The role of spin states in the catalytic mechanism of the intra- and extradiol cleavage of catechols by O2.

Iron-dependent enzymes and biomimetic iron complexes can catalyze the ring cleavage of very inert, aromatic compounds. The mechanisms of these transformations and the factors that lead either to extradiol cleavage or intradiol cleavage have not been fully understood. By using density functional theory we have elucidated the mechanism of the catalytic cycle for two biomimetic complexes, and explained the difference in the experimentally obtained products.

Resolving the origin of the multimode Jahn-Teller effect in metallophthalocyanines.

A detailed Density Functional Theory (DFT) analysis was performed in order to study the multimode Jahn-Teller (JT) problem in the electronic ground state of manganese phthalocyanine (MnPc). A comparison with the magnesium phthalocyanine ion (MgPc-) and the phthalocyanine trianion (Pc3-), also prone to the JT effect, is presented. Our results clarify the origin and provide the microscopic insight into the symmetry breaking process. The JT distortion is highly influenced by the coordination of phthalocyanine to the MnII ion, and occurs over the whole system, while the MgPc- complex ion possesses mainly ligand-based instability.

Challenges in assignment of orbital populations in a high spin manganese(III) complex.

Magnetic, structural and computational data of four complex salts with the same mononuclear high spin octahedral Mn(iii) complex cation are reported. The manifestation of Jahn-Teller-like distortions in the Mn(iii) cation is dependent on the nature of the charge-balancing anion, with small anions yielding a planar elongation and large anions freezing out a preferential axial elongation along one of the amine-Mn-imine directions within that same plane. Modulation of the lattice by changing the charge balancing anion results in mixing of the orbital symmetry due to vibrational perturbation.

A density functional study of the spin state energetics of polypyrazolylborato complexes of first-row transition metals.

Density Functional Theory (DFT) was used to analyse and explain spin state energetics of first-row transition metals (Mn(II), Fe(II), Co(II); Cr(III), Mn(III), Fe(III), Co(III); Mn(IV)) in polypyrazolylborato complexes. We explored the effects of substitutions at the 3 and 5 positions of the pyrazolyl rings, as well as the influence of Jahn-Teller (JT) distortions on spin-state switching. Although the stabilizations due to JT distortion are sometimes substantial, this does not lead to switching of the spin ground-state. On the other hand, electron withdrawing or donating substituents do lead to significant changes in the spin-crossover (SCO) properties of the investigated complexes.

Human Dirofilaria repens infection in Serbia.

Human infection by Dirofilaria repens in Serbia has been increasing steadily. The first case was reported in 1971, presented in the form of a single subcutaneous nodule on the back of a young boy. As established by a literature search, eight additional cases were reported until mid-2001. The most frequent site of infection was subcutaneous tissue, with the exception of two cases, in which parasites were found in subconjunctiva and epididymis. Our study, conducted from 2001 to 2008, encompasses 19 new cases. Most of them (63.1%) presented as ocular or periocular infections, in which the parasite was typically found under the conjunctiva. In other cases a parasitic nodule was localized in the temporal region of the head, epididymis, testicle, abdomen, breast or arm. The diagnosis was made by morphological and histological analysis of the extracted intact worms and parasite sections from the tissue. Morphology of the filarial worms was well preserved in more than half of the cases (12/19) and there was never more than one parasite found inside the lesions. Adult worms and immature nematodes were observed in nine and seven cases, respectively. Furthermore, in two cases microfilariae were discovered inside the pseudocoelom, sections of the female reproductive tubes filled with clearly visible larval stages. Dirofilaria repens infection was diagnosed by its morphological features (17/19) or by performing polymerase chain reactions (PCR) using paraffin-embedded tissues (2/19) in the cases where the morphology was insufficient for identification and the parasites had been determined initially as Dirofilaria spp. The amplified 246 bp PCR product showed that the worms were D. repens.

Public transport as a reservoir of methicillin-resistant staphylococci.

