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| ORIGINAL ARTICLE |
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| Year : 2019 | Volume
: 6
| Issue : 1 | Page : 21-26 |
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Circulating serotypes and antimicrobial susceptibility pattern of Vibrio cholerae isolates from insurgency-stricken Maiduguri, northeastern Nigeria
Musa A Garbati1, Abubakar S Baba2, Abubakar Mursal2, Galadima B Gadzama2
1 Department of Medicine, University of Maiduguri, Borno State, Nigeria
2 Department of Medical Microbiology, University of Maiduguri Teaching Hospital, Maiduguri, Nigeria
| Date of Web Publication | 10-Oct-2019 |
Correspondence Address:
Dr. Musa A Garbati
Department of Medicine, University of Maiduguri, P.M.B. 1069, Borno State, Maiduguri
Nigeria
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/ssajm.ssajm_12_19
Background: Cholera has continued to be a global threat to public health largely due to lack of social development. In endemic areas, outbreaks usually occur when war or civil unrest disrupts public sanitation services contaminating food and water supplies. Extensive and injudicious use of antimicrobials has led to the emergence of Vibrio cholerae strains that are resistant to several antibiotics. Aim: This study aims to highlight the recent cholera outbreak in the northeastern Nigeria and its characteristics, regarding the circulating serotypes and the antibiotic susceptibility of the isolates. This information is important for the effective control of future outbreaks using vaccination and antibiotics. Materials and Methods: We retrospectively reviewed 102 consecutive fresh diarrheic stool samples at the University of Maiduguri Teaching Hospital, Maiduguri, Nigeria, from July to December 2018. All samples were analyzed by culture and serology according to standard procedures. Antimicrobial susceptibility testing was performed with the Kirby-Bauer disk diffusion method on Mueller-Hinton agar. Results: Stool samples from 102 suspected cholera cases were received in the medical microbiology laboratory department for evaluation. Males made up 54% of the study population, aged 3 months to 70 years. Most of the cases were from camps harboring large numbers of internally displaced persons. Serotyping revealed that the sero group Ogawa was responsible. The strains were 100% sensitive to amikacin, ciprofloxacin, and cefotaxime, with varying resistance to trimethoprim/sulfamethoxazole and tetracycline. Conclusion: Our study highlights the continuing social problems associated with cholera epidemics and the significance of regular serologic and antimicrobial resistance surveillance of V. cholerae strains in our environment for proper management of cases.
Keywords: Antibiogram, internally displaced persons, Maiduguri, Nigeria, serotype, Vibrio cholera
How to cite this article:
Garbati MA, Baba AS, Mursal A, Gadzama GB. Circulating serotypes and antimicrobial susceptibility pattern of Vibrio cholerae isolates from insurgency-stricken Maiduguri, northeastern Nigeria. Sub-Saharan Afr J Med 2019;6:21-6 |
How to cite this URL:
Garbati MA, Baba AS, Mursal A, Gadzama GB. Circulating serotypes and antimicrobial susceptibility pattern of Vibrio cholerae isolates from insurgency-stricken Maiduguri, northeastern Nigeria. Sub-Saharan Afr J Med [serial online] 2019 [cited 2023 Mar 21];6:21-6. Available from: https://www.ssajm.org/text.asp?2019/6/1/21/268784 |
| Introduction | |  |
Cholera is an acute diarrheal disease caused by the bacterium Vibrio cholerae acquired following the ingestion of contaminated food or water. Cholera transmission is closely linked to inadequate access to clean water and sanitation facilities. Cholera remains a global threat to public health and an indicator of poor hygiene and lack of social development. The disease usually occurs in outbreaks, especially in developing countries, in either endemic or epidemic proportions. The current cholera pandemic started in 1961, reaching West Africa and Nigeria in the late 1970. The first recorded cases of cholera in Nigeria occurred in a village near Lagos, on December 26, 1970, causing 22,931 cases and 2945 deaths, with a case fatality rate (CFR) of 12.8%.[1] In Nigeria, cholera occurs as a seasonal disease, mostly during rainy seasons. However, in most of the affected areas, the disease is endemic as the cases occur round the year, although with different magnitudes.
Typical at-risk areas include peri-urban slums, and camps for internally displaced persons (IDPs) or refugees, with lack of minimum requirements of clean water and sanitation. The consequences of a humanitarian crisis − such as disruption of water and sanitation systems, or the displacement of populations to inadequate and overcrowded camps − can increase the risk of cholera transmission. In severe cases, the disease is associated with significant morbidity and mortality. It is estimated that every year, approximately 1.3 to 4.0 million cases and 21,000 to 143,000 deaths occur worldwide due to cholera.[2] On October 29, 2018, a total of 42,466 suspected cases including 830 deaths with a CFR of 1.95% have been reported from 20 states (Adamawa, Anambra, Bauchi, Borno, Ebonyi, FCT, Gombe, Jigawa, Kaduna, Kano, Katsina, Kebbi, Kogi, Kwara, Nasarawa, Niger, Plateau, Yobe, Sokoto, and Zamfara) since the beginning of 2018.
