Indwelling Medical Devices Research Articles

Neurocognitive consequences of iatrogenicphthalate exposure during critical illness in children: a study of a development and validation cohort

Phthalates are chemical additives incorporated in PVC-based materials to make them more pliable. Intensive care management, especially in the pediatric setting, relies heavily on the use of soft and flexible indwelling medical devices. As phthalates are not chemically bound to these devices, they can leach during use [1,2]. Environmental phthalate exposure has been associated with attention deficit disorders in children [3,4].

The Biology of the Escherichia coli Extracellular Matrix.

Escherichia coli is one of the world's best-characterized organisms, because it has been extensively studied for over a century. However, most of this work has focused on E. coli grown under laboratory conditions that do not faithfully simulate its natural environments. Therefore, the historical perspectives on E. coli physiology and life cycle are somewhat skewed toward experimental systems that feature E. coli growing logarithmically in a test tube. Typically a commensal bacterium, E. coli resides in the lower intestines of a slew of animals. Outside of the lower intestine, E. coli can adapt and survive in a very different set of environmental conditions. Biofilm formation allows E. coli to survive, and even thrive, in environments that do not support the growth of planktonic populations. E. coli can form biofilms virtually everywhere: in the bladder during a urinary tract infection, on in-dwelling medical devices, and outside of the host on plants and in the soil. The E. coli extracellular matrix (ECM), primarily composed of the protein polymer named curli and the polysaccharide cellulose, promotes adherence to organic and inorganic surfaces and resistance to desiccation, the host immune system, and other antimicrobials. The pathways that govern E. coli biofilm formation, cellulose production, and curli biogenesis will be discussed in this article, which concludes with insights into the future of E. coli biofilm research and potential therapies.

In vitro antifungal activity and in vivo antibiofilm activity of cerium nitrate against Candida species.

The objective of this study was to clarify the antifungal properties of cerium, a lanthanide member, against Candida species. A comprehensive study with planktonic and sessile cells was performed. The ability of cerium nitrate (CN) to impair in vitro and in vivo biofilm formation was evaluated and its potential use in biofilm treatment was also evaluated. Forty-eight clinical isolates of different Candida species and the type strain ATCC 90028 were tested according to the protocol M27-A3. The MICs and minimum lethal concentrations were determined. A time-kill assay was performed and a cytometric kinetic study was performed using live/dead markers. Biofilm inhibition and biofilm susceptibility in the presence of cerium was evaluated by quantification of the biofilm metabolic activity and total biomass with XTT and crystal violet assays, respectively. CN in vivo efficacy as a coating for medical indwelling devices was evaluated for the first time for Candida parapsilosis, using a mouse subcutaneous foreign body model using polyurethane catheter segments. Scanning electron microscopy was used to assess biofilm architecture after CN treatment. The MICs for planktonic cells correlated with severe cellular metabolic activity impairment and membrane damage after 3 h of incubation. Moreover, CN efficiently prevented biofilm formation both in vitro and in vivo in segments of polyurethane catheters. At higher concentrations, it was also able to disorganize and almost eradicate preformed biofilms. Our results strongly suggest that CN application in the clinical setting might be effective in preventing the formation of biofilm-associated infections, namely through catheter coating and ultimately as an antimicrobial lock therapy.

Comparison between Ica Operon Expression and Biofilm Formation in Methicillin-Resistant Staphylococcus Aureus Isolated from Central Venous Catheters under Different Environmental Conditions

