Visual outcome in eight cases of Serratia marcescens keratitis

Microbiological Profile and Clinical Characteristics of Bacterial Keratitis with Poor Visual Outcome

Purpose: To compare clinical characteristics between the poor visual outcome (PVO) and good visual outcome (GVO) groups in culture-proven bacterial keratitis.Methods: A total of 230 cases (44 and 186 eyes in the PVO and GVO groups, respectively) of culture-proven bacterial keratitis, treated between January 2007 and December 2020, were reviewed retrospectively. The PVO group included cases with the final best-corrected visual acuity (BCVA) of less than 0.1 and no improvement compared to the initial BCVA. The remaining cases were included in the GVO group. The microbiological profiles, epidemiology, predisposing factors, and clinical characteristics were compared between the PVO and GVO groups, and the risk factors for PVO were analyzed.Results: Staphylococcus spp. and Pseudomonas spp. were common isolates in both the PVO and GVO groups, with no significant differences in the distribution of isolates. There were no significant differences between the groups in terms of sex, seasonal distribution, corneal trauma, and prior topical steroid use, but contact lens wear was significantly less in the PVO group. Significant risk factors for PVO were age ≥60 years (Z = 4.22, two-proportion Z-test), central corneal lesions (Z = 3.80), epithelial defect size ≥5 mm² (Z = 3.74), prior ocular surgery (Z = 3.63), hypopyon (Z = 3.42), previous ocular surface disease (Z = 3.32), and diabetes (Z = 3.12).Conclusions: In patients with bacterial keratitis, PVO was associated with older age, severe initial corneal findings, previous ocular disease history, and diabetes, but not with the causative pathogen itself.

Infectious Crystalline Keratopathy Caused by Serratia marcescens

PURPOSE

To report the case of a 70-year-old woman with Serratia infectious crystalline keratopathy.

METHODS

Case report.

RESULTS

This is a report of a 70-year-old woman with a history of chronic open-angle glaucoma and trachoma with lagophthalmos, entropion, and trichiasis in both eyes who developed crystalline keratopathy after penetrating keratoplasty and cataract extraction in the right eye followed up with treatment with long-term topical steroids. Ten months after the initial penetrating keratoplasty and cataract extraction, the patient had decreased visual acuity, intense pain, and tearing in the right eye. Corneal cultures showed Serratia marcescens. Topical steroids were discontinued, and treatment with tobramycin and vancomycin ophthalmic solution every hour was initiated. Despite 1 week of aggressive therapy, there was an increase in corneal infiltrate, epithelial defects, and melting, which eventually involved the peripheral recipient cornea. Therapeutic penetrating keratoplasty, debridement of the peripheral cornea, and amniotic membrane transplantation were performed. Antibiotic agents were used postoperatively. There has been no evidence of recurrent infection. The best-corrected visual acuity improved to 6/15 at the 6-month follow-up period after the second intervention.

CONCLUSIONS

S. marcescens may cause infectious crystalline keratopathy after penetrating keratoplasty in patients treated with long-term topical steroids. Therapeutic penetrating keratoplasty, surgical debridement, and amniotic membrane transplantation may be necessary when the clinical response to intensive medical treatment is inadequate.

Human corneal epithelial cells respond to ocular-pathogenic, but not to nonpathogenic-flagellin

In this study, we investigated the expression of TLR5 in human corneal epithelial cells (CEC), and the functional outcome of TLR5 triggering by flagellins of pathogenic- and nonpathogenic bacteria. Flagellins derived from Pseudomonas aeruginosa, Salmonella typhimurium, Serratia marcescense or Bacillus subtilis were used. The TLR5 protein and TLR5 specific mRNA expression was evident on human CEC. In human corneal epithelium tissues, TLR5 protein was detected at the basal and wing cells of the tissues. Ocular pathogenic bacteria, namely P. aeruginosa and S. marcescense, derived flagellin induced the significantly increased level of gene activation and IL-6 and IL-8 production. In contrast, ocular nonpathogenic S. typhimurium- and B. subtilis-derived flagellin induced neither the gene activation nor the increased production of IL-6 and IL-8 in human CEC. Human CEC would respond only to flagellin derived of ocular pathogenic bacteria, but not to those derived of ocular nonpathogenic bacteria, to generate pro-inflammatory cytokines.

