Colistin sulfate for decontamination of preservation fluid in kidney transplantation to decrease the incidence of donor-derived infections caused by multidrug-resistant Gram-negative bacteria.

BACKGROUND: Preservation fluid (PF) contamination, especially by multidrug-resistant (MDR) Gram-negative bacteria (GNB), poses a high risk of donor-derived infection (DDI) and severe clinical outcomes. We sought to determine whether the use of colistin sulfate to decontaminate PF in kidney transplantation can decrease the incidence of probable DDI (p-DDI) caused by MDR GNB. METHODS: In a retrospective study of 916 recipients who received deceased donation, 864 PF samples were collected and cultured, and microbiological contaminants were recorded with the recipients' clinical data and outcomes. From March 2016 to May 2019, 624 samples were decontaminated with ceftizoxime, and from June 2019 to March 2021, 240 samples were decontaminated with colistin sulfate. Between-group comparisons were performed to assess the ability of the two decontamination regimens to decrease the incidence of p-DDI, especially MDR GNB-related infection. RESULTS: The overall PF contamination rate was 54.51% (471/864), and 80 samples were positive for MDR GNB contamination. All p-DDIs occurred in the ceftizoxime group (p < 0.001), and 67.65% of p-DDIs were MDR GNB-related. In the ceftizoxime group, 23 of 61 cases of MDR GNB contamination led to related p-DDIs, while none occurred in the colistin sulfate group (p = 0.002). Among the 23 patients with p-DDIs, 5 died due to severe infection, and 2 experienced graft loss. CONCLUSIONS: The goal of decontamination should be to decrease the risk of MDR GNB-related p-DDI, and colistin sulfate could be an effective and feasible option.

Resistance pattern of infected chronic wound isolates and factors associated with bacterial resistance to third generation cephalosporins at Mbarara Regional Referral Hospital, Uganda.

BACKGROUND: The objectives of this study were; (I) to determine the proportion of pathogens isolated from patients with infected chronic wounds in the surgical ward of MRRH that are resistant to the third-generation cephalosporins and (II) to determine the factors associated with resistance to third-generation cephalosporins in the surgical ward of MRRH. METHOD(S): This study was a descriptive analytical survey of bacterial isolates from infected chronic wounds among patients admitted in the surgical ward of MRRH, Uganda. Seventy five (75) study participants were recruited in the study using convenient sampling technique. Bacterial culture and identification was performed using standard microbiology laboratory procedures whereas broth microdilution method was used to establish the susceptibility of the identified pathogens. Data for objective one (1) was summarized as proportions while the categorized variables were analyzed using logistic regression to determine whether they were associated with the resistance patterns. The level of significance was preset at 5% and p-values less than 0.05 were considered statistically significant. RESULTS: Generally, all isolates had complete susceptibility (100%) to Cefoperazone+Sulbactam 2g except 7.1% of proteus spp that were resistant. Of all the bacterial isolates studied, Staphylococcus aureus, Enterobacter agglomerans, providencia spp and pseudomonas earuginosa had complete resistance (100%) to Cefopodoxime 200mg while providencia spp and pseudomomas earuginosa had complete resistance (100%) to Cefixime 400mg and cefotaxime 1g. Finally, higher odds of bacterial resistance to more 2 brands of the third generation cephalosporins were observed among participants who had prior exposure to the third generation cephalosporins (OR, 2.22, 95% CI, 0.80-6.14), comorbidities (OR, 1.76, 95% CI, 0.62-4.96) and those who had more than two hospitalizations in a year (OR, 1.39, 95% CI 0.46-4.25). However, multivariate logistic regression was not performed since no factor was significantly associated with resistance to more than two brands of third generation cephalosporins (p >0.05). CONCLUSION: This study found that cefixime and cefpodoixme had high rates of resistance and should not be used in routine management of infected chronic wounds. In addition, the factors investigated in this study were not significantly associated with bacterial resistance to more than two brands of third generation cephalosporins.

Development and characterization of lyophilized cefpodoxime proxetil-Pluronic® F127/polyvinylpyrrolidone K30 solid dispersions with improved dissolution and enhanced antibacterial activity.