Background: Methicillin-resistant Staphylococcus aureus (MRSA) infections are complicated by the ability of the organism to grow in surface-adhered biofilms on a multitude of inert synthetic surfaces including those involving indwelling medical devices. Intensive care unit (ICU) patients using central venous catheters (CVCs) are particularly at risk of acquiring device-related infections, which involve biofilms. Objectives: This study was carried out to compare intercellular adhesion (ica) operon expression and biofilm formation in MRSA isolated from CVCs grown under different environmental conditions. Methodology: Seven hundred sixteen central venous catheters tips were tested for MRSA colonization. Semiquantitative measurements of biofilm formation were determined for all MRSA isolates grown under different environmental conditions: Brain heart infusion (BHI) medium, BHI supplemented with 4% sodium chloride (NaCl) and BHI supplemented with 1% glucose (Glu). The ica operon expression were compared in all MRSA isolates grown under different environmental conditions using RT-PCR. Results: The overall catheter tip colonization rate was 36.87%. Staphylococci were isolated from 56.06%. The distribution of the isolated Staphylococci was as follow: Staphylococcus epidermidis (S. epidermidis) 34.8%, Staphylococcus aureus (S. aureus) 12.12% and other Coagulase negative Staphylococci CoNS 9.09%. Out of 32 S.aureus isolates 9 were MRSA (28.125%). Under standard laboratory conditions in BHI medium 22.22% of MRSA isolates were capable of biofilm development. This number increases to 77.77% when grown in BHI supplemented with 1% glucose. In contrast, growth in BHI supplemented with 4% NaCl induces biofilm in 11.11%. Among the 9 MRSA isolates, growth in the presence of NaCl resulted in activation of ica transcription in 8 strains but failed to induce substantial biofilm development in any of these isolates [weak -but measurable- biofilm formation was detected in medium supplemented with NaCl by one strain]. Glucose-mediated induction of biofilm formation in the 9 MRSA isolates correlated with weakly to moderately increased ica operon expression in 6 isolates. Interestingly, ica operon transcription was more potently activated by NaCl than by glucose in all of the MRSA isolates examined except one strain. Conclusion: There appears to be little correlation between ica operon regulation and biofilm formation in MRSA, suggesting that the ica operon and polysaccharide intercellular adhesin, or poly-N- acetylglucosamine (PIA/PNAG) may not be required. for biofilm development in MRSA

Protein-based biofilm matrices in Staphylococci.

Staphylococcus aureus and Staphylococcus epidermidis are the most important etiological agents of biofilm associated-infections on indwelling medical devices. Biofilm infections may also develop independently of indwelling devices, e.g., in native valve endocarditis, bone tissue, and open wounds. After attachment to tissue or indwelling medical devices that have been conditioned with host plasma proteins, staphylococcal biofilms grow, and produce a specific environment which provides the conditions for cell–cell interaction and formation of multicellular communities. Bacteria living in biofilms express a variety of macromolecules, including exopolysaccharides, proteins, extracellular eDNA, and other polymers. The S. aureus surface protein C and G (SasC and SasG), clumping factor B (ClfB), serine aspartate repeat protein (SdrC), the biofilm-associated protein (Bap), and the fibronectin/fibrinogen-binding proteins (FnBPA and FnBPB) are individually implicated in biofilm matrix formation. In S. epidermidis, a protein named accumulation-associated protein (Aap) contributes to both the primary attachment phase and the establishment of intercellular connections by forming fibrils on the cell surface. In S. epidermidis, proteinaceous biofilm formation can also be mediated by the extracellular matrix binding protein (Embp) and S. epidermidis surface protein C (SesC). Additionally, multifunctional proteins such as extracellular adherence protein (Eap) and extracellular matrix protein binding protein (Emp) of S. aureus and the iron-regulated surface determinant protein C (IsdC) of S. lugdunensis can promote biofilm formation in iron-depleted conditions. This multitude of proteins intervene at different stages of biofilm formation with certain proteins contributing to biofilm accumulation and others mediating primary attachment to surfaces. This review examines the contribution of proteins to biofilm formation in Staphylococci. The potential to develop vaccines to prevent protein-dependent biofilm formation during staphylococcal infection is discussed.

Immobilization of proteases on chitosan for the development of films with anti-biofilm properties

Bacterial resistance due to biofilm formation—particularly Staphylococci biofilms—is associated with multiple problems in medical settings where biofilms can colonize medical indwelling devices and cause nosocomial infections. It was against this backdrop that we explored the anti-biofilm activities of a set of proteases against biofilm formation by Staphylococcus aureus, Listeria monocytogenes and Pseudomonas aeruginosa. The selected screened enzymes were immobilized on chitosan to obtain films with anti-biofilm activities. Immobilization efficiency was about 94% for protease from Bacillus licheniformis and reached up to 96% for Neutrase. In vitro assays performed in brain heart infusion (BHI) broth using the Biofilm Ring Test highlighted that immobilized enzymes were efficient against biofilms of Staphylococci cultures, especially protease from B. licheniformis and Neutrase from Bacillus amyloliquefaciens.

