Ocular infections due to anaerobic bacteria

Conjunctival sac microbiome in anophthalmic patients: Flora diversity and the impact of ocular prosthesis materials

Purpose

To explore the changes of bacterial flora in anophthalmic patients wearing ocular prosthesis (OP) and the microbiome diversity in conditions of different OP materials.

Methods

A cross-sectional clinical study was conducted, involving 19 OP patients and 23 healthy subjects. Samples were collected from the upper, lower palpebral, caruncle, and fornix conjunctiva. 16S rRNA sequencing was applied to identify the bacterial flora in the samples. The eye comfort of each OP patient was determined by a questionnaire. In addition, demographics information of each participant was also collected.

Results

The diversity and richness of ocular flora in OP patients were significantly higher than that in healthy subjects. The results of flora species analysis also indicated that in OP patients, pathogenic microorganisms such as Escherichia Shigella and Fusobacterium increased significantly, while the resident flora of Lactobacillus and Lactococcus decreased significantly. Within the self-comparison of OP patients, compared with Polymethyl Methacrylate (PMMA), prosthetic material of glass will lead to the increased colonization of opportunistic pathogens such as Alcaligenes, Dermabacter and Spirochaetes, while gender and age have no significant impact on ocular flora.

Conclusions

The ocular flora of OP patients was significantly different from that of healthy people. Abundant colonization of pathogenic microorganisms may have an important potential relationship with eye discomfort and eye diseases of OP patients. PMMA, as an artificial eye material, demonstrated potential advantages in reducing the colonization of opportunistic pathogens.

Ocular bacterial infections: Pathogenesis and diagnosis

The human eye is a rigid asymmetric structure with unique defence system. Despite considerable resident microbiota, eye is exposed to external environment where a range of microorganisms also inhabits. Opportunistically, some of these microorganisms could associate with eye pathogen that could contact incidentally, leading to destructive visual consequences. Among such microbiota, bacteria form the major proportion concerning ocular complications worldwide. The succession of genome based approach through 16S rRNA gene based identification tremendously augmented the knowledge on diversity of ocular surface bacteria. Such evidence suggests that while few bacteria contribute towards normal ocular functions, considerable number of bacteria play active role in pathophysiology of ocular diseases. Thus, understanding the complexity of ocular microflora not only throw light on their critical role towards normal function of the eye, but also enlighten on certain visual exigencies. Under these circumstances, development of a rapid, reliable and cost effective method is essential that eventually evolve as a routine diagnostic protocol. Such precise prognostic modalities facilitate ophthalmologists to formulate pioneering therapeutics towards challenging ocular diseases.

A study on the characterization of Propionibacterium acnes isolated from ocular clinical specimens

Background & objectives:

There are only a few reports available on characterization of Propionibacterium acnes isolated from various ocular clinical specimens. We undertook this study to evaluate the role of P. acnes in ocular infections and biofilm production, and also do the phylogenetic analysis of the bacilli.

Methods:

One hundred isolates of P. acnes collected prospectively from ocular clinical specimens at a tertiary care eye hospital between January 2010 and December 2011, were studied for their association with various ocular disease conditions. The isolates were also subjected to genotyping and phylogenetic analysis, and were also tested for their ability to produce biofilms.

Results:

Among preoperative conjunctival swabs, P. acnes was a probably significant pathogen in one case; a possibly significant pathogen in two cases. In other clinical conditions, 13 per cent isolates were probably significant pathogens and 38 per cent as possibly significant pathogens. The analysis of 16S rRNA gene revealed four different phylogenies whereas analysis of recA gene showed two phylogenies confirming that recA gene was more reliable than 16S rRNA with less sequence variation. Results of polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) had 100 per cent concordance with phylogenetic results. No association was seen between P. acnes subtypes and biofilm production.

Interpretation & conclusions:

RecA gene phylogenetic studies revealed two different phylogenies. RFLP technique was found to be cost-effective with high sensitivity and specificity in phylogenetic analysis. No association between P. acnes subtypes and pathogenetic ability was observed. Biofilm producing isolates showed increased antibiotic resistance compared with non-biofilm producing isolates.

Proteus mirabilis and its role in dacryocystitis

PURPOSE

Dacryocystitis is a common inflammation of the lacrimal sac, usually from an underlying bacterial infection. Most cases can be attributed to common ocular flora such as Staphylococcus aureus or Streptococcus pneumoniae; however, uncommon bacterial causes such as Proteus mirabilis can still occur. P. mirabilis is a gram-negative bacillus that is found abundantly in people who have undergone long-term catheterization and is uncommonly found in or around the eyes except in people who have undergone long-term catheterization. Proteus species can cause conjunctivitis, canaliculitis, and dacryocystitis and have the ability to manifest into preseptal cellulitis; therefore, timely recognition and treatment are important to prevent potential further complications.

