Resistance in gram-negative bacteria: enterobacteriaceae

Fecal carriage of ESBL-producing E. coli and K. pneumoniae in children in Guinea-Bissau: a hospital-based cross-sectional study

Background

In recent years, the world has seen a surge in extended-spectrum β-lactamase (ESBL)-producing bacteria. However, data on the dissemination of ESBL-producing Enterobacteriaceae in the community from systematically enrolled study subjects in Africa remains limited. To determine the prevalence, phenotypic resistance patterns and genetic characteristics of ESBL-producing E. coli and K. pneumoniae in fecal carriage and to analyze associated risk factors in children attending a pediatric emergency department in Guinea-Bissau.

Methodology/Principal Findings

From June to September 2010, children <5 years of age with fever or tachycardia attending a pediatric emergency ward during the day was screened for ESBL carriage in feces. Socio-demographic and health seeking behavior data was collected. Antibiotic susceptibility was tested with VITEK2 and EUCAST disk diffusion method, molecular characterization of ESBL-encoding genes was performed with multiplex PCR and clonal relatedness was established by automated rep-PCR. Of 408 enrolled children 133 (32.6%) were ESBL carriers. In total, 83 E. coli and 91 K. pneumoniae ESBL-producing isolates were obtained. Nearly all isolates were multidrug-resistant. Co-resistance to ciprofloxacin, trimethoprim-sulfamethoxazole and aminoglycosides was common. Of the isolates, 38.5% were co-resistant to these classes plus extended-spectrum cephalosporins, which infers resistance to all easily available antibiotic agents for treatment of gram-negative sepsis in Guinea-Bissau. The predominant resistance-encoding gene subgroup was bla_CTX-M-1 and epidemiologic typing showed that the bacterial ESBL population was highly diverse both for E. coli and K. pneumoniae. Bed sharing with another child <5 years of age was a risk factor for ESBL carriage, indicating crowding as a potential risk factor for transmission of ESBL-producing bacteria.

Conclusions/Significance

Prevalence of ESBL-producing bacteria in this population was high and clonally diverse. This is alarming considering the limited diagnostic and treatment possibilities in Guinea-Bissau and other resource-poor countries.

Cefepime therapy for monomicrobial bacteremia caused by cefepime-susceptible extended-spectrum beta-lactamase-producing Enterobacteriaceae: MIC matters

BACKGROUND

Extended-spectrum ß-lactamase (ESBL)-producing Enterobacteriaceae isolates are important clinical pathogens. In addition, the efficacy of cefepime for such infections is controversial.

METHODS

We performed a retrospective study of monomicrobial bacteremia caused by ESBL producers at 2 medical centers between May 2002 and August 2007. The patients definitively treated with in vitro active cefepime (cases) were compared with those treated with a carbapenem (controls) in a propensity score-matched analysis to assess therapeutic effectiveness. The 30-day crude mortality is the primary endpoint.

RESULTS

A total of 178 patients were eligible for the study. Patients who received cefepime (n = 17) as definitive therapy were more likely to have a clinical failure (odds ratio [OR] 6.2; 95% confidence interval [CI], 1.7-22.5; P = .002), microbiological failure (OR 5.5; 95% CI, 1.3-25.6; P = .04), and 30-day mortality (OR 7.1; 95% CI, 2.5-20.3; P < .001) than those who received carbapenem therapy (n = 161). Multivariate regression revealed that a critical illness with a Pitt bacteremia score ≥ 4 points (OR 5.4; 95% CI, 1.4-20.9; P = .016), a rapidly fatal underlying disease (OR 4.4; 95% CI, 1.5-12.6; P = .006), and definitive cefepime therapy (OR 9.9; 95% CI, 2.8-31.9; P < .001) were independently associated with 30-day crude mortality. There were 17 case-control pairs in the propensity scores matched analysis. The survival analysis consistently found that individuals who received cefepime therapy had a lower survival rate (log-rank test, P = .016).

CONCLUSIONS

Based on the current Clinical and Laboratory Standards Institute susceptible breakpoint of cefepime (minimum inhibitory concentration ≤ 8 μg/mL), cefepime definitive therapy is inferior to carbapenem therapy in treating patients with so-called cefepime-susceptible ESBL-producer bacteremia.

[Urinary infection in patients with neurogenic bladder: patterns of resistance to the most frequent uropathogens]

PURPOSE

To analyze the most frequent causes and resistances of the uropathogens in patients affected by neurogenic bladder.

MATERIAL AND METHODS

A total of 284 patients, in whom a total of 284 urinary cultures were performed, were included. Of these, 106 came from patients with neurological injuries, 28 from a non-neurogenic control group, 75 from patients admitted to the intensive care unit (ICU) of our Hospital and 75 patients who came into the emergency room with the symptoms of an acute urinary tract infection. A quantitative urine culture was performed in a chromogenic media and the resistances of all urine cultures that were positive for one or two micro-organisms were identified and studied.

RESULTS

A total of 67% of the patients with neurological injuries had positive urine cultures compared to 25% of control group patients. The urine cultures of patients admitted into the ICU and those of the Emergency Room group were 100% positive, since the first 75 positive urine cultures were selected for the study. E.coli was the most-frequently microorganism isolated in the group of neurological patients, as well as among the patients from the Emergency Room and from the control group. In the ICU, the most-frequently isolated micro-organism was Enterococcus spp. (19.4%), followed by P. aeruginosa (16.5%). The study of resistances in general E. coli has high rates of resistance to ampicillin and co-trimoxazole and, although to a lesser degree to ciprofloxacin.

CONCLUSIONS

E. coli is the micro-organism most frequently isolated among all of the groups except in the ICU, where it is surpassed by Enterococcus spp. and P. aeruginosa. The resistances among the four population groups studied have different features, overall showing a low rate of resistance to nitrofurantoin and especially to fosfomycin, observed in patients from the Emergency Room or admitted to the ICU and neurological patients.

Role of the small RNA RyhB in the Fur regulon in mediating the capsular polysaccharide biosynthesis and iron acquisition systems in Klebsiella pneumoniae

BACKGROUND

The capsular polysaccharide (CPS) and iron acquisition systems are important determinants of Klebsiella pneumoniae infections, and we have previously reported that the ferric uptake repressor (Fur) can play dual role in iron acquisition and CPS biosynthesis. In many bacteria, Fur negatively controls the transcription of the small non-coding RNA RyhB to modulate cellular functions and virulence. However, in K. pneumoniae, the role played by RyhB in the Fur regulon has not been characterised. This study investigated Fur regulation of ryhB transcription and the functional role of RyhB in K. pneumoniae.

