Demographics and clinical characteristics
Figure 1 shows the overall experimental flow. The organisms of interest, E. coli and K. pneumoniae, were identified in urine cultures from 885 unique patients during the study period. Of these, 11 were removed from the dataset: 9 cases were missing data, and 2 cases were identified to contain 2 pathogenic species. Table 1 shows a comparison of the demographic and clinical factors between the ESBL-PE and non-ESBL-PE patients. The median (IQR) ages at presentation were 65.5 (52-76) years for the ESBL-PE group and 61 (49-74) years for the non-ESBL-PE group (P< 0.001). The proportions of ESBL-PE infections among males and females were 33.5% and 66.5%, respectively (P = 0.05). The two groups were compared across numerous factors: several comorbid diseases, hospital admission history, invasive urological procedure treatment history, and antibiotic use in the past 3 months. Those which showed significant differences (P < 0.05) were: diabetes mellitus, severe underlying disease, a hospital stay in the preceding 3 months, prior admission to the medical department, prior admission to the surgical department, prior admission to the ICU, undergoing an invasive urological procedure, and antibiotic use in the past 3 months. Among microorganisms, E. coli (739 cases, 84.6%) was the most commonly isolated species, with K. pneumoniae (135 cases, 15.4%) comprising the remainder.
Table 1. Demographic data, clinical characteristics
Variables
|
Overall (n=874)
|
Non-ESBL-PE (n=602)
|
ESBL-PE
(n=272)
|
P value
|
Gender, n (%)
|
|
|
|
0.050
|
Male
|
236 (27.0)
|
145 (24.1)
|
91 (33.5)
|
|
Female
|
638 (73.0)
|
457 (75.9)
|
181 (66.5)
|
|
Age (years), [median (IQR)]
|
62.0 (50-75)
|
61 (49-74)
|
65.5(52-76)
|
<0.001
|
Comorbidity diseases
|
|
|
|
|
Diabetes mellitus, n (%)
|
|
|
|
0.038
|
Yes
|
287 (32.8)
|
211 (35.0)
|
76 (27.9)
|
|
No
|
587 (67.2)
|
391 (65.0)
|
196 (72.1)
|
|
Chronic renal failure, n (%)
|
|
|
0.208
|
Yes
|
123 (14.1)
|
91 (15.1)
|
32 (11.8)
|
|
No
|
751 (85.9)
|
511 (84.9)
|
240 (88.2)
|
|
Immunodeficiency, n (%)
|
|
|
0.056
|
Yes
|
51 (5.8)
|
29 (4.8)
|
22 (8.1)
|
|
No
|
823 (94.2)
|
573 (95.2)
|
250 (91.9)
|
|
Neoplasia, n (%)
|
|
|
|
0.072
|
Yes
|
103 (11.8)
|
63 (10.5)
|
40 (14.7)
|
|
No
|
771 (88.2)
|
539 (89.5)
|
232 (85.3)
|
|
Recurrent Urinary tract infections, n (%)
|
|
|
<0.001
|
Yes
|
134 (15.3)
|
66 (11.0)
|
68 (25.0)
|
|
No
|
740 (84.7)
|
536 (89.0)
|
204 (75.0)
|
|
Severe underlying disease, n (%)
|
|
|
0.009
|
Yes
|
66 (7.6)
|
36 (6.0)
|
30 (11.0)
|
|
No
|
808 (92.4)
|
566 (94.0)
|
242 (89.0)
|
|
Hospital stay in preceding 3 months, n (%)
|
|
|
<0.001
|
Yes
|
309 (35.4)
|
168 (27.9)
|
141 (51.8)
|
|
No
|
565 (64.6)
|
434 (72.1)
|
131 (48.2)
|
|
Previous hospitalization department
|
|
|
|
Medical department, n (%)
|
|
|
0.005
|
Yes
|
265 (30.3)
|
165 (27.4)
|
100 (36.8)
|
|
No
|
609 (69.7)
|
437 (72.6)
|
172 (63.2)
|
|
Surgical department, n (%)
|
|
|
|
<0.001
|
Yes
|
174 (19.9)
|
99 (16.4)
|
75 (27.6)
|
|
No
|
700 (80.1)
|
503 (83.6)
|
197 (72.4)
|
|
Intensive Care Unit (ICU), n (%)
|
|
|
0.047
|
Yes
|
10 (1.1)
|
4 (0.7)
|
6 (2.2)
|
|
No
|
864 (98.9)
|
598 (99.3)
|
266 (97.8)
|
|
Invasive urological procedure, n (%)
|
|
|
<0.001
|
Yes
|
269 (30.8)
|
150 (24.9)
|
119 (43.8)
|
|
No
|
605 (69.2)
|
452 (75.1)
|
153 (56.3)
|
|
Antibiotic use in the past 3 months, n (%)
|
|
|
<0.001
|
Yes
|
190 (21.7)
|
91 (15.1)
|
99 (36.4)
|
|
No
|
684 (78.3)
|
511 (84.9)
|
173 (63.6)
|
|
Microorganism, n (%)
|
|
|
|
Escherichia coli
|
739 (84.6)
|
540 (89.7)
|
199 (73.2)
|
<0.001
|
Klebsiella sp.
