Epidemiological, clinical features and susceptibility pattern of shigellosis in the buea health district, Cameroon
© Njunda et al; licensee BioMed Central Ltd. 2012
Received: 27 September 2011
Accepted: 21 January 2012
Published: 21 January 2012
Shigellosis is an acute invasive enteric infection caused by bacteria belonging to the genus Shigella; it is clinically manifested by bloody diarrhoea. Shigellosis is endemic in many developing countries including Cameroon and also occurs in epidemics causing considerable morbidity and mortality. This study evaluated the epidemiological and clinical features of Shigella and the resistance pattern of isolates to commonly used antibiotics in the Buea Health District in Cameroon, from April to August, 2010.
Of the 223 stool samples cultured, 10 (4.5%) yielded Shigella species. Isolation rate was observed to be more in children below 15 years (7.89%), and also higher in rural areas (6.35%). All 10 isolates showed resistance to at least two antibiotics and 9 (90%) were multi-drug resistant. The highest resistance rates were encountered with cotrimoxazole (90%) and amoxicillin (80%). Least resistance was observed with azithromycin (10%).
Shigellosis is more prevalent in children below 15 years in the Buea District. There is a high level of resistance to most of the antibiotics used for the treatment of shigellosis including extended-spectrum beta-lactamases (ESBLs) as well as evidence of resistance to quinolones. Azithromycin was found to be the drug of choice for shigellosis in this setting.
Shigellosis (bacillary dysentery) is a global health problem, especially in developing countries, where substandard hygienic conditions and unsafe water supplies prevail . Among the bacterial causes of dysentery, Shigella species continue to be the most important, with a high infectivity rate and the development of antimicrobial resistance. Shigellosis is said to be a self-limiting disease, although antimicrobial therapy is recommended . Since 1940, when resistance of Shigella species to sulfonamide was first recognized in Japan , resistance of Shigella species have become progressively recorded to most widely-used antimicrobial agents . Multiple-drug resistance transmitted plasmids among Shigella species have been reported in many countries . So far, limited reports exist on the occurrence and antibiotic resistance patterns of Shigella species in Buea in particular and in Cameroon in general. The purpose of the present study was to determine the epidemiologic profiles of Shigella and their antimicrobial resistance patterns in the Buea Health District, in the South West Region of Cameroon.
Results and discussion
Of the 223 stool specimens cultured for Shigella species, 10 were tested positive with a prevalence of 4.5%. Findings from other authors [6–8] indicate slightly higher prevalence rates of 8.0%, 7.4% and 7.3% respectively, than what is obtained in this study.
The majority of Shigella isolates were from the paediatric population (children < 15 years) with an infection rate of 7.89% while no infection was recorded with individuals aged > 45 years. In line with our findings, a higher prevalence of infection in children was observed in a previous work , in which 70% of all infections occurred in children below 15 years. It was also noted that children of this age group accounted for more than a third of all Shigella positive patients . Scientific findings have revealed that type-specific immunity develops after repeated exposures during childhood . Diarrhoea account for about 16% of all causes of mortality in children , because they are at an immature age, and they are in frequent exposure to contaminated environment due to play-related activities and are not being drilled on the importance of hand-washing after defecation and before eating.
In vitro antimicrobial susceptibility pattern of isolates
Sulfonamide and trimethoprime
Drug resistance patterns of Shigella isolates
Number and percentage of resistant isolates n = 10)
AMX, NA, SXT
A, C, NA, SXT
A, CN, CRO, SXT
AMX, A, CN, SXT
AMX, A, C, NA, SXT
AMX, A, NA, OFX, SXT
AMX, A, C, NA, SXT
AMX, C, CN, CRO, OFX, NA, SXT
This study which highlights the epidemiologic pattern of shigellosis in the Buea Health District however has a limitation including the inability to determine the species of Shigella or to serotype them. Information that could have given an idea of the severity of the species involved. However according to WHO , reporting any isolate of Shigella species is a major step in disease surveillance and helps in taking actions that lessen the risk of serious complications, spreading and death in the population.
This work has revealed that the prevalence rate of shigellosis in the Buea Health District in Cameroon stands at 4.5%. The majority of Shigella isolates are from the paediatric population (children < 15 years) with an infection rate of 7.89%. This condition is linked to the poor hygienic conditions prevailing in the area. The antibiotic susceptibility testing has revealed that these Shigella spp are multiresistant to currently used antibiotics including extended-spectrum beta-lactamses (ESBLs) as well as increasing evidence of resistance to quinolones. Azithromycin was found to be the drug of choice for shigellosis in this setting.
A total of 223 individuals comprising of 90 males and 133 females, aged 1 month to 72 years old were recruited in the study. The participants were patients referred to the laboratory for stool analysis from the in-patient and out-patient departments of the Regional Hospital Annex, Buea and the Kahwa Sumbele Medical Centre Bomaka, all within the Buea Health District. Their informed consent was souk and obtained and an ethical clearance and authorization to collect specimen and data for research was obtained from the South West Regional Delegation of Public Health Ref No. R11/MPH/SWR/RDPH/FP/5489/97 of the 06/04/2010. An estimate of the required number of participants was obtained using a formula for estimating sample size for proportions. The prevalence used in this formula was derived from a previous work . Isolation, morphological and biochemical identification of Shigella spp were done according to standard methods . The confirmed isolates were subjected to antimicrobial susceptibility tests by disc diffusion method [29–31].
(For details of the methods used see Additional file 1).
The authors acknowledge with thanks, the University of Buea Departmental Research Grant (Department of Medical Laboratory Sciences) for sponsoring this work.
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