Table 3 Characteristics and clinical presentation of infants hospitalized for bronchiolitis by nasal swab microbiota profile
Variables | Corynebacterium-dominant profile, n = 109 (13.4%) | Haemophilus-dominant profile, n = 59 (7.2%) | Moraxella-dominant profile, n = 106 (13.0%) | Enterobacter-dominant profile, n = 61 (7.5%) | Staphylococcus-dominant profile, n = 363 (44.5%) | Mixed profile, n = 117 (14.4%) | P value |
|---|---|---|---|---|---|---|---|
Characteristics | |||||||
 Age (months), median (IQR) | 3 (1–6) | 5 (3–8) | 4 (2–7) | 4 (2–6) | 3 (2–4) | 4 (2–7) | < 0.001 |
  < 2 | 36 (33.0) | 7 (11.9) | 24 (22.6) | 14 (23.0) | 132 (36.4) | 23 (19.7) | < 0.001 |
  2–5.9 | 44 (40.4) | 25 (42.4) | 48 (45.3) | 34 (55.7) | 178 (49.0) | 58 (49.6) |  |
  6–11.9 | 29 (26.6) | 27 (45.8) | 34 (32.1) | 13 (21.3) | 53 (14.6) | 36 (30.8) |  |
 Male sex | 59 (54.1) | 36 (61.0) | 58 (54.7) | 37 (60.7) | 230 (63.4) | 68 (58.1) | 0.45 |
 Race/ethnicity |  |  |  |  |  |  | 0.07 |
  Non-Hispanic white | 53 (48.6) | 23 (39.0) | 49 (46.2) | 20 (32.8) | 177 (48.8) | 38 (32.5) |  |
  Non-Hispanic black | 18 (16.5) | 11 (18.6) | 22 (20.8) | 22 (36.1) | 80 (22.0) | 30 (25.6) |  |
  Hispanic | 34 (31.2) | 24 (40.7) | 31 (29.2) | 17 (27.9) | 93 (25.6) | 44 (37.6) |  |
  Other | 4 (3.7) | 1 (1.7) | 4 (3.8) | 2 (3.3) | 13 (3.6) | 5 (4.3) |  |
 Parental history of asthma | 30 (27.5) | 15 (25.4) | 42 (39.6) | 26 (42.6) | 124 (34.2) | 37 (31.6) | 0.18 |
 Maternal smoking during pregnancy | 16 (14.7) | 4 (6.8) | 14 (13.2) | 14 (23.0) | 50 (13.8) | 13 (11.1) | 0.19 |
 Mode of birth |  |  |  |  |  |  | 0.84 |
  Vaginal birth | 71 (65.1) | 37 (62.7) | 65 (61.3) | 41 (67.2) | 248 (68.3) | 75 (64.1) |  |
  C-section | 38 (34.9) | 21 (35.6) | 38 (35.8) | 20 (32.8) | 111 (30.6) | 41 (35.0) |  |
 Prematurity (32–37 weeks) | 17 (15.6) | 12 (20.3) | 15 (14.2) | 12 (19.7) | 60 (16.5) | 22 (18.8) | 0.87 |
 Previous breathing problems before the index hospitalization* | 23 (21.1) | 12 (20.3) | 27 (25.5) | 17 (27.9) | 62 (17.1) | 26 (22.2) | 0.26 |
 History of eczema | 17 (15.6) | 12 (20.3) | 20 (18.9) | 13 (21.3) | 61 (16.8) | 21 (17.9) | 0.92 |
 Ever attended daycare | 23 (21.1) | 17 (28.8) | 33 (31.1) | 15 (24.6) | 75 (20.7) | 27 (23.1) | 0.27 |
 Aeroallergen sensitization†| 0 (0.0) | 1 (1.7) | 2 (1.9) | 0 (0.0) | 7 (1.9) | 2 (1.7) | 0.68 |
 Food sensitization†| 21 (19.3) | 9 (15.3) | 22 (20.8) | 13 (21.3) | 64 (17.6) | 23 (19.7) | 0.92 |
 Children at home | 84 (77.1) | 48 (81.4) | 88 (83.0) | 49 (80.3) | 285 (78.5) | 92 (78.6) | 0.90 |
 Mostly breastfed for the first 3 months of age | 59 (54.1) | 31 (52.5) | 51 (48.1) | 23 (37.7) | 152 (41.9) | 45 (38.5) | 0.21 |
 Smoke exposure at home | 17 (15.6) | 5 (8.5) | 18 (17.0) | 14 (23.0) | 55 (15.2) | 18 (15.4) | 0.42 |
 Antibiotic use before index hospitalization | 29 (26.6) | 30 (50.8) | 44 (41.5) | 27 (44.3) | 96 (26.4) | 28 (23.9) | < 0.001 |
 Corticosteroid use before index hospitalization | 13 (11.9) | 13 (22.0) | 19 (17.9) | 11 (18.0) | 46 (12.7) | 19 (16.2) | 0.31 |
Clinical presentation | |||||||
 Month of hospitalization |  |  |  |  |  |  | 0.06 |
