Impact of antibiotic consumption on the carriage of antibiotic-resistant bacteria by school children

Abstract

Background

Antibiotic consumption in the paediatric population is one of the key drivers of the emergence and spread of antimicrobial resistance, which is a serious global threat to public health and clinical medicine. The aims of this study were to investigate systemic antibiotic consumption in school children and to assess the associations among antibiotic consumption, carriage rate and resistance of respiratory pathogens residing in the upper respiratory tract mucosa.

Methods

In this prospective study, throat and nasopharyngeal swabs from 450 school children, 6–15 years of age (225 healthy children and 225 patients who were ambulatory treated for upper respiratory tract infection), were processed in 2014 in Rijeka, Croatia, and clinical data were obtained via a questionnaire.

Results

In total, 17% of the children had consumed an antibiotic in the previous 6 months, including 7% of the healthy children and 27% of the acutely ill patients. The most commonly prescribed antibiotics were amoxicillin (26%), amoxicillin with clavulanic acid (26%) and macrolides (18%). Respiratory pathogens were more frequently isolated from children who had consumed an antibiotic in the previous 6 months [odds ratio (OR) 3.67, P < 0.001]. Antibiotic-resistant bacteria were also more frequent in children who had been exposed to antibiotics (OR 5.44, P < 0.001).

Conclusions

Penicillins are the most frequently used antibiotics among school children. The results of this study demonstrate that antibiotic consumption is linked with higher carriage rates and resistance rates of respiratory tract pathogens. Therefore, rational use of antibiotics could prevent the emergence and spread of resistant bacteria.

Introduction

Antimicrobial resistance is a well-recognized global threat to public health and clinical medicine.^1,2 Antibiotic consumption is one of the key drivers of the emergence and spread of antimicrobial resistance in community. Most antibiotics are prescribed in ambulatory care, and in Croatia, more than 90% of all antibiotics are prescribed in the outpatient setting.^2–4 In Europe, extreme differences in the prescribing of antibiotics and antimicrobial resistance rates have been recorded between northern countries and southern and eastern countries. Croatia belongs to a group of countries with high overall antibiotic consumption and consequently high antimicrobial resistance among bacteria that commonly cause infections in community.^3,5–7 The association between antibiotic consumption and bacterial resistance in primary care has been confirmed at both the individual and population levels.^6,8,9

Antibiotics are mainly prescribed for upper respiratory tract infections, which are often self-limiting and viral in origin. Broad-spectrum antibiotics are often inappropriately prescribed for these infections, causing significant financial burden and leading to the emergence and spread of bacterial resistance.^4,10–12 Antibiotics are the most commonly prescribed drugs for children, especially among the pre-school population.^10,12,13 School children are not affected as much as children in day-care centres and nurseries, as school children are less susceptible to infections than the children in these facilities.^13–15 However, school children may also serve as important reservoir of antibiotic-resistant bacteria in the community.

The aims of this study were to investigate systemic antibiotic consumption by school children and to evaluate the associations among antibiotic consumption, carriage rate and resistance of respiratory pathogens residing in the upper respiratory tract mucosa. We analyzed the incidence and resistance patterns of the most common respiratory pathogens, namely, Streptococcus pyogenes, Streptococcus pneumoniae, Moraxella catarrhalis and Haemophilus influenzae.

Methods

Study population

All data on children enrolled in this prospective study were processed during the school year, from 29 January 2014 to 16 June 2014 and 22 September 2014 to 04 November 2014. Throat and nasopharyngeal samples were collected from 450 children between 6 and 15 years of age. Two groups of school children were included in the study, 225 healthy children with no signs or symptoms of respiratory tract infection in the previous 2 weeks and 225 patients receiving ambulatory treatment for upper respiratory tract infection. The children attended 31 elementary schools in the city of Rijeka, Croatia and the surrounding area. Parents, legal representatives or guardians of the participating children provided written informed consent and filled out a questionnaire on demographic and socioeconomic characteristics. All children included in the study shared similar socioeconomic statuses. Attending physicians provided data regarding antibiotic consumption and the presence or absence of signs and symptoms of respiratory infection in the previous 6 months. Immunocompromised children were excluded from the study because of the increased sensitivity of these children to infections (especially respiratory tract infections).

