Cases in Medical Microbiology and Infectious Diseases 4th Edition
It has been almost a decade since the 3rd edition of this text was published. Much has happened in the world of infectious diseases during this time. First, there has been recognition that the problems of infectious diseases are truly global and that infectious diseases in one part of the world can be quickly transmitted to another. Prime examples of this were the severe acute respiratory syndrome (SARS), the 2009 H1N1 influenza A virus outbreak, and multidrug-resistant Gram-negative bacilli (MDR-GNB). Genes for multidrug resistance can be carried on extrachromosomal genetic elements, facilitating the spread of these drug resistance determinants to highly virulent organisms such as was seen in the Shiga toxin-producing Escherichia coli (STEC) outbreak due to the O104 serotype in Germany in 2011. These emerging pathogens are literally a plane ride away, no matter where they are found globally, and can be disseminated worldwide in a matter of days to weeks.
MDR-GNB, environmental mycobacteria, and molds are emerging as important pathogens in the ever-expanding population of immunocompromised hosts. These organisms, although of comparatively low virulence when compared to highly adapted human pathogens such as Streptococcus pneumoniae or group A streptococci, have distinct characteristics that make them very worrisome. First, they have evolved over millions of years, adapting to harsh environments which contain antimicrobial molecules. As a result, organisms such as Acinetobacter baumannii, Mycobacterium abscessus group, and Fusarium spp. have high levels of intrinsic drug resistance. Additionally, they have comparatively large amounts of DNA, giving them a broad genetic repertoire which allows them to survive in hostile environments such as hospital surfaces and equipment. Finally, many MDR-GNBs are genetically promiscuous, taking up DNA which may contain resistance genes from other species or genera of bacteria. This promiscuity has led to a new concept in antimicrobial resistance, the “antimicrobial resistome,” which describes all the antimicrobial-resistant genes in a particular environment…