinary tract infections are more frequent in the pediatric population. Risk factors (> or = 20% full-thickness burns, indwelling devices) and causative organisms are similar in both age groups.

Bacterial translocation after burn injury: the contribution of ischemia and permeability changes

Bacterial translocation (BT) has been shown to occur in stress and trauma. In this study, we examined the contribution of altered intestinal permeability (measured with 51Cr-EDTA) and intestinal blood flow (radioactive microspheres) to the loss of intestinal barrier function after burn injury. A 42.6 +/- 0.6% total body surface area scald burn was produced in Sprague-Dawley rats; sham burn animals served as controls. Rats (29 burn and 20 sham burn) were sacrificed 24 h postburn, and mesenteric nodes (MLN), cecum, spleen, and liver were cultured. The incidence of BT was significantly higher in burn compared to shams (MLN, 55 vs. 15%; spleen, 31 vs. 10%; liver, 31 vs. 10%; p < .05). Cecal concentration of Gram-negative bacteria were similar in all rats (5.2 +/- 0.2 x 10(8) colony forming units/g). 5 h postburn, intestinal blood flow decreased significantly in burn (1.60 +/- .20) compared to shams (2.49 +/- .24 ml/min/g, p = .01); at this time, plasma to luminal clearance of 51Cr-EDTA was greater in the burn (.146 +/- .033, N = 9) than in shams (.050 +/- .010 ml/min/100 g, N = 9, p = .001); 24 h postburn, there was no significant difference in intestinal blood flow in sham (2.86 +/- .46, N = 10) and burn rats (2.29 +/- .44 ml/min/g, N = 11); plasma to intestinal lumen clearance of 51Cr-EDTA was similar in sham (.054 +/- .010, N = 11) and burn rats (.051 +/- .006 ml/min/100 g, N = 12) 24 h postburn.(ABSTRACT TRUNCATED AT 250 WORDS)

[Methicillin-resistant Staphylococcus aureus infection and its treatment in burned patients]

Burn wound and systemic infections caused by methicillin-resistant Staphylococcus aureus (MRSA) were analysed in 95 patients. Results showed that both 95 (92.2%) out of 103 strains of Staphylococcus aureus isolated from burn wound and all 17 strains from blood were MRSA. Wound MRSA infection could be found in patients with variety of severity and in any kind of wound, while systemic MRSA infection was often occurred in extensive burn patients. The isolated MRSA were most resistant to cephalosporins and sensitive to vancomycin. In order to control wound MRSA infection, Lysostaphin which is active against these organisms could be used as a topical antimicrobial.

Time course of production of cytokines and prostaglandin E2 by macrophages isolated after thermal injury and bacterial translocation

The relationship of translocation of bacteria from the gut of burned guinea pigs and the in vitro production of tumor necrosis factor (TNF), interleukin (IL)-1 and IL-6, and prostaglandin E2 (PGE2) by lipopolysaccharide (LPS)-stimulated mesenteric lymph node and splenic macrophages was investigated at two early times after thermal injury. Two hr postburn, there was a large number of translocated bacteria in the mesenteric lymph nodes and a large proportion was killed; at 24 hr postburn, there were fewer translocated bacteria, but a large proportion was viable. In some cases, there were very large differences compared to controls in the amounts of TNF, IL-6, and PGE2, but not of IL-1, produced by the macrophages at different times postburn and at different in vitro incubation times. The results suggest that the macrophages were primed by the burn or the translocated bacteria to produce in vitro different and sometimes large amounts of cytokines or PGE2 after further stimulation with LPS. Although there was no direct correlation between production of cytokines or PGE2 and time postburn, the early increased production of PGE2 by splenic macrophages could have depressed the animal's ability to kill translocated bacteria by 24 hr postburn, and could be one of the mechanisms of the cause of systemic infection after burn injury.

