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PubMed2002

Antibiotic resistance and molecular typing of Pseudomonas aeruginosa: focus on imipenem.

Susceptibility tests by disk diffusion and by E-test and molecular typing by macrorestriction analysis were performed to determine the relatedness of Pseudomonas aeruginosa isolates from three distinct hospitals. The resistance profile of 124 isolates to 8 antimicrobial agents was determined in three different hospitals, in Porto Alegre, Brazil. Frequencies of susceptibility ranged from 43.9% for carbenicillin to 87.7% for ceftazidime. Cross-resistance data of imipenem-resistant isolates indicated that most (70%) were also resistant to carbenicillin, although 30% remained susceptible to ceftazidime and cefepime. In general, susceptibility profiles were not able to determine relatedness among isolates of P. aeruginosa. On the other hand, molecular typing by macrorestriction analysis demonstrated high discriminatory power and identified 66 strains among 72 isolates of P. aeruginosa. Imipenem-susceptible isolates were all different. However, identical clones of imipenem-resistant isolates were found in two of the hospitals, despite variable response to other antibiotics. No clustering of infection among the different medical centers was observed. In conclusion, clones of P. aeruginosa did not spread among the different hospitals in our city even though related isolates of imipenem-resistant P. aeruginosa were found.

Bacterial Typing Techniques↗
PubMed2000

[Pulmonary Nocardia otitidiscaviarum infection in an immunocompetent host].

A rare case of pulmonary Nocardia otitidiscaviarum (N. otitidiscaviarum) was encountered in an immunocompetent host. A 74-year-old man was admitted to our hospital with a high fever and a productive cough. His chest radiograph and CT scan revealed infiltrative shadows in the right middle and lower lung fields. Although several antibiotics (third-generation cephalosporin, minocycline, imipenem) were administered, the fever and cough persisted, and C-reactive protein remained elevated. Repeated sputum cultures showed normal flora, so a transbronchial lung biopsy and bronchoalveolar lavage (BAL) were performed bronchoscopically at the right S5. The BAL fluid contained acid-fast, branching filamentous structures. The microorganism was identified as N. otitidiscaviarum by the Research Center for Pathogenic Fungi and Microbial Toxicoses (Chiba University). Trimethoprim-sulfamethoxazole was therefore administered, but the fever continued to rise daily, and C-reactive protein remained elevated. This isolated N. otitidiscaviarum showed resistance to multiple antimicrobial agents in vitro when examined by the disk diffusion method, and so, on the basis of the antibiogram, the patient was treated with clarithromycin (oral, 600 mg/day) plus amikacin (400 mg/day), which proved successful. Testing for pulmonary nocardiosis should be added to the differential diagnosis procedures for refractory pneumonia as an opportunistic infection and for community-acquired pneumonia.

Aged↗
PubMed1991

Haemophilus influenzae resistance in a community hospital.

We prospectively tabulated all isolates of Haemophilus influenzae at DeKalb Medical Center from 1987 through 1989 to assess the occurrence of antibiotic resistance in patients of different ages. Of 325 total strains isolated, 24% produced beta-lactamase, rendering them resistant to ampicillin and amoxicillin. Antibiotic resistance was as common in patients older than age 60 (24%) as in younger patients (23%). Sensitivity testing by disk diffusion and microdilution techniques on 71 isolates (37 beta-lactamase-positive) showed uniform susceptibility to cefuroxime, cefotaxime, amoxicillin/clavulanate, cefaclor, and chloramphenicol, but three beta-lactamase-positive isolates were resistant to trimethoprim/sulfamethoxazole. The high rate of ampicillin resistance noted in elderly patients has implications for the choice of antimicrobial therapy for these infections.

Adolescent↗
PubMed1994

[Nationwide survey on susceptibilities of clinical isolates from urinary tract to antimicrobial agents in Japan, 1991].

