Dysgalactiae Infection Research Articles

Development of a Lateral Flow Strip-Based Recombinase-Aided Amplification for Active Streptococcus dysgalactiae emerging in channel catfish (Ictalurus punctatus)

Streptococcus dysgalactiae has become an important pathogen affecting mammals and fish (especially farmed fish). The development of a rapid, accurate, and sensitive diagnostic method will aid in the prevention of S. dysgalactiae infection. In this study, a method combining recombinase-aided amplification and a lateral flow dipstick (RAA-LFD) was developed to detect active S. dysgalactiae infection. The RAA-LFD detection was based on the ISP gene of S. dysgalactiae as the target, which could be accomplished with the lowest detection limit of 1.002×102 pg/μL reaction under optimal reaction conditions of 39 °C for 15 min. RAA-LFD and conventional PCR were used to detect 50 experimental samples invaded by S. dysgalactiae disease materials. The results showed that the positive concordance rate of the two methods was 97.6%, the negative concordance rate was 90.0%, and the total concordance rate was 98.0%. Compared with conventional PCR, the Area Under the ROC Curve (AUC) of RAA-LFD was 0.950, and the sensitivity and specificity were 100% and 90%, respectively. The RAA-LFD of S. dysgalactiae infection is convenient for rapid clinical detection.

Identification and Characterization of a Novel Prophage Lysin against Streptococcus dysgalactiae.

Streptococcus dysgalactiae infection can cause bovine mastitis and lead to huge economic losses for the dairy industry. The abuse of antibiotics has resulted in growing drug resistance of S. dysgalactiae, which causes hard-to-treat infections. Bacteriophage lysin, as a novel antibacterial agent, has great potential for application against drug-resistant gram-positive bacteria. However, few studies have been conducted on the prophage lysin of S. dysgalactiae. In this study, we mined a novel prophage lysin, named Lys1644, from a clinical S. dysgalactiae isolate by genome sequencing and bioinformatic analysis. Lys1644 was expressed and purified, and the lytic activity, antibacterial spectrum, optimal pH and temperature, lytic activity in milk in vitro, and synergistic bacteriostasis with antibiotics were assessed. The Lys1644 prophage lysin showed high bacteriolysis activity specifically on S. dysgalactiae, which resulted in CFU 100-fold reduction in milk. Moreover, Lys1644 maintained high activity over a wide pH range (pH 5-10) and a wide temperature range (4-42 °C). Synergistic bacteriostatic experiments showed that the combination of low-dose Lys1644 (50 μg/mL) with a subinhibitory concentration of aminoglycoside antibiotics (kanamycin or spectinomycin) can completely inhibit bacterial growth, suggesting that the combination of Lys1644 and antibiotics could be an effective therapeutic strategy against S. dysgalactiae infection.

Outbreak of large skin wounds and necrotising soft tissue infection in Iberian pigs affected by Streptococcus dysgalactiae subspecies equisimilis

AbstractStreptococcus dysgalactiae subspecies equisimilis is an emerging pathogen in animals and humans. Herein, we describe an outbreak of S. dysgalactiae subspecies equisimilis infection in Iberian pigs with large skin ulcerations and necrotising soft tissue. Postmortem examination was performed on two animals that had larger chronic lesions and secondary myiasis. Swabs from the edges of wounds from animals with more acute injuries were collected. The β‐haemolytic colonies obtained from the skin wounds and lymph nodes were identified as S. dysgalactiae subspecies equisimilis. The isolate had low minimum inhibitory concentrations for β‐lactams. Stress due to the change of groups and the consequent increase in fights for the establishment of a new hierarchical order could be the reason why pigs that carry the bacteria in their gingival mucosa transmit them to other individuals through bites. This stressful situation could cause a certain immunosuppression, potentially favouring the exacerbation of S. dysgalactiae subspecies equisimilis and the development of the lesions observed.

