Comparison of scanning electron microscopy findings regarding biofilm colonization with microbiological results in nasolacrimal stents for external, endoscopic and transcanalicular dacryocystorhinostomy

Characteristics of Bacterial Biofilm Formation in Nasolacrimal Silicone Tubes Post-dacryocystorhinostomy

PURPOSE

To examine the biofilm formation characteristics of bacteria identified at the genus level in samples obtained from silicone tubes after dacryocystorhinostomy surgery.

METHODS

In the study involving consecutive patients who underwent dacryocystorhinostomy surgery at Ankara Bilkent City Hospital and whose silicone tubes were removed six months after surgery, between January 2023 and May 2023; the tubes were placed in glycerol-PBS (phosphate buffered saline) solution and cultured on descriptive selective media at the genus level. The biofilm-forming properties of the obtained isolates were examined in solid-air and liquid-air interphases. Salmonella Typhimurium ATCC SL1344 strain was used as the control bacterium.

RESULTS

As a result of the analysis of the samples taken from the patients, Pseudomonas spp. was identified in three of the samples, Staphylococcus spp. in five of the samples, and Streptococcus spp. in one of the samples. Among these samples, except for the bacteria identified in samples one and five, the rest were found to be strong biofilm producers. In all strong biofilm producers, the maximum biofilm production time was determined as 72 h and the incubation temperature was 37°C. The presence of cellulose and amyloid proteins in biofilm matrix structures is identified. Swimming and swarming motilities were observed in all bacterial samples.

CONCLUSION

Since biofilms are considered potential factors in the pathogenesis of infectious and inflammatory diseases, they are a subject that needs to be thoroughly investigated. In our study, although there were no clinical infections in any of the patients, biofilm formation was detected in the patient samples. The fact that the bacteria exhibited moderate to strong biofilm formation characteristics suggests that these microorganisms could be persistent infectious agents.

Scanning electron microscopic features of lacrimal drainage silastic stents: Comparison of various Crawford and large-diameter stents

PURPOSE

This study aimed to examine the differences in the biofilms and physical deposits on Crawford stents compared to large-diameter stents.

METHODS

A prospective interventional study was performed on a series of patients undergoing external or endoscopic dacryocystorhinostomy (DCR) and endoluminal lacrimal duct recanalization (ELDR) with either Crawford or large-diameter stents. All the Crawford stents were retrieved at six weeks and the large-diameter ones at eight weeks following the surgical intervention. There was no evidence of post-operative infection in any of the patients. Following extubation, standard protocols of scanning electron microscopy were used to assess the biofilms and physical deposits on the stents.

RESULTS

A total of 15 stents were studied. Of these, twelve were Crawford, and three were large-diameter stents. The Crawford stents were from two different manufacturers. All the stents demonstrated evidence of biofilm formation and physical deposits. The Crawford stents showed thin biofilms and sparse physical deposits, but there were no demonstrable differences amongst stents from different manufacturers. However, the deposits and biofilms were thicker and more extensive in the large-diameter stents than the Crawford ones. The biofilms from all stents showed the presence of polymicrobial communities within the exopolysaccharide matrix.

CONCLUSIONS

The present study found differences in biofilms and physical deposits between Crawford and large-diameter stents. These differences can be partly explained by stent duration, size, and their tissue interactions.

Comparative outcomes of the pathogen in cultured Jones tubes used in lacrimal bypass surgery according to follow up periods

AIM

To evaluate the pathogens in cultured Jones tubes used in lacrimal bypass surgery according to the postoperative periods and to obtain data for the prevention of infection of functional lacrimal stent invention.

METHODS

Totally 71 patients (81 eyes) who underwent the removal of Jones tubes were enrolled in study. All the removed Jones tubes were cultured for bacterial and fungal identification and tested for bacterial antibiotic sensitivity. The results were analyzed according to the duration of the inserted Jones tube after lacrimal bypass surgery.

RESULTS

Of the 81 eyes, bacteria were isolated from 69 eyes (85.2%) and fungi from 6 eyes (7.4%). Among 69 eyes, 40.6% showed Staphylococcus aureus (S. aureus), 11.6% were Pseudomonas aeruginosa (P. aeruginosa). Gram-positive bacteria were isolated more than Gram-negative bacteria, but Gram-negative bacteria showed a higher incidence in the Jones tube implanted for over 10y (P=0.035). The antibiotic sensitivity test showed that 46.4% of S. aureus were resistant to oxacillin. In terms of antibiotics commonly used in ocular clinical practice, vancomycin was sensitive to S. aureus and Streptococcus pneumoniae (S. pneumoniae), amikacin responded to P. aeruginosa and Proteus mirabilis (P. mirabilis). Trimethoprim/sulfamethoxazole (TMP/SMX) was all sensitive to S. aureus, S. pneumoniae and P. mirabilis except P. aeruginosa.

CONCLUSION

S. aureus is the most commonly found organism in the Jones tube after lacrimal bypass surgery, and 46.4% of them are methicillin-resistant S. aureus (MRSA), sensitive to vancomycin. Especially, P. mirabilis responded with amikacin is dominantly detected in the Jones tubes implanted for more than 10y.

Species-specific characteristics of the biofilm generated in silicone tube: an in vitro study

Background

To investigate characteristics of biofilm which is usually found in silicone tube for nasolacrimal duct surgery and can be the root of chronic bacterial infections eventually resulted in surgical failure.

