Staphylococcus epidermidis bloodstream infections are a cause of septic shock in intensive care unit patients

OBJECTIVES

Staphylococcus epidermidis (SE) is a supposedly low-virulence agent, which may cause proven bloodstream infections (BSIs), with little-known consequences on intensive care unit (ICU) patients. We aimed at studying ICU patients diagnosed with BSIs caused by SE (SE-BSIs).

METHODS

We constituted a retrospective cohort in two medical ICUs. SE-BSIs were defined by two or more independent SE-positive blood cultures of the same strain, within 48 hours, without concurrent infection.

RESULTS

We included 59 patients; 58% were men (n = 34), with median age of 67 (interquartile range 60-74) years and a simplified acute physiology score II of 59 (36-74) points, and 56% were immunocompromised (n = 33). Among the 37 (63%) patients requiring norepinephrine initiation or increase at the onset of SE-BSI versus patients not requiring vasopressors (37%; n = 22), concomitant arterial lactate levels reached 2.8 (1.9-5.8) versus 1.5 (1.3-2.2) mmol/l (P <0.01), whereas the mean blood pressure was 49 (42-54) versus 61 (56-65) mm Hg (P = 0.01) and the mortality was 46% (n = 17) vs 14% (n = 3) at day 28 (P = 0.01), respectively. Regarding antibiotics, the susceptibility rates toward linezolid and vancomycin were 71% (n = 41/58) and 100% (n = 54/54), respectively. At the time of SE-BSI, all but one patient had a central venous access device.

CONCLUSION

This work highlights SE-BSIs as a cause of septic shock, mostly in immunocompromised ICU patients, with increasing concerns about resistance to antibiotics and central line management.

Skin microbiota secretomes modulate cutaneous innate immunity against Borrelia burgdorferi s.s

In Lyme borreliosis, the skin constitutes a major interface for the host, the bacteria and the tick. Skin immunity is provided by specialized immune cells but also by the resident cells: the keratinocytes and the fibroblasts. Discoveries on the role of the microbiome in the modulation of skin inflammation and immunity have reinforced the potential importance of the skin in vector-borne diseases. In this study, we analyzed in vitro the interaction of human primary keratinocytes and fibroblasts with Borrelia burgdorferi sensu stricto N40 in presence or absence of bacterial commensal supernatants. We aimed to highlight the role of resident skin cells and skin microbiome on the inflammation induced by B. burgdorferi s.s.. The secretomes of Staphylococcus epidermidis, Corynebacterium striatum and Cutibacterium acnes showed an overall increase in the expression of IL-8, CXCL1, MCP-1 and SOD-2 by fibroblasts, and of IL-8, CXCL1, MCP-1 and hBD-2 in the undifferentiated keratinocytes. Commensal bacteria showed a repressive effect on the expression of IL-8, CXCL1 and MCP-1 by differentiated keratinocytes. Besides the inflammatory effect observed in the presence of Borrelia on all cell types, the cutaneous microbiome appears to promote a rapid innate response of resident skin cells during the onset of Borrelia infection.

Evaluation of ceftolozane-tazobactam susceptibility on a French nationwide collection of Enterobacterales

OBJECTIVES

Ceftolozane-tazobactam (C/T) proved its efficacy for the treatment of infections caused by non-carbapenemase producing Pseudomonas aeruginosa and Enterobacterales. Here, we aimed to provide susceptibility data on a large series of Enterobacterales since the revision of EUCAST categorization breakpoints in 2020.

METHODS

First, C/T susceptibility was determined on characterized Enterobacterales resistant to third generation cephalosporins (3GCs) (extended spectrum β-lactamase [ESBL] production or different levels of AmpC overexpression) (n = 213) and carbapenem-resistant Enterobacterales (CRE) (n = 259), including 170 carbapenemase producers (CPE). Then, 1632 consecutive clinical Enterobacterales responsible for infection were prospectively collected in 23 French hospitals. C/T susceptibility was determined by E-test® (biomérieux) and broth microdilution (BMD) (Sensititre™, Thermo Scientific) to perform method comparison.

