The term nosocomial is derived from two Greek words: "komeion," which means "to take care of," and "nosus," which means "disease."  "Nosocomial" refer to any illness that a patient shrinks while receiving clinical attention. It is the infections that have become lodged in a medical facility and may have their origins in living things. When a patient receiving medical attention in a distant health care administrative centre or clinic develops "nosocomial" or "medical care associated infections," it is considered a medical emergency. It may occur during the patient's transfer to another hospital for another infection or even after they are released from care. In patients who are free of contaminations at the time of admission, it appears at least 48 hours following hospital admission. [1]. Nosocomial infections, often also known as "healthcare associated infections" (HCAI), manifest in a patient receiving medical attention in a hospital or other healthcare institution that was not present at the time of admission. These infections may develop both during the course of treating another illness and even after the patient is released from the hospital. They also include infections acquired through work among medical personnel [1]. These infections are linked to invasive medical devices used in contemporary healthcare, such as ventilators and catheters.[2].

In India, nosocomial infections occur in 10–20% of admitted patients [3]. ICUs continue to be the principal locations for healthcare-associated infections (HAIs), accounting for 25% of all hospital infections [4]. Staphylococcus aureus is the most frequent cause in a clinical setting [5]. The growing patient load in hospitals, coupled with inadequate sanitary procedures and circumstances, is a major contributing factor to the same [6]. One major avenue for the selective expansion of resistant bacteria resulting from acquired mutations is the treatment of bacterial illnesses, which is predominantly done with non-susceptible antibiotics without prior testing [5]. Recurrent infections in these patient groups are mostly caused by the severity of the disease and frequent exposure to treatment procedures among ICU patients. [7]. Research indicates that the emergence of more antimicrobial-resistant strains of neonatal illnesses is encouraged by nosocomial transmission, which is a leading cause of infant mortality in India. [8]. Although an external source is more frequent, an endogenous source can also cause an illness. Individuals with diabetes, intubation, drainage, and older populations with impaired immune systems are especially vulnerable [4, 6]. Among the common HAIs are still catheter-related UTIs, bloodstream infections linked to intravenous lines, and ventilator-associated pneumonia (VAP) [9].Long-term surgical procedures, nutritional deficiencies, cardiac cachexia, and hypothermia all contribute to this, which raises the estimated cost of therapy while also increasing the mortality rate [10]. As to the National Nosocomial Infections Surveillance System (NNIS), surgical site infections (SSI) rank third among the most frequently reported health-related illnesses in India. [11]. Immunocompromised organisms that are inherently non-pathogenic can occasionally manifest as HAI. Both epidemics and endemics can result in nosocomial infections [12]. It makes sense that illnesses contracted by medical staff are nosocomial [13]. Even though the ICU makes up fewer than 10% of all hospital beds, 20% of nosocomial infections happen there [4]. Varying ICUs and topographies have significantly varying rates and prevalence of nosocomial infections and resistance grades [14]. The burden of HAI has increased revenue-wise for low- and middle-income countries.[15–17]. Research indicates that lengthier stays in the intensive care unit due to HAI were linked to twice as high treatment expenditures [18]. Additionally, it is observed that one nosocomial infection affects 15 out of every 100 admitted patients, and that one in ten of these patients die [19]. This can be attributed to the necessity for more diagnostic testing, extended hospital stays, and expensive medications for infections that are resistant to several drugs [20]. Crude mortality from HAI is a significant contributor, accounting for 23.6% of cases [21]. Moreover, eliminating the HAI is not feasible; prevention, early detection, and control of spread set out to be the best measures.

2. Types of nosocomial infections

The  most  frequent  types  of  infections  include  central  line-associated  bloodstream  infections, catheter-associated  urinary  tract  infections,  surgical  site  infections  and  ventilator-associated  pneumonia.  A brief detail of these is given below:

2.1 Central line-associated bloodstream infections (CLABSI):

The fatal nosocomial illness known as CLABSIs has a death incidence rate ranging from 12% to 25% [8]. Central line catheters are used to provide medication and fluids, but long-term use can result in dangerous bloodstream infections, which can worsen health and raise medical expenses [9]. Despite a 46?cline in CLABSI in US hospitals between 2008 and 2013, an estimated 30,100 CLABSI still happen on ICU and acute care unit wards annually in the US. [10].