This study was conducted to investigate susceptibilities of urinary tract isolates to antimicrobial agents examined at 123 hospital laboratories in Japan from September to December in 1991. In this study, identification and susceptibility testing were carried out at each laboratory. The susceptibility testing was performed according to the disk diffusion method recommended by National Committee for Clinical Laboratory Standards. MRSA showed high resistance rates to all agents tested except to minocycline (MINO). MSSA had good susceptibility to imipenem (IPM) and cephalosporins with susceptibility rates higher than 90%. Enterococcus faecalis was susceptible to IPM, ampicillin and piperacillin (PIPC) and highly resistant to cephalosporins, gentamicin (GM), erythromycin, clindamycin and MINO. Escherichia coli, Klebsiella pneumoniae and Proteus mirabilis were susceptible to beta-lactam drugs, GM and ofloxacin (OFLX). High susceptibility rates were observed for strains of Enterobacter cloacae, Citrobacter freundii to IPM, GM, and OFLX and of Serratia marcescens for IPM and GM. Pseudomonas aeruginosa strains were highly susceptible to IPM, ceftazidime, AMK, cefsulodin, cefoperazone, PIPC in this order.

Anti-Bacterial Agents↗
PubMed1980

Clinical laboratory evaluation of the Abbott MS-2 automated antimicrobial susceptibility testing system: report of a collaborative study.

The MS-2 system (Abbott Diagnostics, Division of Abbott Laboratories, Dallas, Tex.) was evaluated for its efficacy in determining the susceptibilities of both clinical and selected challenge (nonfastidious, facultative, and aerobic) isolates. The MS-2 results were compared with standard Kirby-Bauer disk diffusion and microdilution results by using fresh clinical isolates. For gram-positive isolates other than enterococci, overall agreement between MS-2 and reference results was 93 to 98%. With enterococci, MS-2 agreement with disk diffusion was 68% but with microdilution was 86% (agreement between disk diffusion and microdilution was 73%). The main discrepancies with enterococci were with cephalothin, penicillin, gentamicin, and kanamycin. With clinical gram-negative isolates, the overall agreement was 91 to 93%, with most discrepancies occurring with Enterobacter spp. and beta-lactam antibiotics (MS-2 versus disk diffusion, 84%; MS-2 versus microdilution, 84%; disk diffusion versus microdilution, 87%) and with Serratia spp. and colistin (false-susceptible results). The agreement of MS-2 results with established reference antibiograms of a special collection of challenge strains was 91 to 97% for the gram-positive cocci and 86 to 98% for the gram-negative strains. (With Enterobacter spp., agreement was 86%, but was greater than 90% for all other organism groups.) Of the 98 finite MS-2 minimum inhibitory concentrations (MICs) that could be directly compared with microdilution MICs, 77 (79%) were within +/- 1 well of the geometric mean microdilution MIC. MS-2 analysis time ranged from 2.8 to 6.5 h (mean, 4.2 h). On the basis of these results, we conclude that the MS-2 can be expected to yield rapid and accurate results with most nonfastidious, facultative, and aerobic pathogens.

Anti-Bacterial Agents↗
PubMed2002

Simultaneous detection of the mecA and ileS-2 genes in coagulase-negative staphylococci isolated from Brazilian hospitals by multiplex PCR.

Coagulase-negative Staphylococcus spp. (CNS) has been associated with primary bloodstream infections and implanted medical devices. Its importance is increasing due to the acquisition of resistance to oxacillin (Oxa) and, recently, resistance to mupirocin (Mup). Mupirocin, a topical antimicrobial, has been used in the prevention of staphylococci catheter colonization. Susceptibility to Oxa and Mup was analyzed by different testing methods in clinical CNS isolates. Among 112 CNS strains, 69 (61.6%) were Oxa(R) by the disk diffusion (DD) method and 72 (64.2%) grew on the oxacillin agar screen plate. S. epidermidis and S. haemolyticus presented high rates of oxacillin resistance, 75.4% and 96.1%, respectively. Twenty four (21.4%) strains were Mup(R) by the DD test and 21 of them (87.5%) were identified as S. epidermidis. The detection of the mecA and ileS-2 genes, determined by multiplex-PCR, showed that 72 (64.2%) CNS strains possessed the mecA gene, while 16 (14.3%) possessed the ileS-2 gene. Fifteen of these strains presented the two resistance genes simultaneously. The isolates containing the ileS-2 gene presented a minimum inhibitory concentration (MIC) >1024 microg/mL in the E-test, while low-level mupirocin resistance (MICs of 12-16 microg/mL) was observed in those strains without ileS-2. The resistances to high and low levels of mupirocin could not be distinguished when the DD test was used. The analysis of the Mup(R) S. epidermidis strains by Pulsed Field Gel Electrophoresis showed that 17 (80.9%) strains belonged to one of two patterns (A and B), which have been shown to be prevalent in hospitals in Rio de Janeiro. This report showed that the PCR method for detection of oxacillin and mupirocin resistance in CNS is necessary to determine accurate rates of these resistance, and will can help in the staphylococcal infections prevention and control policies in Brazil.

