Physical activity reduces intradermal bacterial load in a murine model submitted to forced swim training – a pilot study

Regular exercise is beneficial to health. This study evaluated the effects of moderate and intense physical exercise modalities on intradermal infection by Staphylococcus aureus in a murine model. Mice that practiced moderate exercise had lower bacterial load on lymph nodes and less inflammatory infiltrate in dermis. They presented greater weight, however, less amount of epididymal fat: the weight was increased while they had fat diminished. A positive correlation was observed between lipid content and bacterial load in mice trained at moderate intensity. Animals that were under high intensity exercises presented superior bacterial load on the lymph nodes, increased neutrophil count and circulating lymphocytes, and had leukocyte recruitment to the dermis augmented, when compared to the ones in moderate exercise. These findings suggest that moderate physical activity modulates the immune response in dermal infection caused by S. aureus in a murine model.

Key words
infection; mice; physical exercise; Staphylococcus aureus

Authorship

MARIA P.L. GALANTINI

Universidade Federal da Bahia (UFBA), Instituto Multidisciplinar em Saúde (IMS), Campus Anísio Teixeira (CAT), Rua Hormindo Barros, 58, 45029-094 Vitória da Conquista, BA, BrazilUniversidade Federal da Bahia (UFBA)BrazilVitória da Conquista, BA, BrazilUniversidade Federal da Bahia (UFBA), Instituto Multidisciplinar em Saúde (IMS), Campus Anísio Teixeira (CAT), Rua Hormindo Barros, 58, 45029-094 Vitória da Conquista, BA, Brazil

https://orcid.org/0000-0001-9423-5334

LORENA S. LEAL

https://orcid.org/0000-0003-0059-9378

KARINE B. RODRIGUES

https://orcid.org/0000-0003-1465-5895

ISRAEL S. RIBEIRO

https://orcid.org/0000-0002-1262-1387

ITALO S. PEREIRA

Universidade de São Paulo (USP), Faculdade de Medicina de Ribeirão Preto (FMRP), Departamento de Bioquímica e Imunologia, Avenida Bandeirantes, 3900, 14049-900 Ribeirão Preto, SP, BrazilUniversidade de São Paulo (USP)BrazilRibeirão Preto, SP, Brazil Universidade de São Paulo (USP), Faculdade de Medicina de Ribeirão Preto (FMRP), Departamento de Bioquímica e Imunologia, Avenida Bandeirantes, 3900, 14049-900 Ribeirão Preto, SP, Brazil

https://orcid.org/0000-0001-5697-5673

CAROLINE V. GONÇALVES

https://orcid.org/0000-0003-0895-1583

STÉFANO P.M. CALADO

https://orcid.org/0000-0003-3458-1328

DENISAR P. DOS SANTOS

https://orcid.org/0000-0002-3930-9510

IGOR P.R. MUNIZ

https://orcid.org/0000-0003-1842-6432

ROBSON A.A. DA SILVA

https://orcid.org/0000-0003-1361-1591

Correspondence to: Robson Amaro Augusto da Silva E-mail: robson.amaro@gmail.com

AUTHOR CONTRIBUTIONS

RAAS conceived the idea. MPLG, LSL, KBR, ISR, DPS, ISP and IPRM contributed with the interpretation of data, carried out the analysis of the data and the preparation of figures. LSL, KBR, CVG, SPMC contributed with the maintenance, weighing of the animals and assisted in swimming. MPLG, LSL anad IPRM contributed developing the discussion section and writing the manuscript. All authors are involved in interpreting the results and contributed reviewing the manuscript. RAAS, and MPLG supervised the final version. All authors read and approved the final manuscript.

SCIMAGO INSTITUTIONS RANKINGS

Figures | Tables

Figures (6)
Tables (1)

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Figure 1
Bacterial load on exercised and sedentary animals. A / J mice were challenged with the number of 10⁸ CFU of MRSA strains. Animals were euthanized 72 hours post-infection. Animals had the lymph nodes macerated and cultured in BHI medium (Brain Heart Infusion). CFUs were quantified after 24 hours of culture; (MRSA: Methicillin-resistant Staphylococcus aureus). CFU- colony forming unit; SC- sedentary control; MIC- moderate intensity control; HIC- high intensity control; SI- sedentary infected; MII- moderate intensity infected; HII- high intensity infected. n = 8 to 10 / group. *p0.05; *** p0.001.

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Figure 2
Determination of mice weight variation during training period. a) Weight mean of all animals in the group. b) Area under the curve corresponding to the Figure 2a. SC- sedentary control; MIC- moderate intensity control; HIC- high intensity control; SI- sedentary infected; MII- moderate intensity infected; HII- high intensity infected. n = 8 to 10 / group. * p0.05; ** p0.01; **** p0.0001.

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Figure 3
a) Determination of epididymal fat rate exhibited by the training group. This tissue is used as an indicator of animals’ lipid content. Epididymal fat was removed and immediately weighed to avoid dehydration. b) Determination of the animals’ lipid content. Epididymal fat weight was divided by the animal body weight, obtained before the sacrifice, and multiplied by 100 to provide the relative value and percentage. SC- sedentary control; MIC- moderate intensity control; HIC- high intensity control; SI- sedentary infected; MII- moderate intensity infected; HII- high intensity infected n = 8 to 10 / group. ** p0.01; *** p0.001; **** p0.0001.

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Figure 4
Neutrophil and Lymphocyte Differential Cell Counts - A / J mice were challenged with the amount of 10⁸ CFU of MRSA strains. Following challenge, the animals were euthanized after 72 hours. After sacrifice, blood samples were collected for the differential count performed through light microscopy. a) Number of neutrophils; b) Number of lymphocytes. SC- sedentary control; MIC- moderate intensity control; HIC- high intensity control; SI- sedentary infected; MII- moderate intensity infected; HII- high intensity infected n = 8 to 10 / group. ** p0.01; **** p0.0001.

