Which medications in the drug class Antibiotics are used in the treatment of Shigella Infection?

Updated: Apr 03, 2018
  • Author: Jaya Sureshbabu, MBBS, MRCPCH(UK), MRCPI(Paeds), MRCPS(Glasg), DCH(Glasg); Chief Editor: Russell W Steele, MD  more...
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Answer

Antibiotics

Ampicillin and TMP-SMZ are effective for susceptible strains; amoxicillin is less effective than this because of its rapid absorption high in the GI tract. The oral route is preferred except for seriously ill patients. In the United States, sentinel surveillance data from 2003-2006 indicated that 94% of S sonnei and 67% of S flexneri organisms were resistant to ampicillin and TMP-SMZ. The WHO now recommends that clinically diagnosed cases of Shigella dysentery be treated with ciprofloxacin as first line treatment, and pivmecillinam (not available in the United States), ceftriaxone, or azithromycin as second line treatment and lists the others as ineffective (WHO 2005a). [36] . However, resistance to quinolones has also been observed since the late 1990s, and some authors have questioned the effectiveness of this class for Shigella. The choice of antibiotic to use as first line against Shigella dysentery should be governed by periodically updated local antibiotic sensitivity patterns of Shigella isolates.

Ciprofloxacin (Cipro)

First-line treatment for shigellosis. Fluoroquinolone that inhibits bacterial DNA synthesis and, consequently, growth, by inhibiting DNA gyrase and topoisomerases, which are required for replication, transcription, and translation of genetic material. Quinolones have broad activity against gram-positive and gram-negative aerobic organisms. Has no activity against anaerobes. Continue treatment for total of 5 days, even empirical treatment in patient with typical bloody diarrhea who responds clinically with negative stool culture. (7-14 d typical)

Ceftriaxone (Rocephin)

Third-generation cephalosporin with broad-spectrum, gram-negative activity; lower efficacy against gram-positive organisms; higher efficacy against resistant organisms. Bactericidal activity results from inhibiting cell wall synthesis by binding to one or more penicillin binding proteins. Exerts antimicrobial effect by interfering with synthesis of peptidoglycan, a major structural component of bacterial cell wall. Bacteria eventually lyse due to the ongoing activity of cell wall autolytic enzymes while cell wall assembly is arrested.

Highly stable in presence of beta-lactamases, both penicillinase and cephalosporinase, of gram-negative and gram-positive bacteria. Approximately 33-67% of dose excreted unchanged in urine, and remainder secreted in bile and ultimately in feces as microbiologically inactive compounds. Reversibly binds to human plasma proteins, and binding have been reported to decrease from 95% bound at plasma concentrations < 25 mcg/mL to 85% bound at 300 mcg/mL.

Azithromycin (Zithromax)

Acts by binding to 50S ribosomal subunit of susceptible microorganisms and blocks dissociation of peptidyl tRNA from ribosomes, causing RNA-dependent protein synthesis to arrest. It has enhanced activity against gram-negative organisms. Concentrates in phagocytes and fibroblasts, as demonstrated with in vitro incubation techniques; hence, plasma concentrations are very low but tissue concentrations are very high. It has a long tissue half-life and once daily dosage is recommended. In vivo data suggest that concentration in phagocytes may contribute to drug distribution to inflamed tissues.

Ampicillin (Principen)

Broad-spectrum penicillin. Interferes with bacterial cell-wall synthesis during active replication, causing bactericidal activity against susceptible organisms.

Nalidixic acid (NegGram)

First-generation quinolone. Blocks bacterial DNA gyrase. Useful in patients with sulfas and cephalosporin allergy. WHO guidelines state most Shigella strains are now resistant to nalidixic acid.

Cefixime (Suprax)

Third-generation oral cephalosporin with broad activity against gram-negative bacteria. By binding to one or more of the penicillin-binding proteins, it arrests bacterial cell wall synthesis and inhibits bacterial growth. For outpatient use in drug-resistant Shigella infections.

Trimethoprim and sulfamethoxazole (Bactrim, Cotrim)

Combination effective for shigellosis in the past, but WHO states most Shigella strains are now resistant. Produces sequential blockade in folic acid synthesis. Effect frequently synergistic and bactericidal.


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