The definition of the heterogeneous group of coagulase-negative staphylococci (CoNS) is still based on diagnostic procedures that fulfill the clinical need to differentiate between Staphylococcus aureus and those staphylococci classified historically as being less or nonpathogenic. Due to patient- and procedure-related changes, CoNS now represent one of the major nosocomial pathogens, with S. epidermidis and S. haemolyticus being the most significant species. They account substantially for foreign body-related infections and infections in preterm newborns. While S. saprophyticus has been associated with acute urethritis, S. lugdunensis has a unique status, in some aspects resembling S. aureus in causing infectious endocarditis. In addition to CoNS found as food-associated saprophytes, many other CoNS species colonize the skin and mucous membranes of humans and animals and are less frequently involved in clinically manifested infections. This blurred gradation in terms of pathogenicity is reflected by species- and strain-specific virulence factors and the development of different host-defending strategies. Clearly, CoNS possess fewer virulence properties than S. aureus, with a respectively different disease spectrum. In this regard, host susceptibility is much more important. Therapeutically, CoNS are challenging due to the large proportion of methicillin-resistant strains and increasing numbers of isolates with less susceptibility to glycopeptides.

Coagulase-Negative Staphylococci

The human gut microbiota is engaged in multiple interactions affecting host health during the host's entire life span. Microbes colonize the neonatal gut immediately following birth. The establishment and interactive development of this early gut microbiota are believed to be (at least partially) driven and modulated by specific compounds present in human milk. It has been shown that certain genomes of infant gut commensals, in particular those of bifidobacterial species, are genetically adapted to utilize specific glycans of this human secretory fluid, thus representing a very intriguing example of host-microbe coevolution, where both partners are believed to benefit. In recent years, various metagenomic studies have tried to dissect the composition and functionality of the infant gut microbiome and to explore the distribution across the different ecological niches of the infant gut biogeography of the corresponding microbial consortia, including those corresponding to bacteria and viruses, in healthy and ill subjects. Such analyses have linked certain features of the microbiota/microbiome, such as reduced diversity or aberrant composition, to intestinal illnesses in infants or disease states that are manifested at later stages of life, including asthma, inflammatory bowel disease, and metabolic disorders. Thus, a growing number of studies have reported on how the early human gut microbiota composition/development may affect risk factors related to adult health conditions. This concept has fueled the development of strategies to shape the infant microbiota composition based on various functional food products. In this review, we describe the infant microbiota, the mechanisms that drive its establishment and composition, and how microbial consortia may be molded by natural or artificial interventions. Finally, we discuss the relevance of key microbial players of the infant gut microbiota, in particular bifidobacteria, with respect to their role in health and disease.

The First Microbial Colonizers of the Human Gut: Composition, Activities, and Health Implications of the Infant Gut Microbiota

https://www.clinicalmicrobiologyandinfection.com/article/S1198-743X(14)65086-2/pdf

The difficult-to-control spread of carbapenemase producers among Enterobacteriaceae worldwide

The emergence of carbapenem-resistant Gram-negative pathogens poses a serious threat to public health worldwide. In particular, the increasing prevalence of carbapenem-resistant Klebsiella pneumoniae is a major source of concern. Klebsiella pneumoniae carbapenemases (KPC) and carbapenemases of the oxacillinase-48 (OXA-48) type have been reported worldwide. New Delhi metallo--lactamase (NDM) carbapenemases were originally identified in Sweden in 2008 and have spread worldwide rapidly. In this review, we summarize the epidemiology of K. pneumoniae producing three carbapenemases (KPCs, NDMs, and OXA-48-like). Although the prevalence of each resistant strain varies geographically, K. pneumoniae producing KPCs, NDMs, and OXA-48-like carbapenemases have become rapidly disseminated. In addition, we used recently published molecular and genetic studies to analyze the mechanisms by which these three carbapenemases, and major K. pneumoniae clones, such as ST258 and ST11, have become globally prevalent. Because carbapenemase-producing K. pneumoniae are often resistant to most -lactam antibiotics and many other non--lactam molecules, the therapeutic options available to treat infection with these strains are limited to colistin, polymyxin B, fosfomycin, tigecycline, and selected aminoglycosides. Although combination therapy has been recommended for the treatment of severe carbapenemase-producing K. pneumoniae infections, the clinical evidence for this strategy is currently limited, and more accurate randomized controlled trials will be required to establish the most effective treatment regimen. Moreover, because rapid and accurate identification of the carbapenemase type found in K. pneumoniae may be difficult to achieve through phenotypic antibiotic susceptibility tests, novel molecular detection techniques are currently being developed.

