Comparison of azithromycin and moxifloxacin against bacterial isolates causing conjunctivitis

Prevalence of antimicrobial-resistant Cutibacterium isolates and development of multiplex PCR method for Cutibacterium species identification

INTRODUCTION

Cutibacterium species such as C. acnes, C. avidum, and C. granulosum are known anaerobic skin inhabitants and often cause surgical site infections. These species are genetically similar and are difficult to identify rapidly. In addition, their pathogenicity and antimicrobial resistance remain unknown. In this study, antimicrobial resistance in Cutibacterium isolates was studied and a multiplex PCR method for their identification was developed.

METHODS

A total of 497 C. acnes, 71 C. avidum, and 25 C. granulosum strains which were isolated from the acne pustule and infectious regions, were used.

RESULTS

The antimicrobial resistance rates of C. acnes, C. avidum, and C. granulosum strains isolated from patients with acne vulgaris were higher than those of strains isolated from patients with infectious diseases. In particular, macrolide-clindamycin-resistant strains were isolated most frequently from all species. Among the resistant strains, strains with 23S rRNA mutations were the most common in C. acnes (24.3%, 71/292), whereas C. avidum and C. granulosum strains were most frequently found with erm(X). For the first time, a C. granulosum strain carrying pTZC1, which codes erm(50) and tet(W), was isolated from patients with acne vulgaris. Regarding the rapid identification of causative pathogens from infectious regions, three Cutibacterium species were identified with 100% sensitivity and specificity using multiplex PCR method.

CONCLUSIONS

Our data showed that antimicrobial resistance differed among Cutibacterium species. The multiplex PCR method may contribute to the rapid detection of Cutibacterium species and selection of appropriate antimicrobial agents.

A Systematic Review of Multi-decade Antibiotic Resistance Data for Ocular Bacterial Pathogens in the United States

INTRODUCTION

Since 2009, the Antibiotic Resistance Monitoring in Ocular Microorganisms (ARMOR) surveillance study has been assessing in vitro antibiotic resistance for bacterial isolates sourced from ocular infections in the US. The main goal of this systematic review was to compare in vitro resistance data for ocular pathogens from published US studies with the most recently published data from the ARMOR study (2009-2018) and, where possible, to evaluate trends in bacterial resistance over time over all studies.

METHODS

A literature search was conducted using MEDLINE®, BIOSIS Previews®, and EMBASE^® databases (1/1/1995-6/30/2021). Data were extracted from relevant studies and antibiotic susceptibility rates for common ocular pathogens (Staphylococcus aureus, coagulase-negative staphylococci [CoNS], Streptococcus pneumoniae, Pseudomonas aeruginosa, and Haemophilus influenzae), longitudinal changes in susceptibility, and multidrug resistance (MDR) were compared descriptively.

RESULTS

Thirty-two relevant studies were identified. High in vitro resistance was found among S. aureus and CoNS to fluoroquinolones, macrolides, and methicillin/oxacillin across studies, with high rates of MDR noted, specifically among methicillin-resistant staphylococci. Data from studies pre-dating or overlapping the early years of ARMOR reflected increasing rates of S. aureus resistance to fluoroquinolones, macrolides, methicillin/oxacillin, and aminoglycosides, while the ARMOR data suggested slight decreases in resistance to these classes between 2009 and 2018. Overall, methicillin-resistant S. aureus (MRSA) prevalence peaked from 2005 to 2015 with a possible decreasing trend in more recent years.

DISCUSSION AND CONCLUSIONS

Data from local and regional US datasets were generally consistent with data from the national ARMOR surveillance study. Continued surveillance of ocular bacterial pathogens is needed to track trends such as methicillin resistance and MDR prevalence and any new emerging antibiotic resistance phenotypes. Susceptibility data from ARMOR can inform initial choice of therapy, especially in practice areas where local antibiograms are unavailable.