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Figure 5
Leukocyte recruitment to the right ear dermis of A / J mice. Mice trained in moderate intensity, high intensity exercise, or the sedentaries, were infected with 10⁸ methicillin resistant Staphylococcus aureus (MRSA). Animals were euthanized 72 hours after infection. Animals had excision of the right ear and histopathological slides were analyzed through light microscopy (MRSA: Methicillin-resistant Staphylococcus aureus) n = 8 to 10. Magnification 20X. a) SC (Sedentary control); b) MIC (Moderate intensity control); c) HIC (High intensity control); d) SI (Sedentary infected); e) MII (Moderate intensity infected); f) HII (High intensity infected).

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Figure 6
Leukocyte recruitment in the ear dermis (μm²) – Sedentary A / J mice or previously trained in moderate intensity or high intensity exercise were infected with 10⁸ strains of methicillin resistant Staphylococcus aureus (MRSA). Animals were euthanized 72 hours after infection. Animals had excision of the right ear and histopathological slides were prepared and analyzed through light microscopy. SC- sedentary control; MIC- moderate intensity control; HIC- high intensity control; SI- sedentary infected; MII- moderate intensity infected; HII- high intensity infected n = 8 to 10. *p0,05; *** p0.001.

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Table I
Bacterial load correlate with lipid content in exercise mice.

Figure 1 Bacterial load on exercised and sedentary animals. A / J mice were challenged with the number of 10⁸ CFU of MRSA strains. Animals were euthanized 72 hours post-infection. Animals had the lymph nodes macerated and cultured in BHI medium (Brain Heart Infusion). CFUs were quantified after 24 hours of culture; (MRSA: Methicillin-resistant Staphylococcus aureus). CFU- colony forming unit; SC- sedentary control; MIC- moderate intensity control; HIC- high intensity control; SI- sedentary infected; MII- moderate intensity infected; HII- high intensity infected. n = 8 to 10 / group. *p0.05; *** p0.001.

Figure 2 Determination of mice weight variation during training period. a) Weight mean of all animals in the group. b) Area under the curve corresponding to the Figure 2a. SC- sedentary control; MIC- moderate intensity control; HIC- high intensity control; SI- sedentary infected; MII- moderate intensity infected; HII- high intensity infected. n = 8 to 10 / group. * p0.05; p0.01; ** p0.0001.

Figure 3 a) Determination of epididymal fat rate exhibited by the training group. This tissue is used as an indicator of animals’ lipid content. Epididymal fat was removed and immediately weighed to avoid dehydration. b) Determination of the animals’ lipid content. Epididymal fat weight was divided by the animal body weight, obtained before the sacrifice, and multiplied by 100 to provide the relative value and percentage. SC- sedentary control; MIC- moderate intensity control; HIC- high intensity control; SI- sedentary infected; MII- moderate intensity infected; HII- high intensity infected n = 8 to 10 / group. p0.01; * p0.001; **** p0.0001.

Figure 4 Neutrophil and Lymphocyte Differential Cell Counts - A / J mice were challenged with the amount of 10⁸ CFU of MRSA strains. Following challenge, the animals were euthanized after 72 hours. After sacrifice, blood samples were collected for the differential count performed through light microscopy. a) Number of neutrophils; b) Number of lymphocytes. SC- sedentary control; MIC- moderate intensity control; HIC- high intensity control; SI- sedentary infected; MII- moderate intensity infected; HII- high intensity infected n = 8 to 10 / group. p0.01; ** p0.0001.

Figure 5 Leukocyte recruitment to the right ear dermis of A / J mice. Mice trained in moderate intensity, high intensity exercise, or the sedentaries, were infected with 10⁸ methicillin resistant Staphylococcus aureus (MRSA). Animals were euthanized 72 hours after infection. Animals had excision of the right ear and histopathological slides were analyzed through light microscopy (MRSA: Methicillin-resistant Staphylococcus aureus) n = 8 to 10. Magnification 20X. a) SC (Sedentary control); b) MIC (Moderate intensity control); c) HIC (High intensity control); d) SI (Sedentary infected); e) MII (Moderate intensity infected); f) HII (High intensity infected).

Figure 6 Leukocyte recruitment in the ear dermis (μm²) – Sedentary A / J mice or previously trained in moderate intensity or high intensity exercise were infected with 10⁸ strains of methicillin resistant Staphylococcus aureus (MRSA). Animals were euthanized 72 hours after infection. Animals had excision of the right ear and histopathological slides were prepared and analyzed through light microscopy. SC- sedentary control; MIC- moderate intensity control; HIC- high intensity control; SI- sedentary infected; MII- moderate intensity infected; HII- high intensity infected n = 8 to 10. *p0,05; *** p0.001.

Table I Bacterial load correlate with lipid content in exercise mice.

CORRELATIONS BETWEEN GROUPS	p	r
Lipid content MII X Bacterial load MII	0,0220	0,7079
MII total count X Neutrophils MII	0,0017	0,8531
Total score SC X Neutrophils SC	0,0004	0,9453

SC - sedentary control; MII - moderate intensity infected; p – p-value (p<0.05); r – Pearson correlation coefficient; n = 8 to 10.

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Physical activity reduces intradermal bacterial load in a murine model submitted to forced swim training – a pilot study

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[1] Correspondence to: Robson Amaro Augusto da Silva E-mail: robson.amaro@gmail.com