Antibiotic resistance of Streptococcus pneumoniae, isolated from nasopharynx of preschool children with acute respiratory tract infection in Lithuania

Abstract

Background: Increasing pneumococcal resistance to commonly used antibiotics and multidrug resistance is a serious public health concern. Data on distribution of resistant Streptococcus pneumoniae (SPn) strains among children in Lithuania are limited. We evaluated the circulation of SPn serotypes and antimicrobial susceptibility among preschool children in Lithuania before the introduction of universal infant pneumococcal vaccination.

Methods: A prospective study was carried out from February 2012 to March 2013 in five cities of Lithuania. A total of 900 children under six years of age who presented to primary care centre or a hospital emergency department with acute respiratory tract infection were enrolled in the study. Nasopharyngeal swabs were obtained and cultured for SPn. Positive samples (n = 367) were serotyped and tested for antimicrobial susceptibility. Associations of pneumococcal non-susceptibility with study site, season, age, sex, attendance of day care centre and treatment with antimicrobials (between one and six months prior the study) were evaluated.

Results: About a half (56.7 %) of SPn strains were susceptible to all the antibiotics tested. Pneumococcal non-susceptibility to penicillin, erythromycin, clindamycin and trimethoprim-sulphamethoxazole was 15.8, 21.3, 16.9 and 27.3 %, respectively. None of the tested isolates was resistant to norfloxacin or vancomycin. We found a geographical variation of pneumococcal resistance within the cities of the country. Age, sex, the attendance of day care centre and treatment with antimicrobials prior the study was not significantly associated with a carriage of non-susceptible SPn strains. Among non-susceptible SPn serotypes 67.9 %-82.4 % were present in currently available pneumococcal conjugate vaccines.

Conclusions: The rates of nasopharyngeal SPn susceptibility to penicillin and macrolides are still high among preschool children in Lithuania, however they are lower compared with previous studies. A strict policy with respect to antibiotic prescription together with widespread use of vaccination could potentially reduce the carriage rate of antibiotic-resistant pneumococci in our country.

Keywords: Antibiotic resistance; Nasopharyngeal colonization; Preschool children; Respiratory tract infection; Streptococcus pneumoniae.

Fig. 1

Distribution of non-susceptible Streptococcus pneumoniae nasopharyngeal strains in the study sites of Lithuania. TMP-SMX - trimethoprim–sulphamethoxazole; MDR - multidrug resistance. Study sites were primary care centres of Vilnius, Kaunas, Klaipeda, Panevezys and Alytus and the emergency department of Children’s Hospital, Affiliate of Vilnius University Hospital Santariskiu Klinikos in Vilnius. Note that Alytus was excluded from this comparison because of the small number of S. pneumoniae isolates (n = 2). Using univariable Poisson regression analysis, significant differences were found in these comparisons: non-susceptibility to penicillin was higher in Panevezys vs Vilnius (PR: 2.885, p = 0.000), non-susceptibility to erythromycin was higher in Panevezys vs Vilnius (PR: 1.794, p = 0.007) and Kaunas (PR: 2.140, p = 0.035), resistance to clindamycin was higher in Panevezys vs Vilnius (PR: 2.621, p = 0.000) and Kaunas (PR: 3.424, p = 0.007), non-susceptibility to TMP-SMX was higher in Vilnius vs Panevezys (PR: 1.659, p = 0.039) and MDR was higher in Panevezys vs Vilnius (PR: 3.118, p = 0.000) and Kaunas (PR: 2.663, p = 0.035)

Fig. 2

The most common serotypes of non-susceptible Streptococcus pneumoniae nasopharyngeal strains. TMP-SMX - trimethoprim–sulphamethoxazole; MDR - multidrug resistance