In Vitro Susceptibility of Four Serotypes of Enterohaemorrhagic Escherichia coli to Antimicrobial Agents.

Abstract

Escherichia coli (E. coli) serotype O157 : H7 was first recognized as a human pathogen during a 1982 investigation of two outbreaks of diarrhea, and is estimated to cause more than 20000 cases of infection and as many as 250 deaths each year in the United States.1,2) In Japan, the incidence of this infection is also high as was observed in a large outbreak stemming from a school lunch in Sakai City in 1996 in which 12680 people were infected with E. coli O157 : H7, and 3 of them died. 3)There is continuing controversy as to whether antimicrobial therapy should be performed for E. coli O157 : H7 infection. Some investigators have suggested that administration of antimicrobial agents for this infection promotes release of verotoxin from this serotype or tends to induce secondary infection, thus arguing against antimicrobial therapy.4,5) Others have reported no effects of administration of antimicrobial agents for E. coli O157 : H7 infection on the development of hemolytic uremic syndrome (HUS) or the microorganism discharge period. 6,7) In contrast, some studies have shown a significant decrease in the incidence of HUS after administration of appropriate antimicrobial agents such as fluoroquinolones for E. coli O157 : H7 infection, or a significant decrease in the mortality rate after administration of a fluoroquinolone to this infection in a mouse model. [8][9][10] In general, effective oral antimicrobial agents should be administered for bacterial enterocolitis. 9) Enterohaemorrhagic E. coli has many 0 serotypes (1,2,4,5,6,18, 25, 26, 38, 39, 45, 50, 55, 82, 84, 91, 103, 111, 113, 114, 115, 117, 118, 121, 128, 145, 146, 153, 163, 165) in addition to O157. However, there are no data on drug susceptibility of enterohaemorrhagic E. coli other than E. coli O157.11-13) Therefore, we evaluated E. coli O26, O111, and O165 which could be acquired in addition to E. coli O157. MATERIALS AND METHODS Susceptibility TestsThe minimum inhibitory concentrations (MIC) were determined for the 83 strains of enterohaemorrhagic E. coli after 18 h incubation at 35°C by dilution on Mueller-Hinton agar (Difco, U.S.A.) under both aerobic and anaerobic conditions. As a control, E. coli NIHJ JC-2 was used. The following agents were tested: ciprofloxacin (Bayer Yakuhin, Ltd.), norfloxacin (Kyorin Pharm.), fosfomycin Na (Meiji Seika Kaisha, Ltd.) with or without 25 mg/ml of glucose-6-phosphate (G-6-P; Oriental Yeast Co., Ltd.) added, 14) kanamycin sulfate (Meiji Seika Kaisha, Ltd.), cefoperazone Na (Pfizer Pharm, Inc.), and ceftazidime (Glaxo Japan Co.). These agents were provided in the form of a bulk powder. Anaerobic incubation was performed using a disposable O 2 absorbing and CO 2 generating agent (AnaeroPack ® ; Mitsubishi Gas Chemical Co.). The inocula (ca. 10 4 colony forming units/spot) were plated using a multipoint incubator (Sakuma Co.). MIC were defined as the lowest concentration of agent inhibiting visible growth.Productivity of Verotoxin The production of verotoxin (Shiga-like toxin) was determined by VTEC-RPLA SEIKEN (De...

Elevated Expression of GlpT and UhpT via FNR Activation Contributes to Increased Fosfomycin Susceptibility in Escherichia coli under Anaerobic Conditions

“…Bacteria often encounter oxygen-limited situations during infection of the host. In many cases, the antibacterial activities of drugs, including fluoroquinolones and aminoglycosides, decrease when oxygen is depleted (1)(2)(3)(4).…”