Journal of Bacteriology & Parasitology

Inhibition of Staphylococcus aureus by Corynebacterium Species: A Mini-Review

Sana Alibi^{1,2* 1}Department of Biology, University of Gafsa, Tunisia
²Research Unit: Analysis and Process Applied to the Environment, University of Monastir, Mahdia, Tunisia
^*Correspondence: Sana Alibi, Department of Biology, University of Gafsa, Tunisia, Tel: +21698980610, Email:

Received: 16-Apr-2023, Manuscript No. JBP-23-21079; Editor assigned: 20-Apr-2023, Pre QC No. JBP-23-21079 (PQ); Reviewed: 04-May-2023, QC No. JBP-23-21079; Revised: 11-May-2023, Manuscript No. JBP-23-21079 (R); Published: 18-May-2023, DOI: 10.35248/2155-9597.23.14.459

Introduction

Staphylococcus aureus is a common colonizer of human nose and skin. This carriage increased the risk of autoinfection. Indeed, the emergence of S. aureus resistant to multiple antibiotics, in particular, Methicillin-Resistant S. aureus (MRSA) is a serious problem worldwide. It becomes crucial to look for alternative methods to prevent the nasal chronic colonization of S. aureus. The use of the symbiotic microbiota may be a good approach. Recently, C. accolans was suggested as a promotor probiotic to ameliorate the health of patients with chronic rhinosinusitis [1].

Corynebacterium spp. constitutes a major compound of the normal microbiota. The coexistence of Corynebacterium spp. with S. aureus in the skin and the nasal cavities leads to an interaction between them. Some researchers demonstrated that S. aureus is inhibited by Corynebacterium spp. Here, we summarized the main results of researchers studying the interaction between these two microorganisms.

Corynebacterium spp. inhibits the growth of S. aureus

Since 1987, studies focusing in the interaction between Corynebacterium species and S. aureus have been started. Hogan et al (1987) reported that the coculture of C. bovis and S. aureus inhibited the growth of this last in comparison with a monoculture.

In 2016, Ramsey et al (2016) studied in vitro the interaction between S. aureus and Corynebacterium spp. They showed that the coculture of C. striatum and S. aureus inhibited the growth of S. aureus on agar plates. The number of CFUs of S. aureus in a co-infection is lower in a mono-infection, whereas CFUs of C. striatum increased [2].

This same observation was recently confirmed when S. aureus was co-incubated with C. pseudodiphtheriticum (2020). Hardy et al (2020) found that the strain obtained from the nose of a healthy volunteer exhibited a larger inhibition zone than a lab-adapted strain. This species exhibited a selective bactericidal activity against S. aureus strains [3].

It collectively suggests that certain species of Corynebacterium, such as C. bovis, C. striatum, and C. pseudodiphtheriticum, possess the ability to inhibit the growth of S. aureus. This inhibition may be mediated through mechanisms such as the production of antimicrobial substances or competition for nutrients and resources. It is needed to understand the specific mechanisms involved in this interaction and explore its potential applications in combating S. aureus infections.

Corynebacterium inhibits the adherence of S. aureus to epithelial cells

The binding of S. aureus to nasal epithelial cells is a crucial step in the process of infection [4,5].

The relationship between S. aureus nasal carriage and the development of serious infections has been established in immune-depressed patients [6]. The elimination of nasal carriage may be done by the administration of antibiotics (local or systemic). The use of bacteria instead of antibiotics may be a potential strategy is to decrease S. aureus nasal carriage [6].

In 2000, Uehara et al (2000) evaluated the role of the normal nasal microbiota in the elimination of Staphylococcus spp. They found that the implantation of a Corynebacterium strain (Co304) leaded to the eradication of S. aureus from the nares of 71% of the 17 volunteers. However, this strain didn’t exhibit a bacteriocin-like activity against S. aureus in solid and liquid culture media [7].

The authors suggested that there is a competition for survival between these species [7]. This hypothesis was previously established by Wickham et al (1978) who supposed that initial bacterial colonizers could block later establishment of S. aureus.

This observation was confirmed by testing bacterial adherence to epithelial cells in nasal cavities. Corynebacterium spp. strain showed higher affinity to nasal mucus than S. aureus [7].

In 2013, a study yielded in USA showed the effectiveness of a bacterial solution of C. pseudodiphtheriticum to shift the nasal community. The administration of this solution to volunteers with chronic staphylococci nasal carriage exhibited a notable reduction in the number of CFU of S. aureus versus an augmentation in C. striatum CFUs. This solution eradicated S. aureus after 2 to 3 weeks of spraying. Observations with Transmission Electron Microscopy (TEM) showed that the presence of C. pseudodiphtheriticum altered the cell wall of S. aureus which causes the cell lysis [8].

The authors suggested that this method could be useful for the prophylaxis and the treatment of the nasal carriage by S. aureus, potentially providing an alternative strategy to antibiotics to reduce S. aureus nasal carriage and associated infections [9].

