Participation of the arcRACME protein in self-activation of the arc operon located in the arginine catabolism mobile element in pandemic clone USA300

ABSTRACT Staphylococcus aureus pandemic clone USA300 has, in addition to its constitutive arginine catabolism (arc) gene cluster, an arginine catabolism mobile element (ACME) carrying another such cluster, which gives this clone advantages in colonisation and infection. Gene arcR, which encodes an oxygen-sensitive transcriptional regulator, is inside ACME and downstream of the constitutive arc gene cluster, and this situation may have an impact on its activation. Different relative expression behaviours are proven here for arcRACME and the arcACME operon compared to the constitutive ones. We also show that the artificially expressed recombinant ArcRACME protein binds to the promoter region of the arcACME operon; this mechanism can be related to a positive feedback model, which may be responsible for increased anaerobic survival of the USA300 clone during infection-related processes.

Infección grave por Staphylococcus aureus meticilino sensible productor de leucocidina de Panton-Valentine: reportes de dos casos / Severe infection by methicillin sensitive Staphylococcus aureus producing Panton-Valentine leukocidin: reports of two cases

Staphylococcus aureus es uno de los principales agentes etiológicos de infecciones en niños provenientes de la comunidad y del ámbito hospitalario. La gravedad de estos cuadros se asocia a factores de virulencia, entre los que se encuentra la leucocidina de Panton-Valentine. Tanto Staphylococcus aureus resistente como sensible a la meticilina producen esta leucocidina, aunque con frecuencia variable. Presentamos a dos niños con infección grave por Staphylococcus aureus sensible a la meticilina productor de leucocidina de Panton-Valentine con complicaciones osteoarticulares y endovasculares. Es fundamental la sospecha diagnóstica, el tratamiento antibiótico adecuado y el manejo quirúrgico precoz para mejorar el abordaje de estas infecciones. Se debe mantener la vigilancia epidemiológica para detectar la frecuencia de las infecciones causadas por estas bacterias.

Staphylococcus aureus is a major etiologic agent of infections in children from the community and the hospital setting. The severity of these conditions is associated with virulence factors, including the Panton-Valentine leukocidin. Both methicillin resistant and sensitive Staphylococcus aureus produce this leukocidin although with varying frequency. We present two children with severe infection by sensitive Staphylococcus aureus producer of Panton-Valentine leukocidin with musculoskeletal and endovascular complications. It is essential the suspected diagnosis, appropriate antibiotic treatment and early surgical management to improve the approach of these infections. Epidemiological surveillance should be mantained to detect the frequency of infections caused by these bacteria.

Habituation of enterotoxigenic Staphylococcus aureus to Origanum vulgare L. essential oil does not induce direct-tolerance and cross-tolerance to salts and organic acids

Enterotoxigenic Staphylococcus aureus strains that were isolated from foods were investigated for their ability to develop direct-tolerance and cross-tolerance to sodium chloride (NaCl), potassium chloride (KCl), lactic acid (LA) and acetic acid (AA) after habituation in sublethal amounts (1/2 of the minimum inhibitory concentration - 1/2 MIC and 1/4 of the minimum inhibitory concentration - 1/4 MIC) of Origanum vulgare L. essential oil (OVEO). The habituation of S. aureus to 1/2 MIC and 1/4 MIC of OVEO did not induce direct-tolerance or cross-tolerance in the tested strains, as assessed by modulation of MIC values. Otherwise, exposing the strains to OVEO at sublethal concentrations maintained or increased the sensitivity of the cells to the tested stressing agents because the MIC values of OVEO, NaCl, KCl, LA and AA against the cells that were previously habituated to OVEO remained the same or decreased when compared with non-habituated cells. These data indicate that OVEO does not have an inductive effect on the acquisition of direct-tolerance or cross-tolerance in the tested enterotoxigenic strains of S. aureus to antimicrobial agents that are typically used in food preservation.

