Table 1 Characteristics of the patients
Groups
|
Acute PJI
|
Delayed PJI
|
Chronic PJI
|
χ2 /t-value
|
p
|
n
|
25
|
91
|
86
|
-
|
-
|
Gender(male/female)
|
13/12
|
38/53
|
33/53
|
1.483
|
0.476
|
Age (years,mean SD)
|
64.16±16.13
|
62.02±13.14
|
63.77±12.23
|
0.818
|
0.664
|
Hip/Knee
|
12/13
|
38/53
|
52/34
|
6.261
|
0.044
|
Complication
|
Hypertension
|
7(22.58%)
|
40(35.4%)
|
32(29.63%)
|
20.610
|
0.300
|
Diabetes
|
6(19.35%)
|
18(15.93%)
|
15(13.89%)
|
Arrhythmia
|
4(12.9%)
|
18(15.93%)
|
17(15.74%)
|
Phlebothrombosis
|
4(12.9%)
|
7(6.19%)
|
9(8.33%)
|
Osteoporosis
|
2(6.45%)
|
0(0.00%)
|
2(1.85%)
|
Anemia
|
2(6.45%)
|
4(3.54%)
|
5(4.63%)
|
Cerebral Infarction
|
3(9.68%)
|
3(2.65%)
|
5(4.63%)
|
Coronary Heart Disease
|
1(3.23%)
|
14(12.39%)
|
17(15.74%)
|
Hypoproteinemia
|
2(6.45%)
|
4(3.54%)
|
2(1.85%)
|
Phlebothrombosis
|
0(0.00%)
|
5(4.42%)
|
4(3.70%)
|
Patients’ History
The clinical data of 202 patients with PJI after primary hip/knee arthroplasty from January 2017 to December 2021 were retrospectively analyzed. There were 84 males and 118 females, aged (63.03±13.10) years (range: 24 to 89 years). One hundred and two patients underwent total hip arthroplasty and one hundred patients underwent total knee arthroplasty. According to the time of postoperative infection, patients were classified as acute according to the time of postoperative infection PJI group (onset time was 3 months after surgery), delayed PJI group (onset time was 3 months to 2 years after surgery) and chronic PJI group (onset longer than 2 years after surgery)14. In this group of 202 patients, the patients were divided into the acute PJI group (25 cases), delayed PJI group (91 cases) and chronic PJI group (86 cases). There were no significant differences in gender, age and complications among the three groups (P < 0.05). The number of hip infection cases in the chronic group was higher than that in the delayed group (χ²=6.191, P=0.013). There was no significant difference between the acute and delayed group (χ²=0.312, P=0.577). There was no significant difference between the acute and chronic group (χ²=1.233, P=0.267). The demographic characteristics of 202 participants are listed in Table 1.
Pathogens
Among the 202 PJI patients in this study, 160 (79.21%) were positive for microbial culture, including 119 (58.91%) gram-positive bacterium, 29 (14.36%) gram-negative bacteria, 4 (1.98%) fungus and 8 (3.96%) mixed infection. Another 42 (20.79%) patients were negative for bacterial culture. The culture-positive rates of patients with acute PJI, delayed PJI and chronic PJI were 72.00% (18/25), 79.12% (72/91) and 81.40% (70/86), there was no significant difference (χ²= 1.039, P=0.595).
Gram-positive bacteria were the main pathogens of PJI (58.91%, 119/202). Staphylococcus epidermidis was the most common gram-positive bacteria (23.76%, 48/202), followed by Staphylococcus aureus (16.34%, 33/202). The positive rates of gram-positive bacteria in acute PJI, delayed PJI and chronic PJI patients were 32.00% (8/25), 62.64% (57/91) and 62.79% (54/86), respectively. There was a statistical difference among the groups(χ²=8.356, P=0.014) (Table 2).
The positive rate of gram-negative bacteria was 14.36% (29/202). The main pathogens of gram-negative bacteria were Escherichia coli (7.43%, 15/202), followed by Klebsiella pneumoniae (2.48%, 5/202). The detection rates of gram-negative bacteria in acute, delayed and chronic PJI patients were 32% (8/25), 10.99% (10/91) and 12.79% (11/86), respectively. There were statistical differences among the groups (χ²=7.340, P=0.026). Only 4 (1.98%, 4/202) cases of delayed PJI group were cultured with fungi, and the other two groups were not isolated with fungus. Two pathogens were isolated from 8 cases of mixed pathogen infection (3.96%, 8/202). In the acute PJI group, there were 2 cases of mixed infection (Staphylococcus warneri and Candida parapsilosis, Klebsiella pneumoniae and Enterococcus faecalis). In the delayed PJI group, there were 1 case of mixed infection (Streptococcus and Bacterium burgeri). In the chronic PJI group, there were 5 cases of mixed infection (Staphylococcus aureus and Enterobacter cloacae; Staphylococcus aureus and Baumanii; Enterococcus faecalis and Enterobacter cloacae; Staphylococcus epidermidis and Candida parapsilosis; Staphylococcus epidermidis and Enterobacter cloacae) (Table 3).
