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PubMed2005

Analysis of Salmonella spp. with resistance to extended-spectrum cephalosporins and fluoroquinolones isolated in North America and Latin America: report from the SENTRY Antimicrobial Surveillance Program (1997-2004).

Emerging antimicrobial-resistant Salmonella spp. requires increased efforts to appropriately test susceptibility. The SENTRY Antimicrobial Surveillance Program monitored Salmonella spp. and detected nalidixic acid-resistant strains with elevated fluoroquinolone minimum inhibitory concentration (MIC) results and strains with extended-spectrum beta-lactamase (ESBL) "phenotypes" over the last 8 years. A total of 786 stool and bloodstream isolates from North American and Latin American medical centers (2001-2003) were tested by reference broth microdilution methods. Genetic analysis was used to further characterize the resistance mechanisms. Twenty-one sites forwarded 89 (11.3%) nalidixic acid-resistant (MIC, > or =32 microg/mL) strains. Nineteen of these isolates were studied to determine mutations in the quinolone resistance-determining region (QRDR). Among the nalidixic acid-resistant Salmonella spp. isolates, fluoroquinolone MIC values were also elevated (8- to 32-fold) compared with "wild-type" strains. Ciprofloxacin and gatifloxacin (MIC(90), 0.5 microg/mL) were more potent than levofloxacin and garenoxacin (1 microg/mL) against nalidixic acid-resistant strains. Single gyrA mutations were responsible for elevated fluoroquinolone MIC values and included D87Y (5), S83F (7), D87N (5), and S83Y (2). During 2001, 9 sites contributed 11 (2.9%) strains that met ESBL screening criteria (> or =2 microg/mL) for aztreonam or ceftazidime or ceftriaxone. ESBL confirmation was evaluated by Etest (AB BIODISK, Solna, Sweden) ESBL strips and the enzymes were characterized by polymerase chain reaction and gene sequencing. The ESBL phenotype isolates had the following MIC patterns: ceftazidime (> or =16 microg/mL), aztreonam (4 to >16 microg/mL), and ceftriaxone (8-32 microg/mL). All strains were susceptible to cefepime, carbapenems, gentamicin, and fluoroquinolones. No strains were inhibited by clavulanic acid consistent with all isolates producing the identified CMY-2, AmpC-like enzyme. Fluoroquinolones may be compromised among isolates with QRDR mutations detected using nalidixic acid as a screening agent. Salmonella spp. with ESBL phenotypes were likely to harbor CMY-2 (not an ESBL) and remain susceptible to cefepime, carbapenems, and fluoroquinolones, which can be used for serious invasive Salmonella spp. infections. Compared with the stool culture isolates, the blood culture isolates had higher QRDR mutations, but remained susceptible to the fluoroquinolones. The blood culture isolates were more susceptible to penicillins (ampicillin and ticarcillin) and not significantly different for ceftriaxone or trimethoprim/sulfamethoxazole susceptibility patterns. No QRDR trends over time were detected in North America, but increased resistance was observed in Latin America.

Anti-Bacterial Agents↗
PubMed2004

Antimicrobial susceptibility profiles of Pseudomonas aeruginosa and Staphylococcus aureus isolated in Italy from patients with hospital-acquired infections.

Here we report the results of the Sentinel Project 2000 and give the susceptibility to selected antibiotics of 108 Pseudomonas aeruginosa and 108 Staphylococcus aureus strains isolated from patients with hospital-acquired lower respiratory tract infections. In P. aeruginosa, susceptibility to aztreonam and ciprofloxacin was lower than 50%. The resistance rate to beta-lactams was up to 25% and to amikacin 15.7%. Blood isolates showed 80-90% susceptibility to all antibiotics tested except for aztreonam and tobramycin. Overall, oxacillin resistance in S. aureus was 45%, reaching 64.3% among the bronchoalveolar lavage isolates, and 42.9% among the blood isolates. These worrying results confirm the need for continuous monitoring of bacterial resistance trends in the hospitals, mainly in ICUs.

Anti-Bacterial Agents↗
PubMed2007

Biochemical characterisation of the CTX-M-14 beta-lactamase.

