Molecular surveillance of macrolide, tetracycline and quinolone resistance mechanisms in 1191 clinical European Streptococcus pneumoniae isolates

Streptococcus pneumoniae isolates (n=1191) were collected during a 1997-1999 European surveillance study. In addition to susceptibility data, a molecular epidemiological survey of their mechanisms of resistance to macrolides, tetracyclines, and quinolones was provided. Of the isolates tested, 72.6% were penicillin-susceptible, 19.9% penicillin-intermediate and 7.5% penicillin-resistant. There was an obvious relationship between resistance to penicillin and resistance to erythromycin (19% of all isolates), clindamycin (14%) and tetracycline (23%). Only one isolate was resistant to levofloxacin. Seventy-three percent of the European S. pneumoniae isolates resistant to erythromycin (n=229) carried the erm(B) gene, while the remaining 27% possessed the mef(A) gene. No mutations were detected in 23S rRNA or in ribosomal proteins L4 and L22. All tetracycline-resistant isolates (n=277) carried the tet(M) gene; none carried the tet(O) gene. Classical mutations in gyrA (Ser 81-Phe or Tyr) and parC (Ser 79-Phe and Asp 83-Asn) and efflux contributed to the decreased quinolone susceptibility. This study of recent European S. pneumoniae isolates can be used to recognize any changes in susceptibility patterns and resistance mechanisms that may occur in the future.

Control of nosocomial multiresistant Enterobacteriaceae using a temporary restrictive antibiotic agent policy

An observational study on the epidemiology of multiresistant Enterobacteriaceae was conducted in the neurology and neurosurgery wards of a university hospital to determine the impact of hospital hygiene measures and an additional temporary restrictive antibiotic agent policy on the sudden rise in incidence of these bacteria. The incidence and prevalence of patients with multiresistant Enterobacteriaceae were assessed, and patient isolates were typed phenotypically and by random amplified polymorphic DNA analysis. All hospital hygiene measures implemented were recorded, and the influence of the restrictive policy on antibiotic use was analyzed. This policy consisted of a prior authorization requirement and the withdrawal of all antibiotics with a possible selective pressure on multiresistant strains (gentamicin, tobramycin, quinolones, cotrimoxazole, broad-spectrum penicillins, and cephalosporins). This ban left only carbapenems and amikacin for treatment. Typing showed that 17 of the 61 (28%) patients involved were infected or colonized with a single multiresistant strain of Klebsiella oxytoca, for which an environmental source was identified. The isolates recovered from the other patients comprised eight different species, and subsequent genotyping yielded a great variety of strains. The increased incidence could not be controlled with hospital hygiene measures alone. Only after implementation of the restrictive antibiotic policy did the epidemic strain vanish and the endemic incidence of multiresistant Enterobacteriaceae decrease to <50% of the level before intervention. In the years since, the incidence has remained at this low level, and the antibiotic costs have decreased to a level lower than before intervention.

Molecular detection of antimicrobial resistance

The determination of antimicrobial susceptibility of a clinical isolate, especially with increasing resistance, is often crucial for the optimal antimicrobial therapy of infected patients. Nucleic acid-based assays for the detection of resistance may offer advantages over phenotypic assays. Examples are the detection of the methicillin resistance-encoding mecA gene in staphylococci, rifampin resistance in Mycobacterium tuberculosis, and the spread of resistance determinants across the globe. However, molecular assays for the detection of resistance have a number of limitations. New resistance mechanisms may be missed, and in some cases the number of different genes makes generating an assay too costly to compete with phenotypic assays. In addition, proper quality control for molecular assays poses a problem for many laboratories, and this results in questionable results at best. The development of new molecular techniques, e.g., PCR using molecular beacons and DNA chips, expands the possibilities for monitoring resistance. Although molecular techniques for the detection of antimicrobial resistance clearly are winning a place in routine diagnostics, phenotypic assays are still the method of choice for most resistance determinations. In this review, we describe the applications of molecular techniques for the detection of antimicrobial resistance and the current state of the art.

Emergence, mechanism, and clinical implications of reduced glycopeptide susceptibility in Staphylococcus aureus

In order to understand the mechanism(s) of the resistance/reduced susceptibility of Staphylococcus aureus to glycopeptide antibiotics, the current data on the modes of action of glycopeptides were reviewed. In addition, the different test systems for detecting vancomycin resistance and the clinical relevance of resistant Staphylococcus aureus were analyzed. Finally, strategies to prevent the nosocomial spread of these bacteria are presented, as are new therapeutic options.

Novel gene cassettes and integrons

An increase in multiresistant Enterobacteriaceae was observed at one of the departments of the University Medical Center Utrecht. Nine different integrons and 17 gene cassettes were found, including the new gene cassette aadA8. This cassette was highly related to aadA3 and aadA2. In addition, an unknown promoter sequence was found for two integrons.

Epidemiology and susceptibility of 3,051 Staphylococcus aureus isolates from 25 university hospitals participating in the European SENTRY study

A total of 3,051 methicillin-susceptible Staphylococcus aureus (MSSA) isolates and methicillin-resistant S. aureus (MRSA) isolates in Europe were compared. MRSA isolates constituted 25% of all isolates and were more prevalent in southern Europe. MRSA isolates appeared to be more prevalent in intensive care units than in outpatient departments. Only a small minority of MSSA isolates were multidrug resistant, whereas the majority of MRSA isolates were multidrug resistant.

