Colonization rate of bacteria in the throat of healthy infants

https://doi.org/10.1016/S0165-5876(01)00635-8Get rights and content

Abstract

Objective: the human throat is a major ecological site for various bacteria that can reach neighbouring sterile sites and cause mild infections or invasive diseases. The aim of this study was to investigate the carriage rate of several potential pathogens in the throat of healthy children under the age of 2 years. Methods: cultures were taken from the tonsils of 1000 healthy infants aged 1–24 months attending well-baby clinics, who had not received antibiotic therapy during the preceding 14 days. Results: one hundred and ninety-eight (19.8%) cultures were positive. Thirteen (1.3%) cultures were positive for β-haemolytic Streptococcus group A, 23 (2.3%) for Streptococcus pneumoniae. In 28 (2.8%) and 24 (2.4%) cultures, respectively, Haemophilus influenzae Type b and non-typeable Haemophilus influenzae were recovered. The commonest bacterium found was Staphylococcus aureus (99 positive cultures). Eleven children carried two species of bacteria and from one 6-month-old child three species were isolated concurrently. Conclusions: it is concluded that children younger than 2 years of age can be carriers of several types of pathogenic bacteria. In contrast to many other studies, in this study β-haemolytic Streptococcus group A was isolated from the tonsils of children younger than 1 year of age.

Introduction

The relationship between humans and their microbes is very complex. Resident micro-organisms are normally associated with a particular site and a particular animal host. Host factors (like defence mechanisms) and microbial features (virulence) will influence the result of the process of infection.

A microbe is a pathogen when infection results in disease. Colonization is also an infection but the relationship between the host and the micro-organism is commensal.

When relatively virulent organisms which are known as potential pathogens colonize a human host we consider the patient as a carrier and in many cases this situation is undesirable. Bacterial colonization of the upper respiratory tract occurs as early as the first months of life [1]. The human orophanynx is a primary ecological niche for various bacteria such as Streptococcus pneumoniae, Haemophilus spp., Staphylococcus aureus, coagulase negative staphylococci, β-haemolytic streptococci, Neisseria spp., α-haemolytic streptococci, Moraxella catherallis, Lactobacilli, Corynebacteria, anaerobes, Candida albicans and various protozoa [1]. These microorganisms may infect ordinarily sterile neighbouring sites and cause otitis media, conjunctivitis or sinusitis. Some of them may even penetrate the mucosa and cause invasive diseases such as pneumonia, sepsis or meningitis [1], [2], [3].

Children with recurrent episodes of otitis media have been shown to have a higher carrier rate of potentially pathogenic bacteria, including Streptococcus pneumoniae, non-typeable Haemophilus influenzae, Moraxella catarrhalis and Streptococcus group A, than healthy children [3], [4], [5].

It was possible to isolate, by throat culture, a type of capsulated Streptococcus pneumoniae, similar to that isolated from the middle ear, a short time before the onset of otitis media [6]. Furthermore, a correlation of 95–100% was found between the bacteria isolated from the middle ear and those obtained by a nasopharyngeal culture during an ear infection [6]. During outbreaks of meningitis in day-care centres caused by Haemophilus influenzae Type b, the pathogen was found in the throat of children who were in contact with the sick infants, but not in those who were not [7], [8]. During pneumococcal outbreaks in day care centres the pathogen was found in up to 86% of the healthy children in the centre [9]. In cases of tonsillitis caused by Streptococcus group A, the same pathogen was frequently found in the throat of healthy contacts [10].

The purpose of this study was to determine the current carrier state of healthy Israeli infants who are not exposed to infectious diseases in day care centres. The bacteria studied included the frequent pathogens in our area: β-haemolytic streptococci (groups A, C and G), Streptococcus pneumoniae, Haemophilus influenzae Type b, non-typeable Haemophilus influenzae, Neisseria meningitidis, and Staphylococcus aureus.

The frequency of the presence of these bacteria concurrently in the throat of healthy young children in Israel has not been reported earlier.

Section snippets

Materials and methods

The study was approved by the ethics committee of Assaf Harofeh Medical Centre and the Israel Ministry of Health. Signed informed consent was obtained from the parents before enrolment.

