Aiello, A.E.

De Lastours, V.

Foxman, B.

Malosh, R.E.

English

Carolina Digital Repository

LETTERSPrevalence of Escherichia coli Carriage in theOropharynx of Ambulatory Children and Adults withand without Upper Respiratory SymptomsTo the Editor:Escherichia coli is a common gut commensal and an importanthuman pathogen that rarely causes pneumonia in thecommunity. However, E. coli increasingly causes hospital-acquired pneumonia, particularly among intensive care unit (ICU)patients (1, 2). E. coli pneumonia, similar to other hospital-acquired and ventilator-associated pneumonias, is responsible forlonger ICU and hospital stays, high morbidity and mortality,and increased antibiotic consumption and hospital costs (1, 2).This is particularly true since the recent global emergenceand spread of E. coli strains producing extended-spectrumb-lactamases, which constitute a major public health concern (3).E. coli identified in protected bronchoalveolar lavagespecimens from ICU patients with ventilator-acquired pneumoniais often genetically identical to the strains found in their dentalplaque and oropharyngeal cavity (4, 5). Yet little is known aboutoropharyngeal colonization by E. coli, with most studies datingback 30 years ago (6–9). Because no recent work has addressedE. coli carriage in the community, we aimed to fill this gap inthe literature by estimating the E. coli carriage rates amongotherwise healthy adults and children with and without upperrespiratory symptoms. We detected E. coli using quantitative PCR(qPCR), which is more sensitive than culture.MethodsUsing a collection of oropharyngeal samples from participants intwo community cohort studies ongoing in Southeast Michiganduring the 2012–2013 and 2013–2014 influenza season, theHousehold Influenza Vaccination Effectiveness Study (HIVE) (10)and the eX-FLU study (11), we estimated the prevalence of E. colioropharyngeal carriage among 589 subjects. HIVE participants(range, 2–70 yr old) were recruited among households with at leasttwo children (for details, see Reference 10). eX-FLU participantswere college students (aged 18–21 yr; mean, 19.2 yr) living indormitories and enrolled using a social network referral model.Students suffering from upper respiratory symptoms defined ascough and fever/feverishness, body aches, or chills (cough plus oneof fever/feverishness, chills, or body aches) were requested toprovide samples at onset. Their healthy social contacts (no illnessin the previous 14 d) were also sampled.We used a highly sensitive qPCR assay for E. coli detection,as bacterial load was anticipated to be lower than amonghospitalized patients. We limited our analysis to oropharyngealswabs collected from 152 adults and 186 children from the HIVEstudy at the time of acute respiratory illness (an illness ,7 dduration with cough, fever or feverishness, nasal congestion, chills,headache, body aches, or sore throat) and to 251 college studentsfrom the eX-FLU study, 130 of whom (52%) had upper respiratorysymptoms and 121 of whom were the healthy contacts.Dual throat swabs were collected from participants andconserved in universal transport media and in sterilized skim milkat 2808C. After bacterial DNA extraction from the universalmedia sample, qPCR was performed using primers specific tothe 16S ribosomal genes in E. coli previously designed by ourlaboratory (12). All assays were conducted in triplicate. Ano-template control and E. coli MG1655 positive control wereincluded in every run. Negative samples were those with cyclethreshold (CT) values higher than 40. E. coli MG1655 was used todetermine the accurate limit of detection of qPCR by comparingcultures on MacConkey agar with qPCR results for sequentialdilutions starting with a Macfarlane 5 dilution. In parallel, wecultured on MacConkey agar a subset of skim milk specimensboth from subjects with qPCR results of more than 104 genomiccopies/mL and from E. coli-negative subjects.ResultsAltogether, 21/338 (6.2%) HIVE and 20/251 (7.9%) eX-FLUparticipants carried E. coli, using a detection limit of 103 genomiccopies/mL (P = 0.4) (Table 1). Mean bacterial load for positivesamples was 4.3 Log genomic copies/mL (SD, 0.32), witha maximum of 5.7 Log genomic copies/mL. Using sequentialdilutions of the MG1655 strain, we estimated the limit of detectionby culture to be approximately 105 genomic copies/mL of skimmilk, which is two Logs higher than the qPCR assay. None of theskim milk samples grew E. coli on MacConkey agar. No differencewas found either in carriage rates or relative abundance of E. coliamong positive samples between adults and children, by agegroup in the HIVE cohort, or between subjects with and withoutacute upper respiratory symptoms in the eX-FLU study.DiscussionIn two different large cohorts of ambulatory children and adultswith and without acute respiratory symptoms, we found thatcarriage of E. coli in the