Staphylococcal biofilms are among the main causes of chronic implant-associated infections. We have recently suggested that their transformation into viable but non-culturable (VBNC) forms (i.e. ...forms capable of resuscitation) could be responsible for the recurrent symptoms. This work aims to establish whether Staphylococcus aureus biofilms can give rise to VBNC forms capable of being resuscitated in suitable environmental conditions, the role of different stressors in inducing the VBNC state and the conditions favouring resuscitation.
S. aureus 10850 biofilms were exposed to different concentrations of antibiotic (vancomycin or quinupristin/dalfopristin) and/or to nutrient depletion until loss of culturability. The presence of viable cells and their number were examined by epifluorescence microscopy and flow cytometry. Gene expression was measured by real-time PCR. Resuscitation ability was tested by growth in rich medium containing antioxidant factors.
Viable subpopulations were detected in all non-culturable biofilms. However, viable cell numbers and gene expression remained constant for 150 days from loss of culturability in cells from antibiotic-exposed biofilms, but not in those that had only been starved. Resuscitation was obtained in rich medium supplemented with 0.3% sodium pyruvate or with 50% filtrate of a late-log culture.
Our findings demonstrate that S. aureus can enter the VBNC state in infectious biofilms. The presence of vancomycin or quinupristin/dalfopristin can inadvertently induce a true VBNC state or its persistence in S. aureus cells embedded in biofilms, supporting previous findings on the role of staphylococcal biofilms in recurrent infections.
Biofilms cause chronic infections in tissues or by developing on the surfaces of medical devices. Biofilm infections persist despite both antibiotic therapy and the innate and adaptive defence ...mechanisms of the patient. Biofilm infections are characterized by persisting and progressive pathology due primarily to the inflammatory response surrounding the biofilm. For this reason, many biofilm infections may be difficult to diagnose and treat efficiently. It is the purpose of the guideline to bring the current knowledge of biofilm diagnosis and therapy to the attention of clinical microbiologists and infectious disease specialists. Selected hallmark biofilm infections in tissues (e.g. cystic fibrosis with chronic lung infection, patients with chronic wound infections) or associated with devices (e.g. orthopaedic alloplastic devices, endotracheal tubes, intravenous catheters, indwelling urinary catheters, tissue fillers) are the main focus of the guideline, but experience gained from the biofilm infections included in the guideline may inspire similar work in other biofilm infections. The clinical and laboratory parameters for diagnosing biofilm infections are outlined based on the patient’s history, signs and symptoms, microscopic findings, culture-based or culture-independent diagnostic techniques and specific immune responses to identify microorganisms known to cause biofilm infections. First, recommendations are given for the collection of appropriate clinical samples, for reliable methods to specifically detect biofilms, for the evaluation of antibody responses to biofilms, for antibiotic susceptibility testing and for improvement of laboratory reports of biofilm findings in the clinical microbiology laboratory. Second, recommendations are given for the prevention and treatment of biofilm infections and for monitoring treatment effectiveness. Finally, suggestions for future research are given to improve diagnosis and treatment of biofilm infections.
Aims
Multidrug‐resistant Klebsiella pneumoniae has become a relevant healthcare‐associated pathogen. Capsule, type 1 and 3 fimbriae (mrkA gene), type 2 quorum‐sensing system (luxS), synthesis of ...D‐galactan I (wbbM), LPS transport (wzm) and poly‐beta‐1,6‐N‐acetyl‐D‐glucosamine (pgaA) seem involved in K. pneumoniae biofilm. Nonenzymatic antibiotic resistance is related to nonexpression or mutation of porins (OmpK35 and OmpK36), and efflux pump (acrB) overexpression. The aim of this study was to analyse some virulence factors of K. pneumoniae isolates, and to evaluate possible correlations between their antibiotic resistance profile and ability to form biofilm.
Methods and Results
Quantitative biofilm production assay, congo red agar test and string test were performed on 120 isolates clustered in 56 extensively drug‐resistant (XDR), 40 MDR and 24 susceptible (S) strains. Nine representative strains were analysed by real‐time RT‐PCR for the expression of antibiotic resistance (OmpK35, OmpK36, acrB) and biofilm production genes (mrkA, luxS, pga, wbbM, wzm) during planktonic and sessile growth. XDR isolates showed a higher ability to form biofilm (91·07%) and to produce polysaccharides (78·57%) when compared to MDR and S strains. In biofilm‐growing XDR strains, seven of eight genes were upregulated, with the only exception of OmpK36.
Conclusions
XDR strains exhibited phenotypic and genotypic features supporting a significant growth as biofilm.
Significance and Impact of the Study
This study produces new findings that highlight a positive correlation between antibiotic resistance profile and biofilm‐forming ability in XDR K. pneumoniae strains. These new evidences might contribute to the progress in selection of therapeutic treatments of infections caused by K. pneumoniae resistant also to the ‘last line of defence’ antibiotics, that is, carbapenems.
Viable bacteria were sought in 44 Maki-negative biofilms from central venous catheters (CVCs) using epifluorescence microscopy after live/dead staining. Thirty (77%) samples contained viable but ...non-culturable (VBNC) cells; the majority were positive on real-time PCR specific for Staphylococcus epidermidis (one also for Staphylococcus aureus). Viable cells were significantly (p <0.01) associated with CVCs from febrile patients, three of whom showed S. epidermidis-positive blood cultures, suggesting that CVC-associated biofilms can be reservoirs for staphylococci in the VBNC state. The possible role of VBNC staphylococci in persistent infections related to medical devices requires further investigation.
