Biofilm Formation among Stenotrophomonas maltophilia Isolates Has Clinical Relevance: The ANSELM Prospective Multicenter Study.

The ability to form biofilms is a recognized trait of Stenotrophomonas maltophilia, but the extent of its clinical relevance is still unclear. The present multicenter prospective study (ANSELM) aims at investigating the association between biofilm formation and clinical outcomes of S. maltophilia infections. One hundred and nine isolates were collected from various geographical origins and stratified according to their clinical relevance. Biofilm formation was evaluated by the microtiter plate assay and correlated with microbiological and clinical data from the associated strains. Antibiotic susceptibility of the planktonic cells was tested by the disk diffusion technique, while antibiotic activity against mature biofilms was spectrophotometrically assessed. Most strains (91.7%) were able to form biofilm, although bloodborne strains produced biofilm amounts significantly higher than strains causing hospital- rather than community-acquired infections, and those recognized as "definite" pathogens. Biofilm formation efficiency was positively correlated with mechanical ventilation (p = 0.032), whereas a negative relationship was found with antibiotic resistance (r2 = 0.107; p < 0.001), specifically in the case of the pathogenic strains. Mature S. maltophilia biofilms were markedly more resistant (up to 128 times) to cotrimoxazole and levofloxacin compared with their planktonic counterparts, especially in the case of bloodborne strains. Our findings indicate that biofilm formation by S. maltophilia is obviously a contributing factor in the pathogenesis of infections, especially in deep ones, thus warranting additional studies with larger cohort of patients and isolates.

Lyme Endocarditis as an Emerging Infectious Disease: A Review of the Literature.

Lyme endocarditis is extremely rare manifestation of Lyme disease. The clinical manifestations of Lyme endocarditis are non-specific and can be very challenging diagnosis to make when it is the only manifestation of the disease. Until now, only a few cases where reported. Physicians should keep in mind the possibility of borrelial etiology of endocarditis in endemic areas. Appropriate valve tissue sample should be sent for histopathology, culture, and PCR especially in case of endocarditis of unknown origin PCR on heart valve samples is recommended. With more frequent PCR, Borrelia spp. may be increasingly found as a cause of infective endocarditis. Prompt diagnosis and treatment of Lyme carditis may prevent surgical treatment and pacemaker implantations. Due to climate change and global warming Lyme disease is a growing problem. Rising number of Lyme disease cases we can expect and rising number of Lyme endocarditis.

Longitudinal Outbreak of Multidrug-Resistant Tuberculosis in a Hospital Setting, Serbia.

A retrospective population-based molecular epidemiologic study of multidrug-resistant Mycobacterium tuberculosis complex strains in Serbia (2008-2014) revealed an outbreak of TUR genotype strains in a psychiatric hospital starting around 1990. Drug unavailability, poor infection control, and schizophrenia likely fueled acquisition of additional resistance and bacterial fitness-related mutations over 2 decades.

Pulmonary isolation and clinical relevance of nontuberculous mycobacteria during nationwide survey in Serbia, 2010-2015.

The rates of pulmonary colonization and disease due to nontuberculous mycobacteria (NTM) appear to be increasing globally, but diversity of species recovered as well as clinical relevance of NTM isolates differ considerably by geographic region. The first nationwide study of isolation frequency and clinical significance of NTM in Serbia included all patients with respiratory specimens yielding a positive NTM culture over the six-year period, 2010-2015. We analyzed trends in annual NTM isolation and NTM pulmonary disease (PD) incidence rates, with NTM PD cases defined in accordance with microbiological criteria established by the American Thoracic Society/Infectious Diseases Society of America (ATS/IDSA). 777 pulmonary NTM isolates were collected from 565 patients, of whom 126 (22.3%) met the ATS/IDSA criteria. The annual NTM isolation and NTM PD incidence rates per 100,000 changed over 2010-2015 from 0.9 to 1.6 (p = 0.1746) and from 0.18 to 0.48 (p = f0.0040), respectively. Both isolation and disease rates increased considerably with age, while higher NTM PD rates were also associated with residence in urbanized areas. Diversity of NTM species isolated was shown to be region-specific, with M. xenopi as the most prevalent species (17.3%), and increasing isolation rates of rapid growing mycobacteria (RGM) (p = 0.0072). M. xenopi was also the most common cause of NTM PD (28.6%), followed by RGM (27.8%). With 73% clinically relevant isolates, M. abscessus was identified as the most clinically relevant NTM species. While NTM PD obviously remains a rare disease in Serbia, the overall results justify recognition of NTM as pathogens of rising importance, and require further characterization of their epidemiology in the country.