|
135 (15.4)
|
62 (10.3)
|
73 (26.8)
|
<0.001
|
Mortality, n (%)
|
|
|
|
|
Secondary to infection
|
6 (0.7)
|
4 (0.7)
|
2 (0.7)
|
0.604
|
Other cause
|
7 (0.8)
|
3 (0.5)
|
4 (1.5)
|
0.140
|
Following random sampling, 611 patients, including 191 (31.3%) ESBL-PE patients, were included in the training set. The remaining 263 patients, with 82 (31.2%) ESBL-PE patients, were assigned to the validation set. No significant difference in the variables was observed between the training validation sets (all P > 0.05), as shown in Table 2.
Table 2. Clinical features and risk factor exposition in the study population.
Variables
|
Overall
(n=874)
|
Training set
(n=611)
|
Validation set
(n = 263)
|
P value
|
Status, n (%)
|
|
|
|
0.981
|
ESBL-
|
602 (68.9)
|
420 (68.7)
|
181 (68.8)
|
|
ESBL+
|
272 (31.1)
|
191 (31.3)
|
82 (31.2)
|
|
Gender, n (%)
|
|
|
|
0.111
|
Male
|
236 (27.0)
|
176 (28.8)
|
62 (23.6)
|
|
Female
|
638 (73.0)
|
435 (71.2)
|
201 (76.4)
|
|
Age, n (%)
|
|
|
|
0.543
|
0 to 18 years
|
70 (8.0)
|
49 (8.0)
|
21 (8.0)
|
|
18 to 60 years
|
309 (35.4)
|
209 (34.2)
|
100 (38.0)
|
|
Over 60 years
|
495 (56.6)
|
353 (57.8)
|
142 (54.0)
|
|
Comorbidity diseases
|
|
|
|
|
Diabetes mellitus, n (%)
|
|
|
|
0.920
|
Yes
|
287 (32.8)
|
200 (32.7)
|
87 (33.1)
|
|
No
|
587 (67.2)
|
411 (67.3)
|
176 (66.9)
|
|
Chronic renal failure, n (%)
|
|
|
|
0.998
|
Yes
|
123 (14.1)
|
86 (14.1)
|
37 (14.1)
|
|
No
|
751 (85.9)
|
525 (85.9)
|
226 (85.9)
|
|
Immunodeficiency, n (%)
|
|
|
|
0.913
|
Yes
|
51 (5.8)
|
36 (5.9)
|
15 (5.7)
|
|
No
|
823 (94.2)
|
575 (94.1)
|
248 (94.3)
|
|
Neoplasia, n(%)
|
|
|
|
0.170
|
Yes
|
103 (11.8)
|
78 (12.8)
|
25 (9.5)
|
|
No
|
771 (88.2)
|
533 (87.2)
|
238 (90.5)
|
|
Recurrent Urinary tract infections, n (%)
|
|
|
0.496
|
Yes
|
134 (15.3)
|
97 (15.9)
|
37 (14.1)
|
|
No
|
740 (84.7)
|
514 (84.1)
|
226 (85.9)
|
|
Severe underlying disease, n (%)
|
|
|
|