Efecto de los factores solubles de Staphylococcus aureus, Staphylococcus capitis y Staphylococcus epidermidis sobre la funcionalidad espermática / Effect of soluble factors of Staphylococcus aureus, Staphylococcus capitis and Staphylococcus epidermidis on sperm functionality

ANTECEDENTES: La interacción entre los espermatozoides con algunas especies bacterianas o sus factores solubles influyen en el deterioro de la calidad seminal, alterando la función reproductiva del hombre. OBJETIVO: El objetivo de este trabajo fue determinar el efecto de los factores solubles de Staphylococcus aureus, Staphylococcus capitis y Staphylococcus epidermidis sobre la calidad seminal. MÉTODO: Los factores solubles producto del metabolismo bacteriano de las cepas de S. aureus y S. Capitis sensible a oxacilina y S. aureus y S. Epidermidis resistente a oxacilina se incubaron con las muestras de semen de 20 voluntarios y se cuantificaron los parámetros seminales convencionales y funcionales por microscopía y citometría de flujo, respectivamente. RESULTADOS: Se observó una disminución en la movilidad espermática con los factores solubles de S. aureus, esta disminución fue mayor con la cepa sensible y el efecto negativo sobre la movilidad fue inmediato. Al incubar los espermatozoides con los factores solubles de S. aureus sensible a oxacilina, se afectaron todos los parámetros funcionales excepto la integridad de la cromatina y se observó menor liberación de especies reactivas de oxígeno; con los factores solubles de la cepa de S. aureus resistente a oxacilina se observó una disminución en la lipoperoxidación de membrana y en la expresión de anexina V. CONCLUSIÓN: Este estudio da cuenta del efecto negativo de los factores solubles de la bacteria S. aureus tanto sensible como resistente a oxacilina sobre los parámetros espermáticos convencionales y funcionales, y por ende en su función reproductiva.

BACKGROUND: The interaction between sperm with some bacteria species and their soluble factors are the deterioration of semen quality by altering the reproductive function of man. AIM: The aim of this study was to determine the effect of soluble factors Staphylococcus aureus, Staphylococcus epidermidis and Staphylococcus capitis on semen quality. METHODS: The soluble factors product of bacterial metabolism of the strains of S. aureus and S. capitis methicillin sensitive and S. aureus and S. epidermidis resistant to oxacillin, were incubated with semen samples from 20 volunteers. Subsequently, conventional seminal parameters were measured and functional quantified by microscopy and flow cytometry, respectively. RESULTS: A decrease was observed in sperm motility with soluble factors of S. aureus, this decrease was higher with the sensitive strain that with oxacillin resistant strain and the negative effect on motility was immediate. By incubating the sperm with soluble factor from oxacillin-sensitive S. aureus, all functional parameters were affected except the chromatin integrity and reduced release of reactive oxygen species, mean fluorescence intensity in oxacillin resistant S. aureus strain was decrease in membrane lipid peroxidation and annexin V expression. CONCLUSIONS: This study reports the negative effect of soluble factors of bacteria either S. aureus sensitive and resistant to oxacillin, over conventional and functional sperm parameters, and therefore in their reproductive function.

Success stories about severe pneumonia caused by Panton-Valentine leucocidin-producing Staphylococcus aureus

We describe three cases of community-acquired necrotizing pneumonia which were caused by Panton-Valentine leucocidin-producing strains of Staphylococcus aureus (one of them methicillin sensitive). All cases were successfully treated without any sequelae for the patients due to the prompt initiation of adequate antimicrobial therapy. High suspicion toward this fatal pathogen was the key to the successful outcome of the patients.

Presence of enterotoxigenic Staphylococcus aureus in artisan fruit salads in the city of San Luis, Argentina

An increase in the consumption of fruit juices and minimally processed fruits salads has been observed in recent years all over the world. In this work, the microbiological quality of artisan fruit salads was analysed. Faecal coliforms, Salmonella spp, Shigella spp, Yersinia enterocolitica and Escherichia coli O157:H7 were not detected; nevertheless, eleven strains of Staphylococcus aureus were isolated. By multiplex PCR, all isolates showed positive results for S. aureus 16S rRNA gene and 63.6% of them were positive for sea gene. Furthermore, PCR sea positive strains were able to produce the corresponding enterotoxin. Finally, the inactivation of these strains in fruit salads by nisin, lysozyme and EDTA, was studied. EDTA produced a total S. aureus growth inhibition after 60 h of incubation at a concentration of 250 mg/L. The presence of S. aureus might indicate inadequate hygiene conditions during salad elaboration; however, the enterotoxigenicity of the strains isolated in this study, highlights the risk of consumers' intoxication. EDTA could be used to inhibit the growth of S. aureus in artisan fruit salads and extend the shelf life of these products.

Actividad antibacteriana del Schinus molle l cultivado en Italia / Antibacterial activity of Schinus molle I grown in Italy

El objetivo de esta investigación fue determinar la actividad antibacteriana del extracto etanolico de las hojas y el extracto hexanoico obtenido de los frutos del Schinus molle L. (Anacardiaceae), cultivado en Italia, con un rendimiento de 32,42 % y 5,63 %, respectivamente. Independientemente del tipo de extracto y de la parte de la planta utilizada, el Schinus molle L., mostró una buena actividad antibacteriana contra bacterias Gram positivas (S. aureus ATCC 29213 y E. faecalis ATCC 29212) con una CMI 16 µg/mL. El rango de CBM de estas bacterias estuvo entre 32 y 64 mg/mL, respectivamente.