Two biotypes of V. cholerae are described. The more recent “El Tor” differs from the “classical” in being hemolytic and resistant to polymyxin B. It persists longer in the environment than classical biotype, and a greater proportion of those infected are asymptomatic. Both classical and El Tor V. cholerae are divided into three serotypes (Ogawa, Inaba, Hikojima) by antisera to the O antigen. Strains that do not react with the O antisera are referred to “non-O1” and do not usually cause epidemics.[3],[4]
Rehydration remains the primary treatment for cholera, with antimicrobial drug therapy being recommended for severe cases.[5] Although V. cholerae maintains susceptibility to some of the antibiotics used for treatment, the occurrences of infections due to multidrug-resistant V. cholerae have long been observed,[6] with new resistance profiles during previous epidemics in Cameroon.[7],[8],[9],[10],[11],[12] Drug-resistant V. cholerae strains are, therefore, a global health concern as infections resulting from these could be more severe and difficult to treat. Increased resistance could lead to higher CFRs, prolonged hospitalizations, increased health-care costs, and probably more secondary infections.[13]
Drug-resistant V. cholerae strains are, therefore, a global health concern as infections resulting from these could be more severe and difficult to treat. In addition, there could be higher CFRs, prolonged hospitalizations, increased health-care costs, and probably more secondary infections. Absence of antimicrobial stewardship programs and the abnormal use of antimicrobials in these regions have been thought to be the driving factors for this escalation. During the course of the seventh pandemic, a new variant cholera biotype called the “hybrid” or “atypical” biotype with mixed markers of the classical and El Tor biotypes has emerged.[14] This atypical El Tor biotype is associated with higher virulence and more widespread antibiotic resistance.[14]
Cholera outbreaks have been ongoing in Nigeria for the past 4 decades. Unfortunately, the specific strains responsible and their antibiotic resistance patterns are not well studied.[15] The present study aims to report on the circulating serotype of V. cholerae strains responsible for the recent epidemic in Borno State and their antibiogram. This will serve as a guide for the empiric use of antimicrobials to treat cases of cholera in the northeast region of Nigeria.
| Methodology | | |
Study samples
This retrospective study was conducted from July to December 2018 at the University of Maiduguri Teaching Hospital (UMTH), Maiduguri, Nigeria. A total of 102 consecutive fresh diarrheic stool samples submitted to the Department of Microbiology, UMTH, from patients of all age groups suspected to have cholera were analyzed. Only one sample was analyzed for each patient. All samples were transported (in Cary-Blair medium) immediately and processed. In the laboratory, stool samples were examined for macroscopic findings. In addition, a hanging drop preparation was made to look for darting motility and a stool routine microscopic examination was performed for pus cells, red blood cells, and cysts and trophozoites of parasites. The ethical committee of UMTH approved the study.
Laboratory diagnosis
Isolation and confirmation of V. cholerae strains
Samples transported in Cary-Blair medium were separately inoculated into alkaline peptone water (pH 8.6) for growth enrichment at 37°C for 24 h. Each bacterial culture was then subcultured on thiosulfate-citrate-bile salts-sucrose agar at 37°C for 24 h. Any V. cholerae-like colonies were subjected to conventional biochemical tests as per standard microbiological techniques.[16]
Serologic characterization
Serologic testing by slide agglutination using serogroup-specific O1 polyvalent and O139 Bengal antisera and monospecific antisera for Ogawa and Inaba strains (Denka Seiken Company Limited, Tokyo, Japan) was further done on organisms suspected to be V. cholerae.
Characterization of the isolated strains
Oxidase reaction was done by transferring the overnight on tryptic soya agar growth using a wood applicator stick to a filter paper saturated with oxidase reagent (1% N,N,N,N’-tetramethyl-p-phenylenediamine.2HCl). A dark purple color developing within 10 s indicates a positive test growth.
Antibiotics susceptibility testing
Antimicrobial susceptibility testing was performed with the Kirby-Bauer disk diffusion method on Mueller-Hinton agar. The Escherichia coli reference strain ATCC 25922 served as a control. The isolates were tested against the following antimicrobials: ciprofloxacin (5 µg), chloramphenicol (30 µg), amikacin (30 µg), sulfamethoxazole/trimethoprim (1.25 µg + 23.75 µg), tetracycline (30 µg), and cefotaxime (30 µg) (Oxoid, Basingstoke, UK). Diameters were interpreted according to the 2015 Clinical and Laboratory Standards Institute guidelines as resistant, susceptible, or intermediate.[17] Generated data were collected on an excel spreadsheet and analyzed, and subsequently presented as tables, charts, and figures.
| Results | | |
Between July and December 2018, stool samples from 102 suspected cholera cases were received in the medical microbiology laboratory department of the UMTH for evaluation. The current epidemic started in the epidemic week 33 of 2018 when 56 cases were reported to the Nigeria centre for disease control (NCDC) and ended in the epidemic week 47 in 2018 with only six cases.
