Abstract
The emergence of multidrug-resistant enteric fever led to the use of ciprofloxacin as the mainstay of therapy. Furthermore, nalidixic acid-resistant Salmonella typhi (NARST) with decreased susceptibility to ciprofloxacin causing therapeutic failure emerged and became endemic (Threlfall & Ward, 2001). Consequently, there have been several isolated reports, including from India, on ciprofloxacin resistance (Adachi et al., 2005; Capoor et al., 2006; Cooke et al., 2006; Joshi & Amarnath, 2006; Kownhar et al., 2007; Mohanty et al., 2006; Nair et al., 2006; Renuka et al., 2005; Saha et al., 2006). Reports of cephalosporin resistance have also emerged (Saha et al., 1999; Marano et al., 1999).
The index case of ciprofloxacin-resistant Salmonella enterica serovar Paratyphi A (S. Paratyphi A) from our hospital was detected in December 2004 in the blood culture of a 7-year-old boy with septicaemia and bilateral cellulitis of the lower limbs of 2 months duration. He was treated for staphylococcal cellulitis with several broad-spectrum antimicrobials, including fluoroquinolones, in another hospital. In our hospital, his blood for culture grew S. Paratyphi A on the third day that was resistant to ciprofloxacin (MIC=256 µg ml–1) and he was successfully treated with ceftriaxone. This study was initiated to evaluate the emerging resistance in enteric fever isolates over a span of 5 years (2001 and August 2005–August 2006).
The study was conducted in a 1570-bed tertiary care hospital in New Delhi. Patients from rural and urban areas of northern India are referred there for further management. In 2001, 178 isolates were collected, and 198 isolates were recovered between August 2005–August 2006 and included in the study. These isolates were compared for phenotypic traits including epidemiological parameters and antimicrobial susceptibility pattern.
Biochemical identification and serotyping with specific antisera (Central Research Institute, Kasauli, India) were performed to confirm all isolates. The antimicrobial susceptibility of the isolates was determined by the disc diffusion method of Kirby Bauer on Mueller–Hinton agar using ampicillin (10 µg), chloramphenicol (30 µg), trimethoprim/sulphamethoxazole (1.25/23.75 µg), nalidixic acid (30 µg), ciprofloxacin (5 µg), ceftriaxone (30 µg), cefixime (5 µg) and cefepime (30 µg). The MIC of ciprofloxacin, cefotaxime, and cefepime was determined by agar dilution, in accordance with CLSI guidelines (CLSI, 2006). The MIC experiments were repeated twice and the mean was taken.
In 2001, 59.6 % of enteric fever cases occurred in male patients, the median age of the patients was 22 years, and the majority (74 %) of cases occurred in the outpatient department. In 2005–2006, the respective figures were 64.7 %, 12 years and 70.2 %. There was an increase of 3.8 % in patients requiring hospitalization. The summer and monsoon months (April–September) uniformly showed the maximum rate of isolation (70 %). In 2001, 98.3 % of isolates were S. Typhi and 1.7 % were S. Paratyphi A, whereas in 2005–2006, 71.9 % were S. Typhi and 18 % were S. Paratyphi A. Table 1 depicts the comparative antimicrobial resistance profiles of enteric fever isolates in 2001 and August 2005–August 2006. Table 2 shows the comparative MICs of ciprofloxacin, cefotaxime and cefepime for the isolates.