Risk Factors for Surgical Site Infections in Elective and Emergency Surgeries: A Prospective Cohort Study

Abstract

Background

Surgical site infections (SSIs) cause morbidity, disabilities, and healthcare costs. This study aims to assess patient- and surgery-related factors influencing SSIs with standardized preoperative, operative, and postoperative care.

Methods

This prospective cohort study involved 140 patients undergoing elective or emergency surgeries at Al-Azhar University Hospitals, Egypt, from October 2020 to September 2021. Patients were stratified into two groups: emergency (Group A) and elective (Group B). Risk factors for SSIs were assessed through observational and analytical methods, focusing on adults aged 15 and older without prior infections. The chi-square test was utilized to assess the strength of associations for categorical variables. Statistical significance was determined at a p-value under 0.05, with a 95% confidence interval employed for all analyses. Data were tabulated using a spreadsheet and analyzed with IBM SPSS Statistics for Windows, Version 20.

Results

Among 140 patients, 25 developed SSIs (19 men, 6 women). Significant differences were found in wound type (P = 0.001, surgery type (P = 0.002), and operative time (P = 0.010). SSI risk was higher for dirty (45.8%), contaminated (31.3%), and clean-contaminated (12.9%) wounds. Prolonged operative times (≥60 minutes) increased SSI risk (57.9% vs. 40.6%, P = 0.010). Diabetic patients had a higher incidence. In emergency surgeries, E. coli, Staphylococcus aureus, and Pseudomonas aeruginosa predominated, while S. aureus and Citrobacter were more common in elective surgeries. Amikacin, metronidazole, azithromycin, and imipenem were effective antibiotics.

Conclusion

SSIs were more common in emergency surgeries. Risk factors included smoking, diabetes, wound contamination, and prolonged operative times. Effective antibiotic use and infection control measures can decrease SSI occurrence.

↑What is “already known” in this topic:

SSIs are influenced by patient variables (e.g., age, obesity, smoking, and diabetes) and procedure factors (e.g., surgery type, duration, and aseptic techniques). Elective surgeries have lower SSI rates due to better preparation, while emergency surgeries carry higher risks due to urgency and contamination. SSIs lead to elevated morbidity, greater costs, and longer stays, emphasizing the importance of infection control measures like timely antibiotics and proper wound care.

→What this article adds:

A detailed comparison of SSI risk factors specific to elective and emergency surgeries offers insights into how risks differ and why. Additionally, The use of a prospective cohort methodology provides stronger evidence that will contribute to the global data.

Introduction

It is projected that 2% of hospitalized patients will develop surgical site infections (SSIs). However, because postoperative discharge data are incomplete, this figure might not accurately reflect the actual incidence rate (1, 2).

Further evidence indicates that SSIs may develop during certain procedures at a frequency of 3% to 20%, with a possibly greater frequency in high-risk patients. As a result of severe tissue damage and poor wound healing, SSIs can cause significant morbidity and long-term disabilities, which raises the cost of healthcare and places a significant financial burden on society(3-5).

Despite some misconceptions among surgeons, an SSI is not a trivial condition with a benign course. SSI, as described by the Centers for Disease Control and Prevention (CDC), refers to an infection developing at the location of a surgical incision within 30 days after the process, typically characterized by inflammation or the presence of purulent discharge. The CDC classifies procedures into four categories—Classes I through IV—according to the risk of contamination associated with each procedure(6-8).

SSIs is influenced by both patient-specific factors and procedural variables. The kind of surgery performed and the clinical features of the patients influence the frequency of SSIs. The development of SSIs results from the combination of bacterial inoculation, microbial virulence, host defense mechanisms, and the surgical site microenvironment. Microorganisms are transferred into the incision site during the surgical intervention(9, 10).

During surgery, pathogenic microorganisms can enter the body from multiple external sources, such as the operating room environment, gloves, implants, surgical instruments, and drugs used in the method. The majority of these microorganisms are endogenous flora, naturally present in the patient's body(9).

The type of surgery and the healthcare setting. A study by Elzohairy et al. (2014) documented an SSI rate of around 15% in general surgery patients. Other studies report incidence rates ranging from 10% to 25%, varying by the type of surgical procedure, healthcare setting, and patient risk factors(10-12).

