Table 1.

Paper details identified from the systematic search with results for the genus Bifodobacterium.

Study	Country	Type of Study	Type of Sample	NGS Tecnology	Type of Sequencing	N	Groups	Abundance in COVID-19 Group	Clinical Relevance
Albrich et al., 2022 [8]	Switzerland and Ireland	Cohort	Stool	MiSeq	V3–V4	128 1	32 mild/ moderate 45 severe/non-fatal 22 severe/fatal COVID-19 29 healthy controls	Decreased	Associated with severity
Cui et al., 2022 [9]	China	Case-control	Tongue-coating and stool	MiSeq	V3–V5	195	35 patients post-COVID-19 160 healthy controls	No statistical difference observed	Not associated with recovery process
Ferreira-Junior et al., 2022 [10]	Brazil	Case-control	Stool	MiSeq	V3–V4	220	149 post-COVID-19 71 healthy controls	Decreased in post-COVID-19 and antibiotic-treated	Associated with disease and antibiotic treatment
Gumenyuk et al., 2022 [11]	Russia	Cross-sectional	Stool	SOLiD 5500	Shotgun	208	110 COVID-19 patients 98 healthy controls	Decrease of B. adolescentis	Associated with disease
Hazan et al., 2022 [12]	USA	Cross-sectional	Stool	NextSeq 500/550	Shotgun	70	50 COVID-19 patients 20 exposed controls	Decreased	Associated with severity
Kim et al., 2023 [13]	USA	Cohort	Saliva and nasopharyngeal	MiSeq	V1–V2	144	114 samples COVID-19 positive 30 samples COVID-19 negative	Decreased in ICU group. The genus was associated with lower levels of IL-17F and MCP-1	Associated with severity
Li et al., 2021 [14]	China	Case-control	Stool	BGISEQ-500	Shotgun	66	47 COVID-19 patients 19 healthy controls	Increase of B. longum in COVID-19. B. bifidum was negatively correlated with the severity and B. animalis was positively correlated.	Associated with severity
Liu et al., 2022 [15]	China	Cohort	Stool	NextSeq 550	Shotgun	174	106 COVID-19 (50 PACS) 68 non-COVID-19	Decreased. B. pseudocatenulatum was inversely correlated with PACS at 6 months	Associated with severity and PACS
Maddah et al., 2023 [16]	China 2/Iran 3	Cross-sectional	Stool	MiSeq	V3–V4	30	30 COVID-19 patients 30 healthy controls	Decrease of B. adolescentis	Associated with disease
Mazzarelli et al., 2022 [17]	Italy	Cohort	Stool	MiSeq	V3–V4	97	47 mild COVID-19 50 severe COVID-19	No statistical difference observed	Not associated with severity
Rafiqul Islam et al., 2022 [18]	Bangladesh	Cross-secctional	Stool and saliva	MiSeq	V3–V4	37	22 COVID-19 patients 15 healthy controls	Decreased	Associated with disease
Reinold et al., 2021 [19]	Germany	Cross-secctional	Stool	Novaseq 6000	V3–V4	212	44 mild COVID-19 35 moderate COVID-19 38 severe/critical COVID-19 95 SARS-CoV-2 negative controls	Decreased	Associated with disease
Romani et al., 2022 [20]	Italy	Cohort	Stool	MiSeq	V3–V4	183	68 COVID-19 children 16 non-COVID-19 4 children with MIS	Decreased	Associated with disease
Rueca et al., 2021 [21]	Italy	Cohort	Nasal/ oropharyngeal	IonS5	V2-4-8 e V3-6 e 7-8	39	21 COVID-19 patients 8 HCoV patients 10 healthy controls	Complete depletion in ICU patients	Associated with severity
Sun et al., 2022 [22]	China	Case-control	Stool	Novaseq 6000	Shotgun	71	63 COVID-19 patients 8 non-infected controls	Increase of B. longum and depletion of B. pseudocatenulatum in COVID-19	Associated with severity
Suskun et al., 2022 [23]	Turkey	Cohort	Stool	NovaSeq 6000	V3–V4	39	20 COVID-19 children 25 MIS-C children 19 healthy controls	Increase of B. adolescentis in COVID-19	Associated with severity
Wang et al., 2023 [24]	China	Cohort	Stool	MiSeq	V3–V4	186	59 COVID-19 children 50 asymptomatic caregivers 52 healthy children 25 healthy adults	Decreased	Associated with disease
Yeoh et al., 2021 [25]	China	Case-control	Stool	NovaSeq 6000	Shotgun	178	100 COVID-19 patients 78 non-COVID-19 patients	Depletion of B. adolescentis in COVID-19. B. bifidum was negatively correlated with severity. Increase of B. dentium and depleted B. longum in recovered patients.	Associated with disease severity and recovery process

¹ Patients sequenced. ² Original data. ³ Data reanalysis. MIS: multisystem inflammatory syndrome.