BACTERIOLOGICAL PROFILE OF INFECTIONS IN BURNS UNIT - PLASTIC AND RECONSTRUCTIVE SURGERY

The nosocomial bacterial infection being one of the main causes of morbidity and mortality in burn patients, our work aimed on describing the nosocomial bacterial infections in order to establish the bacteriological profile to adapt the antibiotic therapy to our service. This is a retrospective study of 502 bacteriological samples taken from 65 patients hospitalized in the Resuscitation of burns of the plastic surgery department of the CHU Mohamed VI of Marrakech, over a period of 3 years, from January 1, 2016 to December 31, 2018. For this which is characteristic of bacterial infections, the infected sites were mainly the skin (50.1%) and blood (37.7%). The main germs were: Coagulase Negative Staphylococcus (32.1%), AcinetobacterBamannii (13.8%) Staphylococcus Aures (8.45%)


Material and Methods:-
We carried out a retrospective analytical study over a period of 3 years from January 1, 2016 to December 31, 2018 which allowed us to collect the various data concerning the experience of the plastic surgery department with regard to burned infection.
The assays of Vancomycinaemia and Amikacinaemia were carried out by immunological techniques: EMIT technique (Enzyme MultipliedImmunoassay Technique).

Resultats:-Infectious sites:
During the study period, our patients benefited from 502 bacteriological samples from which we were able to identify 351 strains.

Germs found in bacteriological examinations:
Staphylococcus is the most frequently encountered germ in our series; we find 30 cases of golden staphylococci (8.45%), coagulase negative staphylococci (mostly staphylococcus epidermidis) were found 114 times (32.11%).
Klebsiella Pneumoniae, Pseudomonas Aeruginosa and Escherichia Coli also constitute a large part of the germs encountered (Table I). The germ most frequently identified on the cultures of the tips of central venous catheters is Acinetobacter Baumanii which was isolated 5 times (33.33%), followed by Klebsiella Pneumoniae and Pseudomonas Aeruginosa identified 3 times each (20%).

The distribution of germs according to the age of the burn
The germs most frequently identified on the samples taken before D7 of the burn are Staphylococcus Aureus and Staphylococcus with Coagulase negative (48.9%) After D7 of the burn, coagulasenegative staphylococcus (32.4%) is still frequent but there is an increase in the occurrence of infection with non-fermenting BGN (28.8%) and enterobacteria (17.1%).

Antibiotic resistance profile:
Among the 30 Aureus Staphylococci identified, 5 (16.6%) are resistant to Meticillin. We note that no resistance to methicillin was observed on the samples taken before D5 of the burn.
All Aureus Staphylococci in our series are sensitive to glycopeptides.
All the identified SCN strains identified on our samples are multiresistant but they remain sensitive to glycopeptides.
Regarding enterobacteria, We mainly studied the sensitivity to C3G. However, they are sensitive to Amikacin, Imipenem, and colistin.