Methods

To form a biofilm, sterile silicone tube was placed in culture media of Staphylococcus aureus, Corynebacterium matruchotii, Pseudomonas aeruginosa, or Streptococcus pneumonia. Biofilms formed on these silicone tubes were fixed with 95% ethanol and stained with 0.1% crystal violet. After staining, the optical densities of biofilms were measured using spectrophotometer on a weekly basis for 12 weeks.

Results

Staphylococcus aureus group and Pseudomonas aeruginosa group formed significantly more amounts of biofilms compared to the control group. The maximum optical densities of the two groups were found on week 3–4 followed by a tendency of decrease afterwards. However, the amounts of biofilms formed in other groups of silicone tubes were not statistically significant from that of the control group.

Conclusions

Bacterial species that could form biofilm on silicone tube included Staphylococcus aureus (week 3) and Pseudomonas aeruginosa (Week 4). It is important to first consider that the cause of infection around 1 month after silicone tube intubation can be Staphylococcus aureus and Pseudomonas aeruginosa.

Yeast Surface Display of Escherichia coli Enterotoxin and Its Effects of Intestinal Microflora and Mucosal Immunity

Enterotoxigenic Escherichia coli (ETEC) is a significant cause of infectious diarrhea in animals. In this study, yeast surface display technology was employed to investigate the effects of ETEC enterotoxin fusion protein on the intestinal flora and mucosal immunity of rats. ETEC estA, estB, and eltAB (heat-labile and heat-stable toxins) were expressed on the surface of yeast. Rats were divided into normal saline, yeast and display yeast groups. Fecal and jejunal content samples were collected on the 7th, 14th, and 21st days. Rats were then fed ETEC for 3 days before again collecting these samples. Levels of SIgA, IL-2, IL-4, IFN-γ, and microbial population density and diversity were documented by ELISA, T-RFLP and real-time PCR. The results demonstrated that estA, estB, and eltAB fusion proteins were expressed on the surface of yeast. Following ETEC challenge, levels of SIgA, IL-2, IL-4, IFN-γ, and, the numbers and variety of intestinal microbes were significantly increased in rats receiving display yeast and yeast. These factors were significantly decreased in rats given normal saline and yeast. Our results indicate that display yeast and yeast can increase the number and diversity of intestinal microbes in rats and improve intestinal immune function. After ETEC challenge, the display yeast can better maintain the balance of intestinal bacteria and mucosal immunity.

Conjunctival bacterial flora in fellow eyes of patients with unilateral nasolacrimal duct obstruction and its changes after successful dacryocystorhinostomy surgery

PURPOSE

To evaluate the results of conjunctival culture in fellow eyes of patients with unilateral nasolacrimal duct obstruction (NLDO) and its changes after successful dacryocystorhinostomy (DCR) surgery.

METHODS

In this prospective study, 71 adult patients with unilateral NLDO and 41 age and sex-matched controls without NLDO were evaluated. The patients were divided into 2 groups based on clinical examination; group A with purulent regurgitation and group B without purulent regurgitation. They all underwent DCR. Before DCR surgery, microbiologic specimens were taken bilaterally from the conjunctiva of both eyes. Postoperative conjunctival sampling was continued weekly until the culture became negative or the colony count reached to the range of the control group.

RESULTS

There were 38 and 33 patients in groups A and B, respectively. Silicone tube was inserted for 17 patients (23.9%). The culture was positive for bacterial growth in 56 fellow eyes (79%). The conjunctival culture in the control group was positive in 17 eyes (41.4%). The mean count of colonies in a sample unit was 624.73 ± 2412.31, 195.75 ± 407.56, and 9.5 ± 1.5 for group A, group B, and controls, respectively. The mean time of normalization of specimens was 1.43 ± 0.69 weeks (range 1-4). Higher colony count at baseline and presence of silicone tube in infected eye were significantly associated with longer normalization time for fellow eye (P < 0.001 and P = 0.003 respectively).

CONCLUSIONS

This study suggests that after successful DCR surgery, a waiting period of 4 weeks is needed for conjunctival bacterial cultures to become negative or reach the level of the normal eyes, in the fellow eyes of patients with unilateral NLDO.

Biofilms in infections of the eye

The ability to form biofilms in a variety of environments is a common trait of bacteria, and may represent one of the earliest defenses against predation. Biofilms are multicellular communities usually held together by a polymeric matrix, ranging from capsular material to cell lysate. In a structure that imposes diffusion limits, environmental microgradients arise to which individual bacteria adapt their physiologies, resulting in the gamut of physiological diversity. Additionally, the proximity of cells within the biofilm creates the opportunity for coordinated behaviors through cell–cell communication using diffusible signals, the most well documented being quorum sensing. Biofilms form on abiotic or biotic surfaces, and because of that are associated with a large proportion of human infections. Biofilm formation imposes a limitation on the uses and design of ocular devices, such as intraocular lenses, posterior contact lenses, scleral buckles, conjunctival plugs, lacrimal intubation devices and orbital implants. In the absence of abiotic materials, biofilms have been observed on the capsule, and in the corneal stroma. As the evidence for the involvement of microbial biofilms in many ocular infections has become compelling, developing new strategies to prevent their formation or to eradicate them at the site of infection, has become a priority.