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Infectious keratitis: causative microorganisms and how to detect them
Örebro University, School of Medical Sciences.ORCID iD: 0000-0003-1150-1751
2021 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

First, to describe the microbial spectrum in infectious keratitis by both a culture and a targeted sequencing approach; second, to describe the clinical and genetic characteristics of Corynebacterium macginleyi; and third, to study different aspects of the corneal culture process by comparing two instruments used for sampling and two sampling and inoculation strategies. 

The five studies in this thesis made use of two retrospective study populations and one prospective study population.

In the retrospective population the microbial spectrum by corneal culture was explored, Gram-positive bacteria, mainly coagulase-negative staphylococci, Staphylococcus aureus, and Corynebacterium spp. were commonly isolated. In the prospective study population, culture detected 13 different bacterial genera, while targeted sequencing identified a total of 168 different bacterial genera, with individual samples having a median of 13 (7–28) genera. Culture and sequencing showed an 82% agreement on the bacterial genera detected by culture. Genome sequencing and analysis of C. macginleyi revealed two different clades of which the minor clade (n=7), not previously described, exhibited a more complicated disease course. Cotton tipped applicators generated a significantly higher rate (44%) of positive corneal cultures on solid media than knife blades (31%). Direct transferal of multiple corneal samples to culture media generated a significantly higher rate of positive corneal cultures (61%) than indirect transferal through a single transport medium (44%).

In conclusion, the microbial spectrum in a Swedish population is similar to previously described in Europe, and C. macginleyi may be considered a corneal pathogen. Targeted sequencing may gain clinical application if further developed. The findings of this thesis indicate that a cotton tipped applicator may be sufficient for corneal sampling for direct inoculation, and the corneal culture procedure can be simplified from seven samplings on four different media to three samplings on two media.

Place, publisher, year, edition, pages
Örebro: Örebro University , 2021. , p. 95
Series
Örebro Studies in Medicine, ISSN 1652-4063 ; 250
Keywords [en]
Infectious keratitis, corneal culture, C. macginleyi, targeted sequencing
National Category
Surgery
Identifiers
URN: urn:nbn:se:oru:diva-93734ISBN: 9789175294087 (print)OAI: oai:DiVA.org:oru-93734DiVA, id: diva2:1586115
Public defence
2021-11-26, Örebro universitet, Campus USÖ, hörsal C1, Södra Grev Rosengatan 32, Örebro, 09:00 (English)
Opponent
Supervisors
Available from: 2021-08-19 Created: 2021-08-19 Last updated: 2021-12-02Bibliographically approved
List of papers
1. Infectious keratitis: isolated microbes and their antibiotic susceptibility pattern during 2004-2014 in Region Örebro County, Sweden
Open this publication in new window or tab >>Infectious keratitis: isolated microbes and their antibiotic susceptibility pattern during 2004-2014 in Region Örebro County, Sweden
2020 (English)In: Acta Ophthalmologica, ISSN 1755-375X, E-ISSN 1755-3768, Vol. 98, no 3, p. 255-260Article in journal (Refereed) Published
Abstract [en]

PURPOSE: To describe predisposing risk factors, causative microorganisms and their antibiotic susceptibility patterns in infectious keratitis during an 11-year period in Region Örebro County, Sweden.

METHODS: This is a descriptive study conducted as a retrospective audit of clinical records. Patients who received treatment for infectious keratitis at any of the three ophthalmological departments within Region Örebro County, Sweden, between 2004 and 2014 were included if they fulfilled the predefined criteria for infectious keratitis. Data regarding culture results, antibiotic susceptibility pattern and risk factors for infectious keratitis were obtained from medical records and microbiological reports.

RESULTS: In total, 398 episodes of infectious keratitis in 392 patients were included, and 285 were culture positive. The most common predisposing risk factor was contact lens wear (45%). Coagulase-negative staphylococci (39.6%) was the most commonly isolated type of organism. Staphylococcus aureus (15.1%) followed by Moraxella spp. (7.4%) and Pseudomonas aeruginosa (6.7%) were among the most common isolated bacteria not considered to be commensal. Reduced susceptibility to fluoroquinolones was observed in five of 43 S. aureus isolates and in four of nine Streptococcus pneumoniae isolates.

