"This leg is hot, doc," the ambulance medic whistled. "Scratched the bottom of her foot three days ago. A nick. Nothing." He threw up a perplexed hand. Mrs. Anders, a 35-year-old black woman, brooded in her wheelchair. Vexed at the absurd injury that had landed her in the emergency room, she just wanted her leg to get better so she could go home to her three kids.
"Go to it," I told Kevin, my physician’s assistant student.
Kevin was a star, the kind of PA student who sometimes makes medical school seem overrated.
"Get the history, examine her, then tell me your plan," I told him, unnecessarily.
Ten minutes later he crisply read out of his little spiral notebook, "The patient scratched the bottom of her left foot three days ago. Can’t remember what on. Yesterday it began to hurt and swell. Last night she felt feverish. Except for a history of depression, she has no other medical problems. No diabetes, no prior leg surgeries, no nothing, really. Her temp is 104.6."
"Whew," I exhaled.
"On exam," he continued, the left foot and ankle are red, hot, and tender."
"Any other findings?"
"None."
"What do you think?"
"Cellulitis of the left ankle and foot. Needs antibiotics."
A superficial skin infection, cellulitis is both common and generally easy to treat. The usual causes, staph and strep bacteria, respond to oral antibiotics. Doctors prefer to treat both because it’s difficult, clinically, to distinguish them.
"Sounds good. Let’s take a look," I said.
The foot and ankle glowed a dusky red. But Mrs. Anders still had her pants on.
"How far up did you look?" I asked Kevin.
"Oops," he replied. Not far enough.
I smiled at Mrs. Anders and drew the curtain.
"We’ll need to take these off, I’m afraid."
"Okay," she answered neutrally.
We helped her slide the slacks off. And there, tracking up the inside of her leg like a battalion of fire ants, was an inch-wide streak of red.
I pointed: Lymphangitis. Classic sign of strep infection. The bug uses the lymphatic system like a highway. This infection has advanced well beyond her ankle. She needs intravenous antibiotics.
"And I should have picked it up," Kevin lamented.
The lymph system is the complex network of vessels that carries waste products from the tissues back into the bloodstream. These vessels also carry foreign material to the lymph nodes to help promote an immune response against infection. The worry with strep infections in the lymph system is that they can linger in the vessels, causing local destruction before the immune system can be alerted to launch an effective defense. Alternatively, if strep passes out of the lymph system and invades the bloodstream, it can cause catastrophic illness without much local infection. In Mrs. Anders’s case, strep was on the march and we would have to hurry to head it off.
Streptococcus bacteria, the cause of everyday strep throat, is among our most ancient, tenacious, and versatile bacterial enemies. Strep strains linger in the soil and on our skin, and their tricks are legion. Some can incite surface infections like strep throat and erysipelas. (The word erysipelas—Greek for red skin—refers to a more severe skin infection than cellulitis.) . In other cases, they can invade lungs, heart valves, and spinal cords. A great opportunist, strep rampaged through nineteenth-century maternity wards as puerperal fever thanks to doctors who examined new mothers with unwashed hands between cases. Before penicillin, untreatable strep throat caused lethal epidemics of rheumatic fever via an evil biochemical mimicry. The strep provokes an antibody response that mistakes the sufferer’s own heart muscle and valves for the strep intruder.
Most recently, strep reared its hydra-like head as flesh-eating bacteria. Headlines hyped it as a new plague, but 2,500 years ago Hippocrates described an erysipelas that led, gruesomely, to flesh, sinews, and bones falling away in large quantities. This horrifying condition is caused by strep strains that slip into tissue following an innocuous scrape or cut. If the infection is not treated, the bacteria can crank out enough enzymes and toxins to literally dissolve flesh. Strep enzymes can dismantle connective tissue, blood clots, and other living firewalls in its path. Strep toxins sabotage blood vessels and cell membranes, dropping blood pressure and flooding organs with oxygen-blocking cellular sludge. So efficient and tailor-made to humans are strep’s tools that in one of biology’s great ironies, we now use the enzyme streptokinase as a clot-buster to open clogged coronaries and save tens of thousands of heart attack victims a year.
Finally, this bacterial version of a Swiss Army knife kills because it is quick. Once it clears a beachhead, it can move at almost visible speed, as it had on Mrs. Anders’s leg. The nastier strains of strep secrete flesh-chewing toxins, and if the infection progresses, patients can suffer the horrendous loss that Hippocrates so accurately described. The destruction of flesh is even more terrifying because it can commence without much evidence of poisoning on the surface of the skin.
"So what do we give her?" I asked my still-chagrined PA student.
"Cellulitis can be caused by staph, strep . . ."
"Usually," I cut him off. "And you need antibiotics that cover both. But," I deepened my voice and harrumphed, "this is classic, absolutely classic strep lymphangitis. Only strep behaves in such a fashion. Your patient requires penicillin. And in large doses. So fire away."
In keeping with its particularities, strep, in this era of antibiotic resistance, has remained exquisitely sensitive to that granddaddy of antibiotics, penicillin.
"A million units?" Kevin asked.
"Her temp is over 104, the strep is galloping up her leg," I replied. "Let’s say 2.5 million."
All that remained was to call the admitting team and get Mrs. Anders upstairs. I let Kevin do it.
"And emphasize to them it’s strep and she needs penicillin."
"Right."
We moved on to other patients. An hour later, I buttonholed Mrs. Anders’s admitting intern, Carol Fields.
"Amazing lymphangitis, eh?" I asked. "You won’t see many as clear-cut as that. How much penicillin did you give?"
She squirmed.
"Our attending wants Cefazolin," she finally admitted. "Broader coverage."