Streptococcus dysgalactiae subsp. dysgalactiae presents with progressive weakness in limbs: a case report and literature review

BackgroundStreptococcus dysgalactiae subsp. dysgalactiae has been identified as an animal pathogen that is thought to occur only in animal populations. Between 2009 and 2022, humans infected with SDSD were reported rarely. There is a lack of details on the natural history, clinical features, and management of disease caused by this pathogen. This case outlines a human SDSD with muscle aches and progressive loss of muscle strength leading to immobility and multi-organ dysfunction syndrome.Case presentationShe presented with muscle pain and weakness, and later developed a sore throat, headache and fever with a maximum temperature of 40.5 °C. The muscle strength of the extremities gradually decreased to grade 1 and the patient was unable to move on his own. Next-generation blood sequencing and multi-culture confirmed the presence of Streptococcus dysgalactiae and Streptococcus dysgalactiae subsp. Dysgalactiae, respectively. A Sequential Organ Failure Assessment score of 6 indicated septicemia, and therapeutic antibiotics were prescribed empirically. After 19 days of inpatient treatment, the patient's condition greatly improved and completely recovered within a month.ConclusionSymptoms of Streptococcus dysgalactiae subsp. dysgalactiae presenting with progressive limb weakness resemble polymyositis, so a precise differential diagnosis is essential. Multidisciplinary consultation is helpful when polymyositis cannot be ruled out and facilitates the choice of an optimal treatment protocol. In the context of this case, penicillin is an effective antibiotic for Streptococcus dysgalactiae subsp. dysgalactiae infection.

P-020 The validation of a PCR method for Streptococcus dysgalactiae infection in sheep and its application for on-farm disease transmission studies

P-020 The validation of a PCR method for Streptococcus dysgalactiae infection in sheep and its application for on-farm disease transmission studies

Recurrent Streptococcus dysgalactiae subspecies dysgalactiae infection in a 92-year-old inpatient: a case report and review of literature

Recurrent Streptococcus dysgalactiae subspecies dysgalactiae infection in a 92-year-old inpatient: a case report and review of literature

Molecular characterization of the evolutionary conserved signaling intermediate in Toll pathways (ECSIT) of soiny mullet (Liza haematocheila)

Mammalian evolutionary conserved signaling intermediate in Toll pathways (ECSIT) is an important intracellular protein that involves in innate immunity, embryogenesis, and assembly or stability of the mitochondrial complex I. In the present study, the ECSIT was characterized in soiny mullet (Liza haematocheila). The full-length cDNA of mullet ECSIT was 1860 bp, encoding 449 amino acids. Mullet ECSIT shared 60.4%∼78.2% sequence identities with its teleost counterparts. Two conserved protein domains, ECSIT domain and C-terminal domain, were found in mullet ECSIT. Realtime qPCR analysis revealed that mullet ECSIT was distributed in all examined tissues with high expressions in spleen, head kidney (HK) and gill. Further analysis showed that mullet ECSIT in spleen was up-regulated from 6 h to 48 h after Streptococcus dysgalactiae infection. In addition, the co-immunoprecipitation (co-IP) assay confirmed that mullet ECSIT could interact with tumor necrosis factor receptor-associated factor 6 (TRAF6). Molecular docking revealed that the polar interaction and hydrophobic interaction play crucial roles in the forming of ECSIT-TRAF6 complex. The resides of mullet ECSIT that involved in the interaction between ECSIT and TRAF6 were Arg107, Glu113, Phe114, Glu124, Lys120 and Lys121, which mainly located in the ECSIT domain. Our results demonstrated that mullet ECSIT involved in the immune defense against bacterial and regulation of TLRs signaling pathway by interaction with TRAF6. To the best of our knowledge, this is the first report on ECSIT of soiny mullet, which deepen the understanding of ECSIT and its functions in the immune response of teleosts.

A recombinant fungal defensin-like peptide-P2 combats Streptococcus dysgalactiae and biofilms.

Streptococcus dysgalactiae, considered one of the main pathogens that causes bovine mastitis, is a serious threat to humans and animals. However, the excessive use of antibiotics and the characteristic of S. dysgalactiae forming biofilms in mastitic teat canal have serious clinical implications. In this study, in vivo and in vitro multiple mechanisms of action of P2, a mutant of fungal defensin plectasin, against S. dysgalactiae were systematically and comprehensively investigated for the first time. P2 showed potent antibacterial activity against S. dysgalactiae (minimum inhibitory concentration, MIC = 0.23-0.46 μM) and rapid bactericidal action by 3.0 lg units reduction in 2-4 h. No resistant mutants appeared after 30-d serial passage of S. dysgalactiae in the presence of P2. The results of electron microscopy and flow cytometer showed that P2 induced membrane damage of S. dysgalactiae, causing the leakage of cellular content and eventually cell death. Besides, P2 effectively inhibited early biofilm formation, eradicated mature biofilms, and killed 99.9% persisters which were resistant to 100 × MIC vancomycin; and confocal laser scanning microscopy (CLSM) also revealed the potent antibacterial and antibiofilm activity of P2 (the thickness of biofilm reduced from 18.82 to 7.94 μm). The in vivo therapeutic effect of P2 in mouse mastitis model showed that it decreased the number of mammary bacteria and alleviated breast inflammation by regulating cytokines and inhibiting bacterial proliferation, which were superior to vancomycin. These data indicated that P2 maybe a potential candidate peptide for mastitis treatment of S. dysgalactiae infections. KEY POINTS: •P2 showed potential in vitro antibacterial characteristics towards S. dysgalactiae. •P2 eradicated biofilms, killed persisters, and induced cell death of S. dysgalactiae. •P2 could effectively protect mice from S. dysgalactiae infection in gland.