Antibacterial effects of antibiotics and cell-free preparations of probiotics against Staphylococcus aureus and Staphylococcus epidermidis associated with conjunctivitis

Conjunctivitis, caused by bacterial infections, represents health concern and diagnosis of the disease is pivotal for the proper selection of the treatment. The main causes of bacterial conjunctivitis vary in different countries. The current study investigated the common bacterial causes of bacterial conjunctivitis from eye clinics' attendants and evaluated the effectiveness of different therapeutic approaches. Eye swabs from patients, diagnosed with conjunctivitis, were assessed microbiologically and the isolated bacteria were identified using the standard biochemical identification and sequencing of the 16S rRNA gene. Antibiotics' susceptibility of the conjunctivitis-associated bacterial pathogens was evaluated against nineteen broad-spectrum antibiotics. In the meanwhile, cell-free preparations from probiotic Lactobacillus and Bifidobacterium strains were used to evaluate their antagonistic activities. Findings from this study showed that out of 52 specimen, 17 eye swabs from patients with conjunctivitis were bacterial culture-positive. The identity of the bacterial species, using the biochemical identification system, was Staphylococcus aureus (4 isolates) and S. epidermidis (13 isolates). Staphylococcus spp. showed susceptibility to linezolid, vancomycin, novobiocin, and fluoroquinolones (norfloxacin, ofloxacin, ciprofloxacin and levofloxacin). However, isolates from the two Staphylococcus spp. expressed resistance to penicillin G, oxacillin, and cephalexin. As alternatives to antibiotics, the growth of Staphylococcus spp., including isolates with antibiotic resistance, was inhibited by cell-free preparations of the 4 probiotic Lactobacillus and the 2 Bifidobacterium strains. These findings provide evidence that topical antibiotics such as fluoroquinolones are still effective antimicrobial agents against staphylococci associated with conjunctivitis whereas probiotic preparations could be promising for further research to pave the way for their therapeutic applications against ophthalmic diseases.

Azithromycin 1.5% ophthalmic solution: in purulent bacterial or trachomatous conjunctivitis

The second-generation macrolide azithromycin is available as a 1.5% ophthalmic solution for use in the treatment of bacterial or trachomatous conjunctivitis. This article reviews the pharmacological properties of azithromycin 1.5% ophthalmic solution and its clinical efficacy and tolerability in patients with purulent bacterial conjunctivitis or trachomatous conjunctivitis caused by Chlamydia trachomatis. Azithromycin 1.5% ophthalmic solution had good in vitro activity against Haemophilus influenzae and C. trachomatis, and achieved good concentrations in tear samples from healthy volunteers. Azithromycin 1.5% ophthalmic solution for 3 days (1 drop twice daily) was noninferior to tobramycin 0.3% ophthalmic solution for 7 days (1 drop every 2 hours) in paediatric and adult patients with purulent bacterial conjunctivitis, with regard to clinical cure and bacteriological resolution on day 9, in a randomized, investigator-masked, multicentre study. In children with trachomatous inflammation, 3-day treatment with azithromycin 1.5% ophthalmic solution was noninferior to a single dose of azithromycin oral suspension, with regard to clinical cure rate in the worst eye at 60 days, in a randomized, double-masked, multicentre study. Azithromycin 1.5% ophthalmic solution was well tolerated in patients with bacterial or trachomatous conjunctivitis. Most events were of mild to moderate severity.

Propionibacterium acnes: infection beyond the skin

Propionibacterium acnes is a Gram-positive bacterium that forms part of the normal flora of the skin, oral cavity, large intestine, the conjunctiva and the external ear canal. Although primarily recognized for its role in acne, P. acnes is an opportunistic pathogen, causing a range of postoperative and device-related infections. These include infections of the bones and joints, mouth, eye and brain. Device-related infections include those of joint prostheses, shunts and prosthetic heart valves. P. acnes may play a role in other conditions, including inflammation of the prostate leading to cancer, SAPHO (synovitis, acne, pustulosis, hyperostosis, osteitis) syndrome, sarcoidosis and sciatica. If an active role in these conditions is established there are major implications for diagnosis, treatment and protection. Genome sequencing of the organism has provided an insight into the pathogenic potential and virulence of P. acnes.

Topical ophthalmic moxifloxacin elicits minimal or no selection of fluoroquinolone resistance among bacteria isolated from the skin, nose, and throat

PURPOSE

To investigate whether moxifloxacin therapy of bacterial conjunctivitis in children changes the moxifloxacin susceptibility of bacterial isolates in eyes, cheeks below eyes, nares, and throat.