Increased prevalence of class I integrons in Escherichia coli, Klebsiella species, and Enterobacter species isolates over a 7-year period in a German university hospital

The prevalence of integrons in five enterobacterial species was analyzed in 900 blood culture isolates from 1993, 1996, and 1999. Remarkably, the prevalence increased from 4.7% in 1993 to 9.7% in 1996 and finally to 17.4% in 1999 (P < 0.01). Within 7 years the combined percentage of P1 strong promoters and P1 weak plus P2 active promoters with high transcription efficacies has increased from 23.1 to 33.3 and finally 60% (P < 0.05).

Frequency of isolation of pathogens from bloodstream, nosocomial pneumonia, skin and soft tissue, and urinary tract infections occurring in European patients

The frequency of isolation of pathogens that cause different types of infections is an important guide for empiric therapy. As part of the SENTRY Antimicrobial Surveillance Program, the frequency of isolation of different bacterial species from bloodstream, nosocomial pneumonia, skin and soft tissue, and urinary tract infections occurring in European patients was determined. A total of 15,704 isolates were collected in 1997 and 1998 from 24 university hospitals in 14 European countries: 9,194 from bloodstream, 2,052 from nosocomial pneumonia, 2,320 from skin and soft tissue, and 2,138 from urinary tract infections. More than 95% of all bacterial infections were caused by only 15 different genera. Staphylococcus spp. and Escherichia spp, accounted for more than 50% of the infectious isolates, with the exception of those obtained from cases of nosocomial pneumonia. In the latter type of infection, isolates belonging to these two genera were responsible for 30% of the infections. An analysis at the individual species level showed that Escherichia coli caused a large proportion of bloodstream and urinary tract infections (20.8% and 49.3% of isolates, respectively). Staphylococcus aureus was the main causative species for nosocomial pneumonia and skin and soft tissue infections (21.5% and 37.4% of isolates, respectively). In addition, Pseudomonas aeruginosa played an important role in all types of infection analyzed.

International surveillance of bloodstream infections due to Candida species: frequency of occurrence and in vitro susceptibilities to fluconazole, ravuconazole, and voriconazole of isolates collected from 1997 through 1999 in the SENTRY antimicrobial surveillance program

A surveillance program (SENTRY) of bloodstream infections (BSI) in the United States, Canada, Latin America, and Europe from 1997 through 1999 detected 1,184 episodes of candidemia in 71 medical centers (32 in the United States, 23 in Europe, 9 in Latin America, and 7 in Canada). Overall, 55% of the yeast BSIs were due to Candida albicans, followed by Candida glabrata and Candida parapsilosis (15%), Candida tropicalis (9%), and miscellaneous Candida spp. (6%). In the United States, 45% of candidemias were due to non-C. albicans species. C. glabrata (21%) was the most common non-C. albicans species in the United States, and the proportion of non-C. albicans BSIs was highest in Latin America (55%). C. albicans accounted for 60% of BSI in Canada and 58% in Europe. C. parapsilosis was the most common non-C. albicans species in Latin America (25%), Canada (16%), and Europe (17%). Isolates of C. albicans, C. parapsilosis, and C. tropicalis were all highly susceptible to fluconazole (97 to 100% at < or =8 microg/ml). Likewise, 97 to 100% of these species were inhibited by < or =1 microg/ml of ravuconazole (concentration at which 50% were inhibited [MIC(50)], 0.007 to 0.03 microg/ml) or voriconazole (MIC(50), 0.007 to 0.06 microg/ml). Both ravuconazole and voriconazole were significantly more active than fluconazole against C. glabrata (MIC(90)s of 0.5 to 1.0 microg/ml versus 16 to 32 microg/ml, respectively). A trend of increased susceptibility of C. glabrata to fluconazole was noted over the three-year period. The percentage of C. glabrata isolates susceptible to fluconazole increased from 48% in 1997 to 84% in 1999, and MIC(50)s decreased from 16 to 4 microg/ml. A similar trend was documented in both the Americas (57 to 84% susceptible) and Europe (22 to 80% susceptible). Some geographic differences in susceptibility to triazole were observed with Canadian isolates generally more susceptible than isolates from the United States and Europe. These observations suggest susceptibility patterns and trends among yeast isolates from BSI and raise additional questions that can be answered only by continued surveillance and clinical investigations of the type reported here (SENTRY Program).

Frequency of isolation and antimicrobial resistance of gram-negative and gram-positive bacteria from patients in intensive care units of 25 European university hospitals participating in the European arm of the SENTRY Antimicrobial Surveillance Program 1997-1998