0.056
|
Yes
|
66 (7.6)
|
53 (8.7)
|
13 (4.9)
|
|
No
|
808 (92.4)
|
558 (91.3)
|
250 (95.1)
|
|
Hospital admission history
|
|
|
|
|
Admission times, n (%)
|
|
|
|
0.555
|
1 to 2 times
|
645 (73.8)
|
455 (74.5)
|
190 (72.2)
|
|
3 to 6 times
|
159 (18.2)
|
111 (18.2)
|
48 (18.3)
|
|
More than 6 times
|
70 (8.0)
|
45 (7.4)
|
25 (9.5)
|
|
Hospital stay in preceding 3 months, n (%)
|
|
|
|
0.645
|
Yes
|
309 (35.4)
|
219 (35.8)
|
90 (34.2)
|
|
No
|
565 (64.6)
|
392 (64.2)
|
173 (65.8)
|
|
Previous hospitalization department
|
|
|
|
Medical department, n (%)
|
|
|
|
0.905
|
Yes
|
265 (30.3)
|
186 (30.4)
|
79 (30.0)
|
|
No
|
609 (69.7)
|
425 (69.6)
|
184 (70.0)
|
|
Surgical department, n (%)
|
|
|
0.111
|
Yes
|
174 (19.9)
|
113 (18.5)
|
61 (23.2)
|
|
No
|
700 (80.1)
|
498 (81.5)
|
202 (76.8)
|
|
Intensive Care Unit (ICU), n (%)
|
|
|
|
0.724
|
Yes
|
10 (1.1)
|
8 (1.3)
|
2 (0.8)
|
|
No
|
864 (98.9)
|
603 (98.7)
|
261 (99.2)
|
|
Treatment history
|
|
|
|
|
Invasive urological procedure, n (%)
|
|
|
|
0.880
|
Yes
|
269 (30.8)
|
189 (30.9)
|
80 (30.4)
|
|
No
|
605 (69.2)
|
422 (69.1)
|
183 (69.6)
|
|
Antibiotic use in the past 3 months, n (%)
|
|
|
|
0.570
|
Yes
|
190 (21.7)
|
136 (22.3)
|
54 (20.5)
|
|
No
|
684 (78.3)
|
475 (77.7)
|
209 (79.5)
|
|
Independent risk factors in the training set
The risk factor analysis was based on the 874 patients in the training set. Univariate and multivariate analysis for ESBL-PE infection is shown in Table 3. Eleven variables were identified by univariate analysis (P < 0.1): gender, age, immunodeficiency, urinary tract infections, severe underlying disease, hospital stay in preceding 3 months, prior admission to medical department, prior admission to surgical department, prior admission to ICU, prior invasive urological procedure, and antibiotic use in the past 3 months.
Table 3. Univariate and Multivariate analysis in the training set.