CASE REPORT

An 84-year-old white man had several recurrences of acute dacryocystitis that had marginal improvement with empiric antibiotic treatment. Resultant culture of the ocular discharge revealed an uncommon bacterium, P. mirabilis. Successful dosing of oral antibiotics resolved the infection but ultimately the patient required an external dacryocystorhinostomy (DCR) procedure to maintain patency of the nasolacrimal lacrimal system and prevent recurrence. At 3 months after external DCR, the patient was symptom free with no recurrences.

CONCLUSIONS

Dacryocystitis has a distinctive clinical presentation and is usually easily treated when appropriate oral antibiotics are directed at the underlying pathogen. In nonresponsive cases, culturing of the ocular discharge should be performed to identify the underlying pathogen. Cases of dacryocystitis caused by Proteus species are usually responsive to several standard antibiotics used orally in eye care; however, culturing and susceptibility testing can streamline the diagnostic and management sequence considerably in unclear or unresponsive cases. Typically, patients with dacryocystitis return to normal after appropriate treatment, but chronic recurrences and epiphora are potential sequelae. Patients should be educated that a DCR surgical procedure may be needed to prevent future recurrences in some cases.

Conjunctivitis: systematic approach to diagnosis and therapy

Conjunctivitis is a common problem in primary health care. Inflammation of the conjunctiva may result from infection or noninfectious causes. Microbial conjunctivitis may be caused by bacteria, viruses, or parasites. Although usually a benign, self-limited disease in healthy individuals, serious complications (eg, keratitis) may be sight-threatening. Accurate diagnosis and specific treatment of conjunctivitis remain challenging. History taking and physical examination are occasionally insufficient for correct diagnosis, thus laboratory testing may play a vital role in identification of specific pathogen(s). However, diagnostic testing has several limitations, including time-consuming methods, increased cost, and requirement for expertise in performance and interpretation. Treatment with empirical topical antibiotics for suspected infectious conjunctivitis is controversial. Although antibiotic treatment can diminish risk of adverse events and shorten the course of disease, drug resistance, toxicity, and expense are important considerations in management of acute infectious conjunctivitis.

The timing of antibiotic administration in the management of infant dacryocystitis

PURPOSE

To report (1) the prevalence of bacteremia among infants with dacryocystitis and (2) the influence of timing of antibiotic administration on the need for repeat probing in the management of these patients.

METHODS

A retrospective analysis of the hospital records of 25 infants < or =6 weeks of age treated for acute dacryocystitis was conducted, including analysis of laboratory data and outcomes.

RESULTS

Of 22 infants who underwent blood cultures, 5 (22.7%) were bacteremic. Twenty-one of the 25 infants underwent nasolacrimal duct probing. Infants who received preoperative antibiotics were less likely to require a repeat probing than those who did not (6% vs. 80%), and this difference was statistically significant (p = 0.004).

CONCLUSIONS

The high rate of bacteremia in this series of patients and the significantly lower incidence of repeat probing among infants who received preprocedural antibiotics suggests that blood cultures and subsequent administration of intravenous antibiotics should be considered prior to probing of infants with dacryocystitis.

Early bacterial keratitis after presbyopic LASIK

PURPOSE

To report an unusual case of infectious keratitis that occurred after presbyopic laser-assisted in situ keratomileusis (LASIK).

METHODS

A 57-year-old woman presented with decreased visual acuity and pain in her right eye 2 days after a bilateral presbyopic LASIK procedure. Slit-lamp examination showed a large corneal infiltrate surrounded by marked corneal inflammation. Corneal scraping grew Propionibacterium acnes.

RESULTS

Under topical and systemic antibiotic treatment, the infiltrate slowly resolved. Visual acuity improved from counting fingers at presentation to 20/30 after 8 months of follow-up.

CONCLUSIONS

To the best of our knowledge, this is the first description of a P. acnes infection after LASIK and the first case of infection complicating a presbyopic LASIK procedure. Although infectious keratitis occurs rarely after refractive surgery, patients should be informed of the potential risk of visual loss caused by such infections.

Antimicrobial resistance and the management of anaerobic infections

Management of anaerobic infections encompasses surgical procedures, antibacterial therapy and adjuncts. At present, metronidazole, penems, beta-lactam/beta-lactamase inhibitor combinations and chloramphenicol have the highest activity against obligate anaerobes. Tigecycline is a promising new agent. Other antibacterials (e.g., nitazoxanide, moxifloxacin, garenoxacin and ramoplanin) and nonantibiotic agents show potential but need further investigation. The patient's characteristics, mixed anaerobic/aerobic infections, infection sites, bacterial resistance patterns, bactericidal activity of agents and their pharmacokinetics, toxicity and influence on the normal flora should be considered. Susceptibility patterns of anaerobes have become less predictable owing to increasing antibacterial resistance. Emergence of highly virulent or multidrug-resistant strains is challenging the current therapy. To counteract these trends, regular resistance surveillance in anaerobes, rational antibiotic use and evaluation of new treatment alternatives are important.