CONCLUSION: The most common predisposing risk factor for keratitis was contact lens wear. Among the most common microbes, not considered to be exclusively commensals, isolated from the cornea in microbial keratitis were S. aureus, Moraxella spp. and P. aeruginosa. The antibiotic susceptibility patterns showed low proportion of resistance. Empiric treatment of suspected infectious keratitis with topical fluoroquinolones and chloramphenicol might be considered in a setting like ours pending culture results.

Place, publisher, year, edition, pages
Wiley-Blackwell, 2020
Keywords
Antibiotic susceptibility, keratitis, microbes
National Category
Infectious Medicine
Identifiers
urn:nbn:se:oru:diva-77026 (URN)10.1111/aos.14256 (DOI)000528770500006 ()31580009 (PubMedID)2-s2.0-85073958683 (Scopus ID)
Note

Funding Agency:

Örebro County Council research committee 

Available from: 2019-10-07 Created: 2019-10-07 Last updated: 2021-11-01Bibliographically approved
2. Does the sampling instrument influence corneal culture outcome in patients with infectious keratitis? A retrospective study comparing cotton tipped applicator with knife blade
Open this publication in new window or tab >>Does the sampling instrument influence corneal culture outcome in patients with infectious keratitis? A retrospective study comparing cotton tipped applicator with knife blade
2020 (English)In: BMJ Open Ophthalmology, E-ISSN 2397-3269, Vol. 5, no 1, article id e000363Article in journal (Refereed) Published
Abstract [en]

Objective: This study aimed to compare the efficacy of a cotton tipped applicator and a knife blade in obtaining corneal samples in patients with infectious keratitis.

Methods and analysis: This is a retrospective cohort study of patients with suspected infectious keratitis during 2004-2014. Samples for corneal culture were obtained by a cotton tipped applicator and a knife blade, and directly inoculated on GC agar, blood agar and Sabouraud agar.

Results: In all, 355 patients were included. Corneal sampling by cotton tipped applicator yielded a significantly higher rate of patients with positive corneal culture, 156/355 (43.9%), compared with knife blade, 111/355 (31.3%) (p<0.001). On a patient level, the culture results obtained by the cotton tipped applicator and the knife blade were identical in 269/355 (76%) of the patients. The overall agreement between the two instruments on microbial level was 0.66 (Cohen's kappa 95% CI 0.60 to 0.72).

Conclusion: Corneal sampling by cotton tipped applicator generated a higher rate of positive corneal cultures and a higher proportion of isolated microbes than by knife blade. Future studies with randomised sampling order are needed to establish which instrument, cotton tipped applicator or knife blade, is the most effective in sampling microbes for direct inoculation in patients with infectious keratitis.

Place, publisher, year, edition, pages
BMJ Publishing Group Ltd, 2020
Keywords
infection, microbiology, cornea
National Category
Ophthalmology
Identifiers
urn:nbn:se:oru:diva-80755 (URN)10.1136/bmjophth-2019-000363 (DOI)000573870600001 ()32154370 (PubMedID)2-s2.0-85079114318 (Scopus ID)
Note

Funding Agency:

Region Örebro County Council research committee

Available from: 2020-03-20 Created: 2020-03-20 Last updated: 2021-11-01Bibliographically approved
3. Clinical and genomic features of Corynebacterium macginleyi-associated infectious keratitis
Open this publication in new window or tab >>Clinical and genomic features of Corynebacterium macginleyi-associated infectious keratitis
Show others...
2021 (English)In: Scientific Reports, E-ISSN 2045-2322, Vol. 11, no 1, article id 6015Article in journal (Refereed) Published
Abstract [en]