A total of 3,981 isolates from patients treated at intensive care units were collected in 25 European university hospitals during 1997 and 1998 as part of the SENTRY Antimicrobial Surveillance Program. Overall, the most important species isolated were Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, coagulase-negative staphylococci (CNS), Enterobacter spp., Haemophilus influenzae, Streptococcus pneumoniae, and Enterococcus faecalis. Thirty-nine percent of all Staphylococcus aureus isolates were resistant to oxacillin. All Staphylococcus aureus isolates were fully susceptible to linezolid and vancomycin. Moreover, all CNS isolates were susceptible to vancomycin and minocycline. All Enterococcus faecalis isolates were susceptible to vancomycin, and 99% of these isolates were also susceptible to ampicillin. The antimicrobial agents most effective against Pseudomonas aeruginosa isolates were amikacin, piperacillin/tazobactam, meropenem, and cefepime, with 87, 85, 84, and 83% of isolates being susceptible, respectively. Escherichia coli isolates were fully susceptible to carbapenems, and at least 99% of these isolates were susceptible to ceftriaxone, cefepime, and amikacin. The Enterobacter spp. were also highly susceptible to carbapenems, amikacin, and cefepime, with 99, 97, and 96% of isolates being susceptible, respectively. Haemophilus influenzae was susceptible to most of the antibiotics tested. Only 68% of the pneumococcal isolates were fully susceptible to penicillin, yet 100% were susceptible to a number of fluoroquinolones and vancomycin. There are still sufficient treatment options for patients infected with the most important bacterial species involved in infections in intensive care units. However, the situation for patients with Pseudomonas aeruginosa infections is critical.

Multi-resistance to antimicrobial agents for the ten most frequently isolated bacterial pathogens

Cross-resistance and multi-resistance to selected antibiotics was determined for Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Pseudomonas aeruginosa, Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis. Amikacin-resistant Enterobacteriaceae often showed cross-resistance to ss-lactam antibiotics. Only 1% of the Escherichia coli isolates showed resistance to more than four antibiotics from a set of seven. This rate was higher for other Enterobacteriaceae and there were high levels of cross-resistance for P. aeruginosa. The cross-resistance of oxacillin with other antibiotics is well known in staphylococci. Penicillin-resistant pneumococcal isolates were cross-resistant to macrolides. Cross-resistance was only a minor problem in H. influenzae and M. catarrhalis. Cross- and multi-resistance are important problems for Gram-negative and Gram-positive bacteria but not for fastidious bacteria with the exception of penicillin-resistant S. pneumoniae.

In-vivo transfer of mecA DNA to Staphylococcus aureus [corrected]

Staphylococcus aureus is thought to have acquired mecA DNA by horizontal transfer. DNA fingerprints made by restriction nucleases that cut certain sequences of DNA are used to compare complete genomes or particular genes between bacteria. We isolated an epidemic mecA(-) meticillin-susceptible S aureus genotype and, subsequently, a rare isogeneic mecA(+) meticillin-resistant S aureus (MRSA) genotype from a neonate who had never been in contact with MRSA. This MRSA contained mecA DNA that was identical to that in a coagulase-negative staphylococcal strain isolated from this patient, but different from other MRSA genotypes. We believe that this MRSA was formed in vivo by horizontal transfer of the mecA DNA between two staphylococcal species.

Worldwide prevalence of antimicrobial resistance in Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis in the SENTRY Antimicrobial Surveillance Program, 1997-1999

The in vitro activities of numerous antimicrobials against clinical isolates of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis from patients with bloodstream and respiratory tract infections in the United States, Canada, Europe, Latin America, and the Asia-Pacific region were studied in the SENTRY Antimicrobial Surveillance Program. Penicillin resistance (minimum inhibitory concentration, > or =2 microg/mL) was noted in all 5 geographic regions, and a high and increasing rate of macrolide resistance among S. pneumoniae isolates was observed. Elevated rates of resistance to clindamycin, trimethoprim-sulfamethoxazole, chloramphenicol, and tetracycline were seen. beta-Lactamase-mediated resistance in H. influenzae to amoxicillin and variable trimethoprim-sulfamethoxazole resistance by region were documented. Resistance to several drugs continues to emerge among pneumococci worldwide, but more stable resistance patterns have been noted for H. influenzae and M. catarrhalis. Continued surveillance of this pathogen group appears to be prudent.

Bacterial resistance in urinary tract infections: how to stem the tide

Each year, approximately 10% of the population is diagnosed with a urinary tract infection (UTI). Escherichia coli is the most prevalent pathogen in UTIs but other species make significant contributions. UTIs are commonly treated with antibiotics and, therefore, a potential source for the emergence and/or selection of resistant bacteria. Although susceptibility to some antibiotics for a number of species is still high, resistance is an issue both for community- and hospital-acquired UTI. However, often treatment is empiric, especially in the community setting. This empiric treatment is often guided by inadequate information about the (local) rates of resistance, selection and emergence of resistance, although there is a general consensus that there is a relationship between antibiotic use and resistance. It is well known that some antibiotics, e.g., some fluoroquinolones, are able to induce mutations leading to resistance but the antibiotics prescribed also affect the commensal flora, potentially selecting resistant organisms. However, antibiotics meant to treat other infections may select uropathogens and, thereby, the risk for UTIs increases. The duration of treatment of any infection is an important factor to consider in this respect, as well as subinhibitory concentrations of the antibiotic prescribed. Prudent use of new and still effective antibiotics is required. Although prudent use of these antibiotics may help to reduce the prevalence of antibiotic-resistant uropathogens, elimination will be hard to achieve. Therefore, we believe, that we can reduce the tide but we will still have to deal with the resistance problem in the future.