Sample collection

Throat and nasopharyngeal swabs (Venturi Transystem, Copan Italia S.P.A, Brescia, Italy) were obtained from each child. Five paediatricians, two general practitioners, two family physicians (from a private practice and from the Health Care Centre of Primorsko-Goranska County, Rijeka) and a school and university physician (from the Teaching Institute of Public Health of Primorsko-Goranska County, Rijeka) participated in the study. The swabs were transported within 12 h of collection in Amies transport medium with charcoal to the Department of Microbiology of the Teaching Institute of Public Health of Primorsko-Goranska County (Rijeka), where the swabs were processed immediately.

Bacterial isolation and identification

Each swab was immediately inoculated on Columbia agar containing 5% sheep blood (bioMérieux, Marcy I’ Etoile, France) and streaked with Staphylococcus aureus. The plates were incubated at 36°C in a 5% CO2-enriched atmosphere and examined for growth after 24–48 h. Bacterial identification of Streptococcus pyogenes was carried out by following standard procedures for colony morphology analysis (β-haemolysis), Gram staining, the catalase test, bacitracin susceptibility testing (BBL, Becton, Dickinson and Company, Sparks, MD, USA) and latex agglutination test (Slidex Strepto Plus, bioMérieux, Marcy I’ Etoile, France). Streptococcus pneumoniae was identified by colony morphology analysis (α-haemolysis), Gram staining, the catalase test, optochin susceptibility testing (BBL, Becton, Dickinson and Company, Sparks, MD, USA) and bile solubility testing. Moraxella catarrhalis was identified by colony morphology analysis (γ-haemolysis), Gram staining, the oxidase test (Bio-Rad, Marnes-la Coquette, France), the catalase test, nitrate reduction testing (nitrate agar, HiMedia Laboratories Pvt. Ltd., Mumbai, India) and the DNAse test (DNAse agar, Oxoid Ltd., Basingstoke, Hampshire, England) and based on the occurrence of a phenomenon called ‘hockey puck sign’ Haemophilus influenzae was identified by colony morphology analysis (γ-haemolysis), Gram staining, the catalase test and based on satellite formation around Staphylococcus aureus and the requirement for X and V factors for growth (Oxoid Ltd., Basingstoke, Hampshire, England). Only one isolate per patient was included in the study.

Antimicrobial susceptibility testing

Bacterial isolates were tested by the disk diffusion method and minimum inhibitory concentrations (MIC) determination when needed according to the recommendations of the European Committee on Antimicrobial Susceptibility Testing (EUCAST),¹⁶ using Mueller-Hinton Fastidious agar (bioMérieux, Marcy I’ Etoile, France) and antibiotic disks (Bio-Rad, Marnes-la Coquette, France). Streptococcus pyogenes was tested for susceptibility to erythromycin, clindamycin and penicillin. Streptococcus pneumoniae was tested for susceptibility to erythromycin, clindamycin, trimethoprim-sulfamethoxazole and penicillin. For pneumococcal isolates with zones of <20 mm diameters around the oxacillin disks, MICs were determined with penicillin, ampicillin, cefuroxime and ceftriaxone using a gradient strip test (E-test, bioMérieux, Marcy I’ Etoile, France). Moraxella catarrhalis was tested for susceptibility to erythromycin, trimethoprim-sulfamethoxazole, cefuroxime, ceftriaxone, ampicillin and amoxicillin with clavulanic acid. Haemophilus influenzae was tested for susceptibility to trimethoprim-sulfamethoxazole, cefuroxime, ceftriaxone, ampicillin and amoxicillin with clavulanic acid. For all Moraxella catarrhalis and Haemophilus influenzae isolates, the production of β-lactamase was tested with the nitrocefin test (Cefinase, bioMérieux, Marcy I’ Etoile, France). Streptococcus pneumoniae ATCC 49619 and Haemophilus influenzae NCTC 8468 were included as quality control strains.

Statistical analysis

Statistical analysis was performed using the statistical packages Statistica 12.0 (StatSoft Inc., Tulsa, USA) and MedCalc 12.0.0 (MedCalc Software, MariaKerke, Belgium). Data are presented with frequencies (absolute, relative), odds ratios (ORs) and 95% confidence intervals (95% CIs). For categorical variables, chi-square test, Yates correction when needed, Fisher’s exact test and proportion test were conducted. P-values <0.05 were considered statistically significant.

