Evaluation of the VITEK 2 system for the identification and susceptibility testing of three species of nonfermenting gram-negative rods frequently isolated from clinical samples

VITEK 2 is a new automatic system for the identification and susceptibility testing of the most clinically important bacteria. In the present study 198 clinical isolates, including Pseudomonas aeruginosa (n = 146), Acinetobacter baumannii (n = 25), and Stenotrophomonas maltophilia (n = 27) were evaluated. Reference susceptibility testing of cefepime, cefotaxime, ceftazidime, ciprofloxacin, gentamicin, imipenem, meropenem, piperacillin, tobramycin, levofloxacin (only for P. aeruginosa), co-trimoxazole (only for S. maltophilia), and ampicillin-sulbactam and tetracycline (only for A. baumannii) was performed by microdilution (NCCLS guidelines). The VITEK 2 system correctly identified 91.6, 100, and 76% of P. aeruginosa, S. maltophilia, and A. baumannii isolates, respectively, within 3 h. The respective percentages of essential agreement (to within 1 twofold dilution) for P. aeruginosa and A. baumannii were 89.0 and 88.0% (cefepime), 91.1 and 100% (cefotaxime), 95.2 and 96.0% (ceftazidime), 98.6 and 100% (ciprofloxacin), 88.4 and 100% (gentamicin), 87.0 and 92.0% (imipenem), 85.0 and 88.0% (meropenem), 84.2 and 96.0% (piperacillin), and 97.3 and 80% (tobramycin). The essential agreement for levofloxacin against P. aeruginosa was 86.3%. The percentages of essential agreement for ampicillin-sulbactam and tetracycline against A. baumannii were 88.0 and 100%, respectively. Very major errors for P. aeruginosa (resistant by the reference method, susceptible with the VITEK 2 system [resistant to susceptible]) were noted for cefepime (0.7%), cefotaxime (0.7%), gentamicin (0.7%), imipenem (1.4%), levofloxacin (2.7%), and piperacillin (2.7%) and, for one strain of A. baumannii, for imipenem. Major errors (susceptible to resistant) were noted only for P. aeruginosa and cefepime (2.0%), ceftazidime (0.7%), and piperacillin (3.4%). Minor errors ranged from 0.0% for piperacillin to 22.6% for cefotaxime against P. aeruginosa and from 0.0% for piperacillin and ciprofloxacin to 20.0% for cefepime against A. baumannii. The VITEK 2 system provided co-trimoxazole MICs only for S. maltophilia; no very major or major errors were obtained for co-trimoxazole against this species. It is concluded that the VITEK 2 system allows the rapid identification of S. maltophilia and most P. aeruginosa and A. baumannii isolates. The VITEK 2 system can perform reliable susceptibility testing of many of the antimicrobial agents used against P. aeruginosa and A. baumannii. It would be desirable if new versions of the VITEK 2 software were able to determine MICs and the corresponding clinical categories of agents active against S. maltophilia.     

Activity in vitro of twelve antibiotics against clinical isolates of extended-spectrum beta-lactamase producing Escherichia coli

Twelve beta-lactam and non-beta-lactam antibiotics were evaluated against 115 clinical isolates of extended-spectrum beta-lactamase-producing (ESBLs) Escherichia coli using a broth microdilution test in accordance with the CLSI guidelines. Susceptibility was 100% with imipenem, ertapenem and amikacin, 95.7% with piperacillin-tazobactam, 91.3% with cefoxitin, 87% with tobramycin, 81.7% with amoxicillin-clavulanate, 80% with cefepime, 67.8% with ceftazidime, 27.8% with ciprofloxacin, 27% with levofloxacin and 13% with ceftriaxone. Ertapenem was the antibiotic with the lowest minimum inhibitory concentrations (MICs) for all isolates. There were no clinically relevant differences in the activity of the antibiotics in the presence of CTX-M-9 or SHV enzymes.     