AIMS: The aim of this study was to explore the occurrence of methicillin-resistant staphylococci in a large urban public transport system. METHODS AND RESULTS: Samples were taken from hand rails, which passengers hold onto when they are standing. In total, 1400 swabs taken from 55 vehicles (trolleybuses, trams and buses) were examined. As many as 30.1% samples were positive for the presence of methicillin-resistant coagulase-negative staphylococci (MRCoNS), but none for methicillin-resistant Staphylococcus aureus (MRSA). MRCoNS were isolated from all 55 vehicles. Nearly 50% of MRCoNS isolates displayed resistance not only to beta-lactams, but at least to two or more other classes of antimicrobials as well. CONCLUSIONS: This study demonstrated widespread occurrence of MRCoNS on hand rails in public transport vehicles. MRSA was not detected. SIGNIFICANCE AND IMPACT OF THE STUDY: The recovery of methicillin-resistant staphylococci from public transport system implies a potential risk for transmission of these bacteria in an out-hospital environment.

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.

Effect of environmental factors on biofilm formation by clinical Stenotrophomonas maltophilia isolates.

The influence of environmental factors (temperature, aerobiosis-anaerobiosis, static-dynamic conditions, pH) was determined on biofilm formation by 51 S. maltophilia clinical isolates. The strains produced more biofilm at 32 degrees C than at 37 or 18 degrees C. Aerobic and 6% CO2 atmosphere yielded comparable biofilm amounts, higher than under anaerobic conditions. Biofilm production was not affected by static vs. agitated culture conditions. Biofilm production at pH 7.5 and 8.5 was comparable but significantly higher than at pH 5.5. The capacity of individual strains to form biofilm and thus contribute to the severity of some diseases is influenced by host traits and environmental conditions at the site of infection, and play an important role in the pathogenesis of biomaterial-related disease caused by S. maltophilia.

Reduced quantity and hydrogen-peroxide production of vaginal lactobacilli in HIV positive women.

It has been suggested that vaginal lactobacilli may influence heterosexual transmission of HIV infection. The aim of this study was to compare the vaginal flora on Gram's stained and isolation rate, quantity and H2O2 production of lactobacilli between HIV positive and HIV negative women. Although, the prevalence of abnormal vaginal flora was increased in HIV infected women, there was no significant difference in isolation rate of vaginal lactobacilli between the two groups (71.87 vs. 83.33%; P>0.05). However, the results of this study showed significantly reduced quantity of lactobacilli in HIV infected women (P<0.01). In particular, the prevalence of H2O2-producing lactobacilli was lower in HIV positive as compared to HIV negative women (80 vs. 56.52%), with borderline significance (P=0.057). Taken together, our findings showed altered vaginal microflora with reduced quantity and hydrogen-peroxide production of vaginal lactobacilli in HIV positive women, but further studies are needed to assess its actual significance and potential benefit from the use of probiotic therapy.

Staphylococcus sciuri: an unusual cause of pelvic inflammatory disease.

We present the case of polymicrobial pelvic inflammatory disease (PID) that involved Staphylococcus sciuri, S. epidermidis, and Streptococcus agalactiae. In order to determine the frequency of S. sciuri isolation from the female lower genital tract, 3415 vaginal samples were analysed during the one-year study period. S. sciuri was isolated from three (0.09%) samples. In all the three cases, S. sciuri was obtained in mixed culture from outpatients without symptoms of infection. While the origin of S. sciuri in the female genital tract remains to be elucidated, the present study showed that this bacterium may colonize vagina and, moreover, may be involved in the pathogenesis of an infection as serious as PID. The low rate of isolation we established, however, indicates infrequent and, most probably, transient colonization of the female genital tract by S. sciuri.

[Colonization of cental venous catheter in the Intensive Care Units at the Institute of Cardiovascular Disease "Dedinje"--one year study].

