Identification of bap and icaA genes involved in biofilm formation in coagulase negative staphylococci isolated from feline conjunctiva

Bap and icaA genes are commonly known to be involved in the biofilm formation. The prevalence of bap and icaA genes and biofilm formation was determined in conjunctival isolates of coagulase negative staphylococci (CNS) collected from cats. The study was conducted on 90 archival CNS isolates collected from feline conjunctiva obtained from clinically healthy cats and cats with ocular problems. Biofilm formation was examined using the microtiter plate (MTP) method. The prevalence of icaA and bap genes was determined using polymerase chain reaction (PCR). Genetic profiles of the bap-positive isolates were examined using the modified random amplified polymorphic DNA (RAPD) method. Of the 90 CNS isolates investigated, 58.9 % (53/90) were confirmed to form biofilms on a polystyrene plate after 24 h, and the intensity of the biofilm production varied strongly between positive strains. Among the biofilm-producing isolates, 24.5 % (13/53) carried the icaA gene and 3.8 % (2/53) carried the bap gene. Among the isolates that did not produce biofilms, the icaA gene and bap gene were detected in 8.1 % (3/37) and 2.7 % (1/37) of isolates, respectively. This is the first report demonstrating that CNS isolated from feline conjunctiva can potentially be a bap gene reservoir. Preliminary comparison of the genetic profiles of three bap-positive isolates collected from cats showed that each of the isolates has a different genetic background with a high similarity with the human strain of S. epidermidis.     

Wound care antiseptics - performance differences against Staphylococcus aureus in biofilm

Background

Staphylococcus aureus is commonly isolated from infected wounds both in animals and humans. It is known to be an excellent biofilm former and biofilms are present in as many as 60% of chronic wounds. Despite that the presence of biofilms in infections are common, antiseptics are usually qualified for in vivo testing according to their effect on planktonic cells. As it is well known that bacteria in biofilms are more tolerant to antiseptics than planktonic bacteria, biofilm infections can be difficult to treat. The aim of the study was to compare three different categories of antiseptics, biguanide (chlorhexidine), quaternary ammonium compound (QAC; Pyrisept) and iodine/iodophores (2% iodine liniment), with regards to efficacy in killing S. aureus in biofilm. If there was observed a difference in efficacy between these antiseptics, a second aim was to find the most effective of the three antiseptics.

Results

Large differences in the bactericidal effect of the different antiseptics against S. aureus in biofilm were observed in the present study. Iodine treatment was found to be the most effective followed by Pyrisept and chlorhexidine.

Conclusions

The bactericidal effect of the different antiseptics used in the present study was found to vary significantly against S. aureus in biofilm. The present study gives valuable knowledge with regards to selecting the antiseptics that are most likely to be successful in treating biofilm infected wounds. This study also contributes to focus attention on the importance of qualifying antiseptics based on results using biofilm bacteria rather than planktonic bacteria.     

The role of galU and galE of Haemophilus parasuis SC096 in serum resistance and biofilm formation

In our previous study, an ompP2 mutant of a Haemophilus parasuis SC096 strain showed sensitivity to serum bactericidal activity. In this study, we inactivated two gal genes, galU and galE, and these mutants were found to be serum sensitive to porcine sera. Furthermore, the galE mutant exhibited greater sensitivity than the galU mutant in serum sensitivity assays. Biofilm formation ability was also investigated. The galU mutant is unable to form biofilms, while more biofilm mass was produced by the galE mutant compared with SC096. Lack of expression of GalU protein by the galU mutant increased its tendency to autoagglutinate. The results indicated that the galU plays a role in autoagglutination and biofilm formation, while galE may affect the biofilm production indirectly. Both genes are significant for serum resistance in the H. parasuis SC096 strain.     

Effect of laser shock peening on fatigue life and surface characteristics of stainless steel cortical bone screws

