Original article
Antimicrobial resistance, virulence factors and genetic lineages of hospital-onset methicillin-resistant Staphylococcus aureus isolates detected in a hospital in ZaragozaResistencia a antibióticos, factores de virulencia y líneas clonales de Staphylococcus aureus resistente a la meticilina de origen hospitalario en un hospital de Zaragoza

https://doi.org/10.1016/j.eimc.2015.01.015Get rights and content

Abstract

Introduction

MRSA population dynamics is undergoing significant changes, and for this reason it is important to know which clones are circulating in our nosocomial environment.

Materials and methods

A total of 118 MRSA isolates were collected from clinical samples from patients with previous hospital or healthcare contact (named as hospital-onset MRSA (HO-MRSA)) during a one year period. Susceptibility testing was performed by disk diffusion and microdilution. The presence of resistance genes and virulence factors were tested by PCR. All isolates were typed by SCCmec, spa and agr typing. PFGE and MLST were applied to a selection of them.

Results

Eighty-three HO-MRSA isolates (70.3%) were resistant to any antibiotic included in the macrolide–lincosamide–streptogramin B group. Among these isolates, the M phenotype was the most frequent (73.5%). One hundred and seven of HO-MRSA isolates (90.7%) showed aminoglycoside resistance. The combination aac(6′)-Ie-aph(2″)-Ia + ant(4′)-Ia genes was the most frequent (22.4%). Tetracycline resistance rates in HO-MRSA isolates were low (3.4%), although a high level of mupirocin resistance was observed (25.4%). Most of the HO-MRSA isolates (approximately 90%) showed SCCmec type IVc and agr type II. Fifteen unrelated pulsotypes were identified. CC5 was the most prevalent (88.1%), followed by CC8 (5.9%), CC22 (2.5%), CC398 (2.5%) and CC1 (0.8%).

Conclusion

CC5/ST125/t067 lineage was the most frequent. This lineage was related to aminoglycoside resistance, and to a lesser extent, with macrolide resistance. The presence of international clones as EMRSA-15 (CC22/ST22), European clones as CC5/ST228, community clones related to CC1 or CC8 and livestock associated clones, as CC398, were observed in a low percentage.

Resumen

Introducción

Las dinámicas poblacionales de SARM están experimentando cambios significativos en los últimos tiempos. Por ello es importante conocer qué líneas clonales circulan en nuestro ambiente hospitalario.

Materiales y métodos

Durante un año, se seleccionaron 118 SARM de muestras clínicas de pacientes con contacto previo con el ambiente hospitalario (SARM de origen hospitalario [SARM-OH]). Las pruebas de sensibilidad se realizaron mediante difusión con discos y microdilución. La presencia de genes de resistencia y factores de virulencia fueron estudiados mediante PCR. Se estableció el tipo de SCCmec, spa y agr en todos los aislados, y en una selección se estudió su relación genética por PFGE y MLST.

Resultados

Ochenta y tres SARM-OH (70,3%) fueron resistentes a al menos un antibiótico del grupo de los macrólidos-lincosamidas-estreptograminas B. Entre estos, el fenotipo M fue el más frecuente (73,5%). Ciento siete aislamientos (90,7%) mostraron resistencia a aminoglucósidos. La combinación aac(6′)-Ie-aph(2″)-Ia + ant(4′)-Ia fue la más frecuente (22,4%). Las tasas de resistencia a tetraciclinas detectadas fueron bajas (3,4%). Se observó un 25,4% de resistencia de alto nivel a mupirocina. Aproximadamente un 90% de SARM-OH mostraron SCCmec tipo IVc y agr tipo II. Se identificaron 15 pulsotipos no relacionados. El CC5 fue el más prevalente (88,1%) seguido de CC8 (5,9%), CC22 (2,5%), CC398 (2,5%) y CC1 (0,8%).

