title: Antimicrobial susceptibility differences among mucoid and non-mucoid Pseudomonas aeruginosa isolates.
abstract: Pseudomonas aeruginosa is one of the most important opportunistic bacteria, causing a wide variety of infections particularly in immunocompromised patients. The extracellular glycocalyx is produced in copious amounts by mucoid strains of P. aeruginosa. Mucoid and non-mucoid P. aeruginosa strains show some differences in their antimicrobial susceptibility pattern. The aim of this study was to investigate the frequency of mucoid and non-mucoid types and their antimicrobial susceptibility patterns isolated from Milad and Mostafa Khomeini Hospital in Tehran, Iran. One hundred P. aeruginosa isolates were collected which all were confirmed by conventional biochemical tests and PCR assay using specific primers for oprI and oprL lipoproteins. Mucoid and non-mucoid types of isolates were determined by culturing isolates on BHI agar containing Congo red and Muir mordant staining method. The susceptibility pattern of isolates against 23 different antibiotics was assessed using MIC sensititre susceptibility plates. Fifty of 100 of isolates were mucoid type, of which 14 isolates were from Mostafa Khomeini Hospital. Frequency of mucoid type of P. aeruginosa in Mostafa Khomeini hospital (70%) was higher than that seen in Milad hospital (45%). The statistical analysis of MICs results showed significant differences in antimicrobial resistance among mucoid and non-mucoid types (non mucoid strains showed more resistance against tested antibiotics). This may be due to the tendency of some antibiotics to attach to extracellular glycocalyx of mucoid strains.
authors.affiliation: Molecular Microbiology Research Center (MMRC), Shahed University, Tehran, Iran.
authors.forename: Parviz
authors.initials: P
authors.lastname: Owlia
authors.affiliation: Molecular Microbiology Research Center (MMRC), Shahed University, Tehran, Iran.
authors.forename: Rahim
authors.initials: R
authors.lastname: Nosrati
authors.affiliation: Department of Pathology and Immunology, Washington University School of Medicine, Barnes Jewish Hospital, St. Louis, MO, USA.
authors.forename: Reza
authors.initials: R
authors.lastname: Alaghehbandan
authors.affiliation: Department of Microbiology, Faculty of Medicine, Iran University of Medical Sciences, Tehran, Iran ; Department of Microbiology, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Abdolaziz Rastegar
authors.initials: AR
authors.lastname: Lari
keywords: Pseudomonas aeruginosa; antimicrobial susceptibility; mucoid/non-mucoid