Antibiotic-resistance profile of Staphylococcus aureus

2. • is an opportunistic microorganism that colonises the skin and mucous
of about 30 % of healthy humans.
• can cause severe infection with impact on population groups at risk
(immunocompromised hosts, newborns).
• oxacillin-resistant form (MRSA) has been the
most important cause of antimicrobial-
resistant healthcare-associated infections
worldwide.
• MRSA is resistant to all beta-lactam antibiotics
caused by a modified penicillin binding
protein, PBP2a, encoded by mecA and mecC
genes .
The ability of bacteria to quickly develop resistance to other classes of
antibiotics requires strict monitoring of the detection of MDR strains.

3. Increasing levels of infections with
MRSA are being reported from many
parts of the world.
In Europe (2013-2016), MRSA was observed
with percentages varying from zero to 57.2%,
representing a serious health problem for at
least 10 countries, including Romania.
EARS-Net surveillance
November 2017

4. This study aims to:
highlight common elements and distinctive
features of the frequency and the distribution of
MRSA strains harvested from a maternity
hospital in the north-eastern Romania;
characterize antibiotic resistance profiles.

5. 54 strains S. aureus included
in the cross-sectional study
were isolated from samples
collected from
newborn with skin infections (20
strains)
purulent secretions
nasal swabs
conjunctival secretions
skin tampons
apparently healthy carriers - mothers,
medical personnel (28 strains)
nasal swabs
pharyngeal swabs
lochia
the surfaces (6 strains)
The results obtained were analyzed and interpreted using the Epiinfo version 7.2.2.
p-value < 0.05 was considered statistically significant.

6. ≤21 mm
Methicillin-resistant
≥22 mm
Methicillin-sensitive
+
-
Confirmation MRSA
MIC Oxa
PB2a or PCR mecA
MRSA
MSSA
Other classes of
antibiotics
Screening cefoxitin 30 µg
Fig. 2. Determining MIC using
AST- VITEK cards
Fig.1 MecA gene amplification
curves by Real Time PC
Glycopeptides Macrolides,
Aminoglycosides,
Tetracyclines, Fluoroquinolones,
Lincosamides, Oxazolidinones,
Folate pathway inhibitors

7. MRSA versus MSSA
Frequency of isolation in samples
•
38,9%
9,2%
35,2%
16,7%
61,1%
MSSA MRSA environm MRSA newborn MRSA adults
More than 2/3 of the examined
strains were characterized as
MRSA, most were isolated
from newborns (35,2%).
There is a much lower share of
MRSA detection in samples
from apparently healthy
carriers (16.7%) and swabs
taken from various surfaces -
incubators, tables, walls (9.2%)

8. 95 %
32,1 %
5 %
67,9 %
0
10
20
30
40
50
60
70
80
90
100
newborns adults
MRSA MSSA
RR =
RR =
RR = 2,96 (CI: 1,71; 5,12; χ2= 16,46, p<0,001)

9. 5,3 %
31,6 %
36,8 %
26,3 %
55,7 %
22,2 %
0
10
20
30
40
50
60
newborns adults
conjunctival secretion
purulent secretion
skin swab
nasal swab
pharyngeal swab
lochia
It is identified a relative comparable distribution of MRSA strains in skin swabs,
purulent secretions and nasal swabs collected from newborns.
Regarding adults, MRSA was isolated mainly from nasal swabs (55,7%).

