Low-Frequency Transduction of Imipenem Resistance and High-Frequency Transduction of Ceftazidime and Aztreonam Resistance by the Bacteriophage AP-151 Isolated from a Pseudomonas aeruginosa Strain

Abstract

Bacteriophage AP-151, isolated from a multidrug resistant Pseudomonas aeruginosa strain, was found to transduce antibiotic resistance determinants to recipient strains of P. aeruginosa. Resistance to cefotaxime, ceftazidime, aztreonam, imipenem and meropenem was transduced as a block, at different frequencies, to two P. aeruginosa strains. Resistance was two logarithms higher (in the range 10^?5) for cefotaxime, ceftazidime or aztreonam than for imipenem in recipient strain PAO-1670. The frequency of transduced imipenem resistance was also lower in recipient strain ML-1008. This phenomenon reflects the difference in the lytic activity of AP-151 in both strains, as the titer of the AP-151 phage in the PAO strain was found to be restricted to 10^?4?10^?5 in contrast to the titer of the same phage in the ML strain which was 10^?10. The limited lytic activity in the PAO recipient strain was correlated with higher transducing activity. It can be concluded that some wild-type bacteriophages of P. aeruginosa might have highly individual relations between lytic and transducing activity in various potential recipient nosocomial strains of P. aeruginosa. The nature of resistance to ceftazidime and imipenem was studied using clavu-lanate and EDTA as inhibitors of individual class of beta-lactamases, indicating the presence of extended-spectrum beta-lactamase and a metallo-beta-lacta-mase in this isolate.     

Imipenem and cefotaxime resistance: transduction by wild-type phages in hospital strains of Pseudomonas aeruginosa.

A wild-type bacteriophage appeared and was isolated from a Pseudomonas aeruginosa strain resistant to imipenem, cefotaxime, kanamycin and streptomycin (susceptible to carbenicillin, aztreonam, amikacin and fluoroquinolones). The best transducing properties were obtained with phage lysates prepared from bacteria growing on cefotaxime or imipenem. Transducing properties were found specific for individual recipient strain(s) susceptible to all drugs. A high-frequency of transduction was recorded for kanamycin and particularly for cefotaxime resistance determinants, followed by an imipenem determinant. This is now the fourth published wild-type bacteriophage, isolated from lysogenic nosocomial P. aeruginosa resistant to imipenem which was found to transduce this resistance determinant to susceptible pseudomonads.     

Imipenem and Cefotaxime Resistance: Transduction by Wild-Type Phages in Hospital Strains of Pseudomonas aeruginosa

Summary

A wild-type bacteriophage appeared and was isolated from a Pseudomonas aeruginosa strain resistant to imipenem, cefotaxime, kanamycin and streptomycin (susceptible to carbenicillin, aztreonam, amikacin and fluoroquinolones). The best transducing properties were obtained with phage lysates prepared from bacteria growing on cefotaxime or imipenem. Transducing properties were found specific for individual recipient strain(s) susceptible to all drugs. A high-frequency of transduction was recorded for kanamycin and particularly for cefotaxime resistance determinants, followed by an imipenem determinant. This is now the fourth published wild-type bacteriophage, isolated from lysogenic nosocomial P. aeruginosa resistant to imipenem which was found to transduce this resistance determinant to susceptible pseudomonads.     

Transferable Resistance to Specific Antibiotics in Nosocomial Strains of Pseudomonas aeruginosa from Two Teaching Hospitals

Abstract

We describe the transfer of resistance to kanamycin, carbenicillin and cephaloridine to a recipient strain of Escherichia coli K-12 No. 3110 from three strains of Pseudomonas aeruginosa out of 146 strains tested in 1995. The P.aeruginosa No. 201, 203, 208 donor strains were isolated from patients in the University Clinics in Frankfurt, Germany. They were resistant to most β-lac-tam antibiotics including cephalosporins of the 1st, 2nd and 3rd generation, imipenem, meropenem and aztreon-am. They transferred kanamycin, carbenicillin and cephaloridine resistance determinants to recipient strain E.coli K-12 3110. These determinants were accompanied in strain P.aeruginosa No. 203, with a transfer of cef-tazidime resistance determinants and in P.aeruginosa No. 208 with transfer of cefotaxime, ceftazidime and aztreon-am resistance determinants. Transfer of antibiotic resistance was also studied in 13 nosocomial strains of P.aeruginosa collected for their ceftazidime and/or imipenem resistance in a large Teaching Hospital in Ostrava, Czech Republic. Six of these strains transferred carbenicillin and/or cephaloridine resistance to the E.coli K-12 3110 recipient strain. Resistance to kanamycin and cefotaxime was also co-transferred with carbenicillin and cephaloridine determinants. Ceftazidime, imipenem or ofloxacin resistance was not transferred and is thus, most probably, of chromosomal origin.     