The aim of this study was the development of hard-cellulose capsules containing cefpodoxime proxetil (CEF) (BCS Class II) loaded novel Pluronic® F127 (P127)/Polyvinylpyrrolidone K30 (PVP) solid dispersions (SDs) using ultrasonic probe induced solvent-lyophilization method for effective antibacterial treatment by means of improved saturated aqueous solubility, dissolution rate, reduced particle size, and wettability. SDs were evaluated for physical and solid-state analyses. The solubility of pure CEF was calculated as 0.269 ± 0.005 mg/mL, SDs formulated with P127/PVP exhibited increased solubility from 3.5- to 8-fold. Molecular distribution of CEF in SDs and formation of CEF loaded amorphous polymeric network were confirmed with morphological study, thermal analysis, Fourier-transform infrared spectroscopy (FT-IR), and 1H-NMR studies. Staphylococcus aureus (ATCC 29213), Escherichia coli (ATCC 25922), and Klebsiella pneumoniae (ATCC 700603) were used to investigate the antibacterial effectiveness of the SDs. The minimum inhibitory concentration (MIC) values of the P127/PVP SDs were found 2-8 times lower than the pure CEF. All SDs from hard-cellulose capsules exhibited significantly faster release than unprocessed CEF. The profiles of SDs and reference were detected to be dissimilar according to difference (f1) and similarity factor (f2). Hard-cellulose capsules containing CEF loaded P127/PVP SDs appear to be feasible alternative to commercially available CEF tablets for effective antibacterial therapy at lowest dose.

Antibiotic susceptibility of cultivable aerobic microbiota from the oral cavity of Echis carinatus from Odisha (India).

During a snake bite, the microbes may get transferred to the bite site and may cause secondary infection along with envenomation. The knowledge on the oral bacterial flora of snakes constitutes information important for snake bite management. The inadequately studied oral microflora of snakes differ geographically, temporally and among the members of the same species. The objective of this study is to determine the pattern of oral bacterial flora of Saw-scaled viper (Echis carinatus) and their susceptibility to antibiotics. Oral swabs were collected from nine healthy Saw-scaled vipers, subjected to microbiological, biochemical and molecular characterization. Additionally, these isolates were subjected to antimicrobial susceptibility testing using ICOSA-20-Plus and ICOSA-20-Minus. A wide range of pathogenic bacteria such as Salmonella arizonae, Pseudomonas stutzeri, Proteus penneri, Alcaligenes faecalis; Citrobacter diversus, C. freundii, Enterococcus faecalis, Bacillus anthracis, Staphylococcus sciuri and Achromobacter xylosoxidans were isolated as new additions to the floral diversity of saw scale viper. Most of the isolates were sensitive towards amikacin, azithromycin, imipenem, ciprofloxacin, gentamicin, ofloxacin, sparfloxacin, tobramycin, levofloxacin, kanamycin, tetracycline, and chloramphenicol while resistant to amoxyclav, cephalothin, cefpodoxime, Co-Trimoxazole, oxacillin and penicillin. The present study revealed that the bacterial flora of the oral cavity of Saw-scaled viper is resistant to many common antibiotics, which are often used for the treatment of snake-bite victims.

Repeated Isolation of Extended-Spectrum-ß-Lactamase-Positive Escherichia coli Sequence Types 648 and 131 from Community Wastewater Indicates that Sewage Systems Are Important Sources of Emerging Clones of Antibiotic-Resistant Bacteria.

Antibiotic resistance in bacteria is an emerging problem globally. Resistant bacteria are found in human and animal microbiota, as well as in the environment. Wastewater receives bacteria from all these sources and thus can provide a measurement of abundance and diversity of antibiotic-resistant bacteria circulating in communities. In this study, water samples were collected from a wastewater pump station in a Norwegian suburban community over a period of 15 months. A total of 45 daily samples were cultured and analyzed for the presence of Escherichia coli Eighty E. coli-like colonies were collected from each daily sample and then phenotyped and analyzed for antibiotic resistance using the PhenePlate-AREB system. During the sampling period, two unique E. coli phenotypes with resistance to cefotaxime and cefpodoxime indicating carriage of extended-spectrum ß-lactamases (ESBL) were observed repeatedly. Whole-genome sequencing of 15 representative isolates from the two phenotypes identified these as two distinct clones belonging to the two globally spread E. coli multilocus sequence types (STs) ST131 and ST648 and carrying blaCTX-M-15 The number of ESBL-positive E. coli strains in the community wastewater pump station was 314 of 3,123 (10%) analyzed E. coli strains. Of the ESBL-positive isolates, 37% belonged to ST648, and 7% belonged to ST131. Repeated findings of CTX-M-15-positive ST648 and ST131 over time indicate that these STs are resident in the analyzed wastewater systems and/or circulate abundantly in the community.