METHODS

Patients (age: 1 to 12 years, n = 105) with bacterial conjunctivitis were treated topically with moxifloxacin three times a day for 7 days. Gender- and age-matched subjects with normal eyes (age: 1 to 12 years, n = 57) served as the control group. Microbiological specimens were collected on days 1 (prior to therapy), 8 (1 day after end of therapy), and 42 (follow-up). Specimens were processed to recover total bacteria and bacteria that grew on fluoroquinolone-selective media. Bacteria were identified to the species level and susceptibility to moxifloxacin and selected other antibiotics determined.

RESULTS

The primary pathogens recovered from the infected eyes on day 1 before therapy were Haemophilus influenzae, Streptococcus pneumoniae, and Staphylococcus aureus. None of the pre-therapy isolates of H. influenzae and S. pneumoniae were resistant to moxifloxacin. Isolates of these two pathogenic species were also recovered primarily from the nose and eyes. Moxifloxacin-resistant S. aureus isolates (minimum inhibitory concentration 1.0 μg/mL or greater) were recovered from the nose and throat prior to topical dosing on day 1. However, there was no change in the frequency of moxifloxacin-resistant isolates of S. aureus following treatment with moxifloxacin.

CONCLUSION

Treatment of conjunctivitis with topical ophthalmic moxifloxacin did not select for moxifloxacin resistance in H. influenzae, S. pneumoniae, or S. aureus in the eye or distal body sites.

The role of topical moxifloxacin, a new antibacterial in Europe, in the treatment of bacterial conjunctivitis

This article discusses current practice in the treatment of conjunctivitis and how the use of topical moxifloxacin can increase therapeutic effectiveness, reduce treatment failures and, consequently, be cost effective and reduce the societal burden of the disorder. Current practice and effectiveness data were derived from the literature. Data on healthcare utilization as a result of treatment failure were collected by survey and the cost of treatment was defined using national costings. A decision-analytic model to assess cost effectiveness was developed and the impact on the healthcare budget was calculated to define the health economic impact. Bacterial conjunctivitis represents a significant health problem and accounts for an estimated 1-1.5% of primary-care consultations. The disorder is highly contagious and causes a substantial healthcare and societal burden. Bacterial conjunctivitis is generally self-limiting, resolving within 1-2 weeks. However, the use of antibacterials significantly improves clinical and microbiological remission, shortens symptom duration, and enables more effective use of healthcare resources, compared with placebo. From a health economic perspective this benefits the healthcare system and society, since fewer healthcare resources are needed and the adult affected, or the parent/caregiver of the child affected, can return to full work capacity sooner, reducing loss of productivity. Treatment strategies vary significantly between countries. Most patients are first seen in primary care, where 'wait-and-see', lubrification and antiseptic or antibacterial treatment is provided. In Europe, when antibacterials are prescribed most general practitioners (GPs) prescribe a broad-spectrum topical antibacterial. The most commonly used drugs are chloramphenicol and fusidic acid, with fluoroquinolones rarely reported as first-line treatment by GPs. At the specialist (ophthalmologist) level, or for second-line treatment at the GP level, topical antibacterials are frequently used. However, in most countries, topical fluoroquinolones, particularly those recently approved by the European Medicines Agency, such as topical levofloxacin and topical moxifloxacin, are rarely used and instead are reserved for use as a last resort. In other parts of the world topical lomefloxacin, gatifloxacin and/or besifloxacin are also available. The strategy of using novel topical fluoroquinolones as a last resort reflects a belief that the use of topical fluoroquinolones may enhance the development of resistance, jeopardizing future availability of antibacterial treatment for ocular infections. In fact, most cases of bacterial resistance arise as a result of systemic treatment. Thus, this concern should not be extrapolated to topical use of fluoroquinolones, which results in antibacterial concentrations at the ocular surface that can significantly exceed mutant prevention concentrations. In addition, with products such as topical moxifloxacin, a dual-step mutation is required for resistance to emerge. Moxifloxacin restricts the selection of resistant mutants, meaning that emergence of resistance is unlikely. The strategy of not using the most effective fluoroquinolones such as topical moxifloxacin may lead to more patients with no improvement or worsening of symptoms, requiring re-intervention, additional examination and new treatment; these outcomes are defined as 'treatment failures'. Treatment failures cause an extra societal burden and increased costs due to the extra healthcare resources required (additional GP/specialist visits, laboratory tests, additional treatment, etc.). Compared with non-fluoroquinolones, topical moxifloxacin has a higher potency and faster in vitro 'speed-to-kill'. It has also been shown that, within the fluoroquinolone class, topical moxifloxacin and besifloxacin achieve the highest mean concentrations in conjunctival tissue, have the longest residence times and display favourable area under the concentration-time curve from time zero to 24 hours (AUC(24))/minimum inhibitory concentration ratio required to inhibit the growth of 90% of organisms (MIC(90)) and thus favourable pharmacokinetic/pharmacodynamic characteristics. This can result in reduced time-to-cure and a lower number of treatment failures, leading to better disease management and a healthcare-economic benefit arising from the associated reduction in utilization of healthcare resources. The high potency and mean concentration in conjunctival tissue combined with the long residence time of topical moxifloxacin enables a dosing strategy of three times daily for 5 days. Topical moxifloxacin is also the first ophthalmic antibacterial in Europe provided as a multidose, self-preserved, topical solution, thus avoiding the risk of benzalkonium chloride preservative-related allergic reactions and swelling. In addition, topical moxifloxacin has a near neutral pH (6.8) and is well tolerated by patients. Given the characteristics of the novel topical fluoroquinolones, a change in the healthcare treatment strategy for acute infectious conjunctivitis is to be recommended. Topical application of fluoroquinolones, such as moxifloxacin multidose self-preserved solution, should be considered earlier in the treatment path for conjunctivitis. Notwithstanding the premium price attached to this novel topical antibacterial, use of topical moxifloxacin for bacterial conjunctivitis can be cost effective and even generate total healthcare budget savings by reducing both the costs of managing treatment failures and the use of clinicians' time to manage such failures.