Relationship of antibiotic resistance phenotype to the R-pyocin susceptibility pattern in clinical isolates of Pseudomonas aeruginosa

One hundred sixteen clinical isolates of Pseudomonas aeruginosa were collected from 7 hospitals in Athens. All strains were studied for their susceptibility to cefotaxime, ceftazidime, carbenicillin, aztreonam, imipenem, nalidixic acid, ciprofloxacin, gentamicin, and chloramphenicol. In addition, the R-pyocin susceptibility pattern was determined and the strains were O-serotyped and tested for their agglutination in acriflavine. The isolates included 53 strains resistant to both gentamicin and carbenicillin, 13 to carbenicillin only, 20 to gentamicin only, and 30 sensitive to gentamicin and carbenicillin. The multiresistant isolates displayed relatively higher resistance to all other antibiotics except aztreonam and cefotaxime. Remarkably 30 out of 53 multiresistant isolates reacted with one pyocin only, namely pyocin R2. This R-pyocin response was not encountered in any other strains of the other antibiotic resistance phenotypes. These isolates belonged to the 0-12 serogroup. The 0-12 serogroup was represented only in a minority of strains giving other R-pyocin reactions. It is interesting that strains reacting with pyocin R5 only were mostly susceptible to antibiotics. The results clearly indicate lipopolysaccharide-core mutations in multiresistant clinical isolates of P. aeruginosa. Despite the fact that the R-pyocin resistance pattern can not define the precise possible defect, the multiple and high level resistance associated with R2-pyocin reaction seems to be an interesting trait.     

In-vitro activity of meropenem, a new carbapenem, against imipenem-resistant Pseudomonas aeruginosa and Xanthomonas maltophilia

The activity of meropenem, a new carbapenem, as well as imipenem, ceftazidime, aztreonam, tobramycin, amikacin and ciprofloxacin against 18 strains of Xanthomonas maltophilia and 23 strains of Pseudomonas aeruginosa resistant to imipenem was tested. All strains of X. maltophilia were resistant to both penems. Ceftazidime, tobramycin and ciprofloxacin were the most active antimicrobial agents against this specie. 17% of imipenem-resistant strains of P. aeruginosa were sensitive to meropenem. Ciprofloxacin, amikacin and aztreonam were the most effective agents against these strains.     

Antibiotic use and development of resistance in blood culture isolates: 8 years of experience from a cancer referral center

The consumption of antimicrobial agents in a Slovakian national cancer institute from 1989-1996 was compared with resistance rates in clinically significant blood culture isolates. We observed an increase in resistance of viridans streptococci to penicillin and of enterococci to ampicillin. Resistance to vancomycin and teicoplanin was stable over the entire period despite a 20-fold increase in vancomycin consumption. Nor did we observe increased resistance to ofloxacin despite a 10-fold increase in consumption. Consumption of aminoglycosides and resistance levels were both stable. A different situation was observed with third-generation cephalosporins, where resistance of Pseudomonas aeruginosa, Stenotrophomonas maltophilia and Acinetobacter spp. to ceftazidime and cefotaxime increased with increasing consumption. Resistance of Enterobacteriaceae to cefotaxime and ceftazidime was stable. Resistance to imipenem did not change significantly. However, the number of Stenotrophomonas maltophilia bacteremias increased significantly after imipenem was introduced in 1991. Because of improved outcome in bacteremia, an increased incidence of both gram-negative and gram-positive bacteremia led to only a slight increase in associated mortality.     

Transferable Resistance to Imipenem in Hospital Isolates of Pseudomonas aeruginosa

Summary

We monitored systematically, for more than five years, the eventual transferability of resistance to imipenem in strains of Pseudomonas aeruginosa isolated from patients in Frankfurt University Clinics. Quite recently, four strains have been found which transfer resistance to imipenem to recipient strains of P. aeruginosa. Although in three strains imipenem was the only antibiotic where resistance was transferred directly, the indirect selection analysis showed that, in each instance, determinants of resistance to carbenicillin and kanamycin were co-transferred. The situation in the fourth strain was more complicated. It was resistant to at least ten anti-pseudomonad antibiotics, and transferred directly not only determinants of resistance to imipenem, but also to carbenicillin and kanamycin, as did the other strains, plus determinants of resistance to ceftazidime and cefotaxime. The origin and mode of spread of resistance determinants in studied strains is briefly discussed.     