Cefpodoxime proxetil.

A comprehensive profile of cefpodoxime proxetil including the nomenclatures, formulae, elemental composition, appearance, uses, and applications. The methods which were developed for the preparation of the drug substance and their respective schemes are outlined. The physical characteristics of the drug including the ionization constant, solubility, X-ray powder diffraction pattern, differential scanning calorimetry, thermal behavior, and spectroscopic studies are included. The methods which were used for the analysis of the drug substance in bulk drug and/or in pharmaceutical formulations includes the compendial, spectrophotometric, electrochemical and the chromatographic methods. The other studies which was carried out on this drug substance are including the drug stability, pharmacokinetics, bioavailability, drug evaluation, comparison and several compiled reviews. Finally, more than two hundred references are listed at the end of this profile.

Potential of a polyherbal drug to prevent antimicrobial resistance in bacteria to antibiotics.

Persistence of antibacterial drugs for prolonged period in milk increases the probability of antimicrobial resistance progress. Ceftizoxime was found to be excreted in milk for a prolonged period in goats, cows and buffaloes following intravenous injection of ceftriaxone and ceftizoxime. A single dose of ceftriaxone was administered intravenously in healthy control goats (group I) and a single oral dose of the commercial mammary protective polyherbal drug (1.9 gm) was given one hour prior to intravenous ceftriaxone injection in healthy (group II) and induced mastitic (group III) goats to evaluate milk disposition of ceftizoxime following single intravenous dosing of ceftriaxone at 42.25 mg kg-1.Ceftriaxone/ceftizoxime was analyzed by HPLC. The t1/2α and t1/2ß values were 14.755 ± 2.733 and 149.079 ± 18.565 hour, respectively indicating prolonged persistence of ceftizoxime in milk. The polyherbal drug increased the milk concentration at later hours and hastened the excretion of ceftizoxime from milk compared to control group. Ceftriaxone could not be detected in milk. The study suggested that adjunct single or repeated therapy of  the polyherbal drug may cause non persistence of ceftriaxone and shorter persistence of ceftizoxime in milk.

Increased exposure to extended-spectrum ß-lactamase-producing multidrug-resistant Enterobacteriaceae through the consumption of chicken and sushi products.

The aim of this study was to determine the occurrence and patterns of resistance of extended-spectrum ß-lactamase (ESBL) producing Enterobacteriaceae in food products purchased in Navarra, northern Spain. A total of 174 samples of fish and chicken were analyzed from September 2015 to September 2016, including raw and ready-to-eat products: trout (n = 25), salmon (n = 28), panga (n = 13), chicken nuggets and chicken scalopes (n = 32), sushi (n = 31) and sliced cooked poultry (n = 45). Cefpodoxime-resistant strains were isolated on ChromID ESBL agar and further phenotypic (antimicrobial study on MicroScan© NM37 panel) and genotypic characterization (multiplex PCR, sequencing and multi-locus sequence typing, MLST) was performed to confirm and characterize ESBL producers. Raw chicken and sushi have been determined as the most risky products regarding transmission of ESBL-producing Enterobacteriaceae (occurrence 53.1% and 19.4%, respectively), while sliced cooked poultry products appear to be a safe product in this aspect. With regard to raw fish, prevalence in salmon was lower (3.6%) than in trout and panga (16.0%). Ninety-eight per cent of ESBL isolates (n = 50) show multidrug-resistant profiles, highlighting the high resistances against quinolones and tetracyclines observed in chicken isolates, as well as against ertapenem and chloramphenicol in sushi strains. Predominant ß-lactamase type was SHV-12 (50.1%), followed by TEM-type (24.5%) and CTX-M (20.8%). In addition, CTX-M type was only detected in chicken products. The phylogenetic study showed the prevalence of groups A (35%), F (25%) and B1 (15%), usually related to nonvirulent strains. MLST E. coli isolates (n = 20) were grouped into 5 clonal complexes (CC) and 15 sequence types (ST), showing high clonal diversity. ST117 was the prevalent sequence type, while the human pathogen ST131 was not detected in this study. The high prevalence of ESBL-producing multidrug-resistant Enterobacteriaceae detected in products of widespread consumption such as chicken and sushi, increases the concern regarding human exposure to superbugs and encourages the need to improve surveillance of this public health issue.