/pdf/global-dissemination-of-carbapenemase-producing-klebsiella-4qyejl7z34.pdf

Global Dissemination of Carbapenemase-Producing Klebsiella pneumoniae: Epidemiology, Genetic Context, Treatment Options, and Detection Methods

Quinolone antimicrobials are synthetic and widely used in clinical medicine Resistance emerged with clinical use and became common in some bacterial pathogens Mechanisms of resistance include two categories of mutation and acquisition of resistance-conferring genes Resistance mutations in one or both of the two drug target enzymes, DNA gyrase and DNA topoisomerase IV, are commonly in a localized domain of the GyrA and ParE subunits of the respective enzymes and reduce drug binding to the enzyme-DNA complex Other resistance mutations occur in regulatory genes that control the expression of native efflux pumps localized in the bacterial membrane(s) These pumps have broad substrate profiles that include quinolones as well as other antimicrobials, disinfectants, and dyes Mutations of both types can accumulate with selection pressure and produce highly resistant strains Resistance genes acquired on plasmids can confer low-level resistance that promotes the selection of mutational high-level resistance Plasmid-encoded resistance is due to Qnr proteins that protect the target enzymes from quinolone action, one mutant aminoglycoside-modifying enzyme that also modifies certain quinolones, and mobile efflux pumps Plasmids with these mechanisms often encode additional antimicrobial resistances and can transfer multidrug resistance that includes quinolones Thus, the bacterial quinolone resistance armamentarium is large

/pdf/mechanisms-of-drug-resistance-quinolone-resistance-eervm3jsw6.pdf

Mechanisms of drug resistance: quinolone resistance.

Is MRSA more virulent than MSSA

We report an outbreak of linezolid-resistant Staphylococcus haemolyticus strains (MIC 32 mg/L) in patients admitted to the Verona University Hospital Intensive Care Unit. The strains proved to be clonally related at pulsed field gel electrophoresis. All the strains showed the G2576T mutation responsible for linezolid-resistance and retained their resistance even after several passages on antibiotic-free medium. After a decade of linezolid use, multifocal emergence of linezolid resistance in coagulase-negative staphylococci has become an important matter of concern and mandates stricter control over the use of this antibiotic in order to preserve its clinical utility.

Outbreak of linezolid-resistant Staphylococcus haemolyticus in an Italian intensive care unit.

https://www.clinicalmicrobiologyandinfection.com/article/S1198-743X(14)65345-3/pdf

Diversity of carbapenemases in clinical isolates of Enterobacteriaceae in Croatia—the results of a multicentre study

https://www.clinicalmicrobiologyandinfection.com/article/S1198-743X(14)61641-4/pdf

Description and plasmid characterization of qnrD determinants in Proteus mirabilis and Morganella morganii

https://www.clinicalmicrobiologyandinfection.com/article/S1198-743X(14)63217-1/pdf

Erika Kocsis

Papers

Is MRSA more virulent than MSSA

Outbreak of linezolid-resistant Staphylococcus haemolyticus in an Italian intensive care unit.

Diversity of carbapenemases in clinical isolates of Enterobacteriaceae in Croatia—the results of a multicentre study

Description and plasmid characterization of qnrD determinants in Proteus mirabilis and Morganella morganii

Klebsiella pneumoniae harbouring OXA-48 carbapenemase in a Libyan refugee in Italy