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Sekwadi P, Smith AM, Maruma W, Mongologa G, Tsele G, Ngomane M, Tau N, Williams S, Disenyeng B, Sebiloane M, Johnston L, Erasmus L, Thomas J. A Prolonged Outbreak of Enteric Fever Associated With Illegal Miners in the City of Matlosana, South Africa, November 2020-September 2022. Open Forum Infect Dis 2024; 11:ofae118. [PMID: 38505295 PMCID: PMC10950048 DOI: 10.1093/ofid/ofae118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Accepted: 02/27/2024] [Indexed: 03/21/2024] Open
Abstract
Background In South Africa, the annual incidence of enteric fever averaged 0.1 per 100 000 persons between 2003 and 2018. During 2021 an increase in the number of enteric fever cases was observed. An outbreak investigation was conducted to determine the magnitude and source of the outbreak. Methods We performed a cross-sectional descriptive study. Data were collected through telephonic or face-to-face interviews with cases or proxies via a standardized case investigation form. Whole genome sequencing was performed on all Salmonella Typhi isolates. Drinking water samples were collected, tested, and analyzed. Descriptive analysis was performed with Microsoft Excel. Results Between January 2020 and September 2022, a cluster of 53 genetically highly related Salmonella Typhi isolates was identified from 5 provinces in South Africa. Isolates associated with the cluster showed ≤5 allelic differences, as determined following core genome multilocus sequence typing analysis. Most cases (60%, 32/53) were in the North West province. Males represented 68% (36/53). Of these, 72% (26/36) were aged 15 to 49 years, with a median age of 31 years. Where occupation was known within this age group, 78% (14/18) were illegal gold miners. Illegal miners reported illness onset while working underground. Five municipal tap water samples were tested and showed no evidence of fecal contamination. Conclusions This outbreak predominantly affected illegal gold miners, likely due to the consumption of contaminated groundwater while working in a gold mine shaft. In addition, this investigation highlights the value of whole genome sequencing to detect clusters and support epidemiologic investigation of enteric fever outbreaks.
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Affiliation(s)
- Phuti Sekwadi
- Centre for Enteric Diseases, National Institute for Communicable Diseases, National Health Laboratory Service, Johannesburg, South Africa
| | - Anthony Marius Smith
- Centre for Enteric Diseases, National Institute for Communicable Diseases, National Health Laboratory Service, Johannesburg, South Africa
- Department of Medical Microbiology, Faculty of Health Sciences, School of Medicine, University of Pretoria, Pretoria, South Africa
| | - Wellington Maruma
- Division of Public Health Surveillance and Response, National Institute for Communicable Diseases, National Health Laboratory Service, Johannesburg, South Africa
- Julius Global Health, Julius Center for Health Sciences and Primary Care, University Medical Centre Utrecht, Utrecht University, Utrecht, the Netherlands
| | - Gift Mongologa
- Health Programmes Directorate, North West Provincial Department of Health, Mahikeng, South Africa
| | - Grace Tsele
- Health Programmes Directorate, North West Provincial Department of Health, Mahikeng, South Africa
| | - Mimmy Ngomane
- Centre for Enteric Diseases, National Institute for Communicable Diseases, National Health Laboratory Service, Johannesburg, South Africa
| | - Nomsa Tau
- Centre for Enteric Diseases, National Institute for Communicable Diseases, National Health Laboratory Service, Johannesburg, South Africa
| | - Shannon Williams
- Centre for Enteric Diseases, National Institute for Communicable Diseases, National Health Laboratory Service, Johannesburg, South Africa
| | - Bolele Disenyeng
- Centre for Enteric Diseases, National Institute for Communicable Diseases, National Health Laboratory Service, Johannesburg, South Africa
| | - Mahlaku Sebiloane
- South African Field Epidemiology Training Program, National Institute for Communicable Diseases, National Health Laboratory Service, Johannesburg, South Africa
| | - Leigh Johnston
- South African Field Epidemiology Training Program, National Institute for Communicable Diseases, National Health Laboratory Service, Johannesburg, South Africa
| | - Linda Erasmus
- Centre for Enteric Diseases, National Institute for Communicable Diseases, National Health Laboratory Service, Johannesburg, South Africa
| | - Juno Thomas
- Centre for Enteric Diseases, National Institute for Communicable Diseases, National Health Laboratory Service, Johannesburg, South Africa
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Johnston PI, Bogue P, Chirambo AC, Mbewe M, Prakash R, Kandoole-Kabwere V, Lester R, Darton T, Baker S, Gordon MA, Meiring JE. Bacterial shedding and serologic responses following an outbreak of Salmonella Typhi in an endemic cohort. BMC Infect Dis 2023; 23:416. [PMID: 37340341 DOI: 10.1186/s12879-023-08385-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Accepted: 06/08/2023] [Indexed: 06/22/2023] Open
