| Literature DB >> 30719332 |
Carlos Florindo1,2, Cinthia Alves Barroco1, Inês Silvestre1,2, Vera Damião1,2, João Paulo Gomes2, Barbara Spellerberg3, Ilda Santos-Sanches1, Maria José Borrego2.
Abstract
Extracellular deoxyribonucleases (DNases) contribute to the spread of pathogenic bacteria through the evasion from host innate immunity. Our main objective was to evaluate the production of extracellular DNases by human and bovine Streptococcus agalactiae clinical strains and perform a correlation of genetic lineages and DNase activity with capsular type, genetic determinants, clinical origin (colonization and infection), and host (human or bovine). DNase activity was evaluated by qualitative and quantitative assays for a collection of 406 human (n = 285) and bovine (n = 121) strains. All (121/121) bovine were isolated from mastitis and revealed to be DNase (+), indicating a putative pathogenic role in this clinical scenario. From the human S. agalactiae strains, 86% (245/285) showed DNase activity, among which all strains belonging to capsular types, namely, Ia, Ib, III-2, and IV. All CC17 strains (n = 58) and 56/96 (58.3%) of the CC19 displayed DNase activity. DNase (-) strains belonged to the CC19 group. However, the subcharacterization of CC19 S. agalactiae strains through multiple-locus variable number tandem repeat analysis (MLVA), antibiotic resistance, mobile elements, and surface proteins did not provide any distinction among DNase producers and non-producers. The production of DNases by all human CC17 strains, about two-fifths of human CC19, and all bovine strains, suggest an important contribution of DNases to hypervirulence.Entities:
Keywords: CC17; CC19; DNase activity assays; Streptococcus agalactiae; bovine and human strains; extracellular DNases
Year: 2018 PMID: 30719332 PMCID: PMC6348702 DOI: 10.1556/1886.2018.00026
Source DB: PubMed Journal: Eur J Microbiol Immunol (Bp) ISSN: 2062-509X
Collection of S. agalactiae strains used in the present study
| Capsular serotype/genotype | Number of human colonizing strains (n = 157)[ | Number of human invasive strains (n = 128)[ | Number of bovine strains from 2002–2003 (n = 60)[ | Number of bovine strains from 2011–2013 ( |
|---|---|---|---|---|
| Ia | 20 | 20 | ||
| Ib | 10 | 10 | ||
| II | 39 | 17 | ||
| III-I | 29 | 29 | ||
| III-2 | 29 | 29 | ||
| III-3 | 1 | |||
| IV | 10 | 3 | ||
| V | 20 | 20 | 14 | |
| New cpsBOv[ | 6 | 1 | ||
| New cpsBOV 2 | 11 | |||
| New cpsBOV 3 | 24 | 28 | ||
| New cpsBOV 4 | 1 | |||
| New cpsBOV 5 | 3 | |||
| New cpsBOV 6 | 10 | |||
| New cpsBOV 7 to new cpsBOV 15 | 1 isolate of each type |
These strains were previously described [15–17].
These strains were previously described [18–20].
Bovine strains from 2002–2003 have been previously described [13, 14].
For 13 bovine strains from 2011–2013, the capsular genotype could not be determined. Part of these strains were previously described [13].
New cpsBOV: new bovine capsular type.
Figure 1.Semi-quantitative assay in gel electrophoresis for the evaluation of DNase activity. 1 μg of DNA (amplicon atr) incubated with 10 μl of S. agalactiae culture supernatant (NEM316 vs CC19 clinical strain) for 1h, 2h, 4h, overnight at 37°C. Neg, Negative control: without culture supernatant; ON, Overnight; M, Molecular weight Ladder.
Supporting information Figure 1Standard curve for quantitative DNase assays A standard curve with four solutions of phage Lambda DNA of known concentrations (1, 10, 100 and 1000 ng/ml) was used: y = 3675x (x = concentration of dsDNA ng/ml, y = fluorescence).
Evaluation of the DNase activity by qualitative and semi-quantitative assays among S. agalactiae of human origin (ST = sequence type; CC = clonal complex)
| Strains with DNase activity (frequency) | ||
|---|---|---|
| [STs (frequency)] | ||
| CCs (frequency) | ||
| Capsular type | Colonization | Invasive infection |
| Ia | 100% (20/20) | 100% (20/20) |
| [ST23 (17/20); ST144 (2/20); ST24 (1/20)] | [ST23 (19/20); ST24 (1/20)] | |
| CC23 (20/20) | CC23 (20/20) | |
| Ib | 100% (10/10) | 100% (10/10) |
| [ST8 (5/10); ST12 (2/10); ST1 (1/10); ST10 (1/10); ST563 (1/10)] | [ST10 (5/10); ST8 (4/10); ST12 (1/10)] | |
| CC1 (2/10); CC12 (8/10) | CC12 (10/10) | |
| II | 82% (32/39) | 88% (15/17) |
| [ST 28 (10/32); ST12 (8/32); ST44 (4/32); ST10 (3/32); ST2 (2/32); ST43 (1/32); ST154 (1/32); ST249 (1/32); ST347 (1/32); ST 472 (1/32)] | [ST 12 (5/15); ST28 (4/15); ST19 (3/15); ST10 (1/15); ST22[ | |
| CC19 (17/32); CC12 (12/32); CC1 (2/32); CC23 (1/32) | CC19 (8/15); CC12 (6/15) | |
| III-1 | 48% (14/29) | 59% (17/29) |
| [ST19 (8/14); ST27 (2/14); ST106 (2/14); ST286 (1/14); ST369 (1/14)] | [ST19 (17/29)] | |
| CC19 (14/14) | CC19 (17/17) | |
| III-2 | 100% (29/29) | 100% (29/29) |
| [ST17 (28/29); ST287 (1/29)] | [ST17 (29/29)] | |
| CC17 (29/29) | CC17 (29/29) | |
| IV | 100% (10/10) | 100% (3/3) |
| [ST196 (3/10); ST1 (1/10); ST2 (2/10); ST3 (1/10); ST162 (1/10); ST23 (1/10); ST10 (1/10)] | [ST66 (1/3); ST8 (1/10); ST23 (1/10)] | |
| CC1 (7/10); CC23 (2/10); CC12 (1/10) | CC1 (1/3); CC23 (1/3); CC12 (1/3) | |
| V | 90% (18/20) | 90% (18/20) |
| [ST1 (5/18); ST2 (13/18)] | [ST1 (15/18); ST2 (1/18); ST23 2/18)] | |
| CC1 (18/18) | CC1 (16/18); CC23 (2/18) | |
aSingleton ST.