Cefotaxime-resistant Escherichia coli TUM1121 was isolated from an abscess of an 83-year-old patient. The CTX-M-14 gene was located on a 70 kb plasmid. The enzyme was purified and its activity was analysed. CTX-M-14 was poorly active against ceftazidime and aztreonam. Aztreonam behaved as a competitive inhibitor. Among the tested suicide substrates for class A beta-lactamases, sulbactam was a rather good substrate. Tazobactam and clavulanic acid behaved as inactivators. The interactions between clavulanic acid and CTX-M-14 were characterised by progressive inactivation of the beta-lactamase. Carbapenems such as imipenem, meropenem or doripenem did not behave as inactivators of CTX-M-14, however very small k(cat) values were observed. This result shows that CTX-M-14 is able to hydrolyse carbapenems.

Cloning, Molecular↗
PubMed2003

[Nosocomial diarrhea outbreak due to Clostridium difficile in a vascular surgery department].

INTRODUCTION: Clostridium difficile is considered the most common cause of nosocomial-acquired diarrhea. In Spain this condition is rarely reported. METHODS: Over a five-month period, 35 episodes of C. difficile diarrhea were diagnosed by toxin A detection in stool samples. Case-control studies were designed to assess risk factors for the outbreak. Twelve cases from the vascular surgery department were compared with 24 randomized controls, patients admitted to the same ward during this period, but without diarrhea. Statistical comparisons (SPSS software) were performed with the Student's t and X2 tests (OR with 95% CI). RESULTS: Overall incidence was 3.42 episodes: 48 episodes/1000 admissions to vascular surgery. Among the total, 80% had received antibiotics before admission and the mean number of antibiotics administered was 2.91 per patient. Comparative analyses disclosed that the cases had received a larger number of antibiotics during hospitalization (p 5 0.000) and in the two months before admission (p 5 0.031) than the controls. Clindamycin administered alone (p 5 0.001) or associated with aztreonam (p 0.000) were the most frequently used antibiotic treatments. CONCLUSIONS: C. difficile diarrhea is common in our setting. Diagnosis requires a high index of suspicion. We attribute the nosocomial outbreak in our vascular surgery department to broad-spectrum antibiotic use (clindamycin and aztreonam). Surveillance, together with restriction of antibiotic use was effective for control.

Aged↗
PubMed2002

[Susceptibility of Pseudomonas aeruginosa to antibiotics isolated from patients of intensive care units in France in 1998. Resistant phenotypes to beta-lactams].

Pseudomonas aeruginosa is responsible for nosocomial infections and demonstrates many types of resistance mechanisms to antibiotics. Thus, in vitro susceptibility survey are frequently required. In this study, susceptibility has been assessed on 105 non redundant consecutive strains isolated from ICU's in 18 general hospitals, from 01.02.98 to 30.06.98. Only clinically significant samples have been considered. MICs have been measured for nine beta-lactams, three aminoglycosides, one fluoroquinolone and colistine. For ticarcilline resistant strains, phenotype has been assessed on Mueller-Hinton medium supplemented with beta-lactamases inhibitor. Transferable beta-lactamases has been identified using pl and PCR. MIC 50 and MIC 90 (mg/L) for beta-lactams are the following (MIC 50-->90): ticarcilline (16-->512), ticarcilline + clavulanic acid (16-->512), piperacilline (4-->512), pipéracilline + tazobactam (4-->64), aztreonam (4-->16), cefsulodine (4-->32), ceftazidime (2-->16), cefepime (4-->16), imipeneme (1-->8). For aminoglycosides: gentamicine (2-->32), tobramycine (1-->32), amikacine (4-->16). For ciprofloxacine (0.25-->32) and colistine (0.5-->2). According to CA-SFM break points recommendations, 50% of isolated strains are resistant to gentamicine, one out of three for ticarcilline + clavulanic acid (29%), one out of four for tobramycine (25%) and ciprofloxacine (25%), one out of ten for amikacine (9%), tazocilline (8%) and imipeneme (9%). Resistance to ceftazidime and aztreonam is uncommon (respectively 2%-1%) and never observed for cefepim. For ticarcilline resistant strains, (38% of total isolates) the following phenotypes have been detected: 6.7% non enzymatic resistance, 15.2% transferable beta-lactamase (TEM 4.8%, CARB 4.8%, TEM + CARB 4.8% and OXA-10 and derivated 0.9%) and 16.2% high level cephalosporinase. Extended-spectrum beta-lactamase has never been detected. TEM beta-lactamase is associated with resistance to amikacine and ciprofloxacine.