Corynebacterium spp. regulated the expression of agr QS system

Ramsey et al (2016) investigated the molecular mechanism of the inhibition of S. aureus by C. striatum. They found that the co- incubation of S. aureus with C. striatum in a solid media inhibits the transcription and the expression of genes implicated the colonization and the virulence.

The expression of more than 460 genes was different in the co- culture compared to the monoculture. C. striatum regulated the transcription of agr operon which results in the decrease of psmb1 gene. Also, C. striatum deceased the expression of agr Quorum Sensing (agr QS) system [10].

In S. aureus, the agr QS system controls the expression of many virulence factors [11]. As a consequence, C. striatum inhibited the expression of virulence genes involved in the invasive infection and increased the expression of the factors implicated in cell-adhesion and host colonization. It indirectly influenced the expression of other agr-dependant genes [10].

In the same study, results showed that, in addition to C. striatum, other Corynebacterium species including C. amycolatum, C. accolans, C. pseudodiphtheriticum and C. glutamicum, also altered the expression of the agr QS system in S. aureus. This suggests that the regulation of agr QS by Corynebacterium species may be a common mechanism among different strains [10].

Results of an investigation conducted by Hardy et al (2020) joined this study. They reported that the target of C. pseudodiphtheriticum is the agrBDCA gene. Resistance of S. aureus to C. pseudodiphtheriticum was induced by the absence or the diminution in the expression of agrBDCA [3].

This team studied the link between the agr QS system and C. pseudodiphtheriticum-mediated bactericidal activity. Their experiments showed that the expression of alpha-psm reduced the sensitivity of S. aureus strains to C. pseudodiphtheriticum- mediated bactericidal activity [10].

These findings indicate that Corynebacterium species, including C. striatum and C. pseudodiphtheriticum, have the ability to regulate the agr QS system in S. aureus, leading to alterations in gene expression and modulation of virulence factors. This is to fully understand the underlying mechanisms and implications of this regulatory interaction.

Corynebacterium spp. regulated the expression of the Spa gene

Staphylococcal protein A (Spa) is an important virulence factor of S. aureus which is expressed during the exponential phase of growth and then is transcriptionally down-regulated during the post-exponential phase of growth [12]. It enables S. aureus to evade hosting immune response [13].

In a co-culture of S. aureus and C. striatum, researchers observed an alteration in the expression of the gene encoding the surface protein of Staphylococci (Spa), which is implicated in its protection from the opsonization and phagocytosis, and during nasal colonization. However, the exposure of S. aureus to C. striatum increased its adhesion to human epithelial cells [10].

Corynebacterium spp. reduces the hemolytic activity of S. aureus

Hemolysin is one of the important virulence factors for S. aureus and causes the typical β-hemolytic. Recently, clinical isolates showed a new profile characterized by an incomplete hemolytic phenotype. The hemolytic activity of S. aureus facilitates the damage the red cell membrane, alters the phagocytosis, induces toxic shock syndrome, and participates in the biofilm formation [14].

The hemolytic activity of S. aureus clearly decreased in the presence of C. striatum which confirms that S. aureus shifts its virulence factors when exposed to C. striatum [10,15].

Corynebacterium spp. compete for iron uptake

Iron is a vital factor for the growth and proliferation of pathogenic bacteria. Iron acquisition is required for S. aureus in colonization and subsequent pathogenesis. The functional redundancy built into staphylococcal iron acquisition systems guarantees the pathogen obtains enough iron to successfully colonize a variety of diverse niches within the host. A restriction of iron amount in the environment during infection affects directly the survival of S. aureus and may be alternative strategies to combat this pathogen [16].

Recently, Stubbendieck et al (2016) focused on the bacterial interaction in the human nasal cavity. They isolated three C. propinquum isolates that strongly inhibited coagulase negative Staphylococcus. The genome sequencing of these strains revealed that it was rich in genes implicated in the iron acquisition. The biosynthetic gene cluster implicated in siderophore production was identified in the inhibitor strains and absent in the non- inhibitor strains [17,18].

Conclusion

In conclusion, Corynebacterium spp. have a negative effect on S. aureus. The presence of this microorganism induced the repression of genes encoding virulence factors in particular the agr system and its related genes. Corynebacterium spp. caused also a decrease in the hemolytic activity and was responsible for harmful damages in the wall of S. aureus. Therefore, the use of Corynebacterium spp. strains may be a good alternative to eradicate S. aureus in particular with the emergence of MRSA strains. However, it is important to note that further in-depth studies are needed to fully understand the mechanisms involved and to explore the feasibility and efficacy of using Corynebacterium spp. strains as a therapeutic approach against S. aureus infections.

Overall, these findings suggest that the interactions between Corynebacterium spp. and S. aureus hold promise for the development of novel strategies to combat S. aureus infections, but more research is required before such approaches can be implemented clinically.

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