Table 2.
Studies analysing the relationship between RTIs and GM in children.
| Author, Year of Publication, Country | Study Design | No. of Subjects and Population | Age Range | Aim | Main Results |
|---|---|---|---|---|---|
| Hasegawa et al. [43], 2016, Massachusetts | Case-control | 40 hospitalized infants with bronchiolitis vs. 115 healthy controls. | <12 months | To identify faecal microbiota profiles and compare the likelihood of bronchiolitis. | The highest likelihood of bronchiolitis in the Bacteroides-dominant profile compared to the Enterobacter/Veillonella-, Escherichia- and Bifidobacterium-dominant profiles. |
| Harding et al. [44], 2020, Louisiana | Case-control | 53 hospitalized infants with RSV- bronchiolitis vs. 37 healthy controls. | <7 months | To compare GM in children with different bronchiolitis severity vs. controls. | Increase in S24_7, Clostridiales, Odoribacteraceae, Lactobacillaceae, and Actinomyces in patients with bronchiolitis compared to controls. Increase in S24_7 in severe patients compared to moderate patients and controls. |
| Alba et al. [45], 2021, Spain | Case-control | 58 infants with RSV-bronchiolitis vs. 17 healthy controls. | <24 months | To compare GM in children with bronchiolitis vs. controls. | No significant differences regarding the most abundant genera (Bifidobacterium, Streptococcus, and Escherichia) between infants with bronchiolitis and controls. |
| Reyman et al. [12], 2019, Netherlands | Prospective single centre | 74 VD children, 46 born by CS. | First year of life | Differences in GM between VD and CS-born children. Correlation between GM and RTIs in the first year of life. |
Prevalence of Bifidobacterium in the first week of life was significantly associated with fewer RTI events. Klebsiella and Enterococcus prevalence were negatively associated with fewer RTI events. |
| Li et al. [19], 2019, China | Case-control | 26 children with RRTIs vs. 23 healthy controls. | >5 years | To compare GM in children with RRTIs vs. controls. To identify GM biomarkers that could discriminate RRTI status. |
Alpha diversity in the RRTI patients’ GM was significantly lower. Reduction of Verrucomicrobia and Tenericutes phyla with increase in Enterococcus and decrease in Eubacterium in the RRTI group. Enterococcus, taken as a biomarker, showed the highest accuracy in identifying RRTIs. |
| Li et al. [46], 2019, China | Case-control | 90 children with RRTIs vs. 30 heathy controls. | <11 years | To compare GM in children with RRTIs vs. controls. Effects of probiotics on GM and RRTIs. |
Significant reduction of lactobacilli and bifidobacteria in children with RRTIs. |
| Xu et al. [47], 2021, China | Case-control | 9 children with COVID-19 vs. 14 healthy controls. | <12 years | To compare GM in children with COVID-19 vs. controls. | Increased representation of Bacteroidetes and Firmicutes, and decrease in Proteobacteria, with significant increase in opportunistic pathogenic and environmental bacteria in COVID-19 children. |
COVID-19: coronavirus disease 2019; CS: cesarean section; GM: gut microbiota; RRTI: recurrent respiratory tract infection; RTI: respiratory tract infection; VD: vaginally delivered.