Aminoglycosides↗
PubMed1997

Activity of selected beta-lactams, ciprofloxacin, and amikacin against different Acinetobacter baumannii biotypes from Chilean hospitals.

The activity of some third generation cephalosporins, aztreonam, imipenem, ciprofloxacin, and amikacin against isolates of Acinetobacter baumannii of various biotypes has been studied. The isolates, independently of the biotype, exhibited a broad multiresistance against cephalosporins. Ceftazidime was the most active and cefoperazone the least active compound. Aztreonam also showed low activity and no imipenem-resistant strains were found. Ciprofloxacin and amikacin were somewhat more active than cephalosporins, but resistant isolates were also frequent. Isolates of Biotypes 9 and 8 exhibited broader multiresistance than those of Biotype 6 and "other."

Acinetobacter↗
PubMed1997

Critical evaluation of the Vitek GNS F6 card results compared to standardized, reference susceptibility test methods.

A large number of Enterobacteriaceae (291 unselected and 30 clinical challenge isolates) were used to evaluate the accuracy of the Vitek GNS-F6 susceptibility testing card for 10 antimicrobial agents (ampicillin, ampicillin/sulbactam, aztreonam, ciprofloxacin, imipenem, mezlocillin, ofloxacin, piperacillin, ticarcillin, and ticarcillin/clavulanate). Results were compared to reference broth microdilution and disk diffusion methods. Highest interpretive error on initial processing were observed with ticarcillin/clavulanate (very major false-susceptible error, 3.4%), imipenem (major false-resistant error, 1.9%), and ampicillin/sulbactam (minor error, 15.9%). Repeat testing resolved many very major errors (21 of 41 results), and the overall accuracy rate was improved from 92.1 to 93.4%. Analysis of all minor interpretive errors demonstrated that the trend for Vitek was to report slightly lower MICs (6 of 10 drugs; 97 of 159 results) in comparison to the reference test results. If a heavy inoculum was used in the Vitek cards, false resistance was observed more frequently with aztreonam and penicillins. These data demonstrate that susceptibility testing accuracy with Vitek GNS-F6 card based on categorical agreement varies from 83.2% (ampicillin/sulbactam) to 99.4% (ciprofloxacin) when testing enteric bacilli. Some antimicrobial agents (beta-lactamase inhibitor/penicillin combinations, antipseudomonal penicillins) may require slight modification of interpretive software. Finally, the overall accuracy of the Vitek System was greater than 91% for 9 of 10 drugs tested with a very low, acceptable rate of false-susceptible error (0.8%).

Anti-Bacterial Agents↗
PubMed1999

Multicenter evaluation of the antimicrobial activity for seven broad-spectrum beta-lactams in Turkey using the Etest method. Turkish Antimicrobial Resistance Study Group.

From March through July 1997, a nine laboratory surveillance project was initiated in Turkey to monitor the potency and spectrum of seven broad-spectrum antimicrobial agents (cefepime, ceftazidime, cefotaxime, imipenem, aztreonam, cefoperazone/sulbactam, and ticarcillin/clavulanate) tested against approximately 100 organisms (average 82; range 70 to 95 isolates) per participant center (736 strains). Eleven groups of organisms were tested by the Etest method (AB BIODISK, Solna, Sweden) with results validated by concurrent quality control strain analysis. Results from all centers were tabulated and 91.1% of quality assurance tests were within ranges recommended by the National Committee for Clinical Laboratory Standards. Among the seven beta-lactam-class drugs tested, imipenem and cefepime were the most active beta-lactams tested against all isolates. Overall, the rank order of susceptibility of the seven agents was imipenem > cefepime > cefoperazone/sulbactam > ceftazidime > cefotaxime > aztreonam > ticarcillin/clavulanate. Both cefepime and imipenem were active against ceftazidime-resistant strains of Enterobacteriaceae as well as against Streptococcus spp. and oxacillin-susceptible Staphylococcus aureus. Resistance phenotypes consistent with extended spectrum beta-lactamases were documented among Escherichia coli and Klebsiella spp., and profiles consistent with stably derepressed Bush-Jacoby-Mederios group 1 (Amp C) cephalosporinases were common among Enterobacter spp., Citrobacter spp., and Serratia spp. These data should be used to guide empiric therapy with beta-lactams in Turkey, and additionally will provide a reference statistical baseline to which future national studies of drugs in this class can be compared.