RESULTS

Deletion of fur from K. pneumoniae increased the transcription of ryhB; the electric mobility shift assay and the Fur-titration assay revealed that Fur could bind to the promoter region of ryhB, suggesting that Fur directly represses ryhB transcription. Additionally, in a Δfur strain with elevated CPS production, deletion of ryhB obviously reduced CPS production. The following promoter-reporter assay and quantitative real-time PCR of cps genes verified that RyhB activated orf1 and orf16 transcription to elevate CPS production. However, deletion of ryhB did not affect the mRNA levels of rcsA, rmpA, or rmpA2. These results imply that Fur represses the transcription of ryhB to mediate the biosynthesis of CPS, which is independent of RcsA, RmpA, and RmpA2. In addition, the Δfur strain's high level of serum resistance was attenuated by the deletion of ryhB, indicating that RyhB plays a positive role in protecting the bacterium from serum killing. Finally, deletion of ryhB in Δfur reduced the expression of several genes corresponding to 3 iron acquisition systems in K. pneumoniae, and resulted in reduced siderophore production.

CONCLUSIONS

The regulation and functional role of RyhB in K. pneumoniae is characterized in this study. RyhB participates in Fur regulon to modulate the bacterial CPS biosynthesis and iron acquisition systems in K. pneumoniae.

Antimicrobial susceptibility of Enterobacteriaceae, including molecular characterization of extended-spectrum beta-lactamase-producing species, in urinary tract isolates from hospitalized patients in North America and Europe: results from the SMART study 2009-2010

In 2009-2010, 3646 urinary tract isolates of Enterobacteriaceae spp. were isolated from hospitalized patients in North America and Europe. Extended-spectrum beta-lactamase (ESBL) production was detected in 8.5% and 8.8% of Escherichia coli and Klebsiella pneumoniae, respectively, in North America and in 17.6% and 38.9% for Europe, respectively. The carbapenems (ertapenem and imipenem) were the most active agents in vitro, with ampicillin-sulbactam the least active. Molecular characterization of about 50% of ESBL-positive isolates identified the presence of bla(CTX-M) genes in over 90% of Escherichia coli from both continents. bla(KPC) was more common in North American isolates of K. pneumoniae than in European isolates (21.4% versus 6.9%). bla(TEM) and AmpC genes were infrequent. Enterobacteriaceae spp. isolated from hospitalized patients with urinary tract infections in both North America and Europe are often resistant to commonly used antimicrobials with bla(CTX-M) genes common in both Escherichia coli and K. pneumoniae.

Studies on New Delhi Metallo-Beta-Lactamse-1 producing Acinetobacter baumannii isolated from donor swab in a tertiary eye care centre, India and structural analysis of its antibiotic binding interactions

Gram-negative bacilli, Enterobacteriaceae and Non-fermentors with resistance to carbapenems and metallo beta-lactams are the major cause of concern in clinical problems in current human healthcare. The most highly emerging dreadful Metallo Beta-lactamses is New Delhi metallo-beta-lactamase (blaNDM-1) which confers resistance to carbapenems; susceptible only to colistin and, less consistently to tigecycline, leading to no therapeutic options. In the present study, we demonstrate the effects of cephalosporins and carbepenems on biofilm producing A. baumanii clinical isolate and also to infer the probable inhibitory binding mode through molecular docking studies. The result of MIC on Biofilm producing A. baumanii and the docking analysis results were found to be concordant. Moreover, we also found cephalosporins and carbepenem groups to interact with 162-166 region of blaNDM-1, which is unique for NDM-1 and also documented to be a potential drug targeting region.

Carbapenem therapy for bacteremia due to extended-spectrum-β-lactamase-producing Escherichia coli or Klebsiella pneumoniae: implications of ertapenem susceptibility

A retrospective study was conducted at two medical centers in Taiwan to evaluate the clinical characteristics, outcomes, and risk factors for mortality among patients treated with a carbapenem for bacteremia caused by extended-spectrum-beta-lactamase (ESBL)-producing organisms. A total of 251 patients with bacteremia caused by ESBL-producing Escherichia coli and Klebsiella pneumoniae isolates treated by a carbapenem were identified. Among these ESBL-producing isolates, rates of susceptibility to ertapenem (MICs ≤ 0.25 μg/ml) were 83.8% and 76.4%, respectively; those to meropenem were 100% and 99.3%, respectively; and those to imipenem were 100% and 97.9%, respectively. There were no significant differences in the critical illness rate (P = 0.1) or sepsis-related mortality rate (P = 0.2) for patients with bacteremia caused by ESBL-producing K. pneumoniae (140 isolates, 55.8%) and E. coli (111 isolates, 44.2%). Multivariate analysis of variables related to sepsis-related mortality revealed that the presence of severe sepsis (odds ratio [OR], 15.9; 95% confidence interval [CI], 5.84 to 43.34; P < 0.001), hospital-onset bacteremia (OR, 4.65; 95% CI, 1.42 to 15.24; P = 0.01), and ertapenem-nonsusceptible isolates (OR, 5.12; 95% CI, 2.04 to 12.88; P = 0.001) were independent risk factors. The patients receiving inappropriate therapy had a higher sepsis-related mortality than those with appropriate therapy (P = 0.002), irrespective of ertapenem, imipenem, or meropenem therapy. Infections due to the ertapenem-susceptible isolates (MICs ≤ 0.25 μg/ml) were associated with a more favorable outcome than those due to ertapenem-nonsusceptible isolates (MICs > 0.25 μg/ml), if treated by a carbapenem. However, the mortality for patients with bacteremic episodes due to isolates with MICs of ≤ 0.5 μg/ml was similar to the mortality for those whose isolates had MICs of >0.5 μg/ml (P = 0.8). Such a finding supports the rationale of the current CLSI 2011 criteria for carbapenems for Enterobacteriaceae.

Clinical significance of infections caused by extended-spectrum β-lactamase-producing Enterobacteriaceae blood isolates with inducible AmpC β-lactamase

Few studies have investigated the clinical features and outcomes for extended-spectrum β-lactamase (ESBL)-producing Enterobacter spp., Citrobacter spp., Serratia spp., and Morganella morganii (ECSM) bloodstream infections. This study was performed to investigate the clinical features and outcomes for ESBL-producing ECSM bloodstream infections. Patients with ECSM bloodstream infection were enrolled from October 2006 to March 2008. Of 124 patients with ECSM bacteremia, 30 cases (24.2%) were ESBL-producing isolates. Immunosuppressive drugs use within 30 days (p=0.028), indwelling device at the time of bacteremia (p=0.042) and antibiotics use within 3 months (p=0.022) were independently associated with ESBL production in multivariate analysis. Overall 30-day mortality rate was 19.4% (24/124). When the 30-day mortality rate was evaluated, no significant difference was found between the ESBL group (16.6%; 5/30) and non-ESBL group (20.2%; 19/94). Hospitalization was longer in the ESBL group than in the non-ESBL group (65.4±92.8 vs. 32.9±37.8 days, respectively; p=0.007). The recent use of antibiotics (especially broad-spectrum cephalosporins and other β-lactam antibiotics) was an important risk factor for ESBL among ECSM bacteremia. ESBL production of ECSM isolates was not significantly associated with mortality but ESBL-producing organisms have an important impact on the duration of hospital stay and subsequent medical cost.