RESULTS

Within the collection isolates, 88% of 3GC resistant strains were susceptible to C/T, with important variation depending on the resistance mechanism: 93% vs. 13% susceptibility for CTX-M and SHV-ESBL producers, respectively. Only 20% of the CRE were susceptible to C/T. Among CPE, 80% of OXA-48-like producers were susceptible to C/T, whereas all metallo-β-lactamase producers were resistant. The prospective study revealed that 95.6% of clinical isolates were susceptible to C/T. Method comparison performed on these 1632 clinical isolates demonstrated 99% of categorization agreement between MIC to C/T determined by E-test® in comparison with the BMD (reference) and only 74% of essential agreement.

CONCLUSION

Overall, C/T showed good activity against wild-type Enterobacterales, AmpC producers, and ESBL-producing Escherichia coli but is less active against ESBL-producing Klebsiella pneumoniae, and CRE. E-test® led to an underestimation of the MICs in comparison to the BMD reference.

[Antimicrobial resistance patterns in pediatric febrile urinary tract infection and empirical antibacterial therapy. An epidemiological study in secondary and tertiary care centers in the north-east of France in 2019-2020]

BACKGROUND

Febrile urinary tract infection (UTI) is a common health issue in pediatrics that can lead to serious infectious and renal complications, it requires early diagnosis and a targeted use of antibiotics. The aim of our study was to describe local bacterial agents causing febrile UTIs and their resistance patterns and confront the results with currently used empirical antibacterial therapy in pediatrics emergency departments in Strasbourg and Saverne.

PATIENTS AND METHODS

We used billing codes (international classification of diseases) to identify all inpatients treated for febrile UTIs in two French pediatric emergency departments between January 2019 and December 2020. Microbial results of urine cultures were retrieved from the laboratory information system.

RESULTS

Among 214 microbial results from 208 patients, the distribution of uropathogens was 82% Escherichia coli, with extended-spectrum beta-lactamase in 2.8%, 7% Enterococcus faecalis, 5% Klebsiella, 2% Proteus mirabilis. E. coli was resistant respectively to amoxicillin, amoxicillin/clavulanic acid and cotrimoxazol in 43, 33 and 14% of samples. A third-generation cephalosporin administered intravenously was mainly used (98%) as empirical treatment. Less than 2% of patients were treated with oral cephalosporin from the start.

CONCLUSION

We present the spectrum of uropathogens and susceptibility test results in pediatric UTIs as well as the susceptibility pattern of E. coli, a local treatment protocol was designed based on our results in conformity with national guidelines.

Antimicrobial Resistance in Enterobacterales Recovered from Urinary Tract Infections in France

In the context of increasing antimicrobial resistance in Enterobacterales, the management of these UTIs has become challenging. We retrospectively assess the prevalence of antimicrobial resistance in Enterobacterales isolates recovered from urinary tract samples in France, between 1 September 2017, to 31 August 2018. Twenty-six French clinical laboratories provided the susceptibility of 134,162 Enterobacterales isolates to 17 antimicrobials. The most frequent species were E. coli (72.0%), Klebsiella pneumoniae (9.7%), Proteus mirabilis (5.8%), and Enterobacter cloacae complex (2.9%). The overall rate of ESBL-producing Enterobacterales was 6.7%, and ranged from 1.0% in P. mirabilis to 19.5% in K. pneumoniae, and from 3.1% in outpatients to 13.6% in long-term care facilities. Overall, 4.1%, 9.3% and 10.5% of the isolates were resistant to cefoxitin, temocillin and pivmecillinam. Cotrimoxazole was the less active compound with 23.4% resistance. Conversely, 4.4%, 12.9%, and 14.3% of the strains were resistant to fosfomycin, nitrofurantoin, and ciprofloxacin. However, less than 1% of E. coli was resistant to fosfomycin and nitrofurantoin. We identified several trends in antibiotics resistances among Enterobacterales isolates recovered from the urinary tract samples in France. Carbapenem-sparing drugs, such as temocillin, mecillinam, fosfomycin, cefoxitin, and nitrofurantoin, remained highly active, including towards ESBL-E.