Epidemiology of antibiotic resistance in human isolates of Enterobacteriaceae in Sicily

The authors have studied the antimicrobial susceptibility of 1073 clinical isolates of various genera of Enterobacteriaceae (collected during the period July-December 1988) to ampicillin, piperacillin, cefotaxime, ceftazidime, ceftriaxone, aztreonam, imipenem, gentamicin, amikacin, netilmicin, norfloxacin, and ciprofloxacin. Antimicrobial susceptibility was determined by Bauer-Kirby disk diffusion method. Of 1073 tested bacteria, 704 (65.6%) produced beta-lactamase detectable by nitrocefin test. The highest percentage of resistant strains occurred with ampicillin (70%) followed by piperacillin (24%) and cefotaxime (19%). Lower percentages of resistant strains were found for gentamicin (10%), aztreonam (8%), netilmicin (7%), norfloxacin (5%) and amikacin (4%). Two percent of the strains were resistant to ciprofloxacin and 0.5% to imipenem. The incidence of resistance in Klebsiella sp., Enterobacter sp., E. coli and Proteus sp. was compared to that found among 872 strains isolated during July-Dec. 1984. In all the Enterobacteriaceae, mainly Enterobacter sp., the increase in the resistance was high for ampicillin, piperacillin and cefotaxime and lower for gentamicin.     

In-vitro activity of ciprofloxacin and other beta-lactam antibiotics against gentamicin- and carbenicillin-resistant isolates of Pseudomonas aeruginosa

The susceptibilities of gentamicin- and carbenicillin-resistant clinical isolates of Pseudomonas aeruginosa to newer beta-lactams, netilmicin and ciprofloxacin were studied by a broth microdilution technique. Imipenem, aztreonam and ceftazidime were active against most of the P. aeruginosa strains with minimum inhibitory concentration (MIC) for 90% of the isolates at clinically achievable levels. Piperacillin, azlocillin, cefotaxime, ceftriaxone, cefsulodin, cefoperazone and netilmicin showed poor activity against these organisms, ciprofloxacin exhibited poor activity, inhibiting only 30% of these strains.     

Sudden increase in Pseudomonas aeruginosa nosocomial strains with broad host range transfer of antibiotic resistance.

We investigated transfer of antibiotic resistance from 51 multiply resistant strains of Pseudomonas aeruginosa isolated from seriously ill patients in the Frankfurt University Clinics. Nine isolates directly transferred resistance to three recipient strains used. Ticarcillin and cephalothin resistance determinants were accepted from eight isolates, and in one case a kanamycin resistance determinant was transferred. The total spectrum of resistance transferred demonstrated that several donor strains transferred a different set of resistance determinants to all three recipient strains. Two P. aeruginosa isolates transferred spectrum of seven resistance determinants including ceftazidime, cefepime and aztreonam, three isolates transferred five determinants and four isolates transferred four resistance determinants. The fact that identical spectra of multiple drug resistance were transferred to recipient strains belonging to three different species (Escherichia coli, Proteus mirabilis and P. aeruginosa), indicates a broad host range in all three transferable genetic elements not observed in previous transfers from P. aeruginosa strains.     

Further Studies of Transferable Antibiotic Resistance in Strains of Pseudomonas aeruginosa from Four Clinical Settings in Three Countries

Abstract

This paper describes transferability of antibiotic resistance determinants in clinical isolates of Pseudomonas aeruginosa resistant to imipenem, cefotaxime and ceftazidime obtained from different clinical settings in three different countries. Two strains of Enterobacteriaceae (Escherichia coli K-12 and Proteus mirabilis P-38) and two strains of P. aeruginosa (PAO and ML) were used as recipient strains. The conjugative transfer of resistance was very specific, i.e. donor strains of P. aeruginosa transferred individual resistance determinants either to recipient strains E. coli K-12 and P. mirabilis P-38, or to P. aeruginosa PAO or ML. In a case when three different species (P. aeruginosa, Acinetobacter calcoaceticus, Stenotrophomonas maltophilia) were isolated from a single patient, a block of resistance determinants was transferred both to Enterobacteriaceae and P. aeruginosa recipients. A single plasmid with rather specific properties was suspected of being exchanged among strains of these different species. It was recommended to study the overall situation of transferability of individual resistance determinants in bacterial strains belonging to various species of nosocomial bacteria, especially of P. aeruginosa, by using a rather specific methodology.     