Bacterial Proteins↗
PubMed2006

[Antimicrobial susceptibility and serotype distribution of pneumococci strains isolated from meningitis patients].

Treatment of life threatening pneumococcal infections such as meningitis has recently become problematic due to the emergence of antibiotic resistant strains. Antimicrobial susceptibility data usually derived from the studies that included all clinical pneumococcal isolates. However, resistance patterns of this microorganism isolated from meningitis cases in our country are not exactly known. The aim of this study was to determine the antimicrobial susceptibility and serotypes of Streptococcus pneumoniae strains isolated from meningitis cases. This retrospective study was designed in three university hospitals in Turkey and 72 pneumococci isolated from patients with meningitis were evaluated. In this study disk diffusion test and E-test methods were used to determine the susceptibility of pneumococci to some antibiotics. All S. pneumoniae isolates were serotyped using Quellung reaction. Although resistance for oxacillin was found by disc diffusion method in 11 isolates, only six of them were found to be resistant by E-test. By the latter procedure, no resistance was recorded against ceftriaxone and meropenem, while chloramphenicol resistance was found as 1.4%. In our study, erythromycin, ciprofloxacin and levofloxacin resistance were 2.8%, TMP-SMX resistance was 26.4%, while no vancomycin resistance was detected by disk diffusion. In evaluation of 72 pneumococci, we found 16 different serotypes and four isolates could not be serotyped. The serogroup 23 (n: 19) was the most common one followed by serotype 19 (n: 9) and serotype 14 (n: 7). Of six resistant isolates, three pneumococci were serogroup 23 and the remaining were from three different serotype/serogroups 11, 14 and 19. As a result penicillin resistance in pneumococci isolated from meningitis was low and there was no resistance to ceftriaxone. It seems that ceftriaxone is an appropriate choice for empirical treatment of meningitis in our patients. These findings also revealed that pneumococcal polysaccharide capsule vaccines in use cover most of the invasive pneumococcal serotypes.

Adolescent↗
PubMed2006

Antibiotic-resistance patterns and frequency of extended-spectrum beta-lactamase-producing isolates of Klebsiella pneumoniae in Tehran.

BACKGROUND: Extended-spectrum beta-lactamase (ESBL)-producing strains of Klebsiella pneumoniae have caused major therapeutic problems worldwide since the majority are resistant to various antibiotics. In this study, an investigation was conducted regarding antibiotic-resistant patterns of 128 isolates of K pneumonile cultured from Iranian patients at two teaching hospitals during 2004-2005. MATERIAL/METHODS: The susceptibility of isolates to 21 antimicrobial agents was determined using the disk diffusion method. Disks containing ceftazidime, cefotaxime, ceftazidime/clavulanic acid, and cefotaxime/clavulanic acid were used in the phenotypic confirmatory (PCT) method to detect ESBL isolates. A comparison between the confirmatory method and double-disk synergy test (aztreonam, ceftazidime, ceftriaxone, cefotaxime, and amoxicillin/clavulanic acid) was also made to assign the appropriate method of detection for ESBLs. The E-test was used to determine the susceptibility of isolates to cefepime. RESULTS: All strains were susceptible to imipenem and meropenem. Resistance to ciprofloxacin and gentamicin were found in 37% (n=47) and 33% (n=42) of isolates, respectively. Production of ESBL was detected in 44.5% of isolates. Resistance to cefepime was found in 40% of isolates. CONCLUSIONS: The prevalence of ESBL strains in the study hospitals is high. The double-disk synergy method is not preferable in successfully detecting ESBL strains. More importantly, 33% of ESBL strains were also resistant to ciprofloxacin and aminoglycosides. Based on the laboratory results, it is recommended that prescription of cephalosporins be restricted to susceptible isolates and that the usage of other effective antibiotics be considered.

Anti-Infective Agents↗
PubMed1999

Antimicrobial activity and spectrum of SCH27899 (Ziracin) tested against gram-positive species including recommendations for routine susceptibility testing methods and quality control. Quality Control Study Group.