Several hospitals in Egypt have implemented infection prevention and control (IPC) programs in line with the World Health Organization (WHO) guidelines; despite these efforts, challenges remain in sustaining compliance with infection prevention and control measures due to resource limitations and variability in healthcare worker training. Therefore, research studies like this are essential to identify key areas for intervention and improve surgical outcomes (10-12).

The mission of the study is to recognize, assess, and analyze the risk variables contributing to SSIs and to explore effective preventive strategies to reduce their incidence.

The objectives of the study are to assess patient-related factors (e.g., age, gender, comorbidities, smoking), examine surgery-related factors (e.g., operative time, type of surgery, whether emergent or elective, and type of surgical wound), all within the context of standardized preoperative, operative, and postoperative care.

The objective of this research is to answer the subsequent question: What are the key risk factors contributing to SSIs?

Methods

This prospective cohort study was conducted on all surgical procedures related to general surgery and vascular surgeryperformed between October 2020 and September 2021. An overall total of 140 patients who were hospitalized for surgical processes (including both elective and emergency surgeries) were included in the research, which was carried out in the Departments of Surgery at Al-Azhar University Hospitals, Egypt, during this specific time period.

The study population was categorized into two groups in accordance with the kind of surgery:

• Group A (Emergency group): Comprising 70 patients who required emergency surgical procedures.

• Group B (Elective group): Comprising 70 patients who underwent elective surgical procedures.

Sampling techniques

Sampling frame: The sampling frame comprised patients scheduled for elective or emergency surgeries between October 2020 and September 2021 in the Department of Surgery at Al-Azhar University Hospital, New Damietta.

Sampling Method: A stratified sampling method was used according to the kind of surgery (elective vs. emergency):

Emergency surgery: Refers to surgeries that must be performed immediately or within 24 hours to save the patient's life, prevent serious complications, or preserve vital functions. These surgeries are typically unplanned.

Diabetes mellitus is identified as fasting blood sugar (FBS) > 120 mg/dL.

Anemia is identified as hemoglobin (Hb) < 12 g/dL in females and < 13 g/dL in males.

Hypertension is identified as diastolic blood pressure (DBP) ≥ 90 mmHg or systolic blood pressure (SBP) ≥ 140 mmHg.

Surgical Site Infections are categorized into organ/space infections, deep incisionals, and superficial incisionals, according to the depth of tissue involvement. SSIs are diagnosed within 30 days post-surgery and involve criteria such as purulent drainage, positive cultures, localized signs of infection (e.g., pain, redness, swelling, fever), wound dehiscence, or abscess formation identified clinically, radiologically, or during reoperation. Diagnosis may also rely on laboratory findings and the clinical judgment of the attending surgery doctors during the daily rounds in the department of surgery of our hospital.

Elective surgery: Refers to procedures planned in advance that do not require immediate intervention. These surgeries are usually performed for non-life-threatening conditions or to enhance the patient's life satisfaction and are scheduled according to the patient’s and surgeon’s availability.

Sample Size Calculation

The sample size was computed to be 140 utilizing Cochran’s sample size formula, with an estimated proportion of 2% (SSI rate of 0.02).

Inclusion criteria

Participants had to meet certain criteria: age 15 years or older and no history of infection at the surgical site prior to the study.

Exclusion criteria

Participants were omitted from the study if they met any of the subsequent circumstances: Individuals younger than 15 years, Late-onset SSI (happening more than 30 days post-surgery), Immunocompromised state or use of immunosuppressive medications, Undergoing repeat surgery, Surgeries involving the head, orthopedic procedures, obstetric and gynaecologic surgeries, or thoracic surgeries.

Prior to surgery, a comprehensive clinical assessment was conducted to establish the progression, onset, and period of symptoms, including rectal bleeding, abdominal lumps, constipation, vomiting, nausea, and abdominal distension. A physical examination was performed for each patient to evaluate vital parameters, including pulse rate and blood pressure. This assessment also included checking for abdominal guarding, rigidity, and tenderness.

An upright abdominal X-ray was performed to evaluate for the occurrence of foreign bodies, free gas under the diaphragm, and air-fluid levels. Abdominal ultrasonography was utilized to evaluate the status of the appendix, spleen, and liver; the presence and type of peritoneal fluid (e.g., hemoperitoneum or pyo-peritoneum); intestinal obstruction; abdominal masses; dilated bowel loops; and other relevant findings.