Inclusion criteria included healthy children aged 1–24 months. The infants were examined for a routine follow-up in ten well-baby care clinics, where children are seen for vaccinations and periodic physical examination. These children were afebrile, and had no upper respiratory tract symptoms, tonsillar exudate,

Results

One thousand children aged 1–24 months (mean±S.D.=10±6 m) 530 males and 470 females were included in the study. Table 1 shows the frequency of the isolation of various pathogens from children's throats.

The 13 (1.3%) children with Streptococcus group A ranged in age from 3 to 21 months (mean±S.D.=10.4±7.5); six were in their first year of life, the youngest being a 3-month-old infant (mean±S.D.=5.5±3 months). Typing of Streptococcus group A for M precipitation and T agglutination was carried out

Discussion

In the present study we investigated the presence of several frequent pathogenic bacteria in the throat of healthy infants.

Pharingotonsillar flora is affected by many demographic factors like climate, age, the extent of exposure to infectious diseases, or vaccines.

A comparison of four sampling methods for detecting pharyngeal infection in symptomatic children showed that the nasopharyngeal swab seemed optimal for the detection of Streptococcus pneumoniae, for Haemophilus influenzae the

Acknowledgements

We would like to thank Zeev Gorodnitzky, MSc, and Zinaida Korenman, MSc, from the National Centre of Streptococci and Pneumococci Laboratories, Ministry of Health Central Laboratory, Jerusalem, Israel, for serotyping the isolates, and Shahnaz Zarini and Hani Moshe for typing the manuscript.

References (32)

  • T.V. Murphy et al.

    Risk of subsequent disease among day-care contacts of patients with systemic Hemophilus influenzae type B disease

    N. Engl. J. Med.

    (1987)
  • T. Cherian et al.

    A cluster of invasive pneumococcal disease in young children in child care

    JAMA

    (1994)
  • T.D. Smith et al.

    Group A Streptococcus associated upper respiratory tract infections in a day-care center

    Pediatrics

    (1984)
  • J.M. Miller, T.H. Holmes, Specimen collection, transport and storage, in: R.P. Murray (Ed.), Manual of Clinical...
  • J.O. Sneed

    Processing and interpretation of upper respiratory tract specimens

  • D.R. Johnson, E.L. Kaplan, Laboratory diagnosis of group A streptococcal infections, WHO collaborating center for...
  • Cited by (19)

    • Nasopharyngeal carriage of Streptococcus pneumoniae in healthy Turkish infants

      2008, Journal of Infection
      Citation Excerpt :

      Seven valent pneumococcal conjugate vaccine, which is currently available in Turkey, covers 51.2% of the serotypes isolated in our study. In the literature, NP carriage rates among healthy infants under 2 years of age not attending daycare centers range between 19 and 93%.17–23 In some Asian and African countries such as India,17 Indonesia,18 Gambia,19 and the carrier rates were 70.2, 48, and 90%, respectively, while in some European countries, like France,20 and Finland,22 it was lower (34 and 19.7%, respectively).

    • Selected bacterial recovery in Trinidadian children with chronic tonsillar disease

      2008, Brazilian Journal of Otorhinolaryngology
      Citation Excerpt :

      The few studies reporting staphylococcal recovery in tonsillar flora in children do not demonstrate differences between pathological and normal tonsils. S. aureus was the commonest bacterium (9.9%) cultured from tonsils of 1000 healthy Israeli children <2 years32. Staphylococcal prevalence was similar with or without tonsil pathology in Brazilian33 (27% versus 28%) and Dutch4 children (6% in both groups).

    • Streptococcus pneumoniae colonisation: The key to pneumococcal disease

      2004, Lancet Infectious Diseases
      Citation Excerpt :

      Not all risk groups for pneumococcal diseases show increased rates of colonisation compared with the general population. For example children with HIV infection and sickle-cell disease have similar colonisation rates to healthy children (table 1).70,92 This similarity is a result of the underlying immune disorder: instead of a defect or augmented challenge of the primary defence mechanism against pneumococal invasion, the immune disorder is related to an impaired response to or clearance mechanism for pneumococci after invasion has occurred.

    View all citing articles on Scopus
    View full text