Comprehensive stability analysis of 13 ß-lactams and ß-lactamase inhibitors in in vitro media, and novel supplement dosing strategy to mitigate thermal drug degradation.

Non-clinical antibiotic development relies on in vitro susceptibility and infection model studies. Validating the achievement of the targeted drug concentrations is essential to avoid under-estimation of drug effects and over-estimation of resistance emergence. While certain ß-lactams (e.g., imipenem) and ß-lactamase inhibitors (BLIs; clavulanic acid) are believed to be relatively unstable, limited tangible data on their stability in commonly used in vitro media are known. We aimed to determine the thermal stability of 10 ß-lactams and 3 BLIs via LC-MS/MS in cation-adjusted Mueller Hinton broth at 25 and 36°C as well as agar at 4 and 37°C, and in water at -20, 4, and 25°C. Supplement dosing algorithms were developed to achieve broth concentrations close to their target over 24 h. During incubation in broth (pH 7.25)/agar, degradation half-lives were 16.9/21.8 h for imipenem, 20.7/31.6 h for biapenem, 29.0 h for clavulanic acid (studied in broth only), 23.1/71.6 h for cefsulodin, 40.6/57.9 h for doripenem, 46.5/64.6 h for meropenem, 50.8/97.7 h for cefepime, 61.5/99.5 h for piperacillin, and >120 h for all other compounds. Broth stability decreased at higher pH. All drugs were ≥90% stable for 72 h in agar at 4°C. Degradation half-lives in water at 25°C were >200 h for all drugs except imipenem (14.7 h, at 1,000 mg/L) and doripenem (59.5 h). One imipenem supplement dose allowed concentrations to stay within ±31% of their target concentration. This study provides comprehensive stability data on ß-lactams and BLIs in relevant in vitro media using LC-MS/MS. Future studies are warranted applying these data to antimicrobial susceptibility testing and assessing the impact of ß-lactamase-related degradation.

Breaking Antimicrobial Resistance: High-Dose Amoxicillin with Clavulanic Acid for Urinary Tract Infections Due to Extended-Spectrum Beta-Lactamase (ESBL)-Producing Klebsiella pneumoniae.

BACKGROUND Carbapenems are the primary treatment for urinary tract infections (UTIs) caused by extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae. However, the recurrence rate is high, and patients often require rehospitalization. We present the results of an observational study on patients with recurrent UTIs who were treated in an outpatient setting with maximal therapeutic oral doses of amoxicillin with clavulanic acid. MATERIAL AND METHODS All patients had pyuria and ESBL-producing K. pneumoniae in urine culture. The starting dosage was 2875 g of amoxicillin twice daily and 125 mg of clavulanic acid twice daily. We down-titrated the doses every 7-14 days and continued prophylactic therapy with amoxicillin/clavulanic acid at 250/125 mg for up to 3 months. We defined therapeutic failure as ESBL-positive K. pneumoniae in urine culture during therapy and recurrence as positive urine culture with the same strain within 1 month after the end of treatment. RESULTS We included 9 patients: 7 kidney graft recipients, 1 liver graft recipient, and 1 patient with chronic kidney disease. We observed no therapeutic failures and no recurrences in the study group during the study period. In 1 case, the patient experienced a subsequent UTI caused by ESBL-producing K. pneumoniae 4 months after completing the therapy. CONCLUSIONS In conclusion, it is possible to break the resistance of ESBL-producing K. pneumoniae strains with high doses of oral amoxicillin with clavulanic acid. Such treatment could be an alternative to carbapenems in select cases.

Triple oral beta-lactam containing therapy for Buruli ulcer treatment shortening.