Variables
|
Univariate
|
Multivariate
|
OR
|
95% CI
|
P value
|
OR
|
95% CI
|
P value
|
Gender
|
|
|
|
|
|
|
Male
|
1.654
|
1.143-2.388
|
0.0073
|
1.607
|
1.066-2.416
|
0.023
|
Female
|
Reference
|
|
|
Reference
|
|
|
Age
|
|
|
|
|
|
|
0 to 18 years
|
Reference
|
|
|
Reference
|
|
|
18 to 60 years
|
3.712
|
1.529-11.108
|
0.008
|
2.825
|
1.119-8.679
|
0.043
|
Over 60 years
|
4.765
|
2.015-14.035
|
0.001
|
4.100
|
1.678-12.343
|
0.005
|
Diabetes mellitus
|
|
|
|
|
|
|
Yes
|
0.884
|
0.610-1.274
|
0.513
|
|
|
|
No
|
Reference
|
|
|
|
|
|
Chronic renal failure
|
|
|
|
|
|
Yes
|
0.886
|
0.529-1.446
|
0.637
|
|
|
|
No
|
Reference
|
|
|
|
|
|
Immunodeficiency
|
|
|
|
|
|
Yes
|
1.829
|
0.914-3.606
|
0.082
|
1.671
|
0.770-3.579
|
0.187
|
No
|
Reference
|
|
|
Reference
|
|
|
Neoplasia
|
|
|
|
|
|
|
Yes
|
1.444
|
0.875-2.351
|
0.143
|
|
|
|
No
|
Reference
|
|
|
|
|
|
Recurrent urinary tract infections
|
|
|
|
|
|
Yes
|
2.181
|
1.398-3.396
|
<0.001
|
1.145
|
0.645-2.011
|
0.639
|
No
|
Reference
|
|
|
Reference
|
|
|
Severe underlying disease
|
|
|
|
|
|
Yes
|
2.294
|
1.295-4.058
|
0.004
|
1.536
|
0.805-2.907
|
0.188
|
No
|
Reference
|
|
|
Reference
|
|
|
Admission times
|
|
|
|
|
|
|
1 to 2 times
|
Reference
|
|
|
|
|
|
3 to 6 times
|
1.047
|
0.664-1.627
|
0.841
|
|
|
|
More than 6 times
|
1.380
|
0.719-2.580
|
0.320
|
|
|
|
Hospital stay in preceding 3 months
|
|
|
|
|
|
|
Yes
|
3.067
|
2.152-4.389
|
<0.001
|
1.872
|
1.141-3.067
|
0.013
|
No
|
Reference
|
|
|
Reference
|
|
|
Medical department
|
|
|
|
|
|
Yes
|
1.516
|
1.052-2.179
|
0.025
|
0.799
|
0.498-1.266
|
0.344
|
No
|
Reference
|
|
|
Reference
|
|
|
Surgical department
|
|
|
|
|
|
Yes
|
1.751
|
1.145-2.663
|
0.009
|
0.943
|
0.572-1.533
|
0.816
|
No
|
Reference
|
|
|
Reference
|
|
|
Intensive Care Unit (ICU)
|
|
|
|
|
|
Multivariate analysis was performed with the eleven variables identified by univariate analysis. Five variables were proved to be independent predictors for ESBL-PE infection: male gender (OR=1.607, 95% CI 1.066-2.416), older age (OR=4.100, 95% CI 1.678-12.343), a hospital stay in preceding 3 months (OR=1.872, 95% CI 1.141-3.067), invasive urological procedure (OR=1.810, 95% CI 1.197-2.729), and antibiotic use within the previous 3 months (OR 0.546, 95% CI 0.314-0.948).
Predictive model construction and validation
An ESBL-PE infection risk estimation nomogram model was developed by logistic regression using the five independent predictors (Figure 2). When present, each of the predictors contributes between 30 and 100 points to a final point total. This point total is then used to estimate the probability that the patient should can diagnosed as ESBL-PE positive.
The AUC was used to evaluate the discriminatory capacity of the predictive model, and the nomogram demonstrated good accuracy in estimating the risk of ESBL-PE infection. The AUC of ROC was 0.714 (95% CI, 0.671–0.757) in the training set (Figure 3A). In validation set, the AUC of ROC was 0.650 (95% CI, 0.577-0.725) (Figure 3B).
A calibration plot and Hosmer–Lemeshow test were used to the calibrate the predictive model (Figure 4). The calibration curves show the predictive model and the validation set produce very good fits of the data. The Hosmer-Lemeshow test indicates that the predicted probability is highly consistent with the actual probability (training set, P=0.999; validation set, P=0.732). Decision curve analysis, shown in Figure 5, was used to demonstrate the net benefits of this predictive model. Its strong predictive capacity allows for accurate diagnosis, which should result in better patient treatment than either non-diagnosis or full diagnosis.