Broth Microdilution and Gradient Diffusion Strips vs. Reference Agar Dilution Method: First Evaluation for Clostridiales Species Antimicrobial Susceptibility Testing

Antimicrobial susceptibility testing of anaerobes is challenging. Because MIC determination is recommended by both CLSI and EUCAST, commercial broth microdilution and diffusion strip tests have been developed. The reliability of broth microdilution methods has not been assessed yet using the agar dilution reference method. In this work, we evaluated two broth microdilution kits (MICRONAUT-S Anaerobes^® MIC and Sensititre Anaerobe MIC^®) and one gradient diffusion strip method (Liofilchem^®) for antimicrobial susceptibility testing of 47 Clostridiales isolates (Clostridium, Clostridioides and Hungatella species) using the agar dilution method as a reference. The evaluation focused on comparing six antimicrobial molecules available in both microdilution kits. Analytical performances were evaluated according to the Food and Drug Administration (FDA) recommendations. Essential agreements (EA) and categorical agreements (CA) varied greatly according to the molecule and the evaluated method. Vancomycin had values of essential and categorical agreements above 90% for the three methods. The CA fulfilled the FDA criteria for three major molecules in the treatment of Gram-positive anaerobic infections (metronidazole, piperacillin/tazobactam and vancomycin). The highest rate of error was observed for clindamycin. Multicenter studies are needed to further validate these results.

Effects of topical corticosteroids and lidocaine on Borrelia burgdorferi sensu lato in mouse skin: potential impact to human clinical trials

Lyme borreliosis is the most prevalent vector-borne disease in northern hemisphere. Borrelia burgdorferi sensu lato spirochetes are transmitted by Ixodes species ticks. During a blood meal, these spirochetes are inoculated into the skin where they multiply and often spread to various target organs: disseminated skin sites, the central nervous system, the heart and large joints. The usual diagnosis of this disease relies on serological tests. However, in patients presenting persistent clinical manifestations, this indirect diagnosis is not capable of detecting an active infection. If the serological tests are positive, it only proves that exposure of an individual to Lyme spirochetes had occurred. Although culture and quantitative PCR detect active infection, currently used tests are not sensitive enough for wide-ranging applications. Animal models have shown that B. burgdorferi persists in the skin. We present here our targeted proteomics results using infected mouse skin biopsies that facilitate detection of this pathogen. We have employed several novel approaches in this study. First, the effect of lidocaine, a local anesthetic used for human skin biopsy, on B. burgdorferi presence was measured. We further determined the impact of topical corticosteroids to reactivate Borrelia locally in the skin. This local immunosuppressive compound helps follow-up detection of spirochetes by proteomic analysis of Borrelia present in the skin. This approach could be developed as a novel diagnostic test for active Lyme borreliosis in patients presenting disseminated persistent infection. Although our results using topical corticosteroids in mice are highly promising for recovery of spirochetes, further optimization will be needed to translate this strategy for diagnosis of Lyme disease in patients.

Skin Interface, a Key Player for Borrelia Multiplication and Persistence in Lyme Borreliosis

The skin plays a key role in vector-borne diseases because it is the site where the arthropod coinoculates pathogens and its saliva. Lyme borreliosis, particularly well investigated in this context, is a multisystemic infectious disease caused by Borrelia burgdorferi sensu lato and transmitted by the hard tick Ixodes. Numerous in vitro studies were conducted to better understand the role of specific skin cells and tick saliva in host defense, vector feeding, and pathogen transmission. The skin was also evidenced in various animal models as the site of bacterial multiplication and persistence. We present the achievements in this field as well as the gaps that impede comprehensive knowledge of the disease pathophysiology and the development of efficient diagnostic tools and vaccines in humans.

Identification of closely related Ixodes species by protein profiling with MALDI-TOF mass spectrometry

Ticks are vectors of infectious diseases of major importance in human and veterinary medicine. For epidemiological studies, accurate identification of ticks is crucial to define their potential role as vectors and to develop control and prevention strategies. Although morphological and molecular methods are widely used to identify ticks, an innovative approach using MALDI-TOF MS technology recently emerged as an alternative tool. Previous works showed that MALDI-TOF MS was highly effective in identifying ticks, but these works mainly tested tick specimens of different genera. To confirm the accuracy of this new tool for tick identification, nine closely related tick species belonging to the Ixodes genus were analysed, specimens of the Dermacentor reticulatus species were also included in the analysis as an outer group. Three of the species used for the present study belonged to the I. ricinus species complex, which are known to transmit Borrelia burgdorferi sensu lato, the causative agent of Lyme borreliosis. A total of 246 tick specimens were submitted to MALDI-TOF MS analysis, and two body parts (half-idiosoma and four legs) were individually investigated. For each body part, intraspecies reproducibility and interspecies specificity of the MS profiles were determined. The profile analysis revealed that the main determinant for spectra clustering was the tick species for both legs and half-idiosoma. For each body part, a reference database of spectra was set up including 2 to 5 specimens per species randomly selected, and genotyped using 16s rDNA and COI genes to confirm their morphological identification. Both created spectral databases were individually blind tested with their respective body part using the remaining specimens, which were correctly identified in 98.5% of the cases. MALDI-TOF MS is a reliable tool for tick identification, including specimens belonging to closely related species and hardly distinguishable using morphology. The 4-legs as well as the half-idiosoma of ticks can now be applied for specimen identification using two different databases. The combined use of these two body parts improves the rate of tick identification and their confidence level.

