<abstract xmlns="http://www.w3.org/1999/xhtml">We observed the death of insect caterpillars of <italic>Spodoptera exigua</italic> in the laboratory culture line and identified <italic>Serratia marcescens</italic> as the bacterial causative agent of the insect death. We confirmed that <italic>S. marcescens</italic> had insecticidal activity against <italic>S. exigua</italic> and caused high mortality of larvae. The LC50 values of <italic>S. marcescens</italic> CFU per 1 cm2 of insect diet surface were similar for all isolates. Our research reports novel strains with high pesticidal activity as candidates for future research on a new bioinsecticide. As bioinsecticides cannot be harmful to non-target organisms, we determined the pathogenic properties of <italic>S. marcescens</italic> to humans. We proved the ability of <italic>S. marcescens</italic> to damage mammalian epithelial cells. All strains had cytopathic effects to Vero cells with a cytotoxic index ranging from 51.2% ± 3.8% to 79.2% ± 4.1%. We found that all of the strains excreted catecholate siderophore – enterobactin. All isolates were resistant to sulfamethoxazole, tobramycin, gentamicin, cefepime, and aztreonam. We did not observe the ESBL phenotype and the integrons’ integrase genes. Resistance to sulfamethoxazole was due to the presence of the <italic>sul1</italic> or <italic>sul2</italic> gene. The use of resistant <italic>S. marcescens</italic> strains that are pathogenic to humans in plant protection may cause infections difficult to cure and lead to the spread of resistance genes. The results of our study emphasize the necessity of determination of the safety to vertebrates of the bacteria that are proposed to serve as biocontrol agents. The novelty of our study lies in the demonstration of the indispensability of the bacteria verification towards the lack of hazardous properties to humans.</abstract>

We observed the death of insect caterpillars of Spodoptera exigua in the laboratory culture line and identified Serratia marcescens as the bacterial causative agent of the insect death. We confirmed that S. marcescens had insecticidal activity against S. exigua and caused high mortality of larvae. The LC50 values of S. marcescens CFU per 1 cm2 of insect diet surface were similar for all isolates. Our research reports novel strains with high pesticidal activity as candidates for future research on a new bioinsecticide. As bioinsecticides cannot be harmful to non-target organisms, we determined the pathogenic properties of S. marcescens to humans. We proved the ability of S. marcescens to damage mammalian epithelial cells. All strains had cytopathic effects to Vero cells with a cytotoxic index ranging from 51.2% ± 3.8% to 79.2% ± 4.1%. We found that all of the strains excreted catecholate siderophore – enterobactin. All isolates were resistant to sulfamethoxazole, tobramycin, gentamicin, cefepime, and aztreonam. We did not observe the ESBL phenotype and the integrons’ integrase genes. Resistance to sulfamethoxazole was due to the presence of the sul1 or sul2 gene. The use of resistant S. marcescens strains that are pathogenic to humans in plant protection may cause infections difficult to cure and lead to the spread of resistance genes. The results of our study emphasize the necessity of determination of the safety to vertebrates of the bacteria that are proposed to serve as biocontrol agents. The novelty of our study lies in the demonstration of the indispensability of the bacteria verification towards the lack of hazardous properties to humans.

Evaluation of The Pathogenic Potential of Insecticidal <italic>Serratia marcescens</italic> Strains to Humans

Polish Journal of Microbiology

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Evaluation of The Pathogenic Potential of Insecticidal  Strains to Humans

We observed the death of insect caterpillars of Spodoptera exigua in the laboratory culture line and identified Serratia marcescens as the bacterial causative...

Isolate	Antimicrobial resistance profile
MPU Si1	SUL*
MPU Si2	SUL
MPU Si3	SUL
MPU Si4	SUL
MPU Si5	TOB, FEP, SUL
MPU Si6	SUL
MPU Si7	GEN, TOB, SUL
MPU Si8	SUL

Strain	Cytotoxic index (%)
MPU Si1	79.2 ± 4.1*
MPU Si2	77.6 ± 2.8
MPU Si3	77.5 ± 3.1
MPU Si4	58.5 ± 2.5
MPU Si5	76.6 ± 1.9
MPU Si6	78.3 ± 3.7
MPU Si7	59.7 ± 2.1
MPU Si8	54.9 ± 3.8

Strain	LC₅₀ (CFU/cm²)	95% Fiducial limits
MPU Si1	4 × 10⁶	2×10⁶ – 4.3 × 10⁷
MPU Si2	4.2 × 10⁶	2×10⁶ – 1.1 × 10⁸
MPU Si3	5 × 10⁶	2.1×10⁶ – 3.8 × 10⁸
MPU Si4	2 × 10⁶	5.6×10⁵ – 7.6 × 10⁶
MPU Si5	4.5 × 10⁶	9.2×10⁵ – 2.3 × 10⁷
MPU Si6	5.6 × 10⁶	9.2×10⁵ – 3.3 × 10⁷
MPU Si7	7.6 × 10⁵	2×10⁵ – 2.8 × 10⁶
MPU Si8	2.5 × 10⁶	1.3×10⁶ – 2.4 × 10⁷
B. thuringiensis	1.7×10⁷	3.6×10⁶ – 3 × 10⁷

Evaluation of The Pathogenic Potential of Insecticidal Serratia marcescens Strains to Humans

Article Category: short-communication

Publicado en línea: 31 may 2019

Páginas: 185 - 191

Recibido: 27 nov 2018

Aceptado: 19 ene 2019

DOI: https://doi.org/10.33073/pjm-2019-018

Palabras clave
bioinsecticide, insecticidal activity, pathogenicity, pesticide safety,

© 2019 Ayse N. Ceylan et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Antibiotic resistance of S. marcescens strains isolated from insects.

Cytotoxic activity of S. marcescens strains isolated from insects.

Pathogenicity of S. marcescens and B. thuringiensis to S. exigua.

Evaluation of The Pathogenic Potential of Insecticidal Serratia marcescens Strains to Humans

Article Category: short-communication

Publicado en línea: 31 may 2019

Páginas: 185 - 191

Recibido: 27 nov 2018

Aceptado: 19 ene 2019

DOI: https://doi.org/10.33073/pjm-2019-018

Palabras clavebioinsecticide, insecticidal activity, pathogenicity, pesticide safety,

© 2019 Ayse N. Ceylan et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Antibiotic resistance of S. marcescens strains isolated from insects.

Cytotoxic activity of S. marcescens strains isolated from insects.

Pathogenicity of S. marcescens and B. thuringiensis to S. exigua.

Palabras clave
bioinsecticide, insecticidal activity, pathogenicity, pesticide safety,