1164. Increasing Invasive Methicillin Susceptible Staphylococcus aureus Infections at Texas Children’s Hospital, 2007-2010
Session: Poster Abstract Session: Staphylococcus aureus Infections in Children
Saturday, October 22, 2011
Room: Poster Hall B1
  • IDSA_2011_MSSAfinal.pdf (699.0 kB)
  • Background: Almost 60% of invasive community-acquired (CA) Staphylococcus aureus infections were caused by MRSA (>90% USA300), at Texas Children’s Hospital (TCH) from 2001-2006.  During this same time we also noted a steady increase of invasive CA-MSSA infections (25% USA300). While most invasive USA300 CA-MSSA isolates were pvl+, only 12% of invasive non-USA300 CA-MSSA isolates carried pvl.

    Methods: We identified CA-MSSA isolates from 2007-2010 from our S. aureus surveillance database. The isolates were analyzed by PFGE and by PCR for the PVL genes (lukSF-PV; pvl) and arcA (ACME cassette gene) using previously described methods. Antimicrobial susceptibilities were obtained.  Statistical analyses included Fisher’s exact and chi-square for trend.

    Results: 176 children with invasive CA-MSSA infections were identified; 151 (86%) isolates were available for study. Overall,  CA-MSSA represented 179/352 (51%) of the total invasive CA-S. aureus infections and the proportion of invasive isolates being MSSA increased yearly [2007- 37/95 (39%), 2008-42/86 (49%), 2009-47/90 (52%), and 2010-53/81 (65%) (p<0.001)].  Of 151 analyzed isolates, 35 were USA300 and 116 were of other PFGE patterns. USA300 decreased as a proportion of the invasive CA-MSSA isolates from 10/29 (34%) isolates in 2007 to 6/45 (13%) in 2010 (p=0.02). By PCR, 92/151 (61%) isolates were pvl+; 58 were non-USA300 isolates. None of the isolates carried arcA.  Of the USA300 isolates, 21 (60%) were erythromycin (E)-resistant (R) and 3 (9%) were clindamycin (C)-R; 28/116 (24%) non-USA300 isolates were E-R and 14 (12%) were C-R . Mean age was 7.6 years (range 0.01-21.1), 93/151 (62%) were male. Invasive infections included osteomyelitis (98), septic arthritis (23), pneumonia/empyema (13), myositis/pyomyositis (10), bacteremia (4), lung/retropharyngeal abscess (2), and cellulitis with bacteremia (1).

    Conclusion: CA-MSSA has steadily increased as a cause of invasive SA infections in children at TCH and accounted for 65% of these infections in 2010.  In 2010, 50% of non-USA300 invasive CA-MSSA isolates were pvl+.  The increasing presence of pvl in non-USA300 MSSA isolates suggests an advantage of these genes for the organism and may, in part, explain the rise in invasive CA-MSSA infections at TCH.

    Subject Category: P. Pediatric and perinatal infections

    Kristina Hulten, PhD, Edward Mason, PhD, Linda B. Lamberth, BS, Paula A. Revell, PhD and Sheldon L. Kaplan, MD, FIDSA, Baylor College of Medicine and Texas Children's Hospital, Houston, TX


    K. Hulten, None

    E. Mason, None

    L. B. Lamberth, None

    P. A. Revell, None

    S. L. Kaplan, Pfizer: Investigator, Research support

    Findings in the abstracts are embargoed until 12:01 a.m. EST Thursday, Oct. 20 with the exception of research findings presented at IDSA press conferences.