Antibiotic Resistance

Antibiotic susceptibility tests of O1 strains isolated from the 1979 outbreak in Bangladesh showed resistance to tetracycline, in addition to other antibiotics ampicillin, kanamycin, streptomycin, and cotrimoxazole (trimetho-prim-sulfamethoxazole). The subsequent follow-up study of the epidemiological assessment of the outbreak indicated that the O1 isolates were not resistant to tetracycline, including streptomycin, chloramphenicol, amoxicillin, or nalidixic acid. All the classical V. cholerae strains isolated in Bangladesh during 1988 and 1989 were resistant to tetracycline, whereas strains belonging to the El Tor biotype were sensitive to the drug. Almost after a decade, tetracycline-resistant El Tor strains reemerged in Bangladesh in 1991 and in Tehran in 1998.[3,15] In October 1995, the emergence of nalidixic acid-resistant O1 V. cholerae El Tor strains was reported in Southern India.[16] Moreover, 80-100% of V. cholerae O1 isolated in Kenya, South Sudan, Peru, and Guinea-Bissau, and 65-90% of isolates from Somalia isolated between March 1994 and December 1996, were not resistant to tetracycline, whereas all the O1 isolates from Tanzania and Rwanda were resistant to this drug.[3] A number of V. cholerae O1 strains isolated during 1992-1997 in Calcutta showed resistance to tetracycline (in addition to ampicillin, chloramphenicol, cotrimoxazole, neomycin, and streptomycin) and emerging resistance to nalidixic acid.[17] Analyses of the antibiotic susceptibility of V. cholerae O1 strains isolated from Kottayam, Alleppey, and Trivandrum, Southern India, in 2000 showed that these strains are resistant to nalidixic acid, and/or neomycin, and/or streptomycin, respectively, in addition to other drugs tested, and are sensitive to tetracycline, suggesting the existence of different R-types of V. cholerae strains in different locations.[18] Continuous surveillance of outbreaks of cholera in Kerala, Southern India showed the emergence of nalidixic acid-resistant strains of V. cholerae O1 in 2002 (unpublished).

In the analysis of the O139 strains isolated during the past 9 years, Faruque et al.[7] showed that O139 strains remained largely susceptible to ciprofloxacin, tetracy-cline, and gentamicin, and resistant to ampicillin; susceptibility to cotrimoxazole, chloramphenicol, and streptomycin varied during this period. Recent studies have shown that O139 strains isolated from different parts of India were, by and large, resistant to ampicillin, furazolidone, streptomycin, and nalidixic acid, except for Calcutta strains that were sensitive to nalidixic acid. Recently, emergence of nalidixic acid-resistant strains of V. cholerae O139, which are sensitive to sulfamethox-azole, trimethoprim, and streptomycin, was observed from the outbreak of cholera in Alleppey and Trivandrum, Southern India in 2002 (unpublished). Waldor et al.[19] reported the presence of a 62-kb self-transmissible transposon-like (SXT) element encoding resistance to sulfamethoxazole, trimethoprim, and streptomycin in V. cholerae O139 isolated during this period. The SXT

element could be conjugally transferred from V. cholerae O139 to V. cholerae O1 and Escherichia coli strains, where it integrated into recipient chromosomes in a site-specific rec-A-independent manner. Considering the rapidly changing patterns of antibiotics observed among V. cholerae strains, it appears that there is substantial mobility in genetic elements encoding antibiotic resistance in V. cholerae.

Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

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