What virulence factors enable Staphylococcus aureus to cause blood stream infections? - PowerPoint PPT Presentation

1 / 25
About This Presentation
Title:

What virulence factors enable Staphylococcus aureus to cause blood stream infections?

Description:

What virulence factors enable Staphylococcus aureus to cause blood stream infections? Sadao Jinno1, Steven Seifried2, Matthew J. Bankowski3, and Alan Tice1 – PowerPoint PPT presentation

Number of Views:210
Avg rating:3.0/5.0
Slides: 26
Provided by: 6649493
Category:

less

Transcript and Presenter's Notes

Title: What virulence factors enable Staphylococcus aureus to cause blood stream infections?


1
What virulence factors enable Staphylococcus
aureus to cause blood stream infections?
  • Sadao Jinno1, Steven Seifried2, Matthew J.
    Bankowski3, and Alan Tice1
  • Department of Medicine, John A. Burns School of
    Medicine, University of Hawaii, Honolulu, Hawaii
    1 Department of Cell and Molecular Biology,
    University of Hawaii John A. Burns School of
    Medicine2 Diagnostic Laboratory Services, Inc.
    and The Queens and Kuakini Health Systems,
    Honolulu, Hawaii3

2
Back ground
  • Staphylococcus aureus (S. aureus) is a major
    cause of severe nosocomial and community-acquired
    infections.
  • S. aureus bloodstream infections (BSIs) have been
    reported to cause 30-day mortality of up to 29.

BMJ. 2006333281.
3
Risk factors for Blood Stream Infections
  • Risk factors for BSIs
  • - intravascular catheters
  • - indwelling foreign body
  • - underlying medical conditions

4
Correlations with virulence that have been
reported
  • Panton Valentine Leucocidine (PVL)
  • In a mouse mode, PVL strains produced
    necrotizing pneumonia
  • Toxic Shock Syndrome Toxin (TSST)-1
  • Cause toxic shock syndrome
  • Science. 2007 Feb 23315(5815)1130-3. Epub 2007
    Jan 18.

5
Correlations with virulence that have been
reported
  • Staphylococcal cassette chromosome mec (SCCmec)
  • Type II/III MRSA was associated with a longer
    length of stay
  • J Infect Dis. 20071951678-1685 .

6
Correlations with virulence that has been
reported
  • Spa typing
  • CC5 and CC30 are associated with hematogenous
    complications
  • Arginine Catabolic Mobile Element (ACME)
  • Associated with virulence and the ability to
    colonize humans
  • J Infect Dis. 2007 Sep 1196(5)738-47.
  • Lancet. 2006 Mar 4367(9512)705-6.

7
Our Objective- BSIs
  • To identify the genes and virulence factors of S.
    aureus which facilitate or correlate with their
    ability to gain access to the blood stream

8
Material and method
  • Comparison of S. aureus strains isolated from
    BSIs with those from soft skin tissue infections
    (SSTI) in Hawaii
  • Spa type, the genes for PVL and mec A, TSST-1,
    SCC mec type and antimicrobial susceptibility.

9
Source of specimens
  • The clinical isolates were selected from
    Diagnostic Laboratory service (DLS) and Clinical
    Laboratory Standards Institute
  • S. aureus strains were obtained from the SAM
    culture collection database at the University of
    Hawaii JABSOM. It was begun in 2004 and currently
    consists of molecular biology studies from over
    800 strains of staphylococcus.

10
Laboratory methods
  • Susceptibility tests were performed by using the
    Vitek system (bioMerieux Vitek Inc, Hazelwood,
    MO). All isolates were tested for susceptibility
    to oxacillin, clindamycin, erythromycin,
    gentamicin, levofloxacin, rifampin,
    trimethoprim-sulfamethoxazole (TMP-SMX),
    tetracycline, and vancomycin.
  • Oxacillin was used for methicillin susceptibility
    testing.

11
Statistical methods
  • SAS software was used for statistical analysis.
    Frequency distribution of categorical potential
    risk factors was calculated for each group of
    SSTI and BSI.
  • the between-group-comparisons were made by means
    of Fisher's exact test.
  • A p value of 0.05 was considered statistically
    significant.

12
Results
  • A total of 27 BSI isolates and 295 SSTI S. aureus
    isolates were identified. MRSA isolates accounted
    for 53.7 (173 out of 322).

