The Relationship between Nasal Carriage of Staphylococcus aureus and Surgical Site Infections in a Hospital Center in Morocco

Background Surgical site infection is a major public health problem in the world. Nasal carriage is a major risk factor for the development of nosocomial Staphylococcus aureus infection, especially methicillin-resistant Staphylococcus aureus (MRSA). Our work aims to determine the prevalence of Staphylococcus aureus, methicillin-resistant Staphylococcus aureus, and the associated risk factors and to evaluate their sensitivity to 27 antibiotics. Methods A cross-sectional study was carried out on 100 patients, hospitalized in preoperative care of surgery units at the Taza Provincial Hospital Center in the Fez-Meknes region, from January to June 2019. Samples were taken from the patient's anterior nostril using single-use sterile dry or wet cotton swabs and then analyzed in the Provincial Public Health Laboratory in Taza. The carriage of Staphylococcus aureus was studied by conventional bacteriological methods by spreading nasal swabs on Chapman culture medium, while antibiotic resistance was determined by the Mueller–Hinton agar disc diffusion method according to the recommendations described by the Antibiogram Committee of the French Society of Microbiology 2019 (CA SFM 2019). Results Of the 84 patients found to be positive, 45.24% had coagulase-positive Staphylococcus aureus and 54.76% had coagulase-negative Staphylococcus. After surgery in the postoperative phase, 16 patients developed surgical site infections, of which two had a negative nasal culture and 14 had positive nasal culture. Among the Staphylococcus aureus-positive patients, 36.84% were colonized by a methicillin-resistant Staphylococcus aureus (MRSA) and 63.16% by a methicillin-sensitive Staphylococcus aureus (MSSA). Of these, 57.14% of MRSA colonized patients developed an infection of the surgical site and 42.85% showed no sign of SSI, while for patients colonized by MSSA, 16.67% developed SSI and 83.33% showed no sign of SSI. Moreover, children were the most affected by MRSA. Concerning antibiotic sensitivity, multiresistance of MRSA to more than 3 antibiotics has been found. Conclusion To the best of our knowledge, this is the first study carried out in this hospital center with the aim of knowing the prevalence of nasal carriage of Staphylococcus aureus and MRSA and to identify the risk factors in order to prevent infections related to nasal carriage of Staphylococcus aureus and MRSA.


Introduction
Surgical site infections (SSIs) are infections that occur after surgery, 30 days postoperatively or one year postoperatively for prosthetic surgery procedures. ese infections are classified as superficial, deep, organ, or space infections [1]. SSIs represent a concern for health systems because of their high mortality and morbidity rates, the increase in the average length of hospital stay, as well as expenses and costs, which increases the number of postoperative patients [2,3] and reduces the care quality and the hospital's branding. SSIs are the second nosocomial infection occuring in France after urinary tract infections [3] and pose a major public health problem in Africa due to their incidence varying between 6.8% and 26% [4]. Staphylococcus aureus remains the most common cause of infections in operating sites [5].
In humans, the anterior nostrils of the nose are the most common sites of carriage for Staphylococcus aureus (S. aureus), which remains a well-defined risk factor for infection with this bacterium [6,7]. In a previous study on the role of nasal carriage in S. aureus infections, it has been shown that there is an increase in carriage rates in extranasal sites for nasal S. aureus carriers, for example, skin carriage on the hands increases from 27% in normal population to 90% in permanent nasal S. aureus carriers [6], which present in surgery cases a higher risk of nosocomial S. aureus infection (bacteremia) compared to controls [8].
Nasal carriage of S. aureus creates a major risk of SSI in carrier's patients, some of whom have a greater risk by carrying methicillin-resistant Staphylococcus aureus (MRSA), which is an additional risk factor for surgical site infection and has become endemic in some hospital areas [9]. In addition, the ineffectiveness of antibiotic prophylaxis on MRSA strains increases the risk of SSI with MRSA in patients treated in surgical intensive care units [10] in Morocco, where little research has been done on this subject. To this end, the objective of our investigation is to study the nasal carriage of Staphylococcus aureus and non-aureus in preoperative patients in a provincial hospital center and to study the antibiotic resistance of all strains isolated in order to determine their relationship with postoperative patients' surgical site infection.

