Milagritos D. Tapia

Intracontinental spread of human invasive Salmonella Typhimurium pathovariants in sub-Saharan Africa

A highly invasive form of non-typhoidal Salmonella (iNTS) disease has recently been documented in many countries in sub-Saharan Africa. The most common Salmonella enterica serovar causing this disease is Typhimurium (Salmonella Typhimurium). We applied whole-genome sequence–based phylogenetic methods to define the population structure of sub-Saharan African invasive Salmonella Typhimurium isolates and compared these to global Salmonella Typhimurium populations. Notably, the vast majority of sub-Saharan invasive Salmonella Typhimurium isolates fell within two closely related, highly clustered phylogenetic lineages that we estimate emerged independently ∼52 and ∼35 years ago in close temporal association with the current HIV pandemic. Clonal replacement of isolates from lineage I by those from lineage II was potentially influenced by the use of chloramphenicol for the treatment of iNTS disease. Our analysis suggests that iNTS disease is in part an epidemic in sub-Saharan Africa caused by highly related Salmonella Typhimurium lineages that may have occupied new niches associated with a compromised human population and antibiotic treatment.

Immunogenicity and Safety of a Meningococcal A Conjugate Vaccine in Africans

BACKGROUND Group A meningococci are the source of major epidemics of meningitis in Africa. An affordable, highly immunogenic meningococcal A conjugate vaccine is needed. METHODS We conducted two studies in Africa to evaluate a new MenA conjugate vaccine (PsA-TT). In study A, 601 children, 12 to 23 months of age, were randomly assigned to receive PsA-TT, a quadrivalent polysaccharide reference vaccine (PsACWY), or a control vaccine (Haemophilus influenzae type b conjugate vaccine [Hib-TT]). Ten months later, these children underwent another round of randomization within each group to receive a full dose of PsA-TT, a one-fifth dose of PsACWY, or a full dose of Hib-TT, with 589 of the original participants receiving a booster dose. In study B, 900 subjects between 2 and 29 years of age were randomly assigned to receive PsA-TT or PsACWY. Safety and reactogenicity were evaluated, and immunogenicity was assessed by measuring the activity of group A serum bactericidal antibody (SBA) with rabbit complement and performing an IgG group A-specific enzyme-linked immunosorbent assay. RESULTS In study A, 96.0% of the subjects in the PsA-TT group and 63.7% of those in the PsACWY group had SBA titers that were at least four times as high as those at baseline; in study B, 78.2% of the subjects in the PsA-TT group and 46.2% of those in the PsACWY group had SBA titers that were at least four times as high as those at baseline. The geometric mean SBA titers in the PsA-TT groups in studies A and B were greater by factors of 16 and 3, respectively, than they were in the PsACWY groups (P<0.001). In study A, the PsA-TT group had higher antibody titers at week 40 than the PsACWY group and had obvious immunologic memory after receiving a polysaccharide booster vaccine. Safety profiles were similar across vaccine groups, although PsA-TT recipients were more likely than PsACWY recipients to have tenderness and induration at the vaccination site. Adverse events were consistent with age-specific morbidity in the study areas; no serious vaccine-related adverse events were reported. CONCLUSIONS The PsA-TT vaccine elicited a stronger response to group A antibody than the PsACWY vaccine. (Funded by the Meningitis Vaccine Project through a grant from the Bill and Melinda Gates Foundation; Controlled-Trials.com numbers, ISRCTN78147026 and ISRCTN87739946.).

Use of ChAd3-EBO-Z Ebola virus vaccine in Malian and US adults, and boosting of Malian adults with MVA-BN-Filo: a phase 1, single-blind, randomised trial, a phase 1b, open-label and double-blind, dose-escalation trial, and a nested, randomised, double-blind, placebo-controlled trial