OBJECTIVES: The application of Central Venous Catheters (CVC) is associated with increased risk of microbial colonization and infection. The aim of present study was to assess the frequency of pathogens colonizing CVC and to determine their susceptibility pattern to various antimicrobial agents. MATERIALS AND METHODS: A total of 253 samples of CVC from intensive care units (ICU) patients were received for culture during 2003. All microorganisms were identified by standard microbiological methods and the susceptibility to antimicrobial agents was determined according to NCCLS recommendations. RESULTS: A total of 184 (72.7%) cultures were positive and 223 pathogens were isolated. Coagulase negative staphylococci (CNS) were the dominant isolates (24.7%), followed by Enterobacter spp. (12.1%), Pseudomonas spp. (11.7%), Enterococcus spp. (9.9%), Klebsiella spp. (8.6%), Candida spp. (7.6%), Acinetobacter spp. (7.6%), other Gram negative nonfermentative bacilli (5.8%), Serratia spp. (4.5%), Staphylococcus aureus (2.6%), Proteus mirabilis (2.2%), E. coli (1.8%) and Citrobacter spp. (0.9%). Meropenem (84.5%) and vancomycin (100%) remain the most effective antimicrobial agents against Gram negative and Gram positive bacteria, respectively. CONCLUSION: Gram negative bacilli and CNS are the commonest microorganisms colonizing CVC from ICU patients. The increasing resistance of the bacteria to antimicrobial agents is the major problem in spite of restricted policy of using antimicrobial agents in ICU.

Influence of acetylsalicylic acid (aspirin) on biofilm production by Candida species.

Candida spp. are important causative agents of infections associated with biofilm formation. Management of biofilm-related infections is extremely difficult and therefore new therapeutic solutions are needed. This study for the first time explored the possible effect of aspirin on Candida spp. Biofilm-producing capacity. Two strains of C. guilliermondii, and one strain per species of C. kefyr, C. glabrata, C. albicans, and C. parapsilosis were included in the study. The antifungal property of aspirin was tested by the broth microdilution method, while effect of aspirin on biofilm formation was determined by the microtiter-plate test. The minimal inhibitory concentrations of aspirin obtained ranged from 2.17 to 8.67 mM and minimal fungicidal concentrations were from 4.33 to 8.67 mM. The concentrations of aspirin which induced statistically significant decrease in biofilm formation ranged from 0.43 mM to 1.73 mM of aspirin, depending on the tested yeast strain. Therefore, the significant effects of aspirin on growth and biofilm formation of Candida spp. were achieved only with suprapharmacological concentrations of the drug. The influence of the inoculum size on the effect of aspirin on biofilm formation was determined for C. albicans only and a significant decrease was observed also at suprapharmacological concentrations of aspirin, irrespective of the inoculum size. The results obtained in the present study show aspirin to be a drug with the potential to affect and suppress biofilm formation by Candida spp., and provide support for further investigation.

Meropenem therapy failure in Listeria monocytogenes infection.

Listeria monocytogenes is highly susceptible to meropenem in vitro, but data on the efficacy of meropenem in clinical cases of listeriosis are scarce. Described here is the case of a child with aplastic anemia who acquired nosocomial listeriosis and failed to respond to initial meropenem therapy. Resolution of fever was not noted after 5 days of therapy with meropenem and, more importantly, clinical worsening was observed during this period. The patient began to improve after ampicillin was introduced to the therapeutic regimen. In total, meropenem was administered for 15 days and ampicillin for 10 days.

Biofilm formation by Salmonella spp. and Listeria monocytogenes on plastic surface.

AIMS: To investigate the biofilm formation by 122 Salmonella spp. and 48 Listeria monocytogenes strains on a plastic surface. METHODS: Quantification of biofilm formation was performed in brain heart infusion (BHI), trypcase soya broth (TSB), meat broth (MB) and 1/20 diluted trypcase soya broth (1/20-TSB) in plastic microtitre plates. RESULTS: All tested Salmonella spp. and L. monocytogenes strains produced biofilm in a suitable medium. However, the quantities of biofilm produced by Salmonella spp. were greater than those produced by tested L. monocytogenes strains. The nutrient content of the medium significantly influenced the quantity of produced biofilm. Diluted TSB was the most effective in promoting biofilm production by Salmonella spp., followed by TSB, while the least quantity of biofilm was formed in BHI and MB. L. monocytogenes produced the highest quantities of biofilm in BHI, followed by TSA, then MB, and the least quantities of biofilm were produced in 1/20-TSB. CONCLUSIONS: Salmonella spp. produces more biofilm in nutrient-poor medium, while L. monocytogenes produce more biofilm in nutrient-rich medium.