Influence of subinhibitory antibiotic concentration on Streptococcus pyogenes adherence and biofilm production.

In this study, the focus was on the effects of sub-MICs of the antibiotics on adherence, hydrophobicity, and biofilm formation by two groups of Streptococcus pyogenes strains, which were responsible for different clinical cases. The aim of this study was to explore the effects of sub-MICs of penicillin, ceftriaxone, erythromycin, and clindamycin on adherence, surface hydrophobicity, and biofilm biomass in two selected collections of group A streptococcus (GAS): strains isolated from carriers (CA) and strains isolated from patients with tonsillopharyngitis (TPh). Isolates were tested for hydrophobicity to xylene, adherence, and biofilm production in uncoated microtiter plates before and after treatment with 1/2 and 1/4 MICs of antibiotics. Penicillin reduced adherence and biofilm production in TPh strains, whereas ceftriaxone diminished adherence and biofilm formation in CA group. On the contrary, clindamycin enhanced adherence and biofilm production in both groups of strains. Erythromycin did not significantly alter adherence, but triggered biofilm production in both groups of isolates. Hydrophobicity of both groups of strains was significantly reduced after exposure to all antibiotics. Beta-lactams displayed anti-biofilm activity; penicillin diminished both adherence and biofilm production in TPh strains, whereas ceftriaxone reduced it in strains isolated from CA.

Effects of penicillin and erythromycin on adherence of invasive and noninvasive isolates of Streptococcus pyogenes to laminin.

This study investigated the possible relationship between the invasiveness of group A Streptococcus (GAS) strains and their abilities to adhere to laminin and assessed the effects of subinhibitory concentrations of penicillin and erythromycin on the ability of GAS to adhere to laminin. The adherence of noninvasive and highly invasive isolates of GAS to laminin was significantly higher than the adherence displayed by isolates of low invasiveness. Antibiotic treatment caused significant reductions in adherence to laminin in all three groups of strains. Penicillin was more successful in reducing the adherence abilities of the tested GAS strains than erythromycin.

Multichannel nonlinear distortion compensation using optical phase conjugation in a silicon nanowire.

We experimentally demonstrate compensation of nonlinear distortion caused by the Kerr effect in a 3 × 32-Gbaud quadrature phase-shift keying (QPSK) wavelength-division multiplexing (WDM) transmission system. We use optical phase conjugation (OPC) produced by four-wave mixing (FWM) in a 7-mm long silicon nanowire. A clear improvement in Q-factor is shown after 800-km transmission with high span input power when comparing the system with and without the optical phase conjugation module. The influence of OSNR degradation introduced by the silicon nanowire is analysed by comparing transmission systems of three different lengths. This is the first demonstration of nonlinear compensation using a silicon nanowire.

Evolutionary history and global spread of the Mycobacterium tuberculosis Beijing lineage.

