Primary and combined resistance to four antimicrobial agents in Helicobacter pylori in Sofia, Bulgaria

The aim of this study was to evaluate the primary and combined resistance of Helicobacter pylori against four antimicrobial agents by a screening agar method (SAM) and a modified disk diffusion method (MDDM) alone and in combination. Pre-treatment H. pylori isolates from 192 consecutive H. pylori-positive patients at three hospitals in Sofia were investigated. MDDM was performed with disks containing metronidazole (5 microg), clarithromycin (15 microg) or erythromycin (15 microg), ciprofloxacin (5 microg) and tetracycline (30 microg). Resistance was determined by an inhibitory zone of <16 mm for metronidazole and < or =30 mm for other agents tested. The cut-off concentrations used to define resistance by SAM were: metronidazole >8 mg/L, clarithromycin >2 mg/L, tetracycline >4 mg/L and ciprofloxacin >1 mg/L. Primary resistance rates in H. pylori were: metronidazole 28.6%, clarithromycin 9.7%, metronidazole + clarithromycin 2.8%, ciprofloxacin 3.9%, metronidazole + ciprofloxacin 2.3%, tetracycline 1.9% and metronidazole + tetracycline 1.2%. Among metronidazole-resistant isolates, combined resistance to clarithromycin, ciprofloxacin and tetracycline was present in 11.4% (5 of 44 strains), 8.3% (3 of 36) and 4.9% (2 of 41), respectively. Two strains exhibited triple resistance to macrolides, metronidazole and either ciprofloxacin or tetracycline. Three tetracycline-resistant strains were detected in 1999; however, resistance rates to other agents were relatively stable during the 6 years. Primary H. pylori resistance to metronidazole is moderate and resistance to clarithromycin and to ciprofloxacin is considerable in comparison with results in most other countries. The alarming appearance of strains harbouring combined resistance or multiresistance provides the motivation for continued surveillance of H. pylori at global, national and regional levels.     

Antibiotic resistance in exopolysaccharide-forming Staphylococcus epidermidis clinical isolates from orthopaedic implant infections

The opportunistic pathogen Staphylococcus epidermidis is able to produce biofilm and to frequently cause implant infections. In recent years, it has also exhibited an increasing antimicrobial drug resistance. Here, the resistance to a panel of 16 different antibiotics in 342 clinical strains of S. epidermidis from orthopaedic implant infections has been investigated. The isolates were pheno- and genotyped for extracellular polysaccharide production, relevant to staphylococcal biofilm formation, in order to ascertain possible associations with antibiotic resistance. Approximately 10% of the isolates were found to be sensitive to all screened antibiotics. In all, 37-38% were resistant to beta-lactams such as oxacillin and imipenem, while the resistance to penicillin, ampicillin, cefazolin, cefamandole, was consistently observed in over 80% of the strains. Erythromycin- and clindamycin- resistant strains were approximately 41% and 16%, respectively. Of the isolates, 10% was resistant to chloramphenicol, 23% to sulfamethoxazole and 26% to ciprofloxacin. Resistance to vancomycin was never observed. Interestingly, exopolysaccharide-producing strains exhibited a significantly higher prevalence in the resistance to the four aminoglycosides (gentamicin, amikacin, netilmicin, tobramycin), to sulfamethoxazole and to ciprofloxacin with respect to non-producing isolates. Moreover, multiple resistance to antibiotics was more frequent among exopolysaccharide-forming strains.     

Antimicrobial susceptibility of Neisseria gonorrhoeae isolated in Bangladesh (1997 to 1999): rapid shift to fluoroquinolone resistance

Periodic monitoring of antimicrobial susceptibility of Neisseria gonorrhoeae is essential for early detection of emergence of drug resistance. A total of 343 gonococcal strains isolated from high-risk and general populations in Bangladesh from 1997 to 1999 were studied. The MICs of penicillin, tetracycline, ciprofloxacin, ceftriaxone, and spectinomycin for the isolates were determined by the agar dilution method. Of the isolates from 1997, 9% were resistant (MIC >or= 1.0 microg/ml) to ciprofloxacin, while 41 and 49% of the isolates from 1998 and 1999, respectively, were resistant to ciprofloxacin. Of the N. gonorrhoeae isolates from 1998 and 1999, 1.2 and 3.6%, respectively, both were penicillinase producing and displayed plasmid-mediated tetracycline resistance.     

