Cutibacterium acnes biofilm forming clinical isolates modify the formation and structure of Staphylococcus aureus biofilms, increasing their susceptibility to antibiotics

Cutibacterium acnes (formally Propionibacterium acnes) is frequently identified within surgical device related infections. It is often co-isolated from infection sites with other opportunistic pathogens. Recent studies have demonstrated that C. acnes is able to form biofilms and when co-cultured with Staphylococcus spp. both inhibitory and stimulatory effects have been reported across several studies. Here, we investigated the biofilm-forming ability of 100 clinical C. acnes isolates from various infection sites in human patients, both deep tissue and superficial, followed by an investigation of how the supernatants of C. acnes cultures influenced the attachment and maturation of S. aureus NCTC 6571 biofilms. All of the C. acnes isolates were able to form biofilms in vitro, although biofilm biomass varied between isolates. Nineteen isolates were weakly adherent, 33 were moderately adherent and the majority (48) showed strong adherence. The presence of C. acnes sterile supernatants reduced the biomass of S. aureus cultures, with a > 90% reduction observed in the presence of several of the C. acnes isolates. We observed that this decrease was not due to C. acnes affecting S. aureus viability, nor due to the presence of propionic acid. Biofilm maturation was however delayed over a 24-hour period as was biofilm surface structure, although initial (up to 8 h) surface attachment was not affected. We hypothesis that this defective biofilm maturation is the cause of the observed biomass decrease. In turn, these altered biofilms showed a greater susceptibility to antibiotic treatments. In contrast the presence of C. acnes supernatant in planktonic (defined as a free moving, non-surface attached population within the liquid column) S. aureus cultures increased antibiotic tolerance, via a currently undefined mechanism. This study suggests that complex interactions between C. acnes and other opportunistic pathogens are likely to exist during colonisation and infection events. Further investigation of these interactions may lead to increased treatment options and a better prognosis for patients

First large-scale study of antimicrobial susceptibility data, and genetic resistance determinants, in Fusobacterium necrophorum highlighting the importance of continuing focused susceptibility trend surveillance

Objectives: The objective of the study was to explore antimicrobial resistance gene determinant, and phenotypic antibiotic susceptibility, data for Fusobacterium necrophorum from a collection of UK strains. In addition, antimicrobial resistance genes detected in publicly available assembled whole genome sequences were investigated for comparison.Methods: Three hundred and eighty five F. necrophorum strains (1982-2019) were revived from cryovials (Prolab). Subsequent to sequencing (Illumina) and quality checking, 374 whole genomes were available for analysis. These genomes, in addition to publicly available assembled F. necrophorum genetic data, were interrogated using BioNumerics (bioMérieux; v 8.1), for the presence of known antimicrobial resistance genes (ARGs). Agar dilution susceptibility results for 313 F. necrophorum isolates (2016-2021) were also examined.Results: The phenotypic antibiotic test data for the 313 contemporary strains demonstrated potential resistance to penicillin, without increased dosing, in only three isolates. Otherwise, all strains were susceptible to ceftriaxone, clindamycin, co-amoxiclav, meropenem, metronidazole, penicillin and piperacillin/tazobactam, using EUCAST (v 11.0) interpretive guidance. The tet(O), tet(M), tet(40), aph(3’)-III, ant(6)-la and blaOXA-85 ARGs were present in publicly available assembled genomes. tet(M), tet(32), erm(A) and erm(B) were found within the UK strains, with correspondingly raised clindamycin and tetracycline minimum inhibitory concentrations.Conclusions: Current antibiotics recommended for the treatment of infections caused by F. necrophorum, including Lemierre’s disease, are likely to be effective in most cases. However, with evidence of potential ARG transmission from oral bacteria, and the detection of a transposon-mediated beta-lactamase resistance determinant in F. necrophorum, surveillance of both phenotypic and genotypic antimicrobial susceptibility trends must continue, and increase.<br/

Outbreak of Clostridium histolyticum infections in injecting drug users in England and Scotland

Clostridial infections in injecting drug users in the United Kingdom are a relatively new phenomenon that came to light in 2000 when cases of serious illness and deaths due to Clostridium novyi were recorded. In the period December 2003 to April 2004, the Anaerobe Reference Laboratory received twelve referrals of an extremely rare isolate, Clostridium histolyticum, from cases of infection in injecting drug users submitted from nine different hospitals in England and Scotland. Molecular typing of these isolates by two different methods of pulsed-field gel electrophoresis and PCR ribotyping revealed they are all indistinguishable, indicating a common source of the infections, most probably a batch of heroin that was recently distributed across the UK

Outbreak of Clostridium histolyticum infections in injecting drug users in England and Scotland

Clostridial infections in injecting drug users in the United Kingdom are a relatively new phenomenon that came to light in 2000 when cases of serious illness and deaths due to Clostridium novyi were recorded. In the period December 2003 to April 2004, the Anaerobe Reference Laboratory received twelve referrals of an extremely rare isolate, Clostridium histolyticum, from cases of infection in injecting drug users submitted from nine different hospitals in England and Scotland. Molecular typing of these isolates by two different methods of pulsed-field gel electrophoresis and PCR ribotyping revealed they are all indistinguishable, indicating a common source of the infections, most probably a batch of heroin that was recently distributed across the UK

Antibiotic susceptibilities of Gram-positive anaerobic cocci: results of a sentinel study in England and Wales

