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PubMed2005

Enterococci spp. isolated from Cuba: species frequency of occurrence and antimicrobial susceptibility profile.

This study investigated the species distribution and antimicrobial resistance among 99 enterococci isolated from hospitalized patients in 12 hospitals in Cuba from October 2000 to September 2001. Species identification was performed by WIDER Automatic System (Francisco Soria Melguizo, Madrid, Spain), and the susceptibility testing was performed by disk diffusion, agar dilution, and E-test methods. Enterococcus faecalis was the most prevalent (85%) species, followed by E. faecium (10%), E. gallinarum (2%), E. casseliflavus (2%), and E. durans-hirae (1%). A higher percentage of resistance to ampicillin (50%), fosfomycin (40%), ciprofloxacin (30%), norfloxacin (20%), and tetracycline (90%) was detected in E. faecium isolates, whereas E. faecalis strains showed higher rates of resistance to erythromycin (52.4%), chloramphenicol (34.5%), rifampicin (62.5%), moxifloxacin (3%), and nitrofurantoin (2.4%). Resistance to glycopeptide was detected in E. faecalis (1.2%) and E. faecium (10%). Thirty-one E. faecalis (37%) and 3 E. faecium (30%) showed a high-level resistance to gentamicin. The results of this work will be very helpful to guide empirical antimicrobial therapy and the implementation of infection control measures in Cuban hospitals.

Drug Resistance, Bacterial↗
PubMed1998

Acquisition, carriage, and transmission of pneumococci with decreased antibiotic susceptibility in young children attending a day care facility in southern Israel.

The prevalence and transmission of antimicrobial drug-resistant pneumococci was studied in 48 children attending a day care facility in southern Israel. Nasopharyngeal cultures were obtained every 2 weeks for 10 months, and antibiotic susceptibility of isolates was determined by disk diffusion and E-test. Relatedness of isolates was investigated by capsular typing, ribotyping, and arbitrarily primed polymerase chain reaction. Pneumococci were recovered during 362 (63%) of 573 fortnights, and 219 (60%) of these isolates showed decreased susceptibility to at least one drug; 154 (43%) were intermediately susceptible to penicillin and 51 (14%) were multiresistant. Combining the different typing methods showed that a limited number of clones circulated in the facility. Clones exhibiting decreased antibiotic susceptibility (especially 23F, intermediately susceptible to penicillin and resistant to trimethoprim-sulfamethoxazole, and multiresistant 6B) were more frequently isolated and persisted longer than did fully susceptible clones. By multivariate analysis, carriage of organisms with decreased antibiotic susceptibility was associated with young age, female sex, winter season, and exposure to antimicrobial drugs during the previous month.

Age Factors↗
PubMed2002

Comparative evaluation of two commercial chromogenic media for detection and presumptive identification of urinary tract pathogens.

The performance of two commercial chromogenic media for the isolation and presumptive identification of urinary tract pathogens, the CPS ID2 (bioMérieux, France) and the CHROMagar Orientation (BBL Becton Dickinson, USA), was evaluated and compared with that of cystine-lactose-electrolyte-deficient agar and tryptic soy agar with 5% sheep blood. The detection, determination of bacterial counts, and presumptive identification of bacteria causing urinary tract infections were evaluated in 3,000 urine specimens. The two chromogenic media showed excellent correlation with the standard media for the detection and the bacterial count of urinary pathogens. The Escherichia coli strains produced the expected colour on the CHROMagar Orientation and the CPS ID2 media in 99% and 90% of the cases, respectively. The Klebsiella-Enterobacter-Citrobacter and the Proteus-Morganella-Providencia groups were easily identified on both chromogenic media, but further biochemical tests were needed to differentiate them to a species level. Both media enabled the differentiation, with varying degrees of difficulty, of Pseudomonas spp. strains from members of the family Enterobacteriaceae. All isolates of Enterococcus spp. were correctly identified and were easily distinguished from the Streptococcus agalactiae isolates. Staphylococcus saprophyticus isolates were easy to identify only on the CHROMagar Orientation medium. No substantial difference was observed when comparing the results of the susceptibility tests, which were performed according to the standardized disk diffusion method as described by the National Committee for Clinical Laboratory Standards, for colonies recovered from the blood agar versus those recovered from the chromogenic media. In conclusion, the CPS ID2 and CHROMagar Orientation media enabled excellent detection, count determination, and presumptive identification of urinary pathogens, both in pure and mixed cultures, and reliable and accurate antimicrobial susceptibility testing directly from primary isolates. Moreover, these media allowed a remarkable reduction in the workload and a significant savings of time. On the basis of their performance, these media can replace the standard primary plating media used in the routine diagnosis of urinary tract infections.

