MYSTIC program: summary of European data from 1997 to 2000

Prevalence and Phylodiversity of ESBL-Producing Coliforms Isolated from Ruminant Mastitis in Nigeria

The public health threat posed by Extended-spectrum beta-lactamase producing E. coli (ESBL-EC) in food animal production systems has attracted global attention. Data on the prevalence, diversity and genetic characteristics of ESBL-producing coliforms are key to advocacy on promoting responsible antimicrobial stewardship and proper planning of control strategies. The coliforms were isolated from 1052 milk samples of 160 cows, 103 ewes and 103 does with mastitis in Plateau State, Nigeria and analysed for ESBL production by phenotypic, biochemical, antimicrobial sensitivity and genetic characterization. The percentage of occurrence of clinical mastitis in cows, ewes, and does were 0.2 %, 0 %, 1.5 % respectively, while the percentage occur-rence of subclinical mastitis in ruminants were 18.1 %, 28.2 % and 38.3 % respectively. From the 677 isolates, 31.3 % (n = 212) were ESBL producing coliforms, with a prevalence of 48.6 %, 18.4 %, 12.7 %, 8.9 %, 5.7 %, 3.8 % and 1.9 % for E. coli, K. pneumoniae, C. freundii, K. aerogenes, S. marcescens, K. oxytoca and E. cloacae, respectively. The genetic characterization revealed a higher prevalence of bla CTX-M than bla TEM in the samples analysed (24.39 % vs. 12.19 %). High pairwise identity was observed among the bla CTX-M and bla TEM gene sequences obtained in this study, but they displayed high phylodiversity with sequences from ruminants and humans from other climes. The bla SHV gene was not detected. Multidrug resistances especially to the commonly used antimicrobials; ofloxacin, gentamycin and streptomycin in veterinary practice in Nigeria were observed. This has public health implications considering the fact that consumption of raw unpasteurized milk is a common practice in some cultures in Nigeria. Such practise will facilitate the transfer of multidrug resistant coliforms to humans resulting in the complications of treatment outcomes. To the best of our knowledge this is the first genetic characterization of ESBL-producing agents from ruminant mastitis in Nigeria.

A clinical prediction tool for extended-spectrum β-lactamase-producing Enterobacteriaceae urinary tract infection

Background

Prevalence of extended-spectrum beta-lactamase-producing-Enterobacteriaceae (ESBL-E) has risen in patients with urinary tract infections. The objective of this study was to determine explore the risk factors of ESBL-E infection in hospitalized patients and establish a predictive model.

Methods

This retrospective study included all patients with an Enterobacteriaceae-positive urine sample at the first affiliated hospital of Jinan university from January 2018 to December 2019. Antimicrobial susceptibility patterns of ESBL-E were analyzed, and multivariate analysis of related factors was performed. From these, a nomogram was established to predict the possibility of ESBL-E infection. Simultaneously, susceptibility testing of a broad array of carbapenem antibiotics was performed on ESBL-E cultures to explore possible alternative treatment options.

Results

Of the total 874 patients with urinary tract infections (UTIs), 272 (31.1%) were ESBL-E positive. In the predictive analysis, five variables were identified as independent risk factors for ESBL-E infection: male gender (OR = 1.607, 95% CI 1.066–2.416), older age (OR = 4.100, 95% CI 1.678–12.343), a hospital stay in preceding 3 months (OR = 1.872, 95% CI 1.141–3.067), invasive urological procedure (OR = 1.810, 95% CI 1.197–2.729), and antibiotic use within the previous 3 months (OR = 1.833, 95% CI 1.055–3.188). In multivariate analysis, the data set was divided into a training set of 611 patients and a validation set of 263 patients The model developed to predict ESBL-E infection was effective, with the AuROC of 0.650 (95% CI 0.577–0.725). Among the antibiotics tested, several showed very high effectiveness against ESBL-E: amikacin (85.7%), carbapenems (83.8%), tigecycline (97.1%) and polymyxin (98.2%).

Conclusions

The nomogram is useful for estimating a UTI patient’s likelihood of infection with ESBL-E. It could improve clinical decision making and enable more efficient empirical treatment. Empirical treatment may be informed by the results of the antibiotic susceptibility testing.

Insights into multidrug-resistant K. pneumoniae urinary tract infections: From susceptibility to mortality

The incidence of urinary tract infections (UTIs) caused by Klebsiella pneumoniae has exhibited an increasing trend and has become a high burden for many public health systems, especially in hospital settings. Multidrug resistance associated with the production of extended-spectrum β-lactamases (ESBL) among K. pneumoniae isolates is endemic in Southeastern Europe. We retrospectively analyzed 75 cases admitted to ‘St. Parascheva’ Clinical Hospital of Infectious Diseases in Iasi, Romania, during the first 6 months of 2019 (January 1 to June 30), who had a confirmed diagnosis of K. pneumoniae UTI at discharge. From a total of 75 patients, 34 (45.3%) presented ESBL⁺K. pneumoniae. The mean age was 66 years (70.1 for the ESBL⁺ patients vs. 62.6 for the ESBL^- patients, P=0.0365). There was a symmetrical sex distribution (37 men vs. 38 women). Of these, 22 men had ESBL⁺K. pneumoniae UTIs, compared to only 15 with an ESBL^- strain, P=0.0087. Another risk factor for ESBL⁺K. pneumoniae UTIs was the presence of hospitalization in the past 6 months; 20 (58.82%) patients with ESBL⁺ infections were previously hospitalized, compared to only 5 (12.19%) patients with ESBL^- strains, P<0.0001. The urinary catheter carriers presented an increased prevalence of ESBL⁺ infections (15/34 vs. 5/41, P=0.0012). Regarding mortality, ESBL⁺ infections caused 6 fatalities, compared to only 1 death in the ESBL^- group, P=0.0166. ESBL⁺K. pneumoniae strains represent an important cause of healthcare-related UTIs, with a significantly higher mortality rate compared to ESBL^- strains. Early identification and adequate management of the risk factors incriminated in ESBL⁺ UTIs should be a priority for physicians in order to limit the dissemination of the ESBL-producing strains and thus to improve the outcome of these patients.

