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. 2014 Apr 4;14:84. doi: 10.1186/1471-2180-14-84

Table 1.

S. aureus isolates used in the study and their β-lactamase genotype and phenotype

# S. aureus isolate β-lactamase genotype* & (‘ blaZ’ PCR) β-lactamase phenotype by nitrocefin disk test
1
29213
Positive
+
2
25923
Negative
-
3
75391-09
Positive
-
4
W5337
Negative
-
5
W53156
Positive
-
6
AI5070237
Positive
+
7
AI5081845
Positive
-
8
159570-08
Positive
-
9
H30876
Positive
-
10
32455-09
Positive$
-
11
HIP12052
Positive
-
12
AI5090298
Positive
-
13
F33263-2
Positive
-
14
AI5090297
Positive
-
15
HIP11033
Positive
-
16
HIP11353
Positive$
-
17
158390-08
Positive$
-
18
F52670
Positive
+
19
H63189
Positive
+
20
M24125
Positive
+
21
F20358.1
Negative
-
22
H67147.3
Positive
-
23
M60028
Negative
-
24
KI58249.2
Unknown
-
25
M69678
Negative
-
26
X33116
Positive
-
27 F29916-2 Positive -

S. aureus strains 29213 (#1) and 25923 (#2) were obtained from ATCC and the S. aureus clinical isolates (#3 - #27) were provided by Dr. Mary Jane Ferraro (Microbiology Labs, Massachusetts General Hospital, Boston, MA, USA). Isolate numbers (e.g. #1 for 29213, etc) are used to refer to the different isolates throughout the study.

*The β-lactamase genotype was determined by PCR to detect blaZ (staphylococcal β-lactamase gene). Genotype data for isolates #3 - #15 was kindly provided by Dr. Robert L. Skov, Statens Serum Institut (R. L. Skov, unpublished results) and for #16 - #27 by Dr. Mary Jane Ferraro.

&All isolates are MSSA.

$Special comment – blaZ contained Stop codon or deletion (so non-functional) (R. L. Skov, unpublished results).

Nitrocefin disk test to determine β-lactamase production was performed as described in Methods. Development of orange colour uniformly, similar to positive control #1, was taken as positive reaction, indicated by ‘+’ symbols. ‘-’ denotes negative result (i.e. no colour change). The results are representative of three independent experiments, which gave consistent results.