The performance of a resazurin chromogenic agar plate with a combined disc method for rapid screening of extended-spectrum-ß-lactamases, AmpC ß-lactamases and co-ß-lactamases in Enterobacteriaceae.

A promising means of rapid screening of extended-spectrum-ß-lactamase (ESBL), AmpC ß-lactamase, and co-production of ESBL and AmpC that combines resazurin chromogenic agar (RCA) with a combined disc method is here reported. Cefpodoxime (CPD) discs with and without clavulanic acid (CA), cloxacillin (CX) and CA+CX were evaluated against 86 molecularly confirmed ß-lactamase-producing Enterobacteriaceae, including 15 ESBLs, 32 AmpCs, nine co-producers of ESBL and AmpC and 30 carbapenemase producers. The CA and CX synergy test successfully detected all ESBL producers (100% sensitivity and 98.6% specificity) and all AmpC producers (100% sensitivity and 96.36% specificity). This assay also performed well in screening for co-existence of ESBL and AmpC (88.89% sensitivity and 100% specificity). The RCA assay is simple and inexpensive and provides results within 7 hr. It can be performed in any microbiological laboratory, in particular, in geographic regions in which ESBL, AmpC or co-ß-lactamase-producing Enterobacteriaceae are endemic.

Evaluation of the relationship between the minimum inhibitory concentration of ceftiofur and third-generation cephalosporins in Escherichia coli isolates from food-producing animals.

To enable future comparison of the antimicrobial susceptibility data between bacteria obtained from animals and humans, it is necessary to compare the relationships between minimum inhibitory concentrations (MICs) of veterinary and human medicine. We evaluated the relationship between the MIC of ceftiofur (CTF) and the MICs of other third-generation cephalosporins (TGCs): cefotaxime (CTX), cefpodoxime (CPDX), and ceftazidime (CAZ), determined by the broth microdilution method using 118 cefazolin-resistant Escherichia coli isolates from food-producing animals. Using the Clinical and Laboratory Standards Institute criteria, very major classification errors were observed only in CAZ (17.8%, 21 of 118); major and minor errors were observed in all TGCs (CTX: 0.8% [1 of 118] and 9.3% [11 of 118]; CPDX: 9.3% [11 of 118] and 6.8% [8 of 118]; CAZ: 2.5% [3 of 118] and 9.3% [11 of 118], respectively). The Spearman correlation coefficients between the MICs of CTF and CTX, CPDX, and CAZ were 0.765, 0.731, and 0.306, respectively. The sensitivity and specificity values were 100.0% and 81.8% for CTX, 99.0% and 27.3% for CPDX, and 76.0% and 86.4% for CAZ compared with CTF. The C-statistic was 0.978 for CTF and CTX, 0.953 for CPDX, and 0.798 for CAZ. For the TGCs evaluated in our study, testing for CTX susceptibility results showed the highest correlation with the results given when testing for CTF susceptibility.

ESBL Detection: Comparison of a Commercially Available Chromogenic Test for Third Generation Cephalosporine Resistance and Automated Susceptibility Testing in Enterobactericeae.