Gram Negative Extended Spectrum Beta-Lactamase Producing Bacteria Prevalence in Jouf Region Tertiary Care Hospital, Saudi Arabia

Extended Spectrum beta lactamase producing pathogens are reported in many clinical samples and pose an emerging threat health. To find the prevalence of ESBL producing Enterobactriacea pathogens isolated from inpatients (Medical and Surgical Wards; Hospital stay > 72 h) admitted to Prince, Mutib, Hospital Sakaka, Jouf. A total of 1043 Enterobactriacea were isolated during April 2015 to October 2016 study period. Vitek -2 compact (biomeriux Leon, France) was used for identification and antimicrobial sensitivity (AST) test. A Total of 115/1043 (11.02%) ESBL producing pathogens were isolated from urine 15.07% (n=242), sputum 13.6 % (n=220), wound 10.8% (n=287) and blood 5.4 % (n=294). Klebsiella pneumonia is most dominant followed by E coli and Proteus miribilis. Cephamycins and carbapenems were found most effective (100% sensitivity) against the pathogens isolated. The aminoglycosides, beta lactams and Fluroquinolnes class of antibiotics, microorganisms have gained the resistance of 20%, 22.7%, 40-70% respectively. The infection control measures should be taken seriously and making of effective use of antibiotics is need of hour.

Phenotypic and Molecular Characterization of Multidrug Resistant Klebsiella pneumoniae Isolated from Different Clinical Sources in Al-Najaf Province-Iraq

BACKGROUND AND OBJECTIVE

Burns infections and urinary tract infections are the most important prevalent diseases in Asian countries, such as Iraq. Klebsiella pneumoniae is one of the most important bacteria cause this type of infections especially in hospitals. Therefore, the aim of this study was to investigate the prevalence of multi-drug resistance K. pneumoniae and extended-spectrum beta-lactamases producing K. pneumoniae isolates from inpatients with urinary tract infection and burns infections in Al-Kufa hospital in Al-Najaf province, Iraq.

MATERIALS AND METHODS

A total of 285 clinical samples were collected from in-patients infected with urinary tract infection (141 urine samples) and burns infections (144 burns swabs). Fourteen different antibiotics were used by disc diffusion method and 13 antimicrobials resistance genes were used by PCR technique.

RESULTS

A total of 43 K. pneumoniae strains were isolated. The highest resistance rate was observed for amoxicillin 25 μg and amoxicillin+clavulanic acid 20+10 μg (97.67%) while the lowest resistance rate was observed for imipenem 10 μg (9.30%). The most common resistance associated-genes were blaSHV (86.04%) and at lower prevalence were IMP (9.30%).

CONCLUSION

Klebsiella pneumoniae strains isolated from burns infections were more virulent than those isolated from urinary tract infections.

Risk factors of mortality in bloodstream infections caused by Klebsiella pneumonia: A single-center retrospective study in China

The prevalence of Klebsiella pneumonia bloodstream infections (KP-BSIs) is increasing worldwide. Few study reports focus on the KP-BSIs published in Mainland China over the previous years. This study aimed to describe the risk factors of mortality from KP-BSIs.A retrospective study was conducted in a teaching hospital in Shanghai, China, for a period of 4 years. Risk factors related to the patient mortality were analyzed using the binary logistic regression model.Of 104 patients with KP-BSIs, the overall 30-day mortality rate was 25%. The logistic regression analysis revealed that thrombocytopenia (TB) (odds ratio [OR]: 1.007, 95% confidence interval [CI]: 1.002-1.013), pancreaticobiliary tract (PBT) (OR: 4.059, 95% CI: 1.398-11.78), and intra-abdominal infection (OR: 6.816, 95% CI: 1.806-25.716) were powerful risk factors leading to the mortality associated with KP-BSIs. Although prior antibiotic exposure, inappropriate empirical antibiotics, and inappropriate definitive antibiotics were not associated with mortality, multidrug-resistant (MDR) of KP-BSIs in the present study was high in both survivors and nonsurvivors (67.9% and 88.5%, respectively).TB, PBT, and intra-abdominal infection caused significant mortality rates increase in KP-BSIs during the study period.

Nosocomial urinary tract infections caused by extended-spectrum beta-lactamase uropathogens: Prevalence, pathogens, risk factors, and strategies for infection control

INTRODUCTION

Our goal was to investigate the prevalence and antibiogram pattern of extended spectrum beta-lactamase (ESBL) production among uropathogens using isolates from urine samples collected at the Department of Urology in the Sahloul Hospital, Tunisia We also aimed to identify the risk factors for nosocomial urinary tract infections (UTIs) in patients who underwent transurethral resection of the prostate (TURP) and the measures for infection control.

METHODS

Laboratory records of a five-year period from January 2004 to December 2008 were submitted for retrospective analysis to determine the incidence of ESBL infections. A total of 276 isolates were collected. A case-control study involving comparisons between two groups of patients who underwent TURP was performed to determine the risk factors for ESBL infection. Group 1, designated case subjects, included 51 patients with nosocomial UTI after TURP. Group 2, designated control subjects, consisted of 58 randomly selected patients who underwent TURP without nosocomial UTI in the same period. Factors suspected to be implicated in the emergence of ESBL infection were compared between the two groups in order to identify risk factors for infection. A univariate regression analysis was performed, followed by a multivariate one.

RESULTS

The annual prevalence of ESBL infection ranged from 1.3-2.5%. After performing univariate and multivariate regression analysis, the main risk factors for ESBL infections were identified as: use of antibiotics the year preceding the admission, duration of catheter use, and bladder washout (p=0.012, p=0.019, and p<0.001.

CONCLUSIONS

Urologists have to perform a good hemostasis, especially in endoscopic resections, in order to avoid bladder irrigation and bladder washout and to reduce the time of bladder catheterization, which is a strong risk factor of nosocomial UTIs.

Prevalence of Plasmid-Mediated Quinolone Resistance Determinants and OqxAB Efflux Pumps among Extended-Spectrum β-Lactamase Producing Klebsiella pneumoniae Isolated from Patients with Nosocomial Urinary Tract Infection in Tehran, Iran

Objective. Plasmid-mediated quinolone resistance (PMQR) plays an important role in the development of clinical resistance to quinolone. The aim of this study was to investigate PMQR determinants among extended-spectrum β-lactamases- (ESBL-) producing Klebsiella pneumoniae recovered from patients with nosocomial urinary tract infection (UTI). Methods. A total of 247 ESBL-producing K. pneumoniae isolates were collected from 750 patients with UTI. ESBL production was confirmed by double disc synergy test and combined disc diffusion test. The prevalence of PMQR determinants among ESBL-producing K. pneumoniae was assessed using PCR method. Results. The rates of resistance to antimicrobial agents in present study varied from 14.2% to 98.8%. In comparison with other PMQR genotypes, the frequency of aac(6')-Ib (68.8%) was strikingly high. Of the 247 isolates tested, qnrA, qnrB, qnrS, and qepA genes were present in 3.6%, 1.6%, 1.2, and 2%, respectively. oqxA and oqxB were detected in 56.7% and 54.6% of isolates. The predominant coexisting ESBL and PMQR profile among our isolates included bla CTX-M and aac(6')-Ib, oqxA, oqxB (28.3%) and bla TEM, bla SHV and aac(6')-Ib, oqxA, and oqxB (19.4%) profile.  Conclusion. Given the linkage observed between resistance to quinolones and beta lactam antibiotics, therapeutic protocol with fluoroquinolones and beta lactam antibiotics should be seriously revised in Tehran hospitals.

