J Med Cases

Journal of Medical Cases, ISSN 1923-4155 print, 1923-4163 online, Open Access

Article copyright, the authors; Journal compilation copyright, J Med Cases and Elmer Press Inc

Journal website https://jmc.elmerpub.com

Case Report

Volume 16, Number 7, July 2025, pages 239-247

Investigation and Management of a Small Outbreak of Septic Knee Arthritis Following Knee Arthroscopy by Stenotrophomonas maltophilia

↓ Figure 1. The joint fluid of two infected patients through knee arthrocentesis. (a) Case 1. (b): Case 2.

↓ Figure 2. Arthroscopic presentation of knee septic arthritis of Stenotrophomonas maltophilia. (a) Infrapatellar fat pad and medial part of intercondylar notch. (b) Suprapatellar bursa. (c) Lateral compartment. (d) Medial compartment. ACL: anterior cruciate ligament; LFC: lateral femoral condyle; LM: lateral meniscus; MFC: medial femoral condyle; MM: medial meniscus.

↓ Figure 3. The appearance of the contaminated arthroscope. (a) Gross look. (b) Object glasses: white arrowhead indicates slight deformation at the junction of glasses and scope body; black arrowhead indicates slight deformation and an enlarged gap at the junction. (c) Port for light cable. (d) Camera glasses.

↓ **Table 1.** Infection Control Investigation of Instruments Associated With Arthroscopy
Instrument type	Items	Sterilization	Samples per item	Sample positions	Positive samples	Positive positions
One to four samples per item were collected depending on instrument size, shape, and complexity. Initial test results were presented in the table. Two subsequent rounds of testing were performed, showing negative results. ACL: anterior cruciate ligament; HPGP: hydrogen peroxide gas plasma.
Arthroscope	4	HPGP	3	Surface, object glasses, light cable port	1	Object glasses
Shaver handpiece	3	HPGP	4	Body surface, body cavity, cable surface, plug	0	N/A
Light cable	3	HPGP	3	Cable surface, arthroscope port, light source port	0	N/A
Arthroscope cannula	4	Steam autoclave	2	Surface, cavity	0	N/A
Cannula obturator	4	Steam autoclave	1	Surface	0	N/A
Probe	3	Steam autoclave	1	Surface	0	N/A
Basket forceps	12	Steam autoclave	1	Surface	0	N/A
Grasping forceps	6	Steam autoclave	1	Surface	0	N/A
Microfracture pick	6	Steam autoclave	1	Surface	0	N/A
Arthroscopic curette	3	Steam autoclave	1	Surface	0	N/A
Suture hook	6	Steam autoclave	1	Surface	0	N/A
Suture cutter	3	Steam autoclave	1	Surface	0	N/A
Knot pusher	3	Steam autoclave	1	Surface	0	N/A
ACL femoral aimer	2	Steam autoclave	1	Surface	0	N/A
ACL tibial guide	2	Steam autoclave	1	Surface	0	N/A
ACL reamer	12	Steam autoclave	1	Surface	0	N/A
Tendon harvester	2	Steam autoclave	1	Surface	0	N/A
Graft sizer	10	Steam autoclave	1	Surface	0	N/A
Ruler	6	Steam autoclave	1	Surface	0	N/A
General surgical instruments (e.g., scalpel handle, scissor, forceps)	56	Steam autoclave	1	Surface	0	N/A

↓ Table 1. Infection Control Investigation of Instruments Associated With Arthroscopy

Instrument type

Items

Sterilization

Samples per item

Sample positions

Positive samples

Positive positions

One to four samples per item were collected depending on instrument size, shape, and complexity. Initial test results were presented in the table. Two subsequent rounds of testing were performed, showing negative results. ACL: anterior cruciate ligament; HPGP: hydrogen peroxide gas plasma.

Arthroscope

HPGP

Surface, object glasses, light cable port

Object glasses

Shaver handpiece

HPGP

Body surface, body cavity, cable surface, plug

N/A

Light cable

HPGP

Cable surface, arthroscope port, light source port

N/A

Arthroscope cannula

Steam autoclave

Surface, cavity

N/A

Cannula obturator

Steam autoclave

Surface

N/A

Probe

Steam autoclave

Surface

N/A

Basket forceps

Steam autoclave

Surface

N/A

Grasping forceps

Steam autoclave

Surface

N/A

Microfracture pick

Steam autoclave

Surface

N/A

Arthroscopic curette

Steam autoclave

Surface

N/A

Suture hook

Steam autoclave

Surface

N/A

Suture cutter

Steam autoclave

Surface

N/A

Knot pusher

Steam autoclave

Surface

N/A

ACL femoral aimer

Steam autoclave

Surface

N/A

ACL tibial guide

Steam autoclave

Surface

N/A

ACL reamer

Steam autoclave

Surface

N/A

Tendon harvester

Steam autoclave

Surface

N/A

Graft sizer

Steam autoclave

Surface

N/A

Ruler

Steam autoclave

Surface

N/A

General surgical instruments (e.g., scalpel handle, scissor, forceps)