Serratia Corneal Ulcers

PURPOSE

To study the clinical and microbiological profile of Serratia corneal ulcers at the Cornea Service of the Wills Eye Hospital.

METHODS

This was a retrospective, observational case series. The clinical records of patients with Serratia marcescens corneal ulcers seen at the Cornea Service of the Wills Eye Hospital between January 1, 1998 and December 31, 2002 were reviewed.

RESULTS

Twenty-four cases of Serratia keratitis were identified in 21 patients. Two patients (9.5%) had recurrent keratitis, 1 of which recurred twice. Both had corneal graft edema and were on topical steroids and antiglaucoma drops. The Serratia infection in 15 patients (71%) was associated with an abnormal corneal surface. Twelve of these patients (57%) had the ulcer in a corneal graft, 4 (19%) of which were associated with suture infiltrates. Fifteen patients (71%) were on topical medications-15 used corticosteroids and 13 used antiglaucoma drops. Six patients (29%) were contact lens wearers-1 had a concomitant suture infiltrate associated with a corneal graft, and 5 had otherwise healthy corneas. One isolate lacked in vitro susceptibility to ciprofloxacin and ofloxacin but was susceptible to gentamicin and tobramycin. Nineteen patients had a favorable response to medical therapy. Two patients with poor outcome had large corneal ulcers with severe necrosis and thinning associated with delay in treatment.

CONCLUSIONS

Serratia marcescens keratitis is associated with the presence of an abnormal corneal surface, use of topical medications, and contact lens wear. Prompt medical therapy results in a good clinical response in the majority of cases.

Ulcerative keratitis caused by Serratia marcescens after laser in situ keratomileusis

We report 2 cases of severe corneal infections caused by Serratia marcescens after laser in situ keratomileusis (LASIK). Twenty-four hours after LASIK, 2 patients developed infectious keratitis, 1 bilaterally. In each eye, the corneal flap was edematous, ulcerated, and detached from the stromal bed. Treatment included removal of the necrotic flap and aggressive antibiotic therapy. Cultures from corneal exudates were positive for S marcescens. After 1 year, both patients had a loss of best corrected visual acuity (BCVA) ranging from 20/40 to 20/22 because of irregular astigmatism. Overrefraction with a hard contact lens resulted in a BCVA of 20/20 in the 3 affected eyes. Slitlamp examination showed trace subepithelial haze without severe corneal scarring. Videokeratography disclosed areas of paracentral inferior steepening resembling keratoconus. Refraction and videokeratography remained stable after 6 months of follow-up. Ulcerative keratitis caused by S marcescens is a potential complication of LASIK. Bilateral involvement may occur if bilateral simultaneous surgery is performed.

Endogenous Serratia marcescens endophthalmitis with dark hypopyon: case report and review

A case of endogenous Serratia marcescens endophthalmitis in a patient with diabetes, end-stage renal disease, and an indwelling venous catheter is reported. The patient presented with a tan hypopyon and elevated intraocular pressure. Diagnosis was established by positive blood, vitreous, conjunctival, and catheter tip cultures. After a deteriorating course the eye was enucleated. Gross and histopathologic examination revealed the presence of a dark hypopyon with iris necrosis and pigment dispersion and possible spontaneous globe perforation. This is the eleventh reported case of endogenous Serratia endophthalmitis. Previous association of a pink hypopyon and of pigmented vitreous fluid and Serratia endophthalmitis has been reported. This is the first case of dark hypopyon in endogenous Serratia marcescens endophthalmitis reported in the medical literature. Previous entities associated with dark hypopyon have been limited to intraocular melanoma and Listeria monocytogenes endophthalmitis. Dark hypopyon in the appropriate clinical setting may be useful in aiding diagnostic and therapeutic decisions.

Incidence of contact-lens-associated microbial keratitis and its related morbidity

BACKGROUND

The incidence of contact-lens-associated microbial keratitis is uncertain and its related morbidity in the general population of contact-lens wearers is not known. We examined these issues in a prospective epidemiological study.

METHODS

We surveyed all practising ophthalmologists in the Netherlands to identify all new cases of microbial keratitis reported during a 3-month period in 1996. Follow-up telephone calls were made to examine ocular morbidity. We undertook annual nationwide telephone surveys between 1994 and 1997 to estimate the prevalence of contact-lens wear.

