Phenotypic and Genotypic Characterization of Bacterial Pathogens in Hemodialysis Patients and their Antibiotics Susceptibility

Abstract

This study was carried out in Khartoum State during the period from March 2013 to March 2014, to study phenotypic and genotypic characterization of bacterial pathogens in hemodialysis patients and their antibiotics susceptibility. Two hundred and one blood specimens for culture were collected from patients attended 17 Dialysis Units. The specimens were cultured on Thioglycollate broth which support the growth of anaerobes and aerobes and has been used in modified form for blood culture purposes. The obtained colonies were investigated using VITEK 2 Compact System for bacterial identification and susceptibility testing. During this study, 62 patients showed positive blood culture. Out of them 56 (90.3%) patients had Gram-positive bacterial infections and 6 (9.7%) patients had Gram-negative bacterial infections. Staphylococcus epidermidis was the most common microorganism associated with hemodialysis catheter-related bloodstream infection, it involved 35 of the 62 (56.5%) cases. Other prominent bacteria included six Enterococcus faecalis and six Enterococcus faecium (9.7%), Staphylococcus aureus 4 (6.5%), Pseudomonas aeruginosa 3 (4.8%), Staphylococcus vitulinus, Staphylococcus hominis, Staphylococcus simulans, Streptococcus uberis, Enterobacter cloacae, Serratia marcescens and Escherichia coli (1.6% each). The antibiotic susceptibility results showed that only vancomycin, linezolid, tigecycline and nitrofuranation were fully efficacious against Gram-positive isolates, they were highly resistant to benzylpenicillin (92.9%) and oxacillin (83.9%). While Gram-negative isolates were fully resistant (100%) to ampicillin, ampicillin/sulbactam, cefazolin and cefoxitin. They were all susceptible to amikacin. In attempting to identify of Staphylococcus epidermidis, P. aeruginosa, Enterococcus faecalis, Enterococcus faecium and Staphylococcus aureus strains at the DNA level, Polymerase chain reaction (PCR) was used based on specific primer for 16S rRNA gene. The results showed that PCR was found to be rapid and more sensitive and specific in identification. The presence of class 1 and 2 integrons was tested by PCR using primers specific for the integron integrase genes intI1 and intI2. Class 1 integrase Gene was present in all Gram- negative isolates (6) and in 48 of 56 Gram- positive isolates. The class 2 intI gene was not found in this study. Most integrons were present in the multi-resistant isolates, indicating a general concordance between the presence of integrons gene and antibiotic resistance, and that the integrons have played an important role in the dissemination of antimicrobial resistance in these species.