Dataset Information

?-Lactam Antibiotics Enhance the Pathogenicity of Methicillin-Resistant Staphylococcus aureus via SarA-Controlled Lipoprotein-Like Cluster Expression.

ABSTRACT: Methicillin-resistant Staphylococcus aureus (MRSA) resists nearly all ?-lactam antibiotics that have a bactericidal activity. However, whether the empirically used ?-lactams enhance MRSA pathogenicity in vivo remains unclear. In this study, we showed that a cluster of lipoprotein-like genes (lpl, sa2275 to sa2273 [sa2275-sa2273]) was upregulated in MRSA in response to subinhibitory concentrations of ?-lactam induction. The increasing expression of lpl by ?-lactams was directly controlled by the global regulator SarA. The ?-lactam-induced Lpls stimulated the production of interleukin-6 and tumor necrosis factor alpha in RAW 264.7 macrophages. The lpl deletion mutants (N315?lpl and USA300?lpl) decreased the proinflammatory cytokine levels in vitro and in vivo Purified lipidated SA2275-his proteins could trigger a Toll-like-receptor-2 (TLR2)-dependent immune response in primary mouse bone marrow-derived macrophages and C57BL/6 mice. The bacterial loads of N315?lpl in the mouse kidney were lower than those of the wild-type N315. The ?-lactam-treated MRSA exacerbated cutaneous infections in both BALB/c and C57BL/6 mice, presenting increased lesion size; destroyed skin structure; and easily promoted abscess formation compared with those of the untreated MRSA. However, the size of abscesses caused by the ?-lactam-treated N315 was negligibly different from those caused by the untreated N315?lpl in C57BL/6 TLR2-/- mice. Our findings suggest that ?-lactams must be used carefully because they might aggravate the outcome of MRSA infection compared to inaction in treatment.IMPORTANCE ?-Lactam antibiotics are widely applied to treat infectious diseases. However, certain poor disease outcomes caused by ?-lactams remain poorly understood. In this study, we have identified a cluster of lipoprotein-like genes (lpl, sa2275-sa2273) that is upregulated in the major clinically prevalent MRSA clones in response to subinhibitory concentrations of ?-lactam induction. The major highlight of this work is that ?-lactams stimulate the expression of SarA, which directly binds to the lpl cluster promoter region and upregulates lpl expression in MRSA. Deletion of lpl significantly decreases proinflammatory cytokine levels in vitro and in vivo The ?-lactam-induced Lpls enhance host inflammatory responses by triggering the Toll-like-receptor-2-mediated expressions of interleukin-6 and tumor necrosis factor alpha. The ?-lactam-induced Lpls are important virulence factors that enhance MRSA pathogenicity. These data elucidate that subinhibitory concentrations of ?-lactams can exacerbate the outcomes of MRSA infection through induction of lpl controlled by the global regulator SarA.

SUBMITTER: Shang W

PROVIDER: S-EPMC6561022 | biostudies-literature | 2019 Jun

REPOSITORIES: biostudies-literature

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β-Lactam Antibiotics Enhance the Pathogenicity of Methicillin-Resistant Staphylococcus aureus via SarA-Controlled Lipoprotein-Like Cluster Expression.

Shang Weilong W Rao Yifan Y Zheng Ying Y Yang Yi Y Hu Qiwen Q Hu Zhen Z Yuan Jizhen J Peng Huagang H Xiong Kun K Tan Li L Li Shu S Zhu Junmin J Li Ming M Hu Xiaomei X Mao Xuhu X Rao Xiancai X

mBio 20190611 3

Methicillin-resistant Staphylococcus aureus (MRSA) resists nearly all β-lactam antibiotics that have a bactericidal activity. However, whether the empirically used β-lactams enhance MRSA pathogenicity in vivo remains unclear. In this study, we showed that a cluster of lipoprotein-like genes (lpl, sa2275 to sa2273 [sa2275-sa2273]) was upregulated in MRSA in response to subinhibitory concentrations of β-lactam induction. The increasing expression of ...[more]

PMID: 31186320

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Project description:Bacterial infections remain the leading killer worldwide which is worsened by the continuous emergence of antibiotic resistance. In particular, methicillin-sensitive (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA) are prevalent and the latter can be difficult to treat. The traditional strategy of novel therapeutic drug development inevitably leads to emergence of resistant strains, rendering the new drugs ineffective. Therefore, rejuvenating the therapeutic potentials of existing antibiotics offers an attractive novel strategy. Plectasin, a defensin antimicrobial peptide, potentiates the activities of other antibiotics such as ?-lactams, aminoglycosides and glycopeptides against MSSA and MRSA. We performed in vitro and in vivo investigations to test against genetically diverse clinical isolates of MSSA (n = 101) and MRSA (n = 115). Minimum inhibitory concentrations (MIC) were determined by the broth microdilution method. The effects of combining plectasin with ?-lactams, aminoglycosides and glycopeptides were examined using the chequerboard method and time kill curves. A murine neutropenic thigh model and a murine peritoneal infection model were used to test the effect of combination in vivo. Determined by factional inhibitory concentration index (FICI), plectasin in combination with aminoglycosides (gentamicin, neomycin or amikacin) displayed synergistic effects in 76-78% of MSSA and MRSA. A similar synergistic response was observed when plectasin was combined with ?-lactams (penicillin, amoxicillin or flucloxacillin) in 87-89% of MSSA and MRSA. Interestingly, no such interaction was observed when plectasin was paired with vancomycin. Time kill analysis also demonstrated significant synergistic activities when plectasin was combined with amoxicillin, gentamicin or neomycin. In the murine models, plectasin at doses as low as 8 mg/kg augmented the activities of amoxicillin and gentamicin in successful treatment of MSSA and MRSA infections. We demonstrated that plectasin strongly rejuvenates the therapeutic potencies of existing antibiotics in vitro and in vivo. This is a novel strategy that can have major clinical implications in our fight against bacterial infections.

Dataset Information

?-Lactam Antibiotics Enhance the Pathogenicity of Methicillin-Resistant Staphylococcus aureus via SarA-Controlled Lipoprotein-Like Cluster Expression.

Publications

β-Lactam Antibiotics Enhance the Pathogenicity of Methicillin-Resistant Staphylococcus aureus via SarA-Controlled Lipoprotein-Like Cluster Expression.

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