1737. In Vitro Susceptibility of Gemella species from Clinical Isolates
Session: Poster Abstract Session: Novel Diagnostics for Uncommon Bacteria
Saturday, October 10, 2015
Room: Poster Hall

Background:

Gemella species (GS) are normal human flora that can cause serious infections such as endocarditis. Minimum inhibitory concentration (MIC) breakpoints were recently established in the CLSI M45 A3 document. Published guidelines emphasize that antimicrobial susceptibility testing (AST) for GS is unpredictable. There is limited published evidence regarding interpretation of MIC breakpoints in GS isolates. 

Methods:

14 clinical isolates of GS from 2007 to 2015 were recovered from a single center. AST was performed by the CLSI broth microdilution method (BMD) in cation-adjusted Muller Hinton broth supplemented with 2.5% lysed horse blood. BMD tests were incubated at 35C in 5% CO2 for 20 hours.  MICs were interpreted according to M45 A3 breakpoints. Chart review was performed to document treatment and outcomes.

Results:

MIC data were available for 8 (57%) GS isolates from blood, 5 (36%) from urine, and 1 (7.1%) from vitreous fluid. All but a single isolate (from blood) were susceptible to all beta-lactams, including penicillin (PEN), cefotaxime (CFX), ceftriaxone (CTX), and meropenem (MEM). 13 (93%), 12 (86%) and 7 (50%) isolates were susceptible to vancomycin (VAN), clindamycin (CLI) and erythromycin (ERY) / levofloxacin (LVX), respectively.  7 of 8 (87.5%) patients with positive blood cultures were treated with beta-lactams, and all cleared follow-up cultures. Zero patients with positive urine cultures received beta-lactams, and only 1 (20%) was treated with a fluoroquinolone. The case of GS endophthalmitis was treated with intra-vitreous vancomycin.

Table. No. Susceptible Isolates

Source (n)

PEN < 0.12

CFX <= 1

CTX <= 1

MEM <= 0.5

VAN <= 1

ERY <= 0.25

LVX <= 1

CLI <= 0.25

 Blood (8)

7 (87.5%)

7 (87.5%)

7 (87.5%)

7 (87.5%)

7 (87.5%)

4 (50%)

3 (37.5%)

6 (75%)

 Urine (5)

5 (100%)

5 (100%)

5 (100%)

5 (100%)

5 (100%)

2 (40%)

3 (60%)

5 (100%)

 Vitreous (1)

1 (100%)

1 (100%)

1 (100%)

1 (100%)

1 (100%)

1 (100%)

1 (100%)

1 (100%)

 Overall (14)

13 (93%)

13 (93%)

13 (93%)

13 (93%)

13 (93%)

7 (50%)

7 (50%)

12 (86%)

Conclusion:

Clinical isolates of GS were most consistently susceptible to beta-lactams and vancomycin. Other agents showed variable activity. Since AST for GS may be unpredictable, susceptibility testing should be performed when GS infections occur.

Jonathan Baghdadi, MD, Division of Infectious Diseases, David Geffen School of Medicine at UCLA, Los Angeles, CA, Theodoros Kelesidis, MD, PhD, David Geffen School of Medicine at UCLA, Los Angeles, CA and Romney Humphries, Ph.D., Department of Pathology and Laboratory Medicine, UCLA, Los Angeles, CA

Disclosures:

J. Baghdadi, None

T. Kelesidis, None

R. Humphries, None

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