Caracterização de genes de virulência em bactérias gram-negativas isoladas de pacientes com pneumonia

Abstract

Pneumonia is an acute and multifactorial respiratory tract disease that affects the lung parenchyma, developing inflammation of an infectious cause. It is a disease known to cause several hospitalizations every year in hospitals, and Ventilator-Associated Pneumonia (VAP or VAP) is one of the biggest causes of hospitalizations and deaths, especially in developing countries. Several bacteria can cause pneumonia, among them those belonging to the ESKAPE group, such as Acinetobacter baumannii, Pseudomonas aeruginosa, Klebsiella pneumoniae and Staphylococcus aureus, which are bacteria that normally show resistance to multiple antimicrobials and are a problem to be treated in hospitals. The expression of genes encoding virulence factors is often linked to the pathogenicity of microorganisms, some examples being adhesins, toxins, invasins, among others. Thus, the objective of this work was to characterize virulence genes in Gram-negative bacteria isolated from samples of respiratory secretions from patients with pneumonia admitted to ICUs of hospitals in São Luís. The work was approved by the Research Ethics Committee of Universidade Ceuma, under the opinion no 766.690/2014. Respiratory secretion samples were obtained for convenience in a laboratory in São Luís, identified by MALDI-TOF and subsequent antibiogram by VITEK (automated) and Kirby-Bauer (manual, gold standard, also called Disc-diffusion) methods. Bacterial DNA was obtained by the boiling method, and then the Polymerase Chain Reaction (PCR) and agarose gel electrophoresis were performed. During two months, 135 samples of tracheal secretions were obtained from 129 patients admitted to ICUs. Of these, a total of 102 were Gram-negative bacteria, from 15 species in total. Most patients were male, with a higher frequency of elderly. A. Baumannii and P. aeruginosa were the most frequent, with 35.3% and 29.4%, respectively. In general, there was greater sensitivity to amikacin, imipenem, meropenem and polymyxin B. However, both showed high rates of resistance to several antimicrobials, including some carbapenems. Other microorganisms, such as Serratia marcescens, were totally resistant to ampicillin and Escherichia coli showed high resistance to ciprofloxacin. Fifteen virulence genes of P. aeruginosa were investigated, being exoS and oprI the most frequent, with 70.0% of the positive samples, followed by phzI (20.0%), exoU (16.7%), toxA (13.3%), phzM and exoT (10.0%), pilA and lasA (3.3%). The apr, pilB, lasB, plcH, plcN and oprL genes were not detected. Due to the ease of genetic transfer between bacteria, the same genes were investigated in A. baumannii and K. pneumoniae, but only oprI gene was positive for one isolated of A. baumannii. However, their effects cannot be ignored, since, combined with resistance genes, they are able to proliferate more easily and make treatment with antimicrobial drugs difficult. In general, the study showed high resistance to antimicrobials, requiring greater attention in hospitals, with good hygiene by the health professionals themselves, in patient management, in prescribing, dispensing and when administering drugs to patients, in order to control bacterial resistance inside and outside hospitals.