Phage F-116 Transduction of Antibiotic Resistance from a Clinical Isolate of Pseudomonas aeruginosa

Summary

The lysate of phage F-116, propagated in a multiple drug resistant clinical isolate of Pseudomonas aeruginosa No. 131 was used to transduce determinants of antibiotic resistance to susceptible auxotrophic laboratory strains of the same species. The phage preparation, designated F-116/131 was found to transduce four determinants of resistance, i.e. to imipenem, cefotaxime, kanamycin and carbenicillin, but not to streptomycin, gentamicin, ceftazidime nor ciprofloxacin/ofloxacin. No conjugal transfer of any resistance determinants could be demonstrated in mating experiments using strain No. 131 and two rifampicin-resistant strains of P. aeruginosa which were highly susceptible to all antibiotics studied. These results might suggest that transduction could be an additional way to conjugational transfer of antibiotic resistance among P. aeruginosa.     

In vitro activity of beta-lactam antimicrobial agents in combination with aztreonam tested against metallo-beta-lactamase-producing Pseudomonas aeruginosa and Acinetobacter baumannii

We evaluate the antimicrobial interactions between aztreonam and selected beta-lactams when tested against metallo-beta-lactamase (MbetaL)-producing clinical strains. Ten Pseudomonsa aeruginosa strains, including nine MbetaL-producers (IMP-1, -2, -13, -16, VIM-1, -2, -7, SPM-1 and GIM-1) and five Acinetobacter baumannii strains, including three MbetaL-producers (IMP-1 and -2) were tested using time kill/bactericidal activity methods. Aztreonam at 4, 8 and 16 mg/L was combined with four other beta-lactam antimicrobials (cefepime, ceftazidime, meropenem and piperacillin/tazobactam or ampicillin/sulbactam), each tested at the recognized susceptible breakpoint concentration. Enhanced activity (synergism or additive effect) was observed with four P. aeruginosa strains (IMP-16, VIM-2, SPM-1 and GIM-1 containing strains) and four A. baumannii strains, while antagonism was observed with two P. aeruginosa (IMP-16 and SPM-1-producing strains) and one A. baumannii (non-MbetaL) strain. All other strains showed indifferent interaction (variation of +/- 1 log10 CFU/ml) with any combination evaluated.     

Relationship of Antibiotic Resistance Phenotype to the R-Pyocin Susceptibility Pattern in Clinical Isolates of Pseudomonas aeruginosa

Summary

One hundred sixteen clinical isolates of Pseudotnonas aeruginosa were collected from 7 hospitals in Athens. All strains were studied for their susceptibility to cefotaxime, ceftazidime, carbenicillin, aztreonam, imipenem, nalidixic acid, ciprofloxacin, gentamicin, and chloramphenicol. In addition, the R-pyocin susceptibility pattern was determined and the strains were O-serotyped and tested for their agglutination in acriflavine. The isolates included 53 strains resistant to both gentamicin and carbenicillin, 13 to carbenicillin only, 20 to gentamicin only, and 30 sensitive to gentamicin and carbenicillin. The multiresistant isolates displayed relatively higher resistance to all other antibiotics except aztreonam and cefotaxime. Remarkably 30 out of 53 multiresistant isolates reacted with one pyocin only, namely pyocin R2. This R-pyocin response was not encountered in any other strains of the other antibiotic resistance phenotypes. These isolates belonged to the 0–12 serogroup. The 0–12 serogroup was represented only in a minority of strains giving other R-pyocin reactions. It is interesting that strains reacting with pyocin R5 only were mostly susceptible to antibiotics. The results clearly indicate lipopolysaccharide-core mutations in multiresistant clinical isolates of P. aeruginosa. Despite the fact that the R-pyocin resistance pattern can not define the precise possible defect, the multiple and high level resistance associated with R2-pyocin reaction seems to be an interesting trait.     