Accuracy of three automated systems (MicroScan WalkAway, VITEK, and VITEK 2) for susceptibility testing of Pseudomonas aeruginosa against five broad-spectrum beta-lactam agents

One hundred recent clinical Pseudomonas aeruginosa isolates were used to assess the quantitative (MIC) and qualitative (susceptibility category) accuracies of the MicroScan WalkAway, VITEK, and VITEK 2 automated susceptibility test systems when five-broad spectrum beta-lactams, aztreonam, cefepime, ceftazidime, imipenem, and piperacillin-tazobactam, were tested. Isolates were selected so that the MICs for the isolates overrepresented the MICs near the breakpoints to assess precisely the agreement between the results obtained with the automated systems and the results obtained by the reference tests. The categorical and MIC results from the automated systems were compared to the consensus result of three reference methods: broth microdilution, agar dilution, and disk diffusion. The consensus categorical testing (susceptibility and resistance) rates were 47 and 27%, respectively, for aztreonam; 59 and 14%, respectively, for cefepime; 44 and 43%, respectively, for ceftazidime; 71 and 19%, respectively, for imipenem; and 50 and 50%, respectively, for piperacillin-tazobactam. All systems tested exhibited a high, unacceptable level of very major (false-susceptible) errors for piperacillin-tazobactam (19 to 27%). Major (false-resistant) error rates were generally acceptable (0 to 3%), but minor error rates were elevated (8 to 32%) for cefepime (VITEK 2 and VITEK) and for aztreonam (all three systems), leading to consistent trends toward false resistance. Manufacturer reevaluation of these automated systems for the testing of selected beta-lactams with current clinical isolates of P. aeruginosa that exhibit contemporary resistance mechanisms would be prudent to minimize the potential for serious reporting errors.     

Effect of β-lactam antibiotics on the in vitro development of resistance in Pseudomonas aeruginosa

Objective   To investigate whether stepwise selection of resistance mutations may mirror the continued bacterial exposure to antibiotics that occurs in the clinical setting.
Methods   We examined the in vitro development of resistance to a number of commonly used antibiotics (cefepime, cefpirome, ceftazidime, cefotaxime, piperacillin and imipenem) in Pseudomonas aeruginosa , a significant nosocomial pathogen. Stepwise resistance was assessed by serial passage of colonies located nearest to the inhibition zone on antibiotic-containing gradient plates.
Results   The lowest frequencies of spontaneous resistance mutations were found with cefepime and imipenem; these drugs also resulted in the slowest appearance of resistance of spontaneous resistance mutations. In five wild-type P. aeruginosa strains, cefepime-selected isolates required a mean of 30 passages to reach resistance; resistance occurred more rapidly in strains selected with other cephalosporins. P. aeruginosa strains that produced β -lactamase or non-enzymatic resistance generally developed resistance more rapidly than wild-type strains. For most strains, resistance to all antibiotics except imipenem correlated with increased levels of β -lactamase activity. Cross-resistance of cephalosporin-selected resistant mutants to other cephalosporins was common. Cephalosporin-resistant strains retained susceptibility to imipenem and ciprofloxacin.
Conclusions   From our in vitro study, we can conclude that the rate of development of resistance of P. aeruginosa is lower with cefepime compared with other cephalosporines.     

2012年深圳市光明新区人民医院细菌耐药监测

目的了解2012年深圳市光明新区人民医院临床分离菌对常用抗菌药物的耐药性。方法采用Microscanauto4鉴定及药敏系统对临床常规细菌进行监测．按CLSl2009年版标准判断药敏结果．并用WHONET5．4软件统计分析。结果全年共分离细菌1818株,其中革兰阳性菌占35．6％,革兰阴性菌占58．O％。葡萄球菌中耐甲氧西林金黄色葡萄球菌（MRSA）占18．3％,凝固酶阴性葡萄球菌（MRCNS）占71．9％。肺炎链球菌中青霉素非敏感的肺炎链球菌（PNSSP）占20．7％。大肠埃希菌和肺炎克雷伯杆菌产ESBLs菌株分别占43．2％和22．4％。检出5株亚胺培南耐药的肠杆科细菌。铜绿假单胞菌和鲍曼不动杆菌对头孢他啶、哌拉西林、妥布霉素、阿米卡星、环丙沙星、亚胺培南的耐药率均低于10％。结论本院常见致病菌耐药性不是十分严重,尤其是院内感染的铜绿假单胞菌和鲍曼不动杆菌对常用抗菌药物耐药率较低。     

