INTRODUCTION
Nosocomial infections is one of the problems of hospital environments, which in addition to economic costs, sometimes prolongs the patient's hospitalization [1]. .... [2-10]. 90% of nosocomial infections are caused by bacteria; Klebsiella pneumoniae, Staphylococcus aureus, Pseudomonas and Proteus mirabilis are among the most important causes of nosocomial infections [10]. Prescribing antibiotics is the first way to treat the disease due to the important role of bacteria in causing nosocomial infections but the challenge in the treatment of these infections is the occurrence of antibiotic resistance [11]. Vancomycin is one of the antibiotics that is frequently used in the hospital environment, especially in the case of methicillin-resistant staphylococci. Although a few cases of vancomycin-resistant Staphylococcus aureus have been reported, with the emergence of resistance to vancomycin in enterococcus and the emergence of methicillin-resistant staphylococci with reduced sensitivity to vancomycin, the treatment problems of these bacteria have increased [12-14]. Excessive antibiotic consumption has caused this resistance. This consumption in Iran is 16 times the world standard and approximately equal to the entire Europe [15]. Timely recognition and diagnosis of antibiotic resistance, proper use of antibiotics to reduce the creation of drug resistance is one of the most important principles in any hospital which the results are effective in reducing patients' long -term hospitalization and reducing mortality and heavy economic costs for patients. Since the use of antibiotics in various infections has increased, examining antibiotic resistance is a research priority in each region.
AIM(s)
In this study, frequency and risk factors and antibiotic resistance of nosocomial infections caused by gram positive bacteria were investigated during 6 years in Mustafa Khomeini Hospital in Iran
RESEARCH TYPE
The present study is a retrospective cross -sectional and descriptive analytical study.
RESEARCH SOCIETY, PLACE & TIME
This study was conducted on patients with the diagnosis of nosocomial infection during the years 2014 to 2019 at Shahid Mustafa Khomeini Hospital in Tehran, Iran.
SAMPLING METHOD AND NUMBER
Based on the census sampling method, 263 patients were identified by diagnosing infection at the time of the study (4 people have two different nosocomial infections and 2 have a common nosocomial infection with different risk factors). Those whose nosocomial infection was not mentioned in their file were excluded from the study.
METHOD
The information required for each patient (based on the Clinical Guidebook of nosocomial Infection in Iran) in the information form including: age, gender, hospitalization department, performing invasive procedures (endotracheal intubation, cathetering, venous catheter, arterial catheter) culture samples, sensitivity and resistance to antibiotics, type of antibiotic, type of infection and type of bacteria were recorded. In the studied patients, drug sensitivity was determined by the disk diffusion method. The first step of this method includes the preparation of yeast suspension according to McFarland standard turbidity of 0.5. Dip a sterile swab in the suspension and after taking the excess liquid by pressing the swab against the inner wall of the tube, wet the swab on the surface of the 9 cm plate containing Mueller Hinton's medium that has already reached room temperature, 3 times completely at an angle of 60 degree and is uniformly inoculated on the surface of the plate. Then the plates are placed in a suitable place for 3 to 5 minutes (maximum 15 minutes) so that the excess liquid is absorbed and penetrates into the agar. In the next step, the antibiotic discs are removed by fine forceps, previously soaked in alcohol and then cooled with a sterile flame, and placed on the surface of the plate. The discs should be pressed briefly with the help of pliers. According to the McFarland standard, to transfer other discs, the forceps must be re-sterilized; because immediately after placing the discs, the antibiotic penetrates into the agar, therefore, discs should not be moved after they are placed on the environment. The plates are kept inverted for 24 hours at 35-37°C. After 24 hours, the plate is checked under the lamp and the diameter of the no growth halo is measured with a ruler and according to the table with the discs, the antibiogram test report is prepared as resistant, semi-sensitive and sensitive.
ETHICAL PERMISSION
This study was conducted after obtaining the code of ethics IR.SHAHED.REC.1399.147 from Shahed University.
STATISTICAL ANALYSIS
Data were analyzed using MedCalc 20 statistical software. Mean and standard deviation were used to describe quantitative variables with normal distribution, median and range were used for quantitative variables with non-normal distribution, number and percentage were used to describe qualitative variables. In order to measure the relationship between the demographic factors of patients and the risk factors of contracting enterococcus isolates, staphylococcus aureus isolates, and coagulase-negative staphylococcus isolates, logistic regression model was used with a type 1 error rate of 0.05.
FINDING by TEXT
In this study, 269 gram-positive cocci isolates from 263 patients were identified during 6 years (from April 2014 to March 2019). In total, 36% of nosocomial infections belonged to coagulase-negative Staphylococcus isolates, 33% to Staphylococcus aureus isolates, 25% to Enterococcus isolates, and 6% to other Gram-positive cocci isolates (Group A Streptococcus, Group B Streptococcus, Staphylococcus Saprophyticus, and Viridans Streptococcus). (Table 1). In this study, the sensitivity of antibiotics erythromycin, amikacin, piperacillin-tazobactam, cefoxitin, clindamycin, vancomycin, ampicillin, ampicillin-sulbactam, gentamicin, ciprofloxacin, chloramphenicol, cholestin, trimethoprim-sulfamethoxazole, linezolid, nitrofurantoin, meropenem, ofloxacin, cefepime was checked with cocci isolates Gram positive (Table 2). The logistic regression model was used to measure the relationship between demographic factors of patients and risk factors with Enterococcus isolate (p= 0.001, X²(7)= 41.67), Staphylococcus aureus isolate (p= 0.001, X²(8)= 42.12) and coagulase-negative Staphylococcus isolates (p=0.01, X²(8)= 18.48) were used. The results of this comparison showed that there was a significant and direct relationship between the inpatient department (special care to the normal department) and the underlying disease (having or not having an underlying disease) with the infection of Enterococcus isolate. Out of 263 patients, 209 had a urinary catheter and 147 had an endotracheal tube, 16 of the patients with a tracheal tube had this isolate, which were not included in the model to avoid errors (Tables 3 and 4). Also, there was a significant and direct relationship between the inpatient department (special care to the normal department) and the length of time the endotracheal tube remained with the infection of Staphylococcus aureus isolate. Also, there was a significant and direct relationship between the duration of hospitalization and coagulase-negative Staphylococcus isolates (Tables 5, 6, 7, 8).