Prevalence of Extended Spectrum β-lactamase-Producing Klebsiella pneumoniae in Clinical Isolates

Background:

Extended spectrum β-lactamase (ESBL) are gram-negative bacteria that produce the enzyme, β-lactamase, which can break down commonly used antibiotics, such as penicillin and cephalosporins, making infections with ESBL producing bacteria more difficult to treat. Extended spectrum β-lactamase-producing Klebsiella pneumoniae were first reported in 1983 from Germany, and since then a steady increase in resistance against cephalosporins has been seen causing health problems.

Objectives:

The aim of this study was to determine the prevalence of ESBL in strains of K. pneumoniae isolated from different clinical samples.

Patients and Methods:

One hundred and thirty isolates of K. pneumoniae were isolated from different clinical specimens from King Khalid hospital, Hafr Elbatin, Kingdom Saudi Arabia. These isolates were then characterized, tested for antimicrobial susceptibility and screened for ESBL production by the MicroScan WalkAway-96 SI System. Extended spectrum β-lactamase production was confirmed by the phenotypic confirmatory disc diffusion test (PCDDT) and the double disc synergy test (DDST).

Results:

Overall, 76.9% (100) of the isolates were resistant to cefuroxime, cefepime and cefazolin, 69.23% (90) were resistant to cefotaxime, and 46.15% (60) were resistant to cefoxitin. Extended spectrum β-lactamase was detected in 53.8% (70) of K. pneumoniae as detected by the MicroScan “WalkAway-96” SI System and 50.07% (66) by PCDDT and 46.15% (60) by DDST. All K. pneumoniae isolates were resistant to ampicillin followed by both piperacillin and mezlocillin 92.30% (120). K.pneumoniae isolates showed high sensitivity to imipenem (15.38%) (20), followed by ertapenem, tetracycline, tigecycline pipracilline/tazobactam and amikacin (23.07%) (30).

Conclusions:

Our study showed that the prevalence of ESBL-producing K. pneumoniae at King Khalid Hospital was significantly high. Routine detection of ESBL-producing microorganisms is required by each of the laboratory standard detection methods to control the spread of these infections and allow a proper therapeutic strategy. For detection, the phenotypic confirmatory disc diffusion test is simple, sensitive and cost effective. However, there is a need for larger scale drug susceptibility surveillance.

Global dissemination of β2-lactamases mediating resistance to cephalosporins and carbapenems

While the main era of beta-lactam discovery programs is over, these agents continue to be the most widely prescribed antimicrobials in both community and hospital settings. This has led to considerable beta-lactam pressure on pathogens, resulting in a literal explosion of new beta-lactamase variants of existing enzyme classes. Recent advances in the molecular tools used to detect and characterize beta-lactamases and their genes has, in part, fueled the large increase in communications identifying novel beta-lactamases, particularly in Gram-negative bacilli. It now seems clear that the beta-lactams themselves have shaped the field of new enzymes, and the evolution of key amino acid substitutions around the active sites of beta-lactamases continues to drive resistance. Over 130 variants of TEM beta-lactamase now exist, and more are reported in the scientific literature each month. The most disturbing current trend is that many bla structural genes normally limited to the chromosome are now mobilized on plasmids and integrons, broadening the spread of resistance to include carbapenems and cephamycins. Furthermore, in some Enterobacteriaceae, concomitant loss of outer membrane porins act in concert with these transmissible beta-lactamase genes to confer resistance to the most potent beta-lactams and inhibitor combinations available. Continued reviews of the literature are necessary in order to keep abreast of the ingenuity with which bacteria are changing the current genetic landscape to confer resistance to this important class of antimicrobials.

APPROPRIATE AND TIMELY EMPIRICAL ANTIMICROBIAL TREATMENT OF ICU INFECTIONS - A ROLE FOR CARBAPENEMS

Treatment of serious nosocomial infections in the intensive care unit requires swift, effective, well-tolerated and appropriate therapy from the outset. The consequences of inappropriate treatment, i.e. the use of antibiotics that are ineffective against the causative pathogen(s) or delayed therapy, are numerous and impact negatively upon both the patient and the ever-dwindling healthcare resources in many hospitals. Although antibiotics have revolutionised the treatment of infections, their inappropriate and untimely use within the intensive care setting has led to the emergence and spread of antibiotic-resistant bacteria worldwide. Consequently, to ensure successful patient outcomes (reduce morbidity and mortality), it is important that any antibiotic treatment employed is right first time. Treatment of serious infections in the intensive care unit requires an empirical stratagem providing broad-spectrum coverage to a wide range of suspected or difficult-to-treat pathogens such as Pseudomonas aeruginosa. However, to prevent the errors of the past, this needs to be tailored as soon as the pathogen has been identified and resistance patterns are known. The carbapenems are potent parenteral antibiotics, with an ultra-broad spectrum of activity that encompasses multi-drug resistant and difficult-to-treat Gram-negative bacteria. Clinical trial data supports the clinical effectiveness of these agents in patients with difficult to treat pathogens.

Characterization of the extended-spectrum β-lactamases and determination of the virulence factors of uropathogenic Escherichia coli strains isolated from children

BACKGROUND AND AIM

The aim of the study was to characterize ESBL-producing uropathogenic Escherichia coli (UPEC) strains isolated in children. That included the investigation of virulence factors and the analysis of the types of β-lactamases at the molecular genetic level.

MATERIAL AND METHODS

During the 2-year study period, 77 ESBL-producing E. coli strains were recovered from urine samples of febrile children with significant bacteriuria hospitalized at one Croatian hospital. Susceptibility of isolates to bactericidal serum activity was tested by Shiller and Hatch method, while adhesin expression was determined by agglutination methods. Characterization of ESBLs was performed by PCR with specific primers for ESBLs and by sequencing of bla (ESBL) genes. Genotyping of the E. coli isolates was performed by pulsed-field gel electrophoresis (PFGE).