OBJECTIVE: To investigate the effect of laser shock peening on the fatigue life and surface characteristics of 3.5-mm-diameter cortical bone screws. SAMPLE POPULATION: 32 stainless steel, 3.5-mm-diameter cortical bone screws. PROCEDURE: Screws were randomly assigned to an untreated control group or 2 power-density treatment groups, 6 gigawatts (GW)/cm2 and 8.5 GW/cm2, for laser shock peening. Number of cycles to failure and findings on scanning electron microscopy-assisted morphometric evaluation, including the mode of failure, surface debris, surface damage, and thread deformation, were compared between control and treated screws. RESULTS: The 6 GW/cm2 treated screws had a significant (11%) improvement in fatigue life, compared with untreated control screws. The 8.5 GW/cm2 treated screws had a significant (20%) decrease in fatigue life, compared with control screws. A mild but significant increase in thread deformation was evident in all treated screws, compared with control screws. The 8.5 GW/cm2 treated screws had significantly more surface irregularities (elevations and pits), compared with control or 6 GW/cm2 treated screws. CONCLUSION AND CLINICAL RELEVANCE: A modest positive increase in fatigue strength was produced by this design of laser shock peening on the midshaft of cortical bone screws. High laser shock peening power densities were detrimental, decreasing screw fatigue strength probably resulting from structural damage. Greater fatigue life of cortical bone screws can be generated with laser shock peening and could reduce screw breakage as a cause of implant failure; however, future studies will be necessary to address biocompatibility, alternative cleaning techniques, alterations in screw strength and pullout characteristics, and effects on susceptibility to corrosion.     

Characterization of Mannheimia haemolytica biofilm formation in vitro

Mannheimia haemolytica is the primary bacterial agent in the bovine respiratory disease complex. It is thought that M. haemolytica colonizes the tonsillar crypts of cattle as a commensal and subsequently descends into the lungs to cause disease. Many bacterial species persist in the host as biofilms. There is limited information about the ability of M. haemolytica to form biofilms. The aim of this study was to develop an in vitro model for M. haemolytica biofilm formation. We found that M. haemolytica required at least 36 h to form robust biofilms on plastic in vitro when incubated in RPMI-1640 tissue culture medium at 37 °C, with maximal biofilm formation being evident at 48 h. Biofilm formation was inhibited by adding the monosaccharides d(+) galactose and d(+) mannose to the growth medium. Addition of antibodies to the M. haemolytica surface protein OmpA also reduced biofilm formation. Upon evaluating the macromolecules within the biofilm extracellular polymeric substance we found it contained 9.7 μg/cm² of protein, 0.81 μg/cm² of total carbohydrate, and 0.47 μg/cm² of extracellular DNA. Furthermore, proteinase K treatment significantly decreased biofilms (P < 0.05) while α-amylase and micrococcal nuclease decreased biofilms to a lesser extent. M. haemolytica biofilm cells were more resistant than planktonic cells to the antibiotics florfenicol, gentamicin, and tulathromycin. These results provide evidence that M. haemolytica can form biofilms, which could contribute to its ability to persist as a commensal in the bovine upper respiratory tract.     

An in vitro biomechanical comparison between prototype tapered shaft cortical bone screws and AO cortical bone screws for an equine metacarpal dynamic compression plate fixation of osteotomized equine third metacarpal bones

OBJECTIVES: To compare biomechanical properties of a prototype 5.5 mm tapered shaft cortical screw (TSS) and 5.5 mm AO cortical screw for an equine third metacarpal dynamic compression plate (EM-DCP) fixation to repair osteotomized equine third metacarpal (MC3) bones. STUDY DESIGN: Paired in vitro biomechanical testing of cadaveric equine MC3 with a mid-diaphyseal osteotomy, stabilized by 1 of 2 methods for fracture fixation. ANIMAL POPULATION: Adult equine cadaveric MC3 bones (n=12 pairs). METHODS: Twelve pairs of equine MC3 were divided into 3 groups (4 pairs each) for (1) 4-point bending single cycle to failure testing, (2) 4-point bending cyclic fatigue testing, and (3) torsional single cycle to failure testing. An EM-DCP (10-hole, 4.5 mm) was applied to the dorsal surface of each, mid-diaphyseal osteotomized, MC3 pair. For each MC3 bone pair, 1 was randomly chosen to have the EM-DCP secured with four 5.5 mm TSS (2 screws proximal and distal to the osteotomy; TSS construct), two 5.5 mm AO cortical screws (most proximal and distal holes in the plate) and four 4.5 mm AO cortical screws in the remaining holes. The control construct (AO construct) had four 5.5 mm AO cortical screws to secure the EM-DCP in the 2 holes proximal and distal to the osteotomy in the contralateral bone from each pair. The remaining holes of the EM-DCP were filled with two 5.5 mm AO cortical screws (most proximal and distal holes in the plate) and four 4.5 mm AO cortical screws. All plates and screws were applied using standard AO/ASIF techniques. Mean test variable values for each method were compared using a paired t-test within each group. Significance was set at P<.05. RESULTS: Mean 4-point bending yield load, yield bending moment, bending composite rigidity, failure load and failure bending moment of the TSS construct were significantly greater (P<.00004 for yield and P<.00001 for failure loads) than those of the AO construct. Mean cycles to failure in 4-point bending of the TSS construct was significantly greater (P<.0002) than that of the AO construct. The mean yield load and composite rigidity in torsion of the TSS construct were significantly greater (P<.0039 and P<.00003, respectively) than that of the AO construct. CONCLUSION: The TSS construct provides increased stability in both static overload testing and cyclic fatigue testing. CLINICAL RELEVANCE: The results of this in vitro study support the conclusion that the EM-DCP fixation using the prototype 5.5 mm TSS is biomechanically superior to the EM-DCP fixation using 5.5 mm AO cortical screws for the stabilization of osteotomized equine MC3.     