MAIN COMPARISON to the SIMILAR STUDIES
The results of this study showed that the coagulase-negative Staphylococcus isolate ranked first with 36% infection. The most dangerous factor of this bacterium was the vascular catheter. Staphylococcus aureus ranked second with 33% of infections and the most common cause was endotracheal tube. Enterococcus isolates ranked third with 25% of cases, and the most common cause was urinary catheters. The best drugs affecting gram-positive cocci were vancomycin and ciprofloxacin, and the most resistance was seen in erythromycin, amikacin and clindamycin. High length of hospitalization and hospitalization department were effective risk factors. The results of the Asghar study, which was conducted in 2008-2009 titled “Prevalence and antibiotic sensitivity of Gram-positive bacteria in Mecca hospitals” are consistent with the results of the present study and show that ampicillin and erythromycin are resistant to streptococci [16]. The results of Mosadegh Rad's meta-analysis show that suction, tracheal tube, urinary catheter, history of surgery and ventilator were the most common causes of nosocomial infection in Iranian hospitals, and in this study, vascular catheter is known as the most important risk factor [17]. History of surgery and urinary catheter in Rahmanian's study constitute 20.9% and 20.3%, respectively, of the cause of nosocomial infection [18]. In the Bijari’s study, urinary catheter dislodgement, suction and endotracheal tube are known as the most important risk factors for nosocomial infections [19]. Ahmed Khan's study on 13 types of nosocomial infections shows that vancomycin has a high sensitivity on enterococcus of most gram-positive cocci infections, which was consistent with the present study [20]. In the study of Mossadegh Rad, Escherichia coli was the most common microorganism causing nosocomial infection, which can indicate its drug resistance to antibiotics. Pseudomonas, Staphylococcus and Klebsiella are in the next categories [17]. ... [21]. The study of Vahdat of Bushehr shows that ampicillin is 94% resistant in Staphylococcus aureus, Vancomycin is 11.7 resistant in Staphylococcus aureus, Gentamicin is 76.5% resistant in Staphylococcus aureus, Amikacin is 76.5% resistant in Staphylococcus aureus, Zoxim hardness is 59% resistant percentage was consistent with the present study and indicates the accuracy of antibiotic selection [22]. Zamanian's study also shows that Staphylococcus aureus has the highest resistance to amoxicillin, nalidixic acid, and penicillin, the lowest resistance to vancomycin, and the highest sensitivity to vancomycin, nitrofurantoin, amikacin, and co-trimoxazole, respectively; this difference in the results of different studies may be due to the difference in the sample size of the studies [23].
LIMITATIONS
The limitations of this study include the retrospective nature of the research and the insufficient accuracy of the information based on the files and also conducting this study in only one hospital.
SUGGESTIONS
Conducting similar studies in a multi-centered manner can most likely determine the pattern of antibiotic resistance at a higher level and based on that, it is possible to plan for the appropriate treatment of patients.
CONCLUSIONS
Coagulase-negative Staphylococci with 36 % has the most frequent and vascular catheter is the most risk factor in this bacterium. Staphylococcus aureus with 33 % infection in the second place and the Enterococcus isolate with 25 % infection.is in the third place. If the use of resistant antibiotics is limited and antibiotics sensitive to microorganisms are used as much as possible, the occurrence of more microbial resistances will be prevented. The insertion of various catheters, including urinary and vascular catheters can provide the basis for nosocomial infection and has been identified as a risk factor in various studies. Therefore, it is better to limit the use of catheters to very essential materials. According to the results of the study, the use of effective antibiotics according to the patient's antibiogram can be useful in improving the effectiveness of the treatment.
CLINICAL & PRACTICAL TIPS in POLICE MEDICINE
Given that gram -positive bacteria such as negative coagulase staphylococcus and staphylococcus aureus are very important pathogens in the hospital environment, including urban hospitals and field hospitals during war and natural crises. The use of effective antibiotics according to antibiogram is emphasized for better treatment, especially during war and crises. Equipping military centers laboratories with antibiogram kits, to quickly prepare samples to prescribe antibiotics selectively, will have better therapeutic results in the above conditions.
ACKNOWLEDGMENTS
The cooperation of the respected personnel of Mustafa Khomeini Hospital in completing this project is appreciated.
CONFLICT of INTEREST
The authors state that there is no conflict of interest in the present study.
FUNDING SOURCES
The project was carried out with the financial support of the Shahed University.

Table 1) frequency distribution of isolated samples of gram-positive cocci isolated from clinical samples