RESULTS

Twenty-seven (35.1 %) and 50 (64.9 %) ESBL-producing UPEC strains were isolated in neonates and infants, respectively. Of 70 strains investigated for the presence of virulence factors, adhesins were detected in 48.6 % strains (8.6 % in the neonate and 40 % in the infants group) giving a statistically significant difference in adhesin expression between the two groups (p < 0.01). Hemolysin was produced by 84.3 %, whereas 70 % of strains were serum-resistant. The bla (TEM) gene was detected in 22 (28 %) and bla (SHV) gene in 57 strains (74 %), whereas bla (CTX-M) gene was detected in only two isolates (2.5%). In ten isolates, bla (TEM) and bla (SHV) were simultaneously detected. Sequencing of bla (SHV) genes revealed that SHV-5 β-lactamase was by far the most prevalent and was found in 51 strains (66 %). The strains were clonally related as demonstrated by PFGE and assigned into ten clusters.

CONCLUSIONS

Infection control measures should be employed and the consumption of expanded-spectrum cephalosporins in the hospital should be restricted.

Prevalence of ESBL-Producing Klebsiella pneumoniae Isolates in Tertiary Care Hospital

Extended-spectrum β lactamases (ESBLs) continue to be a major challenge in clinical setups world over, conferring resistance to the expanded-spectrum cephalosporins. An attempt was made to study the prevalence of ESBL-producing Klebsiella pneumoniae clinical isolates in a tertiary care hospital in Kurnool. A total of hundred collected isolates of Klebsiella pneumoniae was studied for their susceptibility patterns to various antibiotics and detection of ESBL producers by double disc synergy test (DDST) and phenotypic confirmatory disc diffusion test (PCDDT). Of the 100 isolates tested for their antibiogram, 61% isolates have shown susceptibility to 3rd-generation cepholosporins and 39% were resistant. Amoxycillin showed the highest percentage of resistance followed by tetracyclins and cotrimoxazole. Among 39 resistant isolates of Klebsiella pneumoniae, 17 were ESBL producers detected by DDST and PCDDT. ESBL producers were more in the hospital isolates (28%) compared to community isolates (6%). Maximum percentage of ESBL producers were noticed from blood sample with 57.14%. In the present study, a large number of isolates were found to be multidrug resistant and ESBL producers. PCDDT was found to be better than DDST in the detection of ESBLs. Continued monitoring of drug resistance is necessary in clinical settings for proper disease management.

Incidence, risk factors, and outcomes of Klebsiella pneumoniae bacteremia

BACKGROUND

Although Klebsiella pneumoniae is the second most common cause of Gram-negative bloodstream infections, its epidemiology has not been defined in a nonselected population. We sought to describe the incidence of, risk factors for, and outcomes associated with K. pneumoniae bacteremia.

METHODS

Population-based surveillance for K. pneumoniae bacteremia was conducted in the Calgary Health Region (population 1.2 million) from 2000 to 2007.

RESULTS

A total of 640 episodes of K. pneumoniae bacteremia were identified for an overall annual population incidence of 7.1 per 100,000; 174 (27%) were nosocomial, 276 (43%) were healthcare-associated community onset, and 190 (30%) were community acquired. Elderly patients and men were at highest risk for K. pneumoniae bacteremia. Dialysis, solid-organ transplantation, chronic liver disease, and cancer were the most important risk factors for acquiring K. pneumoniae bacteremia. Rates of resistance to trimethoprim/sulfamethoxazole increased significantly during 2000 to 2007. The case fatality rate was 20%, and the annual population mortality rate was 1.3 per 100,000. Increasing age, nosocomial acquisition, non-urinary and non-biliary focus of infection, and several comorbid illnesses were independently associated with an increased risk of death.

CONCLUSION

This is the first population-based study to document the major burden of illness associated with K. pneumoniae bacteremia and identifies groups at increased risk of acquiring and dying of these infections.

Characterization of extended-spectrum beta-lactamases in Enterobacteriaceae causing nosocomial infections in a Zagreb University Hospital

The bacteria producing extended-spectrum beta-lactamases (ESBLs) are increasingly reported. production of ESBLs by Gram-negative bacteria is the major mechanism of resistance to oxymino-cephalosporins and aztreonam. the aim of the present study was to characterize ESBLs produced by Enterobacteriaceae, collected during 2003-2005 in a University Hospital in Zagreb, and to determine the risk factors associated with nosocomial infections due to them. 76 isolates of Enterobacteriaceae were included in the study. Antibiotic susceptibility testing was performed by disk-diffusion and broth microdilution method according to CLSI. beta-lactamases were characterized by PCR and sequencing of bla(ESBL )genes. plasmids were extracted by alkaline lysis method and digested with EcoRI enzyme. Most of the strains displayed CAZ phenotype meaning a higher level of resistance to ceftazidime compared to cefotaxime and ceftriaxone. 50 strains produced SHV-ESBL, 28 tem and 8 CTX-M beta-lactamase. Sequencing of bla(SHV )genes from representative strains revealed SHV-5 beta-lactamase in 6 strains whereas sequencing of bla(CTX-M )genes identified CTX-M-3 beta-lactamase in 3 and CTX-M-15 in 5 strains. Strains were assigned to groups from A to f according to plasmid fingerprinting. The spread of SHV-5-producing strains throughout the hospital units could be due to selective pressure of ceftazidime which is widely prescribed in our hospital thus favoring survival of strains possessing a mutation at the Ambler position 240 responsible for ceftazidime and aztreonam resistance.

Prevalence and molecular characterization of extended-spectrum beta-lactamase-producing Klebsiella pneumoniae in Riyadh, Saudi Arabia

BACKGROUND AND OBJECTIVES

Reports on extended-spectrum beta-lactamases (ESBL) production by Enterobacteriaceae, and especially in Klebsiella pneumoniae, are few in Saudi Arabia. Therefore, we determined the prevalence of ESBL in K pneumoniae from Riyadh and characterized the predominant beta-lactamase gene in these isolates.

METHODS

A total of 400 K pneumoniae samples were isolated from two hospitals in Riyadh during 2007 and screened for production of ESBL using ESBL-E-strips and combined disk methods. PCR assay was used to detect bla(TEM), bla(SHV), and bla(CTX-M) genes.

RESULTS

Phenotypic characterization identified a high ESBL rate of 55% of K pneumoniae isolates. ESBL producing K pneumoniae were PCR positive for SHV, TEM and CTX-M beta-lactamase genes with prevalences 97.3%, 84.1% and 34.1%, respectively. Within the CTX-M family, two groups of enzymes, CTX-M-1 and CTXM- 9-like genes were found with prevalences of 60% and 40%, respectively.

