[About microbiological methods for detection of oxacillin resistance in coagulase-negative staphylococci]. / Sobre los métodos microbiológicos para la detección de la resistencia a oxacilina en Staphylococcus coagulasa negativos.

OBJECTIVE: Coagulase-negative staphylococci (CoNS) take part of the human skin and mucous membranes, but they are also involving in infections with the increasing use of prosthetic, indwelling devices or intravascular catheter-related bacteraemia. They are more resistance than Staphylococcus aureus against a wide range of antimicrobial agents, and it have been observed an increase in morbidity and mortality of patients with incorrect treatment. METHODS: To analyze the results obtained by different commercial techniques: two automatic microdilution systems (MicroScan and Vitek2 Compact), PBP2a agglutiation test, with and without 1 µg oxacillin disk induction, and detection of mecA gene by nucleic acids amplification techniques, for the diagnosis of methicillin resistance staphylococci in 170 strains of CoNS isolated from blood cultures. RESULTS: One hundred and seventy methicillin resistance staphylococci were detected by MicroScan, 167 strains by Vitek 2 Compact, 115 strains were PBP2a positive without oxacillin induction and 168 after oxacillin induction. Finally, 167 strains were mecA gene positive detected by nucleic acids amplification techniques. CONCLUSIONS: It is necessary to do oxacillin induction before PBP2a test to avoid false negatives. There are a great variability in the phenotypic expression of methicillin resistance in CoNS.

Mycobacterium africanum, an emerging disease in high-income countries?

BACKGROUND: Mycobacterium africanum is a cause of tuberculosis (TB) that has mainly been described in Africa, but immigration and travel patterns have contributed to the spread of the disease to other countries. METHODS: We retrospectively reviewed TB cases due to M. africanum during 2000-2010 in seven Spanish hospitals. Selected clinical charts were reviewed using a predefined protocol that included demographical, clinical and microbiological data and outcome. RESULTS: Although 57 cases were diagnosed, only 36 clinical charts were available for review: 82.8% were men and the mean age was 31.6 years (range 12-81). Forty-four cases were from Africa, 1 from the Philippines, 1 from India, and 4 from Spain, while the country of origin was unknown in 7 cases. The most frequent site of infection was the lung (58.3%). Four cases (6.9%) were resistant to at least one first-line anti-tuberculosis drug. CONCLUSIONS: Disease due to M. africanum in industrialised countries is mainly associated with immigration from endemic areas, although some cases also occur among native-born populations.

Moxifloxacin and biofilm production by coagulase-negative staphylococci.

The in vitro activity of moxifloxacin against 41 strains of coagulase-negative staphylococci was determined. A relationship between the activity of moxifloxacin and biofilm formation was detected. Biofilm-producing strains were more resistant to moxifloxacin than biofilm-negative strains. Our global results obtained with six strains of Staphylococcus epidermidis showed that subinhibitory concentrations of moxifloxacin did not significantly modify biofilm formation. On the other hand, moxifloxacin concentrations of 2, 10, 50 and 100 x MIC produced a log decrease in viable count (included in a biofilm) of 0.20, 0.37, 1.10 and 1.69, respectively.

In vitro activity of allicin against Staphylococcus epidermidis and influence of subinhibitory concentrations on biofilm formation.

AIMS: The aim of this study is to determine the in vitro activity of allicin against Staphylococcus epidermidis and to evaluate the influence of allicin on biofilm formation. METHODS AND RESULTS: In vitro activity of allicin (diallyl thiosulphinate) against 38 strains of S. epidermidis was investigated. The activity of allicin was similar against S. epidermidis methicillin susceptible and methicillin resistant strains [minimum inhibitory concentration (MIC)90=8 mg l(-1)]. In general, subinhibitory concentrations (sub-MIC) of allicin diminished biofilm formation in the five strains analysed. CONCLUSION: The results confirm the antibacterial effect of allicin. Sub-MICs of allicin also diminished the biofilm formations by S. epidermidis. SIGNIFICANCE AND IMPACT OF THE STUDY: The present study shows that allicin is active in vitro against S. epidermidis and that sub-MICs of allicin may play a role in the prevention of adherence of this bacteria to medical devices.

Resistance to vancomycin, LY333328, ciprofloxacin and trovafloxacin of community-acquired and nosocomial strains of Enterococcus faecalis isolated in Badajoz (Spain) with and without high-level resistance to streptomycin and gentamicin.

In vitro resistance of community-acquired and nosocomial strains of Enterococcus faecalis isolated in Badajoz (Spain) were determined by a microdilution method. The isolates were identified with conventional MicroScan Pos Combo 4 I dehydrated panels. No resistance to glycopeptides was found, but LY333328 was 2-4 times more active than vancomycin. In the nosocomial strains, high-level resistance to streptomycin (HLRS) was 54.7%, and high-level resistance to gentamicin (HLRG) was 38.1%. Resistance to ciprofloxacin and trovafloxacin was 45.3 and 38.9%, respectively. In the community-acquired isolates, HLRS, HLRG, resistance to ciprofloxacin and resistance to trovafloxacin were 44.2, 17.3, 15.4 and 13.5%, respectively. Trovafloxacin was 2-4 times more active than ciprofloxacin against both groups of strains. An association between high-level resistance to aminoglycosides and resistance to fluoroquinolones was noted. The resistance to aminoglycosides did not influence the activity of vancomycin and LY333328.

[Pathogenicity of Enterococcus spp. Characteristics of 169 hospital isolates]. / Patogenicidad de Enterococcus spp. Características de 169 aislamientos hospitalarios.

BACKGROUND: To know the characteristics of Enterococcus spp. strains isolated in the hospital; to analyse the importance of this microorganism and its resistance to antimicrobial agents. PATIENTS AND METHODS: Retrospective analysis of the case histories of 169 patients with Enterococcus spp. isolates, selected at random at the Infanta Cristina Hospital in Badajoz. Investigation was carried out on: age, date of admission and discharge, clinical symptoms, risk factors, previous antibiotic treatment, clinical and microbiological evolution, recommended treatment and prescribed treatment. Identification of microorganisms and antibiogram with Pos Combo 41 microScam panels, read on Baxter WalkAway-40 equipment. RESULTS: The most frequently found species was Enterococcus faecalis. In 75 cases the isolations were polymicrobial. The enterococci were isolated mainly from urinary infections (27%), skin infections (20%), intrabdominal infections (14%) and infections from surgical wounds (14%). The existence of peripheral catheter was the main risk factor. All the strains of E. faecalis were susceptible to the glycopeptides. Two strains of Enterococcus faecium were not susceptible to vancomycin and one of these was not susceptible to teicoplanin. Mortality was from 21-27.5%. CONCLUSIONS: Enterococcus spp. is frequently isolated in nosocomial infections, although in approximately half the cases it is associated with other bacteria. For this reason, it is not always possible to determine its pathogenic contribution. The isolated strains, except two strains of E. faecium, are susceptible to vancomycin. A relation exists between high resistance to aminoglucosides and resistance to fluoroquinolones.