Antibiotic susceptibility testing
Table 4 indicates the overall antimicrobial susceptibility of PE to the antibiotics tested. The highest sensitivity was observed with amikacin (94.7 %), carbapenem (95.0%), polymyxin (99.2%), tigecycline (98.9%), and latamoxef (91.2 %). Except for latamoxef and cefdinir, there are statistically significant (P < 0.05) differences in the susceptibility of all antibacterial drugs between the two groups.
Table 4. Antibiogram result of PE.
Antibiotics
|
Antibiogram result
|
Total
|
SEN
|
P value
|
Non-ESBL-PE
|
ESBL-PE
|
S
|
I
|
R
|
SEN
|
S
|
I
|
R
|
SEN
|
|
|
ciprofloxacin
|
304
|
24
|
265
|
51.3
|
39
|
5
|
220
|
14.8
|
857
|
40.0
|
<0.001
|
Levofloxacin
|
246
|
66
|
246
|
44.1
|
35
|
18
|
219
|
12.9
|
874
|
32.2
|
<0.001
|
P/T
|
580
|
14
|
8
|
96.3
|
167
|
35
|
69
|
61.6
|
873
|
85.6
|
<0.001
|
Ceftazidime
|
540
|
43
|
16
|
90.2
|
26
|
49
|
196
|
9.6
|
870
|
65.1
|
<0.001
|
C/S
|
590
|
7
|
3
|
98.3
|
166
|
31
|
75
|
61.0
|
872
|
86.7
|
<0.001
|
Cefepime
|
533
|
23
|
45
|
88.7
|
18
|
46
|
207
|
6.6
|
872
|
63.2
|
<0.001
|
Aztreonam
|
561
|
1
|
30
|
94.8
|
18
|
2
|
242
|
6.9
|
854
|
67.8
|
<0.001
|
Amikacin
|
595
|
4
|
3
|
98.8
|
233
|
4
|
35
|
85.7
|
874
|
94.7
|
<0.001
|
Tobramycin
|
438
|
115
|
39
|
74.0
|
127
|
53
|
81
|
48.7
|
853
|
66.2
|
<0.001
|
Carbapenem
|
602
|
0
|
0
|
100.0
|
228
|
0
|
44
|
83.8
|
874
|
95.0
|
<0.001
|
TMP-SMX
|
312
|
1
|
288
|
51.9
|
82
|
0
|
188
|
30.4
|
871
|
45.2
|
<0.001
|
Polymyxin
|
600
|
0
|
2
|
99.7
|
267
|
0
|
5
|
98.2
|
874
|
99.2
|
0.033
|
Doxycycline
|
271
|
123
|
204
|
45.3
|
73
|
43
|
155
|
26.9
|
869
|
39.6
|
<0.001
|
Minocycline
|
371
|
80
|
139
|
62.9
|
96
|
39
|
126
|
36.8
|
851
|
54.9
|
<0.001
|
Tigecycline
|
590
|
0
|
2
|
99.7
|
238
|
0
|
7
|
97.1
|
837
|
98.9
|
0.004
|
Cefixime
|
45
|
0
|
134
|
25.1
|
1
|
0
|
235
|
0.4
|
415
|
11.1
|
<0.001
|
Latamoxef
|
53
|
0
|
2
|
96.4
|
50
|
0
|
8
|
86.2
|
113
|
91.2
|
0.095
|
Cefdinir
|
1
|
0
|
20
|
4.8
|
1
|
0
|
93
|
1.1
|
115
|
1.7
|
0.333
|
Ceftriaxone
|
388
|
0
|
3
|
99.2
|
2
|
0
|
45
|
4.3
|
438
|
89.0
|
<0.001
|
Cefmetazole
|
92
|
0
|
0
|
100.0
|
4
|
0
|
14
|
22.2
|
110
|
87.3
|
<0.001
|
Ceftizoxime
|
39
|
0
|
0
|
100.0
|
0
|
0
|
10
|
0.0
|
49
|
79.6
|
<0.001
|
S: Sensitive; I: Intermediate; R: Resistant; SEN: Sensitivity, %; P/T: piperacillin/tazobactam; C/S: cefoperazone/sulbactam; TMP-SMX: trimethoprim–sulfamethoxazole