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

Nasal decolonization procedures against the opportunistic pathogen Staphylococcus aureus rely on topical antimicrobial drug usage, whose impact on the nasal microbiota is poorly understood. We examined this impact in healthy S. aureus carriers and noncarriers. This is a prospective interventional cohort study of 8 S. aureus carriers and 8 noncarriers treated with nasal mupirocin and chlorhexidine baths. Sequential nasal swabs were taken over 6 months. S. aureus was detected by quantitative culture and genotyped using spa typing. RNA-based 16S species-level metabarcoding was used to assess the living microbial diversity. The species Dolosigranulum pigrum, Moraxella nonliquefaciens and Corynebacterium propinquum correlated negatively with S. aureus carriage. Mupirocin treatment effectively eliminated S. aureus, D. pigrum and M. nonliquefaciens, but not corynebacteria. S. aureus recolonization in carriers occurred more rapidly than recolonization by the dominant species in noncarriers (median 3 vs. 6 months, respectively). Most recolonizing S. aureus isolates had the same spa type as the initial isolate. The impact of mupirocin-chlorhexidine treatment on the nasal microbiota was still detectable after 6 months. S. aureus recolonization predated microbiota recovery, emphasizing the strong adaptation of this pathogen to the nasal niche and the transient efficacy of the decolonization procedure

Dehydration Tolerance in Epidemic versus Nonepidemic MRSA Demonstrated by Isothermal Microcalorimetry.

Methicillin-resistant Staphylococcus aureus (MRSA) clusters are considered epidemic or nonepidemic based on their ability to spread effectively. Successful transmission could be influenced by dehydration tolerance. Current methods for determination of dehydration tolerance lack accuracy. Here, a climate-controlled in vitro dehydration assay using isothermal microcalorimetry (IMC) was developed and linked with mathematical modeling to determine survival of 44 epidemic versus 54 nonepidemic MRSA strains from France, the United Kingdom, and the Netherlands after 1 week of dehydration. For each MRSA strain, the growth parameters time to end of first growth phase (tmax [h]) and maximal exponential growth rate (μm) were deduced from IMC data for 3 experimental replicates, 3 different starting inocula, and before and after dehydration. If the maximal exponential growth rate was within predefined margins (±36% of the mean), a linear relationship between tmax and starting inoculum could be utilized to predict log reduction after dehydration for individual strains. With these criteria, 1,330 of 1,764 heat flow curves (data sets) (75%) could be analyzed to calculate the post-dehydration inoculum size, and thus the log reduction due to dehydration, for 90 of 98 strains (92%). Overall reduction was ~1 log after 1 week. No difference in dehydration tolerance was found between the epidemic and nonepidemic strains. Log reduction was negatively correlated with starting inoculum, indicating better survival of higher inocula. This study presents a framework to quantify bacterial survival. MRSA strains showed great capacity to persist in the environment, irrespective of epidemiological success. This finding strengthens the need for effective surface cleaning to contain MRSA transmission. IMPORTANCE Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of infections globally. While some MRSA clusters have spread worldwide, others are not able to disseminate successfully beyond certain regions despite frequent introduction. Dehydration tolerance facilitates transmission in hospital environments through enhanced survival on surfaces and fomites, potentially explaining differences in transmission success between MRSA clusters. Unfortunately, the currently available techniques to determine dehydration tolerance of cluster-forming bacteria like S. aureus are labor-intensive and unreliable due to their dependence on quantitative culturing. In this study, bacterial survival was assessed in a newly developed assay using isothermal microcalorimetry. With this technique, the effect of drying can be determined without the disadvantages of quantitative culturing. In combination with a newly developed mathematical algorithm, we determined dehydration tolerance of a large number of MRSA strains in a systematic, unbiased, and robust manner

MRSA surveillance programmes worldwide : moving towards a harmonised international approach

Multinational surveillance programmes for methicillin-resistant Staphylococcus aureus (MRSA) are dependent on national structures for data collection. This study aimed to capture the diversity of national MRSA surveillance programmes and to propose a framework for harmonisation of MRSA surveillance. The International Society of Antimicrobial Chemotherapy (ISAC) MRSA Working Group conducted a structured survey on MRSA surveillance programmes and organised a webinar to discuss the programmes’ strengths and challenges as well as guidelines for harmonisation. Completed surveys represented 24 MRSA surveillance programmes in 16 countries. Several countries reported separate epidemiological and microbiological surveillance. Informing clinicians and national policy-makers were the most common purposes of surveillance. Surveillance of bloodstream infections (BSIs) was present in all programmes. Other invasive infections were often included. Three countries reported active surveillance of MRSA carriage. Method- ology and reporting of antimicrobial susceptibility, virulence factors, molecular genotyping and epidemiological metadata varied greatly. Current MRSA surveillance programmes rely upon heterogeneous data collection systems, which hampers international epidemiological monitoring and research. To harmonise MRSA surveillance, we suggest improving the integration of microbiological and epidemiological data, implementation of central biobanks for MRSA isolate collection, and inclusion of a representative sample of skin and soft-tissue infection cases in addition to all BSI cases.peer-reviewe

gwenknight/strain_growth

Strain growth analysis of calorimeter data, pre and post dessication. Supporting code for "Dehydration tolerance in epidemic versus nonepidemic MRSA demonstrated by isothermal microcalorimetry", authored by: Valérie O. Baede a, Mehri Tavakol a, Margreet C. Vos a, Gwenan M. Knight, Willem J.B. van Wamel on behalf of the MACOTRA study group

Extended-Spectrum Beta-Lactamase and AmpC-producing Enterobacteriaceae in household dogs : a longitudinal study

