Antibiotic resistance in gonorrhea
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Neisseria gonorrhoeae, the bacterium that causes the sexually transmitted infection gonorrhea, has developed antibiotic resistance to many antibiotics. The bacteria was first identified in 1879.[1]
In the 1940s effective treatment with penicillin became available, but by the 1970s resistant strains predominated. Resistance to penicillin has developed through two mechanisms: chromosomally mediated resistance (CMRNG) and penicillinase-mediated resistance (PPNG). CMRNG involves step wise mutation of penA, which codes for the penicillin-binding protein (PBP-2); mtr, which encodes an efflux pump that removes penicillin from the cell; and penB, which encodes the bacterial cell wall porins. PPNG involves the acquisition of a plasmid-borne beta-lactamase.[2] N. gonorrhoeae has a high affinity for horizontal gene transfer, and as a result, the existence of any strain resistant to a given drug could spread easily across strains.[citation needed]
Fluoroquinolones were a useful next-line treatment until resistance was achieved through efflux pumps and mutations to the gyrA gene, which encodes DNA gyrase.[2] Third-generation cephalosporins have been used to treat gonorrhoea since 2007, but resistant strains have emerged. As of 2010, the recommended treatment is a single 250 mg intramuscular injection of ceftriaxone, sometimes in combination with azithromycin or doxycycline.[3][4] However, certain strains of N. gonorrhoeae can be resistant to antibiotics that are normally used to treat it. These include: cefixime (an oral cephalosporin), ceftriaxone (an injectable cephalosporin), azithromycin, aminoglycosides, and tetracycline.[5][6]