  November | 10 (9.2) | 3 (5.1) | 10 (9.4) | 10 (16.4) | 32 (8.8) | 5 (4.3) |  |
  December | 21 (19.3) | 7 (11.9) | 16 (15.1) | 6 (9.8) | 74 (20.4) | 22 (18.8) |  |
  January | 31 (28.4) | 24 (40.7) | 32 (30.2) | 15 (24.6) | 97 (26.7) | 36 (30.8) |  |
  February | 31 (28.4) | 14 (23.7) | 24 (22.6) | 12 (19.7) | 85 (23.4) | 32 (27.4) |  |
  March | 12 (11.0) | 8 (13.6) | 21 (19.8) | 14 (23.0) | 40 (11.0) | 15 (12.8) |  |
  April | 4 (3.7) | 3 (5.1) | 3 (2.8) | 4 (6.6) | 35 (9.6) | 7 (6.0) |  |
 Breathing problem began < 1 day before the index hospitalization | 5 (4.6) | 2 (3.4) | 8 (7.5) | 3 (4.9) | 20 (5.5) | 10 (8.5) | 0.67 |
 Weight at presentation (kg), median (IQR) | 6 (5–8) | 7 (6–8) | 6 (5–8) | 6 (5–8) | 6 (5–7) | 7 (5–8) | < 0.001 |
 Respiratory rate at presentation (per minute), median (IQR) | 48 (40–59) | 50 (40–60) | 49 (42–60) | 50 (42–64) | 50 (40–60) | 50 (42–60) | 0.26 |
 Oxygen saturation at presentation |  |  |  |  |  | 0.006 | |
  < 90% | 7 (6.4) | 13 (22.0) | 4 (3.8) | 7 (11.5) | 31 (8.5) | 11 (9.4) |  |
  90–93% | 23 (21.1) | 9 (15.3) | 14 (13.2) | 5 (8.2) | 50 (13.8) | 16 (13.7) |  |
  ≥ 94% | 74 (67.9) | 35 (59.3) | 88 (83.0) | 46 (75.4) | 274 (75.5) | 90 (76.9) |  |
 Retractions on examination |  |  |  |  |  |  | 0.32 |
  None | 18 (16.5) | 6 (10.2) | 24 (22.6) | 13 (21.3) | 58 (16.0) | 17 (14.5) |  |
  Mild | 42 (38.5) | 21 (35.6) | 45 (42.5) | 23 (37.7) | 160 (44.1) | 55 (47.0) |  |
  Moderate/severe | 43 (39.4) | 30 (50.8) | 33 (31.1) | 23 (37.7) | 127 (35.0) | 45 (38.5) |  |
 Wheezing on examination | 63 (57.8) | 30 (50.8) | 65 (61.3) | 37 (60.7) | 214 (59.0) | 77 (65.8) | 0.31 |
 Received antibiotics during pre-hospitalization visit | 28 (25.7) | 34 (57.6) | 35 (33.0) | 25 (41.0) | 104 (28.7) | 41 (35.0) | < 0.001 |
 Received corticosteroids during pre-hospitalization visit | 6 (5.5) | 5 (8.5) | 5 (4.7) | 6 (9.8) | 34 (9.4) | 17 (14.5) | 0.15 |
 Virology |  |  |  |  |  |  | 0.11 |
  Sole RSV infection | 56 (51.4) | 30 (50.8) | 69 (65.1) | 34 (55.7) | 225 (62.0) | 60 (51.3) |  |
  Sole rhinovirus infection | 7 (6.4) | 4 (6.8) | 4 (3.8) | 8 (13.1) | 17 (4.7) | 7 (6.0) |  |
  RSV + rhinovirus coinfection | 14 (12.8) | 3 (5.1) | 14 (13.2) | 7 (11.5) | 44 (12.1) | 15 (12.8) |  |
  RSV + non-rhinovirus pathogens | 14 (12.8) | 15 (25.4) | 9 (8.5) | 6 (9.8) | 34 (9.4) | 15 (12.8) |  |
  Rhinovirus + non-RSV pathogens | 2 (1.8) | 2 (3.4) | 3 (2.8) | 2 (3.3) | 9 (2.5) | 5 (4.3) |  |
  Neither RSV nor rhinovirus‡ | 11 (10.1) | 5 (8.5) | 6 (5.7) | 4 (6.6) | 26 (7.2) | 9 (7.7) |  |
  No viral pathogens | 5 (4.6) | 0 (0.0) | 1 (0.9) | 0 (0.0) | 8 (2.2) | 6 (5.1) |  |
 Viral genomic load (CT-value), median IQR | |||||||
  RSV | 22 (20–25) | 22 (21–26) | 22 (21–25) | 23 (21–25) | 23 (21–25) | 22 (21–27) | 0.63 |
  RV | 28 (26–31) | 29 (24–34) | 28 (27–36) | 27 (25–34) | 31 (27–36) | 30 (27–36) | 0.60 |
Outcomes | |||||||
 Intensive care use‡ | 20 (18%) | 16 (27%) | 6 (6%) | 13 (21%) | 47 (13%) | 21 (18%) |  |
 Hospital length of stay ≥ 5 days | 10 (9%) | 19 (32%) | 16 (15%) | 8 (13%) | 47 (13%) | 18 (15%) |  |
 Hospital length of stay (day), median (IQR) | 2 (1–4) | 2 (2–5) | 2 (1–3) | 2 (1–3) | 2 (1–3) | 2 (1–3) |  |