Epidemiologic and molecular study of pediatric infections caused by Staphylococcus aureus

Doctoral Dissertation uoadl:2778875 302 Read counter

Τομέας Υγείας - Μητέρας - Παιδιού
Library of the School of Health Sciences
Deposit date:
Doudoulakakis Anastassios
Dissertation committee:
Μαρίζα Τσολιά, Καθηγήτρια, Ιατρική, ΕΚΠΑ
Νικόλαος Σπυρίδης, Αναπληρωτής Καθηγητής, Ιατρική, ΕΚΠΑ
Ίρις Σπηλιοπούλου, Καθηγήτρια, Ιατρική, Παν. Πατρών
Αθανάσιος Μίχος, Αναπληρωτής Καθηγητής, Ιατρική, ΕΚΠΑ
Βασιλική Σπούλου, Αναπληρώτρια Καθηγήτρια, Ιατρική, ΕΚΠΑ
Βασιλική Παπαευαγγέλου, Καθηγήτρια, Ιατρική, ΕΚΠΑ
Ευθυμία Πετεινάκη, Καθηγήτρια, Ιατρική, Παν. Θεσσαλίας
Original Title:
Επιδημιολογική και μοριακή μελέτη λοιμώξεων από Staphylococcus aureus στα παιδιά
Translated title:
Epidemiologic and molecular study of pediatric infections caused by Staphylococcus aureus
Objectives: Staphylococcus aureus (SA) is a well-established multidrug resistant pathogen, whereas community-acquired methicillin-resistant S. aureus (CA-MRSA) infections in children are of major concern. The purpose of this study was to assess the epidemiology, clinical characteristics, antimicrobial resistance patterns and molecular markers of certain S. aureus infections occurred in Greek children with no healthcare risk factors attending a large pediatric hospital in Athens during a ten-year period. CA-MRSA infections (2007-2016), skin and soft tissue infections (SSTIs) caused by mupirocin-resistant-methicillin-susceptible S. aureus strains (2013-2016) and CA-SA pneumonia cases (2007-2014) have been reviewed and studied.
Methods: Cases and resistance patterns of all S. aureus isolates recovered from outpatients and inpatients were reviewed using the laboratory (LIS) and WHONET software. Medical files were reviewed where judged necessary and epidemiological categorization of infections as CA or HA was assigned. Cultures were performed according to the procedures of the microbiological laboratory. Identification of S. aureus was done by conventional methods (colony morphology, catalase test, latex agglutination test). Antimicrobial susceptibility testing was performed by disk diffusion method according the CLSI guidelines. For cefoxitin ambiguous results the latex PBP2a Slidex MRSA Detection Kit (bioMerieux SA, France) was used. A disk approximation test (D test) was used to detect inducible clindamycin resistance. Vancomycin, teicoplanin, linezolid MICs for invasive strains were determined by a gradient MIC method. Genes encoding high level (HLR) mupirocin resistance (mupA), fusidic acid resistance (fusB), ermA, ermC, PVL (lukS/lukF-PV), exfoliative toxins (eta, etb), fibronectin binding protein A (fnbA) were investigated in preserved selected strains by PCRs. Genotyping was performed by SCCmec and agr typing, whereas clonality was determined by PFGE and MLST.
Results: During 2007-2016, 5423 CA-SA infections were recorded. Of these, 119 were invasive, osteoarticular infections were predominant (66, 55.5%), followed by bacteremia (25, 21%) and pneumonia (22, 18.5%). MRSA were 41.2% of invasive infections, strongly associated with pneumonia cases (86.4%, p<0.01). Overall, MRSA declined yearly from 37.3% (2008) to 15.7% (2016). SSTIs accounted for 85.2% of the above MRSA infections. Concurrent resistance to fusidic acid, kanamycin and tetracycline was high (>50%), for erythromycin was 20% (9.45 – 34.9) and for clindamycin 17.8% (8.7 – 33.3).
A total of 437 cases of mupirocin-resistant S. aureus were recorded for 2013-2016. All but 3 isolates were methicillin-susceptible. Impetigo was the predominant clinical entity (371, 84.9%) followed by staphylococcal skin scalded syndrome (21, 4.8%) wheras no abscesses were identified. The number of infections detected annually increased during the study years, especially during the summer months. The percentage of high-level-resistance to mupirocin and constitutive resistance to clindamycin were 99% and 20.1%, respectively. Among 102 representative strains available for molecular investigation, 100 (98%) were mupA- and 97 (95%) fusB-positive, 26/27 (96.3%) clindamycin-resistant strains were ermC-positive, 83 (81.4%) lukS/lukF-positive, 95 (93%) carried both eta/etb genes, 99 (97%) were fnbA-positive. Genotyping of MSSA strains revealed that 96/99 (96.7%) belonged to one main pulsotype 1 classified as ST121.
During 2007-2014, 41 cases of CA-SA pneumonia were recorded (boys, 61%); median age 4.3 months from both pediatric hospitals “P. & A. Kyriakou” and “Aghia Sophia”. MRSA accounted for 31 cases (75.6%). Complications included empyema (25/41, 61%), pneumatoceles (7/41, 17%) and lung abscess (1/41, 2.5%). Intensive Care Unit admission was required in 58.5%. Two deaths occurred (4.9%). Definitive therapy was based on vancomycin with or without other antibiotics (55.9%), followed by clindamycin and linezolid (26.5% each). All isolates were susceptible to vancomycin (MIC90 2mg/l, range 1-2), teicoplanin (MIC90 1.5mg/l, range 0.5-2) and linezolid (MIC90 1mg/l range 0.25-2), whereas 26.8% were resistant to clindamycin. Among 25 studied strains, 20 were mecA-positive, carrying also the fnbA gene. Of these, 90% belonged to ST80-IV/agrIII/lukS/lukF - positive clone. MSSA strains showed polyclonality, 3/5 were lukS/lukF positive and 3/5 fnbA-positive.
Conclusions: CA-MRSA infections have significantly declined among children over the last decade. Resistance to fusidic acid, kanamycin and tetracycline being a phenotypical marker of European ST80 is high among these strains but declines over time too. The spectrum of CA-MRSA infections in children in our area is largely associated with the spread of ST80 clone and their clinical characteristics are similar to those described in other parts of the world where different MRSA clones predominate.Moreover, a newly emerged MSSA clone (ST121) carrying genes for resistance to topical antimicrobials and epidermolysins, causing mainly impetigo was documented. Resistance and rich toxinogenic profile confers to this clone adaptability for spread in the community. SSSS cases were also on the rise due to the aforementioned clone. Pediatricians must be discouraged overprescribing topical antimicrobials in their practice.
MRSA and particularly ST80-IV clone predominated among pediatric CA-SA pneumonia cases. Treatment provided was effective in all but two patients, despite relatively high MIC values of vancomycin and a high resistance rate to clindamycin.
Main subject category:
Health Sciences
CA-MRSA, Skin and soft tissue infections, pneumonia, impetigo, children, Mupirocin, Fusidic acid
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