Common childhood bacterial infections

Children with infectious diseases are commonly encountered in primary care settings. Identification of the subset of patients with bacterial infections is key in guiding the best possible management. Clinicians frequently care for children with infections of the upper respiratory tract, including acute otitis media, otitis externa, sinusitis, and pharyngitis. Conjunctivitis is not an uncommon reason for office visits. Bacterial pneumonia, urinary tract infections, and gastroenteritis are regularly seen. Over the last decade, a growing number of children have had infections of the skin and soft tissue, driven by the increased prevalence of infections caused by methicillin-resistant Staphylococcus aureus. The following review addresses the epidemiology and risk factors for specific infections and examines the clinical presentation and selection of appropriate diagnostic methods in such conditions. Methods to prevent these bacterial infections and recommendations for follow-up are suggested. Management of these infections requires that antimicrobial agents be used in a judicious manner in the outpatient setting. Such antibiotic therapy is recommended using both available clinical evidence and review of disease-specific treatment guidelines.

Limitations of current antibiotics for the treatment of bacterial conjunctivitis

Bacterial conjunctivitis is a common ocular infection that is generally treated empirically with a broad-spectrum antibiotic. The more common pathogens causing bacterial conjunctivitis include Staphylococcus aureus, Haemophilus influenzae, Streptococcus pneumoniae, Staphylococcus epidermidis, and Moraxella species. Several antibiotics traditionally used to treat bacterial conjunctivitis are no longer widely prescribed because of increased bacterial resistance and/or safety concerns. The introduction of the fluoroquinolone class of anti-infectives offered effective and better tolerated treatment options. Nonetheless, successful therapy for bacterial conjunctivitis continues to be limited by several factors. A primary concern is the development of bacterial resistance that may be impacted not only by widespread antibiotic use but also by antibacterial pharmacokinetics, such as maintenance of insufficient bactericidal concentrations at the site of infection. In addition, poor adherence to prescribed regimens that require frequent administration, along with undesirable adverse events, affects the development of bacterial resistance and the success of treatment regimens. This article reviews current antibacterial agents used to treat bacterial conjunctivitis, factors that limit their successful use in treatment, and options for future development of more effective topical ophthalmic anti-infective agents.

Effectiveness, tolerability and safety of azithromycin 1% in DuraSite for acute bacterial conjunctivitis

PURPOSE

Bacterial eye infections are commonly treated with topical antibiotics, despite limited evidence of effectiveness. Azithromycin 1% in DuraSite((R)) is a new formulation of azithromycin in a gel polymer designed for use in acute bacterial conjunctivitis.

