Study results demonstrate the significant trends of burn wound colonization, enabling targeted antimicrobial escalation policy.

Naiem Moiemen, MBChB, FRCS

For a study published in the Journal of Burn Care & Research, Naiem Moiemen, MBChB, FRCS, and colleagues sought to “investigate the influence of changes in time, infrastructure, and geography on burn wound colonization in patients admitted to our burn center.” The 14-year study reviewed data from a burn center in Birmingham, UK that not only adjusted treatment protocols over time, but also moved its location to a more enhanced environment in terms of layout and facilities. The study was split into two stages; the first took place between October 2004 and June 2010, and the second took place from this date—when the burn center was relocated to the new facility—until August 2018.

The study examined 2,001 patients with burn wounds from whom swab samples were collected. Participants were excluded if they were younger than 16, had non-cutaneous burns, had non-burn blistering dermatologic conditions, or were admitted to hospice or palliative care within 24 hours of hospital admission. Participants had a median length of stay in the hospital of 11 days (interquartile range [IQR], 6-21) and had a 30-day mortality of 4.3%.

An average of four swabs per patient (IQR, 2-10) were collected, resulting in a total of 24,226 swabs with 14,291 organisms detected. The study focused on the first-time growth of specific organisms excluding repeat appearances in the same individual; a total of 3,368 unique organisms we included.

Detected Organism Types

The breakdown of organisms detected in the microbial isolates was 37.8% gram-positive (GP), 36.5% gram-negative (GN), 9.7% fungi, and 16% described as mixed growth.

The most common organism identified in the swabs was Staphylococcus aureus, which appeared in 33.7 per 100 patients affected by colonization. The researchers categorized MRSA as its own growth, appearing in 6.2 per 100 patients. Bacillus spp. Appeared in 11.1 per 100 patients, and Streptococci spp. Appeared in 6.8 per 100 patients.

In terms of GN species, Pseud. aeruginosa was the most common, appearing in 13.1 per 100 patients affected by colonization. Dr. Moiemen and team noted that the second most common group of GN species was comprised of multiple species that were low individually in number but combined to make up a significant portion of the GN species detected. These included 35 Sten. maltophilia isolates, 30 Proteus spp., and 14 Serratia.

Colonization Changes With Time

Based on swabs collected within the first 48 hours of hospital admission, the second burn wound center site (ie, second study period) had lower rates of detected GP organisms compared with the first burn wound center site (52.9% vs 60%; P<0.05). The second site had higher rates of fungal colonization (6.4% vs 1.1%; P<0.001).

Of 20 antibiotic classes, greater resistance to five appeared at the second site—vancomycin (2.3% vs 0%; P<0.05), ampicillin (59.2% vs 53.1%; P<0.05), fusidic acid (69.6% vs 15.8%; P<0.001), trimethoprim (70.1% vs 29.5%; P<0.001), and third generation cephalosporins (63.9% vs 43.1%; P<0.001) (Table). However, nine of the 20 antibiotic classes showed lower resistance at the second site compared with the first site.

Although the study only focused on the colonization of microbial organisms in patient swabs and not biopsies, Dr. Moiemen and colleagues note that studies have shown that colonization often leads to invasive infection and sepsis in patients with burn wounds. “Early effective antimicrobial administration is paramount to survival of septic burn patients,” they wrote. “The observations in this study demonstrate the significant trends of burn wound colonization enabling targeted antimicrobial escalation policy and the effect of an improvement in infrastructure,” which was demonstrated in the progression from the first site to the second site.