Comparative evaluation of aggressiveness traits in staphylococcal strains from severe infections versus nasopharyngeal carriage.

Despite their commensal status, staphylococci can become problematic pathogens expressing multiple and redundant virulence factors. This study aimed to evaluate aggressiveness markers comparatively in staphylococcal strains isolated from severe infections versus asymptomatic carriage in order to identify clinically relevant bacterial traits that could easily be detected in clinical practice and could be suggestive for particular host-pathogen interactions such as cyto-adhesion or biofilm formation, ultimately orienting the clinical decision-making process. We have used in vitro phenotypic methods to assess adhesion to and invasion of eukaryotic cells, biofilm development, and expression of soluble virulence factors in 92 Staphylococcus spp. strains. The adhesion index, invasion capacity, biofilm formation and expression of soluble factors did not differ significantly between clinical and commensal strains. The major bacterial traits we found to be significantly more prevalent in clinical staphylococci were the aggregative adhesion pattern (P = 0.012), cluster adhesion (P = 0.001) and tetrad morphology (P = 0.018). The aggregative adhesion pattern was correlated with higher cyto-adhesion (P < 0.001), higher invasion capacity (P = 0.003) and lower Carmeli scores (P = 0.002). Three major bacterial traits, namely tetrad morphology, aggregative adhesion pattern, and resistance to methicillin (acronym: TAM), can be used to compute an aggressiveness score (SAS) predictive of the staphylococcal strain's virulence and capacity to initiate and develop a biofilm-driven chronic infectious process versus a fulminant acute infection, in a susceptible host.

[Study of Streptococcus pneumoniae strains resistant to antibiotics analyzed at "Cantacuzino" NIRDMI during 2006-2008]. / Studiul tulpinilor de Streptococcus pneumoniae rezistente la antibiotice analizate la INCDMI "Cantacuzino" în perioada 2006-2008.

OBJECTIVE: The aim of the this study was the analysis of the resistance to antibiotics of Streptococcus pneumoniae isolated in last years. METHODS: 328 S. pneumoniae strains, coming from blood, CSF tracheal aspirate (TA), or sputum, pleural fluid (PL) and other samples (ear and sinus fluid) isolated in 2006-2008, were analyzed at INCDMI "Cantacuzino", National Reference Center for Streptococcus pneumoniae. Strains were tested for susceptibility to by agar diution method (minimal inhibitory concentration-MIC) to the following antibiotics: penicillin (Pc), erythromycin (Em), cephalothin (Kf). cefuroxim (Cxm), cefotaxim (Ctx), trimethoprim/sulfamethoxazol (Sxt), ofloxacin (Ojx), amoxicillin (Amx). tetracycline (Te), cloramphenicol (Cm), vancomycin (Va). RESULTS: The analysis of the results was done according to CLSI 2009. Pneumococci strains isolated from blood, CSF, TA or sputum and PL showed lower resistance level to antibiotics (38.8% Pc, 9.3% Cxm. 4.1% Ctx, 2.7% Amx. 24% Em, 2.4% Ofx, 68% Sxt) against those isolated from ear ans sinus fluid which revealed high levels of resistance (70% Pc, 11.2 % Cxm, 5.9 % Ctx, 3.4% Amx, 58.4 % Em. 3.8% Ofx, 73% Sxt). Strains resistant to penicillin, isolated from blood and CSF revealed the following aspects: 17% low level of resistance and 11 % high level of resistance. CONCLUSIONS. The most efficient antibiotics were Ctx, Amx and Oft. A continuous surveillance of pneumococci strains resistant to antibiotics is needed, as well as the use of an pneumococcal efficient vaccine.

[Antibiotic resistance of Gram-positive cocci isolated in 2008]. / Rezistenta la antibiotice a cocilor Gram pozitivi izolati în 2008.

OBJECTIVE: Antibiotic resistance evaluation of Gram-positive cocci isolated in 2008. MATERIAL AND METHODS: Antibiotic susceptibility testing was performed for 1044 strains: 610 Staphylococcus aureus (352 from patients, 258 from carriers), 203 Streptococcus pneumoniae (53 from patients, 150 from carriers), 144 Enterococcus faecalis. 57 Enterococcus faecium and 30 Streptococcus spp. using automatic systems Vitek 2 Compact. MicroScan, disc diffusion method and Etest according to 2008 CLSI. A number of 497 Streptococcus pyogenes strains were tested for eritromycin resistance. RESULTS: There were 33.2% MRSA for strains isolated from patients and 30.0% from carriers. From MRSA strains. 35.5% were resistant to gentamicin. 33.6% to ciprofloxacin, 74.3% to erythromycin and 30.5% to rifampin. There were no S. aureus strain resistant to vancomycin and linezolid. S. aureus strains isolated from wounds were more resistant to erythromycin (43.9%) than the strains isolated from systemic infections (12.1%). From 11 S. pneumoniae strains isolated from meningitis, 4 were resistant to penicillin. Neither S. pneumoniae strain isolated from other infections, nor those from carriers had MIC to penicillin more than 4 microg/ml. S. pneumoniae strains isolated from carriers were more resistant to erythromycin. clindamycin and tetracycline than the strains isolated from patients (66.7%, 54.1%, 54.2% vs. 27.4%, 22.6%, 33.9%). E. faecium was 95.9% resistant to penicillin, 90.2% to ampicillin, 64.7% to gentamicin, 72.0% to streptomycin and 78.4% to ciprofloxacin. F. faecalis was less resistant than E. faecium at most of the antibiotics: 32.4% to gentamicin, 59.6% to streptomycin, 28.5% to ciprofloxacin. Viridans group Streptococci, all isolated from blood culture were 92% susceptible to penicillin and ampicillin. To erythromycin, 12% of viridians group Streptococci were resistant. S. pyogenes resistance to eritromycin was 5.8%. CONCLUSIONS: S. aureus strains showed a relatively high level of resistance to oxacillin (33.2%) and resistance in the same time to several antibiotics. S. pneumoniae can not be considered resistant to penicillin administrated parenteral, with exception of the strains isolated from meningitis. E. faecium had a higher resistance rate than E. faecalis.

