SXT-related integrating conjugative element and IncC plasmids in Vibrio cholerae O1 strains in Eastern Africa.

OBJECTIVES: The objective of this study was to investigate the extent of resistance patterns and associated mobile genetic elements in epidemic V. cholerae O1 El Tor strains isolated from Eastern Africa in the late 1990s. METHODS: Self-transmissible genetic elements and associated clusters of genes encoding resistance were detected by conjugation experiments. Detection of SXT-related integrating conjugative elements (ICEs) and associated antibiotic resistance genes was performed by PCR to amplify the SXT element-integrase gene (int), right SXT element-chromosome junction (attP-prfC) and genes conferring resistance to chloramphenicol (floR), sulfamethoxazole (sulII), streptomycin (strA) and trimethoprim (dfrA1). Genomic relatedness was established by random amplified polymorphic DNA patterns. RESULTS: Of 224 strains analysed, 200 isolates exhibited resistance to four or more antimicrobials. An IncC plasmid, encoding resistance to ampicillin, chloramphenicol, streptomycin, sulfamethoxazole and trimethoprim, conferred multidrug resistance to 113 strains isolated from Somalia and Ethiopia, whereas an SXT-related ICE, encoding resistance to chloramphenicol, streptomycin, sulfamethoxazole and trimethoprim, conferred multidrug resistance to 74 strains isolated from Sudan, Kenya and Tanzania. CONCLUSIONS: This study has shown the spread of SXT-related ICEs among V. cholerae O1 African isolates. It has also highlighted the role of two distinct genetic elements in conferring multiple resistance to the two distinct groups of V. cholerae O1 strains that, in the late 1990s, spread through Eastern Africa, a critical geographic region for the persistence and transmission of cholera to the entire continent.

Clonal relationship among Vibrio cholerae O1 El Tor strains causing the largest cholera epidemic in Kenya in the late 1990s.

Eighty Vibrio cholerae O1 strains selected to represent the 1998-to-1999 history of the largest cholera epidemic in Kenya were characterized by ribotyping, antimicrobial susceptibility, and random amplified polymorphic DNA patterns. Except for 19 strains from 4 local outbreaks in North Eastern Province along the Somalia border, the other 61 strains from 25 outbreaks occurring in districts scattered around the country were all ribotype B27 and resistant to chloramphenicol, spectinomycin, streptomycin, sulfamethoxazole, and trimethoprim. The 61 strains showed similar and specific amplified DNA patterns. These findings indicate that the predominant strains that caused the Kenyan epidemic had a clonal origin and suggest that ribotype B27 strains, which first appeared in West Africa in 1994, have had a rapid spread to eastern Africa.

Comparison of five methods of malaria detection in the outpatient setting.

In eastern Africa where 90% of the malaria is due to Plasmodium falciparum, the accuracy of malaria diagnosis at the outpatient level is becoming increasingly important due to problems of drug resistance and use of alternative, costly antimalarial drugs. The quantitative buffy coat (QBC) technique, acridine orange staining with an interference filter system, and the ParaSight-F test have been introduced as alternative methods to conventional microscopy for the diagnosis of malaria. Two hundred thirteen outpatients were tested using these alternative methods and conventional microscopy by five experienced technologists; two were randomly allocated to read the results of each test. Paired results showed the highest level of agreement with the ParaSight-F test (99%), followed by Field stain (92%). The results of the QBC technique showed the least agreement (73%). Using conventional microscopy as the reference standard, the ParaSight-F test had a sensitivity range of 90-92% and a specificity of 99%, staining with acridine orange had a sensitivity range of 77-96% and a specificity range of 81-98% and the QBC technique had a sensitivity range of 88-98% and a specificity range of 58-90%. All microscopic tests showed lower sensitivities (as low as 20% using staining with acridine orange) in detecting low parasitemias (< or = 320/microl) than the ParaSight-F test (70%). Due to the high cost of the ParaSight-F test, Field-stained blood films remain the most appropriate method for diagnosis of P. falciparum in eastern Africa. The ParaSight-F test may be used in situations where no trained microscopists are available, or where malaria is strongly suspected and the results of microscopy are negative.

Antibiotic resistance pattern of Vibrio cholerae and Shigella causing diarrhoea outbreaks in the eastern Africa region: 1994-1996.

Between March 1994 and December 1996, 1797 rectal swabs were transported to the AMREF laboratory from sites in six countries in the eastern Africa region: 1749 were cultured for Vibrio cholerae and 48 for Shigella/Salmonella. Culture, isolation, identification and antibiotic susceptibility testing were performed using standardized techniques. The isolates were categorized as sensitive or resistant based on standardized zones of inhibition. The rate of isolation of V. cholerae from rectal swabs increased progressively from less than 20% to more than 45% between 1994 and 1996, 80-100% of isolates of V. cholerae from Kenya and south Sudan, and 65-90% from Somalia were sensitive to tetracycline, although in 1995 isolates from Mogadishu showed only 44% sensitivity. All isolates from Tanzania and Rwanda were 100% resistant to tetracycline. In Kenya and Somalia, the percentage of isolates sensitive to chloramphenicol and cotrimoxazole reduced markedly from 85% in 1994 to < 10% in 1996. 100% of isolates from Rwanda and Tanzania were resistant to chloramphenicol and cotrimoxazole while in south Sudan > 70% of isolates were sensitive. Nalidixic acid and erythromycin retained > 75% sensitivity in all areas. Shigella dysenteriae and Shigella flexneri were recovered from dysentery specimens in northern Kenya. Both species showed similar antibiotic sensitivity patterns and were sensitive only to nalidixic acid and furazolidone. Due to variations of resistance patterns within countries in the region, antibiotic sensitivity testing should be performed at the start of an outbreak, and antibiotic use should be restricted to severe cases of V. cholerae and Shigella infection.