In vitro susceptibility of spiroplasmas to heavy-metal salts
Abstract:
The susceptibility of six spiroplasma strains to heavy-metal salt was characterized in terms of minimal inhibitory concentrations and minimal biocidal concentrations in broth tube dilution tests. The strains were most susceptible to mercuric chloride and silver nitrate; less susceptible to copper sulfate, cobalt chloride, lead nitrate, and cadmium sulfate; and least susceptible to nickel chloride and zinc sulfate. Spiroplasma citri strains Maroc R8A2 and C189 were the most susceptible to five of eight heavy-metal salts, and honeybee spiroplasma strain AS576 and Spiroplasma floricola strain 23-6 were generally the least susceptible. The difference between the minimal biocidal concentrations and the minimal inhibitory concentrations was greater for certain heavy-metal salts than for others.
Insights
This study assessed heavy-metal salt susceptibility in six spiroplasma strains. Results show varying resistance, with mercuric chloride and silver nitrate being most effective against these bacteria.
Area of Science:
- Microbiology
- Environmental Science
- Toxicology
Background:
- Spiroplasma are wall-less bacteria with diverse hosts and ecological roles.
- Heavy metals are environmental contaminants with known antimicrobial properties.
- Understanding spiroplasma susceptibility to heavy metals is crucial for controlling infections and managing environmental impact.
Purpose of the Study:
- To determine the susceptibility of six spiroplasma strains to various heavy-metal salts.
- To identify specific heavy-metal salts with inhibitory and biocidal effects on spiroplasma.
- To compare the susceptibility profiles across different spiroplasma species and strains.
Main Methods:
- Broth tube dilution tests were employed to determine minimal inhibitory concentrations (MICs) and minimal biocidal concentrations (MBCs).
- Six spiroplasma strains, including Spiroplasma citri, honeybee spiroplasma, and Spiroplasma floricola, were tested against eight different heavy-metal salts.
- Data analysis focused on comparing MICs and MBCs to establish susceptibility patterns.
Main Results:
- Spiroplasma strains exhibited differential susceptibility to heavy-metal salts.
- Mercuric chloride and silver nitrate demonstrated the highest antimicrobial activity.
- Nickel chloride and zinc sulfate showed the least efficacy, while copper sulfate, cobalt chloride, lead nitrate, and cadmium sulfate exhibited intermediate effects.
- Spiroplasma citri strains (Maroc R8A2, C189) were generally more susceptible than honeybee spiroplasma (AS576) and Spiroplasma floricola (23-6).
- The difference between MICs and MBCs varied depending on the heavy-metal salt, indicating concentration-dependent effects.
Conclusions:
- Heavy-metal salts display varying degrees of efficacy against spiroplasma, with HgCl2 and AgNO3 being potent inhibitors and biocides.
- Specific spiroplasma strains exhibit distinct susceptibility profiles, suggesting strain-specific resistance mechanisms.
- The findings provide valuable data for potential antimicrobial applications and understanding heavy-metal toxicity in spiroplasma.
