الفهرس 
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Abstract
Infection in burn patients remains the significant source of morbidity and
mortality. The aggressive use of antimicrobials has significantly improved survival,
but has also led to an increased colonization and infection of pathogens that have
resistance to current therapies.
This study was performed at Menoufia University Hospital to determine
bacterial pathogens frequently causing burn infections in our hospital and their
antimicrobial susceptibility patterns. Also to determine the prevalence of multi-drug
resistance among the isolated pathogens and to evaluate the different risk factors for
the development of burn wound infection.
This study included 105 patients (59 males, 46 females) admitted to burn unit of
Menoufia university hospital. The patient personal history was taken including age
and sex of the patients, residence, occupation, socioeconomic status and duration of
hospitalization. Clinical history was performed to determine degree of burn, TBSA%,
exposure to invasive procedures, and associated complications and co-morbidities.
Burn wound swabs were taken from all patients following cleansing of any
remnant ointments. All swabs were inoculated on blood agar, MacConkey agar,
nutrient agar and mannitol salt agar. Semi-quantitative assessment of bacterial growth
was reported using the four quadrant method to distinguish bacterial colonization
from infection. Isolation and identification were carried out using standard
bacteriological methods.
Detection of methicillin resistant staphylococci was carried out by cefoxitin disk
diffusion method. Vancomycin supplemented agar screening test was done for all
staphylococcal isolates to detect their vancomycin susceptibility pattern that was
confirmed by vancomycin MIC tube dilution method.
Screening for ESβLS and MβLS enzymes was performed according to CLSI
guidelines by disk diffusion method using cefotaxime, ceftazidime, ceftriaxone, azetronam and imipenem disks. Suspected ESβL producing Gram-negative bacilli
were confirmed by double disk synergy method and confirmatory clavulinate
combined disk method. Suspected MβLs were confirmed by imipenem/EDTA
combined disk test and modified Hodge test (MHT).
The results obtained in this study revealed that; the mean age of the patients was
15±17.6 years old. Burn injuries were more common among young age group (< 20
years old) (70.4 %) with statistical significant difference between different age groups
regarding burn injuries but not regarding degree of burn. Burn injuries affect patients
of low socioeconomic status (75.2 %) and patients associated with co-morbiditis
(28.6 %) with statistical significant difference. Non significant statistical data were
found between degrees of burn injuries and gender, residence, occupation, and
smoking.
The majority of burnt patients’ injuries (70 %) were of the 2nd degree while 18 %
were of the 3rd degree, and only 11 % were of the 1st degree. Fire (68 %) and scalds
(22 %) were the main etiological agents for burn injuries. Chemicals caused 6 % and
electrical injuries caused about 4 % of burns. The mean TBSA % in this study was
19.4±17 %. There was significant statistical correlation between TBSA % and
duration of hospitalization.
Regarding bacterial growth assessment using four quadrant method, bacterial
colonization was detected when bacterial growth restricted to 1st quadrant or 1st and
2nd quadrants, while extended growth to 3rd or 3rd and 4th quadrants means bacterial
infections. About 36 % of patients had burn wound infections, while 39 % of patients
had burn wound colonization. About 25 % of burnt patients had no bacterial growth
in their burn wounds.
Bacterial colonization was detected in 45.7 % of patients with complications
while bacterial infection was detected in 44.3 %. Pneumonia was the most prevalent
complication, affected 22.8 % of burnt patients. Significant association was found
between presence of complications and bacterial growth on burn wounds.
About 74 % of patients had bacterial growth on their burn wounds related to using invasive procedures (36 % were infected and 38 % were colonized). One burnt
patient had bacterial colonization without using invasive procedure. About 20 % of
burnt patients using invasive procedures revealed no bacterial growth. There was
significant statistical correlation between bacterial infection (52 %) and duration of
hospitalization (> 3 weeks).
The risk factors for burn wound infections were young age, low socioeconomic
status, abuse of invasive procedures and antimicrobial agents, prolonged hospital
stay, and improper control of burn associated complications and co-morbidities.
The predominant pathogens detected in our study were S. aureus (32.4 %),
Pseudomonas spp. (27.6 %), and CoNS (16.2 %). Gram-negative bacilli caused 50.6
% of burn wound infections. No bacterial growth was detected in 26 (24.8 %) burnt
patients. Fifty one of the cultures showed a single bacterial growth, 26 cultures
showed two bacterial isolates, and 2 of the cultures showed polymicrobial community
consisting of three species.
Regarding MDR bacteria distribution, Gram-positive bacteria presented 32.4 %
(24.8 % and 7.6 % for S. aureus and CoNS, respectively) while Gram-negative
bacteria presented 50.5 % (27.6 %, 9.6 %, 6.6 %, 2.8 %, 1.9 % and 1 % for
Pseudomonas spp., Klebsiella spp., Proteus spp., Enterobacter spp., Serratia
marscenscens and Citrobacter, respectively).
About 63 % of bacterial growth was MDR isolates. Ninety seven percent of
them were isolated from complicated cases and 100% from patients using invasive
procedures with significant statistical relation. There was a significant statistical
relation between MDR bacterial affection and prolonged hospital stay.
About 76.4 % of S. aureus isolates and 47.05 % of CoNS strains were MDR
staphylococci. About 73.5 % of S. aureus were MRSA, while 47.1 % of CoNS were
methicillin resistance CoNS. By vancomycin agar screening method, 32.4 % and 41.2
% of S. aureus isolates and CoNS were resistant to Vancomycin, respectively. By
confirmatory MIC tube dilution method, S.aureus and CoNS showed intermediate
resistant to vancomycin by 14.7 % and 17.6 % and completely resistant by 17.7 % and 23.6 %, respectively.
For ESβLs production, 67.9 % of Gram-negative bacilli isolated from burnt
patients were ESβL producers by disk diffusion method and 58.5 % by confirmatory
combined disk method compared to only 5.6 % by double disk synergy test with
statistical significant difference between results. Pseudomonas spp. were the
predominant ESβL producer by 61.3 % followed by Klebseilla spp. (16.1 %),
Acinetobater (9.6 %), Proteus spp. (9.6 %) and finally Enterobacter spp. which
represented 3.4 % of ESβL producers in this study.
For MβLs production, 77.4 % of Gram-negative isolates were MβLs producers
detected by combined disk screening test compared to 43.4 % MβL producers
detected by confirmatory MHT with significant statistical difference.