A study on device-related infections with special reference to biofilm production and antibiotic resistance

Relationship between Antibiotic Resistance, Biofilm Formation, and Biofilm-Specific Resistance in Acinetobacter baumannii

In this study, we aimed to examine the relationships between antibiotic resistance, biofilm formation, and biofilm-specific resistance in clinical isolates of Acinetobacter baumannii. The tested 272 isolates were collected from several hospitals in China during 2010–2013. Biofilm-forming capacities were evaluated using the crystal violet staining method. Antibiotic resistance/susceptibility profiles to 21 antibiotics were assessed using VITEK 2 system, broth microdilution method or the Kirby-Bauer disc diffusion method. The minimum inhibitory concentration (MIC) and minimum biofilm eradication concentration (MBEC) to cefotaxime, imipenem, and ciprofloxacin were evaluated using micro dilution assays. Genetic relatedness of the isolates was also analyzed by pulsed-field gel electrophoresis (PFGE) and plasmid profile. Among all the 272 isolates, 31 were multidrug-resistant (MDR), and 166 were extensively drug-resistant (XDR). PFGE typing revealed 167 pattern types and 103 clusters with a similarity of 80%. MDR and XDR isolates built up the main prevalent genotypes. Most of the non-MDR isolates were distributed in a scattered pattern. Additionally, 249 isolates exhibited biofilm formation, among which 63 were stronger biofilm formers than type strain ATCC19606. Population that exhibited more robust biofilm formation likely contained larger proportion of non-MDR isolates. Isolates with higher level of resistance tended to form weaker biofilms. The MBECs for cefotaxime, imipenem, and ciprofloxacin showed a positive correlation with corresponding MICs, while the enhancement in resistance occurred independent of the quantity of biofilm biomass produced. Results from this study imply that biofilm acts as a mechanism for bacteria to get a better survival, especially in isolates with resistance level not high enough. Moreover, even though biofilms formed by isolates with high level of resistance are always weak, they could still provide similar level of protection for the isolates. Further explorations genetically would improve our understanding of these processes and provide novel insights in the therapeutics and prevention against A. baumannii biofilm-related infections.

Evaluation of Different Phenotypic Techniques for the Detection of Slime Produced by Bacteria Isolated from Clinical Specimens

Introduction 

Microorganisms use various strategies for their survival in both the environment and in humans. Slime production by bacteria is one such mechanism by which microbes colonize on the indwelling prosthetic devices and form biofilms. Infections caused by such microorganisms are difficult to treat as the biofilm acts as a shield and protects microbes against antimicrobial agents. There are several methods for the detection of slime produced by bacteria, and they include both phenotypic and molecular methods. The present study evaluated the Congo red agar/broth method, Christensen’s method, dye elution technique, and the latex agglutination method for the demonstration of slime production by different bacterial clinical isolates.

Materials & Methods

We collected 151 bacterial clinical isolates (both gram-positive and gram-negative bacteria) from various specimens and tested them for the production of slime both by qualitative and quantitative tests. Congo red agar/broth method, Christensen's method, dye elution technique, and latex agglutination methods were used for detecting the slime or slime-like substance.

Results 

We found that 103 (68.2%) strains were positive for slime production by Congo red agar/broth method. It was found that 18 (94.7%) strains of Klebsiellapneumoniae, 21 (84.0%) strains of S aureus and 25 (65.7%) strains of coagulase-negative Staphylococci were positive for slime or slime-like substances by Congo red agar/broth method. A total of 41.0% of the strains positive by Christensen's method and 15.2% of the strains by dye elution technique were found to be more adherent organisms and that have the potential to form biofilms. Only the gram-positive organisms showed nonspecific agglutination with latex suspension.

Conclusion 

Among the various phenotypic methods compared in this study the Congo red agar/broth method is a simple, economical, sensitive, and specific method that can be used by clinical microbiology laboratories for screening the strains for the presence of slime or slime-like substances.

Healthcare-associated infections, medical devices and biofilms: risk, tolerance and control

Biofilms are of great importance in infection control and healthcare-associated infections owing to their inherent tolerance and 'resistance' to antimicrobial therapies. Biofilms have been shown to develop on medical device surfaces, and dispersal of single and clustered cells implies a significant risk of microbial dissemination within the host and increased risk of infection. Although routine microbiological testing assists with the diagnosis of a clinical infection, there is no 'gold standard' available to reveal the presence of microbial biofilm from samples collected within clinical settings. Furthermore, such limiting factors as viable but non-culturable micro-organisms and small-colony variants often prevent successful detection. In order to increase the chances of detection and provide a more accurate diagnosis, a combination of microbiological culture techniques and molecular methods should be employed. Measures such as antimicrobial coating and surface alterations of medical devices provide promising opportunities in the prevention of biofilm formation on medical devices.

Bacteremia and pneumonia in a tertiary PICU: an 11-year study

OBJECTIVES

To describe trends in aetiology and resistance patterns and patient outcomes of bacteraemia and pneumonia in a PICU over an 11-year period. We also describe interventions aimed at reducing multi-resistant infections and other serious bacterial infections in the PICU.