Candida↗
PubMedDate not supplied

Bulk acoustic wave bacterial growth sensor applied to analysis of antimicrobial properties of tea.

A bulk acoustic wave (BAW) bacterial growth sensor has been proposed for study of inhibitory effects of tea by continuous monitoring of disturbances in Proteus growth in the aqueous extracts of various teas, e.g. green tea, Fuzhuan brick tea, Oolong tea, Kudin tea, and black tea. The kinetic parameters, e.g. asymptote (A), maximum specific growth rate (microm), lag time (lambda), and generation time (g), accurately estimated by using the growth response model, have been first used to characterize antimicrobial properties of tea. All of the parameters were changed via the inhibitory effects by tea. Green tea gives the weakest inhibitory action while others show stronger inhibitory actions. These inhibitory effects have also been examined by using the pour plate count technique. Both of the results show that, in addition to the antimicrobial properties of tea polyphenols and catechins, etc., the inhibitory effects may be attributed to the metabolites produced during the fermentation processing of these teas except green tea. The conventional disk diffusion test has been used to determine the minimum inhibitory concentration (MIC) against P. rettgeri. The MICs of green tea, Fuzhuan brick tea, Oolong tea, and black tea were found to be 1113, 818.0, 681.2, and 510.4 microg/mL, respectively. The BAW bacterial growth sensor has shown to have advantages over other techniques, including the disk diffusion test, photometry, and the impedance method.

Acoustics↗
PubMed1978

Modified agar dilution method for rapid antibiotic susceptibility testing of anaerobic bacteria.

A simplified method has been developed for agar dilution antimicrobial susceptibility testing of anaerobic bacteria, designed to economize on time and money when only a few isolates need to be tested. The procedure is based on the principle of using filter paper disks as carriers of the antibiotic and 35- by 10-mm petri dishes which, when inoculated with the Steers replicator, can test up to four organisms per plate. The procedure was run in parallel with conventional agar dilution techniques and showed 95% agreement to within one dilution for all minimal inhibitory concentrations recorded on fresh anaerobic isolates from clinical specimens. The technique was further simplified by using commercially available antibiotic-containing disks, thereby alleviating the tedious and time-consuming procedure of preparing the disks. The data indicated that 48- to 72-h diffusion periods were sufficient to achieve a uniform concentration of the antibiotic in the petri plate and that the antibiotics were stable at room temperature for that period of time. In terms of applicability and relevance to the needs of the clinical microbiology laboratory, the modified agar dilution method for rapid antimicrobial susceptibility testing of individual anaerobic isolates was found to be superior to the broth dilution method since it was easier to read and required considerably less set up time.

Agar↗
PubMed2000

Susceptibility of 1100 Streptococcus pneumoniae strains isolated in 1997 from seven Latin American and Caribbean countries. Laser Study Group.

The antimicrobial susceptibility to beta-lactam and non-beta-lactam agents of 1100 isolates of Streptococcus pneumoniae recovered in 1997 from 16 centres in Argentina, Brazil, Chile, Mexico, Panama, Venezuela and West Indies was studied using E-test and disk diffusion methods. A total of 23.6% of isolates had raised penicillin MICs (16.7% intermediate and 6.9% resistant). The susceptibility of the other agents tested, from most active to least active, were, amoxycillin/clavulanate (99.5% susceptible); chloramphenicol (93.2%); cefotaxime (91.7%); erythromycin (87.1%); tetracycline (74.6%); trimethoprim/sulphamethoxazole (TMP-SMZ) (55.4%); and cefaclor (52.8%). The highest proportion of strains resistant to penicillin, chloramphenicol, erythromycin, tetracycline and TMP-SMZ was found in strains from Mexico while resistance to these agents was lowest in strains from the West Indies. Prevalence of penicillin resistance (including intermediate and resistant isolates) in each of the countries, from highest to lowest was, Mexico (40.8%); Chile (31.3%); Panama (23.0%); Venezuela (21.9%); Argentina (19.1%); Brazil (12.9%); and West Indies (7.1%). Based on current levels of antimicrobial resistance of S. pneumoniae in Latin American and Caribbean countries, continued surveillance efforts are necessary in order to guide clinical empiric treatment and provide for judicious use of antimicrobial agents.