The potential use of clinically approved beta-lactams for Buruli ulcer (BU) treatment was investigated with representative classes analyzed in vitro for activity against Mycobacterium ulcerans. Beta-lactams tested were effective alone and displayed a strong synergistic profile in combination with antibiotics currently used to treat BU, i.e. rifampicin and clarithromycin; this activity was further potentiated in the presence of the beta-lactamase inhibitor clavulanate. In addition, quadruple combinations of rifampicin, clarithromycin, clavulanate and beta-lactams resulted in multiplicative reductions in their minimal inhibitory concentration (MIC) values. The MIC of amoxicillin against a panel of clinical isolates decreased more than 200-fold within this quadruple combination. Amoxicillin/clavulanate formulations are readily available with clinical pedigree, low toxicity, and orally and pediatric available; thus, supporting its potential inclusion as a new anti-BU drug in current combination therapies.

Probiotics and infective endocarditis in patients with hereditary hemorrhagic telangiectasia: a clinical case and a review of the literature.

BACKGROUND: In the last decades, probiotics have been widely used as food supplements because of their putative beneficial health effects. They are generally considered safe but rare reports of serious infections caused by bacteria included in the definition of probiotics raise concerns on their potential pathogenic role in patients with particular predisposing factors. Patients with hereditary hemorrhagic telangiectasia (HHT) are exposed to infections because of telangiectasias and arteriovenous malformations (AVMs). We describe what is, to our knowledge, the first case of infective endocarditis (IE) caused by Lactobacillus rhamnosus in a patient with HHT. A systematic review of the relevant medical literature is presented. CASE PRESENTATION: A patient with HHT and an aortic bioprosthesis was admitted because of prolonged fever not responding to antibiotics. The patient had a history of repeated serious infections with hospitalizations and prolonged use of antibiotics, and used to assume large amounts of different commercial products containing probiotics. Weeks before the onset of symptoms the patient had been treated with nasal packings and with surgical closure of a nasal bleeding site because of recurrent epistaxis. A diagnosis of IE of the aortic bioprosthesis was made. All blood coltures were positive for L. rhamnosus. The patients responded to a cycle of 6 weeks of amoxicillin/clavulanate plus gentamicin. A systematic review of IE linked to consumption of probiotics, and of infective endocarditis in patients with HHT was conducted. 10 cases of IE linked to probiotics consumption and 6 cases of IE in patients with HHT were found. CONCLUSIONS: Consumption of probiotics can pose a risk of serious infections in patients with particular predisposing factors. Patients with HHT can be considered at risk because of their predisposition to infections. Prophylaxis with antibiotics before nasal packings in patients with HHT can be considered.

An Improved Extended-Spectrum-ß-Lactamase Detection Test Utilizing Aztreonam plus Clavulanate.

Clinical laboratories test for extended-spectrum ß-lactamases (ESBLs) for epidemiological and infection control purposes and also for the potential of cephalosporins to cause therapeutic failures. Testing can be problematic, because the CLSI does not recommend the testing of all producers of ESBLs and also falsely negative results may occur with isolates that coproduce AmpC. Boronic acid-supplemented tests can enhance ESBL detection in AmpC producers. Because aztreonam inhibits AmpCs, a study was designed to compare ESBL detection by the CLSI disk test (CLSI), a boronic acid-supplemented CLSI disk test (CLSI plus BA), and an aztreonam plus clavulanate disk test (ATM plus CA). The study tested 100 well-characterized Enterobacteriaceae, Acinetobacter baumannii, and Pseudomonas aeruginosa isolates. Seventy produced TEM, SHV, or CTX-M ESBLs, with 15 coproducing an AmpC and 11 coproducing a metallo-ß-lactamase. Thirty ESBL-negative isolates were also tested. Tests were inoculated by CLSI methodology and interpreted as positive if an inhibitor caused a zone diameter increase of ≥5 mm. The percentages of ESBL producers detected were as follows: ATM plus CA, 95.7%; CLSI plus BA, 88.6%; and CLSI, 78.6%. When AmpC was coproduced, the sensitivities of the tests were as follows: ATM plus CA, 100%; CLSI plus BA, 93.3%; and CLSI, 60%. ATM plus CA also detected an ESBL in 90.1% of isolates that coproduced a metallo-ß-lactamase. Falsely positive tests occurred only with the CLSI and CLSI plus BA tests. Overall, the ATM plus CA test detected ESBLs more accurately than the CLSI and CLSI plus BA tests, especially with isolates coproducing an AmpC or metallo-ß-lactamase.