CONCLUSIONS

This study confirms the high rate of ESBL in K pneumoniae clinical isolates in hospitals in Riyadh. This study demonstrates the worldwide spread of bla(CTX-M) genes. This first report of the presence of the bla(CTX-M) gene in clincial isolates in Saudi Arabia is evidence of the continuing worldwide spread of this gene.

Trends in antimicrobial susceptibility of Gram-negative isolates from a paediatric intensive care unit in Warsaw: results from the MYSTIC programme (1997-2007)

OBJECTIVES

The Meropenem Yearly Susceptibility Test Information Collection (MYSTIC) programme is a longitudinal global surveillance study to monitor in vitro data on microbial susceptibility in centres that prescribe meropenem. This overview provides data on the susceptibility of Gram-negative bacteria (n = 1300) isolated from clinical specimens of children hospitalized in a paediatric intensive care unit (ICU) during 1997-2007.

METHODS

MICs of meropenem and eight other antibiotics were determined using the CLSI agar dilution method.

RESULTS

Meropenem, imipenem and ciprofloxacin were most active (>90% susceptibility) against the tested isolates. A greater proportion of Pseudomonas aeruginosa isolates was susceptible to meropenem compared with imipenem. Antibiotic susceptibility of Enterobacteriaceae and Acinetobacter baumannii showed an increase in 2007. Only susceptibility of P. aeruginosa to ceftazidime and cefepime increased. The incidence of extended-spectrum beta-lactamase (ESBL) producers among Enterobacteriaceae isolates decreased from 37% in 1997 to 21.8% in 2007, and AmpC beta-lactamase producers decreased from 24.6% to 5.7%. Consumption of cephalosporins remained the same and piperacillin/tazobactam increased 3-fold. During 11 years, despite an increase in carbapenem consumption, meropenem and imipenem have retained excellent activity against the majority of isolates studied.

CONCLUSIONS

The comparison of antibiotic susceptibility of Gram-negative isolates in 1997 and 2007 showed a trend of increase, and the number of beta-lactamase-producing isolates among Enterobacteriaceae showed a trend of decrease possibly related to changes in antibiotic policy.

Prevalence and spread of extended-spectrum beta-lactamase-producing Enterobacteriaceae in Europe

Extended-spectrum beta-lactamases (ESBLs) represent a major threat among resistant bacterial isolates. The first types described were derivatives of the TEM-1, TEM-2 and SHV-1 enzymes during the 1980s in Europe, mainly in Klebsiella pneumoniae associated with nosocomial outbreaks. Nowadays, they are mostly found among Escherichia coli isolates in community-acquired infections, with an increasing occurrence of CTX-M enzymes. The prevalence of ESBLs in Europe is higher than in the USA but lower than in Asia and South America. However, important differences among European countries have been observed. Spread of mobile genetic elements, mainly epidemic plasmids, and the dispersion of specific clones have been responsible for the increase in ESBL-producing isolates, such as those with TEM-4, TEM-24, TEM-52, SHV-12, CTX-M-9, CTX-M-14, CTX-M-3, CTX-M-15 and CTX-M-32 enzymes.

Antibiotic resistance surveillance over a 4-year period (2000–2003) in Turkey: results of the MYSTIC Program

The Meropenem Yearly Susceptibility Test Information Collection (MYSTIC) Program is a global study that provides antimicrobial susceptibility data in centers prescribing meropenem. The activity of meropenem and 7 broad-spectrum antimicrobials have been examined against 5208 bacterial isolates from 9 Turkish centers between 2000 and 2003. Cumulative susceptibility rates against all species of Enterobacteriaceae combined were ranked as follows: meropenem (99.3%), imipenem (97.6%), cefepime (80.0%), piperacillin-tazobactam (73.6%), ceftazidime (70.3%), ciprofloxacin (70.1%), cefotaxime (66.9%), and tobramycin (67.2%). The production of extended-spectrum beta-lactamases (ESBLs) was detected in 48.7% of Klebsiella pneumoniae and in 19.5% of Escherichia coli isolates. Of ESBL producing K. pneumoniae isolates, 75.7% were resistant to tobramycin, 40.3% to ciprofloxacin, and 48.3% to piperacillin-tazobactam. Only piperacillin/tazobactam and carbapenems were active against more than 50% of Pseudomonas aeruginosa at the National Committee for Clinical Laboratory Standards-susceptible breakpoint, and the carbapenems were the most active compounds against Acinetobacter spp. These data confirm the continued potency of meropenem against Enterobacteriaceae in units where it is actively being prescribed.

High activity of meropenem against Gram-negative bacteria from a paediatric Intensive Care Unit, 2001–2005

The susceptibility of Gram-negative bacterial strains (n=620) isolated from clinical specimens of children hospitalized in a paediatric Intensive Care Unit between 2001 and 2005 was tested. Meropenem, imipenem and ciprofloxacin were most active (>90% susceptibility) against the tested isolates, with no observed reduction in activity over 5 years. A decrease in prevalence of extended-spectrum beta-lactamase and AmpC beta-lactamase producing Enterobacteriaceae from 56.3 to 34.1% was found.

In vitro activities of three carbapenems against recent bacterial isolates from severely ill patients at Swedish hospitals

To study the in vitro activity of imipenem, meropenem and ertapenem against common pathogens isolated from patients in intensive care, haematology and dialysis/nephrology units at 7 Swedish university hospitals, a total of 788 isolates were collected during 2002-2003. The distribution of the isolates was as follows: Escherichia coli (n = 140), Klebsiella spp. (n = 132), Proteus spp. (n = 97), Enterobacter spp. (n = 113), Pseudomonas aeruginosa (n = 126), Acinetobacter spp. (n = 53) and Enterococcus faecalis (n = 127). The susceptibility to the 3 carbapenems was determined by E-test, and the MICs were interpreted according to SRGA criteria. All 3 carbapenems were highly active against Enterobacteriaceae. The overall susceptibility to imipenem, meropenem and ertapenem was 90%, 98% and 93%, respectively. Against Enterobacteriaceae, Enterobacter spp. excluded, ertapenem had an equal or lower MIC(90) than meropenem. Apart from being the most active carbapenem against Enterobacteriaceae, meropenem was also the most active carbapenem against P. aeruginosa, whereas imipenem was the most active drug against Acinetobacter spp. The carbapenems are still potent antibiotics. With the introduction of ertapenem, and an expected increase in the carbapenem consumption due to an increased prevalence of strains with extended-spectrum beta-lactamases, continuous surveillance of carbapenem resistance appears to be warranted, with special attention to P. aeruginosa, Enterobacter and Proteus spp.

