Surveillance of Methicillin-Resistant Staphylococcus From the Ocular Surface of Cataract Surgery Patients

1
Surveillance of Methicillin-Resistant
Staphylococcus From the Ocular Surface of
Cataract Surgery Patients

• Eric Donnenfeld, MD1 Randall Olson, MD2 Kerry
  Solomon, MD3 R. Bruce Wallace, MD4 Taryn
  Conway, BS5 Rhett Schiffman, MD5 David
  Hollander, MD5
• 1Ophthalmic Consultants of Long Island and
  Connecticut, Rockville Centre, NY 2The John A.
  Moran Eye Center, University of Utah, Salt Lake
  City, UT 3Ophthalmology, Medical University of
  South Carolina, Charleston, SC 4Wallace Eye
  Surgery, Laser and Surgery Center, Alexandria,
  LA 5Allergan, Inc., Irvine, CA

Financial Disclosures This study was funded by
Allergan, Inc., Irvine, CA. Drs. E. Donnenfeld,
R. Olson, K. Solomon, and R.B. Wallace are
consultants to Allergan, Inc. Ms. T. Conway and
Drs. R. Schiffman and D. Hollander are employees
of Allergan, Inc.
2
INTRODUCTION

• Endophthalmitis is a rare, yet potentially
  devastating complication following cataract
  extraction.1-4
• The ocular surface (lids and conjunctiva) and
  nasal flora are the predominant source of
  bacteria leading to postoperative
  endophthalmitis.5-7
• The Endophthalmitis Vitrectomy Study (EVS)
  demonstrated that the vast majority of cases of
  postcataract endophthalmitis arise secondary to
  Gram-positive organisms, including Staphylococcus
  epidermidis and S aureus.8
• Methicillin-resistant staphylococcal infections
  are on the rise and no longer confined to
  healthcare workers.4,9-12
• This study was designed to determine the bacteria
  present on the ocular surface (lids and
  conjunctiva) in patients undergoing cataract
  surgery. An additional goal of the study was to
  evaluate the presence of oxacillin
  (methicillin)resistant bacterial species on the
  ocular surface of both healthcare and
  non-healthcare workers.

3
METHODS

• A multicenter (10 sites), prospective study.
• Swabs were performed on the superior lid lash
  margin and inferior tarsal conjunctiva of the
  nonsurgical eye of patients undergoing cataract
  surgery at the time of operation.
• Gram-negative bacteria were speciated by the BBL
  Enterotube II.
• Gram-positive bacteria were tested for the
  presence of catalase to separate Staphylococcus
  species from other Gram-positive bacteria.
• Staphylococcal species were identified using the
  API Staph kit (bioMérieux , Inc. Durham, NC).
• Susceptibility to oxacillin was tested by Etest
  (oxacillin OX, AB Biodisk Solna, Sweden) in
  Staphylococcus species.
• The oxacillin breakpoints were 2 µg/mL
  (sensitive) and 4 µg/mL (resistant) for S
  aureus and S lugdunensis and 0.25 µg/mL
  (sensitive) and 0.5 µg/mL (resistant) for all
  other coagulase-negative staphylococci.

4
Baseline Patient Demographics
All Patients (N 399)
Gender Female, n () 224 (56)
Age, years Mean (SD) 70 (10)
Comorbidities, n () Glaucoma Diabetes 35 (9) 83 (21)
Healthcare exposure in the last 3 years, n () Healthcare worker Immediate family member of a healthcare worker 38 (10)83 (21)
Patients with positive cultures, n () Lid Conjunctiva 321 (80) 229 (57)

• Some patients had cultures positive for 2 or 3
  pathogens. The total number of positive lid and
  conjunctival isolates were 393 and 256,
  respectively.

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Bacterial Species on the Ocular Surface of
Cataract Surgery Patients
Lid
Conjunctiva
S aureus n 31 (12)
S aureus n 60 (15)
Micrococcus species
Micrococcus species
S capitis
n 13 (5)
n 18 (5)
n 7 (3)
S xylosus
S warneri
n 12 (3)
n 6 (2)
S lugdunensis
n 9 (2)
S warneri
n 6 (2)
n 9 (2)
S epidermidis n 243 (62)
S lugdunensis
Other Gram-positive bacteria
n 12 (5)
n 7 (2)
S capitis
n 21 (5)
S epidermidis n 165 (64)
n 9 (4)
Other Gram-positivebacteria
n 14 (4)
Enterobacter agglomerans
n 7 (3)
Gram-negative bacteria
Other Gram-negative bacteria
(N 393)
(N 256)

• The majority of positive lid (303/393 77) and
  conjunctival (196/256 76) isolates were either
  S epidermidis or S aureus.