Objective
To evaluate the ability of the probiotic strain Lactobacillus brevis CD2 to inhibit the opportunistic anaerobe Prevotella melaninogenica (PM1), a well‐known causative agent of ...periodontitis.
Materials and Methods
The inhibitory effect of Lactobacillus CD2 on Prevotella PM1 biofilm was assessed both by exposing the anaerobe to the supernatant of the probiotic strain and by growing the two strains to obtain single or mixed biofilms. The inhibitory effect of CD2 on PM1 was also checked by the agar overlay method.
Results
The development of PM1 biofilm was strongly affected (56% decrease in OD value) by the CD2 supernatant after 96 h. A dose‐dependent biofilm reduction was also observed at 1/10 and 1/100 dilutions of supernatant. Confocal microscopy on the mixed biofilms revealed the ability of CD2 to prevail on PM1, greatly reducing the biofilm of the latter.
Conclusions
It has been hypothesized a multifactorial nature of the inhibition mechanism, the strong adherence ability of CD2 strain together with the released metabolites presumably contributing to the reduction in the PM1 biofilm detected by confocal microscopy.
In recent years the employment of implantable medical devices has increased remarkably, notwithstanding that microbial infections are a frequent complication associated with their use. Different ...strategies have been attempted to overcome this problem, including the incorporation of antimicrobial agents into the device itself. In this study a new approach to obtain intrinsically antimicrobial materials was developed. Polymer anionomers containing Ag(I), Cu(II), Zn(II), Al(III) and Fe(III) were prepared by neutralization of a carboxylated polyurethane. In the case of the PEUA-Ag, PEUA-Fe and PEUA-Cu ionomers the ion aggregates behaved as reinforcing filler particles, increasing the mechanical properties of the systems in terms of hardness and strength at break over the pristine carboxylated polymer. With the exception of the Al-containing polymer, all the other experimented ionomers showed satisfactory antimicrobial properties. The best antibacterial effect was obtained with the silver ion-containing polymer, which inhibited
Staphylococcus epidermidis growth for up to 16
days. Ciprofloxacin was also adsorbed onto the above mentioned ionomers. A synergistic effect of the antibiotic and silver ions on bacterial growth inhibition was observed for at least 25
days.
VanA-type human (n = 69), animal (n = 49), and food (n = 36) glycopeptide-resistant enterococci (GRE) from different geographic areas were investigated to study their possible reservoirs and ...transmission routes. Pulsed-field gel electrophoresis (PFGE) revealed two small genetically related clusters, M39 (n = 4) and M49 (n = 13), representing Enterococcus faecium isolates from animal and human feces and from clinical and fecal human samples. Multilocus sequence typing showed that both belonged to the epidemic lineage of CC17. purK allele analysis of 28 selected isolates revealed that type 1 was prevalent in human strains (8/11) and types 6 and 3 (14/15) were prevalent in poultry (animals and meat). One hundred and five of the 154 VanA GRE isolates, encompassing different species, origins, and PFGE types, were examined for Tn1546 type and location (plasmid or chromosome) and the incidence of virulence determinants. Hybridization of S1- and I-CeuI-digested total DNA revealed a plasmid location in 98% of the isolates. Human intestinal and animal E. faecium isolates bore large (>150 kb) vanA plasmids. Results of PCR-restriction fragment length polymorphism and sequencing showed the presence of prototype Tn1546 in 80% of strains and the G-to-T mutation at position 8234 in three human intestinal and two pork E. faecium isolates. There were no significant associations (P > 0.5) between Tn1546 type and GRE source or enterococcal species. Virulence determinants were detected in all reservoirs but were significantly more frequent (P < 0.02) among clinical strains. Multiple determinants were found in clinical and meat Enterococcus faecalis isolates. The presence of indistinguishable vanA elements (mostly plasmid borne) and virulence determinants in different species and PFGE-diverse populations in the presence of host-specific purK housekeeping genes suggested that all GRE might be potential reservoirs of resistance determinants and virulence traits transferable to human-adapted clusters.
Summary Background Silver-impregnated central venous catheters (CVCs) have been proposed as a means for preventing CVC colonization and related bloodstream infections (CRBSIs). Aim To evaluate the ...efficacy of CVCs impregnated with silver nanoparticles in a large group of critically ill patients. Methods A prospective, randomized clinical trial was conducted in five intensive care units (ICUs). Three hundred and thirty-eight adult patients requiring CVCs between April 2006 and November 2008 were randomized to receive AgTive silver-nanoparticle-impregnated (SC) or conventional (CC) CVCs. Primary endpoints were CVC colonization (growth of ≥15 colony-forming units from the catheter tip) and incident CRBSIs (meeting the definitions of the Centers for Disease Control and Prevention). Infection-free time (days from initial CVC insertion to initial blood culture positivity) and ICU mortality rates were measured as secondary endpoints. Findings The SC group ( N = 135) and CC group ( N = 137) were similar in terms of clinical and laboratory parameters at baseline, reasons for ICU admission, complications during CVC insertion, and total time with CVC (mean ± standard deviation; SC 13 ± 24 vs CC 15 ± 37 days). No significant intergroup differences were found in CVC colonization rates (SC 32.6% vs CC 30%; P = 0.7), CRBSI incidence rates (3.36 infections per 1000 catheter-days in both groups), infection-free times (SC 13 ± 34 vs CC 12 ± 12 days; P = 0.85) or ICU mortality (SC 46% vs CC 43%; P = 0.7). Conclusion In critically ill patients, use of AgTive® silver-nanoparticle-impregnated CVCs had no significant effect on CVC colonization, CRBSI incidence or ICU mortality. These CVCs cannot be recommended as an adjunctive tool for control of CRBSIs.
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