DESIGN AND SETTING

This cohort study involved data collected between January 2002 and December 2012 in the PICU of the Royal Children's Hospital in Melbourne, Australia. We documented all bacterial and fungal pathogens isolated from culture of blood or bronchial alveolar lavage fluid. Trends in aetiology and antibiotic resistance patterns were evaluated, as well as the case fatality rates of population-subgroups.

PATIENTS, MEASUREMENT AND MAIN RESULTS

Overall, 881 patients (8.9%) had 1,480 serious bacterial or fungal infections and 1.2% of the PICU population suffered a multidrug-resistant infection. Twenty-six percent of 597 total deaths in the PICU during that time period were associated with a serious bacterial infection of the blood or lungs. Children in PICU with a serious infection in blood or lungs had a case fatality rate of 17.5% (95% CI, 15.0-20.2), compared with children overall in the PICU with a case fatality rate of 6.0% (95% CI, 5.5-6.5). The case fatality rate among children with multidrug-resistant sepsis was 25.6% (95% CI, 18.1-34.4) and among children with a persistent or recurrent infection in blood or lungs was 43.1% (95% CI, 30.8-56.0). Cases of multidrug-resistant bacteremia and bronchial alveolar lavage-proven pneumonia increased from 2002 to 2010 and significantly decreased from 2011, coinciding with improvements in antibiotic stewardship and infection control.

CONCLUSIONS

Multiresistant bacterial sepsis and persistent or recurrent sepsis are major threats in pediatric intensive care and are associated with disproportionally high death rates. Our study describes a model for monitoring these serious infections and the effects of infection control interventions in the PICU.

Microbial composition and antibiotic resistance of biofilms recovered from endotracheal tubes of mechanically ventilated patients

In critically ill patients, breathing is impaired and mechanical ventilation, using an endotracheal tube (ET) connected to a ventilator, is necessary. Although mechanical ventilation is a life-saving procedure, it is not without risk. Because of several reasons, a biofilm often forms at the distal end of the ET and this biofilm is a persistent source of bacteria which can infect the lungs, causing ventilator-associated pneumonia (VAP). There is a link between the microbial flora of ET biofilms and the microorganisms involved in the onset of VAP. Culture dependent and independent techniques were already used to identify the microbial flora of ET biofilms and also, the antibiotic resistance of microorganisms obtained from ET biofilms was determined. The ESKAPE pathogens play a dominant role in the onset of VAP and these organisms were frequently identified in ET biofilms. Also, antibiotic resistant microorganisms were frequently present in ET biofilms. Members of the normal oral flora were also identified in ET biofilms but it is thought that these organisms initiate ET biofilm formation and are not directly involved in the development of VAP.

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.

Antiadhesive polymer brush coating functionalized with antimicrobial and RGD peptides to reduce biofilm formation and enhance tissue integration

This paper describes the synthesis and characterization of polymer-peptide conjugates to be used as infection-resistant coating for biomaterial implants and devices. Antiadhesive polymer brushes composed of block copolymer Pluronic F-127 (PF127) were functionalized with antimicrobial peptides (AMP), able to kill bacteria on contact, and arginine-glycine-aspartate (RGD) peptides to promote the adhesion and spreading of host tissue cells. The antiadhesive and antibacterial properties of the coating were investigated with three bacterial strains: Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa. The ability of the coating to support mammalian cell growth was determined using human fibroblast cells. Coatings composed of the appropriate ratio of the functional components: PF127, PF127 modified with AMP, and PF127 modified with RGD showed good antiadhesive and bactericidal properties without hampering tissue compatibility.

Propensity for biofilm formation by clinical isolates from urinary tract infections: developing a multifactorial predictive model to improve antibiotherapy

A group of biofilm-producing bacteria isolated from patients with urinary tract infections was evaluated, identifying the main factors contributing to biofilm formation. Among the 156 isolates, 58 (37.2%) were biofilm producers. The bacterial species (P<0.001), together with patient's gender (P = 0.022), were the factors with the highest influence for biofilm production. There was also a strong correlation of catheterization with biofilm formation, despite being less significant (P = 0.070) than species or gender. In fact, some of the bacteria isolated were biofilm producers in all cases. With regard to resistance profile among bacterial isolates, β-lactam antibiotics presented the highest number of cases/percentages--ampicillin (32/55.2%), cephalothin (30/51.7%), amoxicillin/clavulanic acid (22/37.9%)--although the carbapenem group still represented a good therapeutic option (2/3.4%). Quinolones (nucleic acid synthesis inhibitors) also showed high resistance percentages. Furthermore, biofilm production clearly increases bacterial resistance. Almost half of the biofilm-producing bacteria showed resistance against at least three different groups of antibiotics. Bacterial resistance is often associated with catheterization. Accordingly, intrinsic (age and gender) and extrinsic (hospital unit, bacterial isolate and catheterization) factors were used to build a predictive model, by evaluating the contribution of each factor to biofilm production. In this way, it is possible to anticipate biofilm occurrence immediately after bacterial identification, allowing selection of a more effective antibiotic (among the susceptibility options suggested by the antibiogram) against biofilm-producing bacteria. This approach reduces the putative bacterial resistance during treatment, and the consequent need to adjust antibiotherapy.