Identification of Mycobacterial Genes Involved in Antibiotic Sensitivity: Implications for the Treatment of Tuberculosis with ß-Lactam-Containing Regimens.

In a Mycobacterium smegmatis mutant library screen, transposon mutants with insertions in fhaA, dprE2, rpsT, and parA displayed hypersusceptibility to antibiotics, including the ß-lactams meropenem, ampicillin, amoxicillin, and cefotaxime. Sub-MIC levels of octoclothepin, a psychotic drug inhibiting ParA, phenocopied the parA insertion and enhanced the bactericidal activity of meropenem against Mycobacterium tuberculosis in combination with clavulanate. Our study identifies novel factors associated with antibiotic resistance, with implications in repurposing ß-lactams for tuberculosis treatment.

Susceptibilities of MDR Mycobacterium tuberculosis isolates to unconventional drugs compared with their reported pharmacokinetic/pharmacodynamic parameters.

Background: The second-line drugs recommended to treat drug-resistant TB are toxic, expensive and difficult to procure. Given increasing resistance, the need for additional anti-TB drugs has become more urgent. But new drugs take time to develop and are expensive. Some commercially available drugs have reported anti-mycobacterial activity but are not routinely used because supporting laboratory and clinical evidence is sparse. Methods: We analysed 217 MDR M. tuberculosis isolates including 153 initial isolates from unique patients and 64 isolates from follow-up specimens during the course of treatment. The resazurin microdilution assay was performed to determine MICs of trimethoprim/sulfamethoxazole, mefloquine, thioridazine, clofazimine, amoxicillin/clavulanate, meropenem/clavulanate, nitazoxanide, linezolid and oxyphenbutazone. Isoniazid was used for validation. We calculated the MIC 50 and MIC 90 as the MICs at which growth of 50% and 90% of isolates was inhibited, respectively. Results: The MIC 50 s, in mg/L, for initial isolates were as follows: trimethoprim/sulfamethoxazole, 0.2/4; mefloquine, 8; thioridazine, 4; clofazimine, 0.25; amoxicillin/clavulanate, 16/8; meropenem/clavulanate, 1/2.5; nitazoxanide, 16; linezolid, 0.25; and oxyphenbutazone, 40. The MIC 90 s, in mg/L, for initial isolates were as follows: trimethoprim/sulfamethoxazole, 0.4/8; mefloquine, 8; thioridazine, 8; clofazimine, 0.5; amoxicillin/clavulanate, 32/16; meropenem/clavulanate, 8/2.5; nitazoxanide, 16; linezolid, 0.25; and oxyphenbutazone, 60. By comparison, the MIC 90 of isoniazid was >4 mg/L, as expected. There was no evidence that previous treatment affected susceptibility to any drug. Conclusions: Most drugs demonstrated efficacy against M. tuberculosis . When these MICs are compared with the published pharmacokinetic/pharmacodynamic profiles of the respective drugs in humans, trimethoprim/sulfamethoxazole, meropenem/clavulanate, linezolid, clofazimine and nitazoxanide appear promising and warrant further clinical investigation.

Synergistic effects of baicalein with cefotaxime against Klebsiella pneumoniae through inhibiting CTX-M-1 gene expression.