Intraoperatively, both superior and recurrent laryngeal nerves, as well as the parathyroid glands, were recognized and preserved in all cases. Suction drains were placed in all patients for a duration of 24 hours. Serum calcium levels were measured 24 hours postoperatively, and patients with levels below 8 mg/dL were classified as having hypocalcemia.

Operative time was identified as the total duration of a surgical procedure, typically measured from the moment the surgical incision is made to the time the incision is closed and surgical instruments are removed.

Follow-Up and Data Monitoring

Postoperative evaluation of the patients focused on identifying signs of surgical site infections (SSIs), including tenderness, discharge, swelling, erythema, and heightened temperature around the incision site. Systemic symptoms including purulent discharge, vomiting, nausea, and fever were also assessed.

All patients underwent postoperative care, and wound swabs were obtained for culture and sensitivity analysis for those who had SSIs. The sensitivity of the isolated pathogens to various antibiotics was also investigated to guide appropriate treatment. For patients presenting with systemic symptoms or clinical deterioration, additional investigations, including blood cultures and a complete blood count (CBC), were performed.

Wound dressings were applied periodically using a combination of hydrogen peroxide (H₂O₂) and povidone-iodine. The use of antibiotics was guided by the findings of the culture sensitivity results to ensure targeted and effective treatment.

Statistical analysis

The chi-square test was applied to assess the strength of associations for categorical variables. A p-value under 0.05 was considered statistically significant, with a 95% confidence interval employed for all analyses. Data were tabulated using a spreadsheet and processed with IBM SPSS Statistics for Windows, Version 20.

Results

Altogether, 140 patients participated in this research, equally divided between the emergency and elective groups (70 patients in each group). Out of these, 91 patients (65%) were male, with 46 in the emergency group and 28 in the elective group. The remaining 49 patients (35%) were female, with 21 in the emergency group and 42 in the elective group (Table 1).

Table 1. Attributes of the study’s participants.

Risk factors		Total number (emergency & elective groups N= 140		Emergency group n=70	Elective group n=70
		N	%	N	N
Age groups (Years)	15–25 ref	21	15	16	5
	26–35	37	26.4	18	19
	36–45	27	19.3	12	15
	46–55	23	16.4	14	9
	56–65	22	15.7	6	16
	>65	10	7.2	4	6
Gender	Male	91	65	49	28
	Female	49	35	21	42
Smoking	Yes	35	25	25	10
	No	105	75	45	60
Co-morbidities	Yes	65	46.4	33	32
	No	75	53.6	37	38
Kind of the wound	Clean	38	27.1	0	38
	Clean Contaminated	62	44.3	30	32
	Contaminated	16	11.4	16	0
	Dirty	24	17.2	24	0
Operative time	< 60 Minutes	64	40.6	26	38
	≥ 60 Minutes	76	57.9	44	32

The total number of smokers in the study was 35 patients (25%), while 105 patients (75%) were non-smokers. Co-morbidities were present in 65 patients (46.4%), whereas 75 patients (53.6%) had no co-morbidities (Table 1).

Regarding the type of surgical wound operated upon, there were 24 dirty wounds, 16 contaminated wounds, 62 clean-contaminated wounds, and 38 clean wounds (Table 1).

In terms of operative time, 64 patients (40.6%) had an operative time of less than 60 minutes, while 76 patients (57.9%) had an operative time of 60 minutes or more (Table 1).

Table 2 showed no statistically notable distinctions in the incidence of SSIs among age groups, males and females, smokers and non-smokers, or between patients with and without co-morbidities. However, a statistically notable distinction was noted concerning the type of surgical wound operated upon (P = 0.001), kind of surgery (emergency vs. elective) (P = 0.002), and operative time (P = 0.010).

Table 2. Risk factors and their Association with SSI.

Risk factors		Total number (emergency and& elective groups) N= 140
		N	SSIs	%		P-value
Age groups (Years)	15–25 ref	21	3		14.3
	26–35	37	8		21.6
	36–45	27	3		11.1	0.890
	46–55	23	5		21.7
	56–65	22	4		17.4
	>65	10	2		20
Gender	Male	91	19		20.9
	Female	49	6		12.2	0.102
Smoking	Yes	35	6		17.1
	No	105	19		18.1	0.450
Co-morbidities	Yes	65	12		18.5
	No	75	13		17.3	0.430
Kind of the wound	Clean	38	1		2.6
	Clean Contaminated	62	8		12.9
	Contaminated	16	5		31.3	0.001*
	Dirty	24	11		45.8
Kind of surgery	Emergency	70	19		50	0.002*
	Elective	70	6		50
Operative time	< 60 Minutes	64	26		40.6
	≥ 60 Minutes	76	44		57.9	0.010 *
Total		140	25		17.8%

* Significant association with a significant level of 5%.