Widely distributed and predominant CTX-M extended-spectrum beta-lactamases in Amsterdam, The Netherlands

Three hundred sixty Enterobacteriaceae and nonfermenting gram-negative bacilli, isolated during one week in May 2004 at five hospitals in Amsterdam, The Netherlands, were evaluated for the presence of extended-spectrum beta-lactamases (ESBLs). A prevalence of 7.8% was found, in contrast to the 1% observed in 1997. CTX-M ESBLs dominated, and four types were identified in 18 isolates.

Activity of meropenem and comparators against Pseudomonas aeruginosa and Acinetobacter spp. isolated in the MYSTIC Program, 2002-2004

This study examines the susceptibilities of meropenem and other broad-spectrum antimicrobials tested against bacterial isolates collected from hospitalized patients during 2002-2004 from worldwide medical centers participating in the Meropenem Yearly Susceptibility Test Information Collection (MYSTIC) Program. The in vitro activity of meropenem and 5 comparator antimicrobial agents was assessed against Pseudomonas aeruginosa and Acinetobacter spp. Generally, the susceptibility of Australasian and North American isolates was higher than that of the European and South American isolates. The rank order of activity of the antimicrobial agents tested against a worldwide collection of P. aeruginosa was piperacillin/tazobactam (77.7% susceptible) > meropenem (75.4%) > ceftazidime (70.0%) > imipenem (69.7%) > gentamicin (66.1%) > ciprofloxacin (62.0%). Against a worldwide collection of Acinetobacter spp. meropenem (76.1% susceptible) was the most active compound followed by imipenem (74.7%) > gentamicin (51.9%) > ciprofloxacin (40.5%) > piperacillin/tazobactam (39.8%) > ceftazidime (38.1%). The carbapenems appear to be a valuable option for the treatment of serious nosocomial infections caused by P. aeruginosa or Acinetobacter spp. over a broad geographical region.

An overview of the Meropenem Yearly Susceptibility Test Information Collection (MYSTIC) Program: 1997-2004

This overview provides a summary of the Meropenem Yearly Susceptibility Test Information Collection (MYSTIC) Program over an 8-year period from 1997 to 2004. The evolution of the MYSTIC Program is described, as well as its design compared with other surveillance programs. In addition, the global MYSTIC Program data, published to date, are summarized, and the empiric use of carbapenems, their current indications, and meropenem usage versus resistance was discussed. From 1997 to 2004, 120 medical centers that were actively prescribing meropenem in 32 countries worldwide participated in the program. The MYSTIC Program results demonstrate the sustained potency and continued effectiveness of meropenem globally against clinically relevant Gram-negative and Gram-positive pathogens including extended spectrum beta-lactamase- and AmpC beta-lactamase-producing organisms, which may also display resistance to the fluoroquinolones and/or aminoglycosides. Furthermore, in centers actively prescribing meropenem, resistance to meropenem is not increasing despite greater resistance among the comparator antimicrobial agents. Thus, antipseudomonal carbapenems such as meropenem and imipenem remain an effective treatment option.

Extended-Spectrum β-Lactamases and Clinical Outcomes: Current Data

Nosocomial infections caused by extended-spectrum beta-lactamase (ESBL)-producing gram-negative bacteria complicate therapy and limit treatment options. However, the clinical significance of infections caused by ESBL-producing bacteria remains unclear. A critical examination of the literature provides divergent views of the effect of ESBL carriage on morbidity and mortality and suggests that ESBL production may have its most marked effect on ceftazidime. Effective strategies for the empirical and directed treatment of infections caused by ESBL-producing pathogens include the use of carbapenems and, possibly, the fourth-generation cephalosporin cefepime. Studies indicate that the use of cefepime to treat serious nosocomial infections (e.g., bacteremia, pneumonia, and urinary tract infections) is associated with high rates of microbiological and clinical success. The probability of attaining time above the minimum inhibitory concentration targets of at least 70% of the dosing interval, an important pharmacodynamic indicator of clinical success, is higher with cefepime than with other antimicrobials against Escherichia coli and Klebsiella pneumoniae strains exhibiting ESBL phenotypes. However, for non-ESBL-producing strains, there is no difference in the time above the minimum inhibitory concentration between ceftazidime and cefepime. When used appropriately in institutional settings, cefepime reduces the overall use of cephalosporins, thereby decreasing selection pressure for presumptive ESBL-producing pathogens.

Cryptogenic invasive Klebsiella pneumoniae liver abscess syndrome

BACKGROUND

Klebsiella pneumoniae-associated liver abscesses have distinct clinical and epidemiologic features.

METHODS

We report the unusual case of an American patient with a K. pneumoniae-associated liver abscess and septic spread to other organs. We additionally present a comprehensive review of K. pneumoniae-associated liver abscess syndromes in adults.

RESULTS

We identified three distinct K. pneumoniae liver abscess syndromes: the polymicrobial liver abscess, the monomicrobial cryptogenic noninvasive liver abscess, and the monomicrobial cryptogenic invasive K. pneumoniae-associated liver abscess (CIKPLA) syndromes, with distinct clinical, epidemiologic and outcome features. CIKPLA syndrome typically affects diabetic patients, mainly in Southeast Asia, and is complicated by septic spread to other organs.

CONCLUSIONS

The community-acquired, monomicrobial, K. pneumoniae-associated liver abscess syndromes that typically occur in the USA are mainly noninvasive and affect Asian or Hispanic persons. However, this report provides an alert that CIKPLA syndrome can occur in North America, and physicians need to be aware of it.

Trends in antimicrobial susceptibilities among bacterial pathogens isolated from patients hospitalized in European medical centers: 6-year report of the MYSTIC Surveillance Study (1997-2002)

The Meropenem Yearly Susceptibility Test Information Collection (MYSTIC) Program provides antimicrobial susceptibility data. The activity of meropenem and 7 broad-spectrum antimicrobials have been examined against 12645 bacterial isolates from 14 European centers between 1997 and 2002. Cumulative susceptibility rates against all species of Enterobacteriaceae combined were ranked as follows: meropenem (99.9%) > imipenem (97.7%) > ciprofloxacin (86.0%) > piperacillin-tazobactam (85.6%) > ceftazidime (85.4%) > gentamicin (85.4%) > tobramycin (85.0%) > cefotaxime (83.8%). The carbapenems were also found to be the most active of the classes tested against nonfermentative Gram-negative bacilli. Against methicillin-susceptible Staphylococcus aureus and coagulase-negative staphylococci, all beta-lactams tested (except ceftazidime) had susceptibility rates of > or = 99.0% and > or = 94.3%, respectively. Over the 6-year period, there was no loss of activity or increase in resistance rate for either carbapenem against any of the species tested. These data confirm the continued potency and broad-spectrum activity of meropenem in units where it is actively being prescribed.