throat was a rare event, despite use ofa highly sensitive detection method. E. coli carriage did notdiffer by age, age group, or the existence of upper respiratorysymptoms. Relative bacterial loads were low and unaffected eitherby age or upper respiratory symptoms.Our findings are similar to those of previous studies of subjectsfrom the community (6, 8, 9). A study conducted among 250individuals in Texas published in 1969 found an increasedprevalence in oropharyngeal carriage of gram-negative bacteriaby severity of illness, from 2% in healthy subjects to 57% inThe Household Influenza Vaccine Effectiveness Study is supported by theCenters for Disease Control and Prevention (U01 IP000474) and the NationalInstitute of Allergy and Infectious Diseases (R01 AI097150). The eX-FLUstudy is supported by the Centers for Disease Control and Prevention (U01CK00018501). This work was made possible thanks to an AdvancingScience through Pfizer-Investigator Research Award 2013 (B.F.).Author Contributions: Conception and design: V.d.L. and B.F.; samplecollections: R.E.M. and A.E.A.; experiments: V.d.L.; analysis andinterpretation: V.d.L. and B.F.; and drafting the manuscript: V.d.L., R.E.M.,A.E.A., and B.F.Letters 461 “moribund” patients (9). A 1994 study following 114 healthyinfants from birth to 2 years detected, using culture, a prevalenceof E. coli throat carriage ranging from 0% to 13% (13). Theprevalence of gram-negative rods in a 1975 study among 100healthy individuals aged 3–70 years (mean age, 43 years) who didnot take antibiotics in the previous year was 17% (14).Although our study population was weighted heavily towardchildren and young adults, our sample did include 63 adults aged41–70 years. In this largest cohort of older adults assessed todate, the prevalence of oropharyngeal carriage of E. coli was 4.8%(3/63). This older population is more likely to have chronicillnesses and be hospitalized in an adult ICU. In addition, othershave found higher rates of E. coli carriage in hospitalized children(including some in ICU) than in the community (6). The largeage span covered by our population of subjects confirms previousfindings that E. coli colonization is rare in ambulatory subjects.Carriage rates of E. coli in the oropharynx of patients in theICU are far greater (even as detected using culture) than thoseobserved in the community (9, 15, 16). More severely ill ICUpatients, and those with diabetes or alcoholism (7, 9), are at greaterrisk for colonization with gram-negative bacteria, especially if theirtreatment includes mechanical ventilation (15). Further, a studypublished in 1994 found that patients colonized with gram-negative bacteria (including E. coli) were more likely to developgram-negative bacterial pneumonia during their ICU stay (15). In2012, 132 French ICU patients were screened for E. coli usingculture: 37 (28.0%) were colonized in their oropharynx, 13 alsohad lung colonization, and 12 patients had both lung colonizationand clinical E. coli pneumonia (16). Others have shownthat colonization by E. coli occurs in the first 4 days afterhospitalization (15). Therefore, a major shift in E. coli carriageseems to occur upon admission to an ICU. This probably explainswhy ICU patients are at higher risk of developing E. colipneumonia.We hypothesize that E. coli oropharyngeal colonization isa multifactorial process promoted by prolonged supine position,inhalation from the stomach, modified gastric pH resulting fromthe common use of proton inhibitors, and multiple interactionswith healthcare workers and/or potentially from some disturbedlocal immunity. These factors may explain why such low ratesof E. coli are found in the oropharynx of ambulatory subjectscompared with those found in ICU patients, in turn explainingthe increased risk for E. coli pneumonia in ICU subjects, ascolonization appears to precede inhalation in the lungs (15, 16).One report suggests that E. coli colonizing the oropharynx andsubsequently responsible for ventilator-associated pneumoniaoriginates from the subjects’ own gut (16). Further studies areneeded to determine the dynamics of and risk factors forE. coli colonization of the oropharynx and how frequentlyoropharyngeal and intestinal E. coli are identical to determineeffective prevention and control strategies among ICU patients.Author disclosures are available with the text of this letter atwww.atsjournals.org.Acknowledgment: The authors thank the Household Influenza VaccineEffectiveness study and eX-FLU participants and staff for allowing usto use the oropharyngeal samples. V.d.L. would like to thank thePhilippe Foundation and the Assistance-Publique Hôpitaux de Paris forfinancial support.Victoire de Lastours, M.D., Ph.D.Ryan E. Malosh, M.P.H.University of Michigan School of Public HealthMichiganAllison E. Aiello, Ph.D.University of North Carolina Gillings School of Global Public