Mycobacterium tuberculosis strains of the Beijing lineage are globally distributed and are associated with the massive spread of multidrug-resistant (MDR) tuberculosis in Eurasia. Here we reconstructed the biogeographical structure and evolutionary history of this lineage by genetic analysis of 4,987 isolates from 99 countries and whole-genome sequencing of 110 representative isolates. We show that this lineage initially originated in the Far East, from where it radiated worldwide in several waves. We detected successive increases in population size for this pathogen over the last 200 years, practically coinciding with the Industrial Revolution, the First World War and HIV epidemics. Two MDR clones of this lineage started to spread throughout central Asia and Russia concomitantly with the collapse of the public health system in the former Soviet Union. Mutations identified in genes putatively under positive selection and associated with virulence might have favored the expansion of the most successful branches of the lineage.

Polarization-insensitive wavelength conversion of 40 Gb/s NRZ-DPSK signals in a silicon polarization diversity circuit.

Polarization insensitive wavelength conversion of a 40 Gb/s non-return-to-zero (NRZ) differential phase-shift keying (DPSK) data signal is demonstrated using four-wave mixing (FWM) in a silicon nanowire circuit. Polarization independence is achieved using a diversity circuit based on polarization rotators and splitters, which is fabricated by a simple process on the silicon-on-insulator (SOI) platform. Error-free performance is achieved with only 0.5 dB of power penalty compared to the wavelength conversion of a signal with well optimized input polarization. Additionally, data transmission over 161 km standard single-mode fiber (SSMF) is demonstrated at 40 Gb/s using optical phase conjugation (OPC) in the proposed circuit.

Phase regeneration of DPSK signals in a silicon waveguide with reverse-biased p-i-n junction.

Phase regeneration of differential phase-shift keying (DPSK) signals is demonstrated using a silicon waveguide as nonlinear medium for the first time. A p-i-n junction across the waveguide enables decreasing the nonlinear losses introduced by free-carrier absorption (FCA), thus allowing phase-sensitive extinction ratios as high as 20 dB to be reached under continuous-wave (CW) pumping operation. Furthermore the regeneration properties are investigated under dynamic operation for a 10-Gb/s DPSK signal degraded by phase noise, showing receiver sensitivity improvements above 14 dB. Different phase noise frequencies and amplitudes are examined, resulting in an improvement of the performance of the regenerated signal in all the considered cases.

[Nasal carriage of methicillin-resistant Staphylococcus aureus among medical students of Belgrade University].

INTRODUCTION: Infections caused by methicillin-resistant Staphylococcus aureus (MRSA) present the growing problem in the whole world. Carriage of MRSA is most frequent in the nose, and medical students come in contact both with patients and different persons in the community. Therefore, they may be significant for the transmission of MRSA from hospitals to out-of-hospital communities and vice versa. OBJECTIVE: The aim of this study was to establish the carriage rate among students of the second, third and fourth year of study at the School of Medicine in Belgrade and to analyze their genotypic and phenotypic characteristics. METHODS: In total 533 nasal samples were taken. The samples were incubated inTrypcase-soy broth supplemented with 6.5% NaCl, and thereafter the swabs were inoculated on mannitol salt agar supplemented with 2 microg/mL of oxacillin. The presence of nuc, mecA and Panton-Valentine leukocidin genes was examined by PCR.The characteristics of the MRSA strains were determined using: antibiotic susceptibility testing by Vitek2 System, SCCmec, agr typing and MLST. RESULTS: MRSA was isolated from two of 533 investigated samples (0.37%). MRSA were isolated from the students of the second and third year of study. Profiles of strains were: ST80 (SCCmec type IV, agr type 3) and ST152 (SCCmec type V, agr type 1). MRSA strains were multiresistant. CONCLUSION: The nasal carriage rate of MRSA in population of medical students of the first year of study in Belgrade is low. Genotypic and phenotypic characteristics of MRSA strains indicate their community origin. MLST typing revealed that isolates belong to ST80 and ST152.

Switching characteristics of an InP photonic crystal nanocavity: experiment and theory.