Distinct antimicrobial resistance patterns and antimicrobial resistance-harboring genes according to genomic species of Acinetobacter isolates

Using 58 isolates of Acinetobacter species recovered from a university hospital between August 2004 and March 2005, we performed genomic identification by amplified rRNA gene restriction analysis (ARDRA) and investigated the existence of metallo-beta-lactamase (MBL) producers and extended-spectrum beta-lactamase (ESBL) producers. Genomic species identification of Acinetobacter strains using ARDRA showed that 40 strains were genomic species 2 (Acinetobacter baumannii), 9 were 13 sensu Tjernberg and Ursing (13TU), 5 were Acinetobacter phenon 6/ct 13TU, and 4 were Acinetobacter genospecies 3. Among 58 strains, 13 isolates were MBL producers carrying bla(IMP-1) or bla(VIM-2) and 13 isolates were ESBL producers carrying bla(PER-1). Notably, the MBL producers were mostly 13TU, Acinetobacter phenon 6/ct 13TU, and Acinetobacter genospecies 3, which showed susceptibility to ciprofloxacin and ampicillin-sulbactam. However, 12 of 13 strains carrying bla(PER-1) were A. baumannii, showing multidrug resistance. The data revealed that the antimicrobial resistance patterns and resistance-harboring genes of Acinetobacter species are remarkably distinct according to the genomic species of Acinetobacter isolates.     

Antimicrobial resistance of Salmonella serotypes isolated from slaughter-age pigs and environmental samples

The aim of this study was to determine the antimicrobial resistance patterns of Salmonella strains isolated from slaughter-age pigs and environmental samples collected at modern swine raising facilities in Brazil. Seventeen isolates of six serotypes of Salmonella enterica subsp. enterica were isolated out of 1,026 collected samples: Salmonella Typhimurium (1), Salmonella Agona (5), Salmonella Sandiego (5), Salmonella Rissen (1), Salmonella Senftenberg (4), and Salmonella Javiana (1). Resistance patterns were determined to extended-spectrum penicillin (ampicillin), broad-spectrum cephalosporins (cefotaxime and ceftriaxone), aminoglycosides (streptomycin, neomycin, gentamicin, amikacin, and tobramycin), narrow-spectrum quinolone (nalidixic acid), broad-spectrum quinolone (ciprofloxacin and norfloxacin), tetracycline, trimethoprim, and chloramphenicol. Antimicrobial resistance patterns varied among serotypes, but isolates from a single serotype consistently showed the same resistance profile. All isolates were resistant to tetracycline, streptomycin, and nalidixic acid. One isolate, Salmonella Rissen, was also resistant to cefotaxime and tobramycin. All serotypes were susceptible to ceftriaxone, norfloxacin, ciprofloxacin, ampicillin, gentamicin, and chloramphenicol. The high resistance to tetracycline and streptomycin may be linked to their common use as therapeutic drugs on the tested farms. No relation was seen between nalidixic acid and fluoroquinolone resistance.     

Low-level resistance to fluoroquinolones conferred by efflux overproduction in Pseudomonas aeruginosa: clinical significance and routine detection

The aim of this study was (i) to assess the impact of stable overproduction of efflux systems MexAB-OprM and MexXY-OprM on the bacteriostatic activities of fluoroquinolones in clinical Pseudomonas aeruginosa strains and (ii) to find a convenient test for screening isolates with a low level resistance to fluoroquinolones. The minimal inhibitory concentrations (MICs) of ciprofloxacin and levofloxacin were determined for clinical isolates of P. aeruginosa overexpressing MexAB-OprM or MexXY-OprM. Efflux pumps derepression was associated with a modest two- to fourfold increase in resistance to the tested fluoroquinolones. Clinical significance of low level resistance conferred by the efflux mechanism was evaluated with a Monte Carlo simulation with various fluoroquinolone regimens. With this model, low levels of resistance to ciprofloxacin (MIC > or =0.25 mg/L) or levofloxacin (MIC > or =1 mg/L) such as those due to overproduced MexAB-OprM or MexXY-OprM were predicted to result in poor clinical outcomes. Altogether these data strongly suggest that when derepressed MexAB-OprM or MexXY-OprM provides P. aeruginosa with a resistance that may be sufficient to impair the efficacy of single therapy with highly potent fluoroquinolones such as ciprofloxacin and levofloxacin. Routine detection of clinical strains that displayed low-level resistance to fluoroquinolones with a Mueller Hinton agar containing 0.20 mg/L of ciprofloxacin will help clinician in his therapeutical choice.     

