This book is written to present a brief overview of carbapenemases. The authors have enlightened the characteristic features, Genetic determinants, various phenotypic and molecular diagnostic procedures for detection of NBL. This book is the first effort from Pakistan which summarizes the prevalence scenario and diversity of Carbapenem variants worldwide and particularly in Pakistan. The book has mentioned the myths, pros and cons of various detection methodologies with their evolving trends according to Clinical Laboratory Standards Institute guidelines. We have covered evolution of microbial resistance which is greatly influenced by several intrinsic and extrinsic factors including hospital settings, laboratory setup, use and misuse of antibiotics and discovery of carbapenems, classification of carbapenemases, dissemination of carbapenemases through horizontal gene transfer, different criteria of classification, global occurrence of carbapenemases, carbapenemases in Pakistan. Moreover, we have discussed detection tests with their limitations including phenotypic tests which includes Imipenem (EDTA) synergy test:, Boronic acid tesr and Modified Hodge test. After that we have discussed several chromogenic media in detail for the detection of carbapenemase resistant strains. MALDI TOF MS technology is adapted in various clinical laboratories for the detection of carbapenemase resistance bacteria by detecting the carbapebemases activity. Accelerate diagnostics method which is a digital microscopy of halted alive bacteria found in broths of blood cultures are utilized identify both do susceptibility. Surpluses of reports about molecular identification tools to detect the CP genes have been published in scientific literature over the few past years. But only few of them are approved by FDA to use in diagnostic purpose, and the most of them are laboratory developed tests. PCR is applied on those cases where resistance is directly associated with genes expression level. Than we have discussed numerous pros and cons associated with any detection methods for studying confrontation mechanism in gram negative bacteria. Talking about genetic basis of Carbapenemase phenotype we have discussed Epidemiology of Carbapenems Resistant Bacteria in the globe and more specifically in our region with the distribution of different types of responsible enzymes. Genetic Basis of Carbapenemase Activity including Genetic Expression of Efflux Pumps, Genetic Suppression of Penicillin Binding Proteins, Inter-relationship of Carbapenems Resistance Mechanisms which results in such a phenotype is also discussed in details. We have also discussed several points regarding the Prevention of Carbapenems. After that we have discussed Current Scenario of Carbapenem Therapy in our hospital settings which might give us some clues regarding why this phenotype is spreading everywhere. After discussing problem we have moved towards the therapeutic options that we have left with which includes. The "antibiotic pipeline" has yielded an important new beta-lactam-beta lactamase inhibitor combination, Ceftazidime-Avibactam, which is gaining popularity now days. Polymixin B and colistin are the drug of choice for the MBL producing Gram negative bugs except those organism which are intrinsically resistant to colistin like Proteus species. Rifampicin itself is not used for treatment of Carbapenem resistant Gram negative rods due to rapid emergence of resistance. But in combination with colistin it is very effective and resistance development chances are also less in combination therapy. Different clinical trials have been conducted accessing the role of tigecycline in combination with other antimicrobials. Tigecycline-gentamicin and tigecycline-colistin combinations were proved to be more successful in clinical trials as compared to tigecycline alone. Fosfomycin in combination with colistin has proved to be a very good option against Carbapenem resistant negative bacteria.