Plasmid profile analysis of Salmonella ser. Typhimurium phage untypable strains encountered in diverse geographic regions of India.

Plasmid profile analysis and antibiotic resistance pattern determination were carried out for 117 phage untypable S. Typhimurium strains. Majority of the strains (82%) were resistant to all the seven antibiotics tested, R-pattern being ApCmKmSmSuTcTp, rest (12%) showed heterogenous R-patterns. Plasmid DNA analysis revealed phage untypable strains to harbour large (58.8-114.3 MDal), intermediate size (36 MDal, 42 MDal) and small (1.8-5.2 MDal) plasmids with varying molecular weights. All the phage untypable strains could be subgrouped by plasmid profile analysis into 23 plasmid patterns. Plasmid profile analysis could discriminate large number of phage untypable strains on the basis of their plasmid pattern.

Plasmid profiles, adhesive & invasive properties of Salmonella ser. Typhimurium strains: phage types 99 & 36.

Adhesive and invasive properties were compared with plasmid profile in S. Typhimurium strains of phage type 99(10) and 36(10). All strains of phage type 99 were multiple drug resistant (ApCmKmSmSuTcTp) and harboured small plasmids of 2.4-5.2 MDal. Six strains of the phage type 36 had ApCmTc R-pattern and two with only ampicillin resistance, carried plasmids of molecular size 2.6-5.2 MDal; two strains were sensitive to all antibiotics and devoid of plasmids. None of the strains were found to harbour high molecular weight plasmids. All plasmid positive strains of phage types 99 and 36 could be divided into two groups of three plasmid patterns each, which were phage type specific. All plasmid positive and negative strains adhered and invaded HeLa cells to different degrees. No correlation could be established between plasmid profile and adhesion invasion characteristics. High molecular weight plasmids therefore are unlikely to be essential for adhesion and invasion.

Current status of drug resistance & phage types of Salmonella typhi in India.

A total of 11391 strains of S. typhi were received at the National Salmonella Phage Typing Centre at New Delhi during January 1990- August 1992, from various regions of India. Of these, 39.7 per cent were from north India, 37.5 per cent from central India and 22.8 per cent from south India. 64.5 per cent of S. typhi were found to be multidrug resistant (MDR), maximum resistance being observed in 1991 (71.6%) while it was least in 1990 (50.05%). There was a slight decline in the percentage of MDR strains in 1992. Region-wise analysis of the resistant strains showed maximum number in central India (71.32%), whereas it was least in the south (55.2%); 62.34 per cent of strains received from north India were MDR. Irrespective of the year or region, the predominant resistance pattern remained AMCSXTTE. The commonest phage type was E1, followed by 0 and A. This pattern was also seen in the MDR S. typhi. Certain degraded Vi strains, untypable Vi strains and Vi negative strains were also multidrug-resistant. An important change observed in this study was that a small number of strains belonging to phage types C1, K1, 28, 40, 41 and 42 which were always sensitive earlier, had developed multidrug resistance. Small outbreaks due to one phage type (e.g., 28 and 51) were short lived and subsided spontaneously. More diversity of phage types was observed in north India as compared to central and south India.

Duodenal string test in typhoid fever.

Twenty five children between 4-12 years of age hospitalized with a clinical diagnosis of enteric fever were studied for evaluating the practicality and sensitivity of duodenal string-capsule culture (DSCC) and compared with conventional cultures from blood (BC), urine (UC) and stool (SC). Duodenal string capsule (DSCC) was successfully inserted in 18 patients (72%). Insertion of DSCC failed in 7 patients (28%) and all of them were below 6 years of age. Salmonella typhi was isolated from DSCC and/or BC in 13 cases (72.2%). DSCC was positive in 11 out of 13 confirmed cases of typhoid fever (84.6%). BC was positive in 8 cases (61.5%). DSCC was successful in isolating the organism in about 30% more cases than BC. Duodenal string test was a simple, non-invasive and a reliable test which when used in combination with BC could identify almost all cases of enteric fever irrespective of duration of fever and prior use of antibiotics.

Multidrug resistant typhoid fever: therapeutic considerations.

Forty six blood culture positive cases were studied during the current outbreak of multidrug resistant typhoid fever (MRTF). The present outbreak was caused by E1 phage type and organisms were resistant to all commonly used drugs for the treatment of typhoid fever, viz., chloramphenicol (78%), co-trimoxazole (76%) and ampicillin (68%). Treatment failures with chloramphenicol (45.5%) corroborated well with in vitro resistance. No treatment failure was seen with chloramphenicol and ceftriaxone, when these drugs were used in cases infected with sensitive strains. Among the alternative drugs used in cases with in vitro sensitivity, successful clinical response was seen with ceftriaxone (4/4) and cefotaxime (8/9) as compared to cephalexin (3/5) or a combination of cephalexin and furazolidone (9/12).

A clinical profile of multidrug resistant typhoid fever.

Fifty blood culture positive patients of typhoid fever were studied during the current outbreak of the disease for their clinical profile. In 39 (78%) cases the isolates of S. typhi were resistant to conventional drugs. Children below 2 years of age constituted 20% of the total cases and belonged exclusively to the group with multidrug resistant typhoid fever (MRTF). The clinical presentation seemed to mimic malaria, bronchopneumonia, meningitis, etc. Typhoid hepatitis was diagnosed in 2 cases with MRTF. Life threatening complications were seen in 28.2% patients and were observed exclusively in MRTF group.