Enterococcus durans endocarditis in a patient with transposition of the great vessels.

A case of native valve endocarditis caused by Enterococcus durans in a patient with transposition of the great vessels is reported. The patient was treated initially with gentamicin and ceftriaxone; after isolation of enterococci, ceftriaxone was switched to ampicillin. The only virulence factors established in the strain were haemolytic activity and biofilm formation.

Influence of the incubation atmosphere on the production of biofilm by staphylococci.

Biofilm formation by Staphylococcus epidermidis, Staphylococcus hemolyticus, Staphylococcus sciuri and Staphylococcus aureus in aerobic, anaerobic and CO2 incubation atmospheres was quantified by the modified microtiter plate test. The S. epidermidis and S. aureus strains showed significantly lower biofilm production when grown in a CO2-rich environment compared to that exhibited in aerobic incubation. The amount of biofilm produced by these strains under anaerobic conditions did not differ significantly from the biofilm formation detected in the aerobic incubation. The incubation atmosphere did not affect S. sciuri biofilm formation. Biofilm production by S. hemolyticus isolates was very low regardless of the experimental conditions used.

Significance of inoculum size in biofilm formation by staphylococci.

In the present study the effect of inoculum size, ranging from 10(6) to 1 cell, in biofilm formation by staphylococci was determined by microtiter plate test. The initial inoculum size had a dramatic effect on the quantity of biofilm formed. A decreased number of bacteria in initial inoculum always resulted in a decreased production of biofilm.

Ground red hot pepper agar in the isolation and presumptive identification of Cryptococcus neoformans.

The study compared ground red hot pepper agar (GRHP) and Guizotia abyssinica creatinine agar (GACA), a medium routinely used for isolation of Cryptococcus neoformans. In order to confirm the capacity of GRHP to support the Cr. neoformans growth and pigment production, 15 strains were inoculated onto GRHP and GACA. No significant differences in the growth and pigmentation of the tested strains on the two media were noted. As heavily contaminated specimens, 50 samples of pigeon droppings were examined by plating on GRHP and GACA, which resulted in the isolation of 14 and nine Cr. neoformans strains, respectively. The results indicate that GRHP, as a result of its superior selectivity and significant reduction of contaminant growth, provides better conditions than GACA for isolation and presumptive identification of Cr. neoformans from heavily contaminated specimens.

Influence of dynamic conditions on biofilm formation by staphylococci.

The modified microtiter plate test was used to investigate biofilm formation by staphylococci under both static and dynamic conditions. The quantity of biofilm produced under static conditions was used as a reference. Dynamic conditions, which were achieved by incubating microtiter plates on a horizontal shaker with and without the presence of glass beads in wells, either reduced biofilm formation or left it unchanged. Dynamic conditions particularly affected the capacity of certain species to produce biofilm: these species included the causative agents of infections associated with a foreign body (Staphylococcus epidermidis, Staphylococcus aureus). On the basis of these results, dynamic conditions should be included as a parameter for evaluating biofilm formation by staphylococci in vitro.

Staphylococcus sciuri as a part of skin, nasal and oral flora in healthy dogs.

The coagulase-negative species Staphylococcus sciuri is widespread in nature and is associated with a variety of domestic and wild animals. However, the occurrence of S. sciuri in dogs has received little attention so far. In the present study, we established the prevalence of S. sciuri in a large population of healthy dogs, and characterized isolated strains. Samples from two mucous membrane sites (anterior nares and mouth), and two hair-coated sites (head and withers) were taken from 122 dogs and inoculated into STS agar, a novel selective medium that was introduced and tested in the study. In total, 116 isolates of S. sciuri were obtained from 488 specimens. S. sciuri was isolated from 56 out of 122 (46%) dogs. The occurrence of S. sciuri in the anterior nares and mouth were significantly higher than those in withers and head. No significant association of S. sciuri occurrence in dogs and factors such as sex, age, and living environment (indoor/outdoor) was found. Out of 56 dogs, which tested positive for S. sciuri, 30 (54%) would have it as a resident flora. Thus, we showed that S. sciuri was frequently present as a part of skin, nasal and oral flora in healthy dogs both as a resident and transient carriage.