Results

The study population included 450 children, of whom 225 were healthy and 225 presented with upper respiratory tract infections, 219 were female and 231 were male. The median age was 12, with ages ranging from 6 to 15 years. From the total of 450 school children, 75 (17%) had used at least one antibiotic in the previous 6 months, including 15 (7%) healthy children and 60 (27%) patients presenting with upper respiratory tract infections. Four children (5%) received more than one antibiotic in the previous 6 months [1 (1%) healthy child and 3 (4%) acutely ill patients]. Overall, boys had higher prescription rates (41, 55%) than did girls (34, 45%) in the study period. Antibiotics were prescribed to 22 male (58%) and 16 female (42%) children in the age group 6–9 years and 19 male (51%) and 18 female (49%) children in the age group 10–15 years. Among the 75 antibiotic consumers, 38 children (51%) were in the age group 6–9 years and 37 children (49%) were 10–15 years old. There were 41 antibiotic treatments recorded in the age group 6–9 years and 39 treatments in the age group 10–15 years.

No difference was observed between the age groups of children in terms of the prescribing of antibiotics, except for the prescribing of second- and third-generation cephalosporins, which were more frequently prescribed to children in the age group 6–9 years than to those in the age group 10–15 years (table 1). Among the antibiotics consumed 6 months prior to the latest visit to the doctor, the most widely prescribed antibiotics were penicillins (65%), which were followed by macrolides (18%) and cephalosporins (15%). Amoxicillin and amoxicillin with clavulanic acid were each used in 21 treatments, and phenoxymethylpenicillin was used in 10 treatments. Azithromycin was used in 13 treatments and clarithromycin in 1 treatment. Cephalexin was used in three treatments, cefuroxime axetil in six treatments and cefixime in three treatments (table 1). Penicillin with an extended spectrum and penicillin in combination with a beta-lactamase inhibitor constituted most of the penicillin consumption. Beta-lactamase resistant penicillins were not used (figure 1).

According to the clinical diagnosis in the 75 children (80 treatments) who received antibiotics, 67% of the antibiotics were prescribed for upper respiratory tract infections, 23% for lower respiratory tract infections, 5% for urinary tract infections, 4% for skin infections and 1% for other diagnoses.

In the group of children who had received an antibiotic in the previous 6 months, respiratory pathogens were more frequently isolated than they were in the group of children not exposed to antibiotics (OR 3.67, P < 0.001; table 2). From the 75 children who had received an antibiotic in the previous 6 months, 21 antibiotic-resistant bacteria were isolated, and 25 antibiotic-resistant bacteria were isolated from the 375 children who had not been exposed to antibiotics, which is a statistically significant difference (OR 5.44, P < 0.001; table 3).

Discussion

Croatia is a country with high antibiotic consumption rate that corresponds to the European average (ESAC-Net).³ School-aged children are not particularly prone to infections and are therefore not considered to be important targets for rationalizing the use of antibiotics. In this study, we showed that 7% of the healthy children had consumed antibiotics in the previous 6 month, and this percentage was even higher for children presenting with upper respiratory tract infection (27%). According to the Special Euro barometer Report for 2016, 36% of all Croatians had been prescribed antibiotics in the previous year.¹⁷

Wide variations in the prescribing of antibiotics to children have been shown among countries.^18–21 The prevalence of antibiotic use in children aged 0–19 years was higher in Italy and Canada (42–57%) than it was in the Netherlands and the United Kingdom (14–21%).²¹ Unlike our study, most of the studies include pre-school children, to whom antibiotics are much more commonly prescribed.^13,18–20 Of particular concern is the fact that in many countries, amoxicillin with clavulanic acid is the antibiotic most frequently prescribed to children.^13,22 In countries with more rational antibiotic prescribing, amoxicillin (the Netherlands)^18,19 or phenoxymethylpenicillin (Denmark, Sweden)^18,23 are more frequently used. In our study, amoxicillin and amoxicillin with clavulanic acid were used with equal frequency, and second- and third-generation cephalosporins were used by younger children (6–9 years) with alarming frequency.