SCH27899 is an oligosaccharide, everninomicin antibiotic with activity primarily against Gram-positive pathogens. The activity of SCH27899 was evaluated against 360 routine clinical isolates by the broth microdilution (BMD), agar dilution (AD), disk diffusion (DD), and Etest (AB BIODISK, Solna, Sweden) methods. In addition, results from a nine center SCH27899 quality control (QC) trial were used to establish QC ranges. SCH27899 MICs for 330 Gram-Positive strains, including multiply-resistant staphylococci and enterococci, ranged from 0.015 to 1 microgram/ml with MIC90s of 0.12 to 0.5 microgram/ ml. SCH27899 had no measurable activity against the 30 selected Gram-negative strains tested (MICs, > 256 micrograms/ml), with the exception of Moraxella catarrhalis MICs, 0.12 microgram/ ml). Etest MICs for SCH27899 correlated well with AD and BMD results with > 90% of MICs within +/- one log2 dilutions of the reference test results. Three disk concentrations (2.5-, 5-, 10-microgram) of SCH27899 were evaluated, but minimal difference of zone diameters between disk drug contents was observed (+/- 2 mm). SCH27899 disk zone diameters correlated poorly with reference MICs due to small zone diameters (range, 11 to 22 mm) attributed to poor diffusion through agar mediums, a product of this compound's high molecular weight and solubility. The use of the DD method for SCH27899 was not recommended. The proposed MIC quality assurance limits for SCH27899 using Staphylococcus aureus ATCC 29213 and Enterococcus faecalis ATCC 29212 was 0.06 to 0.25 microgram/ml for both QC strains and methods. SCH27899 appears to be a eveminomicin-derivative widely active against important Gram-positive cocci, and in vitro dilution testing methods would be preferred for clinical use, validated by the recommended MIC control ranges cited in this report.

Aminoglycosides↗
PubMed1989

Structure-activity relationships of hydrazono derivatives of biological interest.

The following hydrazono derivatives (I-XXIII) of type (A), (formula; see text) where: X = NO2 (II, IV, VI, VIII, X, XIV-XXIII), X = H (I, III, V, VII, IX, XI, XII, XIII), and Y = H (I, II); 3-Cl (III, IV); 4-Cl (V, VI); 3,4-Cl2 (VII, VIII); 2,6-Cl2 (IX, X); 2-NO2 (XI); 3-NO2 (XII); 4-NO2 (XIII, XIV); 2-F (XV); 3-F (XVI); 4-F (XVII); 2-OH (XVIII); 4-OH (XIX); 2,4-(OH)2(XX); 2,4,6-(OH)3(XXI); 2,3-(OH,NO2) (XXII); 2,4-(NO2)2 (XXIII), were prepared and tested for antibacterial and antifungal activity. All of these compounds were prepared in satisfactory yield by reaction of aromatic aldehydes with 2-furoyl and 5-nitro-2-furoyl hydrazide. The hydrazono derivatives I-XXIII prepared in this investigation were screened for antimicrobial activity by a disk-diffusion assay (Kirby-Bauer modified). The organisms used were laboratory cultures of S. aureus, S. -haemoliticus, B. subtilis, M. paratuberculosis, E. coli, S. typhi, Ps. aeruginosa, K1. pneumoniae, A. niger, S. cerevisiae, C. albicans. The results of this study showed that a number of the prepared hydrazono derivatives exhibited varying degrees of activity against Gram-positive and Gram-negative bacteria. Compounds IV and XV possessed broad spectrum "in vitro" against Gram-positive and Gram-negative bacteria. Compounds XII greater than IV greater than XV showed inhibitory activity especially toward S. aureus. Compounds IV greater than XV greater than XVI were especially active against E. coli. Compounds XV greater than IV were especially inhibitory toward S. typhi and most of the prepared compounds inhibited considerably Ps. aeruginosa and K1. pneumoniae.

Anti-Bacterial Agents↗
PubMed1999

An interprovincial external quality assessment of the ability of Canadian laboratories to detect the vancomycin and penicillin resistance of Enterococcus faecium D366.