The aim of this research was to determine antibacterial activity of etanolic extract of the leaves and hexanoic extract obtained from fruits of Schinus molle L. (Anacardiaceae), grown in Italia. with a yield of 32,42 % and 5,63 %, respectively. Whatever type of extract and the plant part used, Schinus molle L., showed good antibacterial activity against Gram positive bacteria (S. aureus ATCC 29213 and E. faecalis ATCC 29212) with MIC 16 mg/mL. Range of MBC of these bacteria were between 32 and 64 mg/mL respectively.

Human monocytes tolerant to LPS retain the ability to phagocytose bacteria and generate reactive oxygen species

Tolerance to lipopolysaccharide (LPS) occurs when animals or cells exposed to LPS become hyporesponsive to a subsequent challenge with LPS. This mechanism is believed to be involved in the down-regulation of cellular responses observed in septic patients. The aim of this investigation was to evaluate LPS-induced monocyte tolerance of healthy volunteers using whole blood. The detection of intracellular IL-6, bacterial phagocytosis and reactive oxygen species (ROS) was determined by flow cytometry, using anti-IL-6-PE, heat-killed Staphylococcus aureus stained with propidium iodide and 2',7'-dichlorofluorescein diacetate, respectively. Monocytes were gated in whole blood by combining FSC and SSC parameters and CD14-positive staining. The exposure to increasing LPS concentrations resulted in lower intracellular concentration of IL-6 in monocytes after challenge. A similar effect was observed with challenge with MALP-2 (a Toll-like receptor (TLR)2/6 agonist) and killed Pseudomonas aeruginosa and S. aureus, but not with flagellin (a TLR5 agonist). LPS conditioning with 15 ng/mL resulted in a 40 percent reduction of IL-6 in monocytes. In contrast, phagocytosis of P. aeruginosa and S. aureus and induced ROS generation were preserved or increased in tolerant cells. The phenomenon of tolerance involves a complex regulation in which the production of IL-6 was diminished, whereas the bacterial phagocytosis and production of ROS was preserved. Decreased production of proinflammatory cytokines and preserved or increased production of ROS may be an adaptation to control the deleterious effects of inflammation while preserving antimicrobial activity.

In vitro antibacterial activity of Psidium guajava Linn. leaf extract on clinical isolates of multidrug resistant Staphylococcus aureus.

In the present study, antibacterial activity of aqueous and organic extracts of Psidium guajava leaves was evaluated against multidrug resistant (MDR) clinical isolates of Staphylococcus aureus strains collected from hospitals in northern (Malabar region) Kerala. The strains which exhibited resistance against all the antibiotics tested was selected for antibacterial assays. Minimum inhibitory concentration (MIC) for methanolic and aqueous extracts was found to be 625 ug/ml and 7.5 mg/ml, respectively. Minimum bactericidal concentration (MBC) recorded for methanolic and aqueous extracts was 1.25 and 12.5 mg/ml, respectively. Methanolic extract at minimum bactericidal concentration inhibited the growth of MDR strain by 80%. Time-kill assay revealed that methanolic extract (4 mg/ml) killed MDR bacteria within 10 hr. Total polypeptide profiling of bacterial cultures by SDS-PAGE indicated a high degree of protein degradative activity of the extract. Finally, a human RBC based haemolytic assay showed absence of haemolysis even at concentrations higher than that of MBC, advocating thereby its safety in therapeutic use.

A rapidly fatal case of Panton-valentine leukocidin positive Staphylococcus aureus necrotizing pneumonia in an HIV-infected patient.

This article reports a rare case of necrotizing pneumonia caused by Panton-Valentine leukocidin (PVL) positive Staphylococcus aureus in an HIV-infected patient presenting with severe back pain and rash. The back pain progressed to excruciating abdominal pain which was misleading, resulting in an investigation on intraabdominal conditions. He developed massive hemoptysis and died within 2 days of the first clinical symptoms. Recognizing the emergence of PVL-producing S. aureus is important in both immunocompetent and immunocompromised patients. This organism was transmitted from his wife.