[Incidence and resistance patterns of pathogens from lower respiratory tract infections (LRTI)]. / Incidenta si pattern-ul de rezistenta bacteriilor patogene izolate din tractul respirator inferior.

The aim of present study was to evaluate the incidence and antibiotic susceptibility of pathogens in LRTI for patients in ICU/Surgery and pneumological wards from Marius Nasta Institute. A number of 938 strains isolated between September 1st 2004 and September 1st 2005 were identified by standard procedures and antimicrobial resistance was determined following CLSI approved standard. Imipenem-EDTA Double Disk Synergy test and Etest were used for detection of metallo-beta-lactamase producing isolates of P.aeruginosa. There were isolated 744 Gram-negative strains: H. influenzae 34.6%, P. aeruginosa 17.7%, H. parainfluenzae 15.9%, K. pneumoniae 8.6% and another spp. and 194 Gram-positive strains: 54.1% S.aureus and 45.9% S.pneumoniae. Among H. influenzae and H. parainfluenzae isolates, the highest resistance rate was to trimethoprim/sulfametoxazole (SXT 30.9% and 31.1%), followed by ampicillin (AMP 11.6% and 13.4%), chloramphenicol (C 4.5% and 5.1%) and clarithromycin (1.6% and 13.6%). P. aeruginosa strains showed a resistance rate between 7.9% to amikacin and 38.3% to cefoperazone. The resistance to imipenem (IPM) and meropenem (MEM) was close: 28.2% and 26.0%. From 36 P. aeruginosa IPM and multidrug resistant strains tested, 8 were probably producing metallo-beta-lactamase. For S. aureus the highest resistance rate was to penicillin 93.3% followed by erythromycin (E 45.7%), oxacillin 41.9% and CIP (33.3%); all strains were susceptible to vancomycin, teicoplanin and linezolid. From S. pneumoniae strains 13.4% were high resistant to penicillin and 39.3% were intermediate resistant. The resistance rate for other antibacterial agents was 64.0% to SXT, 18.8% to E, 8.3% to C and all strains were susceptible to levofloxacin. K. pneumoniae strains were resistant to cefepime (11.3%), CIP (7.8%) and there was no resistant strain to IPM and MEM.

[Bacteria isolated from pleural fluid and their resistance to antimicrobials]. / Bacterii izolate din lichidul pleural si rezistenta lor la antibiotice.

The aim of this study is to evaluate the frequency of microorganisms isolated from pleural fluids and their resistance to antimicrobial agents. A total of 272 pleural fluids were studied between July 2004 - July 2005 from the patients hospitalized in ICU/surgery (127) and respiratory diseases wards (145) at Marius Nasta Institute. The laboratory investigations included: direct microscopy, cultures for aerobic and anaerobic bacteria, identification, disk diffusion method according with CLSI recommendations for resistance and Etest for detection of metallo-beta-lactamase producing isolates of Pseudomonas aeruginosa. Microorganisms were isolated from 159 samples (58.4%), 48 pleural fluids were positive only in microscopy (17.6%). The most frequent isolated strain was P. aeruginosa (49.6%), followed by Staphylococcus aureus (12.8%) and Enterobacteriaceae (11.2%) polymicrobial infections were mostly due to combinations of Pseudomonas with Enterobacteriaceae. For P. aeruginosa the resistance rate was higher than 71% for all beta-lactams. For aminoglycosides the lower resistance rate was to amikacin (18.0%). For quinolones, resistance of P. aeruginosa was 67.8% to ciprofloxacin. P. aeruginosa isolated from patients hospitalized in ICU/surgery were more resistant to some antimicrobials than the strains isolated in the respiratory diseases wards: resistance to amikacin was 24.5% versus 10% respectively. From 21 P. aeruginosa imipenem and multidrug resistant strains tested, 3 were probably producing of metallo-beta-lactamase. S. aureus showed 47.1% oxacillin resistance, 38.9% resistance to gentamicin and ciprofloxacin and 27.7% to erythromycin. All S.aureus strains were susceptible to linezolid, teicoplanin and vancomycin. The resistance of Enterobacteriaceae strains was high to ampicillin (80.0%), amoxicillin/clavulanic acid and trimethoprim/sulfamethoxazole e(57.6%); the lowest resistance rate was to cefoperazone/sulbactam (7.7%) and to imipenem and ciprofloxacin (10.8%).