OBJECTIVE: To evaluate the ability of Canadian laboratories to identify enterococci and detect low-level resistance to penicillin, ampicillin and vancomycin in five provinces and two territories by two external quality assessment schemes. METHODS: Enterococcus faecium, strain D366, with minimum inhibitory concentrations for vancomycin and penicillin of 32 and 16 mg/L respectively, was distributed during a routine proficiency survey. Laboratories were required to culture and identify the isolate and to test antimicrobial susceptibility. Participants were assessed against consensus reference values. RESULTS: Three hundred and sixty-four hospital, commercial and public-health laboratories participated, using their established procedures for patient samples. The isolate was identified to the species level by 222 (61%) laboratories and to the genus level by a further 98 participants. Forty-four failed to meet the expected standard. Vancomycin resistance was detected by 94%. Those reporting a falsely susceptible result used disk diffusion testing. Penicillin resistance was noted by 250 of 258 laboratories reporting on this agent. An incorrect ampicillin-susceptible finding was reported by 62 of 147 laboratories using automated microdilution or agar dilution methods. CONCLUSIONS: Most laboratories identified the isolate to an appropriate level. Detection of low-level vancomycin and penicillin resistance was achieved by the majority. Ampicillin resistance was less readily detected.

Journal Article↗
PubMed2005

Frequency of isolation and antimicrobial susceptibility of bacteria isolated from bloodstream infections at Children's Medical Center, Tehran, Iran, 1996-2000.

Antimicrobial susceptibility patterns of major bloodstream pathogens from Iran provide essential information regarding the selection of antibiotic therapy for patients with bloodstream infections (BSIs) living in Iran. Unfortunately, data regarding the isolation frequency and antimicrobial susceptibility patterns of endemic BSI pathogens are scarce in Iran. To shed some light on the susceptibility patterns of BSI pathogens endemic to Tehran, Iran, we investigated the antimicrobial susceptibility patterns of 2248 bloodstream isolates from patients in Children's Medical Center (CMC) Hospital in Tehran between January 1996 and December 2000. Microbiology reports of 24600 blood specimens collected from inpatients in CMC Hospital were retrospectively reviewed. Specimen culture, bacterial identification and disk diffusion susceptibility testing were performed according to National Committee for Clinical Laboratory Standards guidelines. Overall, Gram-positive bacteria comprised 72% (1627/2248) of recovered isolates and Gram-negative bacteria comprised 28% (621/2248). Coagulase-negative staphylococci (CoNS) comprised 48.4% of all isolates, followed by Staphylococcus aureus (16.7%) and Klebsiella spp. (8.5%). Among the 621 Gram-negative organisms, Klebsiella spp. (31%) were the most frequently isolated, followed by Escherichia coli (21%) and Pseudomonas aeruginosa (17%). The rates of oxacillin resistance for S. aureus and CoNS isolates were similar (60% versus 61%); however, the rate of S. aureus vancomycin resistance was almost twice that of CoNS resistance (21% versus 11%). Over 55% of S. pneumoniae were resistant to penicillin and co-trimoxazole. Although all isolates of enterococci were susceptible to vancomycin, only 21% were susceptible to gentamicin. Among Gram-negative isolates, amikacin was shown to be very effective, with susceptibility rates of 84%. The susceptibility of Klebsiella spp. to ampicillin and co-trimoxazole was 1% and 39%, respectively. The susceptibility of Klebsiella spp., E. coli and Enterobacter spp. to ceftriaxone was 47%, 86% and 67%, respectively. There were notable differences in the order of the five most common organisms isolated from blood cultures, which can help set priorities for focused control efforts. Our findings highlight the importance of a nationwide surveillance programme to monitor the trends in isolation frequency of bacteria and their antimicrobial resistance patterns throughout Iran.

Bacteremia↗
PubMed1984

Endocarditis due to methicillin-resistant Staphylococcus aureus in rabbits: expression of resistance to beta-lactam antibiotics in vivo and in vitro.

Whether a strain of methicillin-resistant Staphylococcus aureus susceptible to cephalothin by the disk-diffusion method was also susceptible to cephalothin in vivo was evaluated in the rabbit model of endocarditis. Rabbits with aortic-valve endocarditis due to methicillin-resistant S. aureus that were treated for four days with cephalothin had the same numbers of organisms in vegetations as did untreated rabbits. Treatment with cephalothin caused emergence of a highly resistant subpopulation in aortic-valve vegetations. Organisms highly resistant to cephalothin were also highly resistant to nafcillin. Thus broth-dilution and disk-diffusion tests may not predict therapeutic failure for cephalothin against strains of methicillin-resistant S. aureus. Because of cross-resistances among beta-lactam drugs, these strains should be considered uniformly resistant to this general class of antimicrobial agents, regardless of results from these tests.