The association between the type of surgical wound and the incidence of SSIs was direct: the more contaminated the wound class, the elevated the risk of infection. SSI incidence rates were 45.8%, 31.3%, 12.9%, and 2.6% for dirty, contaminated, clean-contaminated, and clean wounds, respectively (Table 2).

Operative time was found to be a substantial risk factor for SSIs. The longer the operative time, the higher the risk of infection. SSI incidence was 40.6% for surgeries lasting less than 60 minutes and 57.9% for surgeries lasting 60 minutes or more (P = 0.010).

Table 3 demonstrated a statistically notable distinction in the occurrence of SSIs among diabetic and non-diabetic patients.

Table 3. Co-morbidities and their Association with SSI.

Risk factors		Total number (emergency&elective groups) N= 140
		N	SSIs	%	P-value
Diabetes mellitus	Yes	19	6	31.6
	No	121	19	15.7	0.040*
Anemias	Yes	8	2	25
	No	132	23	17.4	0.290
Hypertension	Yes	27	3	11.1
	No	113	22	19.5	0.150
Respiratory disease	Yes	11	1	9.1	0.200
	No	129	24	18.6

Regarding the distribution of SSIs across various risk factors in emergency versus elective surgeries, there was a significant difference observed in males, non-smokers, co-morbid patients, and certain age groups. The lack of statistical significance for other risk factors between emergency and elective surgeries may be attributed to the comparatively small sample size (Table 4).

Table 4. SSI distribution for various risk factors in both elective versus emergency surgeries.

Risk factors		Emergency group n= 70			Elective group n=70
		nSSI		n	SSI	P-value
Age groups (Years)	15–25 ref	16	3	5	0	***
	26–35	18	6	19	2	0.040*
	36–45	12	3	15	0	***
	46–55	14	4	9	1	0.080*
	56–65	6	2	16	2	0.120
	>65	4	1	6	1	0.370
Gender	Male	49	17	42	2	0.001*
	Female	21	2	28	4	0.300
Smoking	Yes	25	4	10		0.300
	No	45	15	60	5	0.001*
Co-morbidities	Yes	3	9	2	3	0.030*
	No	37	11	38	3	0.007*
Kind of the wound	Clean	0	0	38	1	**
	Clean contaminated	30	3	32	5	0.250
	Contaminated	16	5	0	0	***
	Dirt	24	11	0	0	***
Operative time	< 60 Minutes	26	6	38	0	***
	≥ 60 Minutes	44	13	32	6	0.140

* Significant association with a significant level of 5%.

According to Table 5, the most commonly isolated organisms from postoperative wounds in the emergency group were Staphylococcus aureus, Escherichia coli, and Pseudomonas, which accounted for 38%, 50%, and 12% of cases, respectively. Following emergency surgery, 41% of patients experienced tachycardia, 21% had a fever, 11% exhibited pain, 11% had redness or edema, 9 % had swelling, and 34% had discharge, according to the study.

Table 5. The distribution of organisms in infected postoperative wounds and the clinical assessment for SSI evaluation in the two groups.

Organism	Both emergency & elective groups N= 140		Emergency group N=70		Elective group N=70
	N		N (%)		N (%)
Escherichia coli		8 (40%)		8 (50%)		0 (0.0%)
Staphylococcusaureus		9 (45%)		6 (38%)		3 (75%)
Pseudomonas		2 (10%)		2 (12%)		0 (0.0%)
Citrobacter		1 (5%)		0 (0.0%)		1 (25%)
Total		20 (11 gram -ve and 9 gram+ve		16		4
Examination (general/local)		Both emergency & elective groups N= 140		Emergency group N=70		Elective group N=70
		N		N (%)		N (%)
Tachycardia		25		29 (41%)		6 (9%)
Fever		19		15 (21%)		4 (6%)
Pain		12		8 (11%)		4 (6%)
Redness/edema		11		8 (11%)		3 (4%)
Swelling		10		6 (9%)		4 (6%)
Discharge		28		24 (34%)		4 (6%)

In the elective surgery group, S. aureus was the most common organism (75%), succeeded by Citrobacter (25%). Of the isolates, 45% were gram-positive bacteria, and 50% were gram-negative bacteria. Additionally, 6% of patients undergoing elective surgery reported fever, pain, swelling, and discharge, while 9% reported tachycardia, and 4% had redness or edema.

