Transcript No Slide Title

Daptomycin Resistance and Vancomycin Intermediate S. aureus in a Patient with Prolonged Antibiotic Therapy.
PAUL MARIANI M.D1 ,PAUL CARSON M.D.1, HELIO SADER, MD, PhD2, RON JONES, MD2;
1.Univeristy of North Dakota, Fargo, ND, 2. JMI Laboratories, North Liberty, IA.
Results
Abstract
Methods
Background: Daptomycin is a lipopeptide with bactericidal activity against Gram-positive
drug-resistant organisms with reports of acquired resistance rare. We document the
development of resistance to daptomycin and decreased susceptibility to vancomycin during
prolonged therapy with these antimicrobials.
Case: A 64 year old man developed a methicillin-resistant S. aureus (MRSA) prosthetic hip
infection with recurrent bacteremia treated with vancomycin (30 mg/kg/d). On hospital day
(HD) # 99 patient underwent prosthesis removal complicated by disseminated intravascular
coagulation, acute renal failure and antibiotic therapy changed to daptomycin (6 mg/kg).
Patient improved with negative repeat blood cultures. On HD #148 patient developed a
T=103.5°F, wound culture revealed MRSA and an MRI showed a 32 cm thigh abscess. Patient
underwent debriédement and bone culture revealed polymicrobial infection with DAPR/VISA treated with dalfopristin-quinupristin (7.5 mg/kg q8h), gatifloxacin, fluconazole.
Patient later expired from E faecalis catheter-related sepsis.
Methods: S. aureus was isolated on HD #1 (strain # 1), HD #99 (#2) and HD 148 (#3) from
blood, surgical wound, and bone, respectively. Strains were tested for S against DAP, VAN
and other antimicrobials by CLSI broth microdilution, disk diffusion and Etest. Heteroresistance to vancomycin (hVISA) was evaluated by inoculating 2 MacFarland suspension
onto BHI agar with VAN Etest strips and incubating for 48 hours. The strains were typed by
automated ribotyping and pulse field gel electrophoresis.
Results:
All strains were R to oxacillin, clindamycin and ciprofloxacin; and S to gentamicin, linezolid,
tetracycline, and tigecycline. Strains #1 and #2 showed MIC of 0.5, 1 and 0.06 μg/ml for
DAP, VAN, and dalbavancin (DBV), respectively, while strain #3 showed MIC of 8 μg/ml for
DAP, 4 μg/ml for vancomycin as a hVISA, 0.25 μg/ml for DBV. All 3 strains showed identical
molecular typing pattern.
Conclusion:
Resistance to daptomycin may develop during prolonged treatment of S. aureus infections
with DAP.
Isolates: Three strains of S. aureus were isolated from a patient including a blood culture on
hospitalization day (HD) #1, a surgical wound culture from HD #99 and a bone culture from
HD #148. All strains were processed locally and subsequently forwarded to JMI Laboratories
(North Liberty, Iowa, USA) for confirmatory susceptibility testing and molecular typing.
Susceptibility testing: The strains were tested by Clinical and Laboratory Standards Institute
(CLSI; formerly NCCLS) M7-A6 broth microdilution methods in validated, dry-form panels
manufactured by TREK Diagnostics, Inc. (Cleveland, Ohio, USA). Daptomycin were tested in
Mueller-Hinton broth supplemented to 50 mg/L as recommended by the manufacturer.
Disk diffusion methods were performed according to NCCLS M2-A8 method and by Etest (AB
BIODISK, Solna, Sweden) generated according to the manufacturer’s guidelines found in the
package insert.
Molecular typing: Isolates were typed for genetic relatedness using automated ribotyping
(RiboprinterTM Microbial Characterization System, Qualicon, Wilmington, Delaware, USA) of
genomic DNA after digestion using EcoR1 enzyme to assign a ribogroup. Isolates were also
typed by pulsed-field gel electrophoresis (PFGE, BioRad Laboratories, Hercules, California,
USA) after DNA digestion with SmaI. Gels were stained with ethidium bromide to visually
identify banding patterns and determine clonal relatedness.
Case
A 64 year old man was admitted the intensive case unit with methicillin-resistant
Staphylococcus aureus (MRSA) sepsis and was treated with 17-day course of vancomycin.
On the 22nd hospital day patient became febrile and repeat blood cultures reveald MRSA,
a 2D-echocardiogram did not reveal evidence of endocarditis and was treated with a one
month course of vancomycin. On the 60th hospital a WBC tagged scan showed infection
of the right prosthetic hip where an aspiration revealed a WBC 47,000 with culture
positive for MRSA. Patient had suffered a myocardial infarction and an episode of acute
cholecystitis thus surgery was postponed until 102nd hospital day yet continued to receive
vancomycin as suppressive therapy.
Intraoperatively patient developed disseminated intravascular coagulation necessitating
aggressive measures for correction of coagulopathy and further complicated by nonoliguric acute renal failure and thrombocytopenia with platelet count 27,000 and
daptomycin 650 mg daily was begun. Patient’s acute medical problems stabilized over the
ensuing 4 weeks. On 150th hospital day patient suddenly developed a fever where repeat
bacterial blood cultures were negative, however, a wound culture revealed MRSA and an
MRI demonstrated a 32cm abscess.