Summary Background The 2014 west African Zaire Ebola virus epidemic prompted worldwide partners to accelerate clinical development of replication-defective chimpanzee adenovirus 3 vector vaccine expressing Zaire Ebola virus glycoprotein (ChAd3-EBO-Z). We aimed to investigate the safety, tolerability, and immunogenicity of ChAd3-EBO-Z in Malian and US adults, and assess the effect of boosting of Malians with modified vaccinia Ankara expressing Zaire Ebola virus glycoprotein and other filovirus antigens (MVA-BN-Filo). Methods In the phase 1, single-blind, randomised trial of ChAd3-EBO-Z in the USA, we recruited adults aged 18–65 years from the University of Maryland medical community and the Baltimore community. In the phase 1b, open-label and double-blind, dose-escalation trial of ChAd3-EBO-Z in Mali, we recruited adults 18–50 years of age from six hospitals and health centres in Bamako (Mali), some of whom were also eligible for a nested, randomised, double-blind, placebo-controlled trial of MVA-BN-Filo. For randomised segments of the Malian trial and for the US trial, we randomly allocated participants (1:1; block size of six [Malian] or four [US]; ARB produced computer-generated randomisation lists; clinical staff did randomisation) to different single doses of intramuscular immunisation with ChAd3-EBO-Z: Malians received 1 × 1010 viral particle units (pu), 2·5 × 1010 pu, 5 × 1010 pu, or 1 × 1011 pu; US participants received 1 × 1010 pu or 1 × 1011 pu. We randomly allocated Malians in the nested trial (1:1) to receive a single dose of 2 × 108 plaque-forming units of MVA-BN-Filo or saline placebo. In the double-blind segments of the Malian trial, investigators, clinical staff, participants, and immunology laboratory staff were masked, but the study pharmacist (MK), vaccine administrator, and study statistician (ARB) were unmasked. In the US trial, investigators were not masked, but participants were. Analyses were per protocol. The primary outcome was safety, measured with occurrence of adverse events for 7 days after vaccination. Both trials are registered with ClinicalTrials.gov, numbers NCT02231866 (US) and NCT02267109 (Malian). Findings Between Oct 8, 2014, and Feb 16, 2015, we randomly allocated 91 participants in Mali (ten [11%] to 1 × 1010 pu, 35 [38%] to 2·5 × 1010 pu, 35 [38%] to 5 × 1010 pu, and 11 [12%] to 1 × 1011 pu) and 20 in the USA (ten [50%] to 1 × 1010 pu and ten [50%] to 1 × 1011 pu), and boosted 52 Malians with MVA-BN-Filo (27 [52%]) or saline (25 [48%]). We identified no safety concerns with either vaccine: seven (8%) of 91 participants in Mali (five [5%] received 5 × 1010 and two [2%] received 1 × 1011 pu) and four (20%) of 20 in the USA (all received 1 × 1011 pu) given ChAd3-EBO-Z had fever lasting for less than 24 h, and 15 (56%) of 27 Malians boosted with MVA-BN-Filo had injection-site pain or tenderness. Interpretation 1 × 1011 pu single-dose ChAd3-EBO-Z could suffice for phase 3 efficacy trials of ring-vaccination containment needing short-term, high-level protection to interrupt transmission. MVA-BN-Filo boosting, although a complex regimen, could confer long-lived protection if needed (eg, for health-care workers). Funding Wellcome Trust, Medical Research Council UK, Department for International Development UK, National Cancer Institute, Frederick National Laboratory for Cancer Research, Federal Funds from National Institute of Allergy and Infectious Diseases.

Identification by PCR of Non-typhoidal Salmonella enterica Serovars Associated with Invasive Infections among Febrile Patients in Mali