Study Population.
is is a cross-sectional prospective study which was conducted over a period of six months (January to June 2019) in a Provincial Hospital Center in Taza city (in Fez-Meknes region, in the northeast of Morocco). e study concerned patients hospitalized in preoperative care in the men's, women's, children's, and gynecological-obstetric surgery units. Concerning the inclusion criteria, patients hospitalized preoperatively, having benefited from a surgical intervention and being followed up postoperatively, were included in this study, while the patients who did not benefit from a surgical intervention were all excluded. e choice was made in an anarchic way according to patients who agreed to participate in the study.
Patients' medical records were reviewed and examined for demographic information: for information on the antibiotics prescription in the postoperative period and for the detection of surgical site infections.

Sampling
Mode. Samples were taken using single-use sterile dry or moist cotton swabs which were inserted into the patient's anterior nostril (1-2 cm). ereby, nasal secretions were collected by performing 5 complete rotations of the swab, the same swab being used for both nostrils [11]. Immediately after taking the samples, the swabs were sent directly in an isothermal box to the Provincial Public Health Laboratory in Taza, where they were spread on the Chapman medium and then incubated at 35°C (±2) for 24 to 48 hours.

Bacteriological Analysis.
e carrying of S. aureus was investigated by classical bacteriological methods by spreading nasal swabs on the Chapman culture medium (OXOÏD society). Colonies fermenting mannitol were suspected as Staphylococcus aureus; then, bacterial identification was based on morphological and biochemical characters: colonies appearance; mannitol's fermentation based on the strain's ability to use or not mannitol as carbon source; and DNAse positive, Gram positive, oxidase positive, and catalase negative activities. Hence, creamy colonies having a circular outline, a rounded shape, a smooth appearance, a convex elevation, and a viscous consistency are characteristic to S. aureus for which microscopic examination shows Gram-positive diplococci or cocci in regular clusters. Moreover, fermentation produces organic acids after sugar's degradation; the accumulation of these organic acids in the culture medium induces its acidification leading to a change of the phenol red (pH indicator) to yellow. Furthermore, DNase tests are conducted on a DNA agar medium, after 18 to 24 hours of incubation, the presence of a clear area around the streaks indicates the presence of DNase activity.
Finally, the strain's confirmation is carried out on an API® 20 Staph gallery (bioMérieux company) made up of 20 microtubes containing dehydrated substrates. e microtubes are inoculated with a bacterial suspension prepared on the API Staph medium. e reactions produced during the incubation period result in spontaneous color changes or are revealed by the addition of specific reagents; then, identification is made using the analytical catalog. e identified strains were stored at −18°C.

Statistical
Analysis. Data were analyzed using SPSS and Microsoft Office Excel 2010. e p values for the variables analyzed in each case were calculated by the Fisher's exact test and the chi 2 test, considering p value <0.001 as highly significant, p value <0.01 as very significant, and p value <0.05 as significant.