High level ciprofloxacin resistance in Salmonella enterica isolated from blood

PURPOSE: Over the last few years, resistance to ciprofloxacin in Salmonella enterica has become a global concern. The present study was undertaken to find out the susceptibility pattern of Salmonella enterica isolates in our hospital. METHODS: Blood cultures were done using BacT/ALERT 3D system. The antimicrobial susceptibility testing was carried out by the Kirby-Bauer disc diffusion method using CLSI breakpoints. Minimum inhibitory concentration was determined for ciprofloxacin-resistant strains using E-test and Vitek-1 automated system. RESULTS: A total of 25,953 samples of blood culture yielded 431 Salmonella enterica serotype Typhi and 198 serotype Paratyphi A isolates. Twenty-two isolates of serotype Typhi were resistant to ciprofloxacin, while two isolates of Typhi and two Paratyphi A were intermediately susceptible to ciprofloxacin. Ciprofloxacin resistance is 5.6% (24 isolates) among Salmonella enterica serotype Typhi. Ampicillin, chloramphenicol and co-trimoxazole resistance in Salmonella enterica serotype Typhi appears to have decreased to 14.9% (64/431) in comparison to the 27% (55/205) during 2003. All isolates were sensitive to ceftriaxone. CONCLUSIONS: Ciprofloxacin can no longer be considered as the drug of choice in treating Salmonella infections. While first-line antimicrobials may still have a role to play in the treatment of enteric fever, ceftriaxone remains the sole defence against ciprofloxacin-resistant Salmonella infections.     

High rates of plasmid-mediated quinolone resistance QnrB variants among ciprofloxacin-resistant Escherichia coli and Klebsiella pneumoniae from urinary tract infections in Korea

The aims of this study were to investigate the prevalence of qnrA, qnrB, and qnrS determinants and their molecular characteristics in ciprofloxacin-resistant isolates of Escherichia coli and Klebsiella pneumoniae from urinary tract infections (UTI) in Korea. A total of 202 nonduplicated clinical isolates of ciprofloxacin-resistant E. coli (n = 143) and K. pneumoniae (n = 59) were collected between July 2005 and August 2006. The qnr determinant screening was carried out by PCR amplification of qnrA, qnrB, and qnrS, and all positive results were confirmed by direct sequencing of the PCR products. For qnr-positive strains and their conjugants, antimicrobial susceptibility tests and pulsed-field gel electrophoresis (PFGE) were performed. The qnrB gene was detected in 41 of the 202 isolates. Among 33 of 59 (55.9%) K. pneumoniae isolates showing qnrB, 29 isolates contained the qnrB4 gene, 3 isolates had the qnrB2 gene, and 1 isolate had the qnrB6 gene. All 8 (5.6%) of the qnrB-positive isolates among the 143 E. coli strains possessed the qnrB4 gene. The minimum inhibitory concentrations (MICs) of ciprofloxacin for the transconjugants were 0.03-2 mug/ml, representing an increase of 4- to 256-fold relative to the recipient, E. coli J53Az(r). Resistances to various other antimicrobial agents also were transferred with the plasmid. The PFGE analysis revealed indistinguishable or closely related patterns in several strains and highly diverse patterns in general. QnrB variants, especially the qnrB4 subtype, are highly prevalent in ciprofloxacin-resistant E. coli and K. pneumoniae from UTI in Korea. The emergence of plasmid-mediated quinolone resistance may contribute by several means to the rapid increase in bacterial resistance to these drugs.     

Antimicrobial susceptibility of Shigella isolates in eight Asian countries, 2001-2004.

