Hector Verastegui

Age-Related Susceptibility to Infection with Diarrheagenic Escherichia coli among Infants from Periurban Areas in Lima, Peru

BACKGROUND Diarrheagenic Escherichia coli strains are being recognized as important pediatric enteropathogens worldwide. However, it is unclear whether there are differences in age-related susceptibility to specific strains, especially among infants. METHODS We conducted a passive surveillance cohort study of diarrhea that involved 1034 children aged 2-12 months in Lima, Peru. Control stool samples were collected from randomly selected children without diarrhea. All samples were analyzed for common enteric pathogens and for diarrheagenic E. coli with use of multiplex real-time polymerase chain reaction. RESULTS The most frequently isolated pathogens in 1065 diarrheal episodes were diarrheagenic E. coli strains (31%), including enteroaggregative (15.1%) and enteropathogenic E. coli (7.6%). Diarrheagenic E. coli, Campylobacter species, and rotavirus were more frequently isolated from infants aged >or=6 months. Among older infants, diffusely adherent E. coli and enterotoxigenic E. coli were more frequently isolated from diarrheal samples than from control samples (P <.05). Children aged >or=6 months who were infected with enterotoxigenic E. coli had a 4.56-fold increased risk of diarrhea (95% confidence interval, 1.20-17.28), compared with younger children. Persistent diarrhea was more common in infants aged <6 months (13.5% vs 3.6%; P <.001). Among children with diarrheagenic E. coli-positive samples, coinfections with other pathogens were more common in children with diarrhea than in control children (40.1% vs 15.6%; P <.001). CONCLUSIONS Diarrheagenic E. coli strains were more frequently isolated in samples from older infants. In this setting with high frequency of pathogen exposure and high frequency of breastfeeding, we hypothesize that the major age-related differences result from decreased exposure to milk-related protective factors and from increased exposure to contaminated food and water.

Density interactions among Streptococcus pneumoniae, Haemophilus influenzae and Staphylococcus aureus in the nasopharynx of young Peruvian children.

Streptococcus pneumoniae, Haemophilus influenzae and Staphylococcus aureus are commonly carried in the nasopharynx of young children, and have been speculated to interact with each other. Although earlier studies used cultures alone to assess these interactions, the addition of real-time quantitative polymerase chain reaction (qPCR) provides further insight into these interactions. We compared results of culture and qPCR for the detection of these 3 bacteria in 446 nasopharynx samples collected from 360 healthy young children in a prospective cohort study in the Peruvian Andes. Patterns of concurrent bacterial colonization were studied using repeated measures logistic regression models with generalized estimating equations. Spearman correlation coefficients were used to assess correlations among bacterial densities. At a bacterial density <105 colony forming units/mL measured by qPCR, culture detected significantly less carriers (P < 0.0001) for all 3 pathogens, than at a bacterial density >105 colony forming units/mL. In addition, there was a positive association between S. pneumoniae and H. influenzae colonization measured by both culture (odds ratio [OR] 3.11–3.17, P < 0.001) and qPCR (OR 1.95–1.97, P < 0.01). The densities of S. pneumoniae and H. influenzae, measured by qPCR, were positively correlated (correlation coefficient 0.32, P < 0.001). A negative association was found between the presence of S. pneumoniae and Staphylococcus aureus in carriage with both culture (OR 0.45, P = 0.024) and qPCR (OR 0.61, P < 0.05). The impact of density on detection by culture and the observed density-related interactions support use of qPCR in additional studies to examine vaccine effects on diverse bacterial species.

The role of influenza and parainfluenza infections in nasopharyngeal pneumococcal acquisition among young children

In a prospective cohort of young children, we evaluated whether viral infections increased the risk of pneumococcal acquisition. Acute respiratory infections due to influenza or parainfluenza viruses, but not to other viruses, facilitated the nasopharyngeal acquisition of new pneumococcal serotypes.

A community randomised controlled trial evaluating a home-based environmental intervention package of improved stoves, solar water disinfection and kitchen sinks in rural Peru: Rationale, trial design and baseline findings

INTRODUCTION Pneumonia and diarrhoea are leading causes of death in children. There is a need to develop effective interventions. OBJECTIVE We present the design and baseline findings of a community-randomised controlled trial in rural Peru to evaluate the health impact of an Integrated Home-based Intervention Package in children aged 6 to 35 months. METHODS We randomised 51 communities. The intervention was developed through a community-participatory approach prior to the trial. They comprised the construction of improved stoves and kitchen sinks, the promotion of hand washing, and solar drinking water disinfection (SODIS). To reduce the potential impact of non-blinding bias, a psychomotor stimulation intervention was implemented in the control arm. The baseline survey included anthropometric and socio-economic characteristics. In a sub-sample we determined the level of faecal contamination of drinking water, hands and kitchen utensils and the prevalence of diarrhoegenic Escherichia coli in stool specimen. RESULTS We enrolled 534 children. At baseline all households used open fires and 77% had access to piped water supplies. E. coli was found in drinking water in 68% and 64% of the intervention and control households. Diarrhoegenic E. coli strains were isolated from 45/139 stool samples. The proportion of stunted children was 54%. CONCLUSIONS Randomization resulted in comparable study arms. Recently, several critical reviews raised major concerns on the reliability of open health intervention trials, because of uncertain sustainability and non-blinding bias. In this regard, the presented trial featuring objective outcome measures, a simultaneous intervention in the control communities and a 12-month follow up period will provide valuable evidence.

