Several MALDI-TOF MS-based methods have been proposed for rapid detection of antimicrobial resistance. The most widely studied methods include assessment of β-lactamase activity by visualizing the hydrolysis of the β-lactam ring, detection of biomarkers responsible for or correlated with drug-resistance/non-susceptibility, and the comparison of proteomic profiles of bacteria incubated with or without antimicrobial drugs. Antimicrobial-resistance to a number of antibiotics belonging to different classes has been successfully tested by MALDI-TOF MS in a variety of clinically relevant bacterial species including members of Enterobacteriaceae family, non-fermenting Gram-negative bacteria, Gram-positive cocci, anaerobic bacteria and mycobacteria, opening this field to further clinically important developments. Early detection of drug-resistance by MALDI-TOF MS can be particularly helpful for clinicians to streamline the antibiotic therapy for a better outcome of patients with systemic infection, in all cases where a prompt and effective antibiotic treatment is essential to preserve organ function and/or patient survival.

This report describes the nosocomial acquisition of Candida parapsilosis candidemia by one of the six premature newborns housed in the same room of a neonatal intensive care unit at the Ospedale Santa Chiara, Pisa, Italy. The infant had progeria, a disorder characterized by retarded physical development and progressive senile degeneration. The infant, who was not found to harbor C. parapsilosis at the time of his admission to the intensive care unit, had exhibited symptomatic conjunctivitis before the onset of a severe bloodstream infection. In order to evaluate the source of infection and the route of transmission, two independent molecular typing methods were used to determine the genetic relatedness among the isolates recovered from the newborn, the inanimate hospital environment, hospital personnel, topically and intravenously administered medicaments, and indwelling catheters. Among the isolates collected, only those recovered from the hands of two nurses attending the newborns and from both the conjunctiva and the blood of the infected infant were genetically indistinguishable. Since C. parapsilosis was never recovered from indwelling catheters or from any of the drugs administered to the newborn, we concluded that (i) horizontal transmission of C. parapsilosis occurred through direct interaction between nurses and the newborn and (ii) the conjunctiva was the site through which C. parapsilosis entered the bloodstream. This finding highlights the possibility that a previous C. parapsilosis colonization and/or infection of other body sites may be a predisposing condition for subsequent C. parapsilosis hematogenous dissemination in severely ill newborns.

Bacillus cereus behaves as an opportunistic pathogen frequently causing gastrointestinal diseases, and it is increasingly recognized to be responsible for severe local or systemic infections. Pathogenicity of B. cereus mainly relies on the secretion of a wide array of toxins and enzymes and also on the ability to undergo swarming differentiation in response to surface-sensing. In this report, the pathogenicity exerted by B. cereus toxins is described with particular attention to the regulatory mechanisms of production and secretion of HBL, Nhe and CytK enterotoxins.

The number and disposition of flagella harbored by eubacteria are regulated by a specific trait successfully maintained over generations. The genes governing the number of flagella inBacillus subtilishave never been identified, although theifmlocus has long been recognized to influence the motility phenotype of this microorganism. The characterization of a spontaneousifmmutant ofB. subtilis, displaying diverse degrees of cell flagellation in both liquid and solid media, raised the question of how theifmlocus governs the number and assembly of functional flagella. The major finding of this investigation is the characterization of a newly identified dicistronic operon, namedswrA, that controls both swimming motility and swarming differentiation inB. subtilis. Functional analysis of theswrAoperon allowedswrAA(previously namedswrA[D. B. Kearns, F. Chu, R. Rudner, and R. Losick, Mol. Microbiol.52:357-369, 2004]) to be the first gene identified inB. subtilisthat controls the number of flagella in liquid environments and the assembly of flagella in response to cell contact with solid surfaces. Evidence is given that the second gene of the operon,swrAB, is essential for enabling the surface-adhering cells to undergo swarming differentiation. Preliminary data point to a molecular interaction between the two gene products.

Spore-forming Bacillus cereus is a common contaminant of dairy products. As the microorganism is widespread in the environment, it can contaminate milk at the time of milking, but it can also reach the dairy products in each phase of production, storage and ripening. Milk pasteurization treatment is not effective in reducing contamination and can instead act as an activator of spore germination, and a potential associated risk still exists with the consumption of some processed foods. Prevalences and concentrations of B. cereus in milk and dairy products are extremely variable worldwide: in pasteurized milk, prevalences from 2% to 65.3% were reported, with concentrations of up to 3 × 10⁵ cfu/g, whereas prevalences in cheeses ranged from 0 to 95%, with concentrations of up to 4.2 × 10⁶ cfu/g. Bacillus cereus is also well known to produce biofilms, a serious concern for the dairy industry, with up to 90% of spores that are resistant to cleaning and are easily transferred. As the contamination of raw materials is not completely avoidable, and the application of decontamination treatments is only possible for some ingredients and is limited by both commercial and regulatory reasons, it is clear that the correct application of hygienic procedures is extremely important in order to avoid and manage the circulation of B. cereus along the dairy supply chain. Future developments in interventions must consider the synergic application of different mild technologies to prevent biofilm formation and to remove or inactivate the microorganism on the equipment.

Bacillus thuringiensisis being used worldwide as a biopesticide, although increasing evidence suggests that it is emerging as an opportunistic human pathogen. While phospholipases, hemolysins, and enterotoxins are claimed to be responsible forB. thuringiensisvirulence, there is no direct evidence to indicate that the flagellum-driven motility plays a role in parasite-host interactions. This report describes the characterization of a mini-Tn10mutant ofB. thuringiensisthat is defective in flagellum filament assembly and in swimming and swarming motility as well as in the production of hemolysin BL and phosphatidylcholine-preferring phospholipase C. The mutant strain was determined to carry the transposon insertion inflhA, a flagellar class II gene encoding a protein of the flagellar type III export apparatus. Interestingly, theflhAmutant ofB. thuringiensissynthesized flagellin but was impaired in flagellin export. Moreover, a protein similar to the anti-sigma factor FlgM that acts in regulating flagellar class III gene transcription was not detectable inB. thuringiensis, thus suggesting that the flagellar gene expression hierarchy ofB. thuringiensisdiffers from that described forBacillus subtilis. TheflhAmutant ofB. thuringiensiswas also defective in the secretion of hemolysin BL and phosphatidylcholine-preferring phospholipase C, although both of these virulence factors were synthesized by the mutant. Since complementation of the mutant with a plasmid harboring theflhAgene restored swimming and swarming motility as well as secretion of toxins, the overall results indicate that motility and virulence inB. thuringiensismay be coordinately regulated byflhA, which appears to play a crucial role in the export of flagellar as well as nonflagellar proteins.