BACKGROUND: Generation of extended- spectrum ß- lactamases is one of the major mechanisms by which clinical Klebsiella pneumoniae develop resistance to antibiotics. Combined antibiotics prove to be a relatively effective method of controlling such resistant strains. Some of Chinese herbal active ingredients are known to have synergistic antibacterial effects. This study is aimed to investigate synergistic effects of Chinese herbal active ingredients with cefotaxime on the extended- spectrum ß- lactamase positive strains of Klebsiella pneumoniae, and to analyze mechanism of synergistic action, providing experimental evidence for clinical application of antimicrobial drugs. RESULTS: For total sixteen strains including fifteen strains of cefotaxime resistant K. pneumoniae and one extended- spectrum ß- lactamase positive standard strain, the synergy rates of cefotaxime with baicalein, matrine, and clavulanic acid were 56.3 %, 0 %, and 100 %, respectively. The fractional inhibitory concentration index of combined baicalein and cefotaxime was correlated with the percentage decrease of cefotaxime MIC of all the strains (r = -0.78, p <0.01). In the group of synergy baicalein and cefotaxime, the transcribed mRNA level of CTX-M-1 after treatment of baicalein was decreased significantly (p <0.05). Moreover, the CTX-M-1 mRNA expression percentage inhibition (100 %, 5/5) was significantly higher than non- synergy group (25 %, 1/4) (p <0.05). CONCLUSIONS: Our study demonstrated that baicalein exhibited synergistic activity when combined with cefotaxime against some of extended- spectrum ß- lactamases positive K. pneumoniae strains by inhibiting CTX-M-1 mRNA expression. However, no direct bactericidal or bacteriostatic activity was involved in the synergistic action. Baicalein seems to be a promising novel effective synergistic antimicrobial agent.

Comparative performance of isolation methods using Preston broth, Bolton broth and their modifications for the detection of Campylobacter spp. from naturally contaminated fresh and frozen raw poultry meat.

The performance of different isolation methods was evaluated for the detection of Campylobacter from naturally contaminated raw poultry meat. Therefore, fresh and frozen poultry meat samples were analysed using the standard procedure (ISO 10272-1:2006), enrichment in Preston broth, and enrichment in modified Bolton broth (supplemented with (i) potassium clavulanate (C-BB), (ii) triclosan (T-BB), (iii) polymyxin B (P-BB)). The enrichment cultures were streaked onto both modified charcoal cefoperazone deoxycholate agar (mCCDA) and RAPID'Campylobacter agar (RCA). Moreover, direct plating on mCCDA and RCA was performed to quantify Campylobacter. In total, 33 out of 59 fresh retail meat samples (55.9%) were Campylobacter positive. For both fresh and frozen poultry meat samples, enrichment in Bolton broth (ISO 10272-1:2006) resulted in a higher number of positive samples than enrichment in Preston broth. Supplementation of Bolton broth with potassium clavulanate (C-BB) and triclosan (T-BB) enhanced the Campylobacter recovery from fresh poultry meat compared to non-supplemented Bolton broth, although the use of C-BB was less applicable than T-BB for Campylobacter recovery from frozen samples. Additionally, the use of RCA resulted in a higher isolation rate compared to mCCDA. The present study demonstrates the impact of culture medium on the recovery of Campylobacter from fresh and frozen naturally contaminated poultry meat samples and can support laboratories in choosing the most appropriate culturing method to detect Campylobacter.

First series of patients with XDR and pre-XDR TB treated with regimens that included meropenen-clavulanate in Argentina.

XDR (extensively drug-resistant) and pre-XDR tuberculosis (TB) seriously compromise prognosis and treatment possibilities, and inevitably require the use of group V drugs (World Health Organization). The progress of all patients with XDR and pre-XDR TB seen in a specialized unit during 2012 and 2013 and treated with regimens that included at least 6 months of meropenem-clavulanate (MPC), capreomycin, moxifloxacin, linezolid, clofazimine, high-dose isoniazid, PAS, and bedaquiline in 1 case, were retrospectively analysed. Ten patients were treated, 9 with an extensive pattern of resistance to at least 6 drugs, and 1 because of adverse reactions and drug interactions leading to a similar situation. Eight of the 10 patients treated achieved bacteriological sputum conversion (2 consecutive negative monthly cultures) over a period of 2-7 months, while 2 died. No adverse reactions attributable to prolonged administration of MPC were observed.

Stability, compatibility and microbiological activity studies of meropenem-clavulanate potassium.