In-hospital mortality among patients with invasive non-group A β-hemolytic Streptococcus treated with clindamycin combination therapy: a nationwide cohort study.

AimCombination treatment with clindamycin is recommended in patients with invasive group A Streptococcus infection; however, whether the same treatment is effective in invasive group B Streptococcus and S. dysgalactiae subspecies equisimilis infections remains unknown. We aimed to investigate whether clindamycin added to standard of care therapy would be effective in patients with invasive non‐group A β‐hemolytic Streptococcus infections.MethodsThis was a nationwide retrospective cohort study using the Japanese Diagnosis Procedure Combination inpatient database focusing on the period between 2010 and 2018. We extracted data on patients diagnosed with sepsis due to non‐group A β‐hemolytic Streptococcus. One‐to‐four propensity score‐matching was undertaken to compare patients who were treated with clindamycin within 2 days of admission (clindamycin group) and those who did not (control group). The primary outcome was in‐hospital mortality.ResultsWe identified 3754 eligible patients during the study period. The patients were divided into the clindamycin (n = 296) and control groups (n = 3458). After one‐to‐four propensity score matching, we compared 289 and 1156 patients with and without clindamycin, respectively. In‐hospital mortality did not significantly differ between the two groups (9.7% versus 10.3%; risk difference 0.3%; 95% confidence interval, –3.5% to 4.2%).ConclusionsThis nationwide database study showed that combination therapy involving the use of clindamycin was not associated with lower in‐hospital mortality in patients with invasive non‐group A β‐hemolytic Streptococcus.

Immunogenicity of multi-epitope vaccines composed of epitopes from Streptococcus dysgalactiae GapC

Glyceraldehyde-3-phosphate dehydrogenase C (GapC) of Streptococcus dysgalactiae (S. dysgalactiae) is a highly conserved surface protein that can induce a protective immune response against S. dysgalactiae infection. To investigate the immune response and protective efficacy induced by epitope-vaccines against S. dysgalactiae infection, we constructed epitope-vaccines GTB1, GB1B2, and GTB1B2 using a T cell epitope (GapC63-77, abbreviated as GT) and two B cell epitopes (GapC30-36, abbreviated as GB1, and GapC97-103, abbreviated as GB2), which were identified in GapC1-150 of S. dysgalactiae in tandem by a GSGSGS linker. BALB/c mice were immunized via an intramuscular injection with the epitope vaccines. The levels of the cytokines, IFN-γ, IL-4, and IL-17, secreted by splenic lymphocytes and the antibody levels in the sera of the immunized mice were detected by ELISA. The immunized mice were subsequently challenged with S. dysgalactiae, and the bacterial colonization in the immunized-mouse organs was examined using the plate counting method. The results showed that the level of the cytokines induced by GTB1B2 was lower than that induced by GapC1-150, but higher than that induced by other epitope vaccines. The level of IgG induced by GTB1B2 was lower than that induced by GapC1-150, but higher than the levels induced by other epitope vaccines. The bacterial colonization numbers in the organs of the mice immunized with GTB1B2 were higher those of the mice immunized with GapC1-150, but significantly lower than those from the mice immunized with other epitope-vaccines. Our results demonstrated that the T cell and B cell epitopes in the epitope-vaccines worked synergistically against bacterial challenge. The multi-epitope vaccine, GTB1B2, could induce stronger cellular and humoral immune responses, and provide a better protective effect against S. dysgalactiae infection.

Streptococcus dysgalactiae—Contagious or Environmental?

