Publications by authors named "Amos Phiri"

20 Publications

  • Page 1 of 1

Pneumococcal carriage in households in Karonga District, Malawi, before and after introduction of 13-valent pneumococcal conjugate vaccination.

Vaccine 2018 11 21;36(48):7369-7376. Epub 2018 Oct 21.

Institute of Infection and Global Health, University of Liverpool, Liverpool, UK; Malawi-Liverpool-Wellcome Trust Clinical Research Programme, College of Medicine, University of Malawi, Blantyre, Malawi. Electronic address:

Background: Thirteen-valent pneumococcal conjugate vaccine (PCV13) was introduced in Malawi in November 2011 and is offered to infants at 6, 10 and 14 weeks of age as part of routine immunisation. PCV13 is expected to reduce vaccine type (VT) nasopharyngeal carriage, leading to reduced transmission and herd protection.

Methods: We compared pneumococcal carriage in rural Karonga District, Malawi, pre-vaccine in 2009-2011 and post-vaccine in 2014 using a combination of cross-sectional and longitudinal analyses. Nasopharyngeal swabs were collected from a cohort of mother-infant pairs and household members <16 years. Pneumococci from 2009 to 2011 were serogrouped using latex agglutination and serotyped by Quellung reaction. In 2014, latex agglutination was used for both steps. Carriage prevalence ratios using prevalence data from before and after vaccine introduction were calculated by log-binomial regression, adjusted for age, seasonality and household composition. Participating infants in 2014 received PCV13 as part of routine immunisation.

Results: VT carriage prior to PCV-13 introduction was 11.4%, 45.1%, 28.2%, 21.2% and 6.6% for 6-week old infants, 18-week old infants, children 1-4 years, children 5-15 years and mothers, respectively. After vaccine introduction, VT carriage decreased among vaccinated 18-week old infants (adjusted prevalence ratio 0.24 (95%CI 0.08-0.75)), vaccinated children 1-4 years (0.54 (0.33-0.88)), unvaccinated children 5-15 years (0.37 (0.17-0.78)) and mothers (0.34 (0.15-0.79)). No decrease in VT carriage was observed for 6-week old infants too young to be vaccinated (1.07 (0.38-3.02)) and PCV-13 ineligible children 1-4 years (0.84 (0.53-1.33)). Non-VT carriage increased only among vaccinated children 1-4 years (1.58 (1.21-2.06)).

Conclusions: There is evidence of reduced VT pneumococcal carriage three years after vaccine introduction in this rural Malawian population with good vaccine coverage using a 3 + 0 schedule. However carriage was sustained among 6-week-old infants and PCV13 ineligible 1-4 year olds, and there was some indication of serotype replacement in vaccinated 1-4 year olds.
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November 2018

Presentation of life-threatening invasive nontyphoidal Salmonella disease in Malawian children: A prospective observational study.

PLoS Negl Trop Dis 2017 12 7;11(12):e0006027. Epub 2017 Dec 7.

Malawi-Liverpool-Wellcome Trust Clinical Research Programme, College of Medicine, University of Malawi, Malawi.

Nontyphoidal Salmonellae commonly cause invasive disease in African children that is often fatal. The clinical diagnosis of these infections is hampered by the absence of a clear clinical syndrome. Drug resistance means that empirical antibiotic therapy is often ineffective and currently no vaccine is available. The study objective was to identify risk factors for mortality among children presenting to hospital with invasive Salmonella disease in Africa. We conducted a prospective study enrolling consecutive children with microbiologically-confirmed invasive Salmonella disease admitted to Queen Elizabeth Central Hospital, Blantyre, in 2006. Data on clinical presentation, co-morbidities and outcome were used to identify children at risk of inpatient mortality through logistic-regression modeling. Over one calendar year, 263 consecutive children presented with invasive Salmonella disease. Median age was 16 months (range 0-15 years) and 52/256 children (20%; 95%CI 15-25%) died. Nontyphoidal serovars caused 248/263 (94%) of cases. 211/259 (81%) of isolates were multi-drug resistant. 251/263 children presented with bacteremia, 6 with meningitis and 6 with both. Respiratory symptoms were present in 184/240 (77%; 95%CI 71-82%), 123/240 (51%; 95%CI 45-58%) had gastrointestinal symptoms and 101/240 (42%; 95%CI 36-49%) had an overlapping clinical syndrome. Presentation at <7 months (OR 10.0; 95%CI 2.8-35.1), dyspnea (OR 4.2; 95%CI 1.5-12.0) and HIV infection (OR 3.3; 95%CI 1.1-10.2) were independent risk factors for inpatient mortality. Invasive Salmonella disease in Malawi is characterized by high mortality and prevalence of multi-drug resistant isolates, along with non-specific presentation. Young infants, children with dyspnea and HIV-infected children bear a disproportionate burden of the Salmonella-associated mortality in Malawi. Strategies to improve prevention, diagnosis and management of invasive Salmonella disease should be targeted at these children.
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December 2017