An observational study on bloodstream extended-spectrum beta-lactamase infection in critical care unit: incidence, risk factors and its impact on outcome

BACKGROUND

The incidence of nosocomial infections caused by extended-spectrum beta-lactamase (ESBL) producing microbes is increasing rapidly in the last few years. However, the clinical significance of infections caused by ESBL-producing bacteria in ICU patients remains unclear. We did a prospective study to look for incidence, risk factors and outcome of these infections in ICU patients.

METHODS

Consecutive isolates of Escherichia coli and Klebsiella pneumoniae in blood cultures were included for the analysis. Patients were divided into two groups based on the production of ESBL. Primary outcome measure was ICU mortality. Logistic regression analysis was done to identify risk factors for ESBL production.

RESULTS

Among the 95 isolates tested, 73 (76.8%) produced ESBL. Transfer from other hospitals or wards (OR 3.65; 95% CI: 1.3-10.1 and RR 1.35; 95% CI: 1.05-1.73) and previous history of antibiotics usage (OR 3.54; 95% CI: 1.04-11.97 and RR 1.5; 95% CI: 0.89-2.5) were risk factors for ESBL production. There was no significant difference in ICU mortality (p=0.588), need for organ support between two groups.

CONCLUSION

There is a high incidence of ESBL producing organisms causing blood stream infections in critically ill patients. Transfer from other hospitals and previous antibiotic usage are important risk factors for ESBL production. However ESBL production may not be associated with a poorer outcome if appropriate early antibiotic therapy is instituted.

Can phlorotannins purified extracts constitute a novel pharmacological alternative for microbial infections with associated inflammatory conditions?

Bacterial and fungal infections and the emerging multidrug resistance are driving interest in fighting these microorganisms with natural products, which have generally been considered complementary to pharmacological therapies. Phlorotannins are polyphenols restricted to brown seaweeds, recognized for their biological capacity. This study represents the first research on the antibacterial, antifungal, anti-inflammatory and antioxidant activity of phlorotannins purified extracts, which were obtained from ten dominant brown seaweeds of the occidental Portuguese coast.

Phlorotannins content was determined by the specific dimethoxybenzaldehyde (DMBA) method and a yield between 75 and 969 mg/Kg phloroglucinol units (dry matter) was obtained. Fucus spiralis ranked first, followed by three Cystoseira species. The anti-inflammatory potential of the purified extracts was assessed via inhibitory effect on nitric oxide (NO) production by lipopolysaccharide-stimulated RAW 264.7 macrophage cells, Cystoseira tamariscifolia being the one showing promising activity for the treatment of inflammation. NO scavenging ability was also addressed in cell free systems, F. spiralis being the species with highest capacity. The antimicrobial potential of the extracts was checked against five Gram-positive and four Gram-negative bacteria and three fungi strains, that commonly colonize skin and mucosa and are responsible for food contamination. The different extracts were more effective against Gram-positive bacteria, Staphylococcus epidermidis being the most susceptible species. Concerning antifungal activity, Trichophyton rubrum was the most sensitive species.

Although the molecular mechanisms underlying these properties remain poorly understood, the results obtained turn phlorotannins purified extracts a novel and potent pharmacological alternative for the treatment of a wide range of microbial infections, which usually also present an inflammatory component. In addition to the biological properties demonstrated herein, phlorotannins extracts may also be preferred, in order to avoid side effects and allergic reactions commonly associated with synthetic drugs.

The characteristics of NDM-producing Klebsiella pneumoniae from Canada

After recent hospitalization in India (New Delhi and Mumbai), 2 patients, on their return to Canada, presented with lower urinary tract infections due to multiresistant Klebsiella pneumoniae that produced New Delhi metallo-β-lactamase and CTX-M-15. The organisms belonged to clones ST147 and ST340, and were positive for aac(6')-Ib-cr, as well as for the ccdAB and vagCD addiction systems. The bla(NDM) plasmid was located on the IncFIIA and IncA/C replicon groups of plasmids. Clones ST147 and ST340 are also responsible for harbouring bla(KPC), and it is possible that they played an important role in the intercontinental spread of antimicrobial resistance.

Analysis of risk factors associated with antibiotic-resistant Escherichia coli

Antimicrobial-resistant bacteria represent a major threat to human and animal health. We compared equine fecal samples (n=264) from 138 horses from hospital and nonhospital (livery stable and riding school) premises in North West England to determine the prevalence of Escherichia coli, Salmonella, and Campylobacter and rates of antimicrobial-resistant E. coli strains. Campylobacter jejuni was detected only in hospitalized horses (1.1%), and no Salmonella was identified. Data analysis of the horses' management and veterinary treatments (Tx) identified risk factors associated with shedding of antimicrobial-resistant E. coli. The hospital was the major source of resistant and multi-drug-resistant (MDR) E. coli. Moreover, shedding of antimicrobial-resistant E. coli was associated significantly with hospitalization for a gastrointestinal problem (odds ratio [OR]:±95% confidence intervals=8.50:1.79-40.32), receipt of oral antimicrobial Tx (OR=3.52:1.11-11.10), multiple antimicrobial Tx in hospital (OR/Tx=1.05:1.01-1.09), or geldings (OR=4.62:1.23-17.46). Interestingly, intravenous antimicrobial Tx was negatively associated with shedding of antimicrobial-resistant E. coli (OR=0.18:0.04-0.76). MDR E. coli was associated with hospitalization, antimicrobial Tx in hospital (OR/Tx=3.65:1.54-8.68), and increased age (OR/year=1.11:1.03-1.19). Thus, equine hospitals in this geographic location appear to be an important source of antimicrobial-resistant and MDR E. coli strains, but unlikely reservoirs of Salmonella or Campylobacter. Thus, it is important to moderate antimicrobial Tx given to hospitalized horses to lessen exposure and fecal shedding of resistant pathogens.