[A trial of using Cefobid (cefoperazone) in treating infections of the skin and soft tissues]

A clinical laboratory investigation of cefoperazon in the treatment of 27 patients with burn traumata and purulent necrotic wounds of the soft tissues of various genesis and localization was carried out. The clinical efficacy of the treatment was 75-86.6 per cent. 4 patients with extended purulent wounds of the soft tissues and bone affections were treated with cefoperazon and local application of gentacicol (a dosage form of gentamicin based on collagen with prolonged action) which provided the clinical effect in all the cases. 226 isolates from the wounds, urine, blood, sputum, pleural fluid and other substrates were tested and a rather high activity of cefoperazon against many strains of gram-positive and gram-negative organisms including Staphylococcus spp., Pseudomonas aeruginosa, Escherichia coli, Providencia sp. and Proteus spp. was revealed. The tolerance of the drug in all the cases was good.

Role of early enteral feeding and acute starvation on postburn bacterial translocation and host defense: prospective, randomized trials

OBJECTIVES

To investigate the effect of: a) starvation during the preburn period and b) immediate postburn enteral nutrition on the permeability of the gut to microorganisms and the ability of the host to kill translocated bacteria.

DESIGN

Prospective, randomized, experimental trials.

SETTING

Laboratory.

SUBJECTS

Balb/c mice and Hartley guinea pigs.

INTERVENTIONS

In the first experiment, mice were starved for 0, 6, 12, 18, or 24 hrs before receiving gavage with 10(10) 14C-labeled Escherichia coli and a 20% burn injury. In the second experiment, guinea pigs received a 40% burn injury and were randomized to receive a complete enteral diet (175 kcal/kg/day) or infusion of an equal volume of lactated Ringer's solution via a previously placed gastrostomy for 6, 24, or 48 hrs. After each feeding period, 10(10) 14C Escherichia coli were infused intragastrically. In both experiments, the animals were killed 4 hrs after gavage, and mesenteric lymph nodes, spleen, liver, lungs, peritoneal fluid, and blood were harvested aseptically.

MEASUREMENTS

For each tissue or fluid, the number of viable E. coli and radionuclide counts of the 14C E. coli were measured and the percentage of translocated bacteria that remained alive was calculated.

MAIN RESULTS

In mice, 18 and 24 hrs of preburn starvation increased translocation only to the mesenteric lymph nodes, but it also enhanced bacterial killing in all tested tissues. Guinea pigs that were fed enterally for 6, 24, and 48 hrs postburn had significantly lower bacterial translocation in all tissues compared with animals infused with lactated Ringer's solution. Additionally, enhanced killing of translocating organisms was observed after 24 and 48 hrs of feeding.

CONCLUSIONS

Starvation preburn has different consequences than starvation postburn on translocation and bacterial killing. Postburn enteral nutrition decreases the load of viable bacteria in the tissues via a double mechanism: an initial decreased translocation and a subsequent improved ability to kill bacteria that do translocate.

Clinical burn wound infection caused by L-forms of Staphylococcus aureus

A patient with an infection with the L-form of Staphylococcus aureus occurring in burn wounds is reported. The authors conclude that the infection was attributable to a decrease in the host immunological functions and repeated administration of antibiotics resulting in the development of bacterial L-forms.

Macrorestriction analysis of Pseudomonas aeruginosa in colonized burn patients

The colonization of hospitalized patients by Pseudomonas aeruginosa at an intensive care unit for burn victims was studied over a one-year period. A total of 231 isolates from 12 patients were analyzed by macrorestriction analysis. The results revealed that most patients were infected with only one to three different strains. In several patients Pseudomonas aeruginosa isolates of the same clonal lineage exhibited considerable differences in their macrorestriction fragment pattern. Digestion with further restriction enzymes, however, allowed differentiation between clonal variants due to a high genetic drift and superinfection with a different Pseudomonas aeruginosa strain. Isolates of the same clonal lineage could be isolated from several patients as well as from the patients' environment. Notably, Pseudomonas aeruginosa could be isolated from sedimentation plates. Thus, patients may have been extensively cross-infected on the ward. These data underline the importance of strict infection control measures and of regular surveillance for Pseudomonas aeruginosa by an appropriate typing method, i.e. one that can differentiate strains with high genomic variability.