What Is Shigella? Shigellosis Outbreaks Show How Antibiotic-Resistant Bacteria Develop
A series of recent outbreaks of an intestinal disease called shigellosis have spread throughout California, leaving many sick and dozens in intensive care. The unprecedented outbreak revealed a far more virulent strain of the bacteria than doctors were familiar with. However, new research may shed light on how shigella, and other types of bacteria, develop antibiotic resistance.
In a study now published online in the journal mSphere, researchers sequenced and analyzed genomes from Shigella sonnei (S. sonnei) bacteria associated with major shigellosis outbreaks in California in 2014 and 2015, and found clues into how the bacteria became so powerful and also gained resistance to antibiotics. The team found that strains of the bacteria that had been infected with a bacteriophage, a virus that replicates within bacteria, led to more serious illness in patients. Other strains of the bacteria contained genes that gave it resistance to the broad-spectrum of antibiotics.
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"We know these movements of DNA can be important for the spread of antibiotic resistance, virulence and pathogenicity factors," said Jonathan Eisen, a researcher involved with the study, in a recent statement. "Having the genome data from outbreaks allows us to try to figure out what happened."
Usually the Shigella bacteria do not cause very severe infections, but the specific toxin gene they acquired may be the reason they're becoming more severe and drug resistant. The team believe that better understanding genetic sequencing of Shigella bacteria and other infectious diseases may reveal how these infections gain drug resistance, and even lead to the development of more effective treatments.
Shigellosis is usually characterized by often-bloody diarrhea, abdominal pain or cramps, and fever, The Mayo Clinic reported. Although the symptoms usually go away on their own in a few days, in rare cases, the symptoms can be so dehydrating that they lead to more serious complications. Unfortunately, increasing strains of shigella have become drug resistant. According to the Centers for Disease Control and Prevention, reducing the spread of antibiotic-resistant Shigella requires preventing infections, tracking resistance, better managing antibiotic use, as well as developing new treatments.
Source: Kozreva VK, Jospin G, Greninger AL, Watt JP, Eisen JA, Chaturvedi V. Recent Outbreaks of Shigellosis in California Caused by Two Distinct Populations of Shigella sonnei with either Increased Virulence or Fluoroquinolone Resistance. mSphere . 2016
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