Anti-Bacterial Agents↗
PubMed1979

Disk diffusion testing of susceptibility of Mycobacterium fortuitum and Mycobacterium chelonei to antibacterial agents.

Although recent studies have suggested that some antibacterial agents have good activity against the rapidly growing mycobacteria Mycobacterium fortuitum and Mycobacterium chelonei, an easily applicable method for susceptibility testing of clinical isolates is not yet available. We evaluated a disk diffusion method with Mueller-Hinton agar and 48-h readings with 59 strains of M. fortuitum and 11 strains of M. chelonei and compared the results to agar dilution susceptibilities for nine antimicrobial agents. All isolates were susceptible to 16 micrograms of amikacin or kanamycin per ml with minimum zone diameters of 14 and 18 mm, respectively. Amikacin inhibited 100% of isolates of M. fortuitum at 2 micrograms/ml, whereas 10 of 11 (91%) of M. chelonei strains had minimum inhibitory concentrations of 4.0 micrograms/ml or greater. Doxycycline and minocycline had almost identical activities, inhibiting 44% of strains at 4.0 micrograms/ml, and both allowed easy differentiation between susceptible and resistant strains by disk diffusion. Although most isolates of M. chelonei grew better on 7H10 agar, this media gave two- to eight-fold higher minimum inhibitory concentrations than were obtained with Mueller-Hinton agar. Disk diffusion susceptibility testing appears to be a simple and reliable means of predicting susceptibility results for M. fortuitum and most isolates of M. chelonei by the agar dilution method.

Aminoglycosides↗
PubMed1985

[In vitro effect of ceftriaxone on hospital bacteria. Line of regression and critical values].

Antimicrobial activity of ceftriaxone, a new third generation cephalosporin, against hospital isolates was investigated. 312 strains belonging to the most commonly recovered species were studied using the following methods: agar diffusion (disk antibiotic testing), agar dilution (determination of MIC) and dilution in a liquid medium with subculture to agar plates (determination of MBC). Except for a few Citrobacter strains and rare Serratia strains, all Enterobacteriaceae tested proved highly susceptible, with MICs less than or equal to 1 mg/l and mode MICs ranging from 0.003 mg/l (Proteus) to 0.25 mg/l (Enterobacter). MICs ranged from 16 to 32 mg/l for Acinetobacter (mode MICs: 16 mg/l) and 16 to greater than or equal to 128 for Pseudomonas (mode MIC greater than or equal to 128 mg/l). Methicillin-susceptible staphylococci were moderately susceptible to ceftriaxone (MIC: 2 to 8 mg/l) whereas methicillin-resistant staphylococci and enterococci were resistant (MIC greater than or equal to 64 mg/l). Bactericidal activity was excellent: MBC/MIC less than or equal to 2 (except for a few Serratia strains). A correlation curve was established. Given the high serum concentrations of ceftriaxone (achieved with the usual maximal dosage) and its unusually extended half-life (7 to 8 h), the following cutoff concentrations can be proposed: C less than or equal to 4 mg/l, corresponding to greater than or equal to 20 mm: susceptible bacteria C greater than 32 mg/l, corresponding to less than 15 mm: resistant bacteria.

Acinetobacter↗
PubMed1994

Multiple antibiotic resistance in Klebsiella spp. and other Enterobacteriaceae isolated in Singapore.

A common pattern of multiple antibiotic resistance has been noted in bacteria isolated from Singaporean patients. The resistance pattern includes: ampicillin, cefuroxime, ceftazidime and other third generation cephalosporins, aztreonam, gentamicin and other aminoglycosides. The bacterial species implicated are Klebsiellas and other members of the Enterobacteriaceae. Preliminary laboratory investigation with a disk-diffusion augmentation test suggests the presence of extended-spectrum beta-lactamases. A retrospective study of laboratory blood culture records shows a rising incidence of resistance in Klebsiella spp. since 1985. Antimicrobial susceptibility results suggest a high degree of co-transfer of aminoglycoside resistance. The high frequency of this type of multiple antibiotic resistance should result in greater caution in the selection of presumptive antibiotic therapy for septicaemia, in order to avoid treatment failure and further selection of resistant strains.