Steam autoclave

Surface

N/A

↓ **Table 2.** Retrospective Survey of Usage of the Contaminated Arthroscope Since “Patient Zero”
Operation type	Patients	Infected patients (positive microbiology)	Infected patients (negative microbiology)	Infection ratio
ACLR: anterior cruciate ligament reconstruction.
Partial meniscectomy	4	1	2	75%
Meniscus repair	3	2	0	66.7%
ACLR	8	1	0	12.5%
Synovectomy	2	0	1	50.0%
Elbow release	1	0	0	0.0%
Iliotibial band release	1	0	0	0.0%
Total	19	4	3	36.8%

↓ Table 2. Retrospective Survey of Usage of the Contaminated Arthroscope Since “Patient Zero”

Operation type

Patients

Infected patients (positive microbiology)

Infected patients (negative microbiology)

Infection ratio

ACLR: anterior cruciate ligament reconstruction.

Partial meniscectomy

75%

Meniscus repair

66.7%

ACLR

12.5%

Synovectomy

50.0%

Elbow release

0.0%

Iliotibial band release

0.0%

Total

36.8%

↓ **Table 3.** Summary of the Antibiotic Protocols for Cases 1-4
Operation date	Case 1	Case 2	Case 3	Case 4
The date of case 1’s postoperative outpatient revisit when septic knee arthritis was suspected, was defined as day 0. *Day -17 indicates 17 days before day 0. SMZ-TMP: sulfamethoxazole-trimethoprim.
Protocol	Cefepime-sulbactam (3.0 g/8 h)	Ceftriaxone (2 g/24 h) SMZ-TMP (0.96 g/12 h)	Ceftriaxone (2.0 g/24 h)	Levofloxacin (0.75 g/d) SMZ-TMP (1.44 g/8 h)
Start date	Day 1	Day 9	Day 6	Day 12
End date	Day 6	Day 10	Day 8	Day 22
Protocol	Levofloxacin (0.5 g/day) SMZ-TMP (0.96 g/8 h)	Levofloxacin (0.75 g/day) SMZ-TMP (1.44 g/8 h)	Levofloxacin (0.75 g/day) SMZ-TMP (1.44 g/8 h)	SMZ-TMP (1.44 g/8 h) Minocycline (100 mg/12 h)
Start date	Day 7	Day 11	Day 9	Day 23
End date	Day 11	Day 17	Day 22	Day 50
Protocol	Levofloxacin (0.75 g/day) SMZ-TMP (1.44 g/8 h) Minocycline (100 mg/12 h)	SMZ-TMP (1.44 g/8 h) Minocycline (100 mg/12 h)	SMZ-TMP (1.44 g/8 h) Minocycline (100 mg/12 h)
Start date	Day 12	Day 18	Day 23
End date	Day 67	Day 46	Day 50

↓ Table 3. Summary of the Antibiotic Protocols for Cases 1-4

Operation date

Case 1

Case 2

Case 3

Case 4

Day -17*

Day 4

Day 2

Day 5

The date of case 1’s postoperative outpatient revisit when septic knee arthritis was suspected, was defined as day 0. *Day -17 indicates 17 days before day 0. SMZ-TMP: sulfamethoxazole-trimethoprim.

Protocol

Cefepime-sulbactam (3.0 g/8 h)

Ceftriaxone (2 g/24 h)
SMZ-TMP (0.96 g/12 h)

Ceftriaxone (2.0 g/24 h)

Levofloxacin (0.75 g/d)
SMZ-TMP (1.44 g/8 h)

Start date

Day 1

Day 9

Day 6

Day 12

End date

Day 6

Day 10

Day 8

Day 22

Protocol

Levofloxacin (0.5 g/day)
SMZ-TMP (0.96 g/8 h)

Levofloxacin (0.75 g/day)
SMZ-TMP (1.44 g/8 h)

SMZ-TMP (1.44 g/8 h)
Minocycline (100 mg/12 h)

Start date

Day 7

Day 11

Day 9

Day 23

End date

Day 11

Day 17

Day 22

Day 50

Protocol

Levofloxacin (0.75 g/day)
SMZ-TMP (1.44 g/8 h)
Minocycline (100 mg/12 h)

SMZ-TMP (1.44 g/8 h)
Minocycline (100 mg/12 h)

Start date

Day 12

Day 18

Day 23

End date

Day 67

Day 46

Day 50