Sulfamethoxazole-trimethoprim-resistant Shigella flexneri in northeastern Brazil

Emergence of trimethoprim-resistant Escherichia coli in healthy persons in the absence of prophylactic or therapeutic antibiotics during travel to Guadalajara, Mexico

Thirty-nine healthy US students without diarrheal disease and who had not received prophylactic or therapeutic antibiotics were monitored for emergence of trimethoprim-resistant gram-negative fecal flora for a 3-week period after arrival in Guadalajara, Mexico. During this time period, most students showed no change in total fecal gram-negative bacteria (p > 0.05) but showed an increasing level of trimethoprim (TMP) resistance (p < 0.01) among fecal coliforms. Escherichia coli was the TMP-resistant organism isolated in 18 of 39 (46%) healthy students. These 18 TMP-resistant E. coli were also resistant to ampicillin (44%), azithromycin (11%), chloramphenicol (39%), ciprofloxacin (11%), doxycycline (89%), erythromycin (100%), furazolidone (72%), levofloxacin (17%), trimethoprim-sulfamethoxazole (89%) and trovafloxacin (17%). In the absence of prophylactic and therapeutic antibiotics, increased acquisition of TMP-resistant gram-negative fecal flora in this developing country is probably due to poor sanitary conditions and the recurrent and heavy exposure to antimicrobial-resistant indigenous flora as a result of contaminated food and drink.

[Multiple antibiotic resistance mediated by R plasmid in Shigella flexneri strains isolated in the northeast of Brazil]

In Shigella strains were studied the molecular mechanism that mediated the multiply antibiotic-resistance. Twenty-six strains of Shigella flexneri were utilised in this investigation. These strains were submitted to disk diffusion test, mating experiments and plasmid isolation. In relation to antibiotics resistance standard it was observed that all Shigella flexneri strains were resistant to at least, three antibiotics tested. From twenty-six Shigella flexneri strains donors submitted to conjugation process, 34.6% (nine strains) resulted in variable frequency of transconjugants. From strains that conjugated, 100%, transferred the resistance factor acquainted with ampicillin. Being that, in all transconjugants which were observed, just one plasmid with 23.1 Kb was evidenced. This plasmid found in all strains was characterised as the cause of resistance to ampicillin.

High frequency of strains multiply resistant to ampicillin, trimethoprim-sulfamethoxazole, streptomycin, chloramphenicol, and tetracycline isolated from patients with shigellosis in northeastern Brazil during the period 1988 to 1993

The occurrence and antimicrobial resistance pattern of Shigella isolates obtained from persons in community and hospital-based studies of diarrhea and matched controls in northeastern Brazil were studied. The isolation rate of Shigella spp. from patients with diarrhea during 1988 to 1993 varied from 4.5% (26 of 575) for the urban community of Gonçalves Dias to 6.7% (12 of 179) and 5.9% (7 of 119) for Hospital Infantil and Hospital Universitário, respectively. Of the 55 Shigella isolates (45 from patients with diarrhea, 8 from controls, and 2 undetermined) 73% (40 of 55) were Shigella flexneri, 16% (9 of 55) were S. sonnei, 7% (4 of 55) were S. boydii, and 4% (2 of 55) were S. dysenteriae. Of 39 S. flexneri strains, over half were resistant to ampicillin, trimethoprim-sulfamethoxazole, or both. Over 64% were resistant to streptomycin, chloramphenicol, and tetracycline. Overall, 82% of all S. flexneri isolates were resistant to four or more antimicrobial agents tested. As elsewhere, in the northeast of Brazil, ampicillin and trimethoprim-sulfamethoxazole are no longer reliable for treatment of S. flexneri infection. Most Shigella strains were resistant to four or more antimicrobial agents. Nalidixic acid was still useful for treatment of infections due to S. flexneri.

Antibiotic resistance of Shigella strains isolated in the Federal Republic of Germany 1989-1990

A great many reports have been published about the multiresistance to strains of antibiotics in countries with a high incidence of shigellosis. In order to obtain better information about the situation in Germany, we tested 255 Shigella strains to 28 antibiotics during the 1989-1990 period. 153 (60%) of isolates originated from imported cases of infection (Middle and Far East, West and North Africa, Central America), whereas no history of infection in foreign countries was available for the remaining 102 strains. 207 (81.2%) of these strains were resistant to one or more antibiotics. They were divided into 6 phaenotypes according to their resistant pattern. The phaenotypes with the resistance patterns AMP, CMP, SM, SSS, TET as well as SM, SSS, TET in combination with SXT (38.6%) were most frequently isolated, followed by phaenotypes with the resistance pattern AMP, CMP, SM, SSS, or SM, SSS, combined with or without SXT (27.5%), and the phaenotypes AMP, CMP, SM, TET and CMP, SM, SSS, TET (15%). The incidence of resistance was significantly higher in strains from imported cases (93.5%) than in isolates from domestic infections (62.7%; p < 0.001). The similarity of the resistance patterns of strains acquired abroad and those acquired in Germany suggested that such strains might have been introduced from abroad. All strains were sensitive to the quinolones examined (ofloxacin and enoxacin) as well as to cephalosporines of the second and third generations.