Simple SummaryThe usual routes of transmission of Streptococcus dysgalactiae in the development of bovine mastitis are unclear. For the control of mastitis in dairy practice, improved knowledge about the transmission of this pathogen would be very helpful. The variety of strain within a herd can be used to describe its transmission behavior. Isolates of Strep. dysgalactiae were collected from clinical mastitis samples on different farms, and the strains were typed using a molecular method. Overall, we performed strain typing on isolates from 16 farms in Germany and found signs of the contagious transmission of Strep. dysgalactiae on all the farms. We observed a variety of outcomes, from a single strain in all six Strep. dysgalactiae cases recorded on one farm, to five strains in six cases recorded on another farm.Streptococcus dysgalactiae is among the most important pathogens causing bovine mastitis. Unfortunately, there is presently a lack of clear knowledge about the mode of transmission—contagious or environmental—of this pathogen. To obtain more information on this, knowledge of the genetic diversity of the isolated microorganisms at the farm level can be useful. To observe the strain variety in different herds of cattle, isolates of Strep. dysgalactiae were collected from clinical mastitis samples at different farms, and the strains were typed using the pulsed-field gel electrophoresis (PFGE) method. Overall, we performed strain typing on 93 isolates from 16 farms in Germany and used an index to describe the degree of contagiosity of Strep. dysgalactiae at each farm. This index (CI) represents the number of isolates divided by the number of strains found in mastitis milk of clinical cases within a period of 14 months. The results differed between the farms. In one farm, all six Strep. dysgalactiae cases that occurred during the study period were caused by a single strain (CI = 6), while in another farm the six cases that occurred were caused by five different strains (CI = 1.2). All other farms fell between these two extremes. This indicates that Strep. dysgalactiae infections can occur via several routes of transmission. At the farm level, strain comparisons are necessary to determine the routes of transmission. Two strains were able to survive on the farm for a minimum of 14 months.

Group C Streptococcus dysgalactiae infection in fish.

Streptococcus dysgalactiae subsp. dysgalactiae (GCSD) is a Gram-positive, facultative anaerobic bacterium and mostly non-β-haemolytic with Lancefield group C antigen. GCSD infection has been identified in various vertebrates. From 2002 to the present, GCSD infection of fish has been reported to cause severe economic losses in aquaculture farms around the world. Moreover, GCSD isolates from teleosts have been identified in patients with ascending upper limb cellulitis. Therefore, the economic and clinical significance of GCSD has increased in aquaculture, livestock and human health. Many studies have been presented, from the first report of isolated GCSD in fish, to the pathogenesis, characterization, immune responses and vaccine development. In this review, we present the current knowledge of GCSD in teleosts.

TLR13, TLR22, TRAF6, and TAK1 in the soiny mullet (Liza haematocheila): Molecular characterization and expression profiling analysis

Toll-like receptors (TLRs) and their associated signaling pathways play pivotal roles in the immune response to invading pathogens. Here, TLR13, TLR22, tumor necrosis factor receptor-associated factor 6 (TRAF6), and transforming growth factor-β-activated kinase1 (TAK1) were characterized in the soiny mullet (Liza haematocheila), representative mugilid species that is widely cultured in Asia. The four mullet genes, which shared characteristic features with their counterparts in other teleosts, were ubiquitously expressed in all of the examined tissues, albeit with different expression patterns. Following Streptococcus dysgalactiae infection, the four genes were upregulated to different degrees in various mullet tissues. These results indicated that the four genes were involved in the mullet immune response to bacterial infection. To the best of our knowledge, this is the first characterization of these four genes in mullet. Our results provide a basis for future studies of TLR signaling pathways in mullet, as well as for similar studies in other mugilids.

Short communication: Recombinant mammary serum amyloid A3 as a potential strategy for preventing intramammary infections in dairy cows at dryoff

Mammary serum amyloid A3 (M-SAA3) has shown potential in stimulating innate immunity during intramammary infections, at calving and at dryoff. In this study, we produced recombinant caprine M-SAA3 to test its ability to reduce intramammary infections with Staphylococcus aureus, Streptococcus uberis, Streptococcus dysgalactiae, and Escherichia coli, which are all common mastitis-producing pathogens. Recombinant production of M-SAA3 (followed by lipopolysaccharide removal to avoid lipopolysaccharide-nonspecific stimulation of the immune system) was successfully achieved. Mammary serum amyloid A3 stimulated the expression of IL-8 in a dose-dependent manner in primary mammary cultures. Although a direct killing effect on Staph. aureus by M-SAA3 was not detected, this acute phase protein was able to reduce Staph. aureus, Strep. uberis, and Strep. dysgalactiae infections by up to 50% and induced a reduction in E. coli counts of 67%. In general, the best concentration of caprine M-SAA3 for inhibiting infections was the lowest concentration tested (10 μg/mL), although higher concentrations (up to 160 μg/mL) increased its antimicrobial potential against some pathogens.

