Rates of pyomyositis and myositis also have been on the rise at Texas Children’s, and can be correlated to the emergence of CA-MRSA. Among 45 previously healthy children with bacterial pyomyositis or myositis, the cause was S. aureus in 58%. Of 24 community-acquired S. aureus isolates that were available, 15 were MRSA and 9 were MSSA. A total of 16 (including all the MRSA) isolates were found to be USA300, and 17 carried the PVL genes. The presence of MRSA, USA300, and/or the PVL genes was associated with a greater requirement for drainage procedures (Clin. Infect. Dis. 2006;43:953-60).
“Infection of muscles is something we just never saw in the past,” Dr. Kaplan commented.
Pulmonary manifestations are another increasingly common complication of CA-MRSA. An investigation of 70 children with invasive staphylococcal infections at Texas Children’s between 2001 and 2004 showed that 47 had MRSA. Compared with 10 who had MSSA, those with MRSA were more likely to have pneumonia, empyema, lung abscess, and atelectasis. The presence of PVL was associated with abnormal chest image findings in patients with secondary pneumonia (Clin. Infect. Dis. 2005;41:583-90).
Influenza complicated by staph infections is also becoming more common, with most of these cases attributable to MRSA. A study by the U. S. Centers for Disease Control and Prevention comparing pediatric deaths during three influenza seasons revealed that bacterial coinfection increased substantially, from 6% in 2004-2005 to 15% in 2005-2006 to 34% in 2006-2007. Isolation of S. aureus from a sterile site rose from just one case in 2004-2005 to 22 in 2006-2007, of which two-thirds were MRSA. Children with staph coinfection were significantly older and more likely to have pneumonia and acute respiratory distress syndrome than those not coinfected (Pediatrics 2008;122:805-11).
Severe staphylococcal infections also are emerging along with CA-MRSA. In a descriptive report of 14 previously healthy adolescents with severe community-acquired S. aureus infections admitted to intensive care at Texas Children’s with coagulopathy and sepsis, 12 were found to have MRSA and 2 had MSSA. Thirteen also had pulmonary involvement and/or bone and joint infection, four developed vascular complications, and three died. All isolates were identical or closely related to the USA300 clone (Pediatrics 2005;115:642-8).
The typical patient is an adolescent, usually with some trauma to an extremity, who may have underlying osteomyelitis and may develop pulmonary manifestations, and then becomes very ill. “We’ve now had seven deaths due to S. aureus sepsis in otherwise completely healthy children,” Dr. Kaplan said.
Dr. Kaplan (pictured above) has received research grants from Pfizer and Cubist Pharmaceuticals.