The two antibiotics that were most commonly effective against E. coli were amikacin and metronidazole, with amikacin being the most frequently sensitive (Table 6). The two antibiotics most effective against S. aureus were azithromycin and amikacin. Tobramycin was effective against Citrobacter, while both imipenem and tobramycin were effective against Pseudomonas (Table 6).

Table 6. Sensitivity to antibiotics in various organisms.

Antibiotic	Organism
	Citrobacter	Pseudomonas	Staphylococcusaureus	Escherichia coli
Tetracyclin Ciprofloxacin	0	0	1	0
	0	0	2	0
Tobramycin	0	2	0	0
Moxifloxacin	0	2	0	0
Imepenem	0	0	0	0
Meropenem	1	0	0	2
Ceftriaxone	0	0	0	3
Linezolid	0	0	3	0
Azithromycin	0	0	6	2
Metronidazole	0	0	2	5
Amikacin	0	0	5	7

Discussion

Despite numerous advancements in surgical techniques, sterilization, antimicrobial drugs, and asepsis, SSIs continue to be a significant issue across various surgical disciplines in hospital environments. These infections lead to higher surgical expenses, greater morbidity rates, and increased mortality. When a wound infection occurs, hospitalization costs nearly double for the associated procedure (5-8).

SSIs not only raise hospitalization costs but also increase the risk of antimicrobial resistance in patients. This resistance can spread to other patients in the community, affecting primary healthcare services. In addition to identifying the kinds of bacteria that cause SSIs and their patterns of antibiotic resistance, the purpose of this research is to examine the prevalence of SSIs in our setting and investigate the relationship between these bacteria and associated risk factors.

In our study, 140 patients were included, and 70 patients were included in each of the two emergency and elective surgeries. There was no statistically meaningful distinction in the incidence of SSIs across age groups, males and females, smokers and non-smokers, or between patients with and without co-morbidities. However, a statistically significant difference was observed with regard to the kind of surgery (emergency vs. elective) (P = 0.002), the kind of surgical wound operated upon (P = 0.0002), and operative time (P = 0.01).

In this study of elective surgeries, SSIs occurred in 15.6% of clean-contaminated cases (5 of 32) and 2.6% of clean cases (1 of 38). In emergency surgery, no SSIs were recorded in clean cases, as no clean cases were operated on. SSIs developed in 10% (three out of 30) of clean-contaminated cases, 31.3% (five out of 16) of contaminated cases, and 45.8% (eleven out of 24) of dirty cases.

In the emergency group, the overall incidence of SSIs was 38% (19 of 70 cases), whereas the elective group had an infection rate of 8.57% (6 of 70 cases). A statistically significant difference was observed with regard to the type of surgery (emergency vs. elective) (P = 0.002). Emergency procedures frequently involve contaminated or dirty wounds due to their urgent nature, limiting opportunities for adequate preparation. In contrast, elective surgeries allow for thorough preoperative planning, including optimization of patient health (e.g., controlling blood glucose in diabetics and encouraging smoking cessation) and adherence to sterilization protocols. Emergency surgeries, however, proceed without such preparations, significantly increasing the risk of infections. Additionally, patients experiencing emergency surgery often present with compromised physiological states, including shock, sepsis, or trauma, which impair immune responses and delay wound healing, further contributing to the heightened risk of SSIs (9-11).

In a study by El-Sayed et al. (2017) (12),the overall SSI rate was reported to be significantly higher in emergency surgeries relative to elective procedures, similar to our findings. In their research, the infection rate in emergency surgeries was found to be 40%, while elective surgeries experienced a reduced infection rate of around 10%. This aligns with the 38% infection rate in our emergency group and the 8.57% infection rate in the elective group. The study also highlighted that the most common risk factors for SSIs included the type of wound, surgical technique, and the patient's underlying health condition. Our findings similarly identified that emergency surgeries were often associated with contaminated or dirty wounds, which contributed to the increased infection rate.

The total infection rate in the current study was 17.8%, which aligns with infection rates documented in several prior studies, ranging from 6.1% to 38.7% (13-19). Reduced infection rates, varying from 2.8% to 19.4%, have been observed in other developed nations (16-19). SSIs continue to be among the most frequent infections acquired in healthcare settings, substantially affecting the mortality and morbidity rates of patients undergoing surgical procedures (20-23).