Evaluation of the DNase activity by qualitative and semi-quantitative assays among S. agalactiae of bovine origin
| Strains with DNase activity (frequency); | ||
|---|---|---|
| [STs (frequency)] CCs (frequency) | ||
| Capsular type | Collection of 2002–2003 | Collection of 2011–2013 |
| III-3 | 100% (1/1) | |
| V | 100% (14/14) | |
| New cpsBOV 1 | 100% (6/6) | 100% (1/1) |
| New cpsBOV 2 | [ST61 (11/11)] CC61 (11/11) | 100% (28/28) |
| New cpsBOV 3 | [ST61 (4/24); ST554 (20/24)] | [ST61 (3/28); ST554 (23/28); ST2 (1/28); ST N.D. (1/28)] CC1 (1/28)] CC61 (26/28) |
| New cpsBOV 4 | 100% (1/1) | |
| New cpsBOV 5 | 100% (3/3) | |
| New cpsBOV 6 | 100% (10/10) | |
| New cpsBOV 7 | 100% (1/1) | |
| New cpsBOV 8 | 100% (1/1) | |
| New cpsBOV 9 | 100% (1/1) | |
| New cpsBOV 10 | 100% (1/1) | |
| New cpsBOV 11 | 100% (1/1) | |
| New cpsBOV 12 | 100% (1/1) | |
| New cpsBOV 13 | 100% (1/1) | |
| New cpsBOV 14 | 100% (1/1) | |
| New cpsBOV 15 | 100% (1/1) | |
ST = Sequence type; CC = Clonal Complex; New cpsBOV = new bovine capsular type; N.D. = not determined.
Figure 2.Quantitative DNase assays displaying differential DNase activity between S. agalactiae strains over time. 1 μg of DNA (amplicon atr) incubated with 10 μl of S. agalactiae culture supernatant for 1h, 2h, 4h, overnight at 37°C. Fluorescent PicoGreen dye (Invitrogen) was used to quantify the dsDNA. The graphic displays the mean values of the experiment performed in duplicate. Error bars show ± standard deviation (see Supporting information Table 1). Col, Colonization; Inf, Infection; Bov, Bovine; C.S., Clinical Strain; R.S., Reference Strain; PC, Positive Control; NC, Negative Control
Standard deviations obtained in quantitative DNase assays
| Strains | Time (hours) | Standard deviation (%) |
|---|---|---|
| 0,09 | ||
| 3,9 | ||
| 0,85 | ||
| 1,4 | ||
| 1,69 | ||
| 0,76 | ||
| 0,56 | ||
| 0,78 | ||
| 0,86 | ||
| 2,77 | ||
| 0,94 | ||
| 0,76 | ||
| 0,38 | ||
| 1,89 | ||
| 1,03 | ||
| 0,8 | ||
| 1,82 | ||
| 0,35 | ||
| 0,58 | ||
| 1,1 | ||
| 0,38 | ||
| 1,89 | ||
| 1,03 | ||
| 0,92 | ||
| 1,61 | ||
| 0,23 | ||
| 1,71 | ||
| 0,55 | ||
| 2,57 | ||
| 1,23 | ||
| 0,9 | ||
| 1,3 | ||
| 5,57 | ||
| 2,16 | ||
| 1,12 | ||
| 0,9 | ||
| 3,1 | ||
| 1,43 | ||
| 0,36 | ||
| 1,01 | ||
| 1,6 | ||
| 2,1 | ||
| 1,95 | ||
| 3,3 | ||
| 2,7 | ||
| 1,89 | ||
| 1,3 | ||
| 1,46 | ||
| 0,72 | ||
| 0,9 | ||
| 0,65 | ||
| 1,1 | ||
| 1,47 | ||
| 0,89 | ||
| 0,26 | ||
| 0,67 | ||
| 0,8 | ||
| 1,2 | ||
| 0,71 | ||
| 0,3 | ||
| 1,2 | ||
| 0,85 | ||
| 0,63 | ||
| 1,32 | ||
| 1,6 | ||
| 1,2 | ||
| 1,08 | ||
| 0,95 | ||
| 1,11 | ||
| 0,98 | ||
| 0,74 | ||
| 0,95 | ||
| 0,35 | ||
| 0,68 | ||
| 1,25 | ||
| 0,8 | ||
| 1,23 | ||
| 0,64 | ||
| 1,09 | ||
| 0,55 |