Comparative in vitro activity of cefepime (BMY 28142) against multiresistant nosocomial isolates ofPseudomonas aeruginosa

The in vitro activity of a new parenteral cephalosporin cefepime (BMY 28142) was compared with that of ceftazidime, cefotaxime, piperacillin, imipenem, gentamicin, amikacin and ciprofloxacin against 173 recent multiresistantPseudomonas aeruginosa isolates of nosocomial origin using an agar dilution technique with an inoculum of 10⁴ CFU per spot. The activity of cefepime was comparable to that of ceftazidime, superior to that of cefotaxime, piperacillin, gentamicin and amikacin, but inferior to that of imipenem and ciprofloxacin. Cross-resistance ofPseudomonas aeruginosa to ceftazidime and cefepime occurred in nearly 50% of the cefepime resistant strains and 61.5% of the ceftazidime resistant strains respectively.     

Antimicrobial susceptibility of bacteria causing urinary tract infections in Latin American hospitals: results from the SENTRY Antimicrobial Surveillance Program (1997)

Objectives: To evaluate the antimicrobial susceptibility patterns among 469 pathogens isolated as a significant cause of urinary tract infections in 10 Latin American medical centers.
Methods: Consecutively collected isolates were susceptibility tested by broth microdilution methods, and selected isolates were characterized by molecular typing methods.
Results: Escherichia coli and Klebsiella spp. isolates revealed high rates of resistance to broad-spectrum penicillins and to fluoroquinolones. Ceftazidime MICs of ≥2 mg/L, suggesting the production of extended-spectrum β-lactamases (ESBLs), were observed in 37.7% of K. pneumoniae and 8.3% of Escherichia coli isolates. Enterobacter spp. isolates were characterized by high resistance rates to ciprofloxacin (35%) and to ceftazidime (45%), but they generally remained susceptible to cefepime (95% susceptible). Pseudomonas aeruginosa and Acinetobacter spp. were highly resistant to ciprofloxacin and ceftazidime. Imipenem was active against 80% of P. aeruginosa and 93% of Acinetobacter spp. isolates.
Conclusions: Our results demonstrate a high level of resistance to various classes of antimicrobial agents among isolates causing nosocomial urinary tract infections in Latin American hospitals. Clonal dissemination of ESBL-producing K. pneumoniae strains was infrequent.     

Drug sensitivity patterns of bacterial isolates from septic post-operative wounds in a regional referral hospital in Uganda

Background: Wound infections have been a problem in the field of surgery for a long time. Advances in control of infections have not completely eradicated this problem because of development of drug resistance. Antimicrobial resistance can increase complications and costs associated with procedures and treatment. Objective: A study was carried out on drug sensitivity patterns of bacterial isolates from septic postoperative wounds in Jinja hospital, Uganda. This study was designed to determine the distribution of bacterial pathogens isolated from septic post-operative wounds and their antimicrobial susceptibility patterns. Method: Specimens of pus swabs were collected aseptically and analysed in the laboratory. Colony characteristics and Grams technique were used to differentiate the organisms. Biochemical tests were done to confirm the species of the organisms. Sensitivity testing was done on the isolates using the disk diffusion method. Results: Pathogenic bacteria were recovered from 58.5% of the specimens. The isolates were: S.aureus (45.1%), Coliforms (16.9%), Proteus mirabilis (11.3%), P.aeruginosa (9.9%), Klebsiella pneumoniae (7.0%) and Enterobacter spp (2.82%). Most of the organisms were sensitive to gentamicin, ciprofloxacin and ceftazidime. There was resistance to ampicillin, amoxycillin and chloramphenicol. Staphylococcus aureus was generally sensitive to gentamicin (87.5%), ciprofloxacin (68.7%) and methicillin (75%), but resistant to erythromycin (56.2%) and ampicillin (97%). Most of the gram-negative bacteria isolated (Coliforms, P.aeruginosa, E.coli, Proteus mirabilis, and Klebsiella pneumoniae) were sensitive to Ciprofloxacin, Gentamicin and Ceftazidime but resistant to Ampicillin, Amoxycillin and Chloramphenicol. Methicillin-resistant Staphylococcus aureus (MRSA) strains formed 25% of this species. Pseudomonas aeruginosa was sensitive to gentamicin (87.5%) and ceftazidime (85.7%) but showed resistance to ciprofloxacin (57.2%). Some organisms e.g. S.aureus, Pseudomonas aeruginosa and Proteus mirabilis exhibited multi-drug resistance to the antibiotics tested. Conclusion: Since a high proportion of samples had positive cultures, infection control is recommended as a strategy to minimise spread of resistant organisms. It is recommended that gentamicin, ciprofloxacin and ceftazidime be used in preference to ampicillin and amoxycillin for treatment of septic wounds. There is need to develop national surveillance of antibiotic- resistant organisms.     

