June 2005

Case

A 4-year-old female with short-gut syndrome is admitted to the hospital for evaluation and treatment for the recent onset of emesis and fever. She has been dependant on total parenteral nutrition since infancy, and currently has a Port-a-Cath in her right subclavian vein (figures 1 & 2).

Her examination was essentially normal for her baseline, and blood cultures were obtained from the port as well as a peripheral site. These cultures grew the same organism, Staphylococcus aureus, which was sensitive to all antibiotics tested (pan-sensitive), including penicillin. The port was removed, and she received 10 days of nafcillin with good clinical response, becoming afebrile and returning to her usual health. She did well for about another two weeks, then became febrile again, and she is not feeling well.

Evaluation this time revealed a new heart murmur, and blood cultures were again found to be positive for the same organism with the same sensitivities. She had an echocardiogram done, which is shown in figure 3.

What Is Your Therapy?

1. High-dose penicillin for six weeks
2. High-dose nafcillin for six weeks
3. Standard-dose nafcillin for six weeks
4. High-dose nafcillin for four weeks

Answer

I tried to get you to take the “nafcillin bait,” and you would not be wrong if you did, but I feel the best answer is #1, high-dose penicillin for at least six weeks.

This child obviously has infective endocarditis, as supported by the bacteremia following a central line, a new heart murmur and an abnormal echocardiogram revealing a large vegetation on the tricuspid valve. Also, knowing that this staph is actually sensitive to penicillin, aqueous crystalline penicillin G sodium becomes the drug-of-choice. The recommended duration of therapy is four to six weeks, but in a case with a large lesion as shown, I would prepare the parents for a longer course of antibiotics. This is why I left out the four-week option for penicillin. One can always reduce the duration if the patient has a rapid response with normalization of the heart exam. We have become so conditioned to think of Staphylococcus aureus to be not only penicillin-resistant, and now methicillin-resistant, that even when we recover one of those isolates (5% to 8%) that is actually penicillin-sensitive, we still often feel the need to treat empirically with nafcillin, or another anti-staph penicillin in spite of sensitivity results. But there really is no reason for it, and it is actually less toxic to use penicillin, which also has a lower MIC when sensitive.

The pathophysiology in this case obviously began with the infection of the central line with the organism, and presumably the tip of the catheter was causing some damage to the valve, producing a nidus of infection. This is actually how researchers sometimes produce bacterial endocarditis in the lab setting. And while the Port-a-Cath has less risk for infection because it is implanted subcutaneously, this case demonstrates that severe infectious complications can still occur. There is also another teaching point that when a child with a line is febrile and bacteremic with S. aureus, the catheter should be removed as soon as possible, as in this case, increasing the chance of successful medical therapy.

The patient presented above had a repeat echocardiogram at the end of therapy revealing disappearance of the lesion (figure 4), and now with more than three years of follow-up, her heart remains well. However, the outcome for some is not as well, as shown in figures 5 & 6, the gross and microscopic findings of a fatal case of staphylococcal endocarditis, complicated by underlying heart disease. Not all cases are due to staphylococcus. Children (and adults) with congenital heart disease may be predisposed to development of endocarditis with the aid of turbulent blood flow, and may be due to unusual bacteria, including those often referred to as HACEK organisms. This acronym stands for Haemophilus species, Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens and Kingella kingae. These organisms have been lumped together because of their similar growth characteristics in the lab and their propensity to infect the heart. Found in the mouth, they typically gain access to the blood stream by the gingivo-dental route.

Regardless of the underlying cause, it should also be obvious that this problem should be followed by a pediatric cardiologist, and with the increasing possibility of more resistant organisms, an infectious disease consultant may also be helpful. There is an enormous amount of data on this very complex condition, much more than can be covered here. I would recommend going to the 5th Edition (2004) of Feigin & Cherry’s Textbook of Pediatric Infectious Diseases, chapter 32 by Jeffrey R. Starke, MD, or chapter 38 by Lisa Saiman, in Long, Pickering and Prober’s Principles and Practice of Pediatric Infectious Diseases, 2nd Edition (2003), to find all you need to know, and more.

Columnist comments

With summer well underway, remember to encourage your patients and their parents at every opportunity to be careful with their various activities. Drownings and near-drownings are already occurring in our community. Sometimes a simple word from the primary provider can make the difference between a teenage driver buckling up and slowing down vs. ending up in the morgue. Also, patients should be reminded to leave the cell phone off while driving, unless they have someone else in the vehicle to answer it or are willing to ignore it until the driver can stop the car to return the call.

Of course every season has its own special set of hazards, but injuries and fatalities due to preventable injuries peak in the summer months. By the way, if you’re going to be giving tetanus boosters to your adolescents for the wide array of injuries they have this time of year, you might want to be aware that there will probably be a new recommendation for these patients to receive a pertussis booster at the same time. There are two vaccine companies applying for licensure of similar tetanus, diphtheria and acellular pertussis vaccines that are formulated for adolescents (Tdap). GlaxoSmithKline will produce a vaccine called Boostrix that was just approved for children from age 10 to 18. (Click here to read the article. ) The Sanofi Pasture vaccine, called Adacel, will be approved for patients ages 11 to 64 if all goes well at the FDA this month. Keep an eye out for these products. This could go a long way toward preventing more cases in young infants, especially those who are unimmunized, or too young to be fully immunized. These vaccines were discussed in some depth in the April issue of this publication.

Lastly, and as usual, I ask that you pray for our troops if you are a religious person. If you’re not, pray for them anyway, it can’t hurt. While fatalities among our soldiers have dropped, they are still at high risk. However, unless there is a mass-casualty event involving American or coalition soldiers, you may not hear about it, as single fatalities have apparently been relegated to news filler-time, or at the end of the ABC Sunday morning show, “This Week” with George Stephanopoulos, who routinely shows a list of names released by The Pentagon of soldiers recently killed. In fact, on a recent popular early morning television talk show, news that was being read of a soldier killed in Afghanistan was interrupted by the host to continue with a joke that was being told prior to starting the news portion of the hour, and the newscaster never got back to the story. I was a bit disappointed, but since I had predicted this, I was not surprised. I looked for the story in the local paper from the day before, the day of and the day after the story was partially told on television, but it never appeared. It is human nature for this to be the way of things regarding the war now, but it still bothers me. So, I thought you might be bothered, too. I guarantee it bothers the families of those soldiers.