Prevalence and risk factors for anemia severity and type in Malawian men and women: urban and rural differences.

Popul Health Metr 2017 03 29;15(1):12. Epub 2017 Mar 29.

London School of Hygiene and Tropical Medicine, London, United Kingdom.

Background: The global burden of anemia is large especially in sub-Saharan Africa, where HIV is common and lifestyles are changing rapidly with urbanization. The effects of these changes are unknown. Studies of anemia usually focus on pregnant women or children, among whom the burden is greatest. We describe prevalence and risk factors for anemia among rural and urban men and women of all ages in Malawi.

Methods: We analyzed data from a population-wide cross-sectional survey of adults conducted in two sites, Karonga (rural) and Lilongwe (urban), commencing in May 2013. We used multinomial logistic regression models, stratified by sex to identify risk factors for mild and moderate-to-severe anemia.

Results: Anemia prevalence was assessed among 8,926 men (age range 18-100 years) and 14,978 women (age range: 18-103 years). Weighted prevalence levels for all, mild, and moderate-to-severe anemia were 8.2, 6.7 and 1.2% in rural men; 19.4, 12.0 and 7.4% in rural women; 5.9, 5.1 and 0.8% in urban men; and 23.4, 13.6 and 10.1% in urban women. Among women, the odds of anemia were higher among urban residents and those with higher socioeconomic status. Increasing age was associated with higher anemia prevalence in men. Among both men and women, HIV infection was a consistent risk factor for severity of anemia, though its relative effect was stronger on moderate-to-severe anemia.

Conclusions: The drivers of anemia in this population are complex, include both socioeconomic and biological factors and are affecting men and women differently. The associations with urban lifestyle and HIV indicate opportunities for targeted intervention.
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March 2017

Hypertension and diabetes in Africa: design and implementation of a large population-based study of burden and risk factors in rural and urban Malawi.

Emerg Themes Epidemiol 2016 1;13. Epub 2016 Feb 1.

Karonga Prevention Study, Karonga, Malawi ; London School of Hygiene and Tropical Medicine, London, UK.

Background: The emerging burden of cardiovascular disease and diabetes in sub-Saharan Africa threatens the gains made in health by the major international effort to combat infectious diseases. There are few data on distribution of risk factors and outcomes in the region to inform an effective public health response. A comprehensive research programme is being developed aimed at accurately documenting the burden and drivers of NCDs in urban and rural Malawi; to design and test intervention strategies. The programme includes population surveys of all people aged 18 years and above, linking individuals with newly diagnosed hypertension and diabetes to healthcare and supporting clinical services. The successes, challenges and lessons learnt from the programme to date are discussed.

Results: Over 20,000 adults have been recruited in rural Karonga and urban Lilongwe. The urban population is significantly younger and wealthier than the rural population. Employed urban individuals, particularly males, give particular recruitment challenges; male participation rates were 80.3 % in the rural population and 43.6 % in urban, whilst female rates were 93.6 and 75.6 %, respectively. The study is generating high quality data on hypertension, diabetes, lipid abnormalities and risk factors.

Conclusions: It is feasible to develop large scale studies that can reliably inform the public health approach to diabetes, cardiovascular disease and other NCDs in Sub-Saharan Africa. It is essential for studies to capture both rural and urban populations to address disparities in risk factors, including age structure. Innovative approaches are needed to address the specific challenge of recruiting employed urban males.
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February 2016

Pneumococcal Acquisition Among Infants Exposed to HIV in Rural Malawi: A Longitudinal Household Study.

Am J Epidemiol 2016 Jan 1;183(1):70-8. Epub 2015 Dec 1.