Detection of Biofilm Production and Antibiotic Resistance Pattern in Clinical Isolates from Indwelling Medical Devices

Microbial biofilms pose great threat for patients requiring indwelling medical devices (IMDs) as it is difficult to remove them. It is, therefore, crucial to follow an appropriate method for the detection of biofilms. The present study focuses on detection of biofilm formation among the isolates from IMDs. We also aimed to explore the antibiogram of biofilm producers. This prospective analysis included 65 prosthetic samples. After isolation and identification of bacteria following standard methodology, antibiogram of the isolates were produced following Kirby-Bauer disc diffusion method. Detection of biofilms was done by tube adherence (TA), Congo red agar and tissue culture plate (TCP) methods. Out of 67 clinical isolates from IMDs, TCP detected 31 (46.3 %) biofilm producers and 36 (53.7 %) biofilm non-producers. Klebsiella pneumoniae, Pseudomonas aeruginosa and Burkholderia cepacia complex were found to be the most frequent biofilm producers. The TA method correlated well with the TCP method for biofilm detection. Higher antibiotic resistance was observed in biofilm producers than in biofilm non-producers. The most effective antibiotics for biofilm producing Gram-positive isolates were Vancomycin and Tigecycline, and that for biofilm producing Gram-negative isolates were Polymyxin-B, Colistin Sulphate and Tigecycline. Nearly 46 % of the isolates were found to be biofilm producers. The antibiotic susceptibility pattern in the present study showed Amoxicillin to be an ineffective drug for isolates from the IMDs. For the detection of biofilm production, TA method can be an economical and effective alternative to TCP method.

Antibiotic Resistance Related to Biofilm Formation in Klebsiella pneumoniae.

The Gram-negative opportunistic pathogen, Klebsiella pneumoniae, is responsible for causing a spectrum of community-acquired and nosocomial infections and typically infects patients with indwelling medical devices, especially urinary catheters, on which this microorganism is able to grow as a biofilm. The increasingly frequent acquisition of antibiotic resistance by K. pneumoniae strains has given rise to a global spread of this multidrug-resistant pathogen, mostly at the hospital level. This scenario is exacerbated when it is noted that intrinsic resistance to antimicrobial agents dramatically increases when K. pneumoniae strains grow as a biofilm. This review will summarize the findings about the antibiotic resistance related to biofilm formation in K. pneumoniae.

The role of Staphylococcus epidermidis in neonatal sepsis: Guarding angel or pathogenic devil?

Neonatal late-onset sepsis (LOS) is a serious problem in neonatal intensive care. Coagulase-negative staphylococci, especially Staphylococcus epidermidis, have emerged as the predominant pathogen of LOS in very low birth weight (VLBW) infants, accounting for up to 77.9% of neonatal LOS in industrialized countries and 46.5% in some developing regions. VLBW neonates with indwelling medical devices are most susceptible for S. epidermidis sepsis, the incidence rate of which is approximately 25%. However, S. epidermidis primarily plays a commensal role on human host and is of evolutionary importance to newborns, by inhibiting virulent pathogens and educating the innate immune system. Recent advances in molecular microbiology show that S. epidermidis is a bacterial species equipped with remarkable genetic flexibility, and can employ a multitude of mechanisms to become adapted to the changing environment. Extrinsic factors in the neonatal ward, such as the interruption of skin barrier by medical devices and the selective pressure due to antibiotics, contribute to the conversion of S. epidermidis from a member of the skin microflora to an infectious agent. Furthermore, neonates are predisposed for S. epidermidis infections due to their distinct immunological characteristics. A better understanding of the dichotomy of S. epidermidis and the underlying mechanisms may inspire new anti-infectious strategies.