Genetic relatedness of multidrug-resistant, methicillin (oxacillin)-resistant Staphylococcus aureus bloodstream isolates from SENTRY Antimicrobial Resistance Surveillance Centers worldwide, 1998

We reviewed Staphylococcus aureus bloodstream infection isolates from SENTRY centers worldwide during 1998 to evaluate the molecular epidemiology of multiply drug-resistant methicillin (oxacillin)-resistant S. aureus (MDR-MRSA). MDR-MRSA was defined as a S. aureus isolate with a MIC for oxacillin at >2 microg/ml and with four or more additional resistances. A total of 325 unique patient isolates of MDR-MRSA from five continents were analyzed using ribotyping and pulsed-field gel electrophoresis (PFGE). The frequency of MDR-MRSA among all S. aureus BSI isolates ranged from only 2.2% in Canada to 35.6% in the Asia-Pacific region. Forty-eight ribotypes (RT) were distinguished, but over 80% of the isolates were contained within the 10 most prevalent RTs. The most common RT, RT 184.5, which included 30% of all MDR-MRSA, was found on four of five continents. PFGE provided superior discrimination and identified numerous clusters of possible clonal dissemination of MDR-MRSA within individual medical centers and between institutions that are in geographic proximity. In four instances, strains with indistinguishable PFGE patterns were found on more than one continent. The predominant PFGE subtype in South America (RT 893.5/Ia) was isolated from patients at centers in Brazil, Argentina, and Portugal, and closely related subtypes were isolated in Chile and Italy. There is great geographic variation in rates of methicillin- and multidrug-resistance among S. aureus bloodstream isolates worldwide. Although many MDR-MRSA strains group geographically, a few closely related epidemic strains have wide regional and even global range.

In vitro development of resistance to six quinolones in Streptococcus pneumoniae, Streptococcus pyogenes, and Staphylococcus aureus

Streptococcus pneumoniae, Streptococcus pyogenes, and Staphylococcus aureus isolates were exposed to subinhibitory MICs of ciprofloxacin, sparfloxacin, gatifloxacin, moxifloxacin, clinafloxacin, and gemifloxacin during a 10-day period. Subculturing led to resistance development, regardless of the initial potencies of the quinolones. None of the quinolones was associated with a significantly slower rate of resistance development.

Detection of Candida spp. in blood cultures using nucleic acid sequence-based amplification (NASBA)

Candida spp. are the main causes of fungal infections in immunocompromised patients. It is known, that the routinely used automated blood culture systems may fail to detect yeasts. We therefore investigated, whether Nucleic Acid Sequence-Based Amplification (NASBA) can be used to improve the detection rate of Candida spp. in blood cultures. Culture-positive as well as negative blood cultures from patients with a proven candidaemia were analyzed, and the results of BacT/Alert monitoring were compared with the results of NASBA-based detection of yeast RNA. With the NASBA-assay, the number of positive blood cultures increased from 21% to 34%. The NASBA-assay may confirm the diagnosis and demonstrate the need for prolonged treatment. In addition it may shorten the time to detection. In summary, using NASBA for the detection of yeast RNA in blood cultures, we have shown for the first time that it is possible to improve the detection rate of yeasts in blood cultures by using amplification technology.

Development of resistance to ciprofloxacin, rifampin, and mupirocin in methicillin-susceptible and -resistant Staphylococcus aureus isolates

A relationship between resistance to methicillin and resistance to fluoroquinolones, rifampin, and mupirocin has been described for Staphylococcus aureus. Differences in resistance rates may be explainable by a higher spontaneous mutation rate (MR) or a faster development of resistance (DIFF) in methicillin-resistant S. aureus (MRSA). No differences in MR, DIFF, and mutations in grlA and gyrA were detected between methicillin-susceptible S. aureus and MRSA. The higher resistance rates in MRSA are not the result of hypermutability of target genes or a faster emergence of different mutations and may be the consequence of clonal spread of multiresistant MRSA.

Molecular surveillance of European quinolone-resistant clinical isolates of Pseudomonas aeruginosa and Acinetobacter spp. using automated ribotyping

Nosocomial isolates of Pseudomonas aeruginosa and Acinetobacter spp. exhibit high rates of resistance to antibiotics and are often multidrug resistant. In a previous study (D. Milatovic, A. Fluit, S. Brisse, J. Verhoef, and F. J. Schmitz, Antimicrob. Agents Chemother. 44:1102-1107, 2000), isolates of these species that were resistant to sitafloxacin, a new advanced-generation fluoroquinolone with a high potency and a broad spectrum of antimicrobial activity, were found in high proportion in 23 European hospitals. Here, we investigate the clonal diversity of the 155 P. aeruginosa and 145 Acinetobacter spp. sitafloxacin-resistant isolates from that study by automated ribotyping. Numerous ribogroups (sets of isolates with indistinguishable ribotypes) were found among isolates of P. aeruginosa (n = 34) and Acinetobacter spp. (n = 16), but the majority of the isolates belonged to a limited number of major ribogroups. Sitafloxacin-resistant isolates (MICs > 2 mg/liter, used as a provisional breakpoint) showed increased concomitant resistance to piperacillin, piperacillin-tazobactam, ceftriaxone, ceftazidime, amikacin, gentamicin, and imipenem. The major ribogroups were repeatedly found in isolates from several European hospitals; these isolates showed higher levels of resistance to gentamicin and imipenem, and some of them appeared to correspond to previously described multidrug-resistant international clones of P. aeruginosa (serotype O:12) and Acinetobacter baumannii (clones I and II). Automated ribotyping, when used in combination with more discriminatory typing methods, may be a convenient library typing system for monitoring future epidemiological dynamics of geographically widespread multidrug-resistant bacterial clones.

