Isolates of Klebsiella pneumoniae are responsible for opportunistic infections in humans, particularly of the urinary respiratory tracts. These bacteria express type 3 fimbriae that have been implicated in binding to eukaryotic cells and matrix proteins. Twenty four (24) K. pneumoniae strains isolated from medical devices were studied. Their capacity to form biofilm was assessed using two types of materials, polyvinylchloride (PVC) and glass of microfermenter in static or kinetic conditions. Strains with adherence to PVC also cling strongly to glass slides. We determined the in vitro effects of three antimicrobial agents against planktonic and biofilm forms of K. pneumoniae and we demonstrated that isolates of the biofilm form were at least 10-25 times more resistant than the planktonic form. Most strains of K. pneumoniae harbored the mrkD gene and exhibited a strong ability to adhere to inert surfaces.
Acinetobacter baumannii is an opportunistic pathogen responsible for nosocomial infections due to biofilm formation on the surface of implantable medical devices. Thirty (30) strains of A. baumannii were isolated from medical devices and tested for their ability to form a biofilm. The factors that may influence this process, such as the hydrophobicity of the bacterial wall, temperature, duration of implantation and the nature of the medical device, were also investigated. Strains were able to form a biofilm; however this process was more substantial at 30°C than at 37°C and was maximal after 96 h of incubation. Strains seem to adhere better to silicone and latex than to polyvinylchloride (PVC) and no apparent relationship was found between hydrophobicity and biofilm formation.
Staphylococcus spp. is a major cause of infections associated with urinary catheterization and other medical devices. Biofilm formation is an important step in the pathogenesis of these Staphylococci and depends on the expression of the icaADBC operon involved in the synthesis of a polysaccharide intercellular adhesion. In this study, forty-four (44) Staphylococcus spp. obtained from urinary catheters at the University Hospital of Tlemcen (North-West Algeria) were analyzed to investigate the presence or absence of the intercellular adhesion icaA and icaD genes, using the polymerase chain reaction (PCR). Phenotypic biofilm formation was examined by tissue culture plate (TCP) and Congo red agar (CRA) methods. Seventeen (17) of 44 isolates were shown to carry ica-specific DNA, 18 produced slime on CRA plates but only eight produced biofilm spontaneously on the polystyrene surfaces, under normal growth conditions. Upon induction by sugar, biofilm formation could be stimulated in seven (7) of nine (9)ica positive. Biofilm-negative isolates indicated that the icaADBC expression was down-regulated in these strains. Staphylococcus strains isolated from urinary catheters showed high levels of resistance to penicillin (98%) and gentamicine (75%). The data obtained shows the important role of ica-genes, the phenotypic variability of biofilm formation and the multi-resistance to antibiotics as virulence factors of staphylococcus spp. from urinary catheters.It confirms the complexity and diversity of regulation mechanisms implicated in biofilm formation.
Background: Klebsiella pneumoniae is a major cause of community-acquired and nosocomial infections. This germ is responsible for acute and chronic infections, most of which are due to its ability to adhere to medical implants and form a biofilm. The objective of this work is to study the interaction between clinical isolates of K. pneumoniae and abiotic surfaces (medical devices) and some factors influencing biofilm formation. Methods: Over a period of 2 years, 115 strains of K. pneumoniae were isolated from medical devices CHU Tlemcen, most of which had a high level of resistance to cephalosporins 1 st , 2 nd , and 3 rd generation. Their capacity to form biofilm was assessed using 3 techniques: TCP, TP, and RCA. We determined in vitro the effects of three antimicrobial agents against planktonic and biofilm forms of K. pneumoniae. The presence of MrkD genes was detected by polymerase chain reaction (PCR). Results: According to the studied (TCP, TP, RCA) strains of K .pneumoniae isolated from urinary catheters have proved very good, forming the biofilm to those isolated from other medical devices. 24 of 115 isolated strains showed a clear difference in antibiotic susceptibility between planktonic populations and biofilm populations. They were 10-20 times higher. All strains presented a highly hydrophilic character and adhesion 2-10 times greater in PVC with respect to glass support. The MrkD gene (detected by PCR) responsible for biofilm formation was found in 22 strains of K. pneumoniae, which may explain their adhesion and therefor their pathogenicity.
Conclusion:Our results show the great ability of K.pneumoniae strains to form a biofilm on medical devices, and the isolates were at least 10 times more resistant than their planktonic counterparts. In addition, we showed that the presence of type 3-encoding gene mrkD was associated with high adhesion indexes.
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