Anti-Bacterial Agents↗
PubMed1997

Study to determine the ability of clinical laboratories to detect antimicrobial-resistant Enterococcus spp. in Buenos Aires, Argentina.

Few reports of vancomycin-resistant enterococci have appeared outside the USA. Therefore, we evaluated the ability of five laboratories in Buenos Aires, Argentina, to perform susceptibility testing using the disk diffusion method. Laboratories had difficulty identifying the low- and intermediate-level vancomycin-resistant phenotypes. This suggests that the disk diffusion method used by laboratories abroad may fail to detect some vancomycin-resistant enterococci.

Anti-Bacterial Agents↗
PubMed2006

Production of mutagenic metabolites by Metarhizium anisopliae.

NG-391 (1) and NG-393 (2), previously reported from undescribed Fusarium species as nerve-cell growth stimulants, were identified from fermentation extracts of the entomopathogenic fungus Metarhizium anisopliae. These compounds are 7-desmethyl analogues of fusarin C and (8Z)-fusarin C, mutagenic toxins from Fusarium species that contaminate corn. A mutant strain of M. anisopliae (KOB1-3) overproduces 1 and 2 by ca. 10-fold relative to the wild-type strain, ARSEF 2575, from which it was derived. Overproduction of these compounds in KOB1-3 imparts a yellow pigmentation to the culture medium of the fungus. These compounds were inactive at 100 mug/disk in antimicrobial disk diffusion assays. Compound 1 was inactive at 100 ppm in a mosquitocidal assay. However, like their fusarin analogues, 1 and 2 exhibited potent S9-dependent mutagenic activity in the Salmonella mutagenicity test. Discovery of these highly mutagenic mycotoxins in M. anisopliae suggests that screening for production of NG-391 and NG-393 in strains that are used as biocontrol agents would be a prudent course of action. The impact of these findings on the use of M. anisopliae as a biocontrol agent is currently unknown and requires further investigation.

Ascomycota↗
PubMedDate not supplied

[Methicillin resistance detection in Staphylococcus aureus: comparison between conventional methods and MRSA-Screen latex agglutination technique].

Methicillin-resistant Staphylococcus aureus (MRSA) is a significant pathogen that has emerged over the last four decades, causing both nosocomial and community-acquired infections. Rapid and accurate detection of methicillin resistance in S. aureus is important for the use of appropriate antimicrobial therapy and for the control of nosocomial spread of MRSA strains. We evaluated the efficiency of conventional methods for detection of methicillin resistance such as the disk diffusion, agar dilution, oxacillin agar screen test, and the latex agglutination test MRSA-Screen latex, in 100 isolates of S. aureus, 79 mecA positive and 21 mecA negative. The MRSA-Screen latex (Denka Seiken, Niigata, Japón), is a latex agglutination method that detects the presence of PLP-2a, product of mecA gene in S. aureus. The PCR of the mecA gene was used as the "gold standard" for the evaluation of the different methods tested. The percentages of sensitivity and specificity were as follows: disk difusión 97 and 100%, agar dilution 97 and 95%, oxacillin agar screen test 100 and 100%, and MRSA-Screen latex, 100 and 100 %. All methods presented high sensitivity and specificity, but MRSA-Screen latex had the advantage of giving a reliable result, equivalent to PCR, in only 15 minutes.

Bacterial Proteins↗
PubMed1994

Antimicrobial susceptibility testing and blood cultures.