In vitro potency of moxifloxacin, clinafloxacin and sitafloxacin against 248 genetically defined clinical isolates of Staphylococcus aureus

The in vitro potency of three newer fluoroquinolones, moxifloxacin, clinafloxacin and sitafloxacin was tested against 248 genetically defined Staphylococcus aureus isolates, comprising 116 unrelated S. aureus, seven heterogeneous intermediate vancomycin-resistant S. aureus strains as well as 125 clonally related methicillin-resistant S. aureus. All strains were susceptible to clinafloxacin and sitafloxacin based on an investigational breakpoint of 1 mg/L and were less influenced by mutations within the grl and gyr gene loci. In one-quarter to one-third of the strains tested, reserpine decreased slightly the MICs of moxifloxacin, clinafloxacin and sitafloxacin. Compared with moxifloxacin, clinafloxacin and sitafloxacin showed a significantly increased anti-staphylococcal potency.

Prevalence of macrolide-resistance genes in Staphylococcus aureus and Enterococcus faecium isolates from 24 European university hospitals

The polymerase chain reaction (PCR) was used to study the prevalence of the macrolide resistance genes ermA, ermB, ermC, msrA/msrB, ereA and ereB, in 851 clinical isolates of Staphylococcus aureus and 75 clinical isolates of Enterococcus faecium that were erythromycin resistant. The isolates were from 24 European university hospitals. In S. aureus, the ermA gene was more common in methicillin-resistant S. aureus (MRSA) isolates (88%) than in methicillin-susceptible S. aureus (MSSA) isolates (38%), and occurred mainly in strains with constitutive MLS(B) expression. In contrast, ermC was more common in MSSA (47%) than in MRSA (5%), occurring mainly in strains with inducible expression. The ereB gene was only found in MRSA isolates expressing a constitutive MLS(B) phenotype (1%). The ereA gene was not detected. Macrolide resistance by efflux due to the msrA/msrB gene was only detected in MSSA isolates (13%). In contrast to S. aureus, erythromycin resistance in E. faecium was almost exclusively due to the presence of the ermB gene (93%).

Antimicrobial resistance in European isolates of Pseudomonas aeruginosa. European SENTRY Participants

Pseudomonas aeruginosa is responsible for a substantial fraction of hospital infections. Twenty-five European university hospitals submitted a total of 1411 Pseudomonas aeruginosa isolates for susceptibility testing during 1997 and 1998. The isolates showed highest susceptibility to amikacin (87.5%), meropenem (87.3%) and piperacillin/tazobactam (86.8%). Susceptibility to ciprofloxacin was 73.2%. There was no clear geographical distribution of resistance, although isolates from northwestern Europe tended to be more susceptible than those from southeastern Europe. Isolates that were resistant to one class of antibiotics were also often resistant to at least one other class of antibiotics. Imipenem-resistant isolates were generally not clonally related.

Distribution of macrolide-resistance genes in Staphylococcus aureus blood-culture isolates from fifteen German university hospitals. M.A.R.S. Study Group. Multicentre Study on Antibiotic Resistance in Staphylococci

The purpose of the study was to analyze the distribution of the macrolide-resistance genes in 134 erythromycin-resistant Staphylococcus aureus blood-culture isolates collected at 15 German university hospitals. The most prevalent resistance gene was ermC (68/134; 50.7%), followed by ermA (52/134; 38.8%), ereB (10/134; 7.5%), and mrsA/msrB (4/134; 6%). The least common genes were ermB (3/134; 2.2%) and ereA (1/134; 0.7%). Overall, resistance to erythromycin was predominantly due to the presence of two erm genes, although with different distributions, depending on the methicillin-resistance pattern.

In vitro activities of sitafloxacin (DU-6859a) and six other fluoroquinolones against 8,796 clinical bacterial isolates

The in vitro activities of sitafloxacin, ciprofloxacin, trovafloxacin, levofloxacin, clinafloxacin, gatifloxacin, and moxifloxacin against 5,046 gram-negative bacteria, 3,344 gram-positive cocci, and 406 anaerobes were determined. Sitafloxacin was the most active agent against gram-positive cocci and anaerobes. Against Enterobacteriaceae and nonfermenters, its activity was either equivalent to or better than that of clinafloxacin.

Antimicrobial susceptibility and frequency of occurrence of clinical blood isolates in Europe from the SENTRY antimicrobial surveillance program, 1997 and 1998

As part of the European arm of the SENTRY Antimicrobial Surveillance Program, 25 European university hospitals referred 9613 blood isolates for in vitro testing against >20 antimicrobial agents. Escherichia coli, Staphylococcus aureus, coagulase-negative Staphylococcus, Pseudomonas aeruginosa, and Klebsiella pneumoniae were the 5 most frequent isolates and accounted for two-thirds of all referrals, with minor regional variation. Of these, approximately 0.36% of E. coli and 16.7% of K. pneumoniae isolates proved to be potential extended-spectrum beta-lactamase producers, and their incidence clearly varied regionally. Quinolone resistance was detected among gram-negative species; in particular, P. aeruginosa and Acinetobacter species. Considerable regional variation was observed in the incidences of methicillin resistance in S. aureus and penicillin resistance in Streptococcus pneumoniae. The incidence of vancomycin resistance in enterococci was relatively low overall and primarily associated with Enterococcus faecium. However, extrapolation of these data to smaller and nonteaching hospitals should be undertaken with caution, since resistance rates may be lower in these facilities.

