Nasal microbiome disruption and recovery after mupirocin treatment in Staphylococcus aureus carriers and noncarriers

Interventions targeting the nasal microbiome to eradicate methicillin-resistant Staphylococcusaureus

BACKGROUND

Staphylococcus aureus is an important pathogen in many sites, including the bloodstream, skin and soft tissue, bone and joints. When infection is caused by methicillin-resistant S. aureus (MRSA), therapy is more difficult and outcomes are less favourable. Nasal colonization is associated with increased risk for MRSA infections. The nasal microbiome may play a role in risk for nasal colonization and infection.

OBJECTIVES

To review the role of the microbiome in MRSA nasal colonization and infection.

SOURCES

Peer-reviewed literature identified in a MEDLINE search using MRSA, S. aureus, prebiotic and microbiota as search terms.

CONTENT

Reduction of S. aureus nasal colonization has been shown to reduce risk of S. aureus infections, but decolonization methods are imperfect. The role of the nasal microbiome in host defence against S. aureus colonization and infection is explored. Numerous organisms have been shown to be negatively associated with S. aureus colonization. The antimicrobial molecules produced by these organisms are an active area of research.

IMPLICATIONS

Future research should focus on development of safe and effective molecules that can inhibit S. aureus in the nasal vestibule. Damage to the diverse nasal microbiota by unnecessary antibiotics should be avoided.

Staphylococcus aureus colonisation and strategies for decolonisation

Staphylococcus aureus is a leading cause of death by infectious diseases worldwide. Treatment of S aureus infections is difficult due to widespread antibiotic resistance, necessitating alternative approaches and measures for prevention of infection. Because S aureus infections commonly arise from asymptomatic colonisation, decolonisation is considered a key approach for their prevention. Current decolonisation procedures include antibiotic-based and antiseptic-based eradication of S aureus from the nose and skin. However, despite the widespread implementation and partial success of such measures, S aureus infection rates remain worrisome, and resistance to decolonisation agents is on the rise. In this Review we outline the epidemiology and mechanisms of S aureus colonisation, describe how colonisation underlies infection, and discuss current and novel approaches for S aureus decolonisation, with a focus on the latest findings on probiotic strategies and the intestinal S aureus colonisation site.

Impact of control measures including decolonization and hand hygiene for orthopaedic surgical site infection caused by MRSA at a Japanese tertiary-care hospital

BACKGROUND

Meticillin-resistant Staphylococcus aureus (MRSA) is the most common pathogen in orthopaedic surgical site infections (SSIs). However, few studies have investigated the transmission process of orthopaedic MRSA SSI.

AIM

To investigate the transmission process of orthopaedic MRSA SSI using epidemiological and molecular analyses and to determine a method to prevent MRSA SSI in nosocomial orthopaedic surgery.

METHODS

Active MRSA surveillance, preoperative decolonization and contact precautions for MRSA-positive cases was performed at our institution. Changes in epidemic strains were evaluated and the possibility of transmission from patients in an orthopaedic ward of a Japanese tertiary-care hospital was assessed by genotyping stored MRSA strains. In addition, data on the prevalence of MRSA SSI, MRSA colonization, and use of an alcohol antiseptic agent (mL/patient-days) during 2005-2022 were retrospectively assessed.

FINDINGS

SCCmec type II strain in the SSI group decreased over time, associated with fewer outbreaks. Even during a period of high infection rates, no cases of transmission-induced SSI from nasal MRSA carriers were identified. The infection rate correlated negatively with the use of an alcohol antiseptic agent (r = -0.82; P < 0.0001). Two cases among five nasal carriers developed MRSA SSI caused by strains different from those related to nasal colonization.

CONCLUSION

The infection control measures for transmission from the hospital reservoirs including strict adherence to hand hygiene and decolonization of carriers is likely to be important for the prevention of orthopaedic MRSA SSI. However, the need for contact precautions for decolonized nasal carriers might be low.

Characterisation of a capsular polysaccharide from Moraxella nonliquefaciens CCUG 348T

Moraxella nonliquefaciens is a commensal of the human upper respiratory tract (URT) but on rare occasions is recovered in cases of ocular, septic and pulmonary infections. Hence there is interest in the pathogenic determinants of M. nonliquefaciens, of which outer membrane (OM) structures such as fimbriae and two capsular polysaccharide (CPS) structures, →3)-β-D-GalpNAc-(1→5)-β-Kdop-(2→ and →8)-α-NeuAc-(2→, have been reported in the literature. To further characterise its surface virulence factors, we isolated a novel CPS from M. nonliquefaciens type strain CCUG 348T. This structure was elucidated using NMR data obtained from CPS samples that were subjected to various degrees of mild acid hydrolysis. Together with GLC-MS data, the structure was resolved as a linear polymer composed of two GalfNAc residues consecutively added to Kdo, →3)-β-D-GalfNAc-(1→3)-α-D-GalfNAc-(1→5)-α-(8-OAc)Kdop-(2→. Supporting evidence for this material being CPS was drawn from the proposed CPS biosynthetic locus which encoded a potential GalfNAc transferase, a UDP-GalpNAc mutase for UDP-GalfNAc production and a putative CPS polymerase with predicted GalfNAc and Kdo transferase domains. This study describes a unique CPS composition reported in Moraxella spp. and offers genetic insights into the synthesis and expression of GalfNAc residues, which are rare in bacterial OM glycans.