Biofilm production by pathogens associated with canine otitis externa,and the antibiofilm activity of ionophores and antimicrobial adjuvants

Otitis externa (OE) is a frequently reported disorder in dogs associated with secondary infections by Staphylococcus, Pseudomonas and yeast pathogens. The presence of biofilms may play an important role in the resistance of otic pathogens to antimicrobial agents. Biofilm production of twenty Staphylococcus pseudintermedius and twenty Pseudomonas aeruginosa canine otic isolates was determined quantitatively using a microtiter plate assay, and each isolate was classified as a strong, moderate, weak or nonbiofilm producer. Minimum biofilm eradication concentration (MBEC) of two ionophores (narasin and monensin) and three adjuvants (N‐acetylcysteine (NAC), Tris‐EDTA and disodium EDTA) were investigated spectrophotometrically (OD_570nm) and quantitatively (CFU/ml) against selected Staphylococcus and Pseudomonas biofilm cultures. Concurrently, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of planktonic cultures were assessed. 16/20 of the S. pseudintermedius clinical isolates were weak biofilm producers. 19/20 P. aeruginosa clinical isolates produced biofilms and were distributed almost equally as weak, moderate and strong biofilm producers. While significant antibiofilm activity was observed, no MBEC was achieved with narasin or monensin. The MBEC for NAC ranged from 5,000–10,000 µg/ml and from 20,000–80,000 µg/ml against S. pseudintermedius and P. aeruginosa, respectively. Tris‐EDTA eradicated P. aeruginosa biofilms at concentrations ranging from 6,000/1,900 to 12,000/3,800 µg/ml. The MBEC was up to 16‐fold and eightfold higher than the MIC/MBC of NAC and Tris‐EDTA, respectively. Disodium EDTA reduced biofilm growth of both strains at concentrations of 470 µg/ml and higher. It can be concluded that biofilm production is common in pathogens associated with canine OE. NAC and Tris‐EDTA are effective antibiofilm agents in vitro that could be considered for the treatment of biofilm‐associated OE in dogs.     

The Effects of Screw Removal on Bone Strain in an Idealized Plated Bone Model

An idealized plated bone model was used to test the hypothesis that selected screw removal could alter the bone strain field and be a viable treatment for stress protection osteoporosis. Eighteen bone screw modifications were evaluated for their effects on bone strain. The three variables studied were number, position, and length of screws. Removal of two or four bone screws from an eight hole plate significantly increased the strain per load on the bone model over the values with eight screws in the plate (p less than 0.05). The four screw configurations increased bone strain more than the six screw configurations. It also was shown that the position of screws in the plate could significantly alter the bone strain per load results. Removal of six bone screws from an eight hole plate also increased the bone strain per load, but to excess in some tests. In those configurations, the results were not statistically different from the unplated configuration. Replacement of the full length screws with eight half length screws that engaged only the near cortex significantly reduced bone strain per load as compared with eight bicortical bone screws.     

