Microbiologic characteristics and antibiotic resistance rates of diabetic foot infections

Purpose: the purpose of this research was to identify the sociodemographic and microbiological characteristics and antibiotic resistance rates of patients with diabetic foot infections, hospitalized in an emergency reference center. Methods: it was an observational and transversal study. The sociodemographic data were collected by direct interview with the patients. During the surgical procedures, specimens of tissue of the infected foot lesions were biopsied to be cultured, and for bacterial resistance analysis. Results: the sample consisted of 105 patients. The majority of patierns were men, over 50 years of age, married and with low educational level. There was bacterial growth in 95 of the 105 tissue cultures. In each positive culture only one germ was isolated. There was a high prevalence of germs of the Enterobacteriaceae family (51,5%). Gram-negative germs were isolated in 60% of cultures and the most individually isolated germs were the Gram-positive cocci, Staphylococcus aureus (20%) and Enterococcus faecalis (17,9%). Regarding antibiotic resistance rates, a high frequency of Staphylococcus aureus resistant to methicillin (63,0%) and to ciprofloxacin (55,5%) was found; additionally, 43,5% of the Gram-negative isolated germs were resistant to ciprofloxacin. Conclusions: the majority of patients were men, over 50 years of age, married and with low educational level. The most prevalent isolated germs from the infected foot lesions were Gramnegative bacteria, resistant to ciprofloxacin, and the individually most isolated germ was the methicillin resistant Staphylococcus aureus.

Wounds are often initially colonized by microorganisms from the surrounding skin microbiota, the main pathogens responsible for infections usually being Staphylococcus aureus and Streptococcus spp. 5 .
In most severe cases requiring antibiotic therapy, it is necessary to start them empirically, at the moment of diagnosis. Subsequently, daily clinical evaluations and the result of culture and antibiogram allow adjustment to the suitable antimicrobial therapy 3,6 .
Routine culture and antibiogram exams in a certain hospital allows knowledge of the microbiota of that population, subsidizing the development of local guidelines for initial empirical antibiotic therapy, promoting direct impact on treatment success, and even reducing costs, with a stepwise and more logical use of antimicrobials 7,8 . The inappropriate use of antimicrobials during the treatment of diabetic foot infections can aggravate the infection and even lead to the development of bacterial resistance 9 .
In the state of Amazonas, there is lack of studies that analyze the microbiological characteristic and bacterial resistance of infections in foot injuries of diabetic patients. In view of this knowledge gap, we set out to analyze the sociodemographic and microbiological aspects of patients with infected diabetic foot, hospitalized in a reference hospital in the State of Amazonas.  11 classifications. We identified the surgical procedures as debridements, minor amputations (with heel preservation) and major amputations (above the ankle). We also recorded the length of stay and the number of in-hospital deaths.

METHODS
We performed the statistical analysis with simple and absolute frequencies, using the Shapiro-Wilk test for quantitative data and the Pearson's chi-square test for qualitative variables, with a significance level of 5%.

RESULTS
The study sample consisted of 105 patients with complete data collection forms and with biological material obtained for microbiological analysis.
Regarding the sociodemographic characteristics, there was a predominance of male patients, aged between 50 and 70 years old, married, with low level of education and from the city of Manaus (Table 1).  When analyzing the type of surgical procedure, just over half the patients underwent minor amputations (with heel preservation), 40% of them underwent surgical debridement, and seven patients (6.5%), major amputations ( Table 2).

Microbiologic characteristics and antibiotic resistance rates of diabetic foot infections
Proteus mirabilis (12.6%) and Klebsiella pneumoniae (10.5%) were the most isolated Gram-negative specimens, whereas Pseudomonas aeruginosa showed a low incidence (4.2%) in this population (Table 3).    According to the 7th Brazilian Guideline for Hypertension, the prevalence of hypertension is estimated between 50 and 75% in patients with DM 15 . In the present study, hypertension was the most prevalent comorbidity (56.2%), within the range estimated by that guideline.
Hinchliffe et al. 16 19  There has been a constant concern about the increase in multidrug-resistant bacteria since the 90s, with great attention focused on the beta-lactamases or carbapenemases producing Gram-negative germs of the Enterobacteriaceae family, known as MDRO, emerging as one of the major problems in the treatment of infections in diabetic patients 24,29 . We isolated four strains of K. aureus, therefore also resistant to clindamycin. In view of this finding, we point out the need to adapt the initial empirical antibiotic therapy for patients with infected diabetic foot admitted to the Hospital 28 de Agosto.
We therefore propose the association of vancomycin with a carbapenem or piperacillin-tazobactam as an initial empirical antibiotic therapy. Based upon our data, we further highlight the importance of cultures of tissue fragments of the foot lesions of these patients, associated with respective antibiograms, for the adequacy of antibiotic therapy during the treatment of this group of patients, always seeking to reduce the rates of amputations.