10. Antibiotic type MRSA MSSA P value
Penicillin (P) 33/33 16/21 >0,05
Cefoxitin (FOX) 33/33 0/21 <0,001
Oxacilin (OX) 33/33 0/21 <0,001
Cefuroxime (CFX) 31/33 3/21 <0,01
Erythromycin (E) 28/33 3/21 <0,05
Clindamycin (CM) 6/33 3/21 >0,05
Ciprofloxacin (CIP) 2/33 2/21 >0,05
Levofloxacin (LEV) 2/33 3/21 >0,05
Gentamicin (G) 0/33 0/21 p=1
Rifampicin (RIF) 0/33 0/21 p=1
Tetracyclin (TE) 6/33 4/21 >0,05
Trimeth.–sulf( SXT) 1/33 1/21 >0,05
Fusidic acid (FUS) 0/33 1/21 >0,05
Vancomycin (VA) 0/33 0/21 p=1
Tigecycline (TG) 0/33 0/21 p=1
Mupirocin (M) 0/33 0/21 p=1
Linezolid (LZD) 0/33 0/21 p=1
Tobramicin (TOB) 0/33 0/21 p=1
Teicoplanin (TEC) 0/33 0/21 p=1
According to the susceptibility test results, all S.
aureus isolated were identified as sensitive against
mupirocin, gentamicin, tobramicin, teicoplanin, tigecy-
cline, vancomycin and linezolid.
Resistance to erythromycin was
significantly associated with MRSA strains
(p<0,05)
No significant differences were observed
between MRSA and MSSA strains for
resistance to Ciprofloxacin, Levofloxacin,
Tetracycline, Clyndamycin, Trimethoprim-
sulfametoxazol.
0 20 40 60 80 100
P
FOX
OX
CFX
E
CM
CIP
LEV
TE
SXT
FUS
%
P FOX OX CFX E CM CIP LEV TE SXT FUS
MSSA (%) 76.2 4.4 1.8 2.8 14.3 14.3 9.5 14.3 19 4.8 4.8
MRSA (%) 100 100 100 93.9 84.8 18.2 6.1 6.1 18.2 3 0

11. Phenotype
of resistance
Antibiotic
No. of
isolated
strains
MDR/
non MDR
R1
P, OX, FOX 5
(14,7%)
non MDR
R2
P, OX,
FOX,E, CM,
TE
4
(11,8%)
MDR
R3
P, OX, FOX,
E, CM, TE,
LEV
2
(5,9%)
MDR
R4
P, FOX, OX,
E
22
(64,7%)
non MDR
R5
P, FOX, OX,
SXT
1
(3,2%)
non MDR
3,2%
, 14.7%,
11,8%
64,7%
5.9%,
17,7%
R5 R4 R1 MDR R2 R3
5 phenotypes were observed for
MRSA strains, often associated
with resistance to erythromycin
profile (64.7%).
Only 6 MRSA strains were MDR (17.7%), with the detection of resistance
to ≥3 antibiotics (R2-5,9% and R3-11,8%).

12. 16,7%
67,8 %
5 %
50 %
15%
33,3 %
7,2 %
80 %
3,6 %
21,4 %
0
20
40
60
80
100
120
Environment Adults Newborns
MDR (R2; R3)
MRSA+SXT (R5)
MRSA+E (R4)
MRSA (R1)
MSSA
Depending on the original
source, association of MRSA
with erythromycin resistance
was isolated from newborns
(80%) about 3 times more
than swabs taken from
surfaces (33,3%).
The MDR strains (21,4%) were isolated only from mothers, with a potential risk
of contamination of the newborn.

13. The highest rate of MDR strains isolation (66.8%) correspond to the nasal
swabs of adults, while the combination of MRSA with resistance to
erythromycin was identical discovered in the purulent and conjunctival
secretions from newborns (37,5%).
33,3 37,5
33,3 25
66,8
50
37,5
33,3
50
16,6
0
10
20
30
40
50
60
70
80
90
100
MRSA(newborn) MRSA + E (newborn) MDR (adults) MRSA +E (adults)
%
conjunctival secretion exsudate nasal purulent secretions
skin tampons exsudate pharyngeal lochia

14.  Real Time-PCR is a useful technique for epidemiological
surveillance of MRSA strains, it can be applied in the future,
for the rapid detection directly in pathological product.
 The data obtained reveal a diversity of phenotypes for
different classes of antibiotic resistance, while maintaining
sensitivity to glicopepide, linezolid, fusidic acid, gentamicin
and mupirocin.
 The study stresses the need for regular monitoring of MRSA
strains circulating in the hospital to prevent a potential
epidemic outbreak in the context of frequent involvement in
the etiology of neonatal infections.