FINDINGS

Of 440 ophthalmologists contacted, 379 provided information. There were 92 cases of microbial keratitis; 17 used daily-wear rigid gas-permeable lenses, 63 daily-wear soft lenses, and 12 extended-wear soft lenses. The estimated annualised incidence of microbial keratitis was 1.1 per 10,000 (95% CI 0.6-1.7) users of daily-wear rigid gas-permeable lenses, 3.5 per 10,000 (2.7-4.5) users of daily-wear soft lenses, and 20.0 per 10,000 (10.3-35.0) users of extended-wear soft lenses (p<0.00001 for comparison between all groups), Five of the 92 patients achieved a final visual acuity of 20/70 or less. Pseudomonas and Serratia spp were the organisms most commonly isolated. Pseudomonas keratitis accounted for the largest mean diameter of corneal ulcers, the highest mean number of days in hospital, the greatest number of mean outpatients visits, and the poorest visual acuity outcome.

INTERPRETATION

The incidence of microbial keratitis among users of extended-wear soft contact lenses in the Netherlands is similar to that reported in the USA during 1989. Awareness of risk factors and improvement in contact-lens materials have not led to a decrease in incidence. Overnight wear should be strongly discouraged.

The role of Serratia marcescens in soft contact lens associated ocular infections. A review

Serratia marcescens is a Gram negative rod which for a century and a half was considered a harmless saphrophyte. However, medical technology and the use of antibacterial agents have created ecological niches for this bacterium, which is now a medical problem. The bacterium is encountered in connection with contact lens keratitis, often associated with contaminated contact lens solutions. The concentrations of chlorhexidin and thiomersal required in contact lens solution to suppress the bacterium have been proved toxic to the eye. Modern contact lens solutions with biguanids have rapid killing kinetics, while in solutions with polyquaternium S. marcescens can survive in reduced numbers for up to 72 hours. The adherence of a specific isolate of Serratia to hydrogel lenses increased with decreased water content of the lenses. However, there has been no correlation between hydrophobicity markers or hemagglutinins and adherence to contact lenses or urinary tract epithelium. When handling medical plastic devices, such as contact lenses, strictly enforced hygiene remains the most important method to combat environmental bacteria such as Serratia marcescens.

Epidemiology of Pseudomonas aeruginosa keratitis in contact lens wearers

This study evaluated the epidemiology of Pseudomonas aeruginosa keratitis in contact lens (CL) wearers; the relationships between CL storage case contamination and CL hygiene practice and between CL hygiene and the development of keratitis. Sixteen CL wearers with keratitis were compared with 44 asymptomatic controls. Lens hygiene practice was assessed and CL care materials, domestic water sites and endogenous sites were evaluated microbiologically. Poor CL hygiene was not associated with Ps. aeruginosa keratitis. There was an association between keratitis and bacterial contamination of the CL and storage case (P < 0.0005). Lens and storage case contamination were not significantly associated with poor hygiene. No domestic or endogenous source for Ps. aeruginosa was found. Causative organisms may be derived from other sources, but CLs and CL storage cases provide a favourable environment for Ps. aeruginosa colonization. Changing the CL care environment to one less favourable for Ps. aeruginosa may help to eliminate this problem.

Hemagglutination (fimbriae) and hydrophobicity in adherence of Serratia marcescens to urinary tract epithelium and contact lenses

The capacity of 59 isolates of Serratia marcescens, obtained from urinary tract infections, wounds, and contact lenses or their paraphernalia, to agglutinate erythrocytes from different animal species was tested. Three main patterns were found: mannose-sensitive agglutination of guinea-pig, fowl or horse erythrocyte; mannose-resistant agglutination of chicken or pigeon erythrocytes alone or in combination with mannose-sensitive agglutination; and no agglutination. Hemagglutination capacity was associated with isolates from urinary tract infection, but not with isolates associated with contact lenses. Adherence to human urinary tract epithelium did not correlate with the hemagglutination patterns nor with the origin of the isolates. Some strains of different hemagglutination pattern were selected for the study of hydrophobicity and adherence to contact lens polymers. Hydrophobicity, as determined by degree of partition in hexadecane and water (BATH-values), correlated neither with degree of adherence to contact lens polymers nor with the hemagglutination pattern. For a representative strain there was an excellent correlation (r2 = 0.98) between adherence and the water content (hydrophobicity) of the lens polymers. These results suggest that, as with tissues, other factors interact with hydrophobicity in causing adherence to plastics.

