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Vibrio cholerae O1 Hybrid El Tor Strains, Asia and Africa

2008-06-01T00:00:00Z

Title: Vibrio cholerae O1 Hybrid El Tor Strains, Asia and Africa Authors: Safia, Asharafus; Sultana, Jinath; Dac Cam, Phung; Mwansa, James; Kong, Richard Y.C. Abstract: Vibrio cholerae is a water-borne pathogen that causes a severe watery diarrhea disease known as cholera. On the basis of variable somatic O antigen composition, >200 serogroups of V. cholerae have been recognized. Classical and El Tor are 2 well-established biotypes within the V. cholerae O1 serogroup, and they can be distinguished by differences in their biochemical reactions or phenotypic traits (1). In addition to phenotypic traits, genetic markers have recently been used in the identification of the biotypes of V. cholerae. For example, the major toxin-coregulated pilus (TCP) gene, tcpA, of the TCP cluster possesses classical- and El Tor–specific alleles that encode identical functions but differ in their DNA sequence composition; however, the rtxC gene of the repeat in toxin (RTX) cluster is present in El Tor strains only and absent in classical strains (2,3). The cholera toxin, encoded by the ctxA and ctxB genes, is the principal toxin produced by V. cholerae O1 and O139 and is responsible for the disease cholera. Heterogeneity within the ctxB gene and protein was first reported in the early 1990s, and, on this basis, 3 ctxB genotypes of the V. cholerae O1 strains have been identified. Based on amino acid residue substitutions at positions 39, 46, and 68, all classical and US Gulf Coast El Tor strains have been categorized as genotype 1, the Australian El Tor strains as genotype 2, and the El Tor strains of the seventh pandemic and the Latin American epidemic as genotype 3. Genotyping of ctxB has indicated that the classical strains harbor a unique cholera toxin gene that is not in the El Tor strains except for the US Gulf Coast El Tor clone (4). The US Gulf Coast hybrid El Tor strains that harbor the classical cholera toxin have been associated with sporadic outbreaks in the United States (5) and, until recently, had not been reported anywhere else in the world. Then in 2004, hybrid El Tor strains that encode the classical cholera toxin were isolated from cholera patients in Matlab, Bangladesh (6), and in Beira, Mozambique (7). In 2006, Nair et al. reported that the current seventh pandemic prototype El Tor strains had been replaced by hybrid El Tor strains in Bangladesh (8). We now report how far the hybrid El Tor strains have spread in Asia and Africa. Description: This article can also be accessed through pubmed on doi: 10.3201/eid1406.080129

Investigation of Malaria Parasitemia among Asymptomatic Individuals in Designated Districts of Central and Muchinga Provinces of Zambia – A Cross Sectional Study

2024-01-01T00:00:00Z

Title: Investigation of Malaria Parasitemia among Asymptomatic Individuals in Designated Districts of Central and Muchinga Provinces of Zambia – A Cross Sectional Study Authors: Loti, Patrick; Nyirenda, Stanley. S.; Chisulo, Frank, K.; Chama, Agness; Singogo, Majory; Chileshe, Daniel, B.; Mwansa, James Abstract: Abstract. The aim of the study was to investigate asymptomatic malaria in health-conscious population across four selected districts. Malaria is a life-threatening disease caused by Plasmodium spp. transmitted through bites of infected female Anopheles mosquitoes. Asymptomatic malaria refers to the presence of malaria parasites in vivo without symptoms, which usually provides a reservoir for the disease transmission. Materials and methods. Blood collected in EDTA underwent testing through RDT (SD Bioline one-step malaria antigen P.f. (HRP-II) rapid test kits), while thin and thick blood smears Giemsa stained were microscopically examined. Results and discussion. Out of 385 individuals examined, 84 people (21.8 %) tested positive for malaria using RDT and 101/385 (26.2 %) – through microscopy. Microscopic examination further identified 27 individuals (7.0 %) with gametocytes and 74 (19.2 %) – with trophozoites. Intriguingly, 17 (4.4 %) samples showed negative results in RDT but exhibited trophozoites and gametocytes upon smear examination. District-wise analysis demonstrated the highest malaria positivity rate in Kanchibiya district, with 32 cases (8.3 %) detected by RDT and 35 (8.5 %) – through microscopy. Chitambo district followed closely: with RDT and microscopy values of 25 (6.5 %) and 33 (8.4 %), respectively; while Mpika and Serenje districts had 13 (3.4 %) and 14 (3.6 %) prevalence, respectively, with RDT and microscopy at 12 (3.1 %) in both districts [x2 =16.3, p-value=0.0118]. The study also revealed that 365/385 (95 %) of the participants demonstrated knowledge and positive attitudes toward malaria. Our findings accentuate the presence of asymptomatic malaria, encompassing trophozoites and gametocytes, among seemingly healthy individuals which poses a health risk to the community. Therefore, it is imperative to implement preventive chemotherapy and strengthen vector control efforts against malaria in order to reduce the infection rate. Description: This article is investigating malaria parasitemia and can also be accessed online using DOI: 10.21055/0370-1069-2024-2-188-192

Incidence of Severe and Non severe Pertussis Among HIV-Exposed and -Unexposed Zambian Infants Through 14 Weeks of Age: Results From the Southern Africa Mother Infant Pertussis Study (SAMIPS), a Longitudinal Birth Cohort Study