Abstract
BACKGROUND Salmonella enterica serovar Typhi (Salmonella Typhi) is the cause of typhoid fever. Salmonella Typhi may be transmitted through shedding in the stool, which can continue after recovery from acute illness. Shedding is detected by culturing stool, which is challenging to co-ordinate at scale. We hypothesised that sero-surveillance would direct us to those shedding Salmonella Typhi in stool following a typhoid outbreak. METHODS In 2016 a typhoid outbreak affected one in four residents of a Nursing School in Malosa, Malawi. The Department of Health asked for assistance to identify nursing students that might spread the outbreak to other health facilities. We measured IgG antibody titres against Vi capsular polysaccharide (anti-Vi IgG) and IgM / IgG antibodies against H:d flagellin (anti-H:d) three and six months after the outbreak. We selected participants in the highest and lowest deciles for anti-Vi IgG titre (measured at visit one) and obtained stool for Salmonella culture and PCR. All participants reported whether they had experienced fever persisting for three days or more during the outbreak (in keeping with the WHO definitions of 'suspected typhoid'). We tested for salmonellae in the Nursing School environment. RESULTS We obtained 320 paired serum samples from 407 residents. We cultured stool from 25 residents with high anti-Vi IgG titres and 24 residents with low titres. We did not recover Salmonella Typhi from stool; four stool samples yielded non-typhoidal salmonellae; one sample produced a positive PCR amplification for a Salmonella Typhi target. Median anti-Vi and anti-H:d IgG titres fell among participants who reported persistent fever. There was a smaller fall in anti-H:d IgG titres among participants who did not report persistent fever. Non-typhoidal salmonellae were identified in water sampled at source and from a kitchen tap. CONCLUSION High titres of anti-Vi IgG did not identify culture-confirmed shedding of Salmonella Typhi. There was a clear serologic signal of recent typhoid exposure in the cohort, represented by waning IgG antibody titres over time. The presence of non-typhoidal salmonellae in drinking water indicates sub-optimal sanitation. Developing methods to detect and treat shedding remains an important priority to complement typhoid conjugate vaccination in efforts to achieve typhoid elimination.
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Affiliation(s)
- Peter I Johnston
- Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, UK.
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi.
| | - Patrick Bogue
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi
| | - Angeziwa Chunga Chirambo
- Department of Medical Laboratory Sciences, Kamuzu University of Health Sciences, Blantyre, Malawi
| | - Maurice Mbewe
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi
| | - Reenesh Prakash
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi
| | | | - Rebecca Lester
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi
| | - Thomas Darton
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, South Yorkshire, UK
| | - Stephen Baker
- Cambridge Institute of Therapeutic Immunology and Infectious Disease, University of Cambridge, Cambridge, UK
| | - Melita A Gordon
- Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, UK
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi
| | - James E Meiring
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, South Yorkshire, UK
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Vanderslott S, Kumar S, Adu-Sarkodie Y, Qadri F, Zellweger RM. Typhoid Control in an Era of Antimicrobial Resistance: Challenges and Opportunities. Open Forum Infect Dis 2023; 10:S47-S52. [PMID: 37274528 PMCID: PMC10236512 DOI: 10.1093/ofid/ofad135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023] Open
Abstract
Historically, typhoid control has been achieved with water and sanitation interventions. Today, in an era of rising antimicrobial resistance (AMR), two World Health Organization-prequalified vaccines are available to accelerate control in the shorter term. Meanwhile, water and sanitation interventions could be implemented in the longer term to sustainably prevent typhoid in low- and middle-income countries. This article first approaches typhoid control from a historical perspective, subsequently presents how vaccination could complement water and sanitation activities, and finally discusses the challenges and opportunities for impactful control of typhoid infection. It also addresses data blind spots and knowledge gaps to focus on for typhoid control and to ultimately progress towards elimination. This article presents a synthesis of discussions held in December 2021 during a roundtable session at the "12th International Conference on Typhoid and Other Invasive Salmonelloses".