Rapid detection and reporting of third generation cephalosporine resistance (3GC-R) and of extended spectrum betalactamases in Enterobacteriaceae (ESBL-E) is a diagnostic and therapeutic priority to avoid inefficacy of the initial antibiotic regimen. In this study we evaluated a commercially available chromogenic screen for 3GC-R as a predictive and/or confirmatory test for ESBL and AmpC activity in clinical and veterinary Enterobacteriaceae isolates. The test was highly reliable in the prediction of cefotaxime and cefpodoxime resistance, but there was no correlation with ceftazidime and piperacillin/tazobactam minimal inhibitory concentrations. All human and porcine ESBL-E tested were detected with exception of one genetically positive but phenotypically negative isolate. By contrast, AmpC detection rates lay below 30%. Notably, exclusion of piperacillin/tazobactam resistant, 3GC susceptible K1+ Klebsiella isolates increased the sensitivity and specificity of the test for ESBL detection. Our data further imply that in regions with low prevalence of AmpC and K1 positive E. coli strains chromogenic testing for 3GC-R can substitute for more time consuming ESBL confirmative testing in E. coli isolates tested positive by Phoenix or VITEK2 ESBL screen. We, therefore, suggest a diagnostic algorithm that distinguishes 3GC-R screening from primary culture and species-dependent confirmatory ESBL testing by ßLACTATM and discuss the implications of MIC distribution results on the choice of antibiotic regimen.

In Vitro Efficacy of Six Alternative Antibiotics against Multidrug Resistant Escherichia Coli and Klebsiella Pneumoniae from Urinary Tract Infections.

INTRODUCTION: Increasing resistance in Escherichia coli and Klebsiella pneumoniae to firstline antibiotics makes therapeutic options for urinary tract infections (UTIs) challenging. This study investigated the in vitro efficacies of 6 antibiotics against multidrug resistant (MDR) uropathogens. MATERIALS AND METHODS: Minimum inhibitory concentrations to ceftibuten, cefpodoxime, fosfomycin, mecillinam, temocillin, and trimethoprim were determined against 155 MDR-isolates of E. coli and K. pneumoniae. The presence of extended-spectrum beta-lactamases (ESBL) and plasmid-borne AmpC enzymes was determined by phenotypic testing with genotyping performed by multiplex polymerase chain reaction. RESULTS: Temocillin demonstrated highest susceptibility rates for both E. coli (95%) and K. pneumoniae (95%) when breakpoints for uncomplicated UTIs were applied; however, temocillin susceptibility was substantially lower when "systemic infection" breakpoints were used. Fosfomycin demonstrated the best in vitro efficacy of the orally available agents, with 78% and 69% of E. coli and K. pneumoniae isolates susceptible, respectively. The next most effective antibiotics were ceftibuten (45%) and mecillinam (32%). ESBL and ampC genes were present in 47 (30%) and 59 (38%) isolates. CONCLUSION: This study demonstrated few oral therapeutic options for MDR-uropathogens, with fosfomycin demonstrating the best in vitro activity.

Comparison of 2 chromogenic media for the detection of extended-spectrum ß-lactamase producing Enterobacteriaceae stool carriage in nursing home residents.

ChromID ESBL agar and Brilliance ESBL agar were compared for the isolation of extended-spectrum ß-lactamase (ESBL)-producing Enterobacteriaceae from 298 stools. These had comparable sensitivity and selectivity for the 116 positive samples. Pre-enrichment with cefpodoxime and extending incubation to 48 hours after direct plating both significantly increased sensitivity but reduced selectivity of both agars.

Changes in the six most common sequence types of Neisseria gonorrhoeae, including ST4378, identified by surveillance of antimicrobial resistance in northern Taiwan from 2006 to 2013.