The included studies highlighted several major risk factors, including the type of surgical wound (P = 0.0002), type of surgery (emergency vs. elective) (P = 0.002), and operative time (P = 0.01). These findings align with other reports that link SSIs to procedure-related factors(21-23).

In numerous studies, the incidence of SSI in males was 29%, while in females it was 10% (22-28). Conversely, Khan et al. documented that women had a slightly greater rate of SSIs (14.79%) relative to men (14.35%) (23).

Male gender has been identified as an independent risk factor in several studies. This relationship is supported by the evidence that estrogens have been demonstrated to exert an anti-inflammatory effect in women, which may explain the lower incidence of SSIs in females. In contrast, androgens are thought to have a proinflammatory impact on wounds in men, potentially hindering the re-epithelialization process. Furthermore, this disparity may also be influenced by men’s health behaviors and wound care practices (29-30, 1).

In the existing research, the rate of SSIs was non-significantly elevated in males relative to females (20.9% vs. 12.2%, respectively), which aligns with findings from previous studies.

While some studies associate SSI with individuals older than 60 years (25), our research did not observe a statistically notable difference in SSIs across age groups.

As anticipated, our study found that diabetes is a well-known and documented comorbidity that influences the development of SSIs, with a significant association (P = 0.04). Diabetes has been demonstrated to be a significant risk factor in other studies, with wound infection potentially linked to the vascular and immunologic complications associated with diabetes (31-33).

Smoking, which affects tissue perfusion, coagulation, and capillary oxygen transfer, is generally accepted as a contributor to infections. Several studies have identified smoking as an independent risk factor; however, in our research, it was not found to be a substantial risk factor. This could be ascribed to the smaller sample size(30, 34, 35).

In a study from Egypt done by Ahmed et al. (2019), the impact of diabetes and smoking on SSIs was investigated. The results mirrored our own observations regarding diabetes, which was recognized as a major risk factor for SSIs in both elective and emergency surgeries(36).

Numerous studies have shown that the "dirty" or "infected" wound class is a major risk factor for SSIs when compared to other wound classes. This relationship is direct: the more infected the wound class, the greater the risk of infection (clean, clean-contaminated, contaminated, or dirty). This is to be expected, as a higher bacterial load increases the likelihood of developing an SSI (1, 32, 30, 37, 38-41).

This is consistent with our study, where the association between the type of surgical wound and the incidence of SSIs is direct: the more infected the wound class, the greater the risk of infection (dirty, 45.8%; contaminated, 31.3%; clean-contaminated, 12.9%; clean, 2.6%). Using a variety of criteria, many studies found that operating time was a significant risk factor. This relationship is explained by Long-term contact with environmental influences, case complexity, and the incidence of intraoperative complications (29, 30, 39-41).

In the present study, operative time was a notable risk factor for the incidence of SSIs. The longer the operative time, the higher the risk of infection. The incidence of SSIs was 40.6% for operative times < 60 minutes and 57.9% for operative times ≥ 60 minutes (P = 0.01).

Studies executed in India have shown SSI rates as elevated as 49.50%. A cross-sectional study conducted between 2005 and 2008, which included 34,426 cases and utilized data from the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP), demonstrated that 8.56% of the cases were contaminated, 6.7% were dirty, 49.7% were clean, and 35.0% were clean-contaminated. The superficial SSI rates for unclean, contaminated, clean-contaminated, and clean wounds were 5.16%, 4.75%, 3.94%, and 1.76%, respectively. Infections from deep incisions ranged from 0.54% to 2.1%, while space/organ infections ranged from 0.28% to 4.54%. The study also identified factors such as smoking, anemia, diabetes, and the period of surgery as being connected with a raised incidence of SSIs. In cases of contaminated, clean-contaminated, and clean wounds, Ortega et al. reported SSI rates of 10-17%, 3-11%, and 1-5%, respectively (9).

In this study, 20 wound infections were analyzed, with 11 caused by gram-negative organisms (55%) and nine by gram-positive organisms (45%). The organisms were cultured from postoperative wound swabs or collections. In emergency surgeries, Escherichia coli (E. coli) was the most prevalent organism (50%) among those cultured from postoperative wounds, followed by Staphylococcus aureus (S. aureus) (38%) and Pseudomonas aeruginosa (12%). In the elective group, S. aureus was the most common organism (75%), with Citrobacter being the second most prevalent organism (25%).