IsdC from Staphylococcus lugdunensis Induces Biofilm Formation under Low-Iron Growth Conditions

Staphylococcus lugdunensis is a coagulase-negative staphylococcus that is a commensal of humans and an opportunistic pathogen. It can cause a spectrum of infections, including those that are associated with the ability to form biofilm, such as occurs with endocarditis or indwelling medical devices. The genome sequences of two strains revealed the presence of orthologues of the ica genes that are responsible for synthesis of poly-N-acetylglucosamine (PNAG) that is commonly associated with biofilm in other staphylococci. However, we discovered that biofilm formed by a panel of S. lugdunensis isolates growing in iron-restricted medium was susceptible to degradation by proteases and not by metaperiodate, suggesting that the biofilm matrix comprised proteins and not PNAG. When the iron concentration was raised to 1 mM biofilm formation by all strains tested was greatly reduced. A mutant of strain N920143 lacking the entire locus that encodes iron-regulated surface determinant (Isd) proteins was defective in biofilm formation under iron-limited conditions. An IsdC-null mutant was defective, whereas IsdK, IsdJ, and IsdB mutants formed biofilm to the same level as the parental strain. Expression of IsdC was required both for the primary attachment to unconditioned polystyrene and for the accumulation phase of biofilm involving cell-cell interactions. Purified recombinant IsdC protein formed dimers in solution and Lactococcus lactis cells expressing only IsdC adhered to immobilized recombinant IsdC but not to IsdJ, IsdK, or IsdB. This is consistent with a specific homophilic interaction between IsdC molecules on neighboring cells contributing to accumulation of S. lugdunensis biofilm in vivo.

Staphylococcus aureus bloodstream infection in Australian hospitals: findings from a Victorian surveillance system

To determine the burden of disease and trend over time for rates of Staphylococcus aureus bloodstream (SAB) infections in Victorian health care services. Uniform data on all SAB infection events (methicillin-sensitive and methicillin-resistant isolates) were collected from all public and some private hospitals in Victoria using a standardised electronic data collection tool. Data were analysed for the period 1 January 2010 to 31 December 2012. Overall and quarterly aggregate SAB and methicillin-resistant S. aureus (MRSA) bloodstream infection rates per 10,000 occupied bed-days (OBDs); rates of health care-associated (HA) infections compared with a benchmark of no more than 2/10,000 OBDs. Data from 119 public and four private hospitals were analysed. The cumulative aggregate SAB infection rate was 1.0/10,000 OBDs (95% CI, 0.9-1.0/10,000 OBDs). Overall, 1335/3205 SAB infection events (41.7%) were health care-associated. Of these, 26.2% occurred within 48 hours of hospitalisation and were most frequently associated with an indwelling medical device. Quarterly HA-SAB infection rates diminished from 1.4 to 0.7/10,000 OBDs (P < 0.001). A median of four health care services each quarter exceeded the benchmark of 2.0/10,000 OBDs. HA-MRSA bloodstream infection rates diminished from 0.4 to 0.1/10,000 OBDs (P < 0.001), with a cumulative aggregate rate of 0.2/10,000 OBDs. Continuous surveillance for SAB infection showed a significant reduction in rates across Victoria during the first 3 years of a coordinated program. Early onset, device-related SAB infections are an important target for prevention strategies.

Anti-biofilm agents: recent breakthrough against multi-drug resistantStaphylococcus aureus

Staphylococcus aureus is a Gram-positive pathogen that causes potentially life-threatening nosocomial- and community-acquired infections, such as osteomyelitis and endocarditis. Staphylococcus aureus has the ability to form multicellular, surface-adherent communities called biofilms, which enables it to survive in various sources of stress, including antibiotics, nutrient limitations, heat shock, and immune responses. Biofilm-forming capacity is now recognized as an important virulence determinant in the development of staphylococcal device-related infections. In light of the projected increase in the numbers of elderly patients who will require semi-permanent indwelling medical devices such as artificial knees and hips, we can anticipate an expanded need for new agents and treatment options to manage biofilm-associated infections in an expanding at-risk population. With better understanding of staphylococcal biofilm formation and growth, novel strategies that target biofilm-associated infections caused by S. aureus have recently been described and seem promising as future anti-biofilm therapies.