In vitro activity of three different antimicrobial agents against ESBL producing Escherichia coli and Klebsiella pneumoniae blood isolates

Extended spectrum beta-lactamases (ESBLs) usually associated with multiple drug resistance, including beta-lactam and non-beta-lactam antibiotics. This resistance can cause Limitation in the choice of drugs appropriate for using in clinical practice, especially in life-threatening infections. In this study we aimed to investigate in vitro activity of meropenem, ciprofloxacine and amikacin against ESBL-producing and non-producing blood isolates of Escherichia coli and Klebsiella pneumoniae strains. Fifty-eight E. coli (21 ESBL-producing, 37 non-ESBL producing) and 99 K. pneumoniae (54 ESBL-producing, 45 non-ESBL producing) strains were included in the study. The presence of ESBL was investigated by double disk synergy test and E-test methods. Antibiotic susceptibility test was done by microdilution method according to NCCLS guideline. In vitro susceptibilities of ESBL producing E. coli and K. pneumoniae strains were found as 100% for meropenem, 33.3% and 25.9% for ciprofloxacine, 94.5% and 83.3% for amikacin. It was observed that; meropenem was equally active agent in both ESBL-producing and non-producing strains, and its activity was not affected by ESBL production. Whereas amikacin activity was minimally affected and ciprofloxacine activity was markedly decreased by ESBL production. In conclusion, meropenem seems to be better choice of antibiotic should be used for ESBL positive life-threatening infections, because of remaining highest activity.

Surveillance for antimicrobial resistance among clinical isolates of Gram-negative bacteria from intensive care unit patients in China, 1996 to 2002

The objective is to investigate the trend of antimicrobial resistance among nosocomial gram-negative bacteria isolated from intensive care units in China. From 1996 to 2002, the minimum inhibitory concentrations (MICs) of 8 antibiotics for 10,585 isolates of gram-negative bacteria from 19 hospitals in 7 central cities were determined by Etest. From 1996 to 2002, a marked decrease in the susceptibility of Pseudomonas aeruginosa to imipenem was noticed along the years (81-62%). Percentage of multidrug resistance of strains in P. aeruginosa obviously increased (11.5% in 1996, 20.5% in 2002). Imipenem kept active against Escherichia coli (99.2-100% susceptible), Acinetobacter spp. (97.6-93.5%), Klebsiella spp. (94.9-100%), Enterobacter spp. (89-96%). Resistance to cephalosporins, ciprofloxacin, and cefoperazone/sulbactam was observed, particularly among E. coli to ciprofloxacin (42-25%) and cefotaxime (78-54%) and Enterobacter spp. to ceftazidime (51-44%) and cefotaxime (50-37%). Piperacillin/tazobactam kept stable and active against P. aeruginosa, E. coli, and Klebsiella spp. (80%), with an increasing trend, but not good, in Enterobacter spp. (63-58%). Extended-spectrum beta-lactamase-producing strains in E. coli (28.6-45.7%) and Klebsiella spp. (25.5-34.9%) increased during 2001-2002. There was no significant increase resistance in Enterobacteriaceae isolates and Acinetobacter spp. to imipenem, but it has obviously decreased activity in P. aeruginosa throughout the 7-year period in China. Resistance of tested gram-negative bacteria to most comparator antimicrobials increased at different levels from 1996 to 2002 in China.

Pathogens resistant to antimicrobial agents: epidemiology, molecular mechanisms, and clinical management

Resistance to antimicrobial drugs is increasing at an alarming rate among both gram-positive and gram-negative bacteria. Traditionally, bacteria resistant to multiple antimicrobial agents have been restricted to the nosocomial environment. A disturbing trend has been the recent emergence and spread of resistant pathogens and resistance traits in nursing homes, the community, as well as in hospitals. This article reviews the epidemiology, molecular mechanisms of resistance, and treatment options for pathogens resistant to antimicrobial drugs.

Antimicrobial resistance rates and clonality results from the Meropenem Yearly Susceptibility Test Information Collection (MYSTIC) programme: report of year five (2003)

The U.S. Meropenem Yearly Susceptibility Test Information Collection (MYSTIC) Programme in the fifth year continues to monitor the spectrum of activity and potency of meropenem within medical centers where carbapenems are used for the treatment of serious infections. The antimicrobial activity of 11 broad-spectrum agents (including initial comparisons for levofloxacin) was assessed against 2,848 isolates in 2003. The minimum inhibitory concentration (MIC) results demonstrate the continued high potency of meropenem against all monitored pathogens. Against all Gram-negative bacilli tested, the overall rank order of susceptibility was meropenem (96.3%) > imipenem (95.6%) > cefepime (93.7%) > tobramycin (91.9%) > piperacillin/tazobactam (90.2%) > ceftazidime (90.1%) > gentamicin (89.6%) > levofloxacin (82.8%) > ciprofloxacin (82.5%) > aztreonam (81.8%) > ceftriaxone (72.3%). Clonal-based resistances were observed that adversely influenced carbapenem resistance rates, particularly among Klebsiella spp. and Acinetobacter baumannii isolates. Continued surveillance of the carbapenem class and other broad-spectrum agents is warranted to monitor activity against pathogens causing serious infections in hospitalized patients.

Antibiotic therapy for Klebsiella pneumoniae bacteremia: implications of production of extended-spectrum beta-lactamases

The prevalence of extended-spectrum beta -lactamase (ESBL) production by Klebsiella pneumonia approaches 50% in some countries, with particularly high rates in eastern Europe and Latin America. No randomized trials have ever been performed on treatment of bacteremia due to ESBL-producing organisms; existing data comes only from retrospective, single-institution studies. In a prospective study of 455 consecutive episodes of Klebsiella pneumoniae bacteremia in 12 hospitals in 7 countries, 85 episodes were due to an ESBL-producing organism. Failure to use an antibiotic active against ESBL-producing K. pneumoniae was associated with extremely high mortality. Use of a carbapenem (primarily imipenem) was associated with a significantly lower 14-day mortality than was use of other antibiotics active in vitro. Multivariate analysis including other predictors of mortality showed that use of a carbapenem during the 5-day period after onset of bacteremia due to an ESBL-producing organism was independently associated with lower mortality. Antibiotic choice is particularly important in seriously ill patients with infections due to ESBL-producing K. pneumoniae.