ICU患者痰细菌分布特征及药敏分析

目的统计分析2009年1～11月佛山市中医院ICU痰标本细菌培养病原菌分布特征及药敏情况,为临床经验用药提供科学的参考。方法留取经镜检合格的痰标本,经分离培养出病原菌后,以法国梅里埃VITEK2全自动细菌鉴定分析仪鉴定,以K-B法检测药物敏感性,用MICROSOFT OFFICE Excel2003进行数据处理。结果共分离出288株菌,病原菌分布以铜绿假单胞菌最多占20%,其次是金黄色葡萄球菌、鲍曼不动杆菌、肺炎克雷伯菌和大肠埃希菌,分别是14%、13%、10%、7%。药敏结果显示,铜绿假单胞菌和鲍曼不动杆菌对头孢吡肟、头孢他啶、亚胺培南、阿米卡星等的敏感率均达75%以上;阿米卡星、亚胺培南和头孢西丁对肺炎克雷伯菌与大肠埃希菌的抗菌活性也较好;金黄色葡萄球菌对万古霉素、替考拉宁、呋喃妥因等的敏感率较高,均为75%以上,而对青霉素仅有2%的敏感率。结论痰培养病原菌以铜绿假单胞菌和金黄色葡萄球菌为主;对于革兰阴性杆菌,可选用第三代头孢菌素、氨基糖苷类抗生素,对革兰阳性球菌,可用万古霉素、替考拉宁、呋喃妥因。     

Imipenem resistance in nonfermenters causing nosocomial urinary tract infections

Nonfermenting gram-negative bacilli (nonfermenters) have emerged as important nosocomial pathogens causing opportunistic infections in immunocompromised hosts. These organisms show high level of resistance to b-lactam agents, fluoroquinolones and aminoglycosides. Imipenem is a carbapenem antibiotic, which can be very useful for treatment of infections caused by nonfermenters. Eighty-five nonfermenters causing nosocomial UTI were tested for MIC to imipenem by agar dilution method. Resistance to other antimicrobial agents was compared between imipenem sensitive (S) and resistance (R) groups. Overall 36.4% of nonfermenters were resistant to imipenem. Forty two percent of P. aeruginosa and 18.5% of Acinetobacter baumanii were imipenem resistant. Other nonfermenters showed variable resistance, resistance in Alcaligenes spp. being very high. More than 70% of the nonfermenters were resistant to ceftazidime, gentamicin and ciprofloxacin. Piperacillin and amikacin had the best in vitro susceptibility. No significant difference was found in the antibiotic susceptibility profile among imipenem sensitive (S) or resistant (R) strains.     