Table 2 Bacterial culture results
Groups
|
Acute PJI
|
Delayed PJI
|
Chronic PJI
|
Culture Results
|
n
|
percentage
|
n
|
percentage
|
n
|
percentage
|
Gram-positive bacterium
|
8
|
32.00%
|
57
|
62.64%
|
54
|
62.79%
|
Gram-negative bacterium
|
8
|
32.00%
|
10
|
10.99%
|
11
|
12.79%
|
Fungus
|
0
|
0.00%
|
4
|
4.40%
|
0
|
0.00%
|
Mixed infection
|
2
|
8.00%
|
1
|
1.10%
|
5
|
5.81%
|
Negative
|
7
|
28.00%
|
19
|
20.88%
|
16
|
18.60%
|
Table 3 Microbiologic culture details
Groups
|
Acute PJI
|
Delayed PJI
|
Chronic PJI
|
Bacteria
|
n
|
percentage
|
n
|
percentage
|
n
|
percentage
|
Gram-positive bacterium
|
10
|
50.00%
|
58
|
79.45%
|
59
|
78.67%
|
Staphylococcus epidermidis
|
1
|
5.00%
|
24
|
32.88%
|
23
|
30.67%
|
Staphylococcus aureus
|
4
|
20.00%
|
17
|
23.29%
|
12
|
16.00%
|
Streptococcusa
|
0
|
0.00%
|
7
|
9.59%
|
7
|
9.33%
|
Enterococcus faecalis
|
1
|
5.00%
|
4
|
5.48%
|
1
|
1.33%
|
Enterococcus faecium
|
2
|
10.00%
|
1
|
1.37%
|
1
|
1.33%
|
Staphylococcus haemolyticus
|
1
|
5.00%
|
1
|
1.37%
|
3
|
4.00%
|
Staphylococcus warneri
|
1
|
5.00%
|
0
|
0.00%
|
0
|
0.00%
|
Staphylococcus simulans
|
0
|
0.00%
|
0
|
0.00%
|
1
|
1.33%
|
Staphylococcus lentus
|
0
|
0.00%
|
0
|
0.00%
|
1
|
1.33%
|
Staphylococcus hominis
|
0
|
0.00%
|
1
|
1.37%
|
5
|
6.67%
|
Staphylococcus capitis
|
0
|
0.00%
|
0
|
0.00%
|
1
|
1.33%
|
Other Gram-positive bacteriab
|
0
|
0.00%
|
3
|
4.11%
|
4
|
5.33%
|
Gram-negative bacterium
|
9
|
45.00%
|
11
|
15.07%
|
15
|
20.00%
|
Escherichia coli
|
4
|
20.00%
|
5
|
6.85%
|
6
|
8.00%
|
Klebsiella pneumoniae
|
4
|
20.00%
|
1
|
1.37%
|
0
|
0.00%
|
Pseudomonas aeruginosa
|
0
|
0.00%
|
0
|
0.00%
|
3
|
4.00%
|
Baumanii
|
0
|
0.00%
|
0
|
0.00%
|
1
|
1.33%
|
Serratia marcescens
|
0
|
0.00%
|
1
|
1.37%
|
0
|
0.00%
|
Enteroaerogen
|
0
|
0.00%
|
2
|
2.74%
|
0
|
0.00%
|
Enterobacter cloacae
|
1
|
5.00%
|
1
|
1.37%
|
3
|
4.00%
|
Other gram-negative bacteriac
|
0
|
0.00%
|
1
|
1.37%
|
2
|
2.67%
|
Fungus
|
1
|
5.00%
|
4
|
5.48%
|
1
|
1.33%
|
Candida parapsilosis
|
1
|
5.00%
|
4
|
5.48%
|
1
|
1.33%
|
a Streptococcus:Streptococcus pyogenes; Streptococcus intermedius; Streptococcus agalactiae; Streptococcus sanguis; Streptococcus lactis; Streptococcus pharyngitis; Streptococcus pneumoniae; Streptococcus viridis. b Other Gram-positive bacteria: Fengella Magna; Corynebacterium kroppensteiter; Micromonospora; Bacillus cereus; Streptococcus granulosus; Corynebacterium striatum. c Other gram-negative bacteria: Xanthomonas campestris; Burkholderia cepacia; Bacterium burgeri
Drug Resistance
Drug sensitivity for gram-positive bacteria
The drug-resistance rate is an essential factor in the diagnosis and treatment of PJI, which has a great impact on the decision-making of surgeons to use antibiotics. Penicillins, oxacillin and erythromycin showed high drug-resistance rates (Table 4). Among penicillins, 91 of 112 strains (81.25%) showed penicillin resistance, while 57 of 90 strains (63.33%) showed oxacillin resistance. The drug-resistance rates of erythromycin and clindamycin were also high (61.17% and 48.35%, respectively). Of 48 strains of Staphylococcus epidermidis and 33 strains of Staphylococcus aureus observed, almost all of them were resistant to penicillin and erythromycin. At the same time, about half of the patients were resistant to clindamycin, and one-quarter of them were resistant to ciprofloxacin. Among the 48 strains Staphylococcus epidermidis, 34 strains were methicillin-resistant coagulase-negative staphylococci (MRSCoN) and 15 strains of methicillin-resistant staphylococcus aureus (MRSA) were isolated from 33 strains of Staphylococcus aureus. Six strains of Enterococcus faecalis and 4 strain of Enterococcus faecium were detected. All Enterococcus faecalis and Streptococcus were sensitive to penicillin, but all Enterococcus faecalis were resistant to penicillin. No vancomycin-resistant, linezolid-resistant, daptomycin-resistant and tigecycline-resistant gram-positive bacteria were found.