Staphylococcus aureus: aspectos biológicos e patogênicos / Staphylococcus aureus: biological and pathogenic aspects

Na atualidade o gênero Staphylococcus abrange aproximadamente 42 espécies, sendo que destas, 20 são de interesse médico e veterinário, uma vez que, estão associadas a uma variedade de infecções oportunistas em seres humanos e animais. Dentre essas espécies causadoras de enfermidades, o Staphylococcus aureus requer especial atenção devido a seu alto potencial patogênico e também a sua capacidade de desenvolver resistência aos antimicrobianos utilizados rotineiramente na prática clínica, estando desta forma, associado a um amplo espectro de doenças que variam desde lesões cutâneas superficiais até infecções sistêmicas graves.

Prevalence of Inducible Clindamycin Resistance in Staphylococcal Isolates at a Korean Tertiary Care Hospital

Clindamycin resistance in Staphylococcus species can be either constitutive or inducible. Inducible resistance cannot be detected by the conventional antimicrobial susceptibility test. In this study, we determined the prevalence of inducible clindamycin resistance in staphylococcal isolates at a Korean tertiary care hospital. Between February and September 2004, 1,519 isolates of Staphylococcus aureus and 1,043 isolates of coagulase-negative staphylococci (CNS) were tested for inducible resistance by the D-zone test. Overall, 17% of MRSA, 84% of MSSA, 37% of MRCNS, and 70% of MSCNS were susceptible to clindamycin. Of the erythromycin non-susceptible, clindamycin-susceptible isolates, 32% of MRSA, 35% of MSSA, 90% of MRCNS, and 94% of MSCNS had inducible clindamycin resistance. Inducible clindamycin resistance in staphylococci was highly prevalent in Korea. This study indicates importance of the D-zone test in detecting inducible clindamycin resistance in staphylococci to aid in the optimal treatment of patients.

Antibacterial activity of Ocimum sanctum L. fixed oil.

Ocimum sanctum fixed oil showed good antibacterial activity against Staphylococcus aureus, Bacillus pumilus and Pseudomonas aeruginosa, where S. aureus was the most sensitive organism. Sesame and soyabean oils also showed moderate activity against S. aureus. Higher content of linolenic acid in O. sanctum fixed oil could contribute towards its antibacterial activity. The antibacterial activity combined with anti-inflammatory and analgesic activities of the oil, could make it useful in inflammatory disorder resulting from staphylococcal infection.

Evaluation of phytochemical and antimicrobial properties of leaf extract of Tapinanthus sessilifolius (P. Beauv) van Tiegh.

Leaf extracts of T. sessilifolius growing on five different host plants (Psidium guajava, Citrus lemon, Vernonia amygdalina, Persea americana and Jatropa curcas) were evaluated for antimicrobial activity of the plant. Powdered leaves of T. sessilifolius collected from each host plant was divided into two portions. One portion was used for aqueous infusion and the other portion was successively extracted with hexane, ethylacetate and methanol. Infusion of aqueous extract of powdered leaves did not show antimicrobial effect even at the concentration of 1000 and 2000 microg/ml on test microorganisms (Staph. aureus, E. coli, Bacillus subtilis, Pseudomonas aeruginosa and Candida albicans). However in broth culture, methanolic and hexane extract had MIC range of 62.5-500 microg/ml and ethylacetate extract had 250-500 microg/ml. Phytochemical screening of leaf samples of T. sessilifolius collected from different host plants showed positive test for hydrolysable tannins, saponins, flavonoids, terpenes, cardiac glycoside, reducing sugars and proteins. LD50 concentration was found to be > 1.500 mg/kg for samples from P. guajava; 489.89 mg/kg for J. curcas and C. lemon; and 692 mg/kg for V. amydalina in mice.

Bacterial Growth in Amniotic Fluid Is Dependent on the Iron-Availability and the Activity of Bacterial Iron-Uptake System

In the present study, the relationship among iron-availability, antibacterial activity, role of meconium as an iron source and the activity of bacterial iron-uptake system (IUS) for bacterial growth in amniotic fluid (AF) were investigated. Staphylococcus aureus ATCC 6538 and its streptonigrin-resistant (SR) mutant with defective IUS were used as the test strains. The growth of S. aureus in AF was stimulated dosedependently by addition of meconium. Bacterial growth stimulated by meconium was re-inhibited dose-dependently by addition of iron-chelator, dipyridyl and apotransferrin. Iron concentration was correlated with the meconium content in AF (r(2)= 0.989, p=0.001). High-affinity IUS of S. aureus was expressed only in AF but not in AF with meconium. The growth of SR strain was more retarded than that of the parental strain in the iron-deficient brain heart infusion (ID-BHI), clear AF and AF containing apotransferrin. The retarded growth of both strains in the ID-BHI and AF was recovered by addition of holotransferrin, hemoglobin and FeCl3. Taken together, the antibacterial activity of AF is closely related with low iron-availability. Bacterial growth in AF considerably depends on the activity of bacterial IUS. Meconium acts as one of the exogenous iron-sources and thus can stimulate bacterial growth in AF.