Biofilm bacteria: formation and comparative susceptibility to antibiotics

The Calgary Biofilm Device (CBD) was used to form bacterial biofilms of selected veterinary gram-negative and gram-positive pathogenic bacteria from cattle, sheep, pigs, chicken, and turkeys. The minimum inhibitory concentration (MIC) and minimum biofilm eradication concentration (MBEC) of ampicillin, ceftiofur, cloxacillin, oxytetracycline, penicillin G, streptomycin, tetracycline, enrofloxacin, erythromycin, gentamicin, tilmicosin, and trimethoprim-sulfadoxine for gram-positive and -negative bacteria were determined. Bacterial biofilms were readily formed on the CBD under selected conditions. The biofilms consisted of microcolonies encased in extracellular polysaccharide material. Biofilms composed of Arcanobacterium (Actinomyces) pyogenes, Staphylococcus aureus, Staphylococcus hyicus, Streptococcus agalactiae, Corynebacterium renale, or Corynebacterium pseudotuberculosis were not killed by the antibiotics tested but as planktonic bacteria they were sensitive at low concentrations. Biofilm and planktonic Streptococcus dysgalactiae and Streptococcus suis were sensitive to penicillin, ceftiofur, cloxacillin, ampicillin, and oxytetracycline. Planktonic Escherichia coli were sensitive to enrofloxacin, gentamicin, oxytetracycline and trimethoprim/ sulfadoxine. Enrofloxacin and gentamicin were the most effective antibiotics against E. coli growing as a biofilm. Salmonella spp. and Pseudomonas aeruginosa isolates growing as planktonic populations were sensitive to enrofloxacin, gentamicin, ampicillin, oxytetracycline, and trimethoprim/sulfadoxine, but as a biofilm, these bacteria were only sensitive to enrofloxacin. Planktonic and biofilm Pasteurella multocida and Mannheimia haemolytica had similar antibiotic sensitivity profiles and were sensitive to most of the antibiotics tested. The CBD provides a valuable new technology that can be used to select antibiotics that are able to kill bacteria growing as biofilms.     

Surgical Management of Proximal Splint Bone Fractures in the Horse

Fractures of Metacarpal and Metatarsal II and IV (the splint bones) were treated in 283 horses over an 11 year period. In 21 cases the proximal portion of the fractured bone was stabilized with metallic implants. One or more cortical bone screws were used in 11 horses, and bone plates were applied in 11 horses. One horse received both treatments. Complications of screw fixation included bone failure, implant failure, radiographic lucency around the screws, and proliferative new bone at the ostectomy site. Only two of the horses treated with screw fixation returned to their intended use. Complications of plate fixation included partial fixation failure (backing out of screws), wound drainage, and proliferative bony response around the plate. Six of the 11 horses treated by plate fixation returned to their intended use. The authors recommend consideration of plate fixation techniques for repair of fractures in the proximal third of the splint bone.     

Control of bacterial and fungal biofilms by natural products of Ziziphus joazeiro Mart. (Rhamnaceae)

The aim of this study is to verify the action of the aqueous leaf extract Ziziphus joazeiro in the eradication of bacterial and fungal biofilms, and to compare these effects with the stem bark extracts, as well as with conventional standard drugs. The presence of secondary metabolites was observed through phytochemical prospection assays. The effect of the aqueous extract on microbial biofilm formation was observed by OD600 nm absorbance and the crystal violet assay. For bacterial and fungal biofilms, chlorhexidine gluconate and fluconazole, respectively, were used as positive controls. Phytochemical characterization showed the presence of secondary metabolite classes common to both extracts such as flavonoids, steroids and saponins. In particular, in the aqueous leaf extract phenols, condensed tannins and alkaloids were observed. Eradication results using the aqueous leaf extract showed an inhibition of the microbial biofilm mass, moreover the biofilms were more sensitive to the bark extract, which presented a greater inhibition number and an action similar to standard drugs. It is important to highlight the leaf extract showed significant eradication at the lowest concentrations for mature yeast biofilms, thus demonstrating its potential to modify microbial resistance susceptibility. Bacterial and fungal biofilm eradication results using the Ziziphus joazeiro aqueous extracts presented a biofilm inhibition effect for both, moreover the results support the ethnopharmacological knowledge surrounding the use of Ziziphus joazeiro stems in the community. In comparison, the bark extract presented a more effective treatment than the leaf extract against biofilms, presenting inhibition levels similar to the used standard drugs.     