Antimicrobial resistance among urinary tract infection (UTI) isolates in Europe: results from the SENTRY Antimicrobial Surveillance Program 1997

The SENTRY Antimicrobial Surveillance Program was established to monitor the occurrence and antimicrobial susceptibility of bacterial pathogens via an international network of sentinel hospitals. Twenty European hospitals referred a total of 887 urinary tract infection (UTI) isolates to the European SENTRY reference laboratory during the period October-December 1997. Ninety percent of the referred species were represented by Escherichia coli (52%), Enterococcus spp. (12%), Klebsiella spp. (7%), Proteus spp. (7%), Pseudomonas aeruginosa (7%), and Enterobacter spp. (5%). The susceptibility of E. coli isolates to penicillins was less than 60%, while almost all of the isolates were susceptible to piperacillin/tazobactam (98% susceptibility), cephalosporins (98%), and carbapenems (100%). Amikacin was the best aminoglycoside (99.8% susceptibility). The susceptibility to quinolones was only 88-89%, with highest levels of resistance observed for isolates from Portugal, Italy, England, The Netherlands, and some centers in France, Spain, and Poland. The susceptibility of Klebsiella spp. to the newer generations of cephalosporins was 82-95% and to the carbapenems 100%. Amikacin was again the best aminoglycoside (94% susceptibility). The susceptibility of Enterobacter spp. to any beta-lactam antibiotic was poor, except for the carbapenems (100% susceptibility) and cefepime (90% susceptibility), while the susceptibility to aminoglycosides was 80-89%. Proteus spp. showed complete susceptibility to cefepime, ceftriaxone, the carbapenems, and piperacillin/tazobactam, while the susceptibility of P. aeruginosa isolates was poor, with best results for the carbapenems (susceptibility 89%), piperacillin/tazobactam (susceptibility 84%), and amikacin and ticarcillin (susceptibility to both 80%). Enterococcus spp. showed the highest susceptibility to vancomycin (98%), teicoplanin (98%), and ampicillin (94%).

Epidemiology of quinolone resistance of Klebsiella pneumoniae and Klebsiella oxytoca in Europe

The epidemiology of quinolone resistance and the concomitant resistance to other antibiotic classes was investigated in 445 Klebsiella pneumoniae and 238 Klebsiella oxytoca isolates. Decreased susceptibility to ciprofloxacin was found in 7.2% and 3.4% of these two species, respectively. Ciprofloxacin resistance was significantly linked to ceftazidime resistance, the hallmark of extended-spectrum beta-lactamase production, as well as to resistance to all antibiotic classes tested. Using automated ribotyping, seven intrahospital- and interhospital-transmitted clones of ciprofloxacin-resistant isolates were found. The newer fluoroquinolones sitafloxacin and clinafloxacin may become increasingly valuable, since they proved to be active also against ciprofloxacin-resistant isolates.

Molecular epidemiology of quinolone resistance and comparative in vitro activities of new quinolones against European Staphylococcus aureus isolates

New fluoroquinolones (FQ) may possibly be used as alternative therapeutic options for Staphylococcus aureus infections. Our objectives were: (1) to define the in vitro activities of seven FQs in a collection of 434 methicillin-susceptible and 457 methicillin-resistant S. aureus from 23 European university hospitals; (2) to characterise the prevalence of mutations in the grlA and gyrA genes in all ciprofloxacin-resistant (n=433) isolates of S. aureus; (3) to determine the percentage of ciprofloxacin-resistant S. aureus strains with measurable quinolone efflux.

METHODS

(1) The in vitro activities of different FQs were determined by microdilution tests. (2) PCR-amplified DNA was sequenced. (3) Ciprofloxacin minimum inhibitory concentrations (MIC) were determined in the presence and absence of reserpine, which inhibits efflux pumps.

RESULTS

(1) Irrespective of the methicillin resistance of the isolates, sitafloxacin and clinafloxacin showed the best in vitro activities. (2) All ciprofloxacin-resistant isolates exhibited GrlA alterations, namely Ser-80-->Phe or Tyr or Glu-84-->Lys or Ala-116-->Glu or Pro or a combination of Ser-80-->Phe and Glu-84-->Val. These alterations in GrlA were combined with alterations in GyrA, namely Ser-84-->Leu or Lys or Glu-88-->Lys or Val. (3) Reserpine reduced ciprofloxacin MIC values in ca. 30% of the clinical isolates tested.

CONCLUSIONS

(1) This current European overview of mutations involved in FQ resistance demonstrates that only a limited number of classical mutations in grlA and gyrA contributed to resistance in clinical isolates. (2) An efflux pump is involved in ca. 30% of ciprofloxacin-resistant S. aureus isolates. (3) Sitafloxacin and clinafloxacin are two very promising new FQs with good anti-staphylococcal activity. New FQs, perhaps in combination with efflux pump inhibitors, might play a role in the treatment of S. aureus infections.