Globally, S. aureus remains the most frequently detected pathogen in SSIs, followed by Enterobacter species, E. coli, P. aeruginosa, and Enterococcus species. Additional pathogens implicated in SSIs include Candida albicans, Klebsiella pneumoniae, Proteus mirabilis, and various Streptococcus species. Our study's findings support this observation (10).

Based on the data from the National Nosocomial Infections Surveillance (NNIS) system (24), the distribution of pathogens in SSIs has not changed significantly over the past decade. Prevalent pathogens comprise coagulase-negative staphylococci, E. coli, S. aureus, and Enterococcus species. Antimicrobial-resistant pathogens, including Candida albicans and methicillin-resistant S. aureus (MRSA) are increasing in frequency, signaling a rising prevalence of SSIs caused by these resistant organisms(43).

The infection rate was significantly correlated with variables including the kind of wound, the period of the surgery, and whether the procedure was planned or an emergency. Gram-negative bacteria producing extended-spectrum β-lactamases, particularly E. coli, were the most commonly isolated organisms in patients with SSIs. This finding contrasts with earlier studies that observed a greater incidence of gram-positive bacteria, particularly coagulase-negative staphylococci and S. aureus (23).

According to Mangram et al (10), the primary pathogens in gastrointestinal SSIs include anaerobes (e.g., Bacteroides fragilis), gram-positive organisms (e.g., Enterococci), and gram-negative bacilli (e.g., E. coli). External factors contributing to SSIs, alongside endogenous sources, include materials introduced into the sterile field through surgery, surgical instruments, all tools, the operating room setting (e.g., air quality), and the surgical team.

Aerobes, particularly gram-positive bacteria like Staphylococci and Streptococci, constitute the majority of exogenous flora. Fungal infections, which may have either endogenous or exogenous origins, are rarely associated with SSIs. According to Amrutham et al. (11), S. aureus was the most commonly isolated organism from surgical sites, accounting for 53.33% of cases. Other bacterial isolates included Citrobacter (8.88%), Enterobacter (11.11%), Staphylococcus epidermidis (11.11%), Proteus (13.33%), E. coli (17.77%), Klebsiella pneumoniae (26.66%), and Pseudomonas aeruginosa (35.55%). Our study's findings support this observation.

In terms of pathogen distribution, our findings also align with previous studies from Egyptian hospitals, where Staphylococcus aureus and Escherichia coli were identified as the most common pathogens responsible for SSIs. This confirms the results of El-Masry et al. (2018), who documented a high prevalence of E. coli in emergency surgeries, particularly in contaminated and dirty wound categories. Their study further emphasized the importance of appropriate antibiotic prophylaxis and timely intervention to manage infections caused by such pathogens (44).

The majority of these isolates exhibited multidrug resistance(11).Amikacin demonstrated the highest sensitivity against E. coli, and metronidazole succeeded. Similarly, azithromycin was the most effective antibiotic against S. aureus, succeeded by amikacin.

This research has some limitations, including being conducted at a single center and involving a comparatively limited sample size. Future research with larger patient cohorts, investigations involving multiple centers, and systematic reviews or meta-analyses could additionally validate and strengthen the outcomes of this research.

Conclusion

Compared to elective procedures, SSIs are more frequently observed in emergency surgeries. Key risk factors for SSIs include smoking, diabetes mellitus, higher wound contamination levels, and prolonged operative times. Implementing an effective antibiotic policy and robust infection control measures can significantly reduce SSI incidence.

Ethical Considerations

The study received approval from and was reviewed by the Damietta Institutional Review Board, Faculty of Medicine, Al-Azhar University, Damietta, Egypt (Registration number: DFM-IRB 00012367-24-07-007).

Conflict of Interests

The authors declare that they have no competing interests.

Cite this article as : Megahed HA, Taki-Eldin A, Mohamed AA, El-Syed Ibrahim MKh, Abdel Aziz AA, Megahed HA, Zeen Farg MZ, Kandel AM, Alemam A, Salamh KM, Elmoursi LZ, Yousef A, El Wakel MF. Risk Factors for Surgical Site Infections in Elective and Emergency Surgeries: A Prospective Cohort Study. Med J Islam Repub Iran. 2025 (15 Apr);39:55. https://doi.org/10.47176/mjiri.39.55