Ochrobactrum Anthropi Bacteraemia: Report of Six Cases and Review of the Literature

Background: Ochrobactrum anthropi is an emerging opportunistic pathogen classically considered of low virulence. The purpose of this study is to describe the most recent cases of O. anthropi bacteraemia in our hospital, along with a brief review of the literature. Methods: we have reviewed the cases of O. anthropi registered in the database of our hospital during the last 3 years. Ochrobactrum spp. was identified by the macroscopic appearance and growth characteristics; definitive identification was performed by the commercial system Vitek-2 (Biomerieux, France). Results: We report 6 cases of bacteraemia secondary to O. anthropi infection, 5 of them occurring in immunocompromised patients; the last one was considered to be contaminated due to the lack of risk factors andthe clinical improvement without an effective treatment. Two out of 6 patients had catheter-related infection, the most common infection associated to this organism. Another patient had an O. anthropi-related biliary sepsis. Probably the most relevant cases are patients number 1 and patient number 4, suffering from a pneumonia and a transjugular intrahepatic portosystemic shunt (TIPS)-related infection respectively, two uncommon infections caused by this bacterium. Clinical response was satisfactory in all cases, except in case number 4, probably in relation to the maintenance of the TIPS. Conclusion: severe immunosuppression and association with an indwelling medical device are the main factors associated with most cases of O. anthropi bacteraemia. The most important point in the treatment is the removal of the infected device, in addition to an appropriate antibiotic treatment.

Activities of tobramycin and polymyxin E against Pseudomonas aeruginosa biofilm-coated medical grade endotracheal tubes.

Indwelling medical devices have become a major source of nosocomial infections, especially Pseudomonas aeruginosa infections, which remain the most common cause of ventilator-associated pneumonia (VAP) in neonates and children. Using medical grade polyvinyl chloride endotracheal tubes (ETTs), the activity of tobramycin and polymyxin E was quantified in a simulated prevention and treatment static time-kill model using biofilm-forming P. aeruginosa. The model simulated three clinical conditions: (i) planktonic bacteria grown in the presence of antibiotics (tobramycin and polymyxin E) without ETTs, (ii) planktonic bacteria grown in the presence of P. aeruginosa, antibiotic, and ETTs (simulating prevention), and (iii) a 24-h-formed P. aeruginosa biofilm grown on ETTs prior to antibiotic exposure (simulating treatment). In the model simulating "prevention" (conditions 1 and 2 above), tobramycin alone or in combination with polymyxin E was more bactericidal than polymyxin E alone at 24 h using a concentration of greater than 2 times the MIC. However, after a 24-h-old biofilm was allowed to form on the ETTs, neither monotherapy nor combination therapy over 24 h exhibited bactericidal or bacteriostatic effects. Against the same pathogens, tobramycin and polymyxin E, alone or in combination, exhibited bactericidal activity prior to biofilm attachment to the ETTs; however, no activity was observed once biofilm formed on ETTs. These findings support surveillance culturing to identify pathogens for a rapid and targeted approach to therapy, especially when P. aeruginosa is a potential pathogen.

Anti-biofilm activity of low-molecular weight chitosan hydrogel against Candida species

Candida invasive infections have increased in frequency during the last decades. Such infections are often associated to medical indwelling devices like central venous catheter. The recurrent nature and difficulties in the treatment of these infections are often related to biofilm formation. The objective of this study was to investigate the anti-biofilm activity of low-molecular weight chitosan hydrogel (LMWCH), a natural biopolymer obtained from the N-deacylation of crustacean chitin, upon clinical relevant Candida species. The in vitro ability of LMWCH to impair biofilm formation and to disorganize a preformed biofilm was tested in polystyrene microplates and quantified by the semi quantitative XTT assay and by the crystal violet assay. LMWCH in vivo efficacy as a coating for medical indwelling devices was evaluated for the first time for Candida parapsilosis, using a mouse subcutaneous foreign body model using polyurethane catheter segments. Scanning electron microscopy was used to access biofilm architecture after LMWCH treatment. We found that LMWCH efficiently impaired biofilm formation of all Candida species, also promoting biofilm disaggregation. Most importantly, LMWCH was able to significantly inhibit biofilm formation by C. parapsilosis in an in vivo catheter mouse model. SEM images showed biofilm collapsed cells compatible with membrane damage, suggesting that this could be one of the possible mechanisms underlying biofilm impairment. LMWCH revealed to be a promising compound for treatment of candidiasis or its prevention through medical device coating.