Bacteraemia in Europe—antimicrobial susceptibility data from the MYSTIC surveillance programme

The in vitro antimicrobial susceptibility of organisms isolated from bacteraemic versus non-bacteraemic patients was evaluated using data (1997-2001) from the Meropenem Yearly Susceptibility Test Information Collection (MYSTIC) Programme. Minimum inhibitory concentration values and susceptibility breakpoints of meropenem and other broad-spectrum antimicrobials were determined using standard methodology. Three thousand one hundred and thirty-six blood culture (BC) isolates and 17261 non-BC isolates were obtained from 51 European MYSTIC centres. Gram-positive bacteria appeared to be more prevalent in BC isolates compared with other sources. Escherichia coli, methicillin-susceptible Staphylococcus aureus and Pseudomonas aeruginosa were isolated most frequently. Antimicrobial susceptibility of isolates from bacteraemic versus non-bacteraemic patients was similar. Meropenem and imipenem were the most active agents against the majority of the Gram-positive and Gram-negative organisms. Ceftazidime, gentamicin and ciprofloxacin generally exhibited the lowest activities against the most commonly isolated organisms. Meropenem was most active against P. aeruginosa and showed the highest potency and activity against all extended-spectrum and AmpC beta-lactamase producers. These results are relevant to the choice of initial, empirical therapy for patients with suspected bacteraemia.

Extended-spectrum β-lactamases: implications for the clinical microbiology laboratory, therapy, and infection control

Extended-spectrum beta-lactamase (ESBL) producing gram-negative bacilli are a growing concern in human medicine today. When producing these enzymes, organisms (mostly K. pneumoniae and E. coli) become highly efficient at inactivating the newer third-generation cephaloporins (such as cefotaxime, ceftazidime, and ceftriaxone). In addition, ESBL-producing bacteria are frequently resistant to many classes of non-beta-lactam antibiotics, resulting in difficult-to-treat infections. This review gives an introduction into the topic and is focused on various aspects of ESBLs; it covers the current epidemiology, the problems of ESBL detection and the clinical relevance of infections caused by ESBL-producing organisms. Therapeutic options and potential strategies for dealing with this growing problem are also discussed in this article.

Antimicrobial spectrum of activity for meropenem and nine broad spectrum antimicrobials: report from the MYSTIC Program (2002) in North America

The Meropenem Yearly Susceptibility Test Information Collection (MYSTIC) Program provides susceptibility data for participating medical centers where carbapenems are utilized. The activity of meropenem and nine broad-spectrum antimicrobial agents were assessed against 3,047 bacterial isolates collected during 2002 from 16 North American sites. The overall rank order of susceptibility of the 10 antimicrobial agents tested against Gram-negative isolates was: meropenem (98%) > imipenem (97%) > cefepime (95%) > tobramycin (93%) > piperacillin/tazobactam = gentamicin (92%) > ceftazidime (91%) > ciprofloxacin (87%) > aztreonam (86%) > ceftriaxone (74%). These results and those from previous years, demonstrate the continued excellent potency and spectrum of activity for meropenem. The utility of meropenem against Pseudomonas aeruginosa isolates has increased steadily with a rise in percent susceptibility each year from 78.2% in 1999 to a present rate of 93.1% susceptible. Conversely, we showed the susceptibility for ciprofloxacin against these same P. aeruginosa isolates has decreased from 82.9 to 72.3% susceptible over four years. Many medical centers have observed a decreased activity of some aminoglycosides, cephalosporins and fluoroquinolones due to increases in rates of extended-spectrum beta-lactamases, Amp C and other resistance mechanisms. Carbapenem resistance remains rarely documented and these beta-lactamase-stable agents appear to be an alternative treatment option for serious community-acquired or nosocomial infections in high risk patient populations.

A comparison of the antimicrobial activity of meropenem and selected broad-spectrum antimicrobials tested against multi-drug resistant Gram-negative bacilli including bacteraemic Salmonella spp.: initial studies for the MYSTIC programme in India

The evolution in India of multi-drug resistant pathogens possessing extended-spectrum beta-lactamases (ESBLs) threatens to compromise the clinical utility of third-generation cephalosporins and monobactams. Using selected resistant strains from a recent Indian 10 centre surveillance study that measured the prevailing incidence of resistance to beta-lactam antibiotics, the potential clinical utility of meropenem was assessed against nine other antimicrobial agents. A total of 212 Gram-negative bacilli were tested, of which 125 were confirmed by reference methods to be ESBL-producers. Meropenem was the most active of the test antimicrobials against these strains and the rank order of susceptibility was meropenem (99.1% susceptible) > piperacillin/tazobactam (76.9%) > ciprofloxacin (42.5%) > aminoglycosides (34.4-39.6%) = other beta-lactams (30.0-39.6%). Of the tested strains only two (Acinetobacter spp. and Pseudomonas putida) showed an intermediate susceptibility (8 mg/l) to meropenem. Of the 57 tested strains of Salmonella spp., three had an ESBL phenotype, confirmed two of the strains. This study confirms the high levels of resistance to beta-lactams agents in India reported elsewhere and also demonstrates, for Escherichia coli and Klebsiella spp., high levels of co-resistance between the tested beta-lactam agents and ciprofloxacin and the aminoglycosides, gentamicin and tobramycin. However, carbapenems such as meropenem, remain a therapeutic option.

Antimicrobial resistance trends in medical centers using carbapenems: report of 1999 and 2000 results from the MYSTIC program (USA)

Trends in susceptibility to antimicrobials were assessed from United States participants using 4488 isolates in the MYSTIC Program, 1999 (10 centers) through 2000 (15 centers). Diverse types of hospitals (general service, university, cancer, federal, pediatric, cystic fibrosis) were enrolled from 13 states. In 2000, oxacillin-susceptible staphylococci were 100% susceptible to meropenem, imipenem, and cefepime; but only 88% of strains were susceptible to ceftazidime. Among Enterobacteriaceae, > or = 96% of Enterobacter spp., Citrobacter spp., and Serratia spp. were susceptible to meropenem, imipenem, and cefepime; but ceftazidime, ceftriaxone, and piperacillin/tazobactam had 5-20% resistance rates. Extended-spectrum beta-lactamase resistance rates in Klebsiella spp. and Escherichia coli (6-7% and 3-5%, respectively) were stable over 2 years. Acinetobacter spp. were 78-81% susceptible to carbapenems but only 63-72% susceptible to ciprofloxacin. Meropenem, tobramycin, and piperacillin/tazobactam were the most active against Pseudomonas aeruginosa, but ciprofloxacin inhibited only 74% in 2000. Overall, meropenem remained the most potent agent, especially against ceftazidime- or piperacillin/tazobactam-resistant strains.