High prevalence rate of extended-spectrum beta-lactamases (ESBL) among Enterobacteriaceae in a small Brazilian public hospital

The production of extended-spectrum beta-lactamases (ESBL) is considered one of the most important resistance mechanisms that impair antimicrobial treatment of infections caused by Enterobacteriaceae. Data on culture and susceptibility tests were collected from the Clinical Analyses and Research Laboratory charts reporting on patients admitted to the University Hospital of Maringá (HUM) from January 2004 to December 2009. The following Enterobacteriaceae were selected: Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, Enterobacter spp. and Proteus mirabilis. All tests were performed according to the recommendations of the Clinical and Laboratory Standards Institute (biochemical identification; susceptibility tests; initial screening and phenotypic confirmatory tests for ESBL). For Enterobacter spp. isolates, a disk approximation test was carried out, adding a cefepime disk. Seven hundred samples were analyzed, and E. coli was the most prevalent bacteria (n= 356). ESBLs were detected phenotypically in 7.3% of E. coli, 61.7% of K. pneumoniae, 33.3% of K. oxytoca, 7.1% of P. mirabilis, and 13.4% of Enterobacter spp samples. Overall ESBL prevalence reached 22% when all producers were taken together. Although HUM is considered a small-sized hospital, it showed high levels of resistance to antimicrobial agents, similar to those observed in bigger hospitals, which demonstrated the need for careful epidemiological surveillance.

Antimicrobial activity of transition metal acid MoO(3) prevents microbial growth on material surfaces

Serious infectious complications of patients in healthcare settings are often transmitted by materials and devices colonised by microorganisms (nosocomial infections). Current strategies to generate material surfaces with an antimicrobial activity suffer from the consumption of the antimicrobial agent and emerging multidrug-resistant pathogens amongst others. Consequently, materials surfaces exhibiting a permanent antimicrobial activity without the risk of generating resistant microorganisms are desirable. This publication reports on the extraordinary efficient antimicrobial properties of transition metal acids such as molybdic acid (H(2)MoO(4)), which is based on molybdenum trioxide (MoO(3)). The modification of various materials (e.g. polymers, metals) with MoO(3) particles or sol-gel derived coatings showed that the modified materials surfaces were practically free of microorganisms six hours after contamination with infectious agents. The antimicrobial activity is based on the formation of an acidic surface deteriorating cell growth and proliferation. The application of transition metal acids as antimicrobial surface agents is an innovative approach to prevent the dissemination of microorganisms in healthcare units and public environments.

The characteristics of VIM-1-producing Klebsiella pneumoniae from South Africa

A study was designed to characterize a carbapenem-resistant Klebsiella pneumoniae (KPSA01) isolated from a patient in Gauteng, South Africa without recent travel outside South Africa. Molecular characterization was done using isoelectric focusing, polymerase chain reaction and sequencing for bla(VIM), bla(IMP), bla(NDM), bla(CTX-Ms), bla(OXAs), bla(TEMs), and bla(SHV), plasmid-mediated quinolone resistance determinants, multilocus sequencing typing, plasmid replicon typing, and addiction factors. KPSA01 produced VIM-1 and belonged to the newly described sequence type ST569. The plasmid that harboured bla(VIM) typed within the narrow host range IncF replicon group, contained the aadA1 gene cassette, and tested positive for the vagCD and ccdAB addiction systems. This is the first report of VIM-1-producing K. pneumoniae outside Europe. It is important that surveillance studies be undertaken in Africa to determine if VIM-1-producing K. pneumoniae are present in significant numbers.

Antimicrobial resistance status and prevalence rates of extended spectrum beta-lactamase (ESBL) producers isolated from a mixed human population

Owing to the increasing epidemiological and therapeutic challenges associated with infections due to ESBL producers, ESBL prevalence rate among some bacteria isolates from healthy and non-healthy human population in a metropolitan Nigerian setting was evaluated. A total of one hundred and forty-five (145) bacteria strains were isolated from a total of four hundred and sixty (460) samples collected from urine, wound, throat and anal swabs of 220 healthy volunteers in the community and from 240 patients in 2 secondary and 2 tertiary hospitals (altogether, 4) in Enugu metropolis. The presumptive confirmatory test used for ESBL detection was the Double Disc Synergy Test (DDST) method. Conjugation and plasmid curing studies were also done for resistance factor determination. Of the 145 isolates, 20 were ESBL producers with 35% of these ESBL producers being of community origin and 65% from hospitals. This translates to 4.8% and 9% incidences (comparably higher than established prevalence of 4.4% and 7.5 respectively) for community and hospital infections respectively. The ESBL isolates showed high resistance to tetracycline, gentamicin, pefloxacin, ceftriaxone, cefuroxime, ciprofloxacin and Augmentin(®) (Amoxicilin and clavulanic acid combination). Conjugation studies for Resistance plasmid transfer showed non-transference of resistance determinants between the ESBL transconjugants and recipient strains. Correspondingly, the plasmid curing studies revealed that the acridine orange could not effect a cure on the isolates as they still retained high resistance to the antibiotics after the treatment. This study confirms the growing incidences/pool of ESBL strains in Nigeria and call for widespread and continuous monitoring towards an effective management of the potential therapeutic hurdle posed by this trend.

EmmdR, a new member of the MATE family of multidrug transporters, extrudes quinolones from Enterobacter cloacae

We cloned a gene, ECL_03329, from the chromosome of Enterobacter cloacae ATCC13047, using a drug-hypersensitive Escherichia coli KAM32 cell as the host. We show here that this gene, designated as emmdR, is responsible for multidrug resistance in E. cloacae. E. coli KAM32 host cells containing the cloned emmdR gene (KAM32/pEMMDR28) showed decreased susceptibilities to benzalkonium chloride, norfloxacin, ciprofloxacin, levofloxacin, ethidium bromide, acriflavine, rhodamine6G, and trimethoprim. emmdR-deficient E. cloacae cells (EcΔemmdR) showed increased susceptibilities to several of the antimicrobial agents tested. EmmdR has twelve predicted transmembrane segments and some shared identity with members of the multidrug and toxic compound extrusion (MATE) family of transporters. Study of the antimicrobial agent efflux activities revealed that EmmdR is an H+-drug antiporter but not a Na+ driven efflux pump. These results indicate that EmmdR is responsible for multidrug resistance and pumps out quinolones from E. cloacae.

Community-acquired urinary tract pathogens and their resistance patterns in hospitalized children in southeastern Ontario between 2002 and 2006

BACKGROUND

The purpose of the present study was to assess the epidemiology and resistance patterns of bacteria causing urinary tract infections in children who were admitted to Kingston General Hospital (Kingston, Ontario) - the regional tertiary care hospital of southeastern Ontario.

METHODS

A retrospective chart review of patients one to 18 years of age who were admitted to Kingston General Hospital with a discharge diagnosis of urinary tract infection between 2002 and early 2006 was undertaken.