Bioavailability of rifampicin following concomitant administration of ethambutol or isoniazid or pyrazinamide or a combination of the three drugs.

BACKGROUND & OBJECTIVES: Poor bioavailability of rifampicin (R) in combination with other anti-tuberculosis drugs such as isoniazid (H), pyrazinamide (Z), and ethambutol (E) is a subject of much concern for the last few decades. This could be due to an interaction between R and other drugs. An investigation was therefore undertaken to examine the bioavailability of R in the presence of H, Z and E or a combination of the three drugs. METHODS: The study included eight healthy volunteers, each being investigated on four occasions at weekly intervals once with R alone and with three of the four combinations on the three remaining occasions. A partially balanced incomplete block design was employed and the allocation of R or the drug combinations was random. Plasma concentrations of R at intervals up to 12 h were determined by microbiological assay using Staphylococcus aureus as the test organism. The proportion (%) dose of R as R plus desacetyl R (DR) in urine excreted over the periods 0-8 and 8-12 h was also determined. Bioavailability was expressed as an index (BI) of area under time concentration curve (AUC) calculated from the plasma concentrations or proportion of dose of R excreted as R plus DR in urine with the combinations to that with R alone. RESULTS: The bioavailability indices based on AUC were 0.96 with RE, 0.76 with RH, 1.08 with RZ and 0.65 with REHZ. The indices based on urine estimations (0-8 h) were similar, the values being 0.94, 0.84, 0.94 and 0.75, respectively. A second investigation revealed that the decrease of bioavailability of R with H was not due to the excipients present in H tablets. INTERPRETATION & CONCLUSION: Isoniazid alone or in combination with E and Z reduces the bioavailability of R. Urinary excretion data offer a simple and non invasive method for the assessment of bioavailability of R.

Modified antimicrobial disc susceptibility testing for nutritionally-variant streptococci.

Streptococci that were dependent for their growth upon staphylococci were isolated from a patient with sub-acute bacterial endocarditis and subsequently identified as nutritionally-variant streptococci (NVS). Failure of the isolate to grow on agar media supplemented with pyridoxal hydrochloride or L-cysteine, the known supporting growth factors for NVS, made conventional antimicrobial disc diffusion assay impossible. We modified the assay by co-inoculating Staphylococcus aureus resistant to the drugs being tested as a helper to support the growth of the NVS. Streaking S. aureus closely to the antibiotic discs that were placed above NVS resulted in the growth of satellite colonies of NVS that orbited the S. aureus and that produced a pattern of interrupted zones of growth inhibition. Using an alternative method--adding staphylococcal secreting factor(s) to a 10% staphylococcal cell-free culture supernatant and adding this to an antibiotic susceptibility testing medium,--we found that the NVS formed colonies that formed clear zones of growth inhibition around the disc. When the sizes of the growth inhibition zones produced by both these methods were compared with those recommened by the NCCLS, the NVS were found to be susceptible to penicillin, vancomycin, erythromycin, chloramphenicol, cefoperazone, cefamandole and ofloxacin and resistant to co-trimoxazole, gentamicin and tetracycline. Based on these findings, vancomycin was selected for treatment and the patient was cured of endocarditis. The correlation between the in vitro drug susceptibility testing and the in vivo clinical response indicated that the modified antibiotic susceptibility test is an appropriate method for establishing antibiotic regimens.

In vitro anti-oxidant property of protein-A of Staphylococcus aureus.

Protein-A (PA) is a cell-surface glycoprotein of S. aureus Cowan I with immunomodulatory and anti-tumor activities, and ability to ameliorate cyclophosphamide and carbontetrachloride (CCl4) induced toxicity in rodents. The likely mechanism of this effect appears to be the anti-oxidant property of PA, evidenced in the present study by inhibition of CCl4 and Fe2-ascorbate induced lipid peroxidation in rat liver homogenates and inhibition of deaminative-oxidative degradation of L-glutamate into 2-thiobarbituric acid reactive products in a constituted chemical system. The anti-oxidant property of PA seem to arise from its molecular characteristics and the ability to interact with a superoxide derived free-radical species without any affinity for superoxide anion, hydroxyl radical and singlet oxygen species.