1. TRENDS IN SALMONELLA ASSOCIATED WITH INVASIVE AND NON-INVASIVE INFECTIONS OVER A TEN-YEAR PERIOD IN THE GAMBIA, WEST AFRICA.
SAFFIATOU DARBOE
MRC Unit, The Gambia
Date: 19th November, 2015

2. Conflict of interest: Nonex
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Medical Research Council Unit, The Gambia x
Mphil student     
     
Declaration

3. Background (1)
Salmonella enterica infections are common cause of food-borne diseases worldwide usually with self limiting outcome.
In resource limited settings however, they are a common cause of bacteraemia associated with high case fatality ratio and difficult to distinguish from other febrile illnesses.
Culture and complex serological assays remains mainstay of laboratory diagnosis.
Serovars are commonly clinically divided into two:
Typhoidal – Causing enteric fever (Typhi, Paratyphi A, B and C)
Human host restricted; transmission through faecal-oral route
Non-typhoidal Salmonellae (NTS) – causing mainly gastroenteritis (Other serovars)
Broad host range; zoonotic infections
Complex scientific nomenclature , but ….2 species: bongori and enterica Sub species: enterica, salamae, arizonae, diarizonae, houtenae and indica. (over 2500 serovars

4. Background (2)
In The Gambia, large data gaps exist in the epidemiology of diseases by S. enterica.
NTS has been reported to be a more common cause of bacteraemia than S. Typhi.
A strong association between Salmonella invasive disease and malaria is believed to exist.
The association with other disease conditions and risks factors is yet to be fully studied in our setting.
Surveillance of diseases is critical to determine regional epidemiology of serovars and emergence of multi-drug resistance.

5. Methods: study population and lab analysis
Retrospective analysis of stored samples from various clinical specimens from 3 regions in the country:
Western Region- Various Clinical samples from patients in MRC Fajara
Lower River Region – Stool from children in Keneba
Upper River Region – Stool samples from Global enteric multicentre (Gems) study
Lab analysis:
Culture and identification using routine media
Serotyping
Susceptibility testing

6. Aims
Highlight the burden of Salmonella enterica infections in our setting;
Antibiotic resistance
Serotype distribution
Age distribution
Evaluate the impact of the two main clinical groups in terms of disease burden and invasiveness.
Aim of the lab surveillance ………

7. Salmonella prevalence
Fig 1
A. Prevalence in salmonella across the different was between 0.7 to 1.0%. B. Faecal asymtomatic carriage remained the same throughout the year as opposed to bacteramia incidence which was higher during the peak malaria transmission season. C. Asymtomatic carriage is high, in the Gems case control study no difference was found in the rates of infection in those with diarrhoea and those without. D. When seasonality is taken into account however, the peak time for cases was the malaria peak season and there was difference in the carriage.

8. Antibiotic resistance pattern
Fig 2.
Resistance to the common antibiotics seen, although incidence low up to Of particular significance is the recent 2015 data on usually resistance which was compared to the other years although numbers are small to conclude on anything yet.

9. Serogroup and serotype distribution
Fig 3. Infection distribution by serovar
Fig A. NTS causing more infection in both invasive and none invasive disease in our setting than typhi. However infection with Typhi is more associated with invasive disease. Fig B. The different groups mainly associated with invasive disease are groups B and D which as in fig C comprise S. typhimurium and Enteritidis and Typhi (groupD).

10. Age distribution
≤ 5years (%)
≥ 5 years (%)
Total
Blood
63 (59.4)
43 (40.6)
106
Stool
115 (93.5)
8 (6.5)
123
CSF 1
Urine 7
Asp/ Pus/Abs 2 6 8
181 64
245
Bactaeramia and gastroenteritis more common in the under 5 age bracket

11. Conclusion
1st data on trend and phenotypic characteristics of both NTS and typhoidal Salmonella roles in infection in The Gambia.
NTS are the most common cause of both bacteraemia and gastroenteritis
S. Typhimurium was the leading followed closely by S. Enteritidis.
S. Typhi mainly caused invasive disease.
Risk of invasive disease was mainly associated with underlying conditions such as malnutrition, Sickle cell disease and and immune suppression.
Evidence of multi-drug resistance emerging and systematic surveillance is needed.

12. Limitations
Retrospect study with large data gaps in both metadata and clinical data.
Only samples from Western region were serotyped and comprised broad clinical specimens- this may mask geograhical differences.
Serotype was limited to the serogroups A to G and only those in groups B and D could were further characterized to the serovar level.

13. Dr. Richard Bradbury Dr. Martin Antonio Dr. Brenda Kwambana-Adams
Acknowledgement
Dr. Martin Antonio
Dr. Brenda Kwambana-Adams
Dr. Richard Bradbury
Mr. Bola Lawal
Dr. Davis Nwakanma
Dr. Ousman Secka

14. Thank you 

15. Results: Total sample distribution
Sample type
S.Typhimurium
S.Enteritidis
S. Typhi
S. arizonae
Other NTS ⃰
Total
Blood 35 8 16 1 46
106
Stool 6
109
123
CSF
Urine 7
Asp/Abs/pus 2 43 9 22 3
168
245
Broad range of disease conditions:
Bacteraemia
⃰ Not serotyped due to insufficient antisera or belong to other serovars