Meropenem (MEM) and clavulanate potassium have been reported to demonstrate highly effective activity against Mycobacterium tuberculosis. There have been no reports on research into the complex of these chemotherapeutics concerning their mutually dependent stability or microbiological action on other microorganisms. Stability and compatibility studies of MEM/clavulanate potassium were conducted by using an HPLC-DAD method. The antibacterial activity of MEM/clavulanate potassium was tested in vitro against a selection of indicator bacteria strains by determining the MIC as well as analyzing the kinetics of changes in the concentrations of Pseudomonas aeruginosa, Staphylococcus aureus and Listeria monocytogenes caused by the action of MEM/clavulanate potassium. The stability and compatibility of MEM/clavulanate potassium were examined in aqua pro iniectione, 0.9% NaCl and 5% glucose at room temperature and at 5 °C. The degradation rates of MEM/clavulanate potassium depended on the type of infusion solvent used. Although in aqueous solutions of MEM/clavulanate potassium neither compound showed any mutual impact on the rate of degradation, clavulanate potassium was more labile than MEM. The synergy between these two resulted in a significantly lower value of MIC as compared to the values observed for the individual activity of either compound. The infusion solvent in which compatibility is observed between the components of the mixture MEM/clavulanate potassium is aqua pro iniectione. The complex MEM/clavulanate potassium demonstrates synergic antibacterial activity against P. aeruginosa, S. aureus and L. monocytogenes.

Mechanisms of ß-lactam killing and resistance in the context of Mycobacterium tuberculosis.

ß-Lactams are one of the most useful classes of antibiotics against many common bacterial pathogens. One exception is Mycobacterium tuberculosis. However, with increasing incidence of multidrug-resistant tuberculosis and a need for new agents to treat it, the use of ß-lactams, specifically the combination of carbapenem and clavulanate, is now being revisited. With this attention, comes the need to better understand both the mechanisms of action of ß-lactams against M. tuberculosis as well as possible mechanisms of resistance, within the context of what is known about the ß-lactam action in other bacteria. M. tuberculosis has two major mechanisms of intrinsic resistance: a highly active ß-lactamase and a poorly permeable outer membrane. Within the cell wall, ß-lactams bind several enzymes with differing peptidoglycan-synthetic and -lytic functions. The inhibition of these enzymes may lead to cell death through several mechanisms, involving disruption of the balance of synthetic and lethal activities. Currently, all known means of resistance to the ß-lactams rely on diminishing the proportion of peptidoglycan-synthetic proteins bound and inhibited by ß-lactams, through either exclusion or destruction of the antibiotic, or through replacement or supplementation of target enzymes. In this review, we discuss possible mechanisms for ß-lactam activity in M. tuberculosis and the means by which it may acquire resistance, within the context of what is known in other bacterial species.

Improvement of modified charcoal-cefoperazone-deoxycholate agar by addition of potassium clavulanate for detecting Campylobacter spp. in chicken carcass rinse.

The presence of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli (E. coli) in raw poultry is one of the most common factors that interfere with the isolation of Campylobacter by cefoperazone-based selective agar. The performance of modified charcoal-cefoperazone-deoxycholate agar (mCCDA) was improved by addition of an ESBL inhibitor, potassium clavulanate (0.5 mg/L). The ability of the supplemented medium (C-mCCDA) to detect Campylobacter species from chicken carcass rinse was compared with that of normal mCCDA. The isolation rate using C-mCCDA was significantly (p<0.05) higher compared with that using mCCDA (C-mCCDA, 67 out of 120; mCCDA, 38 out of 120). Furthermore, the selectivity of the C-mCCDA as assessed by comparing the number of contaminated plates (C-mCCDA, 44 out of 120; mCCDA, 110 out of 120) and growth index (C-mCCDA, 1.76; mCCDA, 2.79) of competing flora was also better (p<0.05) than that of mCCDA.

Is there a place for ß-lactams in the treatment of multidrug-resistant/extensively drug-resistant tuberculosis? Synergy between meropenem and amoxicillin/clavulanate.