Inhibitory effects of ovomacroglobulin on bacterial keratitis in rabbits

We studied the inhibitory effects of chicken egg-white ovomacroglobulin (ovoM) on keratitis induced by 56,000-Da protease (56 KP) of Serratia marcescens and by elastase (PE) and alkaline protease (PAP) of Pseudomonas aeruginosa. The effects of ovoM on the serratial and pseudomonal keratitis in rabbits were also elucidated. In one model, four drops of 56 KP, PE, or PAP (1 mg/ml) were applied to wounded corneas of eight eyes. Thereafter, 80 microliters ovoM (10 mg/ml) was dropped into four eyes and 0.01 M phosphate-buffed 0.15 M saline (pH 7.4) into the other eyes as a control. The other in vivo test system involved intrastromal injection of S. marcescens or P. aeruginosa, by which each sample (10(5)-10(7) colony-forming units) mixed with ovoM was injected into one cornea and the other cornea received organisms without ovoM. OvoM completely inhibited the activity of these bacterial proteases in vitro and reduced corneal destruction in experimental keratitis in rabbits. In addition, greatly accelerated wound healing was observed.

Contamination of contact lens storage cases by Acanthamoeba and bacteria

In order to identify possible risk factors for microbial keratitis the storage cases for contact lenses of 102 asymptomatic lens wearers were tested for contamination by bacteria and free-living amoebae. Of this group 43 had significant counts of viable bacteria and only 40 had negligible counts. Seven had contamination by acanthamoebae, of whom six also had significant bacterial counts. These results were categorised according to the type of contact lens worn and the lens disinfection method. The high rates of contamination by apathogenic and pathogenic organisms, in particular Acanthamoeba, and the probable support by contaminating bacteria of Acanthamoeba, are discussed.

Late bacterial and fungal keratitis after corneal transplantation. Spectrum of pathogens, graft survival, and visual prognosis

The authors reviewed 108 bacterial and fungal corneal ulcers that developed 1 to 72 months after penetrating keratoplasty in 79 eyes of 78 patients. Graft hypesthesia, topical corticosteroid and antibiotic treatment, exposed sutures, epithelial defects, and poor visual acuity commonly predated infectious keratitis. There were 69 bacterial, 34 fungal, and 5 combined infections. Candida albicans and Staphylococcus epidermidis were the most common pathogens. Follow-up after infection averaged 23 months (range, 1-80 months). Despite hospitalization and fortified topical antibiotic treatment, complications such as wound dehiscence and corneal perforation necessitated emergency regraft in 38 (35%) cases. Of 73 previously clear grafts, only 29 (40%) retained clarity. Median visual acuity, 20/200 before infection, fell to counting fingers at last follow-up; 12 eyes lost light perception.

Association of Pseudomonas and Serratia corneal ulcers with use of contaminated solutions

The wetting and soaking solutions and contact lens cases of eye clinic patients commonly were contaminated with gram-negative bacteria during their use. Serratia marcescens occurred most frequently in preserved solutions, whereas Pseudomonas aeruginosa was most often recovered from home-prepared saline. The bacteria were recovered at densities of greater than 10(6) cells per ml and typically persisted in the solutions. Eight patients who developed bacterial keratitis during 1986 used solutions contaminated with the etiological agents of the infections. Improper hygienic practices of the patients and failure of some preservative systems were implicated in the development of the infections.

Persistence of Serratia marcescens, Serratia liquefaciens and E. coli in solutions for contact lenses

Twenty-four different brands of contact lens solutions were experimentally inoculated with strains of S. marcescens, S. liquefaciens and E. coli. Only flexol and hexidin could sufficiently suppress the growth of Serratia strains. If a soaking agent is to be effective in suppressing S. marcescens it must have a chlorhexidine concentration of at least 50 micrograms/ml and a thiomersal concentration of 10 micrograms/ml.

Serratia marcescens infections

The recognition of serratia as an opportunistic human pathogen can be dated from 1959, when the microorganism entered the family ofEnterobacteriaceae,with features recognizable in the clinical laboratory and related to theKlebsiella/Enterobactergroup. Since then, physicians have been challenged to establish the significance of isolation of serratia from a clinical specimen.