In Vitro Activity of Meropenem against Ciprofloxacin-Resistant Enterobacteriaceae and Pseudomonas aeruginosa

Abstract

The in-vitro susceptibilities of a total of 174 ciprofloxacin-resistant Enterobacteriaceae and Pseudomonas aeruginosa were determined. According to the BSAC and NCCLS breakpoints, meropenem, aztreonam, ceftibuten, ceftazidime, imipenem and cefotaxime were the most active (>90%) antimicrobial agents tested against Enterobacteriaceae. Susceptibility of these strains to piperacillin/tazobactam, cefpodoxime and cefixime (84.96%) was higher than that to tobramycin, gentamicin and fosfomycin (50-75%). More than 90% of P. aeruginosa were susceptible to meropenem when both interpretative susceptibility breakpoint criteria were used. Piperacillin, piperacillin/tazobactam and ceftazidime were active against 50-75% of the same strains. Meropenem was the most active antimicrobial tested against all ciprofloxacin-resistant clinical isolates assayed.     

In-vitro susceptibility of clinical isolates of Pseudomonas aeruginosa to beta-lactam and aminoglycoside antibiotics

The in-vitro susceptibilities of 198 isolates of Pseudomonas aeruginosa from clinical human specimens were determined by an agar dilution technique against beta-lactams and aminoglycosides. These isolates were susceptible to imipenem, aztreonam and ceftazidime with the minimum inhibitory concentration (MIC) for 90% of the strains tested being 8, 16 and 8 micrograms/ml, respectively. Aminoglycosides, except amikacin, had low activity (MIC90 greater than 128 micrograms/ml).     

A survey of antimicrobial drug resistance in respiratory tract pathogens,isolated in a northern Italian teaching hospital between 1990 and 1999

Drug susceptibility test results of respiratory tract pathogens, isolated from patients admitted to the Clinic of Respiratory Diseases of the IRCCS San Matteo Hospital, University of Pavia (Italy) between 1990 and 1999, were retrospectively evaluated. A total of 1366 bacterial isolates were collected, including 499 gram-positive and 867 gram-negative strains. In comparison to methicillin-susceptible Staphylococcus aureus, the methicillin-resistant strains (MRSA) showed high levels of resistance to many selected antibiotics, except for glycopeptides. Resistance rates to beta-lactams were high in both Pseudomonas aeruginosa and in the other gram-negative isolates, while aminoglycoside and ciprofloxacin resistance was less than 20%. Some pathogens became more resistant to selected antimicrobials during the observation period, including staphylococci to methicillin, MRSA to ciprofloxacin, P. aeruginosa isolates to imipenem and ciprofloxacin, and the other gram-negative strains to almost all drugs considered, with the exception of cefotaxime and cotrimoxazole.     

Epidemiology of Antibiotic Resistance in Human Isolates of Enterobacteriaceae in Sicily

Summary

The Authors have studied the antimicrobial susceptibility of 1073 clinical isolates of various genera of Enterobacteriaceae (collected during the period July-December 1988) to ampicillin, piperacillin, cefotaxime, ceftazidime, ceftriaxone, aztreonam, imipenem, gentamicin, amikacin, netilmicin, norfloxacin, and ciprofloxacin.

Antimicrobial susceptibility was determined by Bauer--Kirby disk diffusion method. Of 1073 tested bacteria, 704 (65.6%) produced beta-lactamase detectable by nitrocefin test. The highest percentage of resistant strains occurred with ampicillin (70%) followed by piperacillin (24%) and cefotaxime (19%). Lower percentages of resistant strains were found for gentamicin (10%), aztreonam (8%), netilmicin (7%), norfloxacin (5%) and amikacin (4%). Two percent of the strains were resistant to ciprofloxacin and 0.5% to imipenem.

The incidence of resistance in Klebsiella sp., Entero-bacter sp., E.coli and Proteus sp. was compared to that found among 872 strains isolated during July-Dec. 1984. In all the Enterobacteriaceae, mainly Enterobacter sp., the increase in the resistance was high for ampicillin, piperacillin and cefotaxime and lower for gentamicin.     

In- Vitro Activity of Meropenem,a New Carbapenem,Against Imipenem-Resistant Pseudomonas aeruginosa and Xanthomonas maltophilia

Summary

The activity of meropenem, a new carbapenem, as well as imipenem, ceftazidime, aztreonam, tobramycin, amikacin and ciprofloxacin against 18 strains of Xanthomonas maltophilia and 23 strains of Pseudotnonas aeruginosa resistant to imipenem was tested. All strains of X. maltophilia were resistant to both penems. Ceftazidime, tobramycin and ciprofloxacin were the most active antimicrobial agents against this specie. 17% of imipenem-resistant strains of P. aeruginosa were sensitive to meropenem. Ciprofloxacin, amikacin and aztreonam were the most effective agents against these strains.