Background In sub-Saharan Africa, non-typhoidal Salmonella (NTS) are emerging as a prominent cause of invasive disease (bacteremia and focal infections such as meningitis) in infants and young children. Importantly, including data from Mali, three serovars, Salmonella enterica serovar Typhimurium, Salmonella Enteritidis and Salmonella Dublin, account for the majority of non-typhoidal Salmonella isolated from these patients. Methods We have extended a previously developed series of polymerase chain reactions (PCRs) based on O serogrouping and H typing to identify Salmonella Typhimurium and variants (mostly I 4,[5],12:i:-), Salmonella Enteritidis and Salmonella Dublin. We also designed primers to detect Salmonella Stanleyville, a serovar found in West Africa. Another PCR was used to differentiate diphasic Salmonella Typhimurium and monophasic Salmonella Typhimurium from other O serogroup B, H:i serovars. We used these PCRs to blind-test 327 Salmonella serogroup B and D isolates that were obtained from the blood cultures of febrile patients in Bamako, Mali. Principal Findings We have shown that when used in conjunction with our previously described O-serogrouping PCR, our PCRs are 100% sensitive and specific in identifying Salmonella Typhimurium and variants, Salmonella Enteritidis, Salmonella Dublin and Salmonella Stanleyville. When we attempted to differentiate 171 Salmonella Typhimurium (I 4,[ 5],12:i:1,2) strains from 52 monophasic Salmonella Typhimurium (I 4,[5],12:i:-) strains, we were able to correctly identify 170 of the Salmonella Typhimurium and 51 of the Salmonella I 4,[5],12:i:- strains. Conclusion We have described a simple yet effective PCR method to support surveillance of the incidence of invasive disease caused by NTS in developing countries.

PCR Method To Identify Salmonella enterica Serovars Typhi, Paratyphi A, and Paratyphi B among Salmonella Isolates from the Blood of Patients with Clinical Enteric Fever

ABSTRACT PCR methodology was developed to identify Salmonella enterica serovars Typhi, Paratyphi A, and Paratyphi B. One multiplex PCR identifies serogroup D, A, and B and Vi-positive strains; another confirms flagellar antigen “d,” “a,” or “b.” Blinded testing of 664 Malian and Chilean Salmonella blood isolates demonstrated 100% sensitivity and specificity.

Potential coverage of a multivalent M protein-based group A streptococcal vaccine

BACKGROUND The greatest burden of group A streptococcal (GAS) disease worldwide is due to acute rheumatic fever (ARF) and rheumatic heart disease (RHD). Safe, effective and affordable vaccines designed to prevent GAS infections that trigger ARF could reduce the overall global morbidity and mortality from RHD. The current study evaluated the potential coverage of a new 30-valent M protein-based vaccine using GAS isolates from school children in Bamako, Mali, a population at high risk for the development of RHD. METHODS The bactericidal activity of rabbit antisera against the 30-valent vaccine was assessed using a collection of GAS isolates recovered during a study of the epidemiology of pharyngitis in Bamako. RESULTS Single isolates representing 42 of 67 emm-types, accounting for 85% of the GAS infections during the study, were evaluated. All (14/14) of the vaccine emm-types in the collection were opsonized (bactericidal killing >50%) and 26/28 non-vaccine types were opsonized. Bactericidal activity was observed against 60% of the total emm-types recovered in Bamako, which accounted for 81% of all infections. CONCLUSIONS Multivalent vaccines comprised of N-terminal M peptides elicit bactericidal antibodies against a broad range of GAS serotypes, indicating that their efficacy may extend beyond the emm-types included in the vaccine.

Efficacy of the oral pentavalent rotavirus vaccine in Mali

The oral, pentavalent rotavirus vaccine (PRV), RotaTeq was assessed for prevention of severe rotavirus gastroenteritis (RVGE) in young children in two multi-site, randomized, placebo-controlled field trials; one in Asia (Vietnam and Bangladesh) and the other in sub-Saharan Africa (Ghana, Kenya and Mali). The efficacy results for the Mali site of the multi-country trial are presented here. We randomly assigned infants in a 1:1 ratio to receive 3 doses of PRV/placebo at approximately 6, 10, and 14 weeks of age. Gastroenteritis episodes were captured passively at the local health centers and by home visits. The primary study outcome was severe RVGE, as defined by a score of ≥ 11 using the Vesikari Clinical Scoring System occurring ≥ 14 days after the third dose until the end of the study. Other efficacy analyses included efficacy against severe RVGE through the first year and during the second years of life, as well as efficacy after receiving at least one dose of vaccine. In total, 1960 infants were enrolled in the trial at the Mali site and sera were collected on a subset of infants (approximately 150) for immunogenicity testing. In the first year of follow-up, largely due to cultural practices to visit traditional healers as the first point of care, the point estimate of efficacy was unreliable: the per protocol vaccine efficacy against severe RVGE was 1% (95% confidence interval [CI]: -431.7, 81.6); the intention-to-treat vaccine efficacy was 42.9% (95% CI: -125.7, 87.7). During the second year of follow-up, after the surveillance system was modified to adapt to local customs and health care seeking practices, the point estimate of per-protocol vaccine efficacy was 19.2% (95% CI: -23.1,47.3%). 82.5% of Malian infants (95% CI: 70.1,91.3%) who received PRV mounted a seroresponse (≥ 3-fold rise from baseline (prevaccination) to post-dose 3 vaccination) of anti-rotavirus immunoglobulin A antibody, with a post third-dose geometric mean titer (GMT) of 31.3 units/mL. By contrast, only 20.0% of placebo recipients (95% CI: 10.0, 33.7%) developed a seroresponse and the post-third dose GMT was 3.2 units/mL. None of the serious clinical adverse events observed were considered to be vaccine-related.