The serratial 56K protease as a major pathogenic factor in serratial keratitis. Clinical and experimental study

A possible cause and the difference in clinical severity of serratial keratitis were investigated. Two strains of Serratia marcescens were isolated: one from a patient with severe liquefactive keratitis, who had diabetes mellitus, and one from a patient with mild superficial keratitis, but who had no underlying disease. When the same numbers of bacteria were injected separately into corneas of the same rabbits or guinea pigs, the strain from the first patient elicited severe corneal destruction, remarkable intracorneal edema; and liquefactive necrosis, but the strain from the second caused mild keratitis with erosion or intracorneal abscess. The keratitis induced by the former strain required a longer time to heal, and the prognosis was poorer than that for the other keratitis. Therefore, the difference in severity between the two cases of experimentally induced keratitis paralleled that of the clinical cases. Thus, the severity of the serratial keratitis might be attributed more to the virulence of the bacteria than the condition of the host. The virulence factor seemed to be a heat-labile metabolic product (or products) of the bacteria. To clarify this virulence factor, the major secretory protease (56K protease) produced by these two strains of bacteria was compared by using in vitro and in vivo systems. The virulent strain produced about ten times more protease during culture than the less virulent strain. When injected into the corneas of experimental animals, the 56K protease from the virulent strain induced severe lesions similar to those caused by the living virulent strain of bacteria. These results indicated that one of the major factors causing the virulence was correlated with the tissue destructive 56K protease produced by S. marcescens.

A serratial protease causes vascular permeability reaction by activation of the Hageman factor-dependent pathway in guinea pigs

The 56-kilodalton (56K) protease isolated from a culture filtrate of Serratia marcescens caused vascular permeability enhancement followed by edema formation when injected into guinea pig peripheral corneas and subconjunctival space or skin. The character and the mechanism of permeability enhancement were analyzed in vivo. The enhancement was maximum at 5 to 10 min. The permeability reaction increased exponentially by the amount of enzyme used. The enhancement of permeability induced by the 56K protease was not affected by treatment with an antihistamine but was greatly augmented by simultaneous injection of a kinin potentiator, Glu-Trp-Pro-Arg-Pro-Gln-Ile-Pro-Pro-OH (SQ 20,881). Furthermore, the permeability activity of the protease, but not the amidolytic activity, was inhibited by soybean trypsin inhibitor, a well-known inhibitor of plasma kallikrein, as well as by corn trypsin inhibitor, the best inhibitor of activated Hageman factor. Results of these in vivo studies indicate that the permeability-enhancing reaction induced by the 56K protease is caused by activation of the Hageman factor-dependent pathway in the tissue. The permeability-increasing activity of the 56K protease was parallel with the enzyme activity. Serratial lipopolysaccharide did not produce a permeability enhancement reaction within 30 min when injected into guinea pig skin. These results are consistent with the results of recent in vitro experiments in which activation of the purified Hageman factor but not of prekallikrein by the 56K protease was elucidated (Matsumoto et al., J. Biochem. (Tokyo) 96:739-749, 1984). Thus, the molecular mechanism described above appears to be operative in the pathogenesis of corneal edema and chemosis, which is induced by S. marcescens, in addition to the direct tissue destruction by the protease.

Haemophilus influenzae corneal ulcer in a therapeutic contact lens wearer

Haemophilus influenzae is an unusual corneal pathogen and an unusual cause of corneal ulcers in Western society. In previous reports corneal complications from H. influenzae have been secondary to a conjunctivitis. The first case of a primary H. influenzae corneal ulcer as a complication of therapeutic contact lens wear is presented. Since other uncommon bacteria have been reported as causes of contact lens related corneal ulcers, the bacteriology of contact lens related corneal ulcers is reviewed. Ophthalmologists need to be aware that H. influenzae infections in adults are becoming more frequent.

Serratia keratitis transmitted by contaminated eyedroppers

Serratia marcescens keratitis developed in three patients after keratoplasty. Two patients were using prednisolone sodium phosphate eyedrops and the third was using 0.5% timolol maleate eyedrops. All three cases resolved after treatment with topically and subconjunctivally administered antibiotics. Although S. marcescens was isolated from the outer grooves of the bottletops and from the inner surfaces of the eyedropper caps, it was not cultured from the solutions in the bottles. Moisture collecting in the dead space between the cap and bottle was apparently a culture medium for Serratia. When eyedrops were expressed into the patient's eyes, the eyes were inoculated with Serratia from the contaminated liquid flowing down the eyedropper shaft.