Discussion:-
In our study, the skin site is the most frequent: it represents 50.1% of nosocomial infections. It is the least frequent in the study by Badetti [2] and Wurtz [3]. In the work of Cremer [1] and Taylor [19], skin infections are also the most frequently encountered. The low incidence of skin infections found by Wurtz [3] (3% of infections) is attributed to the common practice of excision of early transplant surgery.
The predominance of skin infection in our series can be correlated with the high frequency of skin samples compared to other studies or to manual delivery and the rules of asepsis which are sometimes forgotten.
In our study, the isolates were mainly composed of Staphylococci (SA and SCN) representing 41% of the total isolates, this predominance of Staphylococci, also reported by certain studies [4][5], is not confirmed by others [6][7] where Pseudomonas aeruginosa is the predominant germ. The frequency of isolation of Acinetobacter baumannii in our study was 13.8%. The emergence of Acinetobacter baumannii is reported by numerous studies which report an increase in its incidence from 0.83% to 14.5% in five years [8][9]. It testifies to the colonization then to the infection of burned patients from the environmental flora where this bacteria is able to resist several months [10,11].
Bahemia [12] finds a predominance of Acinetobacter Baumanii followed by Pyocyanic and then MRSA in blood cultures. This difference from our series can be explained by the high predominance of SNA linked to aseptic faults during sampling and which is not always pathogenic.
Lesens [13] reports that only 12-25% of SCN positive blood cultures are bacteremia. To make sure that it is an infection, you must: Have clinical signs of sepsis and have at least 2 blood cultures taken at different times under good aseptic conditions. The germs most frequently identified on the cultures of central catheters are the BGN contrary to the literature which describes a predominance of staphylococci. The place occupied by Gram-negative bacilli is more and more important, in particular when the catheters are inserted in the lower cavity territory [14].
The authors differentiate early infections occurring less than 7 days after the burn from late infections occurring more than 7 days.
According to this scheme, in our series, the germ most frequently encountered in early infections is Staphylococcus Aureus. The results of our study are then similar to what is found in the literature.
As for late infections, they are most often caused by CNS, non-fermenting BGN and enterobacteria. Indeed, Bahemia reports that Acinetobacter Baumanii is isolated on average on D16 of hospitalization and Pseudomonas Aeruginosa is isolated on D12 on average.
This difference in bacterial ecology depending on the time it takes for the infection to settle guides the clinician in his choice of probabilistic antibiotic therapy.
Concerning the resistance profile of germs found to antibiotics, The associated resistance complicates the management of S. aureus infections justifying the treatment with glycopeptides for late infections.
The MRSA rate in our series is lower than that reported in a multicenter study of S. aureus isolates from skin and soft tissue infections in the USA (44.4%), Europe (32.4% in Spain, 34.7% in France) , 41.8% in Italy ...) [15], in China (66%) [20] than in Tunisia (41%). [16]  The resistance of Acinetobacter baumannii to imipenem is 75%. This high resistance rate to the imipenem of Acinetobacter baumannii isolates poses a real problem in our training and also in all Moroccan university hospitals.This situation is linked, among other things, to an uncontrolled prescription of this molecule selecting resistant strains and to a lack of control of nosocomial infection especially in hot departments.
It is noted that only 27% of the strains of P. aeruginosa presented a resistance to Ceftazidime and Ciprofloxacin it is the antibiotic most, this is comparable to a recent study of 2017 where Ceftazidimere represented the antibiotic of the family of most effective betalactamines with a sensitivity of 78% associated with a sensitivity to ciprofloxacin of 75%. [16] In our series, 718% of the strains of enterobacteria secrete ESBL broad spectrum betalactamases.
The rate of ESBL varies from one burn unit to another. For example, G. Khorasani et al [17] found a rate of 80.4% while that of Hamid Karimi E. et al [18] found 37%.
None of the enterobacteriaceae strains isolated in our center were resistant to imipenem. Resistance to imipenem has been described in enterobacteria recently with the production of carbapenemases . The emergence of enterobacteriaceae resistance to carbapenems is linked to the uncontrolled use of carbapenems motivated by the very high rates of ESBL enterobacteria. This vicious circle will lead to a therapeutic impasse.
In the light of our study, it is therefore necessary to establish a suitable therapeutic protocol in order to optimize the probabilistic antibiotic therapy established in burn patients infected with resuscitation of burn victims in the plastic surgery department of the CHU Mohamed VI. This antibiotic therapy must concern patients with serious infections and whose life prognosis is committed, therefore requiring immediate care. For burns of lesser severity, therapeutic management should preferably refer to bacteriological documentation.
The probabilistic therapeutic scheme proposed for invasive infection in burn victims could be : Infection prećoce : A considérer le SASM principalement + Entérobactéries sensibles aux C3G C3G + Aminoside • Late infection: Consider MRSA, AcinetobacterBamannii and Pseudomonas aeruginosa Imipénème + Amikacine + Vancomycine 1. A clinical-biological reassessment of antibiotic therapy is necessary after 48 to 72 hours to judge the effectiveness of the prescribed probabilistic antibiotic therapy. 2. An adaptation of the antibiotic therapy is essential upon reception in the antibioticogram, whether in the context of therapeutic de-escalation or to broaden the spectrum of activity.

Conclusion:-
Burns represent an excellent bacterial culture medium, infection in burns is therefore a compulsory and inevitable phenomenon. Knowing the bacterial flora of the burn will allow us to reduce this risk as much as possible. Good vigilance with a rigorous application of hygiene measures and epidemiological surveillance of bacteria are necessary, at the scale of burn unit and hospital, to better guide probabilistic antibiotic therapy.