Drug-Resistant Shigella

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More and more infections that were treatable are now less treatable. The antibiotics that once stopped them aren't working. The antibiotics don't fight off these bugs - or not enough or not fast enough. These infections are now "antibiotic resistant."

We are running through antibiotics as bacteria become resistant. Drug-resistant Shigella is now found in the US. It started abroad. It was introduced multiple times.

It spread where it could spread. It joins drug-resistant gonorrhea, MRSA, drug resistant TB, and CRE as pathogens that threaten us but for which we have fewer means of stopping them.

Part of the reason drug resistant Shigella has been spreading so much is that we sometimes take antibiotics when we don't need them. Some people when they travel take antibiotics for a bit of diarrhea. In this case, taking antibiotics "just in case" may be more dangerous than we thought. The antibiotics we might take to keep diarrhea at bay while traveling can actually result in us bringing home resistant bacteria.

Drug Resistant Shigella in the US

In 2014, Massachusetts, California, and Pennsylvania started noticing more and more cases of Shigella resistant to Ciprofloxacin (Cipro), the first choice drug to treat shigellosis among adults. Close to 90 percent of cases tested were not susceptible to Cipro. Now 32 states and Puerto Rico have identified cases of Shigella sonnei where Cipro can't be used.

This Shigella strain is multidrug resistant. The strain was also resistant to multiple other drugs that were used in the past: streptomycin (84%), sulfisoxazole (84%), tetracycline (87%), and trimethoprim/sulfamethoxazole - Bactrim or Septra (84%).

International Travel

Half of these cases were linked to international travel.

The resistance was likely introduced from abroad and then quickly amplified where it could spread.

It's important not to take antibiotics unless you need them. Taking antibiotics when you travel may increase the chance of bringing home resistant bacteria. Travelers who had mild travel associated diarrhea did as well if they took antibiotics as if they didn't, but those who took antibiotics more often came home carrying drug-resistant bacteria.

Of those traveling to South Asia, 80% acquired drug resistant bacteria if they took antibiotics for traveler's diarrhea. Those who have severe diarrhea, as should be discussed with a doctor, do need antibiotics and medical care as needed.

Spread in the US

There are about 500,000 cases of Shigella each year in the US. Outbreaks are often large and can be long. The bacteria can clearly spread fairly easily. Shigella is often caused by contaminated food. Its spread is fecal-oral, meaning stool contamination causes it to spread. A food handler might not wash his hands well enough after using the toilet.

A toddler touching everything surrounded by other daycare kids in diapers puts her hands in her mouth. A swimming pool can become contaminated and spread the infection. It spreads among the homeless. It spreads among men who have sex with men and through anal sex.

High Risk Spread

There were two groups in the US were infection spread quickly among individuals who had not travelled.

In San Francisco, Shigella was introduced into a high-risk population. There were 95 cases in SF, almost half of these were in people who were homeless or marginally housed, though they did not live or eat together (and none had international travel). Many of these people became quite ill and almost half (of whom information is known for) were hospitalized.

Likewise, Shigella can spread rapidly among men who have sex with men. Of those men who did not travel, almost half were men who reported having sex with men.

The CDC's recommendations on Shigella

Shigella infections do not need to be treated with antibiotics. The diarrhea and infection usually resolves in 5-7 days without antibiotics. However, antibiotics can reduce how long symptoms last and are used in more serious cases.

  • Wash hands frequently, especially before eating and after using the toilet.
  • Take bismuth subsalicylate to avoid travelers’ diarrhea instead of relying on antibiotics
  • Treat traveler's diarrhea with drugs like bismuth subsalicylate
  • Only use antibiotics for severe diarrhea

There are different types of Shigella

In general, illness begins in 12–96 hours after exposure. The disease can have mild or severe diarrhea - which usually lasts 4-7 days. Severity varies by species. S. dysenteriae serotype 1 (Sd1) can cause epidemic dysentery and can cause hemolytic uremic syndrome with kidney problems, while S. sonnei can cause milder disease and S flexneri is associated with a reactive arthritis, as can be S. dysenteriae  and S. sonnei.

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