BACKGROUND AND PURPOSE: Shigellosis is a major health problem in developing countries, causing 91 million episodes and 414,000 deaths in Asia annually. Because of increasing trends towards drug resistance, this study was undertaken to monitor local resistance patterns of Shigella isolates from 8 Asian countries. METHODS: Ninety eight Shigella isolates collected from 8 centers in 8 Asian countries from July 2001 to July 2004 were analyzed in terms of serogroup distribution and antimicrobial susceptibility. RESULTS: The most common serogroup of Shigella isolates was Shigella flexneri (49/98, 50%), followed by Shigella sonnei (44/98, 45%). The highest resistance rate was found for trimethoprim-sulfamethoxazole (81%), followed by tetracycline (74%) and ampicillin (53%). Overall, 76 Shigella isolates (78%) were multidrug-resistant strains; S. flexneri had a higher multidrug resistance rate than S. sonnei (74% vs 23%). Increasing ciprofloxacin and ceftriaxone resistance was observed; approximately 10% and 5% of isolates were resistant to ciprofloxacin and ceftriaxone, respectively. Five ceftriaxone-non-susceptible strains (from Taiwan [3], Hong Kong [1] and The Philippines [1]) and 10 ciprofloxacin-non-susceptible strains (from Hong Kong [2], The Philippines [1], Korea [2], Vietnam [4] and Sri Lanka [1]) were isolated. CONCLUSIONS: High rates of multidrug resistance and steady increases in ceftriaxone and ciprofloxacin resistance of Shigella are serious pubic health concerns in Asian countries. Continuous monitoring of resistance patterns among Shigella isolates is necessary.     

Clonality among ampicillin-resistant Enterococcus faecium isolates in Sweden and relationship with ciprofloxacin resistance

Objective  To investigate clonal relationships in a nationwide sample of human Enterococcus faecium isolates.
Methods  Biochemical fingerprinting (PhP (PhenePlate) typing) was used to compare 180 fecal ampicillin-resistant E. faecium (ARE) isolates with 169 matched fecal ampicillin-susceptible E. faecium (ASE) isolates from patients in 23 hospitals, collected in 1998, and to study 39 fecal ARE isolates from non-hospitalized individuals collected in 1998, and five ARE and 29 ASE isolates from the early 1990s. Representative ARE and ASE isolates were subjected to pulsed-field gel electrophoresis (PFGE) analysis of genomic DNA and sequencing of the regions encoding the fluoroquinolone targets of the enzymes GyrA and ParC.
Results  Both PhP and PFGE results showed a higher homogeneity among ARE than among ASE isolates ( P  < 0.001). One PhP type (FMSE1) comprised 73% of the hospital ARE isolates (53% of ARE isolates from non-hospitalized individuals, and four of five ARE isolates from the early 1990s), but only 1% of the ASE isolates. PFGE of the hospital E. faecium isolates revealed that 23 of the 25 ARE isolates and one of the 22 ASE isolates were of one dominating type. High-level resistance to ciprofloxacin (MIC > 16 mg/L) was present in 91% of ARE isolates, whereas only low-level resistance (MIC 4–16 mg/L; 35% of isolates) was found among ASE isolates. One mutation in parC (codon 80) and one of two mutations in gyrA (codons 83 or 87) were detected in all ARE isolates tested with high-level ciprofloxacin resistance, but were lacking in ARE and ASE isolates with low-level ciprofloxacin resistance.
Conclusion  Most ARE isolates in Sweden were clonally related. High-level ciprofloxacin resistance was found in ARE isolates of PhP type FMSE1 as well as in other PhP types, but never in ASE isolates.     

Fluoroquinolone and macrolide resistance in Campylobacter jejuni isolated from broiler slaughterhouses in southern Brazil

