Multiresistant Methicillin-Resistant Staphylococcus aureus ST5-SCCmec IV and ST30-SCCmec IV Recovered From Cystic Fibrosis Patients

HAIM MS; PENA AMAYA P; DI GREGORIO S; FERNÁNDEZ S; TEPER A; VAZQUEZ M; LUBOVICH S; GALANTERNIK L; MOLLERACH M

Boston

Congreso; ASM Microbe 2016; 2016

American Society for Microbiology

Staphylococcus aureus is an early and commonly observed pathogen in Cystic Fibrosis (CF) that can chronically infect the lungs of these patients. Methicillin-resistant S. aureus (MRSA) colonization in CF patients attending the Hospital de Niños Ricardo Gutiérrez is an increasing problem climbing from 23% in 1995 up to 32% in 2011. Nevertheless, the information about its epidemiological features is limited. Objectives: to analyze the diversity of MRSA isolates recovered from respiratory samples of CF patients. Methods: Antimicrobial susceptibility of a collection of S. aureus isolates belonging to 41 out of 120 CF patients recovered from June 2012 to May 2013 was characterized by Vitek 2 or Mueller Hinton agar + 5% sheep blood. For each patient, only the first MRSA isolate was included, except when isolates with a different resistance pattern were recovered. luk-SF/PV and mecA genes were studied by PCR. Additionally, strains were genotyped by SCCmec typing, PFGE, spa typing and MLST. Results: 57 isolates from 41 CF patients were included. All were mecA positive and 32% PVL positive. 41/57 (72%) isolates harbored SSCmec IV. Among these, 24 (42%) belonged to the main community-acquired MRSA (CA-MRSA) clone complexes previously described in Argentina: Pulsotype A (PA) ST5-SCCmec IVa (16/57) and Pulsotype C (PC) ST30-SCCmec IVc (8/57). The antibiotic resistance rates were: gentamicin (63%-57%), erythromycin (44%-43%), clindamycin (44%-14%), ciprofloxacin (25%-57%) and rifampicin (31%-0%), PA and PC respectively. Multiresistance was detected in 11/24 (46%) MRSA strains, 8 corresponding to PA and 3 to PC. For those isolates related to PA, 53% were spa type t002 and 47%, t311. Among those with PC, the most frequent spa type was t019 (75%).Conclusions: The ST5-SCCmec IVa-PA clone and ST30-SCCmec IVc-PC, were the most frequent CA-MRSA clones recovered in this study. Nonetheless, the rate of multiresistant isolates belonging to these clones was higher compared to what it is reported in non cystic fibrosis patients in our country. These clones could represent an emerging health threat not only to cystic fibrosis patients but also for the general community, as they seem to have originated from CA-MRSA lineages, which are highly transmissible.