BACKGROUND: There has been no longitudinal study of drug susceptibility in Neisseria gonorrhoeae in Taiwan since 2006. METHODS: We collected 1090 gonococcal isolates from Taipei City Hospital, Taiwan from April 2006 to August 2013. We used a disk diffusion assay to determine the susceptibility to five antibiotics and an E-test to determine the minimum inhibitory concentrations for cefixime and ceftriaxone in isolates with resistance. Neisseria gonorrhoeae-multi Antigen Sequence Typing and DNA sequencing of the por and tbpB genes were used to identify sequence types. RESULTS: Among the 1090 isolates, the resistances to penicillin, ciprofloxacin, cefpodoxime, cefixime, and ceftriaxone were 61.01%, 83.39%, 9.63%, 6.70%, and 2.39%, respectively. The highest minimum inhibitory concentrations of cefixime and ceftriaxone were 0.19 mg/L and 0.50 mg/L, respectively. There were 327 sequence types. The four most common sequence types in homosexuals were ST4378, ST359, ST4654, and ST547; the two most common sequence types in heterosexuals were ST421 and ST419. Each of these sequence types had more than 25 isolates. There were significant differences in the sequence types in patients with different sexual orientations (p < 0.001). CONCLUSION: Oral cefixime or ceftriaxone injections were used as first-line drugs for the treatment of gonorrhea from 2006 to 2013 because gonorrhea isolates had low minimum inhibitory concentrations for these two drugs. The abrupt emergence of ST4378 (closely related to the notorious ST1407) since 2009 is a cause for alarm. Changes in sexual behavior, including an increase in sexual activity without the use of condoms, may have contributed to the peak in gonorrhea in 2010. Further molecular epidemiological investigations are required.

Evaluation of cefazolin as a surrogate marker for cefpodoxime susceptibility for urinary tract isolates.

Of the cephalosporins, cefpodoxime has the most published clinical data for the treatment of urinary tract infections. In 2014, the Clinical and Laboratory Standards Institute (CLSI) guidelines recommended that cefazolin should be used as the surrogate marker for cefpodoxime among urinary tract isolates, replacing cephalothin. This study attempted to determine how well cefazolin serves as the surrogate marker. Additionally, it investigated how cefuroxime compared with cefazolin as a surrogate marker. The MicroScan Walkaway Plus system was used to determine susceptibility for cefazolin and cefuroxime on consecutive urine cultures with a colony count of ≥ 50 000 organisms. Only Escherichia coli, Klebsiella pneumoniae and Proteus mirabilis isolates were included, following CLSI guidelines. Simultaneously, an Etest for cefpodoxime was conducted. The cefpodoxime interpretation was compared with that of the other two agents, and the categorical agreement was calculated, defined as the percentage of identical susceptibility interpretations. Cefazolin (92 %) had a significantly higher categorical agreement than cefuroxime (85 %) among 284 isolates (P = 0.011). The major error rate was 4.4 % for cefazolin and 1.1 % for cefuroxime. The very major error rate was 64 % for cefazolin and 18 % for cefuroxime among the 11 cefpodoxime-resistant isolates. Cefazolin was a better predictor of cefpodoxime susceptibility than the previously recommended agent, cephalothin. However, cefuroxime had better major and very major error rates than cefazolin.

Human serum paraoxonase-1 (hPON1): in vitro inhibition effects of moxifloxacin hydrochloride, levofloxacin hemihidrate, cefepime hydrochloride, cefotaxime sodium and ceftizoxime sodium.

In this study, we investigated the effects of antibacterial drugs (moxifloxacin hydrochloride, levofloxacin hemihidrate, cefepime hydrochloride, cefotaxime sodium and ceftizoxime sodium) on human serum paraoxonase-1 (hPON1) enzyme activity from human serum in vitro conditions. For this purpose, hPON1 enzyme was purified from human serum using simple chromatographic methods. The antibacterial drugs exhibited inhibitory effects on hPON1 at low concentrations. Ki constants were calculated to be 2.641 ± 0.040 mM, 5.525 ± 0.817 mM, 35.092 ± 1.093 mM, 252.762 ± 5.749 mM and 499.244 ± 10.149 mM, respectively. The inhibition mechanism of moxifloxacin hydrochloride was competitive, whereas levofloxacin hemihidrate, cefepime hydrochloride, cefotaxime sodium and ceftizoxime sodium were noncompetitive inhibitors.

Formulation of extended release cefpodoxime proxetil chitosan-alginate beads using quality by design approach.