Monitoring of antibiotic resistance in shigellae isolated in The Netherlands 1984-1989

During surveillance of antimicrobial resistance in Shigella strains isolated in the Netherlands from 1984 to 1989 and forwarded to the National Institute of Public Health and Environmental Protection for typing, sensitivity to twelve antimicrobial agents was assessed. High rates of resistance to the older drugs of choice in treating shigellosis were found, i.e. ampicillin and trimethoprim-sulfamethoxazole. Ampicillin resistance varied from 33 to 53% among Shigella flexneri strains and from 10 to 17% among Shigella sonnei strains. Trimethoprim and trimethoprim-sulfamethoxazole resistance increased from 8% to about 25% among Shigella flexneri and from 16 to 46% among Shigella sonnei isolates. All strains were susceptible to the newer quinolones, but five strains resistant to nalidixic acid showed decreased susceptibility to norfloxacin. Approximately 10% of the isolates were resistant to the combination of ampicillin, trimethoprim and sulfamethoxazole.

Multiple drug-resistance in Shigella flexneri isolated from a patient with human immunodeficiency virus

Persistent shigellosis, due to Shigella flexneri resistant to multiple antibiotics, developed in a 40-yr-old homosexual man with human immunodeficiency virus infection. The Shigella strain demonstrated resistance to ampicillin, tetracycline, and trimethoprim-sulfamethoxazole. Although Shigella flexneri isolates resistant to trimethoprim-sulfamethoxazole are uncommon in the United States, laboratories should monitor resistance patterns through routine in vitro susceptibility testing.

Use of norfloxacin in the treatment of acute diarrheal disease

In studies conducted in seven countries, 392 persons with acute diarrhea were enrolled and randomly assigned to one of three regimens. In order to compare the effectiveness of various therapies for acute gastroenteritis, patients were treated for five days with either norfloxacin, 400 mg twice daily, norfloxacin, 400 mg three times a day, or trimethoprim/sulfamethoxazole, (160 mg/800 mg) twice daily. Clinical cure occurred in 89 percent (lower dose) and 91 percent (higher dose) of those treated with norfloxacin, compared with 78 percent of those receiving trimethoprim/sulfamethoxazole; cure rates in each treatment group were greater when the patient's stool contained fecal leukocytes. In 105 of 106 (99 percent) patients treated with either dose of norfloxacin and in 49 of 52 (94 percent) trimethoprim/sulfamethoxazole-treated subjects, the bacterial enteropathogen identified in the pretreatment stool was eradicated on the posttreatment specimen. Two percent (two patients) of those receiving the lower dose of norfloxacin, 3 percent (two patients) of those receiving trimethoprim/sulfamethoxazole, and 4 percent (three patients) of those receiving the higher dose of norfloxacin experienced minor and transient adverse hematologic or blood chemistry reactions. In addition, mild cutaneous reactions that were attributed to the study medications developed in two patients receiving the higher dose of norfloxacin and in three patients who received trimethoprim/sulfamethoxazole. These studies indicate that norfloxacin is safe and effective therapy for bacterial diarrhea.

Lack of emergence of resistant fecal flora during successful prophylaxis of traveler's diarrhea with norfloxacin

Norfloxacin, a new quinolone carboxylic acid derivative, was compared with an identical-appearing placebo preparation in a prospective, randomized, double-blind trial for prevention of traveler's diarrhea among 120 U.S. students arriving in Mexico. Prophylaxis was continued for 2 weeks. Diarrhea was defined as four unformed stools in 24 h plus an additional symptom of enteric disease. In the norfloxacin prophylaxis group, 4 of 56 subjects (7%) experienced diarrhea, compared with 36 of 59 subjects (61%) in the placebo group. The difference was significant (P less than 0.0001). In contrast to our previous experience with use of trimethoprim-sulfamethoxazole to prevent traveler's diarrhea, quantitative stool cultures in the norfloxacin-treated group revealed a significant decline of normal aerobic fecal flora during prophylaxis (P less than 0.0005). Among stool samples from norfloxacin-treated subjects, 32 of 38 (84%) cultured on day 7 and 34 of 37 (92%) cultured on day 14 had no gram-negative bacilli. After norfloxacin was discontinued, fecal flora returned to pretreatment levels. No gram-negative aerobic flora resistant to norfloxacin were found during weekly quantitative cultures before, during, or after therapy.

Characterization of transferable plasmids from Shigella flexneri 2a that confer resistance to trimethoprim, streptomycin, and sulfonamides

A set of plasmids conferring resistance to several antibiotics, including the combination of trimethoprim and sulfamethoxazole, has been isolated from Escherichia coli following conjugative cotransfer from a clinical isolate of Shigella flexneri 2a. One of the plasmids, pCN1, was shown by subcloning and DNA sequencing to carry a gene encoding a trimethoprim-insensitive dihydrofolate reductase identical to that found in E. coli transposon 7. This plasmid was also shown to confer resistance to both streptomycin and spectinomycin by production of an adenylyltransferase that inactivated the drugs and the gene encoding this enzyme has also been sequenced. A second plasmid from the set, pCN2, was shown to inactivate streptomycin by a phosphotransferase mechanism and also to confer resistance to sulfonamides. The third plasmid from the set could not be correlated with a drug-resistance phenotype, but does appear to play a crucial role in plasmid mobilization.