Conclusión

La línea clonal CC5/ST125/t067 fue la más habitual. Esta línea se relacionó con resistencia a aminoglucósidos, y, en menor medida, con macrólidos. La presencia de clones internacionales como EMRSA-15 (CC22/ST22), clones europeos como CC5/ST228, clones comunitarios relacionados con CC1 o CC8 y clones asociados al ganado, como el CC398, se observaron en un bajo porcentaje.

Introduction

Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of human bacterial infections worldwide.1 Currently, MRSA is now endemic in many hospitals and healthcare facilities in industrialized countries.2 The prevalence of MRSA among European countries varies considerably being significantly lower in northern countries (approximately 1 or 2%) than in other European countries (up to 45%).3

In recent years, polyclonal emergence of new clones has been described. Pandemic spread of different hospital-associated MRSA (HA-MRSA) clones, as ST239/SCCmecIII-IV, EMRSA-16 or ST36/SCCmecII (CC30) and ST125/SCCmecIV (CC5) and community-associated MRSA (CA-MRSA) clones, as ST1/SCCmecIV (CC1), USA 300 or ST8/SCCmecIV (CC8), ST30/SCCmecIV (CC30) has been observed.4, 5, 6 To date, livestock-associated MRSA (LA-MRSA) clones has not been frequently identified in hospitals or nursing homes in Europe, although the spread seems to be dependent on the region and the intensity of pig farming.7

In Spain in early twenties, the dominant clone was Iberian clone (ST247/SCCmecI) but over the years this clone has reduced its presence.8 Currently, the most widespread HA-MRSA clone is ST125/SCCmecIV/t067 which is an allelic variant of ST5 pediatric clone.9

MRSA population dynamics is undergoing significant changes due to demographic variations such as immigration and the development of sophisticated and complex health systems (i.e. care of patients with severe underlying diseases and invasive devices in day hospitals, residency in a long-term care facility…).4 For this reason it is more difficult to establish the epidemiology of MRSA infections. The aim of the study was to analyze the molecular epidemiology, clonal lineages, resistance mechanisms and virulence traits of hospital and healthcare associated MRSA clones to understand the epidemiology of these infections.

Section snippets

Setting

The study was performed in the University Teaching Hospital “Lozano Blesa” (Zaragoza, Spain), with 803 beds attending a population of 286,774 inhabitants with 29,506 annual admissions. The study was conducted between July 2009 and July 2010.

Bacterial isolates and patient information

A total of 118 MRSA isolates were collected in our institution from clinical samples belonged to patients with previous hospital or healthcare contact (named as hospital or healthcare onset MRSA, HO-MRSA). HO-MRSA was defined as an isolate cultured from a

Overview and epidemiological data

A total of 118 HO-MRSA isolates were collected from clinical samples during one year. These isolates belonged to 72 male (61.1%) and 46 female (38.9%). The median age and standard deviation of these patients was 75.27 ± 15.06 years old (range 1–96). These isolates were mostly recovered from skin lesions and wounds (60%). The remaining isolates were obtained from lower respiratory tract samples (20%), urine samples (8%), blood (5%), abscesses (4%) and upper respiratory samples (2%). These isolates

Discussion

In Spain, MRSA prevalence has remained stable in recent years. During the course of this study, MRSA prevalence in our hospital was 30.9%, consistent with other resistance rates found in different Spanish hospitals.16, 17 It has been observed that some MRSA clones tend to occur more frequently in certain countries or areas18 while other clones spread worldwide, threatening public health.19 Controlling the infection in hospitals or healthcare centers could reduce the overall prevalence of MRSA,

Funding

This work was supported by Departamento de Ciencia, Tecnología and Universidad del Gobierno de Aragón, Spain (Project DGA-FSE/Grupos consolidados, B24-211130). MGD received a grant from the S.E.I.M.C. (Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica).

Conflict of interest

The authors declare that they have no conflict of interest.

Acknowledgments

We are grateful to Dr. J. Pintado for his help with the GelCompar II® software, Instituto de Investigaciones Marinas, Consejo Superior de Investigaciones Científicas-IIM-CSIC, c/. Eduardo Cabello 6, Vigo, Spain.

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