The purpose of this work was to develop and characterize chitosan-alginate beads for the extended delivery of cefpodoxime proxetil (CFP), to understand the impact of formulation and process parameters on the critical quality attributes (CQAs) using a quality-by-design approach. For this, a study was performed with various formulation and process parameters to determine their impact on CQAs of beads, which were determined to be time for 80% of the drug released (T80%), particle size, and encapsulation efficiency. The beads of CFP were optimized using a three-factor, three-level Box-Behnken design. A formulation comprising of 4.38% (w/v) alginate, 1.39% (w/v) chitosan and 6.82% (w/v) calcium chloride was found to fulfill requisites of an optimum formulation. In vitro release studies showed that the drug is released from the optimized formulation over a period of 24h in a sustained release manner, primarily by non-Fickian diffusion. The optimized formulation was characterized by DSC, FTIR, XRD and SEM analysis. Antimicrobial studies revealed that the release of the drug over 24h periods was above the minimum concentration required for inhibition of microbial growth. This research highlights the level of understanding that can be accomplished through a well designed study based on the approach of QbD.

Association of veterinary third-generation cephalosporin use with the risk of emergence of extended-spectrum-cephalosporin resistance in Escherichia coli from dairy cattle in Japan.

The use of extended-spectrum cephalosporins in food animals has been suggested to increase the risk of spread of Enterobacteriaceae carrying extended-spectrum ß-lactamases to humans. However, evidence that selection of extended-spectrum cephalosporin-resistant bacteria owing to the actual veterinary use of these drugs according to criteria established in cattle has not been demonstrated. In this study, we investigated the natural occurrence of cephalosporin-resistant Escherichia coli in dairy cattle following clinical application of ceftiofur. E. coli isolates were obtained from rectal samples of treated and untreated cattle (n = 20/group) cultured on deoxycholate-hydrogen sulfide-lactose agar in the presence or absence of ceftiofur. Eleven cefazoline-resistant isolates were obtained from two of the ceftiofur-treated cattle; no cefazoline-resistant isolates were found in untreated cattle. The cefazoline-resistant isolates had mutations in the chromosomal ampC promoter region and remained susceptible to ceftiofur. Eighteen extended-spectrum cephalosporin-resistant isolates from two ceftiofur-treated cows were obtained on ceftiofur-supplemented agar; no extended-spectrum cephalosporin-resistant isolates were obtained from untreated cattle. These extended-spectrum cephalosporin-resistant isolates possessed plasmid-mediated ß-lactamase genes, including bla(CTX-M-2) (9 isolates), bla(CTX-M-14) (8 isolates), or bla(CMY-2) (1 isolate); isolates possessing bla(CTX-M-2) and bla(CTX-M-14) were clonally related. These genes were located on self-transmissible plasmids. Our results suggest that appropriate veterinary use of ceftiofur did not trigger growth extended-spectrum cephalosporin-resistant E. coli in the bovine rectal flora; however, ceftiofur selection in vitro suggested that additional ceftiofur exposure enhanced selection for specific extended-spectrum cephalosporin-resistant ß-lactamase-expressing E. coli clones.

High dissemination of extended-spectrum ß-lactamase-producing Enterobacteriaceae in effluents from wastewater treatment plants.

Water environments play an important role in the dissemination of antibiotic-resistant bacteria among humans, animals and agricultural sources. In order to assess the spread of extended-spectrum ß-lactamase (ESBL)-producing Enterobacteriaceae, we analyzed 279 effluent samples from 21 wastewater treatment plants in Navarra (northern Spain). A total of 185 cefpodoxime-resistant bacteria were isolated on ChromID ESBL agar plates, with high predominance of Escherichia coli among isolated species (73%). ESBL production was determined by different methods, concluding its presence in 86.5% of the isolates by the combination disk test, 75.7% by double-disk synergy test and 73.5% by MicroScan(®) NM37 automated system. PCR and sequencing analysis showed that the predominant ß-lactamases (bla) genes were blaCTx-M (67.4%) followed by blaTEM (47%), blaSHV (17.4%) and blaOxA (8.3%); furthermore, two or more ß-lactamases genes were found in 34.9% of the isolates. The results demonstrate the high prevalence of ESBL-producing Enterobacteriaceae in effluent water from wastewater treatment plants and confirm the need to optimize current disinfection procedures and to improve management of wastewater in an effort to minimize reservoirs of resistant bacteria. Further studies are needed for examining the presence of these bacteria in other environments and for determining the potential dissemination routes of these resistances as well as their impact on human health.