13
SSTI vs BSI (MSSA and MRSA)
Characteristic SSTI BSI P-value
Inpatient 82(27.9) 22(81.5) lt0.001
MRSA 152(51.5) 22(81.5) 0.004

SCC mec type
Type?a 75(25.5) 11(40.7) 0.110
Type ? 20(6.8) 1(3.7) 1.000
Type ? 42(14) 6(22) 0.262
Mec A 38(12.9) 1(3.7) 0.441
Mec B 5(1.7) 1(3.7) 1.000
CCR1 2(0.7) 0(0) 1.000
CCR2 22(7.5) 2(7.4) 1.000
Values are numbers of isolates. Values in
parentheses are percentages
14
SSTI vs BSI (MSSA and MRSA)
Characteristic SSTI BSI P-value
PVL 155(54.2) 11(40.7) 0.227
TSST-1 5 (1.7) 2 (7.4) 0.109
Spa type
CC8 145 (54.9) 12 (48) 0.691
CC2 39 (14.8) 6 (24) 0.240
CC12 16 (6.1) 0 (0) 0.379
CC85 11 (4.2) 2 (8) 0.229
15
SSTI vs BSI (MRSA)
Characteristic SSTI (MRSA) BSI (MRSA) P-value
Inpatient 62(40.8) 19(86.4) lt0.001

SCC mec type
Type?a 74(48.7) 11(50.0) 1.000
Type ? 20(13.2) 1(4.5) 0.480
Type ? 31(20.4) 6(27.3) 0.577
Mec A 4(2.6) 1(4.5) 0.496
Mec B 2(1.3) 1(4.5) 0.335
CCR1 0(0) 0(0) 1.000
CCR2 12(7.9) 2(9.1) 0.692
16
SSTI vs BSI (MRSA)
Characteristic SSTI (MRSA) BSI (MRSA) P-value
PVL 155(54.2) 11(40.7) 0.227
TSST-1 5 (1.7) 2 (7.4) 0.109
Spa type
CC8 106 (74.1) 10 (50.0) 0.030
CC2 22 (15.4) 6 (30.0) 0.131
CC12 9 (6.3) 0 (0) 0.605
CC85 2 (1.4) 0 (0) 1.000
17
Antimicrobial Percentage of susceptible isolates (MSSA and MRSA ) Percentage of susceptible isolates (MSSA and MRSA ) P-value
Antimicrobial SSTI BSI P-value
Oxacillin 141 (48.6) 5 (21.7) 0.016
Levofloxacin 258 (87.1) 15 (57.1) 0.001
Clindamycin 250 (85.9) 14 (56.5) 0.001
Erythromycin 132 (45.2) 7 (26.1) 0.084
Gentamicin 293 (99.3) 24 (91.3) 0.028
Tetracycline 281 (95.5) 21 (78.3 ) 0.006
Rifampin 295 (100) 27 (100) 1.000
TMP-SMXa 292 (99.0) 27 (100) 1.000
Vancomycin 295 (100) 27 (100) 1.000
18
Antimicrobial Percentage of susceptible isolates (Only MRSA) Percentage of susceptible isolates (Only MRSA) P-value
Antimicrobial SSTI (MRSA) BSI (MRSA) P-value
Levofloxacin 112(74.6) 7 (43.8) 0.017
Clindamycin 118(78.0) 8 (44.4) 0.004
Erythromycin 24(15.9) 11 (5.6) 0.479
Gentamicin 148 (98.7) 17 (88.9) 0.057
Tetracycline 139 (92.7) 14 (72.2) 0.016
Rifampin 150 (99.3) 20 (100) 1.000
TMP-SMX 149 (98.0) 20 (100) 1.000
Vancomycin 152 (100) 20 (100) 1.000
19
Highlights
  • There was no significant difference in SCC mec
    and Spa type between SSTI and BSI isolates.

20
Highlights
  • PVL was not associated with BSIs
  • 53 of SSTI and 42 of BSIs
  • p 0.227
  • TSST-1 was not associated with BSIs
  • 1.7 of SSTI and 7.7 of BSIs
  • p0.109

21
Highlights
  • MRSA BSI isolates exhibited a significant
    resistance to clindamycin, tetracycline and
    levofloxacin compared with MRSA SSTI isolates (P
    lt0.05).
  • A higher proportion of MRSA BSI isolates was
    resistant to gentamicin compared with MRSA SSTI
    isolates, almost reaching a statistical
    significance level (P 0.056).
  • Both MRSA SSTI and BSI showed significant
    resistances to erythromycin (P0.479).

22
Limitations
  • Retrospective study
  • No clinical information
  • Limited number of isolates

23
Conclusion
  • The differences we have found between blood and
    SSTI isolates suggest PVL, SCC mec, Spa type are
    not significant virulence factors for BSIs in
    Hawaii
  • TSST-1 may be associated with BSIs.

24
Conclusion
  • The correlation of bacteremia and some
    antibiotics susceptibility may be a useful
    clinical tool in evaluation and treating blood
    stream infections.

25
Plan
  • Further studies are needed with more specimens
    and clinical correlations.
Write a Comment
User Comments (0)
About PowerShow.com