Anti-Bacterial Agents↗
PubMed1999

Multicenter evaluation of antimicrobial resistance to six broad-spectrum beta-lactams in Colombia: comparison of data from 1997 and 1998 using the Etest method. The Colombian Antimicrobial Resistance Study Group.

The minimum inhibitory concentrations of six broad-spectrum beta-lactam antimicrobial agents were determined in 1998 by use of the Etest versus a total of 823 bacteria in 11 Colombian hospital laboratories. These data were compared with results of a similar study conducted in 1997. The organisms tested included 532 recent clinical isolates of Enterobacteriaceae, 108 Pseudomonas aeruginosa, 94 Acinetobacter species, and 89 oxacillin-susceptible Staphylococcus aureus. Extended-spectrum beta-lactamase production was noted among 27.8 to 33.9% of Escherichia coli isolates and 41.7 to 46.7% of Klebsiella spp. isolates. Hyperproduction of Amp C cephalosporinases was observed with 10.5 to 31.4% of isolates of Enterobacter spp., Serratia spp., and Citrobacter spp. An increase in resistance to all of the beta-lactams was observed among Enterobacteriaceae, Acinetobacter spp. and P. aeruginosa when 1998 results were compared with those obtained in 1997. The overall rank order of activity of the six beta-lactams tested in 1998 versus all clinical isolates was imipenem (93.2% susceptible) > cefoperazone/sulbactam (84.1%) > cefepime (80.9%) > ceftazidime (70.7%) > aztreonam (65.7%) > cefotaxime (65.6%). In contrast, the rank order of these same agents tested against a similar collection of Colombian isolates in 1997 was imipenem (96.6% susceptible) > cefepime (93.6%) > cefoperazone/sulbactam (90.5%) > cefotaxime (74.9%) > aztreonam (74.3%) > ceftazidime (73.2%).

Colombia↗
PubMed2000

Susceptibility of Polish clinical strains of Yersinia enterocolitica serotype O3 to antibiotics.

A total of 199 clinical strains of Yersinia enterocolitica serotype O3, biotype 4 were tested for their susceptibility to antibiotics (158 strains carried the virulence plasmid pYV and 41 strains did not). A total of 114 isolates were tested by a standard disk diffusion method for 21 antibiotics. Almost all strains tested were resistant to ampicillin and cefazolin and susceptible to amoxycillin/clavulanate, cefaclor, cefamandole, cefuroxime, cefotaxime, ceftriaxone, aztreonam, imipenem, gentamicin, amikacin, netilmicin, tetracycline, doxycycline, chloramphenicol, ciprofloxacin, sulphamethoxazole, trimethoprim, co-trimoxazole and furazolidone. In addition, minimal inhibitory concentrations of 15 antibiotics were determined by the agar dilution method for all 199 strains (158 carrying plasmid pYV and 41 strains that did not). Third-generation cephalosporins such as cefotaxime and ceftriaxone and a fluoroquinolone (ciprofloxacin) were the most active antimicrobial agents tested followed by aztreonam, imipenem, trimethoprim, tetracycline, gentamicin, chloramphenicol, amoxycillin/clavulanate, cefaclor, cefuroxime, amikacin, furazolidone and sulphamethoxazole. The present study demonstrated a high susceptibility of clinical strains of Y. enterocolitica to most of the tested antibiotics. In general there was no significant difference between susceptibility to antibacterial agents of strains with or without plasmid pYV.

Drug Resistance, Microbial↗
PubMed1995

A bi-modal transfer of antibiotic resistance by conjugation and transduction from an imipenem-resistant strain of Pseudomonas aeruginosa.