RESULTS

One hundred forty-two patient charts were reviewed, of which 56.3% of patients were female. The mean age of the patients was 12.3 months. The most common bacteria identified on urine culture over a five-year period were Escherichia coli (71.6%), Enterococcus species (5.7%) and Klebsiella species (5.0%). Bacteria were frequently resistant to ampicillin (54.4%) and trimethoprim-sulfamethoxazole (TMP-SMX) (40.4%). During the three months before admission, bacteria resistant to ampicillin were cultured from the urine of 75.6% of patients who were receiving some antibiotic, compared with 44% of children with no documented use of antibiotics (P<0.0001). Resistance to TMP-SMX in those with pre-existing genitourinary disease was 72.2% versus 31.8% in those without (P<0.0001). Patients who had previous admissions for urinary tract infections also showed greater resistance to TMP-SMX (70.6% versus 32.7%; P<0.005), cefazolin (64.7% versus 20.0%; P<0.0001) and nitrofurantoin (58.8% versus 18.2%; P<0.0001).

CONCLUSIONS

There was a high resistance to ampicillin. Risk factors for resistant bacteria included the use of antibiotics three months before admission, previous genitourinary disease and previous admissions for urinary tract infections. In the presence of these risk factors, a third-generation cephalosporin as first-line antimicrobial therapy is recommended. However, the combination of ampicillin plus gentamicin can be considered for empirical therapy in low-risk patients.

Prevalence and genetic characteristics of TEM, SHV, and CTX-M in clinical Klebsiella pneumoniae isolates from Saudi Arabia

The prevalence and genetic basis of extended-spectrum beta-lactamases (ESBLs) in Klebsiella pneumoniae remains unclear in Saudi Arabia. Therefore, this study was devoted to determine the prevalence and characterize ESBL-producing K. pneumoniae in Al-Qassim area, Saudi Arabia. A total of 430 isolates of K. pneumoniae isolated from clinical samples were collected over 6 months from January to June 2008. These isolates were screened for the presence of ESBLs by double-disk synergy test and re-evaluated by E-test ESBL method. Minimum inhibitory concentrations of 15 antibiotics against ESBL-positive strains were determined by E-test strips. The β-lactamases involved were characterized by polymerase chain reaction assays and DNA sequencing. Conjugation experiments were done and ISEcp1 elements were tested among CTX-M positive isolates. The prevalence of ESBL was 25.6% (110/430) and all ESBL-positive isolates were sensitive to imipenem and tigecycline; however, the resistance rate to gentamicin, amikacin, and ciprofloxacin was 87.3%, 10%, and 9.1%, respectively. Of these, 89.1% produced SHV, 70.9% produced TEM, and 36.4% were CTX-M-producing strains. The prevalence of ESBL SHV SHV-12 and SHV-5 was of 60% and 18.2%, respectively, and various non-ESBL SHV, including SHV-1 (5.5%), -11 (3.6%), and -85 (1.8%), was detected. However, the prevalence of CTX-M-15 and CTX-M-14 was 34.5% and 1.8%, respectively. ISEcp1 element was detected in 60% of bla(CTX-M-15) genes. All bla(CTX-M) genes were transferable; however, most of bla(SHV-12) and bla(SHV-5) were not transferable. TEM-type ESBLs were not detected in any of the isolates. This is the first description of CTX-M-14, SHV-5, SHV-11, and SHV-85 in Saudi Arabia. We have documented the dominance of K. pneumoniae SHV-12 and highlighted the emergence of CTX-M-15 in Saudi Arabia.

SugE, a new member of the SMR family of transporters, contributes to antimicrobial resistance in Enterobacter cloacae

We cloned a gene, sugE, from the chromosome of Enterobacter cloacae ATCC 13047. Analysis of the susceptibilities of the sugE-containing strain (Escherichia coli KAM32/pSUGE28) and sugE-deficient E. cloacae (EcΔsugE) showed that SugE confers resistance to cetyltrimethylammonium bromide, cetylpyridinium chloride, tetraphenylphosphonium, benzalkonium chloride, ethidium bromide, and sodium dodecyl sulfate. We also investigated expression of sugE. We confirm here that SugE from E. cloacae is an SMR family transporter as determined by observing its energy-dependent drug efflux activity.

Antimicrobial resistance in the intensive care unit: mechanisms, epidemiology, and management of specific resistant pathogens

Infections caused by drug-resistant and multidrug-resistant microbial pathogens pose tremendous challenges to health care systems, including challenges related to the diagnosis, treatment, and containment of these infections. These challenges are amplified in the intensive care unit (ICU), where pressures for selection and emergence of resistance and risks of transmission of resistant pathogens are highest, and where the threat of resistance drives selection of empiric antimicrobial regimens. This article reviews basic concepts of resistance to antibacterial agents including mechanisms and modes of transmission, and discusses management issues for the important drug-resistant pathogens found in the ICU.

Plasmid typing and resistance profiling of Escherichia fergusonii and other Enterobacteriaceae isolates from South Korean farm animals

In this study, we focused on determining the distribution and prevalence of major plasmid replicons in β-lactam-resistant Escherichia fergusonii and Enterobacteriaceae of animal and human origin. A high degree of plasmid variability and multiple plasmid replicons were observed among the isolates. The IncF and IncI1 replicons were the most prevalent in E. fergusonii and Salmonella enterica serovar Indiana isolated from swine and poultry in South Korea, respectively. The presence of broad-host-range plasmid replicons such as IncN, IncA/C, IncHI1, and IncHI2 that are associated with important virulence genes and toxins as well as antimicrobial resistance determinants indicates that E. fergusonii has the potential to become an important pig pathogen and possible emerging opportunistic zoonotic pathogen.

Resistance patterns and integron cassette arrays of Enterobacter cloacae complex strains of human origin

The aim of this research was to analyse the resistance patterns and characterize the distribution and genetic content of resistance integrons within Enterobacter cloacae complex strains originating from hospitalized patients. The strains were included in the E. cloacae complex study following sequence analysis of the hsp60 gene. The determination of resistance towards eight classes of antimicrobials was followed by PCR detection of integrons and analyses of the size and sequences of their variable parts. The majority of 69 clinical strains of the E. cloacae complex were identified as Enterobacter hormaechei. They were isolated from a variety of samples, including urine, wounds, blood and stools. The remaining isolates belonged to E. cloacae clusters III and IV, E. cloacae subsp. cloacae and Enterobacter kobei. Fifty-two isolates (75.4 %) were resistant to more than three unrelated antibiotics. The resistance for each antibiotic, except imipenem, was significantly associated with the presence of integrons. Class 1 integrons were detected in 55 % of isolates: 63.3 % of 'E. hormaechei subsp. steigerwaltii', 50 % of E. cloacae cluster III, 40 % of 'E. hormaechei subsp. oharae', 33 % belonging to E. cloacae cluster IV and 20 % of 'E. hormaechei subsp. hormaechei' were intI1-positive. All of the integrons were located on transferable genetic elements. The transferred resistance primarily included that to aminoglycosides, ticarcillin, piperacillin, sulfamethoxazole, trimethoprim and tetracycline. Sequence analysis of the variable regions of integrons identified two groups of genes: those encoding aminoglycoside adenylotransferases responsible for resistance to aminoglycosides, and dfr cassettes conferring resistance to trimethoprim. Integrons of the E. cloacae complex showed limited variability of genes encoding resistance to therapeutics and were stable in structure with the following cassette arrays: dfrA12-orfF-aadA2, aadB-aadA2, dfrA1-aadA1 and aacA4-aadA1. Hospital-dependent differences in type and arrays of gene cassettes were observed, which seemed to be conserved and not liable to changes.

