More summer infections and injuries

The guest columnist this month is Diane Di Maggio, MD, describing an unusual infection in her daughter, Alexandra.

About a year ago, Alexandra was an 18-year-old college student who was stung by a stingray on the medial aspect of her left ankle while participating in a marine science class along the Gulf Coast of Florida.

She experienced immediate, excruciating pain and was taken to the local emergency room (ER) for treatment, where the area was cleaned and immersed into hot water.

Plain radiographs were obtained to rule out any retained foreign body and she was continued on some oral cefpodoxime (an oral third- generation cephalosporin) that she happened to already be taking for a sinus infection. However, five days later, the healing wound began draining pus and she returned to the ER for additional drainage and packing. At this time, her antibiotic treatment was changed to ciprofloxacin. However, four days later, the area continued to show signs of spreading cellulitis and lymphangitis (Figure 1, eight hours before admission). As her condition continued to worsen she was admitted to the hospital.

Her past medical history is that of a normal adolescent, with up-to-date immunizations. She is allergic only to penicillin.

Examination on admission revealed a healthy girl with normal vital signs and a normal examination except for an area of painful swelling and spreading erythema of the left ankle, foot and shin, as shown in Figures 2 – 4. Therapy with intravenous vancomycin plus levofloxacin (an advanced-generation flouroquinolone) was begun. Cultures were obtained, but never grew an organism.

Although she complained of chills 24 hours before admission, she never had a documented fever, and after two days of IV vancomycin and levofloxacin, with improvement noted, she was discharged home to complete an additional week of oral levofloxacin. With clinical improvement noted on follow- up, the antibiotic was stopped; however, three weeks later the wound began to drain again. At that time, she had additional imaging with plain radiographs and ultrasound that did not reveal any retained foreign material. Another culture was obtained and ciprofloxacin was started again. Again, the culture was negative, and the wound was draining 10 days into treatment.

What’s Your Diagnosis?

1. Methicillin-resistant Staphylococcus aureus infection
2. Retained barb from stinger
3. Retained necrotic tissue
4. Aeromonas hydrophila infection

After 11 days of antibiotics, she underwent debridement of necrotic tissue (answer C) and the infection healed without further complications (Figure 5).

This is an excellent case that demonstrates the effects of the trauma of the stinger itself, the infectious complications of a penetrating, water-related injury and the necrotic effect of the venom of the animal, which is a heat-sensitive protein that can be denatured, or at least diminished by warming the injured area as much as the patient can tolerate (would need to be about 115º F) for 60 to 90 minutes. One must be careful not to burn the patient while trying this form of therapy. Debridement of any foreign material (stinger, clothing, etc.) is equally important, and if needed, should not be delayed by the prolonged application of heat. However, sometimes it is very difficult to know how much venom was injected and how much damage it may have caused to the soft tissues about the injury until some time has past.

Ultimately, regardless of antimicrobials given, if necrotic tissue is present, the sore will continue to drain due to persistent inflammation until the dead tissue is removed, which this case demonstrates well.

A retained foreign body will do the same thing, but as in the case presented, with multiple imaging studies, this was essentially ruled out.

The infectious complications are obvious.

Many organisms have been recovered from such injuries, but the most common organisms, like most other soft tissue infections are Gram-positive cocci (Staphylococcus aureus and group A streptococcus). However, unusual water organisms such as Vibrio species and Aeromonas hydrophila are also seen as causes of infections with these water injuries.

Therefore, all these should be kept in mind when deciding on empiric therapy of an infection or for prophylaxis, if used. Usually a quinolone and a third- generation cephalosporin would be reasonable. With MRSA being more common, empiric therapy should probably cover that as well, but eventually, you cannot prophylax for the entire world of microorganisms, and you just have to use close follow up. If a wound gets infected, let a culture be your guide. When the cultures are negative, it is either because of the suppressive effect of prior antimicrobial therapy, the lab not suspecting an unusual organism and, therefore, not using appropriate selective culture media, or the drainage may be sterile and simply due to necrotic tissue.

If this infection was due to MRSA or methicillin-sensitive Staphylococcus aureus (MSSA), I would have expected growth on at least one of the cultures. Group A strep (GAS) should have also grown on either of the cultures as long as they were obtained before antibiotics were begun. In my experience, GAS is difficult to recover after even one dose of an effective antibiotic.

Vibrio species requires selective media, but Aeromonas hydrophila will usually grow on most laboratory media, although it grows best on blood agar with ampicillin added. This organism is increasingly recognized as a human pathogen in a variety of infections, including wound infections and sepsis in immunocompetent patients. Many reptiles, amphibians and fish are found to be infected with the organism. Just this year, I saw my first case of Aeromonas sepsis in an immunocompetent host with a PICC line for osteomyelitis. We could not determine where the source of the organism was, but it readily cleared with line removal and cefotaxime.

The ubiquitous fungus, Fusarium species (a pathogenic mold – Figure 6) has also been reported with stingray injuries. This fungus is normally not seen in immunocompetent hosts unless with a penetrating injury or burn. It has a tendency for vascular invasion, resulting in necrotic lesions, as shown in Figures 7 and 8 (biopsy of a lesion in Figure 7) in a cancer patient.

Of course, it is always best to avoid being stung by these relatively harmless creatures by not stepping on them when wading in the water at the beach. Some experts recommend shuffling your feet rather than taking steps when in the water.

A retained foreign body was reasonably ruled out by the various radiographs and ultrasound obtained. Hopefully, the worst thing you will get by going to the beach is a case of swimmer’s itch (Figure 9), usually caused by an avian schistosome and fairly self-limited. But stingrays, jelly fish and occasionally sharks will remain a risk of entering the sometimes murky waters off our shores. Sunburn remains the greatest risk. Just be prepared.

Columnist comments

I would like to thank Dr. Di Maggio and her daughter, Alexandra, for contributing this very interesting case. Dr. Di Maggio trained at Rush Medical School in Chicago and was a pediatric resident at Children’s Memorial, also in Chicago. She is currently in private practice at Town and Country Pediatrics in Chicago, where she says she can honestly say that none of her group has ever treated a stingray injury.

James H. Brien, DO, is Head of the Pediatric Infectious Diseases Section at The Children’s Hospital at Scott and White and is the Associate Professor of Pediatrics at Texas A&M University, College of Medicine, Temple, Texas. E-mail: jhbrien@aol.com