METHODS

We conducted systematic searches of the Cochrane Database of Clinical Trials, PubMed and Google Scholar to find randomized controlled trials of "azithromycin DuraSite((R))". These searches of published literature were supplemented with searches for unpublished trials and trials in progress.

RESULTS

We found six reports of randomized controlled trials investigating the role of azithromycin 1% in DuraSite((R)) for the management of acute bacterial conjunctivitis. The quality of these trials was judged to be moderate to high. These trials assessed effectiveness, tolerability and safety outcomes, but we found no trials looking at cost-effectiveness. DuraSite((R)) is a relatively stable formulation and so azithromycin 1% in DuraSite((R)) has a simpler dosing schedule than other available topical antibiotics. It appears to be similar to other topical antibiotics in its effectiveness, but minor side effects are quite common.

CONCLUSION

Acute bacterial conjunctivitis is a relatively mild, typically self-limiting, infection. Antibiotics should seldom be required. If, however, a decision to prescribe antibiotics is made, azithromycin 1% in DuraSite((R)) is likely to be broadly comparable in its effectiveness to most other antibiotics used to treat acute bacterial conjunctivitis. Further research is needed to determine its cost-effectiveness.

Efficacy and safety of besifloxacin ophthalmic suspension 0.6% in children and adolescents with bacterial conjunctivitis: a post hoc, subgroup analysis of three randomized, double-masked, parallel-group, multicenter clinical trials

BACKGROUND

Acute conjunctivitis is the most frequent eye disorder seen by primary care physicians and one that often affects children. Besifloxacin is a new topical fluoroquinolone, the first chlorofluoroquinolone, for the treatment of bacterial conjunctivitis.

OBJECTIVE

To examine the efficacy and safety of besifloxacin ophthalmic suspension 0.6% in patients aged 1-17 years with bacterial conjunctivitis.

METHODS

This was a post hoc analysis of a subgroup of pediatric patients aged 1-17 years who had participated in three previously reported, randomized, double-masked, parallel-group, multicenter, clinical trials evaluating the safety and efficacy of besifloxacin in the treatment of bacterial conjunctivitis. The studies were conducted in a community setting (clinical centers). All three clinical trials included children (aged > or = 1 year) with a clinical diagnosis of bacterial conjunctivitis in at least one eye, based on the presence at baseline of grade 1 or greater purulent conjunctival discharge and conjunctival injection, and pin-hole visual acuity of at least 20/200 in both eyes for verbal patients. Two trials were vehicle controlled; the third trial was comparator controlled (moxifloxacin hydrochloride ophthalmic solution 0.5% as base). In all studies, besifloxacin ophthalmic suspension 0.6% was administered as one drop in the affected eye(s) three times daily, at approximately 6-hourly intervals, for 5 days. The main outcome measures were clinical resolution and microbial eradication at visit 2 (day 4 +/- 1 in one study; day 5 +/- 1 in the other two studies) and visit 3 (day 8 or 9). Data from the two vehicle-controlled studies were combined for the assessments to provide greater statistical power.

RESULTS

This analysis included 815 pediatric patients aged 1-17 years (447 with culture-confirmed bacterial conjunctivitis). Clinical resolution was significantly greater (p < 0.05) in the besifloxacin group than in the vehicle group at both visit 2 (53.7% vs 41.3%) and visit 3 (88.1% vs 73.0%). Similarly, microbial eradication was significantly higher with besifloxacin than with vehicle at visit 2 (85.8% vs 56.3%) and visit 3 (82.8% vs 68.3%). No significant differences in clinical resolution and microbial eradication were noted between besifloxacin and moxifloxacin. Besifloxacin was well tolerated, with similar incidences of adverse events in the besifloxacin, vehicle, and moxifloxacin groups.

CONCLUSION

Besifloxacin ophthalmic suspension 0.6% was shown to be safe and effective for the treatment of bacterial conjunctivitis in children and adolescents aged 1-17 years.

Impact of antibiotic resistance in the management of ocular infections: the role of current and future antibiotics

Purpose:

This article reviews the effects of the increase in bacterial resistance on the treatment of ocular infections.