The prevalence of Streptococcus pneumoniae (pneumococcus) carriage is higher in adults who are infected with human immunodeficiency virus (HIV) than in adults who are not. We hypothesized that infants exposed to HIV become carriers of nasopharyngeal pneumococcus earlier and more frequently than infants who are not exposed to HIV. We compared infant pneumococcal acquisition by maternal HIV status and household exposure in Karonga District, Malawi, in 2009-2011, before the introduction of pneumococcal conjugate vaccine. Nasopharyngeal swabs were collected every 4-6 weeks in the first year of life from infants with known HIV-exposure status, their mothers, and other household members. We studied infant pneumococcal acquisition by maternal HIV status, serotype-specific household exposure, and other risk factors, including seasonality. We recruited 54 infants who were exposed to HIV and 131 infants who were not. There was no significant difference in pneumococcal acquisition by maternal HIV status (adjusted rate ratio (aRR) = 1.00, 95% confidence interval (CI): 0.87, 1.15). Carriage by the mother was associated with greater acquisition of the same serotype (aRR = 3.09, 95% CI: 1.47, 6.50), but the adjusted population attributable fraction was negligible (1.9%, 95% CI: 0.0, 4.3). Serotype-specific exposure to children under 5 years of age was associated with higher acquisition (aRR = 4.30, 95% CI: 2.80, 6.60; adjusted population attributable fraction = 8.8%, 95% CI: 4.0, 13.4). We found no evidence to suggest that maternal HIV infection would affect the impact of pneumococcal vaccination on colonization in this population.
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January 2016

Persisting high prevalence of pneumococcal carriage among HIV-infected adults receiving antiretroviral therapy in Malawi: a cohort study.

AIDS 2015 Sep;29(14):1837-44

aDepartment of Clinical Infection, Microbiology, Institute of Infection and Global Health, University of Liverpool, UK bKaronga Prevention Study, Chilumba cThe Polytechnic, University of Malawi, Blantyre, Malawi dDepartment of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, London eDepartment of Epidemiology and Population Health, Institute of Infection and Global Health, University of Liverpool, UK.

Objective: HIV-infected adults have high rates of pneumococcal carriage and invasive disease. We investigated the effect of antiretroviral therapy (ART) on pneumococcal carriage in HIV-infected adults prior to infant pneumococcal conjugate vaccine (PCV) rollout.

Design: Observational cohort study.

Methods: We recruited HIV-infected adults newly attending a rural HIV clinic in northern Malawi between 2008 and 2010. Nasopharyngeal samples were taken at baseline and after 6, 12, 18 and 24 months. We compared pneumococcal carriage by ART status using generalized estimated equation models adjusted for CD4 cell count, sex, seasonality, and other potential confounders.

Results: In total, 336 individuals were included, of which 223 individuals started ART during follow-up. Individuals receiving ART had higher pneumococcal carriage than individuals not receiving ART (25.9 vs. 19.8%, P = 0.03) particularly for serotypes not included in PCV13 (16.1 vs. 9.6% P = 0.003). Following adjustment, increased carriage of non-PCV13 serotypes was still observed for individuals on ART, but results for all serotypes were nonsignificant [all serotypes: adjusted risk ratio (aRR) 1.22 (0.95-1.56); non-PCV13 serotypes: aRR 1.72, 95% CI 1.13-2.62].

Conclusion: Pneumococcal carriage in HIV-infected adults in Malawi remained high despite use of ART, consistent with failure of mucosal immune reconstitution in the upper respiratory tract. There was evidence of increased carriage of non-PCV13 serotypes. HIV-infected adults on ART could remain an important reservoir for pneumococcal diversity post infant pneumococcal vaccine introduction. Control of pneumococcal disease in African HIV remains a priority.
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September 2015

Human Immunodeficiency Virus, Antiretroviral Therapy and Markers of Lymphatic Filariasis Infection: A Cross-sectional Study in Rural Northern Malawi.

PLoS Negl Trop Dis 2015 4;9(6):e0003825. Epub 2015 Jun 4.

Karonga Prevention Study, Karonga District, Malawi; Institute of Infection and Global Health, University of Liverpool, Liverpool, United Kingdom.

Background: Lymphatic filariasis (LF) and human immunodeficiency virus (HIV) are major public health problems. Individuals may be co-infected, raising the possibility of important interactions between these two pathogens with consequences for LF elimination through annual mass drug administration (MDA).