Susceptibility testing of microorganisms isolated from blood cultures should follow the guidelines of the NCCLS in the selection of antimicrobial agents and the method for testing. Standardized testing can be performed on isolated colonies from pure subcultures of the blood/broth mixture. Direct susceptibility testing can provide results up to 24 hours sooner, but the techniques for testing have not been standardized. The disk diffusion and agar dilution techniques do not utilize automated testing techniques and seem to provide reliable results. Limited studies of direct susceptibility testing using automated procedures have been published, but the results are not conclusive. The number of discrepancies with direct automated procedures in comparison with standardized techniques is low, and most investigators agree that direct testing is appropriate given the rapidity with which the results are available. New resistance patterns for microorganisms are appearing regularly, and the technology for automated procedures is changing rapidly. New clinical evaluations of direct susceptibility testing with larger numbers of microorganisms that include some of the recently described resistant microorganisms would help to clarify the accuracy and reliability of current procedures. Standardized direct susceptibility testing guidelines should be established so that reliability and accuracy can be improved. There is general consensus that repeat testing by standardized techniques is advisable, although the decision as to whether to repeat the test using a standardized method rests with the individual laboratory director based on his or her expertise and experience with the procedures. Each laboratory director should compare the advantages and limitations of direct antimicrobial susceptibility testing with the methodology currently in use and determine the need for repeat testing by standardized techniques.

Autoanalysis↗
PubMed2006

Performance accuracy of antibacterial and antifungal susceptibility test methods: report from the College of American Pathologists Microbiology Surveys Program (2001-2003).

CONTEXT: The College of American Pathologists Microbiology Surveys Program provides external proficiency samples that monitor the performance of nearly 3000 laboratories that perform and report antimicrobial susceptibility tests. OBJECTIVE: To summarize results obtained with bacterial and yeast challenge samples (2001 through 2003). DESIGN: One organism every 4 months was tested by surveys participants against antibacterials/antifungals by routinely used methods. Reports were graded by interpretive category (susceptible, intermediate, resistant) based on an 80% consensus of referees/participants. RESULTS: The most common antibacterial test methods/systems were Vitek (38%-43%), MicroScan (39%-43%), and the disk diffusion test (14%-15%), although Etest was most used for fastidious species. YeastOne was the dominant antifungal test (50%-55%). Antifungal results demonstrated continuous, improved accuracy (83%-88%), highest for YeastOne (96%) and broth microdilution (95%) methods. Antibacterial test accuracy was consistently greater than 97% against gram-positive organism challenges and greater than 98% against gram-negative challenges. For gram-negative strains with well-characterized resistance mechanisms, the accuracy by method was disk diffusion greater than broth microdilution greater than automated systems. Major problems identified were (1) Haemophilus influenzae control ranges require re-evaluation, (2) overuse of beta-lactamase tests, (3) errors among Enterococcus faecium against penicillins (Vitek 2, MicroScan), (4) false-susceptible results with trimethoprim/sulfamethoxazole against coagulase-negative staphylococci (MicroScan), (5) macrolide false-susceptibility for beta-hemolytic streptococcus (MicroScan), (6) flawed reporting for antimicrobials not active at the infection site, (7) use of outdated interpretive criteria, and (8) failure to follow Clinical and Laboratory Standards Institute testing/reporting recommendations. CONCLUSIONS: Susceptibility tests were generally performing satisfactorily as measured by the surveys, but serious errors were identified with some drug/organism combinations that may require action by the Clinical and Laboratory Standards Institute and/or the Food and Drug Administration.

Anti-Bacterial Agents↗
PubMed1999

Escherichia coli ATCC 35218 as a quality control isolate for susceptibility testing of Haemophilus influenzae with haemophilus test medium.

Current National Committee for Clinical Laboratory Standards (NCCLS) susceptibility guidelines for quality control testing with Haemophilus influenzae do not include a beta-lactamase-producing strain that could detect the deterioration of the beta-lactamase inhibitor components of amoxicillin-clavulanic acid, ampicillin-sulbactam, and piperacillin-tazobactam. The objective of the study was to determine if comparable quality control results for Escherichia coli ATCC 35218, a beta-lactamase-producing strain, would be produced for the three beta-lactam-beta-lactamase inhibitor agents with Haemophilus test medium and Mueller-Hinton medium. The criteria used in this study to determine if Haemophilus test medium was acceptable for quality control testing of E. coli ATCC 35218 was that 100% of the results obtained with an antimicrobial agent-methodology combination needed to be within the acceptable NCCLS ranges established with Mueller-Hinton medium. The MIC testing results obtained by the broth microdilution and E-test methods with amoxicillin-clavulanic acid and piperacillin-tazobactam were all within the NCCLS ranges; however, the results obtained with ampicillin-sulbactam by both methods were not within the NCCLS ranges. Acceptable results were obtained by the disk diffusion methodology with ampicillin-sulbactam and piperacillin-tazobactam but not with amoxicillin-clavulanic acid. When performing susceptibility testing with H. influenzae with the beta-lactam-beta-lactamase inhibitors, in addition to quality control testing with H. influenzae ATCC 49247, testing of E. coli ATCC 35218 on Haemophilus test medium is an effective way to monitor the beta-lactamase inhibitors in some antimicrobial agent-methodology combinations.