Effects of Bacteriocins on Methicillin-Resistant Staphylococcus aureus Biofilm

Control of biofilms formed by microbial pathogens is an important subject for medical researchers, since the development of biofilms on foreign-body surfaces often causes biofilm-associated infections in patients with indwelling medical devices. The present study examined the effects of different kinds of bacteriocins, which are ribosomally synthesized antimicrobial peptides produced by certain bacteria, on biofilms formed by a clinical isolate of methicillin-resistant Staphylococcus aureus (MRSA). The activities and modes of action of three bacteriocins with different structures (nisin A, lacticin Q, and nukacin ISK-1) were evaluated. Vancomycin, a glycopeptide antibiotic used in the treatment of MRSA infections, showed bactericidal activity against planktonic cells but not against biofilm cells. Among the tested bacteriocins, nisin A showed the highest bactericidal activity against both planktonic cells and biofilm cells. Lacticin Q also showed bactericidal activity against both planktonic cells and biofilm cells, but its activity against biofilm cells was significantly lower than that of nisin A. Nukacin ISK-1 showed bacteriostatic activity against planktonic cells and did not show bactericidal activity against biofilm cells. Mode-of-action studies indicated that pore formation leading to ATP efflux is important for the bactericidal activity against biofilm cells. Our results suggest that bacteriocins that form stable pores on biofilm cells are highly potent for the treatment of MRSA biofilm infections.

Differing lifestyles of Staphylococcus epidermidis as revealed through Bayesian clustering of multilocus sequence types

Staphylococcus epidermidis is part of the normal bacterial flora of human skin and a leading cause of infections associated with indwelling medical devices. Previous phylogenetic analyses of subgenomic data have been unable to distinguish between S. epidermidis strains with nosocomial or commensal lifestyles, despite the identification of specific phenotypes and accessory genes that may contribute to such lifestyles. To attempt to better define the population structure of this species, the international S. epidermidis multilocus sequence typing database was analyzed with the Bayesian clustering programs STRUCTURE and BAPS. A total of six genetic clusters (GCs) were identified. A local population of S. epidermidis from clinical specimens was classified according to these six GCs, and further characterized for antibiotic susceptibilities, biofilm, and various genetic markers. GC5 was abundant and significantly enriched for isolates that were resistant to four classes of antibiotics, high biofilm production, and positive for the virulence markers icaA, IS256, and sesD/bhp, indicating its potential clinical relevance. In contrast, GC2 was rare and contained the only isolates positive for the putative commensal marker, fdh. GC1 and GC6 were abundant but not significantly associated with any of the examined characteristics, except for sesF/aap and GC6. GC3 was rare and identified as a potential genetic sink that received, but did not donate, core genetic material from other GCs. In conclusion, population genetics analyses were essential for identifying clusters of strains that may differ in their adaptation to nosocomial or commensal lifestyles. These results provide a new, population genetics framework for studying S. epidermidis.

Interventions to improve professional adherence to guidelines for prevention of device-related infections