Methodology And Principal Findings: We analysed circulating filarial antigenaemia (CFA) by HIV infection status among adults in two sites in northern Malawi, a region endemic for both LF and HIV. Stored blood samples and data from two geographically separate studies were used: one a recruitment phase of a clinical trial of anti-filarial agent dosing regimens, and the other a whole population annual HIV sero-survey. In study one, 1,851 consecutive adult volunteers were screened for HIV and LF infection. CFA prevalence was 25.4% (43/169) in HIV-positive and 23.6% (351/1487) in HIV-negative participants (p=0.57). Geometric mean CFA concentrations were 859 and 1660 antigen units per ml of blood (Ag/ml) respectively, geometric mean ratio (GMR) 0.85, 95%CI 0.49-1.50. In 7,863 adults in study two, CFA prevalence was 20.9% (86/411) in HIV-positive and 24.0% (1789/7452) in HIV-negative participants (p=0.15). Geometric mean CFA concentrations were 630 and 839 Ag/ml respectively (GMR 0.75, 95%CI 0.60-0.94). In the HIV-positive group, antiretroviral therapy (ART) use was associated with a lower CFA prevalence, 12.7% (18/142) vs. 25.3% (67/265), (OR 0.43, 95%CI 0.24-0.76). Prevalence of CFA decreased with duration of ART use, 15.2% 0-1 year (n=59), 13.6% >1-2 years (n=44), 10.0% >2-3 years (n=30) and 0% >3-4 years treatment (n=9), p<0.01 χ2 for linear trend.

Conclusions/significance: In this large cross-sectional study of two distinct LF-exposed populations, there is no evidence that HIV infection has an impact on LF epidemiology that will interfere with LF control measures. A significant association of ART use with lower CFA prevalence merits further investigation to understand this apparent beneficial impact of ART.
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March 2016

Randomised controlled clinical trial of increased dose and frequency of albendazole and ivermectin on Wuchereria bancrofti microfilarial clearance in northern Malawi.

Trans R Soc Trop Med Hyg 2015 Jun 15;109(6):393-9. Epub 2015 Apr 15.

Karonga Prevention Study, Chilumba, Karonga district, Malawi Institute of Infection and Global Health, University of Liverpool, Liverpool, UK.

Background: In Africa, albendazole and ivermectin are currently used in combination for annual mass drug administration (MDA) for lymphatic filariasis (LF) elimination. Rapid and sustained clearance is desirable for public health impact and elimination of LF. Increasing the dose and/or frequency of albendazole and ivermectin treatment may be more effective in clearing microfilariae than standard MDA.

Methods: We conducted a randomised controlled open label trial in northern Malawi comparing three modified treatment groups to standard dosage of ivermectin and albendazole in adults with confirmed circulating LF antigen and microfilaria. Participants were followed-up every 6 months for 2 years for repeat microfilarial counts and safety assessments.

Results: A total of 1851 adults were screened and 70 with microfilarial counts >80 microfilariae/ml were randomised. All treatment groups achieved a significant reduction of microfilariae levels by 12- and 24-months of follow-up. Doubling the standard dose and administering it twice yearly showed a non-significant tendency towards faster and more complete clearance. There were no serious adverse reactions.

Conclusions: In this small study, all regimens effectively cleared microfilaria. Standard treatment may be adequate in settings like Malawi but not in all endemic settings and larger studies are required to demonstrate benefit of higher dosages. [ identifier: NCT01213576].
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June 2015

Genomic characterisation of invasive non-typhoidal Salmonella enterica Subspecies enterica Serovar Bovismorbificans isolates from Malawi.

PLoS Negl Trop Dis 2013 Nov 14;7(11):e2557. Epub 2013 Nov 14.

Institute of Infection and Global Health, University of Liverpool, Liverpool, United Kingdom.

Background: Invasive Non-typhoidal Salmonella (iNTS) are an important cause of bacteraemia in children and HIV-infected adults in sub-Saharan Africa. Previous research has shown that iNTS strains exhibit a pattern of gene loss that resembles that of host adapted serovars such as Salmonella Typhi and Paratyphi A. Salmonella enterica serovar Bovismorbificans was a common serovar in Malawi between 1997 and 2004.

Methodology: We sequenced the genomes of 14 Malawian bacteraemia and four veterinary isolates from the UK, to identify genomic variations and signs of host adaptation in the Malawian strains.