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Affiliation(s)
- Samantha Vanderslott
- Oxford Vaccine Group, Department of Paediatrics, University of Oxford, Oxford, United Kingdom and NIHR Oxford Biomedical Research Centre, Oxford, Oxfordshire, United Kingdom
| | - Supriya Kumar
- Enteric and Diarrheal Diseases, Bill & Melinda Gates Foundation, Seattle, Washington, USA
| | - Yaw Adu-Sarkodie
- Kwame Nkrumah University of Science and Technology, Kumasi, Ghana
| | - Firdausi Qadri
- International Centre for Diarrhoeal Disease Research, Dhaka, Bangladesh
| | - Raphaël M Zellweger
- Correspondence: Raphaël M. Zellweger, MSc, PhD, Epidemiology , Public Health & Impact, International Vaccine Institute, 1, Gwanak-ro, Gwanak-gu, Seoul 08826, South Korea. ()
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Burrows H, Antillón M, Gauld JS, Kim JH, Mogasale V, Ryckman T, Andrews JR, Lo NC, Pitzer VE. Comparison of model predictions of typhoid conjugate vaccine public health impact and cost-effectiveness. Vaccine 2023; 41:965-975. [PMID: 36586741 PMCID: PMC9880559 DOI: 10.1016/j.vaccine.2022.12.032] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 12/14/2022] [Accepted: 12/15/2022] [Indexed: 12/31/2022]
Abstract
Models are useful to inform policy decisions on typhoid conjugate vaccine (TCV) deployment in endemic settings. However, methodological choices can influence model-predicted outcomes. To provide robust estimates for the potential public health impact of TCVs that account for structural model differences, we compared four dynamic and one static mathematical model of typhoid transmission and vaccine impact. All models were fitted to a common dataset of age-specific typhoid fever cases in Kolkata, India. We evaluated three TCV strategies: no vaccination, routine vaccination at 9 months of age, and routine vaccination at 9 months with a one-time catch-up campaign (ages 9 months to 15 years). The primary outcome was the predicted percent reduction in symptomatic typhoid cases over 10 years after vaccine introduction. For three models with economic analyses (Models A-C), we also compared the incremental cost-effectiveness ratios (ICERs), calculated as the incremental cost (US$) per disability-adjusted life-year (DALY) averted. Routine vaccination was predicted to reduce symptomatic cases by 10-46 % over a 10-year time horizon under an optimistic scenario (95 % initial vaccine efficacy and 19-year mean duration of protection), and by 2-16 % under a pessimistic scenario (82 % initial efficacy and 6-year mean protection). Adding a catch-up campaign predicted a reduction in incidence of 36-90 % and 6-35 % in the optimistic and pessimistic scenarios, respectively. Vaccine impact was predicted to decrease as the relative contribution of chronic carriers to transmission increased. Models A-C all predicted routine vaccination with or without a catch-up campaign to be cost-effective compared to no vaccination, with ICERs varying from $95-789 per DALY averted; two models predicted the ICER of routine vaccination alone to be greater than with the addition of catch-up campaign. Despite differences in model-predicted vaccine impact and cost-effectiveness, routine vaccination plus a catch-up campaign is likely to be impactful and cost-effective in high incidence settings such as Kolkata.
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Affiliation(s)
- Holly Burrows
- Yale School of Public Health, Yale University, New Haven, CT, USA.
| | - Marina Antillón
- Yale School of Public Health, Yale University, New Haven, CT, USA; Swiss Tropical and Public Health Institute, Allschwil, Switzerland; University of Basel, Basel, Switzerland
| | - Jillian S Gauld
- Institute for Disease Modeling, Bill & Melinda Gates Foundation, Seattle, WA, USA
| | - Jong-Hoon Kim
- Public Health, Access, and Vaccine Epidemiology (PAVE) Unit, International Vaccine Institute, Seoul, Republic of Korea
| | - Vittal Mogasale
- Policy and Economic Research Department, International Vaccine Institute, Seoul 08826, Republic of Korea
| | - Theresa Ryckman
- Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Jason R Andrews
- Division of Infectious Diseases and Geographic Medicine, Stanford University School of Medicine, Stanford, CA, USA
| | - Nathan C Lo
- Division of HIV, Infectious Diseases, and Global Medicine, University of California, San Francisco, San Francisco, CA, USA
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Macrophage Cell Lines and Murine Infection by Salmonella enterica Serovar Typhi L-Form Bacteria. Infect Immun 2022; 90:e0011922. [PMID: 35587200 DOI: 10.1128/iai.00119-22] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Antibiotic resistance of pathogenic bacteria has emerged as a major threat to public health worldwide. While stable resistance due to the acquisition of genomic mutations or plasmids carrying antibiotic resistance genes is well established, much less is known about the temporary and reversible resistance induced by antibiotic treatment, such as that due to treatment with bacterial cell wall-inhibiting antibiotics such as ampicillin. Typically, ampicillin concentration in the blood and other tissues gradually increases over time after initiation of the treatment. As a result, the bacterial population is exposed to a concentration gradient of ampicillin during the treatment of infectious diseases. This is different from in vitro drug testing, where the organism is exposed to fixed drug concentrations from the beginning until the end. To mimic the mode of antibiotic exposure of microorganisms within host tissues, we cultured the wild-type, ampicillin-sensitive Salmonella enterica serovar Typhi Ty2 strain (S. Typhi Ty2) in the presence of increasing concentrations of ampicillin over a period of 14 days. This resulted in the development of a strain that displayed several features of the so-called L-form of bacteria, including the absence of the cell wall, altered shape, and lower growth rate compared with the parental form. Studies of the pathogenesis of S. Typhi L-form showed efficient infection of the murine and human macrophage cell lines. More importantly, S. Typhi L-form was also able to establish infection in a mouse model to the extent comparable to its parental form. These results suggested that L-form generation following the initiation of treatment with antibiotics could lead to drug escape of S. Typhi and cell to cell (macrophages) spread of the bacteria, which sustain the infection. Oral infection by the L-form bacteria underscores the potential of rapid disease transmission through the fecal-oral route, highlighting the need for new approaches to decrease the reservoir of infection.
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