HealthNorth CarolinaBetsy Foxman, Ph.D.University of Michigan School of Public HealthMichiganReferences1 Chastre J, Fagon J-Y. Ventilator-associated pneumonia. Am J RespirCrit Care Med 2002;165:867–903.2 Vincent J-L, Rello J, Marshall J, Silva E, Anzueto A, Martin CD, MorenoR, Lipman J, Gomersall C, Sakr Y, et al.; EPIC II Group ofInvestigators. International study of the prevalence and outcomes ofinfection in intensive care units. JAMA 2009;302:2323–2329.3 Livermore DM, Canton R, Gniadkowski M, Nordmann P, Rossolini GM,Arlet G, Ayala J, Coque TM, Kern-Zdanowicz I, Luzzaro F, et al.CTX-M: changing the face of ESBLs in Europe. J AntimicrobChemother 2007;59:165–174.4 Heo S-M, Haase EM, Lesse AJ, Gill SR, Scannapieco FA. Geneticrelationships between respiratory pathogens isolated from dentalplaque and bronchoalveolar lavage fluid from patients in theintensive care unit undergoing mechanical ventilation. Clin Infect Dis2008;47:1562–1570.Table 1. Oropharyngeal carriage of Escherichia coli in subjectsfrom the community in southeast Michigan participating in theHousehold Influenza Vaccine Effectiveness Study (participantsin a household study with acute respiratory illness during2013–2014 influenza season) and the eX-FLU study (collegestudents with upper respiratory symptoms and their healthycontacts during the 2012–2013 influenza season)Study by SelectedCharacteristicsTotal Numberof Participants(n)Prevalence ofEscherichiacoli [n (%)]Household InfluenzaVaccination EffectivenessStudy (n=338)Age, yr2–3 20 2 (10)4–6 74 5 (6.8)7–15 92 7 (7.6)21–30 8 031–40 81 4 (4.9)41–50 56 3 (5.4)51–60 6 061–70 1 0All ages 338 21 (6.2)eX-FLU (n=251)*Upper respiratory symptoms† 130 10 (7.7)Healthy contact 121 10 (8.3)All 251 20 (7.9)Escherichia coli was detected using quantitative polymerase chainreaction.*Participants in the eX-FLU study were aged 18–21 years, with a meanage of 19.2 years.†Defined as cough 1 at least fever/feverishness, body aches, or chills.462 AnnalsATS Volume 12 Number 3| March 2015LETTERS 5 El-Solh AA, Pietrantoni C, Bhat A, Okada M, Zambon J, Aquilina A,Berbary E. Colonization of dental plaques: a reservoir of respiratorypathogens for hospital-acquired pneumonia in institutionalizedelders. Chest 2004;126:1575–1582.6 Sedgley CM, Samaranayake LP. Oral and oropharyngeal prevalence ofEnterobacteriaceae in humans: a review. J Oral Pathol Med 1994;23:104–113.7 Mackowiak PA, Martin RM, Jones SR, Smith JW. Pharyngealcolonization by gram-negative bacilli in aspiration-prone persons.Arch Intern Med 1978;138:1224–1227.8 Hable KA, Washington JA II, Herrmann EC Jr. Bacterial and viral throatflora. Comparison of findings in children with acute upperrespiratory tract disease and in healthy controls during winter. ClinPediatr (Phila) 1971;10:199–203.9 Johanson WG, Pierce AK, Sanford JP. Changing pharyngeal bacterialflora of hospitalized patients. Emergence of gram-negative bacilli.N Engl J Med 1969;281:1137–1140.10 Ohmit SE, Petrie JG, Malosh RE, Cowling BJ, Thompson MG, ShayDK, Monto AS. Influenza vaccine effectiveness in the communityand the household. Clin Infect Dis 2013;56:1363–1369.11 Davis B, de Lastours V, Aiello A, Srinivasan U, Foxman B. Influenza-like illness is associated with increased Streptococcus pneumoniaecarriage among otherwise healthy college students. Presented atthe Society for Epidemiologic Research 47th Annual Meeting. June24–27, 2014, Seattle, Washington. Abstract 61812 Srinivasan U, Ponnaluri S, Villareal L, Gillespie B, Wen A, Miles A,Bucholz B, Marrs CF, Iyer RK, Misra D, et al. Gram stains: a resourcefor retrospective analysis of bacterial pathogens in clinical studies.PLoS ONE 2012;7:e42898.13 Barrie JD, Gallacher JB. The significance of Escherichia coli in theupper respiratory tract of children under 2 years of age. PostgradMed J 1975;51:373–381.14 Rosenthal S, Tager IB. Prevalence of gram-negative rods in the normalpharyngeal flora. Ann Intern Med 1975;83:355–357.15 Johanson WG Jr, Pierce AK, Sanford JP, Thomas GD. Nosocomialrespiratory infections with gram-negative bacilli. The significance ofcolonization of the respiratory tract. Ann Intern Med 1972;77:701–706.16 Messika J, Magdoud F, Clermont O, Margetis D, Gaudry S, Roux D,Branger C, Dreyfuss D, Denamur E, Ricard JD. Pathophysiology ofEscherichia coli ventilator-associated pneumonia: implication ofhighly virulent extraintestinal pathogenic strains. Intensive Care Med2012;38:2007–2016.Copyright © 2015 by the American Thoracic SocietyLetters 463LETTERS 

Prevalence of Escherichia coli carriage in the oropharynx of ambulatory children and adults with and without upper respiratory symptoms

https://cdr.lib.unc.edu/downloads/c821gr49p

Prevalence of Escherichia coli carriage in the oropharynx of ambulatory children and adults with and without upper respiratory symptoms

Abstract

Similar works

Full text

Available Versions

Carolina Digital Repository