Invasive and noninvasive group A streptococcal isolates with different speA alleles in The Netherlands: genetic relatedness and production of pyrogenic exotoxins A and B

Streptococcal pyrogenic exotoxin A (SPE-A) and SPE-B have been implicated in the pathogenesis of severe group A streptococcal (GAS) disease. We studied 31 invasive GAS strains including 18 isolates from patients with toxic shock syndrome and 22 noninvasive strains isolated in The Netherlands between 1994 and 1998. These strains were associated with the different allelic variants of the gene encoding SPE-A. We selected endemic strains with speA-positive M and T serotypes: speA2-associated M1T1 and M22-60T12 strains, speA3-associated M3T3 strains, and speA4-associated M6T6 strains. Since speA1-positive isolates were not frequently encountered, we included speA1 strains of different serotypes. The GAS strains were compared genotypically by pulsed-field gel electrophoresis and phenotypically by the in vitro production of SPE-A and SPE-B. All strains within one M and T type appeared to be of clonal origin. Most strains produced SPE-A and SPE-B, but only a minority of the speA4-positive isolates did so. Among our isolates, speA1- and speA3-positive strains produced significantly more SPE-A than speA2- and speA4-carrying strains, while SPE-B production was most pronounced among speA1- and speA2-containing strains. There was a marked degree of variability in the amounts of exotoxins produced in vitro by strains that shared the same genetic profile. We conclude that the differences in the in vitro production of SPE-A and SPE-B between our selected strains with identical M and T types were not related to either genetic heterogeneity or the clinical course of GAS disease in the patient from whom they were isolated.

Class 1 integrons, gene cassettes, mobility, and epidemiology

Integrons are genetic elements that, although unable to move themselves, contain gene cassettes that can be mobilized to other integrons or to secondary sites in the bacterial genome. The majority of approximately 60 known gene cassettes encode resistance to antibiotics. Recently, a number of gene cassettes encoding extended-spectrum beta-lactamases or carbapenemases have been described. Up to at least five cassettes may be present in an integron, which leads to multiresistance. Frequently, more than one integron is observed within the same bacterial cell. Integrons are widespread in their species distribution. Although integrons are normally reported from Enterobacteriaceae and other gram-negative bacteria, an integron has been described in Corynebacterium glutamicum, a gram-positive species. The gene cassette in this integron showed even higher expression when compared to the expression in Escherichia coli. Integrons have been reported from all continents and are found frequently. The widespread occurrence of integrons is thought to be due to their association with transposon plasmids, conjugative plasmids, or both. Integrons form an important source for the spread of antibiotic resistance, at least in gram-negative bacteria but also potentially in gram-positive bacteria. The aim of this review is to describe the versatility of integrons, especially their mobility and their ability to collect resistance genes.

Association of alterations in ParC and GyrA proteins with resistance of clinical isolates of Enterococcus faecium to nine different fluoroquinolones

The parC and gyrA genes of 73 ciprofloxacin-resistant and 6 ciprofloxacin-susceptible Enterococcus faecium clinical isolates were partly sequenced. Alterations in ParC and GyrA, possibly in combination with other resistance mechanisms, severely restricted the in vitro activities of the nine quinolones tested. For all isolates, clinafloxacin and sitafloxacin showed the best activities.

Nucleic acid sequence-based amplification (NASBA) detection of medically important Candida species

Nucleic Acid Sequence Based Amplification (iNASBA), an isothermal amplification technique for nucleic acids, was evaluated for the identification of medically important Candida species using primers selected from 18S rRNA sequences conserved in fungi. An RNA fragment of 257 nucleotides was amplified for Candida albicans. Nineteen different fungi were tested for rRNA amplification with the NASBA. All were positive when analyzed on agarose gel, whereas human RNA was negative. For the identification of Candida species, NASBA amplification products were analyzed in an enzyme bead-based detection format, using species-specific biotinylated probes and a generic Candida HRPO probe or a membrane-based system using biotinylated probes and avidin-HPRO. Discrimination of the major human pathogenic Candida spp. was based on a panel of biotinylated probes for C. krusei, C. tropicalis, C. albicans, C. glabrata, and C. lusitaniae. Using rRNA dilutions obtained from pure cultures of C. albicans, the combination of NASBA and the enzymatic bead-based detection yielded a sensitivity equivalent to 0.01 CFU. In a model system using 1 ml of artificially contaminated blood as few as 1-10 CFU of C. albicans could be detected. Testing of 68 clinical blood samples from patients suspected of candidemia showed that eight samples were positive for C. albicans and one for C. glabrata. Testing of 13 clinical plasma samples from patients suspected of fungemia identified the presence of C. albicans in two specimens. The whole procedure of sample preparation, amplification and identification by hybridization can be performed in 1 day. This speed and the observed sensitivity of the assay make the NASBA a good alternative to PCR for the detection of candidemia.