In vitro synergistic antimicrobial effect of imipenem and colistin against an isolate of multidrug-resistant Enterobacter cloacae

BACKGROUND/PURPOSE

Enterobacter cloacae is an important nosocomial pathogen responsible for various infections. Little is known about the synergistic effects of imipenem and colistin against multidrug-resistant E. cloacae. Therefore, we investigated the in vitro effects of imipenem and colistin against a clinical isolate of multidrug-resistant E. cloacae.

METHODS

A strain of E. cloacae, designed Ent 831, was isolated from the sputum of a woman who developed severe pneumonia in a medical intensive care unit. Minimal inhibitory concentrations (MICs) of imipenem and colistin were determined by the agar dilution method. The synergistic effects were investigated using the time-kill method.

RESULTS

MICs of imipenem and colistin for E. cloacae strain Ent 831 were 0.5 microg/mL and 1.0 microg/mL, respectively. Using a standard inoculum (5 x 10(5)) CFU/mL), synergism was shown with a concentration of two times the MICs of imipenem and colistin. Furthermore, four times the MIC of imipenem completely inhibited bacterial growth for more than 48 hours, but four times the MICs of colistin resulted in re-growth after 4 hours. There was no synergism between imipenem and colistin at two times the MICs against a high concentration inoculum (6.24 x 10(6)) CFU/mL). Nevertheless, imipenem, with or without colistin, at a concentration of four times MICs could inhibit the growth of bacteria for more than 48 hours.

CONCLUSION

High-dose imipenem, alone or in combination with colistin, is effective against multidrug-resistant E. cloacae. Colistin alone, even at a high dose, is not effective. However, in vitro susceptibility to antimicrobial compounds does not always correlate with clinical success. Thus further testing of these antibiotic combinations in animal models is needed in order to predict their suitability for clinical use.

Mutant prevention concentration (MPC) of ciprofloxacin against Salmonella enterica of epidemic and poultry origin

Salmonella isolates resistant or with reduced susceptibility to quinolones increased in recent years. The mutant prevention concentration (MPC) is a new alternative that can prevent the selection and multiplication of resistant Salmonella spp. strains. The MPC of ciprofloxacin (CipMPC) was evaluated for 312 Salmonella enterica strains of epidemic and poultry origin susceptible and resistant to nalidixic acid (NAL). The CipMPC for NAL-susceptible strains were in the range from 0.002 to 4 μg/ml and for NAL-resistant strains, it ranged from 0.004 to 16 μg/ml. The average MPC/MIC ratio for NAL-resistant strains was higher than NAL susceptible. S. Enteritidis showed the highest CipMPC and the highest MPC/MIC ratio also for NAL-resistant strains and with mutations in gyrA. Serovar Corvallis, a NAL-resistant strain without mutations, and of poultry origin showed the highest CipMPC value. The lowest value was observed for epidemic NAL-susceptible strains serovars Typhimurium and London. The average MPC/MIC ratio for strains with mutations in Aspartate 87 was higher than that mutated in Serine 83. The results show the importance of MPC in determining the correct dosage of Cip for treatment of Salmonella spp.

Clinical characteristics of nosocomial infections in neonatal intensive care unit in eastern China

A retrospective cohort study on nosocomial infections (NI) in the neonatal intensive care unit (NICU) was performed in the Children's Hospital of Zhejiang University, Hangzhou district, China. The most common infection site was pneumonia and bloodstream infection. Low admission age, long NICU stay, and mechanical ventilation were significant risk factors for NI. Klebsiella pneumoniae was the most common pathogen, followed by Acinetobacter baumannii, Staphylococcus epidermidi, Pseudomonas aeruginosa, Enterobacter cloacae, and Stenotrophomonas maltophilia. Antibiotic resistance of the isolated bacterium was high. In conclusion, this study described the clinical characteristics of NI in a Chinese NICU, which might contribute to implementation of more effective therapeutic and preventive strategies.

Oral treatment options for ambulatory patients with urinary tract infections caused by extended-spectrum-beta-lactamase-producing Escherichia coli

An increase in extended-spectrum-beta-lactamase (ESBL)-producing Escherichia coli has been observed in outpatient settings. Consequently, 100 ESBL-positive E. coli isolates from ambulatory patients with clinically confirmed urinary tract infections were collected by a single laboratory between October 2004 and January 2008. Antimicrobial susceptibility testing was carried out using the oral antibiotics fosfomycin, pivmecillinam, and nitrofurantoin and the parenteral antibiotic ertapenem. Susceptibility rates indicate that fosfomycin (97%), nitrofurantoin (94%), and pivmecillinam (85%) could be considered important oral treatment options.

Factors influencing antibiotic resistance burden in municipal wastewater treatment plants

Municipal wastewater treatment plants are recognized reservoirs of antibiotic-resistant bacteria. Three municipal wastewater treatment plants differing on the dimensions and bio-treatment processes were compared for the loads of amoxicillin-, tetracycline-, and ciprofloxacin-resistant heterotrophic bacteria, enterobacteria, and enterococci in the raw inflow and in the treated effluents. The sewage received by each plant, in average, corresponded to 85,000 inhabitant equivalents (IE), including pretreated industrial effluents (<or=30%) in plant activated sludge, 105,000 IE, including pretreated hospital effluents (<or=15%) in plant trickling filter, and 2,000 IE, exclusively of domestic sewage, in plant submerged aerated filter. The presence of pretreated industrial effluents or of pretreated hospital sewage in the raw inflow did not imply significantly higher densities (per milliliter or per IE) of antibiotic-resistant bacteria in the raw wastewater. Longer hydraulic residence periods (24 h) corresponded to higher bacterial removal rates than shorter periods (12 and 9 h), although such efficiency did not imply significant average decreases in the antibiotic resistance prevalence of the treated effluent. The bacterial loads in the treated effluent could be ranked according to the treatment efficiency, suggesting that the characteristics of the raw inflow may have less relevance on the quality of the treated wastewater than other aspects, such as the inflow volume, the type of biological treatment, or the hydraulic residence time.