A strain of Pseudomonas aeruginosa No. 76/17224 resistant to carbenicillin (CAR), kanamycin (KAN), cefalotin (CLO), cefotaxime (CTX), ceftazidime (CAZ), aztreonam (AZA), imipenem (IMI) and ofloxacin (OFL) was isolated at the Frankfurt University Hospital. This strain transferred, by conjugation, antibiotic resistance determinants to CAR, CLO, CTX, CAZ and AZA. In addition, we isolated a wild-type phage from this strain. We used this phage to transduce the resistance determinants to four susceptible recipient strains of P. aeruginosa. The phage designated AP-76 transduced the resistance determinants to KAN, CAR, CTX and CAZ to all four recipient strains. Imipenem and aztreonam resistance determinants were directly transduced to two recipient strains only, i.e. to PAO-1670 and ML-1008. The IMI resistance determinant was not co-transduced with any other resistance determinant(s) selected directly. Our results indicated that IMI resistance determinant was not associated with other resistance determinants. IMI was actively hydrolysed by IMI-resistant transductants and this hydrolysis was inhibited by clavulanate but not by EDTA.

Bacteriophages↗
PubMed1995

Control of infection with multiple antibiotic resistant bacteria in a hospital renal unit: the value of plasmid characterization.

An outbreak of infections due to multiple antibiotic-resistant bacteria took place over a period of approximately 18 months in a renal unit. Strains of Escherichia coli, Enterobacter aerogenes, Klebsiella pneumoniae, Citrobacter spp. and Pseudomonas spp. were involved, and a variety of antibiotic resistances was encountered. Closely related plasmids encoding resistance to aztreonam, ceftazidime and piperacillin, possibly derived from an archetypal plasmid of 105 kb were found in the majority of isolates examined. After limiting the use of aztreonam the incidence of new patient isolates of multiple-resistant organisms was greatly reduced. This study demonstrated how molecular studies can contribute to the control of an outbreak situation in a hospital unit by providing an impetus to reduce the use of specific antibiotics.

Cross Infection↗
PubMed1989

Purification of a class C A-type beta-lactamase from a derepressed strain of Enterobacter cloacae. Comparison of the wild-type and mutant enzyme with those from strains P99, 208 and GN7471.

Enterobacter cloacae strain 5822 expresses low levels of a class C beta-lactamase which can be induced 100-fold by imipenem. Mutants that constitutively express high levels of beta-lactamase can be selected on aztreonam or cefotaxime. The beta-lactamase from one such mutant (5822M2) has been purified to homogeneity and compared on the basis of subunit Mr, pI, substrate specificity, inhibitor sensitivity and immunological cross-reactivity with the enzyme from strains P99, GN7471 and 208, which have been studied previously. The enzyme from strain 5822M2 is clearly related to these other forms and is of the A-type according to the criteria of Seeberg, Tolxdorff-Neutzling & Wiedemann [Antimicrob. Agents Chemother. (1983) 23, 918-925]. The enzyme from the wild-type strain (5822) is shown to be identical to that found in the depressed strain (5822M2), indicating that the mutation is in a regulatory gene. A detailed analysis of the kinetics of the enzyme from strain 5822M2 shows that all of the beta-lactams studied are substrates and that a mechanism involving the formation of an acyl-enzyme is probably applicable in every case. The substrates however can clearly be grouped into two classes, i.e. 'good' substrates with kcat. values of 80-1200 s-1 and 'poor' substrates/good inhibitors with kcat. values of 0.009-0.00007 s-1. The permeability barrier to aztreonam is 4-fold less in the derepressed strain when compared with the wild-type strain. This is associated with significant changes in the expression of outer membrane porins. The observed resistance in the derepressed mutant appears to be linked to the elevated levels of beta-lactamase (3000-fold) rather than to the modest changes in the permeability barrier.

Bacterial Outer Membrane Proteins↗
PubMed1992

Mutations altering substrate specificity in OHIO-1, and SHV-1 family beta-lactamase.

