C. Anthony Hart

Dual Infection of Infants by Human Metapneumovirus and Human Respiratory Syncytial Virus Is Strongly Associated with Severe Bronchiolitis

Abstract The association between severe bronchiolitis and dual infection by human metapneumovirus (hMPV) and human respiratory syncytial virus (hRSV) was investigated in !2-year-old infants with bronchiolitis who were admitted to the hospital during the 2001–2002 winter season. hMPV in nasopharyngeal aspirate and/or cells and fluid collected by nonbronchoscopic bronchoalveolar lavage was detected by reverse transcriptase-polymerase chain reaction (RT-PCR). hRSV was detected in nasopharyngeal aspirate and/or cells and fluid collected by nonbronchoscopic bronchoalveolar lavage by enzyme immunoassay, tissue culture, and RT-PCR. Dual infection with hMPV and hRSV confers a 10-fold increase in relative risk (RR) of admission to a pediatric intensive-care unit for mechanical ventilation (RR, 10.99 [95% confidence interval, 5.0–24.12]; P < .001, by Fisher exact test). Dual infection by hMPV and hRSV is associated with severe bronchiolitis.

Tracing the Source of Campylobacteriosis

Campylobacter jejuni is the leading cause of bacterial gastro-enteritis in the developed world. It is thought to infect 2–3 million people a year in the US alone, at a cost to the economy in excess of US

Prevalence and transmission of Kaposi's sarcoma‐associated herpesvirus (human herpesvirus 8) in Ugandan children and adolescents

4 billion. C. jejuni is a widespread zoonotic pathogen that is carried by animals farmed for meat and poultry. A connection with contaminated food is recognized, but C. jejuni is also commonly found in wild animals and water sources. Phylogenetic studies have suggested that genotypes pathogenic to humans bear greatest resemblance to non-livestock isolates. Moreover, seasonal variation in campylobacteriosis bears the hallmarks of water-borne disease, and certain outbreaks have been attributed to contamination of drinking water. As a result, the relative importance of these reservoirs to human disease is controversial. We use multilocus sequence typing to genotype 1,231 cases of C. jejuni isolated from patients in Lancashire, England. By modeling the DNA sequence evolution and zoonotic transmission of C. jejuni between host species and the environment, we assign human cases probabilistically to source populations. Our novel population genetics approach reveals that the vast majority (97%) of sporadic disease can be attributed to animals farmed for meat and poultry. Chicken and cattle are the principal sources of C. jejuni pathogenic to humans, whereas wild animal and environmental sources are responsible for just 3% of disease. Our results imply that the primary transmission route is through the food chain, and suggest that incidence could be dramatically reduced by enhanced on-farm biosecurity or preventing food-borne transmission.

Epidemics of Invasive Salmonella enterica Serovar Enteritidis and S. enterica Serovar Typhimurium Infection Associated with Multidrug Resistance among Adults and Children in Malawi

We studied the seroprevalence and transmission of Kaposis sarcoma‐associated herpesvirus (KSHV/HHV8), among 215 Ugandan children, adolescents and young adults. We measured antibodies to a latent nuclear antigen (LANA) and a lytic cycle protein encoded by open reading frame (orf) 65. Infection with KSHV/HHV8 occurred during early childhood and reached adult levels (approx. 50%) before the age of puberty. In children younger than 12 years of age, antibodies to LANA and the orf65 protein were independently associated with hepatitis B infection (p < 0.005). KSHV/HHV8 infection was not associated with antibodies to hepatitis A virus and hepatitis C virus, nor with the quality of the water supply, household size, previous blood transfusions, number of boy/girl friends or marital status. Antibodies to the orf65 protein, but not LANA, were weakly associated with a history of i.v. injections. Our results show that, in contrast to its sexual mode of transmission among homo/bisexual men and sexually transmitted diseases clinic attendees of Northern Europe and the US, transmission of KSHV in Uganda occurs largely before puberty. Among Ugandan children, KSHV transmission follows a horizontal pattern similar to other herpesviruses, in particular the related γ herpesvirus, Epstein‐Barr virus. Transmission of KSHV may be facilitated by living conditions that also promote infection with hepatitis B virus. Int. J. Cancer 77:817–820, 1998.© 1998 Wiley‐Liss, Inc.

The Genome of Burkholderia cenocepacia J2315, an Epidemic Pathogen of Cystic Fibrosis Patients

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.

