Clinical Profile and Sensitivity Pattern of Salmonella Serotypes in Children: A Hospital Based Study

Introduction: Enteric fever is a systemic infection caused by the bacteria, Salmonella enterica serovar Typhi (S.typhi) and Salmonella enterica serovara Paratyphi (S. paratyphi A, B and C). Most of the burden of the disease is limited to the developing world and the disease still has the issues like wide spectrum of clinical presentation and multidrug resistance. Objectives: This study was done to analyze the clinical profile and antibiotic sensitivity pattern in the cases of culture positive enteric fever. Methods: A prospective cross-sectional study was conducted in Civil Service Hospital from February 2010 to January 2011 in the paediatric population in the age group of 2 to 14 years. Children with Salmonella species isolated in blood culture were included in the study. Results: Out of the 40 children with culture positive enteric fever, male to female ratio was 1.3:1 with common age group between 11-14 years. S typhi was isolated in 25 cases while S. paratyphi in 15 cases. Clinical features of S. typhi and S. paratyphi were indistinguishable. Both S.typhi and S. paratyphi were found to be 100% sensitive to drugs like Ceftriaxone, Cefotaxime, Cefixime and Chloramphenicol. Sensitivity to Ofloxacin was 100% in S. paratyphi and 92% in S.typhi. Similarly sensitivity of Azithromycin was 92% and 93% for S.typhi and S. paratyphi respectively. Conclusion: Salmonella serotype is still 100 % sensitive to third generation cephalosporin. Some percentage of resistance is seen with Ofloxacin in S. typhi and with Azithromycin in both S.typhi and S. paratyphi.


Introduction
E nteric fever is a systemic infection caused by the bacteria Salmonella enterica serovar Typhi (S.typhi) and Salmonella enterica serovara Paratyphi (S. paratyphi A, B and C).Because of the provision of clean water and good sewage system, it is a sporadic disease in developed countries and occurs mainly in travellers returning from endemic regions.Today, most of the burden of the disease is limited to the developing countries where standards of hygiene and sanitation remain poor 1 .
The global estimate of incidence of enteric fever caused by S. typhi is over 21 million causing 700,000 deaths each year and more than 5 million new infections are caused by S. paratyphi A 2,3 .It is one of the major public health problems in Nepal, particularly in Kathmandu and other urban areas 4 .Chloramphenicol became the standard antibiotic since its introduction in 1948.Its resistance occurred within two years after its introduction, but Chloramphenicol -resistant typhoid fever became a major problem in 1972 when outbreaks occurred in Asia and Latin America 1,5,6 .Later in late 1980s, S. typhi developed multi drug resistance to Chloramphenicol, Trimethoprim, Ampicillin and Sulfamethoxazole which were then used as fi rst-line drugs, leading to outbreaks in Asia and Africa 7,8,9,10 .Fluoroquinolones were very effective in early 1990s, but emergence of resistance to these drugs have occurred 11 .Also sporadic reports of high level of resistance to Ceftriaxone in S.typhi and S.paratyphi have been seen and the relapse rate is 3-6% with this drug 1,12 .Cefi xime though, effective and cheaper oral option for the treatment of multidrug-resistant cases, experience with this drug is less 13 .A short course of 5-7 days of treatment with Azithromycin is enough in uncomplicated typhoid fever, which has a relapse rate of less than 3% as compared to Ofl oxacin where 7-10 days of treatment is required.Short course of treatment with Ofl oxacin (less than 7 days) has higher incidence of treatment failure 14,15 .
Enteric fever still has issues like wide spectrum of clinical presentation and complex mode of treatment 12 .Hence this paper describes clinical profi le and antibiogram of S.typhi and S. paratyphi.

Materials and methods
A prospective cross-sectional study was conducted in Civil service Hospital from February 2010 to January 2011.All the patients between the ages of 2 years to 14 years presenting to outpatient department who were suspected to have enteric fever had complete blood count and blood culture and sensitivity done.Those cases with Salmonella species isolated in culture were included while clinically diagnosed enteric fever was excluded from the study.
All blood samples were grown in Mac Conkey's agar for at least 96 hours and Mueller-Hinton agar with Kirky Bauer disc diffusion was used for sensitivity of culture.

Results
The study revealed total of 40 cases of culture positive enteric fever.Out of 40 children, 23(57.5%)were male and 17(42.5%)were female.According to age wise distribution, 2-5 years were 20%, 6-10 years were 32.5% and 11-14 years were 47.5%.Of the 8 patients (20%) in the age group of 2-5 years, male to female distribution was equal.Thirteen patients were in the age group of 6-10 years with male: female ratio being 0.8:1.Of 19 patients in the age group of 11-14 years; male: female ratio was 2.1:1.(Table 1).The occurrence of the disease was higher during summer and rainy season (Fig. 1).Out of 40 cases, 25(62.5%)were S. typhi and 15 (37.5%) were S. paratyphi A.

Discussion
Enteric fever is one of the common causes of febrile illness and is the major reason for seeking health service by general population 16 .
In this study, the most common age group affected was 11-14 years (47.5%).This result is much different from the study of Prajapati et al where result showed that common age group was 1-5 years 17 .Out of 40 children, males had higher incidence of disease (male to female ratio of 1.3:1).The study done by Ansari et al 18 and Bhattarai et al 19 showed similar results.There was clustering of cases of both S.typhi and S. paratyphi during summer and rainy seasons which is similar to the study done by Karkey A 3 .This study also showed that fever was present in all the patients followed by headache, abdominal pain and vomiting which is similar to other studies 16,20,21 .
Clinical symptoms of S. typhi and S. paratyphi A were indistinguishable in this study, which is similar to the study done by Karkey A 4 .The incidence of S.typhi and S. paratyphi A in this study was similar to fi ndings reported by Karkey et al 3 and Jog et al 12 .The antibiotic sensitivity pattern was also not much different from other studies 16,19 .In our study 100% sensitivity was seen with Ceftriaxone, Cefotaxime, Cefi xime, Chloramphenicol and Cotrimoxazole.Sensitivity to Ofl oxacin was 100% in S. paratyphi and 92% in S.typhi.Azithromycin resistance is documented in some percentage of Salmonella serotypes in our study which is different from the study done by Mishra et al where result shared 100% sensitivity to Azithromycin 22 .This could be due to larger sample size and mostly adult population.Most of the patients had normal leucocyte count which was similar to other literatures 12,19,21 .

Conclusion
Salmonella serotype is still 100 % sensitive to third generation cephalosporin.Some percentage of resistance is seen with Ofl oxacin in S. typhi and with Azithromycin in both S.typhi and S. paratyphi.In the endemic region like ours, appropriate antibiotic should be chosen as indicated by sensitivity pattern to prevent the emergence of resistance to common drugs.

Table 1 :
Age and sex distribution

Table 2 :
Symptoms in culture positive patients.