Design:

Interpretive assessment.

Methods:

Literature review and interpretation.

Results:

Ocular bacterial infections include conjunctivitis, keratitis, endophthalmitis, blepharitis, orbital cellulitis, and dacryocystitis. Treatment for most ocular bacterial infections is primarily empiric with broad-spectrum antibiotics, which are effective against the most common bacteria associated with these ocular infections. However, the widespread use of broad-spectrum systemic antibiotics has resulted in a global increase in resistance among both Gram-positive and Gram-negative bacteria to a number of the older antibiotics as well as some of the newer fluoroquinolones used to treat ophthalmic infections. Strategies for the prevention of the increase in ocular pathogen resistance should be developed and implemented. In addition, new antimicrobial agents with optimized pharmacokinetic and pharmacodynamic properties that have low toxicity, high efficacy, and reduced potential for the development of resistance are needed.

Conclusions:

New antimicrobial agents that treat ocular infections effectively and have a low potential for the development of resistance could be a part of strategies to prevent the global increase in ocular pathogen resistance.

The pharmacodynamic properties of azithromycin in a kinetics-of-kill model and implications for bacterial conjunctivitis treatment

INTRODUCTION

Antibiotics have traditionally been classified as bactericidal or bacteriostatic. Azithromycin belongs to the parent class of macrolides that are characteristically bacteriostatic. Some evidence suggests that this molecule demonstrates bactericidal kill and has concentration-dependent effects. This study tests the hypothesis that azithromycin demonstrates a bactericidal, concentration-dependent antibiotic effect at concentrations corresponding to and exceeding published tear and conjunctival levels.

METHODS

The antibacterial activity of different concentrations of azithromycin 1% in DuraSite(R) (AzaSite(R); Inspire Pharmaceuticals Inc, Durham, NC, USA) was evaluated using a kinetics-of-kill model. Recent conjunctivitis isolates of Staphylococcus aureus, Streptococcus pneumoniae or Haemophilus influenzae were exposed to four concentrations of azithromycin (100, 250, 500 and 750 microg/ml). Starting concentrations were similar to the maximum concentrations (Cmax) that have been demonstrated in conjunctiva (83 microg/g) and tears (288 microg/ml) following topical ocular administration. The percentage of surviving bacteria at 30 and 60 minutes following exposure to each concentration were determined.

RESULTS

Azithromycin failed to demonstrate bactericidal activity (i.e. a 3-log reduction in surviving bacteria) against S. aureus, S. pneumoniae or H. influenzae. Furthermore, the rate and extent of antibacterial activity with azithromycin did not change with higher concentrations, even at the highest tested concentration of 750 microg/ml.

CONCLUSION

Similar to the parent macrolide class, azithromycin demonstrates bacteriostatic activity against common conjunctival pathogens up to the maximum tested concentration of 750 microg/ml (i.e. 2.6-times and 9-times published Cmax tear and conjunctival concentration, respectively). Azithromycin's bacteriostatic effects and prolonged elimination half-life will likely lead to a corresponding increase in the emergence of macrolide-resistant isolates.

Speed of bacterial kill with a fluoroquinolone compared with nonfluoroquinolones: clinical implications and a review of kinetics of kill studies

It is important to rapidly eradicate bacteria in patients with bacterial conjunctivitis in order to decrease disease transmission, shorten symptom duration, and minimize the emergence of resistant bacteria. This paper presents the results of kinetics of kill studies on 3 commonly isolated pathogens in bacterial conjunctivitis. A more rapid speed of kill with moxifloxacin compared with other nonfluoroquinolone antibiotics (tobramycin, gentamicin, polymyxin B/trimethoprim, or azithromycin) was observed in Staphylococcus aureus, Streptococcus pneumoniae, and Haemophilus influenzae infections. Moxifloxacin achieved a 99.9% kill at approximately 1 h for S aureus, 2 h for S pneumoniae, and 30 min for H influenzae. In comparison, other nonfluoroquinolone therapies took longer to achieve a bactericidal (3-log) kill and some demonstrated no change or an increase in bacterial growth. Based on these findings, it is concluded that moxifloxacin kills bacteria more rapidly than nonfluoroquinolone topical ocular antibiotics.