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:: Volume 7, Issue 4 (Autumn 2018) ::
Arch Hyg Sci 2018, 7(4): 282-287 Back to browse issues page
Evaluation of Bacterial Infection of Burn Wounds in a Burn Center, Qom, Iran
Saeed Shams , Mahdi Ghorbanalizadgan , Saedeh Minoii , Sarallah Shojaei
Department of Bacteriology, Faculty of Medical Sciences, Baqiyatallah University, Tehran, Iran.
Keywords: Burn Wound, Infection, Pseudomonas Aeruginosa, Antibiotic Resistance, Iran
Full-Text [PDF 297 kb]   (119 Downloads)     |   Abstract (HTML)  (594 Views)
Type of Study: Original Article | Subject: Microbiology
Received: 2018/05/22 | Accepted: 2018/11/18 | Published: 2018/11/25
Full-Text:   (47 Views)

Skin is an essential component of the nonspecific immune system that protects the host against pathogens (1-3).
Intact skin is a physical barrier and protects human from pathogenic microorganisms (4).
Contact with fire, hot water, steam, electricity, flame, radiation, or caustic chemicals can cause skin damages and interrupt the immune status, resulting loss of a competent antimicrobial barrier (5,6).
Burns has always been a major problem in many parts of the world and it is estimated that 75% of the total deaths from burns caused by wound infection. Physical damages can destroy the body's defenses that normally prevents invasion of microorganisms (6-10).
Due to disorder of the skin's mechanical integrity and suppresses the immune system, burn patients are more prone to different infections .In these patients, microorganisms especially bacteria and fungi rapidly colonize skin wound surface after damaging. Then, systemic spread may occur which can lead to inflammatory responses and life-threatening complications (11).
Despite the considerable progress of antimicrobial therapy in the last 60 years, the bacterial infections in the burn patients are increasing (12). Although the risk of infection in burns is well known, but in recent decades antibiotic-resistant isolated strains of burn patients have been reported. Thus, the distribution of drug-resistant bacteria has become a critical problem in different parts of the hospitals (13).
The prevention of infection in burn patients is an important challenge because continuous management of the burn wound must be performed (14). In uncontrolled or untreated cases, invasive infections may result in the death of the burned patient (Church, Elsayed et al. 2006).
In a burn wound, the combinations of patient factors (such as age, burn depth, and immune system) and virulence factors related to microorganisms (such as enzymes, toxins, etc.) had an important role in the infection of burn site. Different microorganisms can cause burn infection, but Staphylococcus aureus, coagulase-negative staphylococci (CoNS), Enterococcus spp., Pseudomonas aeruginosa, E. coli, Klebsiella pneumonia, and Enterobacter spp. are the  most common Gram-positive and Gram-negative pathogens identified in burn patients (11,15).
Aims of the study:
The aim of this study was to identify the most isolated bacterial agents from burn patients refereed to a burn center of Qom city and the evaluation of the antibiotic resistance of the isolates.
Materials & Methods

Sample collection and isolation of the bacteria
This study was a cross-sectional study that conducted among 793 patients admitted to Nekoei Burn Center of Qom, Iran, during a three-year period (from May 2012 to November 2014). After obtaining informed consent, sampling was done by wet sterile cotton swabs. The swabs were putted in 5cc of Brain Heart Infusion broth (Merck, Germany) and were immediately sent to the microbiology laboratory. The BHI tubes were incubated at 37°C for 24 hours and next sub-cultured on blood agar, MacConkey agar, mannitol salt agar, and nutrient agar media (Merck, Germany) at 37°C for 18-24 hours.
Identification of isolated bacteria
Preliminary identification of the bacterial isolates was done using conventional methods e.g. Gram staining, colony morphology, pigment production, and haemolysis pattern on blood agar, DNase, coagulase, oxidase and catalase tests. Conventional biochemical tests for Gram-negative bacteria e.g. TSI (Triple Sugar Iron), SIM (Sulfide, Indole, Motility), citrate, MR-VP and oxidation-fermentation test of the isolates were also performed to confirm the genus and species of isolates.
Antimicrobial resistance assay
Antibiotic resistance of bacteria was evaluated according to CLSI guideline (16). The antibiogram test of the isolates was carried out using antibiotic disks (PadtanTeb, Iran), including amikacin (30µg), ceftizoxime (30µg), ticarcillin (75µg), ceftriaxone (30µg), cefotaxime (30 mg), ciprofloxacin (5µg), cephalothin (30µg), trimethoprim-sulfamethoxazole or SXT (25μg), imipenem (10µg), gentamicin (10µg), ampicillin (10µg), piperacillin (10µg), nalidixic acid (30µg), carbenicillin (100 µg), meropenem (10µg), cephalexin (30µg), oxacillin (1µg), penicillin (10U), vancomycin (30µg), amoxicillin/clavulanic acid (30µg), and tetracycline (30µg) on muller-hinton agar (Merck, Germany) at 37°C for 24h.

In this study, 793 patients were included which 84% and 16% of them were male and female, respectively. The highest burns equal to 60% was related to the male with an age range of 19-45 years. The distribution of various age groups is shown in Table 1.
Table 1) The percent of various age groups under study
Age group Percentage
Up to 12 16
13 to 18 16
19 to 45 58
More than 45 10
The lowest and highest degrees totally, during 3 years 45 patients (19.82%) were positive culture. Of the total 301 patients admitted in 2012, 16 cases (5.32%) of them had burn wound infection. In 2013, from 331 patients, 11 cases (3.32%) and in 2014 of 161 cases, 18 patients (11.18%) were identified as positive culture (Fig. 1).