Extended-spectrum beta-lactamase-producing Enterobacter cloacae in mobile dialysis units in the medical and surgical departments of a university hospital: a case-control study

The objective of this case-control study was to investigate the source of contamination and risk factors for colonisation and infection during an outbreak of extended-spectrum beta-lactamase (ESBL)-producing Enterobacter cloacae in the University Medical Center Freiburg. A risk factor analysis was performed on 23 patients with ESBL-producing E. cloacae in the medical and surgical departments by comparing them with 46 non-colonised controls, who were matched for ward and length of hospital stay. For these, a risk factor analysis was conducted. Suspected sources for transmission of ESBL were examined and staff received training in infection control measures. The higher risk in colonised patients was attributed to dialysis with mobile units [odds ratio (OR): 4.00; 95% confidence interval (CI): 1.05-15.234; P=0.04]. Dialysis units were examined, but no contamination was found. Improvement in dialysis procedures, additional staff training and renewed training in standard precautions led to a substantial fall in case numbers. Risk factor analysis showed that colonised patients carried more invasive devices than controls (central venous catheter: OR: 2.50; 95% CI: 0.74-8.45; P=0.14; Foley catheter: 5.08; 0.61-42.23; P=0.13) and were given a greater number of different antibiotics (penicillins: 2.52; 0.71-8.89; P=0.15; fluoroquinolones: 2.37; 0.77-7.28; P=0.13). The differences in mobile dialysis frequency and antibiotic use between cases and controls were relevant, although the latter was not statistically significant. It was possible to contain the high frequency of ESBL colonisation or infection by reinforcing infection control measures and training the staff involved.

Cationic phosphorodiamidate morpholino oligomers efficiently prevent growth of Escherichia coli in vitro and in vivo

OBJECTIVES

Phosphorodiamidate morpholino oligomers (PMOs) are uncharged DNA analogues that can inhibit bacterial growth by a gene-specific, antisense mechanism. Attaching cationic peptides to PMOs enables efficient penetration through the Gram-negative outer membrane. We hypothesized that cationic groups attached directly to the PMO would obviate the need to attach peptides.

METHODS

PMOs with identical 11-base sequence (AcpP) targeted to acpP (an essential gene) of Escherichia coli were synthesized with various numbers of either piperazine (Pip) or N-(6-guanidinohexanoyl)piperazine (Gux) coupled to the phosphorodiamidate linker. Peptide-PMO conjugates were made using the membrane-penetrating peptide (RXR)(4)XB (X is 6-aminohexanoic acid; B is beta-alanine).

RESULTS

MICs (microM/mg/L) were measured using E. coli: 3 + Pip-AcpP, 160/653; 6 + Pip-AcpP, 160/673; 2 + Gux-AcpP, 20/88; 5 + Gux-AcpP, 10/49; 8 + Gux-AcpP, 10/56; 3 + Pip-AcpP-(RXR)(4)XB, 0.3/2; and 5 + Gux-AcpP-(RXR)(4)XB, 0.6/4. In cell-free protein synthesis reactions, all PMOs inhibited gene expression approximately the same. These results suggested that Pip-PMOs inefficiently penetrated the outer membrane. Indeed, the MICs of 3 + Pip-AcpP and 6 + Pip-AcpP were reduced to 0.6 and 2.5 microM (1.2 and 10.5 mg/L), respectively, using as indicator a strain with a 'leaky' outer membrane. In vivo, mice were infected intraperitoneally with E. coli. Intraperitoneal treatment with 50 mg/kg 3 + Pip-AcpP, 15 mg/kg 5 + Gux-AcpP or 0.5 mg/kg 3 + Pip-AcpP-(RXR)(4)XB, or subcutaneous treatment with 15 mg/kg 5 + Gux-AcpP or (RXR)(4)XB-AcpP reduced bacteria in blood and increased survival.

CONCLUSIONS

Cationic PMOs inhibited bacterial growth in vitro and in vivo, and Gux-PMOs were more effective than Pip-PMOs. However, neither was as effective as the equivalent PMO-peptide conjugates. Subcutaneous treatment showed that 5 + Gux-AcpP or (RXR)(4)XB-AcpP entered the circulatory system, reduced infection and increased survival.

[Enterobacter sakazakii in powdered infant food formulas]

Species of the Cronobacter genus ("Enterobacter sakazakii" s. l.) are emergent food-borne pathogens that can cause rare but severe neonatal meningitis, bacteriaemia, and necrotizing enterocolitis. Preterm, low-birth-weight, and immuno-compromised infants exposed to these bacterial species are at particular risk. Over the last 50 years, the literature has reported, mainly in newborn children, more than one hundred cases of infection due to these pathogens. The objective of this review was to synthesize the recent advances in knowledge of species of the Cronobacter genus, in particular with regards to taxonomy, physiology, pathogenicity, clinical cases, the methods for detection, isolation, and characterization, and their presence in powdered formulae for infants and young children, which were identified as the main infection vector. Researchers and international public health authorities have explored the ways contamination occur to better control the risks of pathogen development. Appropriate analysis and control measures were implemented in areas processing powdered formulae for infants and young children, and caregivers and families were informed to undertake good hygienic practices.

Carbapenem resistance among Klebsiella pneumoniae isolates: risk factors, molecular characteristics, and susceptibility patterns

BACKGROUND

Carbapenem resistance among isolates of Klebsiella pneumoniae has been unusual.

OBJECTIVES

To identify risk factors for infection with carbapenem-resistant K. pneumoniae (CRKP) and to characterize microbiological aspects of isolates associated with these infections.

DESIGN

Retrospective case-control study.

SETTING

A 900-bed tertiary care hospital.

RESULTS

From January 2006 through April 2007, K. pneumoniae was isolated from 461 inpatients; 88 had CRKP infection (case patients), whereas 373 had carbapenem-susceptible K. pneumoniae infection (control subjects). The independent risk factors for infection with CRKP were prior fluoroquinolone use (odds ratio [OR], 1.87 [95% confidence interval [CI], 1.07-3.26]; P=.026), previous receipt of a carbapenem drug (OR, 1.83 [95% CI, 1.02-3.27]; P=.042), admission to the intensive care unit (OR, 4.27 [95% CI, 2.49-7.31]; P<.001), and exposure to at least 1 antibiotic drug before isolation of K. pneumoniae (OR, 3.93 [95% CI, 1.15-13.47]; P=.029). All CRKP isolates carried the bla(KPC) gene. Approximately 90% of the tested isolates carried the bla(KPC-2) allele, suggesting patient-to-patient transmission. Almost all CRKP isolates were resistant to all antibiotics, except to colistin (resistance rate, 4.5%), gentamicin (resistance rate, 7%), and tigecycline (resistance rate, 15%).

