Comparison of Antibiotic Susceptibility Patterns between Serratia marcescens Strain Isolated in 1920 versus 2008

Abstract

Serratia marcescens is a non-pathogenic, saprophytic, Gram-negative bacterium classified as a member of Enterobacteriaceae. It has recently been classified as a nosocomial pathogen, causing infections such as urinary tract infections, lower and upper respiratory tract infections, and septicemia. These nosocomial infections have mostly been detected in intensive care units (ICUs). Though there is a standard treatment for S. marcescens infections, the bacterium has recently exhibited resistance to several antibiotic treatments. This study was conducted to determine the difference between two strains of S. marcescens (1920 and 2008 strains) using antibiotic resistance as the main criterion. In this study, antibiotic susceptibility tests using three classes of antibiotics (beta-lactams, aminoglycosides, and sulfonamides), genomic DNA isolation, restriction fragment length polymorphism (RFLP), and polymerase chain reaction (PCR) were used to evaluate the differences between the two strains. PCR was performed using primers for the integron classes 1, 2, and 3, and the methicillin-resistance gene mecA. Genomic DNA digestions were carried out using EcoRI-HF and Hind III. Both the strains were found to be resistant to the beta-lactams, but susceptible to the aminoglycoside and sulfonamides and both the strains lacked integron elements. However, RFLP of genomic DNA showed differences, suggesting possible variation within the genomic DNA sequences of 1920 versus 2008 strains. ©2014 Oklahoma Academy of Science