Objective: A sentinel study was carried out to determine the antimicrobial susceptibilities of Gram-positive anaerobic cocci (GPAC) freshly isolated from clinical material in diagnostic laboratories in England and Wales. Methods: A total of 113 GPAC isolates consisting predominantly of current or former members of the genus Peptostreptococcus was obtained from 17 sentinel laboratories in England and one in Wales. Minimum inhibitory concentrations (MICs) of 10 antimicrobial agents were determined by the Etest method. The agents tested were: penicillin, tetracycline, erythromycin, cefoxitin, clindamycin, chloramphenicol, imipenem, co-amoxiclav, piperacillin/tazobactam and metronidazole. MIC50 and MIC90 values for each drug-species combination were calculated whenever suitable numbers of each species were obtained. Results: Excellent spectra of activity (0% resistance) against GPAC were seen for metronidazole, piperacillin/tazobactam, cefoxitin, imipenem and chloramphenicol. Low degrees of resistance to co-amoxiclav (3.5%), clindamycin (7.1%), penicillin (7.1%) and significant degrees of resistance to tetracycline (41.6%) and erythromycin (27.4%) were detected. Some examples of putative macrolide-lincosamide linked resistance were noted in seven (6.2%) isolates of GPAC. Conclusion: This study is one of the largest susceptibility studies specificall

Surface bacteriology of venous leg ulcers and healing outcome

AIM: Bacteria can be cultured from all venous leg ulcers (VLUs) regardless of healing status, and the significance of a positive swab result in non-clinically infected ulcers is unknown. The aim of this study was to characterise the bacteriological flora of VLUs by routine culture to determine whether the data generated had prognostic value. METHODS: The ulcers of 178 patients were sampled weekly for 12 weeks and healing outcome monitored while the limb was treated with graduated compression. Wound bacteriology was assessed using culture methodology standardised to ensure data reproducibility. RESULTS: 153 individual bacterial species were identified. The species most frequently found were Staphylococcus aureus (64.3% of assessments), Corynebacterium striatum (60.6%), Pseudomonas aeruginosa (32.6%), Helcococcus kunzii (22.0%), Finegoldia magna (21.4%) and Proteus mirabilis (16.1%). No single species or the presence of anaerobes and increasing diversity of bacterial species, previously thought to be predictive of impaired healing, was shown to be associated with healing outcome. The presence of C striatum was associated with healing outcome but not after adjusting for the known prognostic factors of wound area and duration. CONCLUSION: Routine bacteriological culture analysis of the VLU wound surface may be used to identify diverse flora in all ulcers. However, the data generated are of no additional value as a prognostic indicator of healing outcome. The presence of C striatum may represent colonisation of non-healing VLU by normal skin flora

Comparing identification of clinically relevant Prevotella species by VITEK MS and MALDI biotyper

In this multicenter study, we aimed to evaluate the performance of MALDI Biotyper and VITEK MS, for identification of Prevotella species. Three hundred and fourteen clinical isolates, collected in eight European countries between January 2014 and April 2016, were identified at the collecting sites by MALDI Biotyper (versions 3.0 and 3.1) and then reidentified by VITEK MS (version 3.0) in the central laboratory. 16S rRNA gene sequencing was used as a standard method. According to sequence analysis, the 314 Prevotella strains belonged to 19 species. MALDI Biotyper correctly identified 281 (89.5%) isolates to the species level and 33 (10.5%) only at the genus level. VITEK MS correctly identified 253 (80.6%) isolates at the species level and 276 (87.9%) isolates at the genus level. Thirty-three isolates belonging to P. bergensis, P. conceptionensis, P. corporis, P. histicola, and P. nanciensis, unavailable in the VITEK MS 3.0 database, were resulted in genus level or no identification. Six Prevotella strains, belonged to P. veroralis, P. timonensis, and P. conceptionensis not represented in the MALDI Biotyper system database, were misidentified at the genus level. In conclusion, both VITEK MS and MALDI Biotyper provided reliable and rapid identification. However, the permanent extension of the databases is needed

A multicenter survey of antimicrobial susceptibility of Prevotella species as determined by Etest methodology

Knowledge about the antimicrobial susceptibility patterns of different Prevotella species is limited. The aim of this study was to determine the current antimicrobial susceptibility of clinical isolates of Prevotella species from different parts of Europe, Kuwait and Turkey. Activity of 12 antimicrobials against 508 Prevotella isolates, representing 19 species, were tested according to Etest methodology. EUCAST, CLSI and FDA guidelines were used for susceptibility interpretations. All Prevotella species were susceptible to piperacillin/tazobactam, imipenem, meropenem, tigecycline and metronidazole. Ampicillin/sulbactam and cefoxitin also showed good activity. Ampicillin, clindamycin, tetracycline and moxifloxacin were less active; 51.2%, 33.7%, 36.8% and 18.3% of isolates were non-susceptible, respectively. A total of 49 (9.6%) isolates were resistant to three or more antimicrobials. Prevotella bivia was the most prevalent species (n = 118) and accounted for most of the multidrug-resistant isolates. In conclusion, the level of nonsusceptibility to antimicrobials, which may be used for treatment of infections involving Prevotella species, are a cause of concern. This data emphasizes the need for species level identification of clinical Prevotella isolates and periodic monitoring of their susceptibility to guide empirical treatment. (C) 2018 Published by Elsevier Ltd