Comparison of Austrian, Hungarian and Macedonian methicillin-resistant and methicillin-sensitive Staphylococcus aureus strains in relation to prevalence of cytotoxin genes.

Cytotoxin genes in 128 Austrian (AT) MSSA, 48 MRSA, 94 Hungarian (HU) MSSA, 110 MRSA and 67 Macedonian (MK) MSSA, 81 MRSA strains were examined. The presence of alfa-haemolysin gene (hla) was more common in HU MSSA strains compared to AT and MK (99%, 86%, 72%: p<0.001). AT and MK MRSA harboured hlb genes more frequently compared to HU (60%, 62%, 33%: p<0.001). HU and MK MRSA strains carried gamma-haemolysin gene (hlg) in higher percentage in contrast to AT (88%, 83%, 69%: p=0.01). Haemolysin gamma-variant gene (hlgv) was more prevalent in HU MSSA compared to AT and MK (84%, 56%, 69%: p<0.001). Panton-Valentine leukocidin genes were found only in AT, HU, MK MSSA and MK MRSA in 2.3%, 4%, 1.5% (p=0.53) and 1% (p=0.38), respectively. The 3-gene combination pattern comprising of hla, hlg and hld genes showed increased prevalence among AT MSSA compared to HU (27%, 11%: p<0.001). The 4-gene pattern composed of hla, hlg, hlgv and hld genes was significantly characteristic for HU MRSA in contrast to AT and MK MRSA (56%, 12.5%, 27%: p<0.001). Frequency of certain cytotoxin genes and combinations differed significantly in Staphylococcus aureus strains according to geographical origin and methicillin-resistance.

In vitro efficiency of vancomycin containing experimental drug delivery systems.

Biofilm-forming Staphylococcus epidermidis strains are common cause of the periprosthetic infection. The treatment of the periprosthetic infection is very problematic, so the prevention of these infections by an antibiotic containing prothesis could be an option for prevention.The purpose of the present study was to examine the in vitro effects of drug delivery systems (DDSs), namely Wax 1 and Wax 2 with different vancomycin content: 0.5, 1, 2 and 4 mg. In order to control the antibacterial activity of DDSs killing curve study was performed and in order to determine the antibiotic release and the antibiotic peak concentration from the DDSs biological assay was carried out.The time kill curve studies showed, that both DDSs with all vancomycin concentration decreased significantly the bacterial counts, however, Wax 2 with 4 mg vancomycin significantly decreased the bacterial count than all the other groups.The vancomycin release was the best with the highest peak concentration from DDSs with 4 mg vancomycin contain; it was significantly better than in the other groups, however, no significant difference was observed between Wax 1 and Wax 2 in this respect.These findings suggest that Wax 2 with 4 mg vancomycin content could be a potential agent for clinical use.

In vitro activity of clarithromycin in combination with other antimicrobial agents against biofilm-forming Pseudomonas aeruginosa strains.

The aim of the study was to investigate the biofilm-production of 60 Pseudomonas aeruginosa strains isolated from clinical samples and to examine the effect of different antimicrobials and their combinations with clarithromycin on biofilm-formation. The minimal inhibitory concentrations (MICs), minimal biofilm inhibitory concentrations (MBICs), and antibiotic synergy by calculating the fractional inhibitory concentration (FIC) index were determined for the following antibiotics: ceftazidime, cefepime, piperacillin/tazobactam, imipenem, meropenem, levofloxacin, ciprofloxacin, gentamicin, amikacin, tobramycin, netilmicin and clarithromycin. A total of 14 (23.3%) isolates out of 60 isolates of P. aeruginosa were biofilm positive. Cefepime, imipenem and meropenem had the lowest MIC 90 values. Piperacillin/tazobactam and clarithromycin had the highest MIC 90 values. Imipenem, meropenem, piperacillin/tazobactam and clarithromycin had the lowest MBIC 90 values. For biofilm-forming P. aeruginosa strains 2-fold to 128-fold higher MBIC values than MIC values were obtained for ceftazidime, cefepime, imipenem, amikacin and netilmicin. The MBIC was 2-fold to 512-fold lower then the MIC values in the case of piperacillin/tazobactam, ciprofloxacin, levofloxacin and clarithromycin. Synergy was generally demonstrated for clarithromycin in combination with aminoglycosides, fluoroquinolones or ceftazidime. However, surprisingly it was found that combinations of clarithromycin with carbapenems or cefepime led to an antagonistic interaction: combination of clarithromycin with imipenem, meropenem or ertapenem showed antagonism in 37.5%, 50% and 62.5% of the strains tested whereas its combination with cefepime expressed antagonism in 75% of the strains, respectively. To the best of our knowledge no one has previously described this phenomenon so far.