Multicentre study of the in vitro activity of cefepime, a broad-spectrum cephalosporin, compared to other broad-spectrum agents

The in vitro activity of cefepime was compared to that of a range of other broad-spectrum agents, using a gradient diffusion MIC method, against 995 recent clinical isolates of Enterobacteriaceae, Pseudomonas aeruginosa, other nonfermentative gram-negative bacilli, staphylococci (except oxacillin-resistant Staphylococcus aureus), streptococci, enterococci, and aerobic gram-positive bacilli. Cefepime had excellent activity against Enterobacteriaceae, including eight presumptive extended-spectrum beta-lactamase producers and 33 stably derepressed mutants of natural cephalosporinases. Activity against Pseudomonas aeruginosa was similar to ceftazidime and superior to cefpirome. Its activity against gram-positive cocci was also good, being more active against staphylococci and only slightly less active against streptococci than ceftriaxone. Cefepime maintained activity against bacteria resistant to aminoglycosides and ciprofloxacin. Enterococci, Bacillus species, Burkholderia cepacia and Stenotrophomonas maltophilia were predicably resistant. Cefepime has a spectrum of activity almost as broad as that of the carbapenems.     

Performance of Vitek 2 in antimicrobial susceptibility testing of Pseudomonas aeruginosa isolates with different mechanisms of beta-lactam resistance

A total of 78 isolates of Pseudomonas aeruginosa grouped according to the phenotype for ceftazidime and imipenem susceptibility/resistance were used to assess the accuracy of the Vitek 2 system in antimicrobial susceptibility testing. Comparisons were made with a MIC gradient test for piperacillin-tazobactam, ceftazidime, aztreonam, imipenem, meropenem, gentamicin, and ciprofloxacin. For the total of 546 isolate-antimicrobial combinations tested, the category agreement was 83.6%, with 2.0, 1.6, and 12.8% very major, major, and minor errors, respectively. Vitek 2 accuracy was influenced differently by the mechanism responsible for resistance, and interpretation of the results in relation to phenotype could improve the performance of the system.     

Correlation between sensitivity to fosfomycin and the presence of penicillinase PSE-1 in Pseudomonas aeruginosa

A prospective survey was carried out during three three-weeks periods in May, October 1997 and October 1998 in 13 teaching hospitals. All non-repetitive isolates of P. aeruginosa collected were subject to serotypage and determination of the inhibiting minimal concentrations for ticarcillin, piperacillin, piperacillin + tazobactam, ceftazidime, imipenem, amikacin, ciprofloxacin and fosfomycin. Identification of the betalactamases and quantification of the cephalosporinase were done for the strains intermediate or resistant to ticarcillin. The most frequent serotypes were O: 6 (17%), O: 11 (13%), O: 1 (10%) and O: 12 (9%). Serotype O: 12 was the least susceptible to antibiotics except for fosfomycin. Whatever the serotype, 76% of P. aeruginosa strains with bla PSE-1 are susceptible to fosfomycin, when only 29.8% of non bla PSE-1 producing strains were susceptible to this antibiotic. Integron encoding bla PSE-1 could be implicated in susceptibility to fosfomycin of P. aeruginosa strains. The associations fosfomycin + imipenem or fosfomycin + ceftazidime could be proposed in case of infections due to P. aeruginosa O: 12.     

Development of resistance in Pseudomonas aeruginosa obtained from patients with cystic fibrosis at different times

Objective  Determination of the extent of changes in quantitative resistance in Pseudomonas aeruginosa isolates from patients with cystic fibrosis over a period of approximately 2 years.
Methods  Three hundred and ninety nine isolates of P. aeruginosa collected from 34 pediatric patients in the period between April 1994 and April 1996 were investigated. During the 2 years the children were treated with a combination of a betalactam and an aminoglycoside, approximately every 3 months. In between they received ciprofloxacin orally, when required. The minimal inhibitory concentrations (MICs) of 38 clones of P. aeruginosa defined by different patterns in macrorestriction analysis (pulse field gel electrophoresis, PFGE) were established for 12 antibiotics: gentamicin, amikacin, tobramycin, ciprofloxacin, levofloxacin, moxifloxacin, trovafloxacin, imipenem, meropenem, ceftazidime, cefepime, and piperacillin by means of broth microdilution tests according to DIN 58940.
Results  Twenty-four of the 38 clones developed increased MIC values during the time of observation especially for aminoglycosides and quinolones. Comparatively less affected were ceftazidime, imipenem and meropenem. An association between the number of the intravenous treatment courses and the increase of the MIC values could not be verified.
Conclusions  A trend towards an increase of the MICs against antipseudomonal agents was observed over a limited period of time. It is necessary to prevent this development possibly by employing suitable combinations of antibiotics and the introduction of new substances.     