Campylobacter jejuni is recognized as a leading cause of acute bacterial gastroenteritis in humans. The over-use of antimicrobials in the human population and in animal husbandry has led to an increase in antimicrobial-resistant infections, particularly with fluoroquinolones and macrolides. The aim of the present study was to provide information of the current status of antimicrobial resistance patterns in Campylobacter jejuni from poultry sources. Fifty strains were recovered from broiler slaughterhouses in Rio Grande do Sul state, Brazil, 2012. The strains were investigated for antimicrobial susceptibility against three agents (ciprofloxacin, nalidixic acid and erythromycin) by minimal inhibitory concentrations. The strains were analysed by polymerase chain reaction-restriction fragment length polymorphism for detection of the Thr-86 mutation that confers resistance to ciprofloxacin. In addition, all the strains were tested for the presence of efflux systems (cmeB gene) conferring antimicrobial resistance. The minimum inhibitory concentrations results showed that 98% of isolates were sensitive to erythromycin and most isolates were resistant to ciprofloxacin (94%) and nalidixic acid (90%). A complete correlation was observed between the minimum inhibitory concentrations and PCR-RFLP assay. Finally, the cmeB gene that is responsible for multidrug resistance was detected in 16 isolates out the 50 strains (32%).     

Discordance between genotypic and phenotypic drug resistance profiles in human immunodeficiency virus type 1 strains isolated from peripheral blood mononuclear cells

The aim of the study was to analyze the relationship between genotypic and phenotypic drug resistance profiles of human immunodeficiency virus type 1 (HIV-1) strains isolated from patients during double-analogue nucleoside therapy. A drug-resistant HIV strain was isolated from 20 out of 25 patients, with 16 (64%) subjects carrying a virus with multiple drug resistance mutations. The most frequent resistance mutations were M184V (18 isolates) and M41L (7 isolates). Discordance between the genotypic and phenotypic profile for at least one drug was detected in 16 out of 25 strains. Particularly, eight isolates had a discordant genotypic-phenotypic resistance pattern for two drugs and one isolate had such a pattern for three drugs. A genotypic resistance pattern with a phenotypic sensitivity profile was detected in six isolates (four resistant to zidovudine and two resistant to lamivudine). On the other hand for several strains a genotypic pattern of sensitivity pattern to abacavir (10 strains), didanosine (7 strains), stavudine (3 strains), zidovudine (2 strains), and lamivudine (1 strain) with a phenotypic resistance profile was detected. After a follow-up period of 8 months, an impairment of virological and immunological parameters was detected only in subjects with an HIV-1 isolate with a phenotypic resistance profile in despite of the genotypic results. Predicting resistance phenotype from genotypic data has important limitations. Despite the low number of patients and the short follow-up period, this study suggests that during failing therapy with analogue nucleosides, a phenotypic analysis could be performed in spite of an HIV genotypic sensitivity pattern.     

Epidemiology of Klebsiella antibiotic resistance and serotypes.

Because of the emergence of drug-resistant Klebsiella strains in many hospitals, the distribution of the serotypes was reexamined to determine whether there was any correlation between the serotype and the site of isolation from the body, the antimicrobial susceptibility pattern, or the place of acquisition of the organism (hospital or community). One hundred consecutive isolates of Klebsiella pneumoniae from different patients were typed as 1, 2, 3, 4, 5, 6, or greater than 6. Of these, 8 of 28 strains isolated from respiratory secretions were serotype 2 (9 typable strains), 6 of 24 wound isolates were serotype 3 (8 typable strains), and the urine isolates varied in their serotypes. Regardless of serotype, most strains appeared mucoid on blood and MacConkey agars. Twenty-six percent of the isolates were resistant to at least one antimicrobial agent. No correlation was found between the serotypes and the antibiotic resistance; however, strains isolated within 25 days of admission to the hospital from the community were all susceptible. It appears that although there may be a correlation between the serotype and isolation from some sites of the body, knowledge of the serotype of the organism cannot predict the antimicrobial susceptibility pattern. The clinician's choice of antibiotic therapy should depend largely on whether the Klebsiella strain was acquired by the patient in the community (0% resistant) or in the hospital (31% resistant).     

Comparison of gyrA mutations, cyclohexane resistance, and the presence of class I integrons in Salmonella enterica from farm animals in England and Wales