CONCLUSIONS

CRKP should be regarded as an emerging clinical threat. Because these isolates are resistant to virtually all commonly used antibiotics, control of their spread is crucial.

Carbapenem-resistant Enterobacter cloacae and the emergence of metallo-beta-lactamase-producing strains in a third-level hospital (Santiago de Compostela, NW Spain)

The purpose of this paper was to investigate the occurrence of carbapenem-resistant Enterobacter cloacae in our institution, to detect the carbapenemase-associated resistance and to determine the genetic relatedness of the isolates. Species identification and antimicrobial susceptibility testing were performed using the Vitek 2 system and Etest. Multiplex polymerase chain reaction-enzyme linked immunosorbent assay (PCR-ELISA) was used for the detection of extended-spectrum beta-lactamase (ESBL)-producers. The bla (IMP) and bla (VIM) genes were amplified by PCR and sequenced. The DiversiLab System was used for strain-typing. During the period 2006-2008, 12 different isolates of carbapenem-resistant E. cloacae (2.3 %) were recovered in our laboratory. Only two positive isolates for the bla (VIM) gene were detected. The minimum inhibitory concentration (MIC) values were higher for all carbapenems in the group of non-metallo-beta-lactamase (MBL)-producers. All isolates showed MIC values <or=2 against this tigecycline. The two bla (VIM-1)-carrying isolates showed different genotypes. For non-MBL-producers, two clonally related clusters were observed. Different mechanisms can be associated with carbapenem-resistance in E. cloacae. MBL-producing strains are less prevalent than those with other mechanisms of resistance. The clonal relationship confirms the risk of spread of these organisms with the transfer of patients to different wards and the persistence of these clones over time or the 'de novo' acquisition of the resistance caused by the selective pressure exerted by antibiotics treatments.

Detection of plasmid-mediated quinolone resistance genes in clinical isolates of Enterobacter spp. in Spain

We have studied by PCR and DNA sequencing the presence of the qnrA, qnrB, qnrS, aac(6')-Ib-cr, qepA, intI1, and ISCR1 genes in 200 clinical isolates of Enterobacter cloacae (n = 153) and E. aerogenes (n = 47) consecutively collected between January 2004 and October 2005 in two hospitals located in Santander (northern Spain) and Seville (southern Spain). Mutations in the quinolone resistance-determining region of gyrA and parC also were investigated in organisms containing plasmid-mediated quinolone resistance genes. The isolates had different resistant phenotypes, including AmpC hyperproduction, extended-spectrum beta-lactamase production, resistance or decreased susceptibility to quinolones, and/or resistance to aminoglycosides. Among the 116 E. cloacae isolates from Santander, qnrS1, qnrB5, qnrB2, and aac(6')-Ib-cr were detected in 22 (19%), 1 (0.9%), 1 (0.9%), and 3 (2.6%) isolates, respectively. Twenty-one, 17, and 2 qnrS1-positive isolates also contained bla(LAP-1), intI1, and ISCR1, respectively. A qnrB7-like gene was detected in one E. aerogenes isolate from Santander. No plasmid-mediated quinolone resistance gene was detected in the isolates from Seville. The qnrS1-containing isolates corresponded to four pulsed-field gel electrophoresis patterns and showed various levels of resistance to quinolones. Six isolates were susceptible to nalidixic acid and presented reduced susceptibility to ciprofloxacin. The qnrS1 gene was contained in a conjugative plasmid of ca. 110 kb, and when the plasmid was transferred to recipient strains that did not have a specific mechanism of quinolone resistance, the ciprofloxacin MICs ranged from 0.047 to 0.125 microg/ml.

A case of multidrug-resistant Salmonella enterica serovar Typhi treated with a bench to bedside approach

We report a relapsed case of a 25 year-old man with multi-drug resistant Salmonella serovar Typhi (MDRST) bacteremia who had recently returned from travel in India. Due to unresponsiveness to ciprofloxacin and ceftriaxone, we examined the strain's resistance to quinolones and extended-spectrum beta-lactamases (ESBLs). The strain had a single gyrA mutation at codon 83 (Ser83Phe), which explains its decreased susceptibility to fluoroquinolone and resistance to nalidixic acid. In the screening tests of ESBLs, TEM-1 was positive, which is beta-lactamase but not ESBL. The patient was finally successfully treated with meropenem and aztreonam. In the presence of clinical unresponsiveness despite favorable sensitivity tests, further laboratory evaluations are needed, which should include studies of genes related to antibiotic resistance and ESBLs. In addition, further prospective trials should be done about the possible inclusion of antibiotics not yet mentioned in the current guidelines. With MDRST on the rise worldwide, the most optimal and effective line of antibiotic defense needs to be devised.

Doripenem activity tested against a global collection of Enterobacteriaceae, including isolates resistant to other extended-spectrum agents

The emergence and rapid dissemination of extended-spectrum beta-lactamase (ESBL)-producing isolates among Enterobacteriaceae coupled with increasing prevalence of stably derepressed and plasmid-borne AmpC producers have rendered broad-spectrum cephalosporins and beta-lactam/beta-lactamase inhibitor combinations less effective. This scenario has required the use of carbapenems for treatment of infections caused by such organisms. In this study, the in vitro activities of doripenem and comparator agents against Enterobacteriaceae, including ESBL- and AmpC-producing strains, were evaluated. A total of 36 614 isolates collected from more than 60 medical centers (2000-2007) were included and tested for susceptibility using reference methods and interpretive criteria, except for doripenem (product package insert). Overall, doripenem inhibited 98.7% of all Enterobacteriaceae tested at <or=0.5 microg/mL. ESBL rates were higher among Klebsiella pneumoniae (from 7.7% to 44.0%, varied by geographic region), followed by Escherichia coli (3.6-14.0%) and Proteus mirabilis (0.8-34.8%). Derepressed AmpC production-mediated resistance rates were highest among Enterobacter cloacae (26.6-38.7%) compared with other species and generally higher for strains isolated in the Asia-Pacific and Latin American regions. Doripenem inhibited 94.3% and 93.7% of the ESBL phenotype and derepressed AmpC isolates, respectively, and these resistances had little adverse influence on doripenem MIC(50) values (nil to 2-fold increases). The observed increase in AmpC- and ESBL-producing Enterobacteriaceae necessitates a greater confidence on carbapenem empiric therapy. Doripenem could represent a valuable choice for broad-spectrum coverage of contemporary Enterobacteriaceae isolates with widespread resistance mechanisms.