Drug sensitivity for gram-negative bacteria
Ticacillin/clavulanate, amoxicillin/clavulanate, cefazolin, cefuroxime, ceftriaxone, cefoxitin, tobramycin, gentamicin, ciprofloxacin, nitrofurantoin and cotrimoxazole showed high drug-resistance rates (Table 4). 7 of 15 strains Escherichia coli and 3 of 5 Klebsiella pneumoniae were extended spectrum beta-lactamases (ESBLs). No amikacin-resistant, tigecycline-resistant, meropenem-resistant and polymyxin B-resistant gram-negative bacteria were found. We discovered 1 strain of imipenem-resistant Baumanii.
Table 4 Drug resistance of each strain
Gram-positive bacterium
|
Gram-negative bacterium
|
Drugs
|
Drug-resistant strain
|
Total number
|
Percentage
|
Drugs
|
Drug-resistant strain
|
Total number
|
Percentage
|
Penicillins
|
|
|
|
β-lactams/ β-lactamase inhibitor
|
|
|
Penicillin
|
91
|
112
|
81.25%
|
Ticacillin/clavulanate
|
2
|
3
|
66.67%
|
Oxacillin
|
57
|
90
|
63.33%
|
Piperacillin/Tazobactam
|
2
|
27
|
7.41%
|
Ampicillin
|
4
|
25
|
16.00%
|
Amoxicillin/clavulanate
|
7
|
15
|
46.67%
|
Cephalosporins
|
|
|
|
Cefoperazone/Sulbactam
|
3
|
22
|
13.64%
|
Ceftaroline
|
0
|
33
|
0.00%
|
Cephalosporins
|
|
|
|
Aminoglycoside
|
|
|
|
Cefazolin
|
5
|
5
|
100.00%
|
Gentamicin
|
22
|
94
|
23.40%
|
Cefuroxime
|
14
|
19
|
73.68%
|
Tetracyclines
|
|
|
|
Ceftriaxone
|
15
|
23
|
65.22%
|
Tetracyclines
|
4
|
9
|
44.44%
|
Ceftazidime
|
8
|
27
|
29.63%
|
Tigecycline
|
0
|
113
|
0.00%
|
Cefepime
|
8
|
28
|
28.57%
|
Macrolides
|
|
|
|
Cephamycins
|
|
|
|
Erythromycin
|
63
|
103
|
61.17%
|
Cefoxitin
|
8
|
18
|
44.44%
|
Lincosamides
|
|
|
|
Aminoglycoside
|
|
|
|
Clindamycin
|
44
|
91
|
48.35%
|
Amikacin
|
0
|
26
|
0.00%
|
Polypeptide
|
|
|
|
Tobramycin
|
4
|
8
|
50.00%
|
Vancomycin
|
0
|
115
|
0.00%
|
Monobactams
|
|
|
|
Teicoplanin
|
4
|
93
|
4.30%
|
Aztreonam
|
2
|
6
|
33.33%
|
Daptomycin
|
0
|
87
|
0.00%
|
Aminoglycoside
|
|
|
|
Fluoroquinolone
|
|
|
|
Gentamicin
|
5
|
6
|
83.33%
|
Levofloxacin
|
23
|
102
|
22.55%
|
Tetracyclines
|
|
|
|
Moxifloxacin
|
19
|
92
|
20.65%
|
Tigecycline
|
0
|
18
|
0.00%
|
Antituberculotic
|
|
|
|
Fluoroquinolone
|
|
|
|
Rifampicin
|
11
|
88
|
12.50%
|
Levofloxacin
|
9
|
27
|
33.33%
|
Others
|
|
|
|
Ciprofloxacin
|
5
|
9
|
55.56%
|
Nitrofurantoin
|
0
|
10
|
0.00%
|
Carbapenems
|
|
|
|
Cotrimoxazole
|
24
|
91
|
26.37%
|
Imipenem
|
1
|
28
|
3.57%
|
Linezolid
|
0
|
115
|
0.00%
|
Meropenem
|
|
27
|
0.00%
|
|
|
|
|
Polypeptide
|
|
|
|
|
|
|
|
Polymyxin B
|
0
|
3
|
0.00%
|
|
|
|
|
Others
|
|
|
|
|
|
|
|
Nitrofurantoin
|
5
|
6
|
83.33%
|
|
|
|
|
Cotrimoxazole
|
12
|
25
|
48.00%
|