This study is focused on real-time detection of gyrA mutations and of the presence of class I integrons in a panel of 100 veterinary isolates of Salmonella enterica from farm animals. The isolates were selected on the basis of resistance to nalidixic acid, representing a variety of the most prevalent serotypes in England and Wales. In addition, organic solvent (cyclohexane) resistance in these isolates was investigated in an attempt to elucidate the presence of efflux pump mechanisms. The most prevalent mutation among the isolates studied was Asp87-Asn (n = 42), followed by Ser83-Phe (n = 38), Ser83-Tyr (n = 12), Asp87-Tyr (n = 4), and Asp87-Gly (n = 3). Two distinct subpopulations were identified, separated at the 1-mg/liter breakpoint for ciprofloxacin: 86% of isolates with mutations in codon 83 showed MICs of >or=1 mg/liter, while 89.8% of isolates with mutations in codon 87 presented MICs of or=2.0 mg/liter. Thirty-four isolates contained class I integrons, with 71% of the S. enterica serovar Typhimurium isolates and 6.9% of isolates belonging to other serotypes containing such elements. The methods used represent sensitive ways of investigating the presence of gyrA mutations and of detecting class-I integrons in Salmonella isolates. The results can be obtained in less than 1 h from single colonies without the need for purifying DNA.     

Mechanisms of antibiotic resistance in Escherichia coli isolates obtained from healthy children in Spain

Antibiotic resistance and mechanisms involved were studied in Escherichia coli isolates from fecal samples of healthy children. Fifty fecal samples were analyzed, and one colony per sample was recovered and identified by biochemical and molecular tests. Forty-one E. coli isolates were obtained (82%). MIC testing was performed by agar dilution with 18 antibiotics, and the mechanisms of resistance were analyzed. Ampicillin resistance was detected in 24 isolates (58.5%), and blaTEM, blaSHV, and blaOXA type genes were studied by PCR and sequencing. The following beta-lactamases were detected (number of isolates): TEM (20), SHV-1 (1), and OXA-30 (1). The number of aminoglycoside-resistant isolates detected was as follows: streptomycin (15), tobramycin (1), gentamicin (1), and kanamycin (4). The aac(3)-IV gene was detected in the only gentamicin-resistant isolate. Nine (22%) and 2 (5%) isolates showed nalidixic acid (NALR) and ciprofloxacin resistance (CIPR), respectively. Mutations in GyrA and ParC proteins were shown in both NAL(R)-CIP(R) isolates and were the following: (1) GyrA (S83L + D87N), ParC (S801); and (2) GyrA (S83L + A84P), ParC (S80I + A108V). A single mutation in the S83 codon of the gyrA gene was found in the remaining seven NAL(R)-CIP(S) isolates. Tetracycline resistance was identified in 21 isolates (51%) and the following resistance genes were found (number of isolates): tetA (12), tetB (5), and tetD (1). Chloramphenicol resistance was detected in five isolates (12%). These results show that the intestinal tract of healthy children constitutes a reservoir of resistant bacteria and resistance genes.     

Clinical and community strains of Klebsiella pneumoniae: multiple and increasing rates of antibiotic resistance in Abha, Saudi Arabia

Klebsiella pneumoniae is the most commonly isolated bacterial species in a maternity hospital in Saudi Arabia. Here, 380 strains isolated in 1997 and 480 strains in 1999 were studied for their resistance antibiograms, using the standardised disc diffusion test. Of 16 antibiotics tested, four in 1997 and six in 1999 were ineffective against > 50% of the respective isolates, and resistance rates to 11 antibiotics increased over the two-year period (P = 0.05-< 0.0001). With resistance rates of < 20%, imipenem, ciprofloxacin, gentamicin and cefotaxime were more effective in 1997; only imipenem and ciprofloxacin remained as effective in 1999. In addition, 105 community strains were tested and > 50% were resistant to four antibiotics. Resistance rates to most antibiotics were lower than those of clinical strains (P = 0.0285-< 0.0001). Imipenem resistance was detected among both clinical and community isolates. Multiresistance was 64.5% in 1997 and 79.2% in 1999 (P < 0.0001), and 83.8% in community strains in 1999. Using the double-disc synergy test, extended-spectrum beta-lactamase (ESBL) was detected in 27.5% of ceftazidime-resistant clinical strains isolated in 1999. Among the clinical strains, seven (65%) and 11 (67.9%) resistance antibiograms occurred frequently in 1997 and 1999, respectively. Such frequency was not observed among community isolates. These findings confirm the alarmingly high rates of multiresistance and the emergence of ESBL-producing strains, highlighting the urgent need to restrict over-the-counter availability of antibiotics, and increase awareness in the local medical community.     