Principal Findings: Whole genome phylogeny of invasive and veterinary S. Bovismorbificans isolates showed that the isolates are highly related, belonging to the most common international S. Bovismorbificans Sequence Type, ST142, in contrast to the findings for S. Typhimurium, where a distinct Sequence Type, ST313, is associated with invasive disease in sub-Saharan Africa. Although genome degradation through pseudogene formation was observed in ST142 isolates, there were no clear overlaps with the patterns of gene loss seen in iNTS ST313 isolates previously described from Malawi, and no clear distinction between S. Bovismorbificans isolates from Malawi and the UK. The only defining differences between S. Bovismorbificans bacteraemia and veterinary isolates were prophage-related regions and the carriage of a S. Bovismorbificans virulence plasmid (pVIRBov).

Conclusions: iNTS S. Bovismorbificans isolates, unlike iNTS S. Typhiumrium isolates, are only distinguished from those circulating elsewhere by differences in the mobile genome. It is likely that these strains have entered a susceptible population and are able to take advantage of this niche. There are tentative signs of convergent evolution to a more human adapted iNTS variant. Considering its importance in causing disease in this region, S. Bovismorbificans may be at the beginning of this process, providing a reference against which to compare changes that may become fixed in future lineages in sub-Saharan Africa.
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November 2013

Bacteraemia in Malawian neonates and young infants 2002-2007: a retrospective audit.

BMJ Open 2012 15;2(3). Epub 2012 May 15.

Department of General Medicine, The Royal Children's Hospital, Melbourne, Australia.

Objectives: To assess the causes of bacteraemia in young infants and susceptibility to first-line antibiotics (benzylpenicillin plus gentamicin) at the Queen Elizabeth Central Hospital (QECH), Malawi during 2002-2007.

Design: Retrospective analysis of demographic and microbiological data using laboratory records.

Setting: QECH is Malawi's largest hospital with 7000 neonates admitted annually, 9% for septicaemia.

Patients: All infants aged 60 days or less admitted to QECH that had a blood culture taken over the 6-year period.

Main Outcome Measures: 6754 blood cultures were taken. 3323 organisms were isolated: one-third were pathogens, two-thirds contaminants. Gram-positive organisms (53%) were more common than gram-negatives (47%). Four organisms made up half of all pathogens: Staphylococcus aureus (15.3%), group B streptococci (13.5%), non-typhoidal salmonellae (12.6%) and Escherichia coli (10.5%). Apart from non-typhoidal salmonellae and Streptococcus pneumoniae, most organisms were more common in the first week of life than later. Overall, 28% of isolates during 2002-2007 were resistant to first-line antibiotic, higher than observed during 1996-2001 (22%). Penicillin susceptibility fluctuated while gram-negative resistance to gentamicin increased from 17% to 27% over the study period.

Conclusions: In the QECH, pathogens causing young infant sepsis are an unusual mix of organisms seen in both developed and developing countries. Resistance to first-line antibiotics is higher than observed in most studies. Ongoing monitoring is needed and clinical outcome data would aid interpretation of findings. A high proportion of blood cultures were contaminated with skin flora-improved training and supervision of phlebotomists are needed to improve the utility of taking blood cultures.
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October 2012

The outcome of non-typhoidal salmonella meningitis in Malawian children, 1997-2006.

Ann Trop Paediatr 2009 Mar;29(1):13-22

Department of Paediatrics, College of Medicine, Blantyre, Malawi.

Introduction: The clinical course and outcome of non-typhoidal salmonella (NTS) meningitis in Malawian children over a 10-year period (1997-2006) is described.

Methods: Demographic, clinical and laboratory data were collected for all children over 2 months of age admitted with salmonella meningitis to Queen Elizabeth Central Hospital from 1997 to 2006. In the 1st year, salmonellae were susceptible to chloramphenicol, and children received 2 weeks of chloramphenicol treatment. When NTS resistance to chloramphenicol started to appear in 1998, treatment was changed to ceftriaxone. From 2002, the duration of antibiotic therapy was extended to 4-weeks which included 2 weeks of intravenous ceftriaxone and a further 2 weeks of oral ciprofloxacin.