A household-based study of acute viral respiratory illnesses in Andean children

Background: Few community studies have measured the incidence, severity and etiology of acute respiratory illness (ARI) among children living at high-altitude in remote rural settings. Methods: We conducted active, household-based ARI surveillance among children aged <3 years in rural highland communities of San Marcos, Cajamarca, Peru from May 2009 through September 2011 (RESPIRA-PERU study). ARI (defined by fever or cough) were considered lower respiratory tract infections if tachypnea, wheezing, grunting, stridor or retractions were present. Nasal swabs collected during ARI episodes were tested for respiratory viruses by real-time, reverse-transcriptase polymerase chain reaction. ARI incidence was calculated using Poisson regression. Results: During 755.1 child-years of observation among 892 children in 58 communities, 4475 ARI were observed, yielding an adjusted incidence of 6.2 ARI/child-year (95% confidence interval: 5.9–6.5). Families sought medical care for 24% of ARI, 4% were classified as lower respiratory tract infections and 1% led to hospitalization. Of 5 deaths among cohort children, 2 were attributed to ARI. One or more respiratory viruses were detected in 67% of 3957 samples collected. Virus-specific incidence rates per 100 child-years were: rhinovirus, 236; adenovirus, 73; parainfluenza virus, 46; influenza, 37; respiratory syncytial virus, 30 and human metapneumovirus, 17. Respiratory syncytial virus, metapneumovirus and parainfluenza virus 1–3 comprised a disproportionate share of lower respiratory tract infections compared with other etiologies. Conclusions: In this high-altitude rural setting with low-population density, ARI in young children were common, frequently severe and associated with a number of different respiratory viruses. Effective strategies for prevention and control of these infections are needed.

Cohort Profile: The Study of Respiratory Pathogens in Andean Children

We investigated respiratory pathogens in a prospective cohort study of young children living in the Peruvian Andes. In the study we assessed viral respiratory infections among young children, and explored interactions of viruses with common respiratory bacteria, especially Streptococcus pneumoniae. Through weekly household visits, data were collected on the signs and symptoms of acute respiratory illness (ARI), nasal samples were collected to test for viruses during episodes of ARI, and nasopharyngeal samples were collected on a monthly basis to monitor bacterial colonisation. We also collected data on vaccination coverage, patterns of social mixing, geographic information, and environmental and socio-demographic variables. Understanding the interaction of respiratory viruses with bacteria and its impact on the burden and severity of ARIs in rural areas of developing countries is critical to designing strategies for preventing such infections.

Incidence and risk factors for respiratory syncytial virus and human metapneumovirus infections among children in the remote highlands of Peru

Introduction The disease burden and risk factors for respiratory syncytial virus (RSV) and human metapneumovirus (MPV) infections among children living in remote, rural areas remain unclear. Materials and Methods We conducted a prospective, household-based cohort study of children aged <3 years living in remote rural highland communities in San Marcos, Cajamarca, Peru. Acute respiratory illnesses (ARI), including lower respiratory tract infection (LRTI), were monitored through weekly household visits from March 2009 through September 2011. Nasal swabs collected during ARI/LRTI were tested for RSV, MPV, and other respiratory viruses using real-time RT-PCR. Incidence rates and rate ratios were calculated using mixed effects Poisson regression. Results Among 892 enrolled children, incidence rates of RSV and MPV ARI were 30 and 17 episodes per 100 child-years, respectively. The proportions of RSV and MPV ARI that presented as LRTI were 12.5% and 8.9%, respectively. Clinic visits for ARI and hospitalizations were significantly more frequent (all p values <0.05) among children with RSV (clinic 41% and hospital 5.3%) and MPV ARI (38% and 3.5%) when compared with other viral infections (23% and 0.7%) and infections without virus detected (24% and 0.6%). In multivariable analysis, risk factors for RSV detection included younger age (RR 1.02, 95% CI: 1.00-1.03), the presence of a smoker in the house (RR 1.63, 95% CI: 1.12-2.38), residing at higher altitudes (RR 1.93, 95% CI: 1.25-3.00 for 2nd compared to 1st quartile residents; RR 1.98, 95% CI: 1.26-3.13 for 3rd compared to 1st quartile residents). Having an unemployed household head was significantly associated with MPV risk (RR 2.11, 95% CI: 1.12-4.01). Conclusion In rural high altitude communities in Peru, childhood ARI due to RSV or MPV were common and associated with higher morbidity than ARI due to other viruses or with no viral detections. The risk factors identified in this study may be considered for interventional studies to control infections by these viruses among young children from developing countries.

Impact of home environment interventions on the risk of influenza-associated ARI in Andean children: observations from a prospective household-based cohort study.