Burden of invasive disease caused by Haemophilus influenzae type b in Bamako, Mali: impetus for routine infant immunization with conjugate vaccine.

Background: Population-based, bacteriologically confirmed disease burden data aid decision makers in African countries pondering whether to introduce Haemophilus influenzae type b (Hib) immunization for infants. Methods: A bacteriology laboratory was established in Hôpital Gabriel Touré, serving Bamako, Mali. Children age 0–15 years with fever ≥39°C or syndromes compatible with invasive bacterial disease (meningitis, etc.) were eligible. From 2 to 5 mL of blood or relevant body fluid were inoculated into Bactec Ped Plus/F medium for automated culture; body fluids were also inoculated directly onto solid media. Hib was confirmed by standard microbiologic techniques and antibiograms generated by disk diffusion. Results: From June 1, 2002 to May 31, 2004, 3592 (87.8%) of 4092 children admitted to Hôpital Gabriel Touré with high fever or suspected invasive bacterial disease were cultured, including 1745 who were 0–11 months old, 1132 who were 1–4 years old and 715 who were 5–15 years old. Hib was isolated from 207 Bamako children, 81 from blood alone and 124 from cerebrospinal fluid (with or without positive blood culture). Of 207 cases 204 (98.5%) occurred in children younger than age 5 years (annual incidence, 45.2/105) and 159 (77%) in infants age 0–11 months (annual incidence, 158.4/105). Peak incidence (370.0 cases/105) and 12 of 21 Hib deaths occurred in 6- to 7-month-olds. Of the Hib isolates, 11.1% were resistant to ampicillin, 32% to chloramphenicol and 0.5% to ceftriaxone. Conclusions: The substantial burden of invasive Hib disease documented in Bamako has prompted the Malian government to introduce routine infant immunization with Hib conjugate.

Distinct Salmonella Enteritidis lineages associated with enterocolitis in high-income settings and invasive disease in low-income settings

An epidemiological paradox surrounds Salmonella enterica serovar Enteritidis. In high-income settings, it has been responsible for an epidemic of poultry-associated, self-limiting enterocolitis, whereas in sub-Saharan Africa it is a major cause of invasive nontyphoidal Salmonella disease, associated with high case fatality. By whole-genome sequence analysis of 675 isolates of S. Enteritidis from 45 countries, we show the existence of a global epidemic clade and two new clades of S. Enteritidis that are geographically restricted to distinct regions of Africa. The African isolates display genomic degradation, a novel prophage repertoire, and an expanded multidrug resistance plasmid. S. Enteritidis is a further example of a Salmonella serotype that displays niche plasticity, with distinct clades that enable it to become a prominent cause of gastroenteritis in association with the industrial production of eggs and of multidrug-resistant, bloodstream-invasive infection in Africa.

Influenza B infection associated with encephalitis: Treatment with oseltamivir

Encephalitis associated with acute influenza infection is unusual in nonepidemic years. A case of a 10-year-old child with influenza B encephalitis and profound weakness who was treated with oseltamivir is presented. This case illustrates several of the unusual findings associated with influenza infections and the result of treatment of influenza B encephalitis with oseltamivir.