Results: The in-hospital case fatality rate (CFR) was 52.3% (48.2% until 2002 and 53.9% after prolonged antibiotic therapy was introduced). Of the survivors, one in 12 (8.3%) became completely well (sequelae-free) in the period 1997-2001 while 18 of 31 survivors (58.1%) made a complete recovery during 2002-2006 (p<0.01). After the 4-week course of antimicrobial therapy was introduced, the number of relapses or recurrences fell from nine in 15 (60%) survivors treated with chloramphenicol or ceftriaxone to three in 35 (8.7%) survivors who received 4 weeks of antibiotics (p<0.0001).

Conclusion: In Malawi, salmonella meningitis has a CFR of approximately 50%, which has remained constant over many years. Residual morbidity, however, has decreased over 10 years, despite rising numbers of multi-drug-resistant cases of NTS. This improvement might be owing to better treatment and management and/or reduced pathogenicity of the multi-drug-resistant bacteria.
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March 2009

Epidemics of invasive Salmonella enterica serovar enteritidis and S. enterica Serovar typhimurium infection associated with multidrug resistance among adults and children in Malawi.

Clin Infect Dis 2008 Apr;46(7):963-9

Malawi-Liverpool-Wellcome Trust Clinical Research Programme, College of Medicine, University of Malawi, Blantyre, Malawi.

Background: Nontyphoidal salmonellae (NTS) have become the most common cause of bacteremia in tropical Africa, particularly among susceptible children and HIV-infected adults.

Methods: We describe 4956 episodes of NTS bacteremia (2439 episodes in adults and 2517 episodes in children) that occurred in Blantyre, Malawi, during the 7-year period 1998-2004.

Results: A total of 75% of the cases of NTS bacteremia were due to Salmonella enterica serovar Typhimurium, and 21% were due to S. enterica serovar Enteritidis. Epidemic increases in the incidence of NTS bacteremia were seen sequentially, occurring first among cases caused by S. Enteritidis and then among cases caused by S. Typhimurium. Increased incidence of bacteremia was temporally associated with the acquisition of multidrug resistance to ampicillin, cotrimoxazole, and chloramphenicol by each serovar and occurred while the incidence of infection due to other common bloodstream pathogens remained constant. These epidemics were observed among adults and children. A seasonal pattern was also seen, with increased incidence during and after the rainy season. The median age of the patients was 32 years among adults and 22 months among children. Acquisition of multidrug-resistant infection was not associated with an increased case-fatality rate among children (22%), and the case-fatality rate among adults showed a significant trend toward decreasing (from 29% to 20%).

Conclusions: These data have important implications for the treatment of severe febrile illness in adults and children in tropical Africa. Further understanding of the molecular basis of these epidemics of multidrug-resistant NTS infection, including ongoing whole-genome sequencing of multidrug-resistant isolates, will yield important tools for the study of NTS pathogenesis, transmission, epidemiology, and prevention.
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April 2008

Invasive group B streptococcal infection in infants, Malawi.

Emerg Infect Dis 2007 Feb;13(2):223-9

Malawi-Liverpool-Wellcome Trust Programme of Clinical Tropical Research, Blantyre, Malawi.

Group B streptococci (GBS) are a recently identified cause of neonatal sepsis in Malawi. In Queen Elizabeth Central Hospital, Blantyre, Malawi, during May 2004-June 2005, GBS were isolated from routine blood and cerebrospinal fluid cultures from 57 infants. The incidence of early (EOD) and late onset (LOD) invasive GBS disease was 0.92 and 0.89 cases per 1,000 live births, respectively. Sepsis (52%) was the most common manifestation of EOD; meningitis (43%) and sepsis (36%) were the principal manifestations of LOD. The case-fatality rate was 33% overall (38% EOD, 29% LOD). Serotypes Ia and III were responsible for 77% of disease. All isolates were susceptible to penicillin, but 21% were resistant to erythromycin. The rate and manifestations of neonatal GBS disease in Malawi are similar to those in industrialized countries, but the case-fatality rate is higher than in industrialized countries. Effective locally relevant prevention strategies are needed.
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February 2007

Bacteremia in Malawian children with severe malaria: prevalence, etiology, HIV coinfection, and outcome.

J Infect Dis 2007 Mar 2;195(6):895-904. Epub 2007 Feb 2.

Blantyre Malaria Project, Blantyre, Malawi.

