The four key syndromes
The four syndromes are severe S. aureus pneumonia, S. aureus bone and joint infections with multiple foci, S. aureus osteomyelitis complicated by deep vein thrombosis, and invasive S. aureus infection plus shock.
- Severe S. aureus pneumonia. Investigators at Claude Bernard University in Lyon, France, have done extensive pioneering work on severe PVL-positive S. aureus invasive infections in children. In an early paper, they highlighted the characteristics that distinguish severe PVL-positive pneumonia: it typically occurs in previously healthy children and adolescents without underlying comorbid conditions, and it is often preceded by a influenza-like syndrome followed by an acute severe pneumonia with hemoptysis. Mortality was very high in this early series, with nearly half of the patients being dead within the first several days after admission (Lancet. 2002 Mar 2;359[9308]:753-9).
- Severe osteomyelitis. Investigators at Baylor College of Medicine, Houston, were among the first to observe that osteomyelitis caused by PVL-positive strains of S. aureus are associated with more severe local disease, with multiple affected areas, bigger abscesses, a greater systemic inflammatory response, and more surgeries required compared with osteomyelitis caused by PVL-negative S. aureus (Pediatrics. 2006 Feb;117[2]:433-40).
- Osteomyelitis with deep vein thrombosis. When a child hospitalized for acute hematogenous osteomyelitis due to S. aureus develops difficulty breathing, that’s a red flag for a severe PVL-positive infection involving deep vein thrombosis. Indeed, investigators at the Leeds (England) General Infirmary have reported that deep vein thrombosis in the setting of S. aureus osteomyelitis is associated with a greater than eightfold increased likelihood of a PVL-positive infection (Br J Hosp Med [Lond]. 2015 Jan;76[1]:18-24). Also, patients with PVL-positive osteomyelitis and deep vein thrombosis are prone to formation of septic emboli.
- Osteomyelitis with septic shock. The Lyon group compared outcomes in 14 pediatric patients with PVL-positive S. aureus osteomyelitis and a control group of 17 patients with PVL-negative disease. All 14 PVL-positive patients had severe sepsis and 6 of them had septic shock. In contrast, none of the controls did. Median duration of hospitalization was 46 days in the PVL-positive group, compared with 13 days in controls (Pediatr Infect Dis J. 2007 Nov;26[11]:1042-8).
Treatment
No randomized trials exist to guide treatment, but Dr. Rojo recommends the protocol utilized by the Lyon group: a bactericidal antibiotic – vancomycin or a beta-lactam – to take on the S. aureus, coupled with a ribosomally active antibiotic – clindamycin or linezolid – to suppress the PVL toxin’s virulence expression. The French group cites both in vitro and in vivo evidence that clindamycin and linezolid in their standard dosing have such an antitoxin effect (Clin Microbiol Rev. 2017 Oct;30[4]:887-917).
In addition, Dr. Rojo recommends utilizing any of the commercially available intravenous immunoglobulin (IVIG) products on the basis of work by investigators at Vanderbilt University in Nashville, Tenn., who have demonstrated that these products contain functional neutralizing antibodies against S. aureus leukocidins. This observation provides a likely explanation for anecdotal reports of improved outcomes in IVIG-treated patients with toxin-associated staphylococcal disease (Antimicrob Agents Chemother. 2017 Oct 24;61[11]. pii: e00968-17).
Challenged as to when specifically he would use IVIG in light of the global shortage of immunoglobulins, Dr. Rojo replied: “Not in every invasive S. aureus infection, but in serious infections that are PVL positive. I think if you have a child with one of these four syndromes who is in a pediatric ICU, you should use it. I mean, the mortality is around 30% in healthy children, so you would not stop from giving it. The risk of giving IVIG is very low, no side effects, so I highly recommend it for these severe cases.”
He reported having no financial conflicts.