**2. Enterococcal infections and their treatments**

Over the past few decades, members of the genus *Enterococcus* have emerged as an important nosocomial pathogen causing different infections. Their transformation from gut commensal to pathogen is attributed by increasing antibiotic resistance especially resistance to vancomycin, high-level aminoglycosides (HLA), and penicillin is of interest. Moreover, resistance to new antimicrobial agents, like linezolid, quinupristin/dalfopristin, and daptomycin has also been emerged (**Figure 2**). Being more resistant than *E. fl*, *E. faecium* (*E. fm*) has come out to be the leading cause of multidrug resistant (MDR) infections in U.S. Because of its resistance to vancomycin, ampicillin and high-level aminoglycosides, infections caused by this species is very difficult to treat. According to National Healthcare Safety Network (NHSN) report, majority of device associated infections (for example, central lines infections, urinary drainage catheters infection and ventilator infections) were caused by 80% vancomycin and 90.4% ampicillin resistant *E. faecium* [8]. Other enterococcal species including *E. avium, E. casseliflavus, E. durans, E. hirae, E. raffinosus, E. gallinarum and E. mundtii* accounts for less human's infection [9]. Enterococci can cause variety of infections directly as sole cause of an infection or indirectly as a contributor in co-infection with other microorganisms [10] (**Figure 3**).

Enterococcal infections particularly those caused by vancomycin resistant enterococci (VRE) are associated with prolonged hospital stay and excess mortality. World Health Organization (WHO), in its report published in February 2017 placed Vancomycin Resistant *E. faecium* in the "HIGH PRIORITY category in global priority pathogens list (global PPL)" of antibiotic resistant bacteria to help in prioritizing

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**Figure 3.**

**Figure 2.**

*Examples of recently approved drugs.*

*The Genus* Enterococcus *and Its Associated Virulent Factors*

the research and development of new and effective antibiotic treatments [11, 12]. Earlier to this, VRE was also categorized as "microorganisms with a threat level of serious" with estimated 20,000 drugs resistant enterococcal infections, 1300 death

UTIs including prostatitis, epididymitis and cystitis are the most common types of infections caused by ENT. Majority of the patients includes older men as compared to young women. Upper UTIs which lead to bacteremia also occurred in young men [14]. According to a report presented to NHSN by center of disease control and prevention (CDC), *Enterococcus spp.* account for 14.9% of the total catheter associated UTIs between 2006 and 2007 [8]. Moreover, it is also reported

tolls and 66,000 *Enterococcus* infections per year in United States [13].

**2.1 Urinary tract infections (UTIs)**

*Different infections caused by genus* Enterococcus*.*

*DOI: http://dx.doi.org/10.5772/intechopen.89083*

#### **Figure 2.**

*Microorganisms*

**Figure 1.**

*Bacterial mobile genetic elements.*

chromosomal exchange as well as plasmid or transposon (**Figure 1**). This can lead to increment in dangerous nosocomial infections, thus limiting therapeutic options [6]. This is the reason for exploitation of this genus as an important key indicator

Over the past few decades, members of the genus *Enterococcus* have emerged as an important nosocomial pathogen causing different infections. Their transformation from gut commensal to pathogen is attributed by increasing antibiotic resistance especially resistance to vancomycin, high-level aminoglycosides (HLA), and penicillin is of interest. Moreover, resistance to new antimicrobial agents, like linezolid, quinupristin/dalfopristin, and daptomycin has also been emerged (**Figure 2**). Being more resistant than *E. fl*, *E. faecium* (*E. fm*) has come out to be the leading cause of multidrug resistant (MDR) infections in U.S. Because of its resistance to vancomycin, ampicillin and high-level aminoglycosides, infections caused by this species is very difficult to treat. According to National Healthcare Safety Network (NHSN) report, majority of device associated infections (for example, central lines infections, urinary drainage catheters infection and ventilator infections) were caused by 80% vancomycin and 90.4% ampicillin resistant *E. faecium* [8]. Other enterococcal species including *E. avium, E. casseliflavus, E. durans, E. hirae, E. raffinosus, E. gallinarum and E. mundtii* accounts for less human's infection [9]. Enterococci can cause variety of infections directly as sole cause of an infection or indirectly as a contributor in

Enterococcal infections particularly those caused by vancomycin resistant enterococci (VRE) are associated with prolonged hospital stay and excess mortality. World Health Organization (WHO), in its report published in February 2017 placed Vancomycin Resistant *E. faecium* in the "HIGH PRIORITY category in global priority pathogens list (global PPL)" of antibiotic resistant bacteria to help in prioritizing

bacterium for humans and veterinary resistance surveillance system [7].

**2. Enterococcal infections and their treatments**

co-infection with other microorganisms [10] (**Figure 3**).

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*Examples of recently approved drugs.*


#### **Figure 3.**

*Different infections caused by genus* Enterococcus*.*

the research and development of new and effective antibiotic treatments [11, 12]. Earlier to this, VRE was also categorized as "microorganisms with a threat level of serious" with estimated 20,000 drugs resistant enterococcal infections, 1300 death tolls and 66,000 *Enterococcus* infections per year in United States [13].