The OHIO-1 beta-lactamase does not normally hydrolyse oxyimino-beta-lactam substrates like cefotaxime, ceftriaxone, ceftazidime or aztreonam. We were able to select spontaneous mutants of an OHIO-1-bearing strain of Escherichia coli using the antibiotic substrates listed above by enrichment methods of frequencies of 10(-8)-10(-10) for all antibiotics except ceftazidime (frequency less than 10(-10)). Most mutants with increased resistance to the other beta-lactams were also more resistant to ceftazidime. Mutations identified by DNA sequencing included a Gly238----Ser238 substitution identical with the SHV-2 mutation previously described, cysteine and valine substitutions at the identical site, and a Gly242----Cys242 substitution. The Cys238 and Cys242 mutant enzymes had less affinity for aztreonam than had the other mutant enzymes. Hydrolysis of cefotaxime, but not cephaloridine, by the cysteine-substituted enzymes was inhibited by p-chloromercuribenzoate. The mutant enzymes had, in general, greater affinity for the mechanism-based inhibitors sulbactam, clavulanic acid and tazobactam. These results suggest two non-mutually exclusive hypotheses for the structural role of substitutions in this area of the enzyme. Either potential hydrogen-bond donors, such as serine and cysteine, interact directly with the beta-lactam molecules, or the steric bulk of these substitutions distorts the beta-pleated sheet such that the beta-lactam is held in a position favourable for stable binding and catalysis. Finally, our data raise questions about a strategy relying on oligonucleotide-probe technology to detect such mutations, because of the variety of substitutions that give rise to similar phenotypes.

Amino Acid Sequence↗
PubMed2001

Effect of inoculum size on the antibacterial activity of cefpirome and cefepime against Klebsiella pneumoniae strains producing SHV extended-spectrum beta-lactamases.

OBJECTIVE: To determine the effects of varying inoculum size on in vitro susceptibility of SHV extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae isolates to cefepime and cefpirome compared to previously established cephalosporins and aztreonam. METHODS: Antibiotic susceptibilities were determined by disk diffusion test, the MIC broth microdilution method, and time-kill studies with two different inocula of 10(5) and 10(7) CFU/mL. The strains were classified into four groups according to the type of beta-lactamase they produce: SHV-2, SHV-5, SHV-12, and ESBL-negative klebsiellae. RESULTS: The antibacterial activities of cefpirome and cefepime were comparable to that of cefotaxime, but were significantly greater than those of ceftazidime and aztreonam. An inoculum effect was detected for all broad-spectrum cephalosporins, but it was more pronounced with cefpirome and cefepime compared to older cephalosporins. The disk diffusion test proved to be not sensitive enough for the detection of an inoculum effect, particularly for cefepime. CONCLUSIONS: The present study found that most SHV-producing klebsiellae have MICs of cefpirome that imply susceptibility at the moderate inoculum size, in spite of the fact that, according to the NCCLS, all ESBL producers should be considered resistant to all cephalosporins, independent of MIC values. With a high inoculum, most of the strains seemed to be resistant to both antibiotics. Furthermore, the bactericidal activities of cefpirome and cefepime against isogenic Escherichia coli strains producing SHV-2, SHV-4 and SHV-5 beta-lactamases, respectively, were also inoculum dependent. Bactericidal activity against SHV-4 and SHV-5 beta-lactamase producers was obtained only at the moderate inoculum, whereas the SHV-2 beta-lactamase producer was efficiently killed with both antibiotics, regardless of the inoculum size.

Cefepime↗
PubMed2002

Transferable plasmid mediating resistance to multiple antimicrobial agents in Klebsiella pneumoniae isolates in Greece.

OBJECTIVE: To investigate the underlying resistance mechanisms in 10 Klebsiella pneumoniae isolates. METHODS: Ten K. pneumoniae strains according to distinct bacteriocin typing and REP-PCR, were examined for their plasmid content, their ability to transfer their resistance to aminoglycosides and third-generation cephalosporins, and their production of aminoglycoside-modifying enzymes and beta-lactamases. RESULTS: Transfer of resistance to the above-mentioned antibiotics as well as to co-trimoxazole and tetracycline in Escherichia coli strain RC 85 at a frequency of 5-106 was achieved for all strains by conjugation. Similar strains harbor a self-transferable multiresistant plasmid (80 kb) with similar EcoRI and HindIII restriction patterns. This plasmid encodes an extended-spectrum beta-lactamase which confers high-level resistance to third-generation cephalosporins and aztreonam. It produces SHV-5 beta-lactamase, as demonstrated by isoelectric focusing and DNA sequencing. Aminoglycoside resistance was co-transferred, and AAC(6')-I, mediating resistance to gentamicin, tobramycin, netilmicin and amikacin, and AAC(3)-I, mediating resistance to gentamicin and sisomycin, were encoded in all isolates and their transconjugants, while APH(3')-I, mediating resistance to kanamycin and neomycin, was encoded in seven strains. CONCLUSIONS: It appears that a multiresistant transferable plasmid encoding the SHV-5 beta-lactamase, causing unusually high resistance to ceftazidime and aztreonam, and the combination AAC(6')-I + AAC(3)-I of acetylating enzymes causing, also resistance to all clinically available aminoglycosides, is established in K. pneumoniae in Greece.