Purification of equine neutrophil lysozyme and its antibacterial activity against Gram-positive and Gram-negative bacteria

Lysozyme from equine neutrophil granulocytes was isolated in a pure form by fast performance liquid chromatography, i.e. ion-exchange chromatography and reversed-phase chromatography. The lysozyme lysed Micrococcus luteus, Bacillus subtilis and Staphylococcus lentus and was also bactericidal against the Gram-negative bacteria Escherichia coli, Klebsiella pneumoniae, Bordetella bronchiseptica, and Serratia marcescens. Staphylococcus aureus and Staphylococcus epidermidis were not lysed. The lysozyme was only very slightly bactericidal for S. epidermidis and S. aureus. Equine neutrophil lysozyme was found to be bactericidal for Gram-positive as well as for Gram-negative bacteria without further treatment. Equine and chicken egg white lysozymes were found to be immunologically related when examined using specific antisera against each of them. Both lysozymes also had very similar specific enzymatic activities against M. luteus membranes.     

Intervertebral biomechanics of locking compression plate monocortical fixation of the canine cervical spine

Objective: To evaluate the use of a locking compression plate (LCP) with monocortical screw purchase for stabilization of the canine cervical spine. Study Design: Experimental study. Animals: Cadaveric canine cervical spine specimens (n=7). Methods: Flexion and extension bending moments were applied to canine cadaveric specimens (C3–C6) in 4‐point bending, before and after creation of a ventral slot at C4–C5, and after fixation with a 5 hole, 3.5 mm LCP with monocortical screw placement. Screw placement and penetration into the vertebral canal were determined by radiography. Range of motion, stiffness, and energy for passive physiologic loads were determined for the C3–C4, C4–C5, and C5–C6 vertebral motion units (VMU). Monotonic failure properties were determined for cervical extension. Effects of treatments on biomechanical variables were assessed using repeated measures analysis of variance and least square means (P≤.05). Results: The ventral slot procedure increased range of motion at the treated VMU. Plate fixation decreased range of motion, increased stiffness, and decreased energy at the treated VMU. No changes were observed at adjacent VMUs. None of the screws penetrated the vertebral canal. Mean (± SD) yield bending moment of plate stabilized, slotted spines was 15.6 ± 4.6 N m. Conclusion: LCP fixation with monocortical screws stabilized the canine cervical spine.     

Risk factors for screw migration after triple pelvic osteotomy

The objective of this retrospective study was to identify risk factors for screw migration after triple pelvic osteotomy (TPO) in clinical patients. The medical records, radiographs made immediately after surgery, and follow-up radiographs documenting a healed osteotomy were reviewed for 52 dogs treated with unilateral TPO and 38 dogs treated with bilateral TPO. Signalment, surgeon expertise, length of surgery, sequence of surgery in dogs treated bilaterally, use of ischial or ilial wires or both, screw depth in the sacrum, and screw migration were documented for each of the 128 pelvic osteotomies. Screws placed in the first and second plate hole, securing the cranial portion of the plate, loosened most frequently. Factors associated with decreased screw migration included use of an ischial hemicerclage wire and increased depth of sacral purchase with the first and second cranial screws.     

Structural Properties of Interlocking Nails, Canine Femora, and Femur-Interlocking Nail Constructs

Using standard material testing techniques (bending stiffness, torsional stiffness, and maximum torque to failure or yield torque), the structural properties of interlocking nails (IN), canine femora, and IN/femur constructs were determined. Specimens that were tested included: 6 and 8 mm diameter IN with 5 to 10 screw holes (n = 18), and intact canine femora (n = 10), which also, with an IN inserted, formed the intact construct (IC) group, (n = 10). Specimens in the IC group were first tested with an 8 mm diameter IN with zero screws, followed by one and two screws (4.5 mm diameter) in the proximal and distal femur. A fracture model construct (FMC), (n = 14), consisting of a transverse femoral osteotomy with a 3 mm gap, was used with either 6 mm or 8 mm IN. In the 6 mm FMC, one and two 3.5 mm screws were used sequentially in the proximal and distal femoral segment. In the 8 mm FMC, one and two 3.5 mm screws and one and two 4.5 diameter screws were used similarly. When bending forces were applied parallel to IN screw holes, mean IN stiffness was 20% less than with forces perpendicular to the holes (n = 18), (P <.05). Eight-millimeter IN were 220% stiffer in torsion and 270% stiffer in bending than 6 mm IN (P <.05). Six-millimeter IN had approximately 32% of the bending stiffness and torsional stiffness of intact femurs (P <.05). Eight-millimeter IN had 93% and 79% of the bending stiffness and torsional stiffness, respectively, of intact femurs. Intact femur constructs (8 mm IN with four, 4.5 mm screws) had 147% of the bending stiffness (P <.05), and similar torsional stiffness and maximum torque, as intact femora (P >.05). The mean values of 6 mm FMC with four screws (3.5 mm) were 21% and 33% in torsional stiffness and bending stiffness, respectively, of intact femora values. When tested in torsion, 8 mm FMC failed by bone fracture; 6 mm FMC, in contrast, underwent plastic deformation. In comparing FMC stabilized with an 8 mm IN with two screws (4.5 mm diameter) in each bone segment, to intact femurs, the maximum torque was similar, FMC torsional stiffness was 40% (P <.05), and FMC bending stiffness was 65% (P <.05). These 8 mm FMC percentages are comparable to human IN fracture model construct values, indicating that the 8 mm IN/four screw construct should provide adequate stabilization for many canine diaphyseal femoral fractures.     

