672. Continued Decline in Community Acquired Invasive MRSA Infections at Texas Children’s Hospital
Session: Poster Abstract Session: They've Been Here a Billion Years! Pediatric Bacterial and Viral Infections
Thursday, October 27, 2016
Room: Poster Hall
  • IDSA 2016_MSSA10132016 final.pdf (818.7 kB)
  • Background: The epidemiology of CA-S. aureus infections is changing with CA-methicillin susceptible Staphylococcus aureus (CA-MSSA) isolates causing an increasing share of both invasive and non-invasive SA infections at TCH. This study characterized this current epidemiology of invasive CA-MSSA infections.

    Methods: The prospective CA-S. aureus surveillance database was queried for invasive SA infections between 2007 and 2014. CA-MSSA isolates were characterized using PFGE, spa typing agr and presence of lukSF-PV (pvl) genes. Medical records were reviewed. Statistical analyses included Fisher’s exact and Wilcoxon test.

    Results: CA-MRSA invasive infections decreased from 61 in 2007 to 20 in 2014 while CA-MSSA caused ~40-50 invasive infections annually and 66% of the invasive CA-S. aureus infections in 2014. (Figure) Similarily, CA-MRSA infections overall decreased from 1461 to 578 infections while CA-MSSA infections fluctuated between 400-650 infections, annually. We studied 296 (82%) of the invasive CA-MSSA infections with available isolates. Mean age was 8 years (range 0.01-18.3), 183 (62%) were male. Seventy-four (25%) isolates were USA300; 88 (30%) were pvl+. Bone and joint infections were most common (242, 82%) and associated with non-USA300 isolates (p=0.005); 74% were pvl-. In contrast, 8 of 12 pneumonia isolates were USA300 (p=0.001) and 11 (92%) were pvl+ (p<0.0001). Among patients with bone and joint infections, USA300 was associated with disseminated disease (13/52 vs 5/190, p<0.0001) and deep venous thrombosis [DVT] (11/52 vs 1/190, P<0.0001). Among a subset of 198 isolates, 75 spa types were identified; t008 (associated with USA300) represented 24% of isolates. Conclusion: Because of continuing decline in CA-MRSA for unknown reasons, CA-MSSA has been the most common cause of invasive CA-S. aureus infections at TCH since 2010. No single strain was a predominant cause of MSSA infections and the frequency of USA300 among the isolates has remained stable. CA-MSSA USA300 was associated with DVT, disseminated infection and pneumonia, similar to the clinical presentations among CA-MRSA. Our findings indicate niche specificity for USA300-pvl positive CA-MSSA isolates, similar to what has been observed among CA-MRSA.

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


    K. G. Hulten, None

    E. Mason Jr, None

    L. B. Lamberth, None

    S. L. Kaplan, Forest Labs: Grant Investigator , Research support and Site-PI for clinical trial unrelated to presented research
    Pfizer: Grant Investigator , Research grant
    Cubist: Grant Investigator , Research grant and Site-PI for clinical trial unrelated to presented research

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