Mucoid Pseudomonads in Patients With Noncystic Fibrosis Bronchiectasis

Abstract

To the Editor: Mucoid Pseudomonas aeruginosa is isolated in up to 40% of noncystic fibrosis patients with chronic bronchitis and other obstructive lung diseases.1 Apart from P. aeruginosa, mucoid strains of other species of pseudomonads are infrequently discussed; and in most of the laboratories that lack automated systems, their identification is not attempted and is reported as "Pseudomonas species not aeruginosa." Mucoid pseudomonads are lung colonizers in patients with bronchiectasis and frequently cause secondary infections leading to increased mortality and morbidity.2 In this study, we have characterized and determined the antimicrobial susceptibility of mucoid pseudomonads strains, isolated from sputum of adult patients with noncystic fibrosis bronchiectasis using simple biochemical tests, which are routinely available in a microbiology laboratory. Antimicrobial susceptibility testing and metallo-β-lactamase production were done using standard methods.3 A total of 97 strains were isolated from 871 sputum samples during the study period. Among them, P. aeruginosa (n = 49, 50.5%) was the commonest isolate, followed by Pseudomonas fluorescens (n = 15), Pseudomonas putida (n = 8), Pseudomonas pseudoalcaligenes (n = 5), Brevundimonas vesicularis (n = 5), CDC group Vb-3 (n = 4), Pseudomonas spp group 1(n = 3), Pseudomonas mendocina (n = 2), Burkholderia cepacia complex (n = 2), Ralstonia pickettii (n = 2), Pseudomonas luteola (n = 1), and Brevundimonas diminuta (n = 1). Antimicrobial susceptibility pattern showed that majority of isolates were multidrug resistant, and polymyxin B was found to be most effective antibiotic. Metallo-β-lactamase production was determined in 19 meropenem resistant strains, and 12 (63%) of 19 isolates were metallo-β-lactamase positive (Table 1).TABLE 1: Antimicrobial Susceptibility Pattern of the Common Mucoid Pseudomonads IsolatesAmong pseudomonads, P. aeruginosa is the most common human pathogen. The first report of mucoid P. aeruginosa isolation came in 1927 from a patient with a fistulating abscess of the gallbladder.2 In the first detailed study, Elston and Hoffman4 reported an incidence of mucoid forms as 1.7%, and Fujita et al5 were the first worker to report mucoid P. putida causing pulmonary infection in an immunocompetent host. Generally, "Pseudomonas non-aeruginosa" species are considered as environment contaminant; however, results of this study indicate that Pseudomonas non-aeruginosa constituted 49.5% of mucoid pseudomonal isolates in patients with bronchiectasis and are an emerging cause of respiratory infections in patients with bronchiectasis. Antimicrobial resistance among them is of increasing concern as not only P. aeruginosa but also other pseudomonads were also found to be multidrug resistant, and these probably demonstrate the changing pattern of antimicrobial resistance in pseudomonads. Further large-scale studies are required to look for epidemiological distribution of mucoid strains and study their antimicrobial susceptibility pattern. Atul Garg, MD, DNB S. Sujatha, MD Jaya Garg, MD, DNB Nasreen H., MSc S. C. Parija, MD, FRCPath Department of Microbiology Jawaharlal Institute of Postgraduate Medical Education and Research Pondicherry, India [email protected]