Non-typhoidal salmonella bacteraemia among HIV-infected Malawian adults: high mortality and frequent recrudescence

Bacterial infections of the lungs of cystic fibrosis (CF) patients cause major complications in the treatment of this common genetic disease. Burkholderia cenocepacia infection is particularly problematic since this organism has high levels of antibiotic resistance, making it difficult to eradicate; the resulting chronic infections are associated with severe declines in lung function and increased mortality rates. B. cenocepacia strain J2315 was isolated from a CF patient and is a member of the epidemic ET12 lineage that originated in Canada or the United Kingdom and spread to Europe. The 8.06-Mb genome of this highly transmissible pathogen comprises three circular chromosomes and a plasmid and encodes a broad array of functions typical of this metabolically versatile genus, as well as numerous virulence and drug resistance functions. Although B. cenocepacia strains can be isolated from soil and can be pathogenic to both plants and man, J2315 is representative of a lineage of B. cenocepacia rarely isolated from the environment and which spreads between CF patients. Comparative analysis revealed that ca. 21% of the genome is unique in comparison to other strains of B. cenocepacia, highlighting the genomic plasticity of this species. Pseudogenes in virulence determinants suggest that the pathogenic response of J2315 may have been recently selected to promote persistence in the CF lung. The J2315 genome contains evidence that its unique and highly adapted genetic content has played a significant role in its success as an epidemic CF pathogen.

Rotavirus G and P types in children with acute diarrhea in Blantyre, Malawi, from 1997 to 1998: predominance of novel P[6]G8 strains.

ObjectiveNon-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. DesignOne hundred consecutive adult inpatients with NTS bacteraemia in Blantyre, Malawi, were treated with chloramphenicol. Survivors were prospectively followed to detect bacteraemic recurrence. MethodsIndex and recurrent isolates were typed by antibiogram, pulsed-field gel electrophoresis and plasmid analysis to distinguish recrudescence from re-infection. ResultsInpatient mortality was 47%, and 1-year mortality was 77%. A total of 77 out of 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. ConclusionNTS bacteraemia has a high mortality (47%) and recurrence (43%) rate in HIV-infected African adults. Recurrence is caused by recrudescence rather than re-infection. As 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.

Methicillin-resistant staphylococci in companion animals

One hundred rotavirus strains detected in children with acute diarrhea in Blantyre, Malawi, between July 1997 and January 1998 were characterized for G (VP7) and P (VP4) types by using multiplex, heminested, reverse transcription–polymerase chain reaction. A novel P[6]G8 rotavirus strain was identified in 42% of the specimens. The remaining strains comprised P[8]G3 (20%), P[6]G3 (10%), P[4]G8 (9%), P[6]G9 (3%), P[8]G4 (2%), P[6]G4 (2%), and P[4]G3 (1%). Rotavirus strains with mixed G or P types were identified in 2% of the specimens. Nine percent of the strains were nontypeable with the primers used. The P[6] genotype was identified in 57% of strains overall. This first description of serotype G8 rotavirus as a predominant strain has important implications for vaccine development in Africa. The finding of novel P/G combinations (P[6]G8 and P[4]G8) highlights the extraordinary diversity of rotaviruses in some countries. J. Med. Virol. 57:308–312, 1999.

The neglected role of antibody in protection against bacteremia caused by nontyphoidal strains of Salmonella in African children

We determined the molecular characteristics of methicillin-resistant staphylococci from animals and staff at a small animal and equine hospital. Methicillin-resistant Staphylococcus aureus (MRSA) identical to human EMRSA-15 was found in dogs and hospital staff. In contrast, 5 distinct MRSA strains were isolated from horses but not from hospital staff.

Clinical presentation and outcome of Pneumocystis carinii pneumonia in Malawian children

Nontyphoidal strains of Salmonella (NTS) are a common cause of bacteremia among African children. Cell-mediated immune responses control intracellular infection, but they do not protect against extracellular growth of NTS in the blood. We investigated whether antibody protects against NTS bacteremia in Malawian children, because we found this condition mainly occurs before 2 years of age, with relative sparing of infants younger than 4 months old. Sera from all healthy Malawian children tested aged more than 16 months contained anti-Salmonella antibody and successfully killed NTS. Killing was mediated by complement membrane attack complex and not augmented in the presence of blood leukocytes. Sera from most healthy children less than 16 months old lacked NTS-specific antibody, and sera lacking antibody did not kill NTS despite normal complement function. Addition of Salmonella-specific antibody, but not mannose-binding lectin, enabled NTS killing. All NTS strains tested had long-chain lipopolysaccharide and the rck gene, features that resist direct complement-mediated killing. Disruption of lipopolysaccharide biosynthesis enabled killing of NTS by serum lacking Salmonella-specific antibody. We conclude that Salmonella-specific antibody that overcomes the complement resistance of NTS develops by 2 years of life in Malawian children. This finding and the age-incidence of NTS bacteremia suggest that antibody protects against NTS bacteremia and support the development of vaccines against NTS that induce protective antibody.