The dynamical properties of an InP photonic crystal nanocavity are experimentally investigated using pump-probe techniques and compared to simulations based on coupled-mode theory. Excellent agreement between experimental results and simulations is obtained when employing a rate equation model containing three time constants, that we interpret as the effects of fast carrier diffusion from an initially localized carrier distribution and the slower effects of surface recombination and bulk recombination. The variation of the time constants with parameters characterizing the nanocavity structure is investigated. The model is further extended to evaluate the importance of the fast and slow carrier relaxation processes in relation to patterning effects in the device, as exemplified by the case of all-optical wavelength conversion.

Identification and antimicrobial susceptibility testing of Staphylococcus vitulinus by the BD phoenix automated microbiology system.

This study evaluated the performance of the BD Phoenix system for the identification (ID) and antimicrobial susceptibility testing (AST) of Staphylococcus vitulinus. Of the 10 S. vitulinus isolates included in the study, 2 were obtained from the Czech Collection of Microorganisms, 5 from the environment, 2 from human clinical samples, and 1 from an animal source. The results of conventional biochemical and molecular tests were used for the reference method for ID, while antimicrobial susceptibility testing performed in accordance with Clinical and Laboratory Standards Institute recommendations and PCR for the mecA gene were the reference for AST. Three isolates were incorrectly identified by the BD Phoenix system; one of these was incorrectly identified to the genus level, and two to the species level. The results of AST by the BD Phoenix system were in agreement with those by the reference method used. While the results of susceptibility testing compared favorably, the 70% accuracy of the Phoenix system for identification of this unusual staphylococcal species was not fully satisfactory.

Long-term analysis of Listeria monocytogenes vaginal carriage frequency in Belgrade, Serbia (short communication).

In order to gain insight into the frequency of L. monocytogenes vaginal carriage among women of reproductive age in Belgrade, Serbia, we conducted the long-term investigation (January 1992 through August 2006) described herein. The study population of 958 women included 799 patients with spontaneous abortion and 159 patients with infertility. A low rate of L. monocytogenes vaginal carriage of 0.1% was established, since only one strain was recovered from vaginal swab of a woman with spontaneous abortion.

Quantification of biofilm in microtiter plates: overview of testing conditions and practical recommendations for assessment of biofilm production by staphylococci.

The details of all steps involved in the quantification of biofilm formation in microtiter plates are described. The presented protocol incorporates information on assessment of biofilm production by staphylococci, gained both by direct experience as well as by analysis of methods for assaying biofilm production. The obtained results should simplify quantification of biofilm formation in microtiter plates, and make it more reliable and comparable among different laboratories.

Aminoglycoside resistance in members of the Staphylococcus sciuri group.

This study investigated the prevalence of aminoglycoside resistance and genes encoding aminoglycoside-modifying enzymes in members of the Staphylococcus sciuri group. A total of 304 S. sciuri group member isolates (284 S. sciuri, 12 S. lentus, and 8 S. vitulinus) from humans (n = 34), animals (n = 133), and environmental sources (n = 137; out-hospital and hospital environment, food) were examined for their susceptibility to amikacin, gentamicin, isepamicin, kanamycin, neomycin, netilmicin, sisomicin, streptomycin, and tobramycin. The overall prevalence of resistance to aminoglycosides was low at 12.1%. Resistance to single aminoglycosides ranged from 0% to 7.2%. The aac(6')-Ie/aph(2"), ant(4')-Ia, and aph(3')-IIIa genes, either alone or in combination, were found in 16 out of 19 isolates showing resistance to nonstreptomycin aminoglycosides. Among the 22 isolates that showed resistance to streptomycin, the genes str and ant(6)-Ia were identified in 18 and 4 isolates, respectively.

Supplementary biochemical tests useful for the differentiation of oxidase positive staphylococci.

Differentiation of the oxidase positive staphylococci, Staphylococcus sciuri, Staphylococcus lentus, Staphylococcus vitulinus and Staphylococcus fleurettii, based on tributyrin, urease, caseinase, gelatinase and DNase activity is described. These tests may be used for preliminary identification of oxidase positive isolates of staphylococci resulting in more accurate identification of these species.