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Oxacillin (Methicillin) Susceptibility of Lid
Staphylococcus Species
48
Oxacillin Resistant
S epidermidis (n 224)a
51
34
Oxacillin Susceptible
S aureus (n 59)a
59
58
S xylosus (n 12)
42
0
S warneri (n 8)a
88
33
S lugdunensis (n 9)
66
17
S capitis (n 6)
83
0
S hominis (n 4)
100
S caprae (n 2)
50
50
S haemolyticus (n 2)
0
S saprophyticus (n 2)a
50
0
S lentus (n 1)
100
0
S sciuri (n 1)
100
100
S cohnii spp urealyticus (n 1)
0
Percentage of Staphylococcus Species
aFour (7) S aureus, 2 (1.0) S epidermidis, 1
(50) S saprophyticus, and 1 (12) S warneri were
intermediately resistant to oxacillin.

• Oxacillin (methicillin) susceptibility was tested
  on 331 (92) of 358 lid staphylococci.
• The rate of oxacillin (methicillin) resistance
  was highest among lid S xylosus (58), followed
  by S epidermidis (48) and S aureus (34).

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Oxacillin (Methicillin) Susceptibility of
Conjunctival Staphylococcus Species
45
S epidermidis (n 154)a
Oxacillin Resistant
52
Oxacillin Susceptible
21
S aureus (n 29)a
76
0
S warneri (n 5)
100
0
S lugdunensis (n 5)
100
25
S capitis (n 4)
75
S caprae (n 3)a
33
0
S hominis (n 3)
100
67
S haemolyticus (n 3)
33
0
S xylosus (n 2)
100
Percentage of Staphylococcus Species
aFour (3) S epidermidis, 1 (3) S aureus, and 1
(33) S caprae were intermediately resistant to
oxacillin.

• Oxacillin (methicillin) susceptibility was
  determined for 208 (92) of 227 conjunctival
  staphylococci.
• The rate of oxacillin (methicillin) resistance
  was 45 among conjunctival S epidermidis and 21
  among S aureus species.

8
Proportion of Oxacillin (Methicillin)Resistant
Staphylococcus Species Among Non-Healthcare
Workers
Non-Healthcare Workers
120
Healthcare Workers
69
Patients (n)
14
7
Resistant Conjunctival Cultures
Resistant Lid Cultures

• Of 134 patients with resistant lid Staphylococcus
  cultures, 120 (90) patients were not healthcare
  workers.
• Of 76 patients with resistant conjunctival
  Staphylococcus cultures, 69 (91) were not
  healthcare workers.

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Distribution of Oxacillin (Methicillin)Resistant
Staphylococcus Isolates
Non-Healthcare Workers Healthcare Workers Total
Positive Isolates, n 485 54 539
All Resistant Isolates, n ()MRSAa MRSEb 200 (41)25 (5)159 (33) 22 (41)1 (2)19 (35) 222 (41)26 (5)178 (33)
Oxacillin MIC, (µg/mL) MRSAa Median Range MRSEb Median Range 25616-256960.5-256 44-41920.5-256 256 4-2561120.5-256
aMRSA Oxacillin (methicillin)-resistant S
aureus bMRSE Oxacillin (methicillin)-resistant
S epidermidis

• The percentage of resistant Staphylococcus
  isolates was similar between healthcare and
  non-healthcare workers.

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DISCUSSION

• Over 75 of bacterial isolates on the ocular
  surface (lids and conjunctiva) of cataract
  surgery patients were either S epidermidis or S
  aureus.
• Overall, approximately one-half of S epidermidis
  isolates and one-quarter of S aureus isolates
  were resistant to oxacillin (methicillin).
• The percentage of Staphylococcus isolates
  resistant to oxacillin (methicillin) was similar
  between healthcare and non-healthcare workers.
• The high rate of oxacillin (methicillin)resistant
  Staphylococcus species on the ocular surface of
  cataract surgery patients underscores the need to
  use an antibiotic in the perioperative period
  with a favorable profile against Gram-positive
  species, including Oxacillin (methicillin)resista
  nt S aureus (MRSA) and Oxacillin
  (methicillin)resistant S epidermidis (MRSE).

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CONCLUSIONS

• S epidermidis and S aureus were the most common
  bacterial species identified on the ocular
  surface of cataract surgery patients.
• A significant portion of ocular surface
  staphylococcal species were resistant to
  oxacillin (methicillin), even among
  non-healthcare workers.

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