Animals↗
PubMed2003

Effectiveness of selected materials against Enterococcus faecalis: part 3. The antibacterial effect of calcium hydroxide and chlorhexidine on Enterococcus faecalis.

It has been found that Enterococcus faecalis is most commonly isolated in failed endodontic treatment. Irrigation with chlorhexidine gluconate has been suggested based on its antimicrobial effect and substantivity. Calcium hydroxide also is an effective antimicrobial agent because of its high alkalinity. The purpose of this study was to test the individual and combined effect of calcium hydroxide and chlorhexidine against E. faecalis. The agar-diffusion test was performed on Mueller-Hinton plates. Paper disks were impregnated with: (a) CaOH powder with sterile water; (b) Pulpdent; (c) 0.12% Peridex; (d) CaOH powder with Peridex; and (e) Pulpdent with Peridex. Ampicillin served as a control. The plates were incubated at 37 degrees C for 72 h. Peridex showed significantly larger zones of inhibition compared with CaOH. No statistically significant difference was found between Peridex and the combination of CaOH and Peridex.

Analysis of Variance↗
PubMed1982

Antimicrobial susceptibility of Moraxella bovis determined by agar disk diffusion and broth microdilution.

The antimicrobial susceptibility of 84 isolates of Moraxella bovis was evaluated by the standard agar disk diffusion and broth microdilution procedures. All isolates were resistant to cloxacillin by disk diffusion, with 97% of isolates having a minimal inhibitory concentration of greater than or equal to 2 micrograms/ml. Of the hemolytic isolates, 68% were resistant to streptomycin. A high frequency of susceptibility was recorded for all other antimicrobial agents tested. Quantitative data supported the use of sulfonamides, but not tylosin, for parenteral infectious bovine keratoconjunctivitis therapy.

Anti-Bacterial Agents↗
PubMed1998

Antimicrobial activity of quinupristin-dalfopristin (RP 59500, Synercid) tested against over 28,000 recent clinical isolates from 200 medical centers in the United States and Canada.

A total of 200 medical center laboratories in the USA and Canada contributed results of testing quinupristin-dalfopristin, a streptogramin combination (formerly RP 59500 or Synercid), against 28,029 Gram-positive cocci. Standardized tests [disk diffusion, broth microdilution, Etest (AB BIODISK, Solna, Sweden)] were utilized and validated by concurrent quality control tests. Remarkable agreement was obtained between test method results for characterizing the collection by the important emerging resistances: 1) oxacillin resistance among Staphylococcus aureus (41.0 to 43.7%); 2) vancomycin resistance among Enterococcus faecium (50.0 to 52.0%); and 3) the penicillin nonsusceptible rate for pneumococci (31.1% overall, with 10.6% at MICs of > or = 2 micrograms/mL). The quinupristin-dalfopristin MIC90 for oxacillin-susceptible and -resistant S. aureus was 0.5 microgram/mL and 1 microgram/mL, respectively. The quinupristin-dalfopristin MIC90 for vancomycin-resistant E. faecium was 1 microgram/mL, and only 0.2% of isolates were resistant. Other Enterococcus species were generally not susceptible to the streptogramin combination but were usually inhibited by ampicillin (86 to 97% susceptible; MIC50, 1.0 microgram/mL) or vancomycin (86 to 95%; MIC50, 1.0 microgram/mL). Among all tested enterococci, the rate of vancomycin resistance was 16.2%. The quinupristin-dalfopristin MIC90 (0.75 microgram/mL) for 4,626 tested Streptococcus pneumoniae strains was not influenced by the penicillin or macrolide susceptibility patterns. When five regions in the USA and Canada were analyzed for significant streptogramin and other antimicrobial spectrum differences, only the Farwest region had lower numbers of streptogramin-susceptible E. faecium. Canadian strains were generally more susceptible to all drugs except chloramphenicol and doxycycline when tested against E. faecalis (73% and 89% susceptible, respectively). The U.S. Southeast region had S. pneumoniae strains less susceptible to macrolides (73%) but had more susceptibility among E. faecium isolates tested against vancomycin and ampicillin. The Northeast region of the USA had the greatest rate of vancomycin resistance among enterococci. Strains retested by the monitor because of quinupristin-dalfopristin resistance (MICs, > or = 4 micrograms/mL) were generally not confirmed (2.2% validation), and only 0.2% of E. faecium isolates were identified as truly resistant. The most common errors were: 1) species misidentification (28.0%); 2) incorrect susceptibility results (65.6%); and 3) mixed cultures (4.3%) tested by participants. Overall, quinupristin-dalfopristin was consistently active (> or = 90% susceptible) against major Gram-positive pathogens in North America, regardless of resistance patterns to other drug classes and geographic location of their isolation.