Results
For a total of 100 patients, 25% for each service, the mean age of 39 years (±1 year) and sex ratio of 1. 22 Figure 1).
Females have been the most carriers of S. aureus with a rate of 63.16%. Moreover, patients admitted to the programmed surgery are the most colonized by S. aureus with 20 cases (52.63%), as well as patients with no venous catheters and patients not presenting any associated pathology are the most affected by S. aureus.
Concerning specialties, gynecology has recorded the highest number of S. aureus infections, followed by pediatric surgery, orthopedic surgery, visceral surgery, and urology. However, these infections have been absent in otolaryngology surgery and neurosurgery. Otherwise, patients from rural areas have been the main carriers of S. aureus with a percentage of 65.78% compared to urban patients. For services, where operative site infection was developed, the children's surgeries service has ranked first with 5 cases (41.66%) followed by gynecology (3 cases) (25.00%) and then women's and men's surgeries having the same cases number (2 cases in each surgey unit corresponding to 16.67%) ( Table 1).
Regarding the regression analysis between S. aureus and patient characteristics (Table 1), the rate of S. aureus carriers has been found statistically insignificant in relation to services, age, sex, venous catheter, and pathologies associated with the specialty and origin (p > 0.05). However, a highly significant relationship has been noted between S. aureus carriers and surgical site infections, p � 0.007 (p < 0.01), odds ratio at the 95% confidence interval, OR � 4.2391 [1.3016; 15.3893], as well as a significant relationship between S. aureus carriers and the nature of admission to services, p � 0.01, odds ratio at the 95% confidence interval, OR � 3.0483 [1.181; 8.0862].
In relation to MRSA colonized patients (Table 2), the children's surgery department has the highest number of patients (5 cases (35.71%)), followed by men's surgery (4 cases (28.58%)), then gynecology (3 cases (21.43%)) and women's surgery (2 cases (14.28%)). Regarding the age group, most colonized with MRSA, it is under 15 years old (35.71%), while the carriers of MSSA are between 30 and 45 years old (37.50%). Moreover, females are the most affected by MRSA (64.29%), as well as patients admitted in emergency, venous catheter carriers, and also patients without associated pathologies. For the specialty, children's surgery is at the first level (with 5 cases of MRSA) followed by gynecology and orthopedic surgery (3 cases for each one), then visceral (2 cases), and urology (1 MRSA carrier case). Patients from rural areas are the most colonized by MRSA (78.57%). For the services affected by MRSA whose patients developed an SSI, child surgery (37.5%) is followed by gynecology and men's surgery (25%) and finally women's surgery (12.5%).
Concerning the patient's factors and S. aureus nasal porting status, a highly significant relation has been observed between S. aureus nasal porting and emergency admission mode (p � 0.01) and a highly significant relationship between nasal porting and surgical site infection (p < 0.01).  MRSA is one of the major multiresistant organisms and represents a major public health problem in the world [21]. In our study, the MRSA rate is 14% versus 24% of MSSA, and these results differ from those found elsewhere. In fact, it differs from one country to another according to the geographical area. Hence, a rate of 33.8% was reported in Iran [22], 1.2% in Turkey [23], 45.4% in Cameroon [24], 6.8% in Taiwan [25], 40% in Egypt [26], 53.4% in East Africa [27], and 3.4% in Japan [18]. In our study, MRSA is generally observed in patients who have recently been hospitalized and shows a significant relationship between MRSA nasal porting and the admission's mode (p < 0.05), which explains why patients admitted to emergency departments have a high risk of MRSA colonization.
In terms of age groups, children under 15 years have recorded a high number of MRSA, which is similar to other studies [28]. e highest MRSA carrier rate is recorded among female patients, which is contradictory to the results found at another hospital center in Morocco [9], where the MRSA carrier rate was higher in the child surgery department followed by the men surgery department. is proportion varies according to the department type and patients categories as well as according to the care type in the different departments.
For surgical site infections, a significant relationship between MRSA and surgical site infections (p < 0.05) has been found. is result is similar to those reported by different studies [18,29,30].
Regarding antibiotic susceptibility, MRSA isolates show high resistance to ceftazidime (85.72%), cefixime (78.58%), erythromycin (64.29%), Cefalotin (85.72%), piperacillin (78.58%), and teicoplanin (85.73%) which means multidrug resistance. Other studies in Morocco have shown that resistance to Erythromycin and the antibiotic resistance profile varies with geographical region and changes over time [31]. Our multidrug resistance result is consistent with other studies [32,33], which is explained by the antibiotics overuse on the one hand and by patients self-medication with antibiotics on the other hand.
Nasal carriage of S. aureus is a well-identified factor in patients undergoing surgical procedures in surgical departments; hence, it is necessary to eradicate. In this context, some scientific studies carried out showed firstly the effectiveness of a whole body wash with a 4% chlorhexidine solution for the eradication of the MRSA strains [34] and secondly the effectiveness of the antibiotic agent mupirocin [35] in reducing the surgical site infection [35]. Furthermore, the application of decontamination procedures in preoperative patients can be difficult, especially for emergency surgery, due to the time required for diagnosis (2 days for culture) and 3 days for treatment [30].
Despite some limitations of this study concerning mainly the investigation duration, as it was conducted over a period of six months, and the limited patients' numbers (25 patients for each department), which did not enable to differentiate permanent from intermittent nasal carriage in preoperative patients; it appears that nasal carriage of S. aureus significantly increases the rate of nosocomial surgical site infection (SSI) after surgery and is an independent risk factor for postoperative wound infections. erefore, regular examination is required for patients to reduce the number of spontaneous colonization of S. aureus and to minimize the risk of surgical site infection.

Conclusion
is study focuses on the nasal carriage of S. aureus and the importance of screening patients for MRSA. Results showed a significant relationship between MRSA and surgical site infections as well as the admission mode of patients to the hospital. Furthermore, in our study, children have been at greater risk of MRSA than other patients. Regarding antibiotic sensitivity, MRSA isolates have been found to develop multiresistance to antibiotics, which requires early detection of MRSA during patient admissions, decolonization of carrier patients, and control of antibiotic prescription in order to prevent nosocomial infections, especially SSI.

Data Availability
All data are available from the corresponding author upon kind request.

Ethical Approval
e study was ethically approved by the Fez-Meknes regional health steering committee. All information obtained from study subjects was coded to maintain confidentiality.

Consent
Consent was obtained from participants and guardians of the children prior to data collection

Conflicts of Interest
e authors declare no conflicts of interest.