Background: Previous prospective studies of bacteremia in African children with severe malaria have mainly included children with cerebral malaria, and no study has examined the impact of human immunodeficiency virus (HIV) infection. We examined the prevalence and etiology of bacteremia and the impact of HIV infection on bacteremia in Malawian children with severe malaria, as well as the impact of bacteremia and HIV infection on outcome.

Methods: From 1996 until 2005, blood for culture was obtained on admission from all children admitted with severe malaria during the rainy season to the Paediatric Research Ward at the Queen Elizabeth Central Hospital in Blantyre, Malawi. HIV testing was performed prospectively from 2001 to 2005 and retrospectively for those admitted from 1996 to 2000. Multivariate regression analysis examined independent risk factors for bacteremia and death.

Results: Sixty-four (4.6%) of 1388 children with severe malaria had bacteremia; nontyphoidal Salmonellae (NTS) accounted for 58% of all bacteremias. The prevalence of any bacteremia and of NTS bacteremia was highest in children with severe malarial anemia (11.7% and 7.6%), compared with the prevalence in children with cerebral malaria and severe anemia (4.7% and 3.8%) and in those with cerebral malaria alone (3.0% and 0.9%). HIV infection status was determined in 1119 patients. HIV prevalence was 16% (and was highest in those with severe malaria anemia, at 20.4%), but HIV infection was not significantly associated with bacteremia. Neither bacteremia nor HIV infection was associated with death.

Conclusions: Antibiotics are not routinely indicated for children with severe malaria in this region, in which HIV is endemic. However, antibiotic therapy should be used to treat NTS infection if bacteremia is suspected in children with severe malarial anemia.
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March 2007

The impact of routine infant immunization with Haemophilus influenzae type b conjugate vaccine in Malawi, a country with high human immunodeficiency virus prevalence.

Vaccine 2006 Sep 9;24(37-39):6232-9. Epub 2006 Jun 9.

Mzuzu Central Hospital, Mzuzu, Malawi.

Malawi has extreme poverty and a high-human immunodeficiency virus (HIV) prevalence. Following Haemophilus influenzae type b (Hib) conjugate vaccine introduction during 2002, we evaluated vaccine impact by reviewing hospital surveillance data for acute bacterial meningitis in Blantyre district among children age 1-59 months admitted during 1997-2005. Documented annual Hib meningitis incidence rates decreased from 20-40/100,000 to near zero among both rural and urban residents despite no change in pneumococcal meningitis incidence rates. Before vaccine introduction, an average of 10 children/year had Hib meningitis and HIV infection compared to 2/year during 2003-2004 and none during 2005. Vaccine effectiveness was high following two or more doses of vaccine. The most urgent future need is for a sustainable routine infant immunization program, including a less expensive vaccine that preferably is delivered in a multivalent form.
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September 2006

Identification and characterization of ceftriaxone resistance and extended-spectrum beta-lactamases in Malawian bacteraemic Enterobacteriaceae.

J Antimicrob Chemother 2006 Apr;57(4):661-5

Malawi-Liverpool-Wellcome Trust Laboratories, Blantyre, Malawi.

Objectives: To enumerate and characterize extended-spectrum beta-lactamases (ESBLs) amongst ceftriaxone-resistant coliforms in Blantyre, Malawi, where third-generation cephalosporin use is currently highly restricted.

Methods: Over the period April 2004-March 2005 all ceftriaxone-resistant isolates from blood cultures were examined for the presence of ESBLs. Isoelectric focusing was performed on enzyme extracts. PCR and DNA sequencing of amplicons were used to identify the underlying genetic determinants responsible for the ESBL phenotypes. Transferability of the ESBL phenotypes was tested by conjugation to a susceptible Escherichia coli J53.

Results: Enterobacteriaceae were isolated from 1191 blood cultures, of which 19 (1.6%) were ceftriaxone resistant. Ten isolates (0.7% of all isolates) demonstrated an ESBL phenotype but only eight were characterized as three isolates were from the same patient. Genotypes SHV-11 (n = 1), SHV-12 (n = 3), SHV-27 (n = 1), TEM-63 (n = 2) and CTX-M-15 (n = 1) were detected. Plasmid transfer of the ESBL resistance phenotype was successful for all the isolates.

Conclusions: In a clinical setting of minimal cephalosporin usage there is already a diversity of ESBL genotypes. Increased use of cephalosporins in this setting is likely to result in a rapid expansion of ESBLs and their prevalence will need to be carefully monitored.
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April 2006

HIV infected adults do not have an excess of colonising bacteria in their large airways.