2.2. Catheter associated urinary tract infections (CAUTI):

The most common kind of nosocomial infection worldwide is CAUTI [11]. Acute care hospital statistics from 2011 show that over 12% of infections that are reported are UTIs [12]. Patients' endogenous natural microbiota is what causes CAUTIs. The placement of catheters inside the body allows bacteria to enter through the conduit, but the inadequate drainage from the catheter leaves some urine volume in the bladder, stabilising the bacterial residence [11]. For male patients, CAUTI can lead to complications such orchitis, epididymitis, and prostatitis; for all patients, it can cause pyelonephritis, cystitis, and meningitis. [12].

1. 3. Surgical  Site  Infections  (SSI):

Surgical site infections, or SSIs, affect 2-5% of patients after surgery. These are the second most prevalent kind of nosocomial infections, primarily brought on by Staphylococcus aureus, which increase the risk of death and lengthen hospital stays [13]. The patient's endogenous microflora is the source of the infections that cause SSI. The incidence could reach 20%, contingent on the method and surveillance standards applied. [14].

2.4 Ventilator  associated  pneumonia  (VAP):

Pneumonia and other respiratory or lung infections are often associated with the use of a ventilator and account for 22% of all HAIs. A ventilator assists the patient with breathing with tubes which enter the body via the mouth, nose, or incision in the throat. Germs can enter the ventilator and therefore be transported to the lung.

1. 4. Gastrointestinal tract infections:

The gastrointestinal tract is an organ system made up of all the organs responsible for                 digesting food and excreting waste. These organs are home to billions of naturally-occurring bacteria, including E. coli. When the healthy balance of these bacteria is upset (for example, by the use of antibiotics), or a foreign bacteria is introduced, infection can set in. GI infections lead to contaminated waste as the body tries to remove the infection in the form of vomit and diarrhea. This waste can lead to further contamination, especially if cleaning is not thorough and frequent.

3. Nosocomial Pathogenesis

3.1. Bacteria: The most well-known microorganisms that can cause nosocomial infections are bacteria. Some are related to the patient's natural flora and cause disease only when the patient's immune system becomes predisposed to illness. ICU diseases are caused by a class of pathogenic microorganisms called acinetobacter. It is present in 80% of reported contaminations in soil, water, and records. In the abdomen lies a commensal bacterium called Bacteroides fragilis. When combined with other germs, it might become contaminated. [3]. If Enterobacteriaceae are spread from the gut, where they are normally found, they can become a source of infections in other parts of the body. It is made up of Klebsiella species and Escherichia coli. Methicillin-resistant S. aureus (MRSA) spreads by hands contaminated with germs, open wounds, and direct contact. It begins with sepsis and pneumonia and spreads to other organs or the circulatory system. This has a high level of resistance to beta lactam antibiotics. The primary cause of Clostridium difficile-induced colon inflammation, colitis, and diarrhoea is the endosymbiotic bacteria that replace helpful microorganisms in the colon. Medical personnel handling infected patients can spread C. difficile to others by using improperly cleansed hands. [4, 5].

3.22. Viruses: A significant contributing factor to this infection, aside from bacteria, is infections. Regular investigation reveals that viruses are to blame for 5% of these diseases. They can exchange information by hand-mouth, respiratory, or fecal-oral routes. The persistent illness spread by this is hepatitis. Hepatitis infections are given and transferred to patients and labourers by therapeutic institutions. Risky infusion practices are typically used to spread hepatitis B and C. Other illnesses include the flu, rotavirus, HIV, and herpes simplex infection. [6, 7].

3.3. Fungal: It functions as an opportunistic bacterium that causes these infections in individuals with weakened immune systems. Aspergillus species have the ability to spread illnesses through ecological means. Candida albicans and Cryptococcus neoformans are also susceptible to infection during an emergency. Whereas Candida infections originate from the patient's own endogenous microbiota, Aspergillus contaminations are nearly entirely spread by inhaling parasite spores from contaminated air during construction or renovation of medical facilities. [8]

3.4. Parasites: It has been observed that parasites are the etiological agents of diarrhoea. Protozoa, such as Cryptosporidium sp., Entamoeba histolytica, Giardia lamblia, and Blastocystis, are typically responsible for contaminations. Food and water tainted with excrement can transmit protozoa that cause loose diarrhoea. One agent that may be responsible for watery nosocomial parasite illness is T. gondii. Transfusion-related nosocomial illness transmission is another plausible explanation. The Plasmodium species is the most well-known blood parasite that can spread by transfusion. It is occasionally possible to get nosocomial parasite infections from contaminated medical clinic equipment. There have been cases of injectors, contaminated gloves, and bedside glucometers spreading Plasmodium, a class of protozoans. It has also been reported that S. stercoralis has been transmitted from tainted endoscopes. [9].

