bacteria which are difficult or impossible to treat with existing medicines such as

methicillin-resistant S. aureus (MRSA), S. aureus resistant to vancomycin, and

extremely drug-resistant tuberculosis (Arguaete et al. 2013).

For bacteria, several mechanisms of resistance have evolved, including decreased

membrane permeability (Delcour 2009), overexpression of specific efflux pumps

(Piddock 2006), development of the mechanisms to degrade or alter the conventional

antibiotic (Munita and Arias 2016), and biological differentiation of the antibiotic

target site (Blair et al. 2015; Poole 2002; Jayaraman 2009). On broadly AMR against

bacterial cell divided into two types: acquired (due to protein, enzyme, genetic and

physical change in bacterial cell) and intrinsic (natural type of resistance in which

bacteria retard the drug penetration through the cell wall and also modified the

target) (Cope and Cope 2013) (Fig. 27.1).

Moreover, another study revealed that resistance in bacteria was created by a

special

gene

in

bacteria

called

NDM-1

which

is

called

New

Delhi

metallo-β-lactamase-1. The bacteria which produce this NDM-1 have resistance to

β-lactams,

aminoglycosides,

and

fluoroquinolones

(Pitout

2010).

Bacteria

possessing just one of these resistance mechanisms can be treated through an

alternative class of antibiotic; however, it is becoming increasingly common for

single strains of bacteria to simultaneously possess the genes for more than one of

these resistance mechanisms.

Gravely, as antibiotics are becoming increasingly ineffective, the human popula-

tion is expected to lose its most powerful weapon against infectious diseases, taking

us back to the pre-antibiotics days, where minor wounds, injuries, and other sources

of infection, including routine surgery, could potentially be life-threatening. Obvi-

ously, microorganisms have challenged modern science, and the global mortality

rate is estimated to reach 10 million lives per year (i.e. one person in every 3 s) in

Fig. 27.1 Schematic representation of the bacterial resistance to the antibiotic

27

Antimicrobial Applications of Engineered Metal-Based Nanomaterials

497