Characteristics of study participants
During the study period from February to May 2019, 52 patients participated in the study. The age of the latter ranged from 5 to 79 years with a mean of 40.77 years. Patients were hospitalized for 3 and 22 days with a mean of 7.58 days. The characteristics of this population are summarized and presented in Table I.
Table I. Characteristics of study participants
Characteristics
|
Number
|
Frequency (%)
|
Sex
|
|
|
|
Men
|
37
|
71.15
|
|
Women
|
15
|
28.85
|
Type of surgery
|
|
|
|
Visceral
|
38
|
73.08
|
|
Orthopedic
|
14
|
26.92
|
Antibiotics administered
|
|
|
|
β-lactamine
|
43
|
82.69
|
|
|
Ampicillin
|
21
|
40.38
|
|
|
Ceftriaxone
|
29
|
55.77
|
|
|
Cefixime
|
9
|
17.31
|
|
|
Cefuroxime
|
2
|
3.85
|
|
|
Amoxicillin/Clavulanic Acid
|
4
|
7.69
|
|
|
Cloxacillin
|
1
|
1.92
|
|
Fluoroquinolone
|
15
|
28.85
|
|
|
Ciprofloxacin
|
15
|
28.85
|
|
Aminoside
|
17
|
32.69
|
|
|
Gentamicin
|
17
|
32.69
|
|
Nitro-5-imidazoles
|
46
|
88.46
|
|
|
Metronidazole
|
46
|
88.46
|
|
Macrolide
|
1
|
1.92
|
|
|
Clarithromycin
|
1
|
1.92
|
|
|
|
|
|
|
First of all, it appears that men accounted for almost 3/4 of the population. Similarly, visceral surgery was the most frequent type of surgery with a proportion of 3/4. Finally, the antibiotics most commonly administered to patients belonged to the families of nitro-5-imidazole and β-lactamines with proportions approximately equal to 4/5 and the antibiotics least administered to patients belonged to the family of macrolides with a proportion of 1/50.
Distribution of bacterial isolates
From admission to discharge from hospital, 104 samples were taken. From these analysis, 110 Staphylococcus isolates were obtained. Of these, 57 isolates were obtained at admission versus 53 at discharge. The distribution of Staphylococcus isolates is presented in Table II.
Table II. Distribution of Staphylococcus strains
|
Hospitalization
|
|
|
Admission
|
|
Discharge
|
|
|
Number
|
Frequency (%)
|
|
Number
|
Frequency (%)
|
Staphylococcus aureus
|
|
16
|
28.07
|
|
25
|
47.17
|
Coagulase negative Staphylococcus
|
|
41
|
71,93
|
|
28
|
52.83
|
The results presented in Table II show a significant variation between Staphylococcus aureus strains and coagulase negative Staphylococcus strains isolated at admission and those isolated at discharge. Indeed, at admission Staphylococcus aureus represented practically 1/4 of the strains of Staphylococcus compared to approximately 1/2 at discharge.
Antibiotic susceptibility profiles of Staphylococcus isolates
The susceptibility profile of Staphylococcus isolates obtained at admission and at discharge is presented in Table III.
Table III. Antibiotic susceptibility profiles of Staphylococcus isolates
|
nadmission (%)
|
ndischarge(%)
|
Chi-2
|
p-value
|
Cefoxitin
|
|
|
|
|
|
Susceptible
|
44(77.19)
|
14(26.42)
|
29.49
|
˂0.0001
|
|
Intermediate
|
2(3.51)
|
2(3.77)
|
|
Resistant
|
11(19.30)
|
37(69.81)
|
Gentamicin
|
|
|
|
|
|
Susceptible
|
52(91.23)
|
46(86.79)
|
0.56
|
0.4559
|
|
Intermediate
|
0(0.00)
|
0(0.00)
|
|
Resistant
|
5(8.77)
|
7(13.21)
|
Erythromycin
|
|
|
|
|
|
Susceptible
|
18(31.58)
|
19(35.85)
|
1.81
|
0.4051
|
|
Intermediate
|
9(15.79)
|
4(7.55)
|
|
Resistant
|
30(52.63)
|
30(56.60)
|
Clindamycin
|
|
|
|
|
|
Susceptible
|
21(36.84)
|
26(49.06)
|
1.67
|
0.1957
|
|
Intermediate
|
0(0.00)
|
0(0.00)
|
|
Resistant
|
36(63.16)
|
27(50.94)
|
Norfloxacin
|
|
|
|
|
|
Susceptible
|
52(91.23)
|
42(79.25)
|
3.17
|
0.0749
|
|
Intermediate
|
0(0.00)
|
0(0.00)
|
|
Resistant
|
5(8.77)
|
11(20.75)
|
Ciprofloxacin
|
|
|
|
|
|
Susceptible
|
53(92.98)
|
43(81.13)
|
3.47
|
0.0624
|
|
Intermediate
|
0(0.00)
|
0(0.00)
|
|
Resistant
|
4(7.02)
|
10(18.87)
|
Fusidic acid
|
|
|
|
|
|
Susceptible
|
10(17.54)
|
4(7.55)
|
2.47
|
0.1160
|
|
Intermediate
|
0(0.00)
|
0(0.00)
|
|
Resistant
|
47(82.46)
|
49(92.45)
|
Co-trimoxazole
|
|
|
|
|
|
Susceptible
|
19(33.33)
|
17(32.08)
|
0.02
|
0.9878
|
|
Intermediate
|
3(5.26)
|
3(5.66)
|
|
Resistant
|
35(61.41)
|
33(62.26)
|
Penicillin G
|
|
|
|
|
|
Susceptible
|
27(47.37)
|
3(5.66)
|
24.09
|
˂0.0001
|
|
Intermediate
|
0(0.00)
|
0(0.00)
|
|
Resistant
|
30(52.63)
|
50(94.34)
|
Oxacillin
|
|
|
|
|
|
Susceptible
|
43(75.44)
|
16(30.19)
|
22.61
|
˂0.0001
|
|
Intermediate
|
0(0.00)
|
0(0.00)
|
|
Resistant
|
14(24.56)
|
37(69.81)
|
nadmission : number at admission ; ndischarge : number at discharge.