Evaluation of the performance of rapid antibiotic susceptibility test results using the disk diffusion directly from the positive blood culture bottles

PurposeIn this study, we aimed to evaluate the compliance of rapid antibiotic susceptibility test (RAST) and conventional laboratory procedures.MethodsThe RAST was performed directly from the blood cultures of 71 Gram negative bacilli (GNB) and 38 Gram positive cocci (GPC) isolates. The results were evaluated at fourth, sixth and eighth hour. Categorical agreement (CA), very major error (VME), major error (ME) and minor error (mE) were calculated and compared with the results of conventional Vitek-2 system.ResultsCategorical agreement was detected ≥90 in cefotaxime and meropenem at fourth hour in Escherichia coli isolates. An encourage positive CA results were obtained from meropenem, ceftazidime and ciprofloxacin at the fourth hour in Klebsiella pneumoniae isolates. CA was compatible in imipenem, ciprofloxacin, gentamicin, and tobramycin for Pseudomonas aeruginosa at sixth hour. CA was low (<90%) in piperacillin-tazobactam for E. coli and K. pneumoniae, and meropenem in P. aeruginosa isolates. A good CA (≥90) with all tested antibiotics were found at all hours for Acinetobacter baumannii and also very high CA (100%) was detected at sixth and eighth hour in Staphylococcus aureus isolates. CA remained below the standard criteria at fourth hour in vancomycin and high level gentamicin, in addition to imipenem at sixth hours in enterococci isolates. VME and ME were not detected and mE was 12.7% in GNB and 50% in GPC at eighth hour.ConclusionsEUCAST RAST at eighth hour will be beneficial in urgent patients due to their high CA rate, easy preparation, inexpensive, and could be performed with the available equipment and personnel.     

Antibiotic resistance monitoring of nosocomial clinical isolates

The authors evaluate the epidemiological trend of in vitro resistance of 2,196 clinical isolates, chiefly Gram-negative, in Caltagirone hospital in 1998/99 to piperacillin-tazobactam, piperacillin, cefotaxime, ceftazidime, ceftriaxone, imipenem, ciprofloxacin and tobramicin. The resistance percentage is reported for each year in order to study the phenomenon in time. The following results were obtained: resistance frequently increases or rarely stays constant in time for all antibiotics used; the resistance percentage is very high for some strains of bacteria; monitoring of resistance in a hospital can help in choosing the empirical therapy. Piperacillin-tazobactam, imipenem and ciprofloxacin were the most active drugs against clinical isolates.     

Multicenter study of the in vitro activity of cefepime in comparison with five other broad-spectrum antibiotics against clinical isolates of Gram-positive and Gram-negative bacteria from hospitalized patients in Switzerland

Objective: To assess the in vitro susceptibility of clinical isolates to cefepime and five other antimicrobial agents with broad-spectrum activity.
Methods: The minimal inhibitory concentrations of 1521 Gram-positive cocci and 3170 Gram-negative rods were determined by the Etest procedure.
Results: The susceptibilities were as follows. Gram-positive bacteria: cefepime, 92.7%; ceftazidime, 60.5%; ceftriaxone, 87.8%; imipenem, 92.6%; amikacin, 56.5%; ciprofloxacin, 72.5%. Gram-negative bacteria: cefepime, 97.8%; ceftazidime, 94.3%; ceftriaxone, 83.1%; imipenem, 95.7%; amikacin, 96.6%; ciprofloxacin, 95.8%.
Conclusions: Cefepime had the best activity when compared with the other broad-spectrum β-lactams ceftazidime, ceftriaxone, imipenem, and the non-β-lactams amikacin and ciprofloxacin.     

