Higher incidence of perineal community acquired MRSA infections among toddlers.

BACKGROUND: A six-fold increase in pediatric MRSA infections, prompted us to examine the clinical profile of children with MRSA infections seen at Mercy Children's Hospital, Toledo, Ohio and to characterize the responsible strains. METHODS: Records were reviewed of pediatric patients who cultured positive for MRSA from June 1 to December 31, 2007. Strain typing by pulsed field gel electrophoresis (PFT) and DiversiLab, SCCmec typing, and PCR-based lukSF-PV gene (encodes Panton-Valentine leukocidin), arginine catabolic mobile element (ACME) and cap5 gene detection was performed. RESULTS: Chart review of 63 patients with MRSA infections revealed that 58(92%) were community acquired MRSA (CAMRSA). All CAMRSA were skin and soft tissue infections (SSTI). Twenty five (43%) patients were aged < 3 yrs, 19(33%) aged 4-12 and 14(24%) aged 13-18. Nineteen (76%) of those aged < 3 yrs had higher incidence of perineal infections compared to only 2(11%) of the 4-12 yrs and none of the 13-18 yrs of age. Infections in the extremities were more common in the older youth compared to the youngest children. Overall, there was a significant association between site of the infection and age group (Fisher's Exact p-value < 0.001). All CAMRSA were USA300 PFT, clindamycin susceptible, SCCmec type IVa and lukSF-PV gene positive. Nearly all contained ACME and about 80% were cap5 positive. Of the 58 USA300 strains by PFT, 55(95%) were also identified as USA300 via the automated repetitive sequence-based PCR method from DiversiLab. CONCLUSIONS: CAMRSA SSTI of the perineum was significantly more common among toddlers and that of the extremities in older children. The infecting strains were all USA300 PFT. Further studies are needed to identify the unique virulence and colonization characteristics of USA300 strains in these infections.

Differential gene expression of soluble CD8+ T-cell mediated suppression of HIV replication in three older children.

Suppression of human immunodeficiency virus (HIV) replication by CD8+ T-cells (CD8 suppression) contributes to survival in adults and children <1 year. Soluble CD8 suppression can also be seen in some older children with AIDS. The factor responsible, CD8-derived antiviral factor (CAF), acts at the level of HIV RNA transcription. Differential gene expression techniques have been used to define the gene(s) mediating this phenomenon in adults. Recently, CAF has been linked to exosomes secreted by CD8+ T-cells. To compare the gene expression profiles from pediatric patients with each other, with those reported in 2 previous studies in adults and in those reportedly related to exosomes, we used differential gene expression to study three older children with HIV infection, one who did demonstrate soluble CD-8 suppression and two who did not. Eighteen differentially expressed genes were also seen in one adult study (P = 0.002, χ(2) test), and 38 such genes (P < 0.0001, χ(2) test) in a second adult study. In addition, two exosome components and some RNA's related to exosomal proteins were also differentially expressed. In children with HIV infection, we found significant differentially expressed genes that correlated to those previously reported in two studies in adults. Our data also lends some support to the recent identification of CAF with exosomes secreted by CD8+ T-cells.