Healthcare-associated infections (HAIs) are a major threat to patient safety, and are associated with mortality rates varying from 5% to 35%. Important risk factors associated with HAIs are the use of invasive medical devices (e.g. central lines, urinary catheters and mechanical ventilators), and poor staff adherence to infection prevention practices during insertion and care for the devices when in place. There are specific risk profiles for each device, but in general, the breakdown of aseptic technique during insertion and care for the device, as well as the duration of device use, are important factors for the development of these serious and costly infections. To assess the effectiveness of different interventions, alone or in combination, which target healthcare professionals or healthcare organisations to improve professional adherence to infection control guidelines on device-related infection rates and measures of adherence. We searched the following electronic databases for primary studies up to June 2012: the Cochrane Effective Paractice and Organisation of Care (EPOC) Group Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, and CINAHL. We searched reference lists and contacted authors of included studies. We also searched the Cochrane Database of Systematic Reviews and Database of Abstracts of Reviews of Effectiveness (DARE) for related reviews. We included randomised controlled trials (RCTs), non-randomised controlled trials (NRCTs), controlled before-after (CBA) studies and interrupted time series (ITS) studies that complied with the Cochrane EPOC Group methodological criteria, and that evaluated interventions to improve professional adherence to guidelines for the prevention of device-related infections. Two review authors independently extracted data and assessed the risk of bias of each included study using the Cochrane EPOC 'Risk of bias' tool. We contacted authors of original papers to obtain missing information. We included 13 studies: one cluster randomised controlled trial (CRCT) and 12 ITS studies, involving 40 hospitals, 51 intensive care units (ICUs), 27 wards, and more than 3504 patients and 1406 healthcare professionals. Six of the included studies targeted adherence to guidelines to prevent central line-associated blood stream infections (CLABSIs); another six studies targeted adherence to guidelines to prevent ventilator-associated pneumonia (VAP), and one study focused on interventions to improve urinary catheter practices. We judged all included studies to be at moderate or high risk of bias.The largest median effect on rates of VAP was found at nine months follow-up with a decrease of 7.36 (-10.82 to 3.14) cases per 1000 ventilator days (five studies and 15 sites). The one included cluster randomised controlled trial (CRCT) observed, improved urinary catheter practices five weeks after the intervention (absolute difference 12.2 percentage points), however, the statistical significance of this is unknown given a unit of analysis error. It is worth noting that N = 6 interventions that did result in significantly decreased infection rates involved more than one active intervention, which in some cases, was repeatedly administered over time, and further, that one intervention involving specialised oral care personnel showed the largest step change (-22.9 cases per 1000 ventilator days (standard error (SE) 4.0), and also the largest slope change (-6.45 cases per 1000 ventilator days (SE 1.42, P = 0.002)) among the included studies. We attempted to combine the results for studies targeting the same indwelling medical device (central line catheters or mechanical ventilators) and reporting the same outcomes (CLABSI and VAP rate) in two separate meta-analyses, but due to very high statistical heterogeneity among included studies (I(2) up to 97%), we did not retain these analyses. Six of the included studies reported post-intervention adherence scores ranging from 14% to 98%. The effect on rates of infection were mixed and the effect sizes were small, with the largest median effect for the change in level (interquartile range (IQR)) for the six CLABSI studies being observed at three months follow-up was a decrease of 0.6 (-2.74 to 0.28) cases per 1000 central line days (six studies and 36 sites). This change was not sustained over longer follow-up times. The low to very low quality of the evidence of studies included in this review provides insufficient evidence to determine with certainty which interventions are most effective in changing professional behaviour and in what contexts. However, interventions that may be worth further study are educational interventions involving more than one active element and that are repeatedly administered over time, and interventions employing specialised personnel, who are focused on an aspect of care that is supported by evidence e.g. dentists/dental auxiliaries performing oral care for VAP prevention.

Surgical Site Infection byCorynebacterium macginleyiin a Patient with Neurofibromatosis Type 1

Corynebacterium (C.) macginleyi is a gram positive, lipophilic rod, usually considered a colonizer of skin and mucosal surfaces. Several reports have associated C. macginleyi with ocular infections, such as conjunctivitis and endophthalmitis. However, even if rare, extraocular infections from C. macginleyi may occur, especially among immunocompromised patients and patients with indwelling medical devices. We report herein the first case of surgical site infection by C. macginleyi after orthopaedic surgery for the correction of kyphoscoliosis in a patient with neurofibromatosis type 1. Our patient developed a nodular granulomatous lesion of about two centimetres along the surgical scar, at the level of C4-C5, with purulent discharge and formation of a fistulous tract. Cervical magnetic resonance imaging showed the presence of a two-centimetre fluid pocket in the subcutaneous tissue. Several swabs were collected from the borders of the lesion as well as from the exudate, with isolation of C. macginleyi. The isolate was susceptible to beta-lactams, cotrimoxazole, linezolid, and glycopeptides but resistant to quinolones, third-generation cephalosporins, and erythromycin. Two 30-day courses of antibiotic therapy with amoxicillin/clavulanate (1 g three times/day) and cotrimoxazole (800/160 mg twice a day) were administered, obtaining a complete healing of the lesion.