4. Epidemiology of nosocomial infection: Numerous patients worldwide are impacted by nosocomial infections, which dramatically increase mortality rates and financial losses. About 15% of hospitalised patients had these illnesses, according to estimates provided by the WHO [23]. With an incidence rate of 75% in South-East Asia and Sub-Saharan Africa, these illnesses account for 4%–56% of all neonatal death causes [1]. In high-income nations, the incidence ranges from 3.5% to 12%, whereas in middle-class and low-income nations, it varies from 5.7% to 19.1%. While the incidence of infections in neonates is three to twenty times greater, the frequency of infections overall is three times higher in low-income nations than in high-income countries. [24].

5. Transmission

1. Contact transmission is divided into two subgroups: direct-contact transmission and indirect-contact transmission.

6. Determinants

The setting in which treatment is provided; the patient's state and vulnerability, and the staff's and healthcare professionals' ignorance of such prevalent infections are risk factors that determine nosocomial infections.

6.1 Environment

Poor  hygienic  conditions  and  inadequate  waste  disposal  from  health  care  settings.

1. 2. Susceptibility

Immunosuppressant  in  the  patients,  prolonged  stay  in  intensive  care  unit,  and  prolonged  use  of  antibiotic.

1. 3. Unawareness

Improper use  of  injection  techniques,  poor  knowledge  of  basic  infection  control  measures,  inappropriate  use  of  invasive devices  (catheters),  and,  lack  of  control  policies[25].  In  low  income  countries  these  risk  factors  are  associated  with  poverty, lack  of  financial  support,  understaffed  health  care  settings  and  inadequate  supply  of  equipments [5].

7. Prevention of nosocomial infection

Being  a  significant  cause  of  illness  and  death,  nosocomial  infections  need  to  be  prevented  from  the  base  line  so  that their  spread  can  be  controlled.

7.1Transmission from environment: An unclean atmosphere is the ideal setting for harmful organisms to proliferate. Food, drink, and the air can all become polluted and spread to people receiving medical care. Policies must be in place to guarantee that windows, doors, floors, beds, bathtubs, toilets, and other medical equipment are cleaned and cleaned with cleaning products. Airborne bacterial pollution can be removed using fresh, filtered air that is properly vented. It is necessary to maintain and record the regular inspection of the ventilation systems and filters in the general wards, surgical rooms, and intensive care units. The reason behind infections linked to water is that medical facilities don't satisfy the required standards. microbiological surveillanceTechniques ought to be applied while analysing water. Patients who are infected need to take separate baths. Food-borne illnesses can result from improper food handling practices. The meal should be of a standard that is met, and the area should be cleaned. [22].

7.2Transmission from staff:

Healthcare personnel may transmit infections to others. Healthcare workers have a responsibility to participate in infection control. Everybody needs to practise good personal hygiene; therefore employees should do the same. After coming into contact with sick people, one must properly decontaminate their hands with hand disinfectants. Sterilised equipment and safe injection techniques must to be employed. It is imperative for healthcare providers to wear masks, gloves, head coverings, or appropriate uniforms.[22]

7.3Hospital waste management:

Hospital waste presents a risk of harbouring germs and should be handled carefully. Hazardous waste makes around 10–25% of the garbage produced by healthcare facilities. Healthcare waste that is infectious should be kept in a location with limited access. Waste from surgeries, infected people, contaminated with blood and sputum, and diagnostic lab waste—all of which have a high concentration of heavy metals—must be disposed of separately. Cleaners and healthcare personnel should be made aware of the risks associated with trash and how to properly manage it.[22].

8. Control of nosocomial infection

There is a lack of actual statistics regarding the causes and antimicrobial susceptibility in developing countries. Pathogens with resistant organisms make it extremely difficult to devise a proper plan and its implementation for control [3].

8.1Measurement and comparison of infection rates: Measuring infection rates in various hospital settings is challenging. It is crucial to understand the kinds of microorganisms involved and their precise location within a person's body in order to measure infection rates. Because of their inherent heterogeneity, infectious organisms differ from one another. It is plausible that infection rates inside a hospital may exhibit similarities, albeit significant differences in the location and variability of organisms. Since infection rates differ between public and private hospitals, it is necessary to know the type of healthcare setting in order to compare the infection rates. Furthermore, there are significant differences in how infections are managed in various facilities.
       
           
       

8.2 Guidelines for control of nosocomial infection.