α-Enolase as a novel vaccine candidate against Streptococcus dysgalactiae infection in cobia (Rachycentron canadum L.)

Streptococcus dysgalactiae is an important pathogenic bacterium that has caused economic loss for the cobia industry in Taiwan, ROC. This study presents a highly effective subunit vaccine composed of a moonlight protein, α-enolase, for the prevention of S. dysgalactiae infection. First, α-enolase was cloned, transformed, and expressed in E. coli for production of recombinant protein. Then, the protective efficacies of α-enolase recombinant protein were evaluated in combination with either a pro-inflammatory cytokine, TNF-α, or an oil adjuvant, ISA 763 AVG. The results showed that the combination of α-enolase and ISA 763 AVG was highly protective (RPS = 88.89%), while a negative effect was found in the group immunised with α-enolase adjuvanted with TNF-α (RPS = 22.22%). A further study was conducted with double dose of ISA 763 AVG, which led to an increased RPS value of 97.37%. Moreover, immunised cobia exhibited significantly greater lysozyme activity, antibody responses, and expression of certain immune-related genes post-challenge. Altogether, our results demonstrated that a combination of α-enolase recombinant protein with ISA 763 AVG adjuvant is a promising vaccine that can be employed for protection of cobia against S. dysgalactiae infection.

Differential expression of immune-related genes in head kidney and spleen of cobia (Rachycentron canadum) having Streptococcus dysgalactiae infection

Streptococcus dysgalactiae is a gram-positive bacterium and a harmful aquaculture pathogen. To investigate the immune response against S. dysgalactiae, we performed transcriptome analysis of the head kidney and spleen of cobia (Rachycentron canadum) using RNA-seq. Total RNA was extracted from the head kidney and spleen of cobia, 1 and 2 days after treatment with S. dysgalactiae or control PBS. After RNA purification and cDNA library generation, sequencing was performed using the Illumina HiSeq™ 4000 platform. The filtering and de novo assembling transcripts were annotated using several databases. To identify differentially expressed genes (DEGs) between the S. dysgalactiae and PBS groups, the mapped values of fragments per kilobase of transcripts per million fragments were calculated. After de novo assembly, a total of 106,984 transcripts were detected, with an N50 of 3020 bp. These transcripts were annotated and categorised into a total of 7608 genes based on the KEGG pathway database. DEGs (2-fold difference) were calculated by comparing the S. dysgalactiae and PBS control group gene expression levels at each time point. The DEGs were mainly annotated into signal transduction and immune system categories, based on the KEGG database. The DEGs were significantly enriched in the immune-related pathways – “cytokine-cytokine receptor interaction”, “complement and coagulation cascades”, and “hematopoietic cell linage”. In this study, immune-related genes responding to S. dysgalactiae were detected, and several immune system pathways were categorized. We identified the IL17C-related pathway for inducing the expression of pro-inflammatory cytokine genes (IL-1β, IL-6, and IFNγ). Additionally, neutrophil-related genes (CSF3, CD121, and CD114) were induced in the spleen after S. dysgalactiae infection. It was suggested that these pathways contribute to immune responses against S. dysgalactiae infection. The data revealed in this study may offer improved strategies against S. dysgalactiae infection in cobia.

Direct cytotoxic activity of CD8+ T cells against Ichthyophthirius multifiliis in ginbuna crucian carp, Carassius auratus langsdorfii

The suppressor of cytokine signaling (SOCS) family members play crucial roles in regulating immune signal pathways by acting as inhibitors of cytokine receptor signaling. In this study, 10 SOCS genes were identified in soiny mullet (Liza haematocheila), an economically important aquaculture mugilid species in China and other Asian countries. Sequence comparison showed that the sequence identity between mullet SOCSs and their counterparts from other vertebrates ranged from 38.2% to 92.5%. All mullet SOCS genes were constitutively expressed in tissues examined, but their expression patterns were different. Further, following Streptococcus dysgalactiae infection, all mullet SOCS genes exhibited distinct expression patterns in tissues. These results suggest that SOCSs are involved in immune response to bacterial infection and provide the basis for understanding the complex cytokine regulatory network of teleosts.