Academic Medical Centers↗
PubMed2006

Antimicrobial susceptibility of enterococci strains isolated from slaughter animals on the data of Hungarian resistance monitoring system from 2001 to 2004.

Isolates of Enterococcus spp. were collected from January 2001 to December 2004 from caecal samples of slaughtered poultry, swine and cattle in Hungary. The isolates were identified by their growth and biochemical properties and with PCR. The antibiotic susceptibility of a total number of 1272 isolates was tested with disk diffusion test to ampicillin, gentamicin, streptomycin, tetracycline, erythromycin and vancomycin. It was established that although ampicillin and amoxicillin are often used in veterinary practice its resistance rate was relatively low. In the case of tetracyclines and macrolides, a high incidence of resistance was found. Susceptibility of strains to tetracyclines and/or macrolides reduced in both 2003 and 2004 in all animal species, which may be due to the more frequent usage of these drugs in the veterinary practice following the ban of growth promoters. The annual data of vancomycin resistance point to an association between the recovery of vancomycin-resistant enterococci (VRE) isolates and the use of avoparcin. This study indicates that reducing antimicrobial resistance in food animals could be possible with lower usage of antibiotics, although variations can occur with different strains.

Abattoirs↗
PubMed2001

Characterization of clinical isolates of Klebsiella pneumoniae from 19 laboratories using the National Committee for Clinical Laboratory Standards extended-spectrum beta-lactamase detection methods.

Extended-spectrum beta-lactamases (ESBLs) are enzymes found in gram-negative bacilli that mediate resistance to extended-spectrum cephalosporins and aztreonam. In 1999, the National Committee for Clinical Laboratory Standards (NCCLS) published methods for screening and confirming the presence of ESBLs in Klebsiella pneumoniae, Klebsiella oxytoca, and Escherichia coli. To evaluate the confirmation protocol, we tested 139 isolates of K. pneumoniae that were sent to Project ICARE (Intensive Care Antimicrobial Resistance Epidemiology) from 19 hospitals in 11 U.S. states. Each isolate met the NCCLS screening criteria for potential ESBL producers (ceftazidime [CAZ] or cefotaxime [CTX] MICs were > or =2 microg/ml for all isolates). Initially, 117 (84%) isolates demonstrated a clavulanic acid (CA) effect by disk diffusion (i.e., an increase in CAZ or CTX zone diameters of > or =5 mm in the presence of CA), and 114 (82%) demonstrated a CA effect by broth microdilution (reduction of CAZ or CTX MICs by > or =3 dilutions). For five isolates, a CA effect could not be determined initially by broth microdilution because of off-scale CAZ results. However, a CA effect was observed in two of these isolates by testing cefepime and cefepime plus CA. The cefoxitin MICs for 23 isolates that failed to show a CA effect by broth microdilution were > or =32 microg/ml, suggesting either the presence of an AmpC-type beta-lactamase or porin changes that could mask a CA effect. By isoelectric focusing (IEF), 7 of the 23 isolates contained a beta-lactamase with a pI of > or =8.3 suggestive of an AmpC-type beta-lactamase; 6 of the 7 isolates were shown by PCR to contain both ampC-type and bla(OXA) genes. The IEF profiles of the remaining 16 isolates showed a variety of beta-lactamase bands, all of which had pIs of < or =7.5. All 16 isolates were negative by PCR with multiple primer sets for ampC-type, bla(OXA), and bla(CTX-M) genes. In summary, 83.5% of the K. pneumoniae isolates that were identified initially as presumptive ESBL producers were positive for a CA effect, while 5.0% contained beta-lactamases that likely masked the CA effect. The remaining 11.5% of the isolates studied contained beta-lactamases that did not demonstrate a CA effect. An algorithm based on phenotypic analyses is suggested for evaluation of such isolates.

Algorithms↗