Impact of Heat Stress on Pregnant Subsistence Farmers in West Africa

## **Involvement of Panton–Valentine Leukocidin-Producing Staphylococcus aureus in Staphylococcal Skin Diseases in Patients in Peri-Urban Benin**

**Bawa Boya1, Hachim Mamadou1, and Théodora A. Ahoyo2**

1Laboratory of Biology and Molecular Typing in Microbiology, Cotonou, Benin

2Engineering of Human Biology/Polytechnic School of Abomey-Calavi, Cotonou, Benin

Staphylococcus aureus is a pathogen that colonizes a large part of the general population and causes a wide spectrum of diseases. About 3% of S. aureus strains express a virulence factor called Panton–Valentine leucocidin (PVL). This study aims to highlight the role of PVL in staphylococcal infections in a peri-urban area of Benin. This is a study that involved a cohort of 124 patients with the staphylococcal disease (wound, abscess, furuncle, osteomyositis, pyomisitis) received at the " Réservoir de Siloé " health center in Hlagbaouassa, commune de Zogbodomè, from November 2014 to December 2017. Data were retrospectively collected in 71 patients and prospective and longitudinal in 53 patients. The profile of the 123 patients was established on the basis of sociodemographic, clinical, microbiological, hematological, and immunological parameters. Patients are female-dominated, with a sex ratio equal to 80%, and a slice of [1; 10 years] that was the most represented as 68.55%. A total of 54.03% use traditional medicine for treatment, and only 10.28% of patients use probabilistic antibiotic therapy. With regard to microbiological analysis, 129 cases of S. aureus have been isolated, with 100% in pyomyositis cases. A total of 29.61% of strains of S. aureus are resistant to the tested antibiotics, of which 100% are penicillin. A total of 70.39% of strains of S. aureus are susceptible to tested antibiotics, including 100% vancomycin and ciprofloxacin. A total of 75.61% of S. aureus strains produce PVL, and 89.15% of its strains are sensitive to meticillin. Follow-up showed that patients with PVL + showed, at the start of treatment, leukocytosis (91.18%) and a decrease in CD4 compared to those with LPV-. It was noted that a gradual improvement of immunological parameters became normal in almost all patients at the fourth week of follow-up. S. aureus, a producer of PVL, plays a major role in staphylococcal infections in peri-urban areas in Benin. The presence of methicillin-sensitive strains suggests the loss of the horizontal transfer meticillin resistance gene.

#### Methodology

This study focused on a cohort of 124 patients with staphylococcal diseases (wound, abscess, furuncle, osteomyositis and pyomisitis) received at the "Siloe Reservoir" health center in Hlagba-ouassa, a commune of Zogbodome, from November 2014 to December 2017. Data were collected retrospectively on 71 patients and prospectively and longitudinally on 53 patients. The profile of the 124 patients was established on the basis of sociodemographic, clinical, microbiological, hematological and immunological parameters. Then, the immunological follow-up of the cohort of 53 patients (34 PVL+ and 19 PVL-) was performed weekly for 4 weeks on the basis of the following parameters: CRP, VS, NB, CD4.

The patients were predominately female, with a sex ratio equal to 0.8, and the age group [1; 10 years] was the most represented, i.e., 68.55%. The age group [1 to 10 years] was the most affected regardless of disease. The most common diseases were pyomyositis (42.74%), osteomyelitis (24.19%) and abscesses (20.97%). Before the medical consultaion, 54.03% of the patients first resorted to traditional medicine to treat themselves, and 10.28% resorted to probabalistic antibiotic therapy (Figure 1).

*Figure 1. Distribution of patients according to treatment at home.*

#### Bacterial species isolated according to the type of infection

Figure 2 shows that Staphylococcus aureus was isolated in 83.11% of the cases studied, and the majority of Staphylococcus aureus was isolated in pure culture in 100% of the pyomyositis cases. There was no significant difference between the bacterial strains according to the infections (p >0.9999).

A total of 29.61% of Staphylococcus aureus strains were resistant to the antibiotics tested, including 100% to Penicillin. A total of 70.39% of Staphylococcus aureus stains were sensitive to the antibiotics tested, including 100% to Vancomycin and Ciprofloxacin. A total of 91 strains of S. aureus out of 123 isolated produced Panton-Valentine leucocidin (PVL), i.e., 73.98% of the strains tested. All PVL-producing S. aureus strains were sensitive to methicillin, while 40.63% of non-PVL- producing S. aureus strains were resistant to methicillin. There was no significant difference between methicillin-susceptible and methicillin-resistant S. aureus strains (p> 0.9999) according to the production of PVL.

The majority of patients were seronegative with a CPR level higher than 6mg/l at admission. Despite this seronegative result, we observed a depletion in T4 lymphocytes in most patients. The follow-up of the patients over four weeks showed a clear improvement of the immunological parameters in the majority (even though the literature does not say much about this case, this indicates the impact of PVL on the immune system of PVL+ patients.

#### Conclusions

*S. aureus*, as a producer of PVL, plays a major role in staphylococcal infections in peri-urban areas in Benin. The presence of methicillin-sensitive strains suggests the loss of the horizontal transfer methicillin-resistance gene.

Keywords: S. aureus; PVL; staphylococcal skin infections; community; Benin

Acknowledgements: The authors express their gratitude to the LBTMM staff for their contribution to this study

#### Authors

Bawa Boya1, Hachim Mamadou1, and Théodora A. Ahoyo2

1 Laboratoire de Biologie et de Typage Moleculaire en Microbiologie; Universite d'Abomey-Calavi, 05 BP 1604 Cotonou, Benin 2 Genie de Biologie Humaine, Ecole Polytechnique d'Abomey-Calavi; Universite d'Abomey-Calavi, BP 2009 Cotonou, Benin

Introduction: Staphylococcus aureus is a pathogen that colonizes a large part of the general population and causes a wide spectrum of diseases. About 3% of S. aureus strains express a virulence factor called Panton-Valentine Leucocidin (PVL). This study aims to highlight the role of PVL in staphylococcal infections in a peri-urban area of Benin.