A longitudinal study was performed (i) to investigate continuity of shedding of extended-spectrum beta-lactamase (ESBL) producing Enterobacteriaceae in dogs without clinical signs, (ii) to identify dominant plasmid-mediated ESBL genes and (iii) to quantify ESBL-producing Enterobacteriaceae in feces. Fecal samples of 38 dogs were collected monthly for 6 months. From 7 included dogs, additional samples were collected on a weekly basis for 6 weeks. CFU/g feces were determined for non-wild-type Enterobacteriaceae on MacConkey agar supplemented with 1 mg/L cefotaxime (MCC) and total number of Enterobacteriaceae on MacConkey agar. Cefotaxime-resistant isolates were screened by PCR and sequence analysis for presence of blaCTX-M, blaCMY, blaSHV, blaOXA and blaTEM gene families. Bacterial species were identified by MALDI-TOF MS analysis. PCR-negative isolates were tested by double disk synergy test for enhanced AmpC expression. 259 samples were screened, 126 samples were culture-positive on MCC, resulting in 352 isolates of which 327 isolates were Escherichia coli. Nine dogs were continuously positive during this study and 6 dogs were continuously negative. Monthly or weekly shifts in fecal shedding were observed in 23 dogs. Genotyping showed high variety of ESBL genes and gene combinations at single and multiple consecutive sampling moments. ESBL genes blaCTX-M-1, blaCTX-M-14, blaCTX-M-15, blaSHV-12 and blaCMY-2 were most frequently found. Mean cfu of non-wild-type Enterobacteriaceae was 6.11×10(8) cfu/g feces. This study showed an abundance of ESBL-producing Enterobacteriaceae in dogs in the Netherlands, mostly in high concentrations. Fecal shedding showed to be highly dynamic over time which is important to consider when studying ESBL epidemiology

Extended-Spectrum Beta-Lactamase and AmpC-producing Enterobacteriaceae in household dogs : a longitudinal study

A longitudinal study was performed (i) to investigate continuity of shedding of extended-spectrum beta-lactamase (ESBL) producing Enterobacteriaceae in dogs without clinical signs, (ii) to identify dominant plasmid-mediated ESBL genes and (iii) to quantify ESBL-producing Enterobacteriaceae in feces. Fecal samples of 38 dogs were collected monthly for 6 months. From 7 included dogs, additional samples were collected on a weekly basis for 6 weeks. CFU/g feces were determined for non-wild-type Enterobacteriaceae on MacConkey agar supplemented with 1 mg/L cefotaxime (MCC) and total number of Enterobacteriaceae on MacConkey agar. Cefotaxime-resistant isolates were screened by PCR and sequence analysis for presence of blaCTX-M, blaCMY, blaSHV, blaOXA and blaTEM gene families. Bacterial species were identified by MALDI-TOF MS analysis. PCR-negative isolates were tested by double disk synergy test for enhanced AmpC expression. 259 samples were screened, 126 samples were culture-positive on MCC, resulting in 352 isolates of which 327 isolates were Escherichia coli. Nine dogs were continuously positive during this study and 6 dogs were continuously negative. Monthly or weekly shifts in fecal shedding were observed in 23 dogs. Genotyping showed high variety of ESBL genes and gene combinations at single and multiple consecutive sampling moments. ESBL genes blaCTX-M-1, blaCTX-M-14, blaCTX-M-15, blaSHV-12 and blaCMY-2 were most frequently found. Mean cfu of non-wild-type Enterobacteriaceae was 6.11×10(8) cfu/g feces. This study showed an abundance of ESBL-producing Enterobacteriaceae in dogs in the Netherlands, mostly in high concentrations. Fecal shedding showed to be highly dynamic over time which is important to consider when studying ESBL epidemiology

Raw pet food as a risk factor for shedding of extended-spectrum beta-lactamase-producing Enterobacteriaceae in household cats

Background: Close contact between pets and owners provides the opportunity for transmission of antimicrobial resistant organisms like extended-spectrum beta-lactamase (ESBL)/AmpC beta-lactamase (AmpC)-producing Enterobacteriaceae, posing a risk to public health. Objectives: To investigate whether raw feed is a risk factor for household cats to shed ESBL-producing Enterobacteriaceae, a cohort study was designed. Additionally, raw and non-raw commercial pet food products were screened for the presence of ESBL-producing Enterobacteriaceae. Methods: Weekly fecal samples of 17 cats in the control group and 19 cats in the exposed group were collected for three weeks and analyzed for the presence of ESBL-producing Enterobacteriaceae. Questionnaires were obtained to determine additional risk factors. Fecal samples were cultured on MacConkey agar supplemented with 1 mg/L cefotaxime. PCR and sequence analysis was used for screening for ESBL genes in suspected isolates. Pet food samples were cultured in LB broth supplemented with 1 mg/L cefotaxime and processed as described above. Results: In the cohort study, ESBL-producing bacteria were isolated from 3 of 51 (5.9%) samples in the control group compared to 37 of 57 (89.5%) samples in the exposed group. A significant association was found between ESBL shedding and feeding raw pet food products (OR = 31.5). No other risk factors were identified in this study. ESBL-producing Enterobacteriaceae were isolated from 14 of 18 (77.8%) raw pet food products and 0 of 35 non-raw pet food products. Conclusions: This study shows a strong association between shedding of ESBL-producing bacteria in household cats and feeding raw pet food. Raw pet food was often contaminated with ESBL-producing Enterobacteriaceae

ESBL and MLST characterization results of cohort study.

<p>ESBL and MLST characterization results of cohort study.</p

ESBL characterization results for raw pet food products.

<p>ESBL characterization results for raw pet food products.</p