Unconventional diagnostic tests for Lyme borreliosis: a systematic review

BACKGROUND

Lyme borreliosis (LB) diagnosis currently relies mainly on serological tests and sometimes PCR or culture. However, other biological assays are being developed to try to improve Borrelia-infection diagnosis and/or monitoring.

OBJECTIVES

To analyse available data on these unconventional LB diagnostic assays through a systematic literature review.

METHODS

We searched PubMed and Cochrane Library databases according to the PRISMA-DTA method and the Cochrane Handbook for Systematic Reviews of Interventions. We analysed controlled and uncontrolled studies (published 1983-2018) on biological tests for adults to diagnose LB according to the European Study Group for Lyme Borreliosis or the Infectious Diseases Society of America definitions, or identify strongly suspected LB. Two independent readers evaluated study eligibility and extracted data from relevant study reports; a third reader analysed full texts of papers to resolve disagreements. The quality of each included study was assessed with the QUADAS-2 evaluation scale.

RESULTS

Forty studies were included: two meta-analyses, 25 prospective controlled studies, five prospective uncontrolled studies, six retrospective controlled studies and two case reports. These biological tests assessed can be classified as: (i) proven to be effective at diagnosing LB and already in use (CXCL-13 for neuroborreliosis), but not enough to be standardized; (ii) not yet used routinely, requiring further clinical evaluation (CCL-19, OspA and interferon-α); (iii) uncertain LB diagnostic efficacy because of controversial results and/or poor methodological quality of studies evaluating them (lymphocyte transformation test, interferon-γ, ELISPOT); (iv) unacceptably low sensitivity and/or specificity (CD57⁺ natural killer cells and rapid diagnostic tests); and (v) possible only for research purposes (microscopy and xenodiagnoses).

DISCUSSION

QUADAS-2 quality assessment demonstrated high risk of bias in 25/40 studies and uncertainty regarding applicability for 32/40, showing that in addition to PCR and serology, several other LB diagnostic assays have been developed but their sensitivities and specificities are heterogeneous and/or under-evaluated or unassessed. More studies are warranted to evaluate their performance parameters. The development of active infection biomarkers would greatly advance LB diagnosis and monitoring.

Bone penetration of daptomycin in diabetic patients with bacterial foot infections

OBJECTIVES

Daptomycin has shown clinical efficacy in diabetic foot infections (DFI). However, only limited data are available on its bone penetration in this particular population. The aim of this study was to determine daptomycin bone concentrations in patients with DFI undergoing surgery after multiple daptomycin infusions and to determine bone daptomycin inhibitory quotients (IQs) for the predominant gram-positive species involved in DFI.

METHODS

Fourteen adult patients hospitalized with DFI treated with daptomycin and requiring surgical bone debridement and amputation were included in this single-centre prospective study. Daptomycin concentrations in serum and bone were determined by HPLC at steady state. Bone IQs were then calculated according to different minimum inhibitory concentrations (MICs; range 0.25-4mg/l) that are representative of the main MICs for Staphylococcus aureus, coagulase-negative staphylococci (CoNS), and Enterococcus sp populations.

RESULTS

Residual and peak concentrations varied from 4.5mg/l to 39.9mg/l and from 31.8mg/l to 110.9mg/l, respectively. Bone daptomycin concentrations at the moment of surgery varied from 1.2mg/l to 17mg/l. Up to a MIC of 1mg/l, which is the epidemiological cut-off value (ECOFF) and breakpoint value for S. aureus and CoNS, all bone daptomycin IQs were positive. The highest bone IQs were observed with Staphylococcus species. Calculated bone IQs for Enterococcus species were often weak at MIC values near the ECOFF.