Our study demonstrated that 90% of the antibiotics were prescribed for respiratory tract infections, primarily upper respiratory tract infections (67%), similarly as in other studies.^20,23

Our study confirmed a statistically significant association between antibiotic consumption and antimicrobial resistance of respiratory pathogens isolated from throat and nasopharyngeal swabs from school children. Therefore, antibiotic use in school children is an important driver of antimicrobial resistance in the community. In this study, we also found a statistically significant relationship between antibiotic use and the carriage rate of Streptococcus pyogenes, Streptococcus pneumoniae and Haemophilus influenzae. This result implies that antibiotic consumption may predispose children to colonization by potential respiratory pathogens.

Even in Sweden and the Netherlands, countries with low antibiotic prescription rates, several studies have emphasized the need for increased prudence in outpatient antibiotic use in children.^19,23–25 Mölstad et al. showed that the multi-disciplinary coordinated programme STRAMA (the Swedish Strategic Programme for the Rational Use of Antimicrobial Agents and Surveillance of Resistance) has greatly contributed to the reduction of total antibiotic use by 15% and outpatient antibiotic use by 20% during the 1995–2004 period in Sweden. This decrease was particularly evident for macrolides (65%). STRAMA recommends phenoxymethylpenicillin as the drug of choice to treat most respiratory tract infections, which is reflected in the high use of narrow-spectrum penicillins in this country.^23,25 Since 2006, the Croatian Intersectoral Coordination Mechanism for the Control of Antimicrobial Resistance (Interdisciplinarna Sekcija za Kontrolu Rezistencije na Antibiotike, ISKRA) has been coordinating all activities related to antibiotic resistance control at the national level. These activities include surveillance of resistance and antibiotic consumption,⁴ education of clinicians, patients and pharmacists⁷ and development of national guidelines on antibiotic use. Although ISKRA has published national guidelines for antimicrobial therapy for sore throat which promote the use of phenoxymethylpenicillin²⁶ for this indication the results of our study indicate that much needs yet to be done to improve compliance with the guidelines and that there is a need for developing guidelines for other respiratory tract infections for which antibiotics should generally not be prescribed. Large variations in the prescribing of antibiotics at the community level have been shown to be influenced by many factors, such as socioeconomic and sociocultural factors and patients’ and prescribers’ attitudes, beliefs and knowledge regarding antibiotic use and resistance.^5,27 André et al.²⁸ observed that the Swedish public had a high level of trust in the restrictive prescribing of antibiotics by doctors and a high awareness of antibiotic resistance. The Dutch public had the same attitudes, beliefs and knowledge regarding antibiotic use and resistance as Swedish citizens. In contrast, Italy and Croatia had poor public knowledge and attitudes regarding antibiotic consumption and resistance.^29,30 Pressure from the pharmaceutical industry, poor quality of physician-patient interaction leading to lack of patients’ trust and poor compliance with prescription guidelines play important roles in the prescribing of antibiotics.²⁷ Our study confirmed the need for increased individual and population level evidence-based studies on antibiotic use and resistance in school children, in order to encourage improvements in the prescribing of antibiotics to this age group.

A limitation of this study is that a small number of respiratory pathogens were obtained from both healthy and ill children, which might have influenced the statistical analysis. Additionally, a relatively small number of patients received antibiotics, so the results of the antibiotic use analysis may not match the results of population-based studies. However, our study has indicated an apparent link between antibiotic consumption, carriage of respiratory pathogens and resistance rates.

Conclusions

Our findings suggest that school children represent a significant reservoir of antibiotic-resistant bacteria in the community, and this age group should also be considered a target for intensive education on the rational prescribing of antibiotics, at both the patient and health care professional level.

Ethical approval

The study was approved by the Ethics Committee of the Teaching Institute of Public Health of Primorsko-Goranska County in Rijeka, the Ethics Committee of the Health Care Centre of Primorsko-Goranska County in Rijeka and the Ethics Committee of the University of Rijeka Faculty of Medicine.

Acknowledgements

The authors express sincere gratitude to all the children who participated in the study and their parents, legal representatives or guardians. The authors also thank family physicians M. Ferri-Matić and B. Popović; general practitioners D. Škarpa Gudelj and A. Beževan; and paediatricians S. Kilvain, J. Prospero and M. Brajović Blašković for participating in sample and data collection.

Conflicts of interest: None declared.

References