Table III shows that overall, the resistance rates obtained at discharge were higher than those obtained at admission. Significant and insignificant differences between the susceptibility profiles of the isolates obtained at admission and discharge were observed.
Significant differences were observed (p˂0.0001) for β-lactamines: cefoxitin, oxacillin and penicillin G in favour of a higher proportion of resistance to these antibiotics at discharge than at admission, resulting in resistance proportions respectively 4 times, 3 times and 2 times higher at discharge. In contrast, insignificant differences were mainly observed for fluoroquinolones (ciprofloxacin and norfloxacin with p=0.0624, p=0.0749 respectively) and cotrimoxazole (p=0.9878).
Distribution of methicillin-resistant Staphylococcus isolates
A systematic screening of methicillin-resistant Staphylococcus isolates was performed during the interpretive reading of the antibiotic susceptibility test. Overall 13 (25%) of patients were colonized by methicillin resistant Staphylococcus at admission versus 39 (75%) at discharge. The results of distribution of methicillin resistant Staphylococcus obtained at admission and at discharge are presented in Table IV.
Table IV. Distribution of methicillin-resistant Staphylococcus isolates
|
nadmission(%)
|
ndischarge(%)
|
Chi-2
|
p-value
|
Staphylococcus strains
|
|
|
|
|
|
MR+
|
14(24.56)
|
37(69.81)
|
22.61
|
˂0.0001
|
|
MR-
|
43(75.44)
|
16(30.19)
|
nadmission : number at admission; nsortie : number at discharge ; MR+: resistance to methicillin; MR- : no resistance to methicillin.
From Table IV, it appears that the proportion of methicillin-resistant Staphylococcus isolates obtained at discharge from hospital was almost three times that obtained at admission with a significant difference (p˂ 0,0001).
Research of the factors associated to colonization by MRS
In order to determine the factors associated to colonization by MRS, variables were identified and uni-variate analyses were first performed. Those who had presented a p≥ 0.20 were selected for the multi-variate analysis. The results of the latter are summarized and presented in Table V.
Table V. Research of factors associated to colonization by MRS
Variable
|
OR
|
OR 95%CI
|
p-value
|
|
|
Admission/discharge
|
|
|
|
|
|
Admission
|
1
|
|
Réf
|
|
|
Discharge
|
0.03
|
[2.36x10-3-0.40]
|
0.0080
|
|
Metronidazole
|
|
|
|
|
|
No
|
1
|
|
Réf
|
|
|
Yes
|
3.54
|
[0.56-22.46]
|
0.1797
|
|
Duration of hospilization
|
|
|
|
|
|
|
0.79
|
[0.65-0.96]
|
0.0185
|
|
Ampicillin
|
|
|
|
|
|
No
|
1
|
|
Réf
|
|
|
Yes
|
0.82
|
[0.19-3.50]
|
0.7879
|
|
Ceftriaxone
|
|
|
|
|
|
No
|
1
|
|
Réf
|
|
|
Yes
|
0.23
|
[0.04-1.18]
|
0.0788
|
|
Cefixime
|
|
|
|
|
|
No
|
1
|
|
Réf
|
|
|
Yes
|
10.24
|
[0.75-140.16]
|
0.0813
|
|
Type of surgery
|
|
|
|
|
|
Orthopaedic
|
1
|
|
Réf
|
|
|
Visceral
|
1.87
|
[0.55-6.39]
|
0.3149
|
|
Gentamicin
|
|
|
|
|
|
No
|
1
|
|
Réf
|
|
|
Yes
|
1.24
|
[0.30-5.03]
|
0.7684
|
|
It appears that in multi-variate analysis that hospitalization with an OR of 0.03 (95% CI; [2.36x10-3-0.40]) and hospitalization time with an OR of 0.79 (95% CI; [0.65-0.96]) remained significantly associated to colonization by MRS with p=0.0080 and p=0.0185 respectively.