Antimicrobial resistance and population structure of Staphylococcus epidermidis recovered from pig farms in Belgium

Pigs are known to harbour a variety of staphylococcal bacteria, including Staphylococcus epidermidis, in the upper respiratory tract. The aim of the present study was to determine the prevalence, genetic diversity, virulence and antimicrobial resistance of S. epidermidis in healthy pigs, as well as to identify the potential role of pigs as a reservoir of zoonotic infection.The overall prevalence of S. epidermidis carriage was 28%, with approximately half of the pigs tested (13.5%) carrying methicillin-resistant S. epidermidis (MRSE). Some isolates belonged to multilocus sequence types, associated with healthy human carriers or healthcare personnel (ST88, ST210) whereas others were related to animal or environmental strains (ST100, ST273). Most MRSE isolates carried SCCmec type IV, with SCCmec type V or a non-typeable SCCmec detected in the remaining isolates. Both MRSE and methicillin-susceptible S. epidermidis isolates showed a degree of antimicrobial resistance, with most resistant to tetracycline and/or trimethoprim antimicrobial drugs. Isolates subjected to micro-array analysis carried the antimicrobial resistance genes tet(K), tet(M) and dfrS1, while half carried the arginine catabolic element (ACME) associated with colonisation. Some MRSE ST273 strains also carried the ica operon involved in biofilm formation. These research findings provide insight into the population structure and characteristics of S. epidermidis carried by healthy pigs, suggesting a role for these strains as a potential reservoir for antimicrobial and virulence genes and indicating that exchange of strains might occur between pigs and humans.     

Evaluation of plate luting, using an in vivo ovine osteotomy model

Bilateral, midshaft metacarpal osteotomies were performed in 11 sheep and bilateral, midshaft radial osteotomies were performed in 7 sheep. The lesions were repaired with bone plates. One of each pair of plates was luted with polymethylmethacrylate and all screws were tightened uniformly with a torque screwdriver. Sheep were allowed unrestricted exercise after surgery. At 8 weeks, 10 of 11 sheep with metacarpal osteotomies were sound and both osteotomies were healing. Seven were lame on the limb with the unluted plate during the first 3 weeks; 4 were never lame on either limb. The screws of the unluted plates were significantly (P less than 0.01) looser at 8 weeks than those in the luted plates. All of the sheep with radial osteotomies were lame in the limb with the unluted plate. Four of 7 sheep had overt loosening of the unluted plates. One sheep only had mild screw loosening with continued alignment of the osteotomy. Two of 7 sheep fractured the radius with the luted plate; these 2 sheep were lame in the limb with the unluted plate and were using the limb with the luted plate vigorously. Excluding the 2 sheep with fractures, all had substantially more screw loosening in the unluted plate. Histologically, there were no discernible differences in the vascularity or porosity of the bone under the luted vs the unluted plates. The only adverse consequence of the luting technique was introduction of a small amount of polymethylmethacrylate into the osteotomy gap in 5 bones.     

Characterisation of biofilm formation by a Streptococcus suis meningitis isolate

Biofilm formation by a strain of Streptococcus suis serotype 2 isolated from a case of meningitis in pigs was characterised. Using a polystyrene microtitre plate assay, S. suis 95-8242 produced a dense biofilm when glucose, fructose or sucrose was used as the carbohydrate source, whereas no biofilm formed in the presence of lactose. Polysaccharide production by the biofilm-forming strain was demonstrated by the Congo red agar assay. Transmission electron microscopy revealed that bacterial cells were surrounded by a thick layer of polycationic ferritin-labelled material. S. suis 95-8242 was more resistant to both penicillin G and ampicillin in biofilms than in planktonic cultures on the basis of minimal inhibitory and minimal bactericidal concentrations.