CONCLUSIONS

Daptomycin penetrates bone well in patients treated for DFI. At an initially recommended dosage of 6mg/kg, bone concentrations are likely to be effective against staphylococcal infections and infections due to low-MIC Enterococcus.

Characteristics and clinical outcomes after treatment of a national cohort of PCR-positive Lyme arthritis

OBJECTIVES

To describe the clinical and microbiological characteristics and outcomes after antibiotic treatment of a national cohort of patients with Lyme arthritis confirmed by PCR testing on synovial fluid and by serology, when available.

METHODS

Using the French National Reference Center for Borrelia database, patients with a positive PCR on synovial fluid for Borrelia were identified. Patient clinical and biological characteristics were reviewed from patient records. Long-term outcomes after treatment were studied through a questionnaire and with follow-up data.

RESULTS

Among 357 synovial fluid testing by PCR between 2010 and 2016, 37 (10.4%) were positive for Borrelia. Patients' median age was 36 years (range 6-78) with 61% of men and 28% patients under 18. The presentation was monoarticular in 92% and the knee was involved in 97%. Contrary to the Borrelia species repartition in European ticks, B. burgdorferi sensu stricto was the most prevalent species found in synovial fluid (54%) followed by B. azfelii (29%) and B. garinii (17%). Antibiotic treatments were mainly composed of doxycycline (n = 24), ceftriaxone (n = 10) and amoxicillin (n = 6), for a median duration of 4 weeks (range 3-12). Despite a properly conducted treatment, 34% of patients (n = 12) developed persistent synovitis for at least 2 months (median duration 3 months, range 2-16). Among those, 3 developed systemic inflammatory oligo- or polyarthritis in previously unaffected joints with no signs of persistent infection (repeated PCR testing negative), which mandated Disease-Modifying Antirheumatic Drugs (DMARD) introduction, leading to remission.

CONCLUSION

In France and contrary to ticks ecology, Lyme arthritis is mainly caused by B. burgdorferi sensu stricto. Despite proper antibiotic therapy, roughly one third of patients may present persistent inflammatory synovitis and a small proportion may develop systemic arthritis. In such cases, complete remission can be reached using DMARD.

Bacteriological sampling of peritoneal dialysis fluids. How to limit negative-culture peritonitis rate?

Peritonitis is a major and serious complication in terms of morbi-mortality for patients treated with peritoneal dialysis. Their microbiological diagnosis is challenging for both the detection of the etiological agents and in interpreting positive cultures. Many microorganisms can cause this infection; usual micro-organisms such as coagulase-negative staphylococci or Enterobacteriaceae, but also ‘atypical’ bacteria, which culture or detection, is more tedious can be found. To identify the responsible bacteria, molecular biology and culture techniques can be set up. Molecular biology (particularly the sequencing of the universal 16s rDNA gene) makes it possible to identify atypical agents, but antimicrobial susceptibility testing cannot be performed following these technics. The culture of peritoneal dialysis fluids remains the ‘gold-standard’ for the diagnosis of these infections. Nevertheless this must be optimized to enhance its sensitivity. The etiological diagnosis of peritonitis in patients treated with peritoneal dialysis may be difficult, but modern microbiology combined with a bacterioclinical discussion allow the identification of the microorganism responsible for the infection in the great majority of the cases.

Homogeneous Inflammatory Gene Profiles Induced in Human Dermal Fibroblasts in Response to the Three Main Species of Borrelia burgdorferi sensu lato

In Lyme borreliosis, the skin is the key site for bacterial inoculation by the infected tick and for cutaneous manifestations. We previously showed that different strains of Borrelia burgdorferi sensu stricto isolated from tick and from different clinical stages of the Lyme borreliosis (erythema migrans, and acrodermatitis chronica atrophicans) elicited a very similar transcriptional response in normal human dermal fibroblasts. In this study, using whole transcriptome microarray chips, we aimed to compare the transcriptional response of normal human dermal fibroblasts stimulated by 3 Borrelia burgdorferi sensu lato strains belonging to 3 main pathogenic species (B. afzelii, B. garinii and B. burgdorferi sensu stricto) in order to determine whether “species-related” inflammatory pathways could be identified. The three Borrelia strains tested exhibited similar transcriptional profiles, and no species-specific fingerprint of transcriptional changes in fibroblasts was observed. Conversely, a common core of chemokines/cytokines (CCL2, CXCL1, CXCL2, CXCL6, CXCL10, IL-6, IL-8) and interferon-related genes was stimulated by all the 3 strains. Dermal fibroblasts appear to play a key role in the cutaneous infection with Borrelia, inducing a homogeneous inflammatory response, whichever Borrelia species was involved.