BMC Infect Dis 2003 Dec 12;3:29. Epub 2003 Dec 12.

Malawi-Liverpool-Wellcome Trust Research Programme, Universities of Malawi and Liverpool, PO Box 30096, Blantyre, Malawi.

Background: HIV infected adults have increased susceptibility to bacterial pneumonia but the underlying immune defect is poorly understood. We tested the hypothesis that HIV infection might be associated with increased bacterial colonisation of distal airways by nasal flora, which would then predispose patients to bacterial pneumonia.

Methods: Healthy volunteer adults with normal chest radiographs were recruited. Bronchoscopy was carried out and uncontaminated mucosal samples were collected from proximal and distal sites in the large airways using a protected specimen brush. Samples were cultured to detect typical respiratory tract colonising organisms, and the proportion of samples found to contain colonising bacteria compared between HIV infected and uninfected subjects using non-parametric tests.

Results: Forty-nine subjects were studied of whom 27 were HIV infected. Colonising bacteria were identified in the nasopharynx of all subjects including Streptococcus pneumoniae in 6/49 subjects (5 HIV uninfected). Colonising bacteria were found in the distal airway of 6 subjects (3/27 HIV infected vs 3/22 HIV uninfected; chi2 = 0.07, p = 0.8). Streptococcus pneumoniae was identified in the trachea of all subjects with nasal colonisation but in the distal airway of only 1 subject.

Conclusions: There was no evidence to support a hypothesis of increased airway bacterial colonisation in healthy HIV infected subjects.
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December 2003

Nontyphoidal salmonellae in United Kingdom badgers: prevalence and spatial distribution.

Appl Environ Microbiol 2003 Jul;69(7):4312-5

Department of Medical Microbiology and Genito-Urinary Medicine, University of Liverpool, Duncan Building, Daulby Street, Liverpool L69 3GA, United Kingdom.

Eighteen (72%) of 25 badger social groups were found to excrete Salmonella enterica serovar Ried, S. enterica serovar Binza, S. enterica serovar Agama, or S. enterica serovar Lomita. Each serovar was susceptible to a panel of antimicrobials. Based on results of pulsed-field gel electrophoresis, the S. enterica serovar Agama and S. enterica serovar Binza isolates were very similar, but two clones each of S. enterica serovar Lomita and S. enterica serovar Ried were found. Badgers excreting S. enterica serovar Agama were spatially clustered.
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July 2003

Non-typhoidal salmonella (NTS) bacteraemia in Malawian adults: a severe, recrudescent, HIV-associated illness.

Malawi Med J 2003 Jun;15(2):47-51

Malawi-Liverpool-Wellcome Trust Clinical Research Programme, College of Medicine, Blantyre, Malawi; Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK.

Non-typhoidal salmonella (NTS) bacteraemia is a common, recurrent illness in HIV-infected African adults. We aimed to describe the presentation and outcome of NTS bacteraemia, the pattern of recurrence, and to determine whether recurrence results from re-infection or recrudescence. 100 consecutive adult inpatients with NTS bacteraemia in Blantyre, Malawi were treated with chloramphenicol (500mg qid for 14 days). Survivors were prospectively followed to detect bacteraemic recurrence. Index and recurrent isolates were typed by antibiogram, pulsed field gel electrophoresis and plasmid analysis to distinguish recrudescence from re-infection. Inpatient mortality was 47%, and 1-year mortality was 77%. 77/78 cases were HIV positive. Anaemia was associated with inpatient death, and several features of AIDS were associated with poor outpatient survival. Among survivors, 43% (19/44) had a first recurrence of NTS bacteraemia at 23-186 days. Among these, 26% (5/19) developed multiple recurrences up to 245 days. No recurrence was seen after 245 days, despite follow-up for up to 609 days (median 214). Suppurative infections were not found at presentation, and were only seen twice at recurrence. Index and recurrent paired isolates were identical by phenotyping and genotyping, consistent with recrudescence, rather than re-infection. NTS bacteraemia has a high mortality (47%) and recurrence rate (43%) in HIV-infected African adults. Recurrence is caused by recrudescence rather than re-infection. Since focal infections were rarely found, recrudescence may often be a consequence of intracellular tissue sequestration. There is an urgent need for improved primary treatment and secondary prophylaxis in Africa.
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June 2003