Analysis of Clinical Characteristics and Antimicrobial Resistance in 249 Isolates of Streptococcus mitis: a Single-Centre Study

Fig. 1.

Trends in detection rate of Streptococcus mitis from 2020 to 2024_

Year	Annual patients volume	Cases	Rate (‱)
2020	65,378	16	2.45
2021	67,020	17	2.54
2022	70,952	36	5.10
2023	78,830	66	8.37
2024	82,557	114	13.81
Total	364,737	249	6.83

Specimen sources of Streptococcus mitis isolates during 2020–2024_

Specimen source	Isolates (n = 249)	Rate (%)
Skin and soft tissue secretion	58	23.30
bronchoalveolar lavage fluid	58	23.30
Urine	51	20.48
Blood	44	17.67
Punctate fluid	14	5.62
Pus	8	3.21
Bile	6	2.41
Pleural effusion	5	2.01
Ascites	5	2.01

Resistance rates of Streptococcus mitis to antimicrobial agents during 2020–2024_

Antimicrobial agents	2020 (n = 16)	2021 (n = 17)	2022 (n = 36)	2023 (n = 66)	2024 (n = 114)	χ2	p
	R (%)	R (%)	R (%)	R (%)	R (%)
Cefepime	43.75	17.65	11.11	12.12	6.14	10.644	0.001
Ceftriaxone	25.00	29.41	22.22	22.72	6.14	7.399	0.007
Erythromycin	68.75	88.23	83.33	71.21	37.72	6.586	0.010
Clindamycin	50.00	100.00	63.88	48.48	28.95	8.514	0.004
Levofloxacin	50.00	52.94	30.55	42.42	19.30	5.564	0.018
Linezolid	0	0	0	0	0	–	–
Vancomycin	0	0	0	0	0	–	–
Penicillin G	55.55	41.17	72.22	46.96	24.56	6.608	0.010

Resistance rates of Streptococcus mitis to antimicrobial agents in different age groups_

Antimicrobial agents Age	≤ 20	21~40	41~60	61~80	≥ 81
Cefepime	0	1	8	16	4
Ceftriaxone	4	5	10	15	5
Erythromycin	13	20	48	73	5
Clindamycin	9	18	39	44	3
Levofloxacin	2	11	26	36	3
Linezolid	0	0	0	0	0
Vancomycin	0	0	0	0	0
Penicillin G	10	16	31	39	5

Specimen sources of Streptococcus mitis isolates in different ages groups_

Specimen source	≤ 20	21~40	41~60	61~80	≥ 81
Skin and soft tissue secretion	14	10	10	23	1
bronchoalveolar lavage fluid	24	3	13	17	1
Urine	10	4	16	19	2
Blood	9	3	16	16	0
Punctate fluid	5	1	2	5	1
Pus	1	2	3	2	0
Bile	1	3	2	0	0
Pleural effusion	1	0	3	1	0
Ascites	0	1	3	1	0

Clinical characteristics of patients with Streptococcus mitis infection from 2020 to 2024_

Clinical characteristics	Parameters	Cases	Rate (%)
Sex	Male	147	59.04
	Female	102	40.96
Age in years	≤ 20	65	26.10
	21~40	27	10.84
	41~60	68	27.31
	61~80	84	33.74
	≥ 81	5	2.01
Type of infection	HAI	21	8.43
	CAI	112	44.98
	Colonization	116	46.59
Department	Pediatrics	55	22.09
	Urinary	49	19.68
	Stomatology	29	11.65
	ICU	18	7.23
	Radiation	15	6.02
	Respiratory medicine	10	4.02
	Orthopedics	10	4.02
	General surgery	9	3.61
	Endocrine	8	3.21
	Cardiothoracic surgery	8	3.21
	Gastroenterology	9	3.61
	Neonatology	5	2.01
	Hematology	5	2.01
	Others	18	7.23

Analysis of different infection types and patient age, specimen source, and antimicrobial resistance_

Characteristics	Infection type	HAI (21)	CAI (112)	Colonization (116)
	Parameters	Cases/%	Cases/%	Cases/%
Ages	≤ 20	2/9.52	30/26.79	33/28.44
	21~40	2/9.52	10/8.93	15/12.93
	41~60	6/28.58	35/31.25	27/23.28
	61~80	9/42.86	36/32.14	39/33.62
	≥ 81	2/9.52	1/0.89	2/1.72
Source	Skin and soft tissue	4/19.05	18/16.70	36/31.03
	Secretion bronchoalveolar lavage fluid	1/4.76	25/22.3	32/27.59
	Urine	4/19.05	14/12.5	33/28.44
	Blood	10/47.62	34/30.35	0
	Punctate fluid	0	6/5.36	8/6.90
	Pus	1/4.76	4/3.57	3/2.59
	Bile	0	2/1.79	4/3.45
	Pleural effusion	0	5/4.46	0
	Ascites	1/4.76	4/3.57	0
Resistance	Cefepime	5/23.81	11/9.82	13/11.21
	Ceftriaxone	11/52.38	13/11.61	15/12.93
	Erythromycin	18/85.71	48/42.86	93/80.17
	Clindamycin	15/71.43	43/38.40	55/47.41
	Levofloxacin	10/47.62	30/26.79	38/32.76
	Linezolid	0	0	0
	Vancomycin	0	0	0
	Penicillin G	19/90.48	40/35.71	42/36.21