Comparative Activity of Ciprofloxacin, Levofloxacin and Moxifloxacin against Klebsiella pneumoniae, Pseudomonas aeruginosa and Stenotrophomonas maltophilia Assessed by Minimum Inhibitory Concentrations and Time-Kill Studies

The aim of this study was to compare the in vitro susceptibility of Klebsiella pneumoniae, Pseudomonas aeruginosa and Stenotrophomonas maltophilia to three fluoroquinolones. The minimum inhibitory concentrations (MICs) to ciprofloxacin, levofloxacin and moxifloxacin were examined by E-test^® for a total of 40 K. pneumoniae strains, 40 S. maltophilia strains and 40 P. aeruginosa strains. Then, the bactericidal activity of these fluoroquinolones was investigated on five strains of each bacterial species by means of time-kill curves. For K. pneumoniae and P. aeruginosa, the distance of the measured MIC from the clinical break-point is a good indicator of the bactericidal activity for ciprofloxacin and levofloxacin as obtained in our experiments. The lower the MIC, the better the bactericidal activity in term of CFU Log decreases. If MIC of ciprofloxacin and levofloxacin against the considered bacteria are far from clinical breakpoint, these two antibiotics are equivalent. According to our MIC₅₀ and modal MIC, the breakpoints of both ciprofloxacin and levofloxacin seem to be somewhat high and data suggest reducing them. On S. maltophilia, none of the tested antibiotics showed a satisfactory activity.

Moraxella osloensis, an emerging pathogen of endocarditis in immunocompromised patients?

We report two cases of endocarditis due to Moraxella osloensis. Only one previous case of such infection has been described. These infections occurred in immunocompromised patients (B-cell chronic lymphocytic leukaemia and kidney graft associated with Hodgkin's disease) and both patients had a favourable outcome with a complete cure of their infectious endocarditis. This bacterium could be an emerging pathogen revealed by MALDI-TOF. Indeed, its characterisation within the Moraxella group by use of biochemistry-based methods is difficult. Moreover, this strain could be particularly involved in immunocompromised patients.

Mobile insertion cassette elements found in small non-transmissible plasmids in Proteeae may explain qnrD mobilization

qnrD is a plasmid mediated quinolone resistance gene from unknown origin, recently described in Enterobacteriaceae. It encodes a pentapeptide repeat protein 36-60% different from the other Qnr (A, B, C, S and VC). Since most qnrD-positive strains were described as strains belonging to Proteus or Providencia genera, we hypothesized that qnrD originated in Proteeae before disseminating to other enterobacterial species. We screened 317 strains of Proteeae for qnrD and its genetic support by PCR. For all the seven qnrD-positive strains (4 Proteus mirabilis, 1 Proteus vulgaris and 2 Providencia rettgeri) the gene was carried onto a small non-transmissible plasmid, contrarily to other qnr genes that are usually carried onto large multi-resistant plasmids. Nucleotide sequences of the qnrD-bearing plasmids were 96% identical. Plasmids contained 3 ORFs apart from qnrD and belonged to an undescribed incompatibility group. Only one plasmid, in P. vulgaris, was slightly different with a 1,568-bp insertion between qnrD and its promoter, leading to absence of quinolone resistance. We sought for similar plasmids in 15 reference strains of Proteeae, but which were tested negative for qnrD, and found a 48% identical plasmid (pVERM) in Providencia vermicola. In order to explain how qnrD could have been inserted into such native plasmid, we sought for gene mobilization structures. qnrD was found to be located within a mobile insertion cassette (mic) element which sequences are similar to one mic also found in pVERM. Our conclusions are that (i) the small non-transmissible qnrD-plasmids described here may result from the recombination between an as-yet-unknown progenitor of qnrD and pVERM, (ii) these plasmids are maintained in Proteeae being a qnrD reservoir (iii) the mic element may explain qnrD mobilization from non-transmissible plasmids to mobilizable or conjugative plasmids from other Enterobacteriaceae, (iv) they can recombined with larger multiresistant plasmids conjugated in Proteeae.