Background The Respiratory Infections in Andean Peruvian Children (RESPIRA-PERU) study enrolled children who participated in a community-cluster randomized trial of improved stoves, solar water disinfection, and kitchen sinks (IHIP trial) and children from additional Andean households. We quantified the burden of influenza-associated acute respiratory illness (ARI) in this household-based cohort. Methods From May 2009 to September 2011, we conducted active weekly ARI surveillance in 892 children age <3 years, of whom 272 (30.5%) had participated in the IHIP trial. We collected nasal swabs during ARI, tested for influenza and other respiratory viruses by RT-PCR, and determined influenza incidence and risk factors using mixed-effects regression models. Results The overall incidence of influenza-associated ARI was 36.6/100 child-years; incidence of influenza A, B, and C was 20.5, 8.7, and 5.2/100 child-years, respectively. Influenza C was associated with fewer days of subjective fever (median 1 vs. 2) and malaise (median 0 vs. 2) compared to influenza A. Non-influenza ARI also resulted in fewer days of fever and malaise, and fewer healthcare visits than influenza A-associated ARI. Influenza incidence varied by calendar year (80% occurred in the 2010 season) and IHIP trial participation. Among households that participated in the IHIP trial, influenza-associated ARI incidence was significantly lower in intervention than in control households (RR 0.40, 95% CI: 0.20–0.82). Conclusions Influenza burden is high among Andean children. ARI associated with influenza A and B had longer symptom duration and higher healthcare utilization than influenza C-associated ARI or non-influenza ARI. Environmental community interventions may reduce influenza morbidity.

Bacterial Density, Serotype Distribution and Antibiotic Resistance of Pneumococcal Strains from the Nasopharynx of Peruvian Children Before and After Pneumococcal Conjugate Vaccine 7.

Background: Pneumococcal conjugate vaccines (PCV) have decreased nasopharyngeal carriage of vaccine types but little data exist from rural areas. We investigated bacterial density, serotype distribution and antibiotic resistance of pneumococcal strains within the nasopharynx of young children in the Peruvian Andes, 2 years after PCV7 was introduced. Methods: Pneumococcal strains were isolated from a subset of 125 children from our Peruvian cohort, who entered the study in 2009 and had pneumococcus detected in the nasopharynx in both 2009 and during follow-up in 2011. Strains were Quellung serotyped and tested for susceptibility to antibiotics. Bacterial density was determined by quantitative polymerase chain reaction. Results: The prevalence of PCV7 strains decreased from 48% in 2009 to 28.8% in 2011, whereas non-PCV7 types increased from 52% to 71.2% (P = 0.002). There was a 3.5-fold increase in carriage of serotype 6C in 2011 (P = 0.026). Vaccination with PCV7 did not affect pneumococcal density in children colonized by a PCV7 type but did increase density in those colonized with a non-PCV7 type. Antibiotic resistance did not change after vaccine introduction; strains were nonsusceptible to tetracycline (97.2%), trimethoprim–sulfamethoxazole (56.4%), penicillin (34%), erythromycin (22.4%), chloramphenicol (18.8%) and clindamycin (12.4%). Conclusions: Serotype replacement was observed post-PCV7 vaccination with a concomitant, not previously recognized, increased nasopharyngeal density.

Concordance between RT-PCR-based detection of respiratory viruses from nasal swabs collected for viral testing and nasopharyngeal swabs collected for bacterial testing

BACKGROUND Epidemiologic studies of respiratory infections frequently rely on separate sample collections for the detection of bacteria and viruses. The requirement for two specimens presents cost, logistical, and acceptability challenges. OBJECTIVES To determine the agreement in detection of respiratory viruses using RT-PCR between two different types of samples collected on the same day: nasal swabs preserved in viral transport medium (NS) and nasopharyngeal swabs preserved in skim milk-tryptone-glucose-glycerol [STGG] medium (NP), the current standard for pneumococcal colonization studies. STUDY DESIGN Paired NS and NP samples were collected between May 2009 and September 2011 as part of the RESPIRA-PERU study, a large prospective cohort of Andean children <3 years of age. NS samples used polyester swabs and viral transport medium whereas NP samples used rayon wire-handled swabs and STGG medium. Samples were tested for influenza, human metapneumovirus (MPV), respiratory syncytial virus (RSV), human rhinovirus (HRV), parainfluenza virus 3 (PIV3) and adenovirus (ADV) using real-time RT-PCR. We calculated the agreement, and compared cycle thresholds (CT) between NP and NS samples. RESULTS Among 226 paired NP-NS samples, we observed very high agreement with a Kappa statistic ranging from 0.71 for ADV to 0.97 for MPV. CT values were similar for both strategies. CONCLUSIONS NP samples preserved in STGG provide a simple and reliable strategy for identification of both pneumococcus and respiratory viruses. This single specimen collection strategy could be used for epidemiologic studies, especially in resource-limited settings. Furthermore, archived NP-STGG specimens from previous studies could be reliably tested by RT-PCR for viruses.