Anti-Bacterial Agents↗
PubMed2002

Comparison of screening methods for TEM- and SHV-derived extended-spectrum beta-lactamase detection.

OBJECTIVE: To compare common extended-spectrum beta-lactamase (ESBL) screening methods and beta-lactams for their ability to detect TEM- and SHV-related ESBL enzymes. METHODS: This study compared disk diffusion testing by NCCLS methodology, the Jarlier double disk test, a disk-on-disk test, a modified three-dimensional test and the E test method for their sensitivity and specificity in detecting TEM- and SHV-related ESBL producers. Three negative and 22 positive controls were studied. These were two Klebsiella pneumoniae and 23 Escherichia coli transconjugants. Seventeen beta-lactam antibiotics were tested: cefamandole, cefotetan, cefoxitin, cefuroxime, cefixime, cefoperazone, cefotaxime, cefpodoxime, cefsulodin, ceftazidime, ceftibuten, ceftizoxime, ceftriaxone, moxalactam, cefepime, cefpirome and aztreonam. RESULTS: NCCLS disk diffusion was 14% sensitive with ceftriaxone, 36% with cefotaxime, 64% with aztreonam, 68% with cefpodoxime, and 73% with ceftazidime. Cefoperazone, cefamandole, cefpodoxime and cefpirome showed 91% sensitivity using the Jarlier test. Using the disk-on-disk test, cefsulodin showed 95% sensitivity, and cefoperazone, cefepime and cefamandole showed 91% sensitivity. With the modified three-dimensional test, cefoperazone, cefpodoxime and cefpirome showed 91% sensitivity. CONCLUSIONS: For practical reasons, we would recommend use of either the Jarlier test or the commercial cephalosporin disks containing clavulanic acid to screen for ESBL producers. Cefoperazone, cefamandole, cefpodoxime and cefpirome showed good sensitivity across the methods tested.

Anti-Bacterial Agents↗
PubMed2002

Analysis of antimicrobial resistance among gram-negative bacilli and antimicrobial use in intensive care unit patients for 5 years in a Veterans Affairs medical center.

BACKGROUND: Gram-negative bacilli antimicrobial resistance remains a significant problem for patients in the intensive care unit (ICU). Patterns of antimicrobial use may be a contributing factor. METHODS: Gram-negative bacilli from ICU patients of a Veterans Affairs (VA) medical center were tested to determine in vitro antimicrobial susceptibility (205 isolates in 1995 and 209 in 1999). Antimicrobial use was calculated from 1995 through 1999. RESULTS: For Pseudomonas aeruginosa, significant declines in susceptibility to ciprofloxacin (medical ICU [MICU] individually and all units) and aztreonam (all units) were noted. For gram-negative bacilli that was non-P aeruginosa, significant increases in susceptibility to ceftazidime (MICU, surgical ICU, and all units), gentamicin (all units), and ticarcillin/clavulanate (MICU) were noted. The most notable trends in antimicrobial usage were sharp increases in fluoroquinolone use in the MICU and surgical ICU and substantial decreases in the use of third-generation cephalosporins, monobactams, and aminoglycosides. In each instance of significant change in the susceptibility of a group of organisms to an antibiotic, there was a corresponding inverse change in the use of the antibiotic and/or its antimicrobial category (except for aztreonam). CONCLUSIONS: Significant changes in antimicrobial use may affect certain gram-negative bacilli antimicrobial susceptibilities in ICUs.

Anti-Bacterial Agents↗