Antimicrobial resistance and putative virulence genes of Pseudomonas aeruginosa isolates from patients with respiratory tract infection

Headnote

Abstract

Introduction Pseudomonas aeruginosa is a common agent causing community acquired and nosocomial respiratory tract infections, with particularly life-threatening manifestations in patients who are immunocompromised of who have cystic fibrosis. This study investigated the occurrence of extended-spectrum β-lactamases (ESBLs) and metallo β-lactamase (MBL) in association with important putative virulence genes and genotypes variation among P. aeruginosa isolates from respiratory tract infection of Jordanian patients.

Methods Over a period of 8-month, a total of 284 respiratory tract samples were obtained from patients diagnosed with respiratory tract infection while attending the Pulmonary Clinic/Intensive Care Unit, Jordan University Hospital (JUH). At the time of sampling most were inpatients (86.9%). Samples were cultured specifically for P. aeruginosa.

Results A total of 61/284 (21.5%) P. aeruginosa isolates were recovered from respiratory samples of patients. The percentage of MDR P. aeruginosa isolates was 52.5%, and all isolates were susceptible to colistin with lower rates of susceptibility to other tested antibiotics. Positive genes of b/a_CTX-M, bla_VEB, b/a_TEM, bla_GES and bla_SHV were detected in 68.9%, 18.9%, 18.9%, 15.6% and 12.5% of isolates, respectively. Genotyping revealed no significant genetic relationship among MDR P. aeruginosa isolates from hospitalized patients as judged by the constructed dendrogram and the presence of 14 genotypic groups. The percentages of the virulence genes algD, lasB, toxA, exoS, and exoU among P. aeruginosa isolates were 98%, 98%, 80%, 33% and 33%, respectively, and 87% of isolates produced pyocyanin.

Conclusion The present study demonstrates high occurrence of MDR P. aeruginosa isolates carrying blaCTX.M genes. No specific associations were found between antibiotic resistance, virulence genes and genotypes among MDR isolates.

Keywords P. aeruginosa, antimicrobial resistance, virulence factors, respiratory infections, Jordan patients.

Introduction

Pseudomonas aeruginosa respiratory infections are causing high morbidity and mortality due to the germ's capacity to rapidly develop antibiotic resistance, especially during antibiotic treatment of patients. The organism can carry a variety of putative virulence factors, which are highly controlled by cell-to-cell signaling systems.1-2

P. aeruginosa can secrete an exopolysaccharide called alginate (algD) and an elastase B (lasB) enzyme in response to environmental conditions. Both these virulence factors can influence pathogenesis by enhancing adhesion, colonization, and invasion of tissues, causing chronic pulmonary inflammation.3 Additionally, elastase B is an important protease of aeruginosa....