Antimicrobial susceptibility survey of Pseudomonas aeruginosa strains isolated from clinical sources

A two-year prospective study of 554 Pseudomonas aeruginosa isolates was recovered from various clinical sources throughout Trinidad, and their resistance patterns to antipseudomonal antimicrobial agents were determined. Of the 554 P. aeruginosa isolates, 20.6% (114/554) were community isolates, 17.3% (96/554) from the intensive care unit (ICU), 10.1% (56/554) from the nursery, and the remaining 52% (288/554) were from other hospital inpatient services. Respiratory tract infections were the predominant source of P. aeruginosa isolates from the ICU--46.9% (45/96)--and nursery--21.4% (12/56), whereas wounds were the principal source of P. aeruginosa from the surgical services--77.0% (141/183). Community isolates of P. aeruginosa were predominantly from ear--100% (51/51)--and urinary tract infections--35.5%, (33/93). The overall prevalence of resistance was low for both hospital isolates (13.9%) and community isolates (3.8%). All community isolates were fully sensitive to four of the nine antimicrobials tested. Resistance rates among community strains ranged from 2.6% (ciprofloxacin and ceftazidime) to 12.3% for piperacillin. All isolates from hospital were fully sensitive to imipenem, but resistance rates for the other drugs ranged between 2.5% and 27.3%. The study showed that the overall resistance pattern of P. aeruginosa was relatively low. This is an encouraging observation but invites caution since resistance to the newly introduced drug, cefepime, has now emerged within the hospital environment and may present serious therapeutic problems within the near future. Policies governing the use of antimicrobials in many institutions are lacking. Such policies must be instituted in order to limit the spread of resistance and also to reduce the emergence of resistance to newly commissioned drugs within the country.     

Continuous infusion β-lactams for intensive care unit pulmonary infections

This study evaluated the pharmacodynamics of continuous infusion beta-lactams against pulmonary isolates of Gram-negative bacteria from patients managed in intensive care units (ICUs) in the USA. Multiple 10,000-patient Monte Carlo simulations were performed by integrating pharmacokinetic data from healthy individuals with 2408 MICs from the 2002 Intensive Care Unit Surveillance System database. These pharmacodynamic simulations suggested that continuous infusion regimens of cefepime, aztreonam, ceftazidime and piperacillin-tazobactam 13.5 g have the greatest likelihood of achieving pharmacodynamic targets against isolates of Enterobacteriaceae in the ICU. Beta-lactams are unlikely to achieve pharmacodynamic targets against Pseudomonas aeruginosa or Acinetobacter baumannii when administered as monotherapy.     

Molecular surveillance of European quinolone-resistant clinical isolates of Pseudomonas aeruginosa and Acinetobacter spp. using automated ribotyping

Nosocomial isolates of Pseudomonas aeruginosa and Acinetobacter spp. exhibit high rates of resistance to antibiotics and are often multidrug resistant. In a previous study (D. Milatovic, A. Fluit, S. Brisse, J. Verhoef, and F. J. Schmitz, Antimicrob. Agents Chemother. 44:1102-1107, 2000), isolates of these species that were resistant to sitafloxacin, a new advanced-generation fluoroquinolone with a high potency and a broad spectrum of antimicrobial activity, were found in high proportion in 23 European hospitals. Here, we investigate the clonal diversity of the 155 P. aeruginosa and 145 Acinetobacter spp. sitafloxacin-resistant isolates from that study by automated ribotyping. Numerous ribogroups (sets of isolates with indistinguishable ribotypes) were found among isolates of P. aeruginosa (n = 34) and Acinetobacter spp. (n = 16), but the majority of the isolates belonged to a limited number of major ribogroups. Sitafloxacin-resistant isolates (MICs > 2 mg/liter, used as a provisional breakpoint) showed increased concomitant resistance to piperacillin, piperacillin-tazobactam, ceftriaxone, ceftazidime, amikacin, gentamicin, and imipenem. The major ribogroups were repeatedly found in isolates from several European hospitals; these isolates showed higher levels of resistance to gentamicin and imipenem, and some of them appeared to correspond to previously described multidrug-resistant international clones of P. aeruginosa (serotype O:12) and Acinetobacter baumannii (clones I and II). Automated ribotyping, when used in combination with more discriminatory typing methods, may be a convenient library typing system for monitoring future epidemiological dynamics of geographically widespread multidrug-resistant bacterial clones.