Increasing ciprofloxacin resistance among prevalent urinary tract bacterial isolates in Gaza Strip, Palestine

This article presents the incidence of ciprofloxacin resistance among 480 clinical isolates obtained from patients with urinary tract infection (UTI) during January to June 2004 in Gaza Strip, Palestine. The resistance rates observed were 15.0% to ciprofloxacin, 82.5% to amoxycillin, 64.4% to cotrimoxazole, 63.1% to doxycycline, 32.5% to cephalexin, 31.9% to nalidixic acid, and 10.0% to amikacin. High resistance to ciprofloxacin was detected among Acinetobacter haemolyticus (28.6%), Staphylococcus saprophyticus (25.0%),Pseudomonas aeruginosa (20.0%), Klebsiella pneumonia (17.6%), and Escherichia coli (12.0%). Minimal inhibitory concentration (MIC) of ciprofloxacin evenly ranged from 4 to 32 mu g/mL with a mean of 25.0 mu g/mL. This study indicates emerging ciprofloxacin resistance among urinary tract infection isolates. Increasing resistance against ciprofloxacin demands coordinated monitoring of its activity and rational use of the antibiotics.     

Susceptibility patterns of enteroaggregative Escherichia coli associated with traveller's diarrhoea: emergence of quinolone resistance.

Enteroaggregative Escherichia coli (EAggEC) isolates were identified as a cause of traveller's diarrhoea in 50 (9%) of 517 patients and their antimicrobial susceptibility was determined. Molecular epidemiological characterisation and investigation of the mechanisms of acquisition of quinolone resistance among nalidixic acid-resistant EAggEC strains was performed. Seventeen (34%) of 50 patients needed antimicrobial therapy, because of persistence of symptoms in nine cases and the severity of symptoms in eight cases. Ampicillin and tetracycline resistance was high, whereas chloramphenicol and co-trimoxazole showed moderate activity and amoxicillin plus clavulanic acid, nalidixic acid and ciprofloxacin showed very good activity. Resistance to nalidixic acid was demonstrated in three isolates, two from patients who had travelled to India. In all three strains the resistance was linked to mutations in the gyrA gene alone or in both gyrA and parC genes. Although ciprofloxacin shows excellent in-vitro activity and could be useful in the treatment of traveller's diarrhoea in patients travelling abroad, it may not be useful in patients who have journeyed to India or to Mexico.     

Molecular epidemiology and distribution of serotypes, surface proteins, and antibiotic resistance among group B streptococci in Italy

Group B streptococci (GBS) comprising three different sets of isolates (31 invasive, 36 noninvasive, and 24 colonizing isolates) were collected in Italy during the years 2002 to 2005. Clonal groups were established by pulsed-field gel electrophoresis (PFGE), and selected isolates were studied by multilocus sequence typing (MLST). GBS isolates were also characterized by classical and molecular techniques for serotyping and protein gene and antibiotic resistance profiling. Some serotypes were significantly associated with a particular isolate population: serotype Ia more frequently corresponded to invasive strains than other strains, serotype V was more frequently encountered among noninvasive strains, and nontypeable strains were more common among isolates from carriers. Four major clonal groups accounted for 52.7% of all isolates: PFGE type 1/clonal complex 1 (CC1) comprised mainly serotype V isolates carrying the alp3 gene, PFGE type 2/CC23 encompassed serotype Ia isolates with the alp1 or alpha gene, PFGE type 3/CC17 comprised serotype III isolates carrying the rib gene, and PFGE type 4/CC19 consisted mainly of serotype II isolates possessing the rib gene. The same serotypes were shared by isolates of different clonal groups, and conversely, isolates belonging to the same clonal groups were found to be of different serotypes, presumably due to capsular switching by the horizontal transfer of capsular genes. Erythromycin resistance (prevalence, 16.5%; 15 resistant isolates of 91) was restricted to strains isolated from patients with noninvasive infections and carriers, while tetracycline resistance was evenly distributed (prevalence, 68.1%; 62 resistant isolates of 91). Most erythromycin-resistant GBS strains were of serotype V, were erm(B) positive, and belonged to the PFGE type 1/CC1 group, suggesting that macrolide resistance may have arisen both by clonal dissemination and by the horizontal transfer of resistance genes.