Infectious keratitis is a potentially sight threatening ophthalmological emergency. Contact lens wear is a common risk factor. Diagnostic advances such as MALDI-TOF MS provides new insights into the spectrum of corneal pathogens and on microbes previously considered as commensals. Corynebacterium macginleyi was described in 1995, and in 2018, the genomic features of three isolates were reported after whole-genome sequencing. Here we describe the clinical characteristics of patients with infectious keratitis (n = 29) presumably caused by Corynebacterium macginleyi, and analyze the genomic features of C. macginleyi (n = 22) isolated from the corneal ulcers of these patients. The disease course was uneventful apart from minor interventions such as corneal cross-linking and amniotic membrane transplant. Genome sequencing and comparison revealed a highly conserved core genome of C. macginleyi. Based on the analyses of single nucleotide polymorphisms, the population could be divided into two main clades that also differed in a few clade-specific genomic islands. Patients infected with an isolate belonging to the minor clade (n = 7) presented a more severe disease. Comparisons with other corynebacterial species clearly separated C. macginleyi. C. macginleyi may be considered a corneal pathogen; genomic analysis provided insights into its population structure and disease-causing potential.

Place, publisher, year, edition, pages
Nature Publishing Group, 2021
National Category
Infectious Medicine
Identifiers
urn:nbn:se:oru:diva-90519 (URN)10.1038/s41598-021-85336-w (DOI)000630512600017 ()33727638 (PubMedID)2-s2.0-85102715369 (Scopus ID)
Note

Funding Agency:

Örebro University 

Available from: 2021-03-18 Created: 2021-03-18 Last updated: 2022-09-15Bibliographically approved
4. Corneal Culture in Infectious Keratitis: Effect of the Inoculation Method and Media on the Corneal Culture Outcome
Open this publication in new window or tab >>Corneal Culture in Infectious Keratitis: Effect of the Inoculation Method and Media on the Corneal Culture Outcome
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2021 (English)In: Journal of Clinical Medicine, E-ISSN 2077-0383, Vol. 10, no 9, article id 1810Article in journal (Refereed) Published
Abstract [en]

BACKGROUND: To compare two different methods of corneal culture in infectious keratitis: multiple sampling for direct inoculation and enrichment (standard method) and a single sample via transport medium for indirect inoculation (indirect inoculation method).

METHODS: Prospective inclusion of patients fulfilling predefined criteria of infectious keratitis undergoing corneal culture according to both studied methods in a randomized order.

RESULTS: = 0.002) and a significantly higher proportion of microorganisms than the indirect inoculation method, with a Cohen's kappa of 0.38 (95% CI: 0.28-0.49) for agreement between the methods. Subanalysis of culture results showed that direct inoculation on gonococcal agar only combined with the indirect inoculation method resulted in a similar rate of culture positive patients and proportion of detected microorganisms to the standard method.

CONCLUSION: Indirect inoculation of one corneal sample cannot replace direct inoculation of multiple corneal samples without loss of information. A combination of directly and indirectly inoculated samples can reduce the number of corneal samples by four without statistically significant differences in culture outcome or in the proportion of detected microorganisms.

Place, publisher, year, edition, pages
MDPI, 2021
Keywords
Corneal culture, direct inoculation, indirect inoculation, infectious keratitis
National Category
Analytical Chemistry
Identifiers
urn:nbn:se:oru:diva-91681 (URN)10.3390/jcm10091810 (DOI)000650400300001 ()33919274 (PubMedID)2-s2.0-85113191755 (Scopus ID)
Note

Funding Agency:

Region Örebro County Council Research Committee OLL-779911

Available from: 2021-05-10 Created: 2021-05-10 Last updated: 2021-12-02Bibliographically approved
5. Bacterial findings by a targeted sequencing approach in patients with infectious keratitis
Open this publication in new window or tab >>Bacterial findings by a targeted sequencing approach in patients with infectious keratitis
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Surgery
Identifiers
urn:nbn:se:oru:diva-95292 (URN)
Available from: 2021-11-01 Created: 2021-11-01 Last updated: 2021-12-02Bibliographically approved

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Sagerfors, Susanna

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