Identification and expression analysis of suppressors of cytokine signaling (SOCS) from soiny mullet (Liza haematocheila)

The suppressor of cytokine signaling (SOCS) family members play crucial roles in regulating immune signal pathways by acting as inhibitors of cytokine receptor signaling. In this study, 10 SOCS genes were identified in soiny mullet (Liza haematocheila), an economically important aquaculture mugilid species in China and other Asian countries. Sequence comparison showed that the sequence identity between mullet SOCSs and their counterparts from other vertebrates ranged from 38.2% to 92.5%. All mullet SOCS genes were constitutively expressed in tissues examined, but their expression patterns were different. Further, following Streptococcus dysgalactiae infection, all mullet SOCS genes exhibited distinct expression patterns in tissues. These results suggest that SOCSs are involved in immune response to bacterial infection and provide the basis for understanding the complex cytokine regulatory network of teleosts.

Subacute Lethal Bilateral Leg Time-Lag Infection by Streptococcus dysgalactiae

A 66-year-old man felt left leg pain 7 days prior to admission to our hospital. His history included diabetes mellitus, hypertension, alcoholic live disease and chronic renal failure without hemodialysis. He drank 90 g of ethanol per day. As the pain gradually became exacerbated, he visited a local clinic on foot. The chemical laboratory analysis showed thrombocytopenia, so he was admitted to our department. On arrival, his consciousness was clear, and he had stable vital signs. He had bilateral lichen legs, and the left leg showed swelling, tenderness and redness. Computed tomography revealed a high-density area of soft tissue in the left leg. The patient was treated with meropenem and linezolid. On the second hospital day, he felt improvement of pain in his left leg, but began to feel pain in his right leg. He had oligouria. The same day, his blood pressure and respiratory function deteriorated, and both legs became red with purpura. He died on the third hospital day. Streptococcus dysgalactiae was detected in the blood and skin of his left leg cultures. We herein report a unique case of invasive Streptococcus dysgalactiae infection. Elderly patients with underlying diseases, who might have a soft tissue infection, may require early aggressive debridement of the infected tissue, in addition to performing prophylactic decontaminated measurements of the uninfected area.

Disease outbreaks in farmed Amazon catfish (Leiarius marmoratus x Pseudoplatystoma corruscans) caused by Streptococcus agalactiae, S. iniae, and S. dysgalactiae

The Amazon catfish is one of the main farm-raised native fish in Brazil. In spite of its importance, the main health-associated issues have been poorly characterized in these fish. In this study, we describe outbreaks of S. agalactiae, S. iniae, and S. dysgalactiae in Amazon catfish farms in detail. The genetic diversity and antibiotic resistance patterns of different isolates were also evaluated. Thirty-five diseased fish were sampled from four commercial farms, and were subjected to bacteriological examinations. The isolates were genotyped by REP-PCR, and antimicrobial susceptibility of six antibiotics was evaluated using the disc diffusion assay. Fifteen Streptococcus spp. isolates were identified (S. agalactiae = 10 strains; S. dysgalactiae = 1; S. iniae = 4), which were further confirmed by MALDI-TOF. S. agalactiae and S. dysgalactiae infections were successfully achieved under experimental conditions, which confirmed Koch's postulates. Three distinct genetic patterns were verified by REP-PCR for S. agalactiae; S. iniae isolates were indistinguishable by this technique. In antimicrobial susceptibility tests, all S. agalactiae isolates were classified as wild-types to erythromycin (ERY); S. agalactiae strains, non-wild-types to amoxicillin (n = 2 isolates), florfenicol (n = 4), norfloxacin (n = 2), oxytetracycline (n = 3) (OXY), and trimethoprim-sulfamethoxazole (n = 6) (SXT); S. dysgalactiae strain, non-wild-type to OXY and ERY; and S. iniae isolates, non-wild-types to both SXT (n = 1) and OXY (n = 3). This study represents the first description of Streptococcus iniae, S. dysgalactiae, and S. agalactiae serotype II infections in farm-raised Amazon catfish. In addition, it is the first study that describes OXY resistant S. agalactiae isolates from farmed native fish in Brazil.