Males made up 54% of the study population. The age distribution is presented in [Figure 1]. All age groups were affected by the outbreak with 27% being aged 15 years or less, whereas 67% were aged between 16 and 45 years. Most of the cases were from Monguno, Muna, and Dikwa, areas plagued by the insurgency currently ravaging the northeast subregion and harboring large numbers of IDPs. The camps are overcrowded with inadequate sewage and refuse disposal and sanitation facilities. Shallow boreholes served as their major source of drinking water.
The peak of the epidemic was observed in the month of September 2018 with 80 (75%) cases with a sharp decline in October and November 2018 [Figure 2]. Out of the presumptive cholera cases, 57 (56%) of the samples yielded Gram-negative rods on thiosulfate-citrate-bile salts-sucrose agar, later identified as V. cholerae. Serotyping was done on the samples and 100% were positive for the sero group Ogawa.
The antibiogram of the V. cholerae strains isolated during the study period is summarized in [Table 1]. For logistic reasons, only four of the isolates were randomly selected and subjected to antimicrobial susceptibility during the outbreak, as it was not feasible to test all samples. All the strains (100%) were sensitive to amikacin, ciprofloxacin, and cefotaxime, a third-generation cephalosporin. Resistance rate to trimethoprim/sulfamethoxazole and tetracycline, some of the common antibiotics used in treating cholera, was 50% and 75%, respectively.
| Discussion | | |
We observed that the recent cholera outbreak in Borno State affected all age groups; the age range was 3 months to 70 years, 27% of the affected population being 15 years or less. The 36 to 45-year age group was mostly affected (28%). Most of the cases were among IDPs residing in camps with inadequate water supply and sanitation facilities. The peak of the epidemic was observed in the month of September 2018 with 80 (75%) cases. There was a sharp decline in October and November; a similar finding was also reported earlier.[18]
The results from this study showed that the V. cholerae strains isolated from the 2018 outbreak in Maiduguri, northeastern Nigeria were all of Ogawa serotypes. This finding only goes to buttress previous findings that reported the Ogawa serotype[19],[20],[21] being dominant. This is in contrast to cholera outbreaks in northern Nigeria in 1985 in which both Inaba and Ogawa strains were implicated[22] and the 2011 outbreak in Calabar, southern Nigeria, in which the Hikojima serotype was responsible.[23] In a recent systematic review of published articles across sub-Saharan Africa in 2018,[24] the Ogawa serotype was also predominant (27.6%) compared with Inaba (10.3%), Ogawa/Inaba coexisting together (20.7%), and coexistence of Inaba/Ogawa/Hikojima (3.4%).
The antibiogram of the V. cholerae strains isolated during the study period is summarized in [Table 1]. All the strains (100%) were sensitive to amikacin, ciprofloxacin, and cefotaxime, a third-generation cephalosporin. Resistance rate to trimethoprim/sulfamethoxazole and tetracycline, some of the common antibiotics used in treating cholera, was 50% and 75%, respectively. In contrast to our findings, Mohammed et al.[24] reported a fluoroquinolones resistance rate of 44%. Resistance to sulfonamides was also high (92%),[24] which is in keeping with our findings. One hundred percent of our isolates were susceptible to the third-generation cephalosporins as compared to 80% from a recent report.[24]Drug resistance was high (75%) among our isolates for tetracycline, a drug considered the choice for the treatment of cholera in the previous studies.[25] Other studies have also reported the rising tetracycline resistance among V. cholerae O1 strains involved in major epidemics in Latin America, Tanzania, Bangladesh, and India.[26] This is likely due to extensive use of this class of drug for treatment and prophylaxis.
| Conclusion | | |
Cholera has remained endemic in Nigeria since its first report in 1970, and in recent times, successive epidemics of the disease have occurred across the six geopolitical zones of the country. Data on pathogen and host factors promoting pathogenesis of severe disease is strongly needed for formulating appropriate surveillance, control, and treatment measures against future cholera outbreaks. Amikacin, ciprofloxacin, and cefotaxime, have maintained 100% susceptibility whereas borderline susceptibility has been detected to other commonly used drugs such as trimethoprim/sulfamethoxazole and tetracycline. The empiric use of these latter agents against cholera, especially during outbreaks, needs to be reconsidered.
Financial support and sponsorship
None.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1]
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