Dolphin Streptococcus (Streptococcus iniae) Diagnostic Protocol

Streptococcus iniae is a Gram-positive bacterium known for causing diseases in fish and marine mammals, with the potential to infect humans as well. The following diagnostic protocol for Streptococcus iniae is intended to assist veterinarians or laboratory technicians in accurately identifying and diagnosing this pathogen.

I. Clinical Symptom Assessment

Prior to laboratory testing, collect detailed clinical information, including:

1. Host Information: Understand the species, age, health status, and living conditions of the affected animal.
2. Clinical Manifestations: Observe for abnormal behaviors, skin lesions, respiratory distress, appetite reduction, and other symptoms in the animal.
3. Epidemiological Data: Investigate potential outbreaks and possible transmission routes.

II. Sample Collection and Processing

1. Sample Types: Commonly collect samples such as blood, tissues (e.g., liver, spleen), pus, or exudates.
2. Aseptic Technique: Strictly adhere to aseptic procedures during collection to prevent cross-contamination.
3. Sample Preservation: Place samples in appropriate culture media and transport them rapidly to the laboratory under cold chain conditions.

III. Laboratory Testing Methods

A. Bacterial Culture and Identification

1. Selective Agar: Cultivate using selective media containing suitable antibiotics such as nalidixic acid.
2. Incubation Conditions: Incubate in an anaerobic or microaerophilic environment at 37°C for 24 to 48 hours.
3. Morphological Identification: Observe colony characteristics such as size, shape, color, and hemolytic properties.
4. Biochemical Tests: Perform a series of biochemical assays, including catalase tests and sugar fermentation tests, to differentiate among various species within the Streptococcus genus.

B. Molecular Biology Methods

1. PCR Detection: Design specific primers targeting specific gene regions of Streptococcus iniae for polymerase chain reaction (PCR) amplification.
2. Gene Sequencing: Sequence PCR products and compare them with known Streptococcus iniae sequences for confirmation.

C. Serological Testing

1. Antibody Detection: Detect specific antibody levels in the host using ELISA or other serological methods.
2. Antigen Detection: Directly detect bacterial antigens in samples using immunological methods such as immunochromatographic test strips.

IV. Result Interpretation and Reporting

Interpret the laboratory test results in conjunction with clinical symptoms and epidemiological data to make a comprehensive judgment on whether it is an infection by Streptococcus iniae. After confirmation, promptly report to the relevant authorities and take appropriate control measures.

V. Treatment and Prevention Recommendations

1. Antibiotic Therapy: Choose appropriate antibiotics for treatment based on the results of susceptibility tests.
2. Vaccination: Promote effective vaccination programs to enhance host immunity.
3. Environmental Management: Improve breeding environments and sanitary conditions to reduce the risk of pathogen transmission.