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
Posters
  • 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

    Disclosures:

    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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