Figure 1) Percent of wound infection in three years.
The most common bacterial isolates isolated were Pseudomonas aeruginosa (66%), coagulase-negative staphylococci (16%), Staphylococcus aureus (12%) and Klebsiella spp. (6%) (Fig. 2).

Figure 2) The frequency of the most common bacterial isolates from burn wound infections
The results of antibiotic resistance showed that the most resistance was observed among isolates of Pseudomonas aeruginosa. High level of resistance was detected against ciprofloxacin at a rate of 93.3% and ceftriaxone amounted to 86.6%. The lowest resistance was also identified against meropenem (6.6%) and cephalexin (6.6%). Full results of the antibiotic resistance pattern of Pseudomonas aeruginosa can be seen in Table 2. Other isolated species were sensitive to evaluated antibiotics.
Table 2) The results of antimicrobial resistance.
Sensitivity (%) 6.6 6.6
(No.) 1 1
Intermediate (%) 13.3 6.6 6.6
(No.) 2 1 1
Resistance (%) 66.6 33.3 46.6 86.6 20 93.3 33.3 60 60 20 13.3 13.3 40 20 6.6 6.6 40
(No.) 10 5 7 13 3 14 5 9 9 3 2 2 6 3 1 1 6
AN; amikacin, CT; ceftizoxime, TIC; ticarcillin, CRO; ceftriaxone, CTX; Cefotaxime, CP; ciprofloxacin, SXT; trimethoprim-sulphamethoxazole, IPM; imipenem, GM; gentamicin, AM; ampicillin, PIP; piperacillin, NA; nalidixic acid, CB; carbenicillin, CF; cephalothin , MER; meropenem, CN; cephalexin, TET; tetracycline.

Infectious diseases are major causes of human mortality. Today drug resistance of the microorganisms has been reported as a serious threat in health systems around the world (17). The incorrect use of first-line antibacterial treatment has led to detection of the resistant bacteria. With failure of therapy, other options may be used which are more toxic, less effective and often expensive for patients. The studies have shown that the hospitalization and the risk of death in patients with resistant infections are progressively greater (18,19).
This project was focused to determine the prevalence of the bacterial pathogens causing infection in burn wounds and to detect antibacterial resistance in the isolated species.
Pseudomonas aeruginosa was dominant species in 793 patients studied, followed by coagulase-negative staphylococci, Staphylococcus aureus, and Klebsiella spp. In performed study by Rezaei et al. shown that P. aeruginosa and Klebsiella were the most common Gram-negative bacteria and S. aureus was the most common Gram-positive organism recovered from the burn patients (20). In another work in Ghana, the predominant Gram-negative and Gram-positive organisms isolated were Pseudomonas spp. (30.2%) and Staphylococcus aureus (2.3%), respectively (21). As shown by studies, P. aeruginosa is well-known as an opportunistic pathogen and with minimal requirements for survival can adapt to a wide range of environmental niches. The organism infected high-risk groups include neonates, patients with cystic fibrosis, burned patients, etc. (22).
In current study, antibacterial susceptibility patterns showed that Pseudomonas aeruginosa were more resistant to antibiotics than other bacteria. Antibiotic-resistant bacteria are difficult or impossible to treat and increasingly have become a global crisis (23).
Mechanisms of antibiotic resistance in bacteria are varied and include Efflux pumps and outer membrane (OM) permeability, antibiotic inactivation, target modification, peptidoglycan and protein structure alteration. The complexity of these mechanisms may be used by P. aeruginosa against antibiotics (18,24). So, reports have shown that P. aeruginosa is difficult to control by some antibiotics (25-27).
The most resistance among isolated P. aeruginosa was related to ciprofloxacin and ceftriaxone, 93.3% and 86.6%, respectively. Ranjbar et al. in Tehran reported that the Pseudomonas aeruginosa strains isolated from burned patients were resistant to ciprofloxacin (65%), ceftriaxone (60%) (28). Among the hospitalized burn patients, Sorkh also detected the Pseudomonas aeruginosa with resistance to ceftriaxone (94.66) and ciprofloxacin (84%) (29).
The lowest resistance was also identified against meropenem and cephalexin. In agreement with our study, Bayram et al. showed that meropenem, amikacin, ciprofloxacin, and cefepime were the most effective drugs against Pseudomonas aeruginosa (13).
In another study in India reported that Pseudomonas aeruginosa resistance to carbapenems (imipenem, meropenem) was 13-19% (30). High-level resistance to amikacin and gentamycin was detected. The performed work by Othman in Sulaymaniyah, Iraq, determined that Pseudomonas were resistant to gentamicin with 85.3% resistance and to amikacin with 57.3% resistance (11).

P.aeruginosa is an alarming increase in resistance to antibiotics in our hospital especially in the Burn Center. A guideline on stewardship of the antibacterial agents should be developed for reducing and preventing of the spread of resistance.

Conflict of Interest:
The authors declared no conflict of interest.

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Shams S, Ghorbanalizadgan M, Minoii S, Shojaei S. Evaluation of Bacterial Infection of Burn Wounds in a Burn Center, Qom, Iran. Arch Hyg Sci. 2018; 7 (4) :282-287
URL: http://jhygiene.muq.ac.ir/article-1-335-en.html

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