Stenotrophomonas maltophilia : An Emerging Pathogen in Paediatric Population

INTRODUCTION: Stenotrophomonas maltophilia (formerly Pseudomonas maltophilia/Xanthomonas maltophilia), a Gram- negative, non-fermenting bacillus, is being increasingly recognized as a threatening nosocomial pathogen, associated with significant mortality. AIM: To determine the prevalence of infection, antimicrobial susceptibility pattern and clinical outcome of S. maltophilia in a paediatric population. MATERIALS AND METHODS: This was a retrospective study conducted over a period of eight months, i.e., October 2015 to May 2016. All clinical samples received in the microbiology laboratory during the study period were processed using standard microbiological procedures. S. maltophilia isolates were selected. Antibiotic susceptibility was performed for levofloxacin and trimethoprim-sulphamethoxazole by Vitek 2C system (Biomerieux, France). Average length of stay and mortality caused by S. maltophilia infection was compared with age and sex matched controls without S. maltophilia infection. RESULTS: A total of 16,234 clinical specimens were received in the microbiology laboratory in the study period, with 2,734 pathogenic bacteria isolated. A total of 1,339 (1.7% of total isolates) Gram-negative bacteria were isolated, out of which 414 were non-fermenters. Among the non-fermenters, 23 (5.5%) were S. maltophilia. Out of the 23 isolates, 15 (65.2%) were isolated from blood, 4 (17.3%) were isolated from urine and tracheal aspirate each. A total of 91.3% of strains were susceptible and 8.6% were resistant to trimethoprim-sulphamethoxazole. Total 80% of strains were sensitive and 20% had intermediate susceptibility for levofloxacin. None of the strains were resistant to levofloxacin. Average length of stay of patients with S. maltophilia infection was found out to be 23.3 days as compared to 44.8 days in controls. The average mortality of patients with S. maltophilia infection was found to be same as that of controls (35.2%). CONCLUSION: S. maltophilia is becoming an important nosocomial pathogen and its isolation rate is reported to be increasing. Trimethoprim-sulphamethoxazole still remains the drug of choice but resistance has been reported for this drug as well. As its isolation is increasing, it is important to study the epidemiology, antimicrobial susceptibility profile and clinical outcomes of these isolates.