Culture Media↗
PubMed2002

In vitro activities of antimicrobial combinations against clinical isolates of Stenotrophomonas maltophilia.

BACKGROUND AND PURPOSE: Stenotrophomonas maltophilia, a major pathogen causing nosocomial infection, is inherently resistant to multiple antimicrobial agents. Evaluation of the effectiveness of recommended therapeutic options for S. maltophilia infections is crucial, particularly in areas with high antimicrobial resistance in this nosocomial pathogen. METHODS: The in vitro activities of ceftazidime (CAZ), ticarcillin-clavulanate (TIM), amikacin (AN), ciprofloxacin (CIP), and trimethoprim-sulfamethoxazole (TMP-SMZ) against 102 clinical isolates of S. maltophilia collected from January 1998 to December 1999 at a university hospital were evaluated. The disk diffusion and agar dilution susceptibilities of individual agents against these isolates were determined concomitantly. Errors between results obtained by the two methods were identified based on the guidelines for Acinetobacter species provided by the National Committee for Clinical Laboratory Standards. Activities of three two-drug combinations (AN + CIP, CAZ + CIP, and TIM + TMP-SMZ) against 32 of these isolates were analyzed using the checkerboard synergy test. RESULTS: Among the agents tested, TMP-SMZ was the most active against S. maltophilia (83.3% susceptible), followed by CIP (63.7%), CAZ (39.2%), TIM (36.2%), and AN (20.5%). Errors (very major and major) between the results obtained by the disk diffusion and agar dilution methods occurred at a high frequency for AN (15% and 3%), CAZ (8% and 6%), and CIP (3% and 3%). Synergy or partial synergy of antimicrobial agent combinations was detected predominantly with CAZ + CIP (81.3%) and TIM + TMP-SMZ (84.4%) but not with AN + CIP (37.5%). No antagonism was detected with any drug combinations. CONCLUSION: The dilution method is preferable to the disk diffusion method for susceptibility testing of S. maltophilia isolates, particularly for testing with AN, CAZ, and TIM, which have considerable error rates between the results obtained by the two methods. The findings from the synergy test suggest that TIM + TMP-SMZ and CAZ + CIP combinations are the treatments of choice for infections caused by S. maltophilia.

Anti-Bacterial Agents↗
PubMed1989

Evaluation of the Cobas-Bact system for direct and rapid identification and antimicrobial susceptibility testing of Enterobacteriaceae from positive urine specimens.

A direct antimicrobial susceptibility test and a direct identification of Gram-stained urine specimens positive for Enterobacteriaceae using a new instrument (Cobas-Bact) were compared by means of the conventional Kirby-Bauer agar diffusion disk method and the spot indole test, an in-house set of identification tests or API 20E. Bacteria from 191 cases of monomicrobial bacteriuria due to members of the family Enterobacteriaceae were tested. Direct susceptibility testing was performed in 180 cases (94%), providing 1649 antibiotic-microorganism combinations. A complete agreement was reached in 82% and essential agreement in 92% of cases. Minor discrepancies were found in 163 (9.9%) major ones in 125 (7.6%) and very major ones in 10 (0.6%) of examinations. 72% of all minor and 71% of all major discrepancies were caused by two antibiotics: cephalothin and nitrofurantoin. Of the very major discrepancies, 50% were due to amoxicillin. Of 171 direct identifications obtained, 130 (76%) were "high-confidence" correct identifications (percentage of likelihood p greater than or equal to 80%), 25 (14.6%) "low-confidence" identifications (percentage of likelihood p less than 80%) and 16 (9.4%) misidentifications. On the whole, this direct and rapid Cobas-Bact identification and susceptibility testing procedure provided satisfying information within 5-6 h after collection of urine specimens positive for members of the Enterobacteriaceae family.

Anti-Bacterial Agents↗
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↗