Monoclonal Antibody Raised against PNAG Has Variable Effects on Static S. epidermidis Biofilm Accumulation In Vitro

Staphylococcus epidermidis causes infections commonly associated with patients with indwelling medical devices due to its ability to form biofilms, bacterial structures attached to a surface and embedded in a protective matrix. Cells within biofilms are known to be more resistant than free-floating planktonic cells to the host immune response and also to antibiotic therapy often leading to relapsing infections 1. Frequently, surgical removal of an infected device is required to resolve these infections, resulting in significant effects in a patient's quality of life. Hence, preventative approaches are clearly needed to overcome this challenge. Antibodies have been shown to be one promising alternative to target surface-attached molecules and inhibit biofilm formation 2. We have previously shown that human monoclonal antibodies (mAb) specific for poly-β-1,6-N-acetylglucosamine (PNAG) were effective in killing S. epidermidis in opsonophagocytic in vitro assays, and in protecting the murine host against infection by PNAG-producing pathogens 3,4. Since S. epidermidis biofilm accumulation is mainly mediated by PNAG, it was hypothesized that the binding of this molecule by a specific mAb could impact biofilm accumulation, a process that has not previously been investigated. Here we tested the previously characterized mAb F598 3, for inhibition of S. epidermidis biofilm accumulation in vitro. Several concentrations of mAb F598 and the isotype control human mAb F429 (specific for the Pseudomonas aeruginosa alginate capsule) 5, were co-cultured with bacteria in static conditions for 1h at 37oC to allow antibody binding. Thereafter, cultures were incubated for 24h at 37oC with shaking at 250 rpm. Biofilm accumulation was then quantified by the standard crystal violet staining 6. Depending on the S. epidermidis strain used, the presence of mAb F598 had a differential effect on biofilm accumulation. In the case of the ATCC strain RP62A we observed a 42% reduction in biofilm accumulation at the highest mAb concentration tested, while the clinical strains 1457 and M184 grown in the presence of mAb F598 had a dose-dependent increase of the biofilm accumulation. In the case of the PNAG-deficient, ica-mutant strain 1457-M10, as expected, no significant effect was found on the biofilm biomass as no PNAG is produced. Furthermore, control mAb F429 had no significant effect on S. epidermidis biofilm accumulation. The results with the ica-mutant and mAb controls suggest altogether that the inhibitory or enhancing effect of the mAb is PNAG-dependent. As observed in other studies that have used antibodies specific for S. epidermidis surface molecules, the observed enhancement of biofilm formation could be a result of increased PNAG expression caused by the early blockage of the synthesis of this molecule 7. On the other hand, the specificity of mAb F598 for epitopes on PNAG that do not require the N-acetyl groups on the glucosamine monomers may have contributed to the differential effects in biofilm accumulation. These would thus depend on the level of PNAG acetylation of individual strains, ultimately, controlled by the IcaB extracellular deacetylase. Therefore, mAbs directed to other epitopes might be better suited for inhibition of in vitro biofilm accumulation. Additionally, the results presented here suggest that a difference between the effect of mAb F598 against PNAG-producing bacteria in animal models 3,4 and it efficiency at inhibiting in vitro static biofilm accumulation among different S. epidermidis strains. Notably, many biofilms are formed under flow conditions and it is not clear to what extent shear stress from flow over in vivo biofilms contributes to biofilm formation, and whether under those conditions the effect of mAb F598 might be different. While the stimulation of biofilm formation by S. epidermidis grown in vitro may raise questions regarding the usage of mAb F598 in vivo, the results do not necessarily exclude that mAb F598 could be effective in vivo against biofilm infections. The majority of studies that reported strong biofilm inhibition by monoclonal or polyclonal antibodies used only a few strains in the assays 2,8, which could result in misleading interpretations. The findings presented here further stress the necessity to use more than a few strains when testing the efficacy of new biofilm-inhibition strategies in order to ensure that the desired effect is observed in a representative number of clones of the species under study.