Patient was again taken to surgery and an acetabular biopsy grew vancomycin
intermediate, daptomycin intermediate S aureus, C freundii, and fluconazole susceptible C
albicans, C glabrata, C parapsilosis. Patient’s antibiotic therapy was changed to
dalfopristin / quinupristins 850 mg / day, gatifloxacin 200 mg / day and fluconazole 400
mg / day. Patient subsequently developed a line-associated dalfopristin/quinupristin
resistant E faecalis bacteremia in addition to polymycrobial wound infection. Family opted
to withdraw all medical care and patient died shortly thereafter.
Table 1. Broth microdilution MIC results for 19 antimicrobial agents tested against three S.
aureus isolates recovered from a patient on prolonged therapy.
•According to broth microdilution MIC results, all three ORSA strains were resistant to
oxacillin, erythromycin, clindamycin, telithromycin and ciprofloxacin, and susceptible to a
larger number of antimicrobials (Table 1).
Antibiogram analysis of the three S. aureus isolates showed that strains #1 and #2 were
more similar with identical daptomycin (0.5 g/ml), vancomycin (1 g/ml) and dalbavancin
(0.06 g/ml) MIC results. Strain #3 MIC results for these agents were elevated to 8, 4 and
0.25 g/ml, respectively.
Interestingly, strains #1 and #2 were resistant to penicillin (-lactamase-positive) and strain
#3 was -lactamase-negative. Conversely, strain #1 was susceptible to rifampin and strains
#2 and #3 were resistant to this antimicrobial.
Heteroresistance to vancomycin (hVISA) was observed on strain #3, which showed MIC
values of 12 g/ml for both vancomycin and teicoplanin when tested by Etest using high
inoculum.
Disk diffusion zone diameter results for daptomycin showed a 3 - 4 mm decrease for strain
#3 compared to the first two isolates validating observed higher MIC values. The
vancomycin disk zone diameter results did not change (16 mm) as the MIC increased from 1
to 4 g/ml (Table 2).
All three S. aureus strains demonstrated an identical molecular typing pattern by two
methods (Figure 1).
MIC (g/ml)
Strain # (hospital day/culture type)
Antimicrobial agent
1 (1/blood)
Daptomycin
Vancomycin
Teicoplanin
Dalbavancin
Oxacillin
Penicillin
Clindamycin
Erythromycin
Telithromycin
Quinupristin/dalfopristin
Chloramphenicol
Ciprofloxacin
Gentamicin
Linezolid
Rifampin
Tetracycline
Tigecycline
Trimethoprim/Sulfamethoxazole
0.5
1
2
0.06
>2
16
>2
>8
>4
0.5
8
>4
2
2
0.25
2
0.12
0.5
2 (99/surgical
wound)
0.5
1
2
0.06
>2
16
>2
>8
>4
0.5
8
>4
2
2
>2
2
0.25
0.5
3 (148/bone)
8
4 (12)a
2 (12)a
0.25
>2
0.12
>2
>8
>4
0.5
4
>4
2
1
>2
2
0.06
0.5
Figure 1. Riboprint patterns of the three S. aureus strains evaluated in the present study.
Strains 1 and 2 were susceptible to daptomycin (MIC, 0.5 g/ml) while strain 3 showed
daptomycin MIC of 8 g/ml.
Conclusion
•Resistance to daptomycin may develop during prolonged treatment of S. aureus infections
with daptomycin.
a.MIC in parenthesis using an Etest with an elevated inoculum.
Selected Reading
1.
Table 2. Disk diffusion and -lactamase test results.
Zone diameter (mm)
Antimicrobial agent
Daptomycin
Vancomycin
Oxacillin
Penicillin
Linezolid
Rifampin
-lactamase test
Strain #1
18
16
6
8
27
31
+
Strain #2
19
16
6
9
27
13
+
Strain #3
15
16
10
27
31
6
-
Clinical and Laboratory Standards Institute. (2005) Performance standard for antimicrobial susceptibility testing. Document M100-S15.
Wayne, PA:CLSI.
2. Clinical and Laboratory Standards Institute (2006). Methods for dilution antimicrobial susceptibility tests for bacteria that grow aerobically.
Document M7-A7. Wayne, PA, CLSI (in press).
3. Cubicin (daptomycin for injection) [package insert]. Lexington, MA: Cubist Pharmaceuticals, 2003.
Munoz-Price LS, Lolans K, Quinn JP. (2005) Emergence of resistance to daptomycin during treatment of vancomycin-resistant Enterococcus
faecalis infection. Clinical Infectious Disease 41:565-566.
4. National Committee for Clinical Laboratory Standards. (2003). Performance standards for antimicrobial disk susceptibility tests; Approved
standard, 8th ed. Document M2-A8. Wayne, PA:NCCLS
5. National Committee for Clinical Laboratory Standards. (2003) Methods for dilution antimicrobial susceptibility tests for bacteria that grow
aerobically. Document M7-A6. Wayne, PA:NCCLS.
6.Sabol K, Patterson JE, Lewis II JS, Owens A, Cadena J, Jorgensen JH. (2005) Emergence of daptomycin resistance in Enterococcus faecium
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7. Sakouloas G, Eliopoulos GM, Alder J, Thauvin-Eliopoulos C. (2003). Efficacy of daptomycin in experimental endocarditis due to methicillinresistant Staphylococcus aureus. Antimicrobial Agents and Chemotherapy 47:1714-1718.
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