2016-01-01T00:00:00Z

Title: Incidence of Severe and Non severe Pertussis Among HIV-Exposed and -Unexposed Zambian Infants Through 14 Weeks of Age: Results From the Southern Africa Mother Infant Pertussis Study (SAMIPS), a Longitudinal Birth Cohort Study Authors: Gill, J. Christopher; Mwananyanda, Lawrence; Kwenda, Geoffrey; Magdalene, Mwale; Williams, L. Anna; Siazeele, Kazunga; Zhaoyan, Yang; Mwansa, James; Thea, M. Donald Abstract: Background. Maternal vaccination with tetanus, reduced-dose diphtheria, and acellular pertussis vaccine (Tdap) could be an effective way of mitigating the high residual burden of infant morbidity and mortality caused by Bordetella pertussis. To better inform such interventions, we conducted a burden-of-disease study to determine the incidence of severe and nonsevere pertussis among a population of Zambian infants. Methods. Mother–infant pairs were enrolled at 1 week of life, and then seen at 2- to 3-week intervals through 14 weeks of age. At each visit, nasopharyngeal (NP) swabs were obtained from both, and symptoms were catalogued. Using polymerase chain reaction (PCR) to identify cases, and a severity scoring system to triage these into severe/nonsevere, we calculated disease incidence using person-time at risk as the denominator. Results. From a population of 1981 infants, we identified 10 with clinical pertussis, for an overall incidence of 2.4 cases (95% confidence interval [CI], 1.2–4.2) per 1000 infant-months and a cumulative incidence of 5.2 cases (95% CI, 2.6–9.0) per 1000 infants. Nine of 10 cases occurred within a 3-month window (May–July 2015), with highest incidence between birth and 6 weeks of age (3.5 cases per 1000 infant-months), concentrated among infants prior to vaccination or among those who had only received 1 dose of Diphtheria Tetanus whole cell Pertussis (DTwP). Maternal human immunodeficiency virus (HIV) modestly increased the risk of infant pertussis (risk ratio, 1.8 [95% CI, .5–6.9]). Only 1 of 10 infant cases qualified as having severe pertussis. The rest presented with the mild and nonspecific symptoms of cough, coryza, and/or tachypnea. Notably, cough durations were long, exceeding 30 days in several cases, with PCRs repeatedly positive over time. Conclusions. Pertussis is circulating freely among this population of Zambian infants but rarely presents with the classical symptoms of paroxysmal cough, whooping, apnea, and cyanosis. Maternal HIV appears to increase the risk, while lack of effective exposure to DTwP increased the risk. Description: This article can also be accessed on DOI: 10.1093/cid/ciw526

Detection of Pneumococcal DNA in Blood by Polymerase Chain Reaction for Diagnosing Pneumococcal Pneumonia in Young Children From Low- and Middle-Income Countries

2017-06-15T00:00:00Z

Title: Detection of Pneumococcal DNA in Blood by Polymerase Chain Reaction for Diagnosing Pneumococcal Pneumonia in Young Children From Low- and Middle-Income Countries Authors: Morpeth, C. Susan; Knoll, Maria Deloria; Scott, G. Anthony J.; Park, E. Daniel; Watson, L. Nora; Bagget, C. Henry; Brooks, W. Abdullah; Feikin, R. Daniel; Hammitt, L. Laura; Howie, R. C. Stephen; Kotlof, L. Karen; Levine, S. Orin; Madhi, A. Shabir; O'Brien, L. Kathrine; Thea, M. Donald; Adrian, V. Peter; Ahmed, Dilruba; Antonio, Martin; Bunthi, Charatdao; Deluca, N. Andrea; Driscoll, J. Amanda; Githua, Louis Peter; Higdon, M. Melisa; Kahn, Geof; Karani, Angela; Karron, A. Ruth; Kwenda, Geoffrey; Makprasert, Sirrirat; Mazumder, Razib; Moore, P. David; Mwansa, James; Nyongesa, Sammy; Prosperi, Christine; Sow, O. Sambao; Tamboura, Boubou; Whistler, Toni; Zeger, L. Scott; Murdoch, R. David Abstract: We investigated the performance of polymerase chain reaction (PCR) on blood in the diagnosis of pneumococcal pneumonia among children from 7 low- and middle-income countries. Methods. We tested blood by PCR for the pneumococcal autolysin gene in children aged 1–59 months in the Pneumonia Etiology Research for Child Health (PERCH) study. Children had World Health Organization–defined severe or very severe pneumonia or were age-frequency–matched community controls. Additionally, we tested blood from general pediatric admissions in Kilifi, Kenya, a PERCH site. The proportion PCR-positive was compared among cases with microbiologically confirmed pneumococcal pneumonia (MCPP), cases without a confirmed bacterial infection (nonconfirmed), cases confirmed for nonpneumococcal bacteria, and controls. Results. In PERCH, 7.3% (n = 291/3995) of cases and 5.5% (n = 273/4987) of controls were blood pneumococcal PCR-positive (P <.001), compared with 64.3% (n = 36/56) of MCPP cases and 6.3% (n = 243/3832) of nonconfirmed cases (P < .001). Blood pneumococcal PCR positivity was higher in children from the 5 African countries (5.5%–11.5% among cases and 5.3%–10.2% among controls) than from the 2 Asian countries (1.3% and 1.0% among cases and 0.8% and 0.8% among controls). Among Kilifi general pediatric admissions, 3.9% (n = 274/6968) were PCR-positive, including 61.7% (n = 37/60) of those with positive blood cultures for pneumococcus. Discussion. The utility of pneumococcal PCR on blood for diagnosing childhood pneumococcal pneumonia in the 7 low- and middle-income countries studied is limited by poor specificity and by poor sensitivity among MCPP cases. Description: Can also be accessed https://doi.org/10.1093/cid/cix145