International surveillance of blood stream infections due to Candida species in the European SENTRY Program: species distribution and antifungal susceptibility including the investigational triazole and echinocandin agents. SENTRY Participant Group (Europe)

The SENTRY Antimicrobial Surveillance Program, an international study of blood stream infections (BSIs), detected 170 episodes of candidemia in 20 European medical centers (13 nations) between January and December, 1997. Twenty-three percent of the candidal BSI occurred in patients hospitalized in an intensive care unit, 21% in patients in an internal medicine service, 13% in patients in a surgical service, and 9% in patients in an oncology service. Overall, 53% of the BSI were attributable to Candida albicans followed in prevalence by C. parapsilosis (21%), C. glabrata (12%), C. tropicalis (6%), C. famata (2%), C. krusei (1%), and C. inconspicua (1%). As observed previously in Canada and Latin America, C. parapsilosis and not C. glabrata, was the most common non-albicans species causing yeast BSI in Europe. The proportion of these candidemias attributable to C. albicans varied widely from 0-100% among the 20 European centers. Among the different species of Candida, resistance to fluconazole (MIC, > or = 64 micrograms/mL) and itraconazole (MIC, > or = 1.0 microgram/mL) was observed with C. glabrata and C. krusei and was observed more rarely among other species (e.g., C. inconspicua). Isolates of C. albicans, C. parapsilosis, C. tropicalis, and C. guilliermondii were all highly susceptible to both fluconazole and itraconazole. Furthermore, the investigational triazoles (BMS-207147, Sch 56592, and voriconazole) and an echinocandin (MK-0991) all demonstrated potent in vitro activity (MIC90s, 0.5, 0.5, 1.0, and 2.0 micrograms/mL, respectively) against these isolates. Continued surveillance at an international level will be important to monitor trends in species distribution and antifungal susceptibility among invasive strains of Candida.

Antimicrobial resistance among community-acquired pneumonia isolates in Europe: first results from the SENTRY antimicrobial surveillance program 1997. SENTRY Participants Group

OBJECTIVE

The SENTRY antimicrobial surveillance program was established to monitor the occurrence and antimicrobial susceptibility of bacterial pathogens via an international network of sentinel hospitals.

MATERIAL AND METHODS

Microorganisms were forwarded to the reference laboratory for testing against various antimicrobial agents using broth microdilution. Twenty European hospitals referred 286 Streptococcus pneumoniae, 309 Haemophilus influenzae, and 167 Moraxella catarrhalis isolates during the first 10 months of the study, starting in April 1997.

RESULTS

Seven percent of the S. pneumoniae isolates were highly resistant to penicillin, and 21% showed intermediate resistance. The highly resistant pneumococcal isolates came from Coimbra, Barcelona, Athens, and London, whereas the intermediate penicillin-resistant isolates were received from all participating countries. The incidence of intermediate penicillin-resistant pneumococci was lowest in Lausanne, Freiburg and Duesseldorf, London, and Utrecht and highest in southern European countries. Fifty-five percent of the penicillin-resistant S. pneumoniae were also resistant to erythromycin, and 35% to clindamycin. Sparfloxacin, trovafloxacin, levofloxacin, and vancomycin were fully active against pneumococcal isolates. Haemophilus influenzae isolates were generally highly susceptible to most of the antibiotics tested, and 92% of the M. catarrhalis isolates were resistant to penicillin. Susceptibility to cephalosporins, ciprofloxacin, levofloxacin, and rifampicin was 100%.

CONCLUSION

Penicillin may no longer be the first-choice drug for empirical treatment of pneumococcal infections. The newer fluoroquinolones may play a role in the empirical treatment of community-acquired pneumonia.

Comparative activities of six different fluoroquinolones against 9,682 clinical bacterial isolates from 20 European university hospitals participating in the European SENTRY surveillance programme. The SENTRY participants group

The in-vitro activities of gatifloxacin, trovafloxacin, levofloxacin, sparfloxacin, ofloxacin, and ciprofloxacin were tested against 9,682 clinical bacterial isolates from 20 European university hospitals participating in the European SENTRY surveillance programme. Gatifloxacin and trovafloxacin exhibited the highest activities against gram-positive cocci, while levofloxacin, ofloxacin, ciprofloxacin, and gatifloxacin were the most active against Enterobacteriaceae. Ciprofloxacin and levofloxacin showed the highest antimicrobial activities against Pseudomonas spp., while gatifloxacin and trovafloxacin were the most active against Acinetobacter spp. and Stenotrophomonas maltophilia. All Haemophilus spp. and Moraxella catarrhalis isolates were fully susceptible to all quinolones tested. Overall, the new quinolones, showed improved activity against gram-positive cocci and gram-negative non-fermenters while retaining their broad-spectrum activity against gram-negative bacilli.

Comparative in vitro activities of ciprofloxacin, clinafloxacin, gatifloxacin, levofloxacin, moxifloxacin, and trovafloxacin against Klebsiella pneumoniae, Klebsiella oxytoca, Enterobacter cloacae, and Enterobacter aerogenes clinical isolates with alterations in GyrA and ParC proteins

The in vitro activities of ciprofloxacin, clinafloxacin, gatifloxacin, levofloxacin, moxifloxacin, and trovafloxacin were tested against 72 ciprofloxacin-resistant and 28 ciprofloxacin-susceptible isolates of Klebsiella pneumoniae, Klebsiella oxytoca, Enterobacter cloacae, and Enterobacter aerogenes. Irrespective of the alterations in GyrA and ParC proteins, clinafloxacin exhibited greater activity than all other fluoroquinolones tested against K. pneumoniae and E. aerogenes.