OBJECTIVES: To: (i) assess if amoxicillin/clavulanate is a useful option for the management of multidrug-resistant/extensively drug-resistant tuberculosis (MDR/XDR-TB); (ii) assess if meropenem/clavulanate is active against Mycobacterium tuberculosis at concentrations achievable in vivo; and (iii) determine whether there was inhibition of meropenem/clavulanate activity in the presence of amoxicillin. METHODS: Twenty-eight M. tuberculosis strains (7 susceptible, 2 monoresistant, 16 MDR and 3 XDR) were included in the study and tested against different concentrations of meropenem, meropenem/clavulanate, amoxicillin/meropenem, amoxicillin/clavulanate and amoxicillin/meropenem/clavulanate using the Bactec 960 MGIT(®) system. RESULTS: All 28 strains were resistant to meropenem at the highest concentration tested (5 mg/L). Although 24 strains were susceptible to amoxicillin/clavulanate, 7 strains were susceptible only to 7.2/2.5 mg/L amoxicillin/clavulanate, 10 strains were susceptible to 3.6/2.5 mg/L amoxicillin/clavulanate, 6 strains were susceptible to 1.8/2.5 mg/L amoxicillin/clavulanate and 1 strain was susceptible to 0.9/2.5 mg/L amoxicillin/clavulanate. Therefore, 4/28 strains (14.29%) were resistant to the highest concentration of amoxicillin tested (7.2 mg/L); all of them were MDR. All of the 11 strains resistant to amoxicillin or susceptible only to 7.2 mg/L amoxicillin increased their susceptibility to amoxicillin/clavulanate after the addition of meropenem. The addition of clavulanate to meropenem reduced the MIC of meropenem by an average of over 1.8 dilutions. CONCLUSIONS: The combination of amoxicillin/clavulanate plus meropenem is active against MDR/XDR-TB in vitro, and this triple therapy could be a useful therapy for MDR/XDR-TB and possibly help to reduce the development of further resistance. The drug susceptibility technique used here is routinely used, with modification, in mycobacteriology laboratories.

Mecillinam/clavulanate combination: a possible option for the treatment of community-acquired uncomplicated urinary tract infections caused by extended-spectrum ß-lactamase-producing Escherichia coli.

BACKGROUND: Extended-spectrum ß-lactamases (ESBLs) have emerged as an important mechanism of ß-lactam resistance among community uropathogens. We characterized the ESBLs of a collection of Escherichia coli isolates recovered from outpatients with urinary tract infection during nationwide surveillance conducted from 2005 to 2006 in Greece, and evaluated the in vitro activity of mecillinam and mecillinam/clavulanate against them. MATERIALS AND METHODS: ESBLs were characterized with PCR and sequencing. In vitro interactions were evaluated with agar dilution with and without clavulanate (4 mg/L) using an inoculum of 10(4) or 10(6) cfu/spot as well as with time-kill methodology. RESULTS: Among 48 ESBL producers, 47 (97.9%) were susceptible to mecillinam. CTX-M-type enzymes were produced by 87.2%, with CTX-M-3 being the most prevalent. SHV enzymes were found in 10.6%, VEB enzymes in 2.1%, TEM enzymes in 19.2% and OXA-type enzymes in 12.8%. Synergy with clavulanate was detected in 60.4% using the agar dilution method and in 43.8% using the time-kill methodology. An inoculum effect was detected in 64.6% of isolates, but this phenomenon was inverted and synergy was evidenced for 85.4% with clavulanate. When a high inoculum was used, 60.4% (29/48) were resistant to mecillinam, but 97.9% (47/48) were susceptible in the presence of clavulanate. CONCLUSIONS: CTX-M-type enzymes were the most prevalent among ESBL-producing E. coli uropathogens in Greece. Mecillinam may be useful in uncomplicated cystitis caused by ESBL producers with low MICs. The addition of the inhibitor could improve and extend the activity of mecillinam, even in the setting of infection with a high bacterial inoculum, and merits clinical evaluation.

Antimicrobial resistance in urinary tract pathogens in Canada from 2007 to 2009: CANWARD surveillance study.

From January 2007 to December 2009, an annual Canadian national surveillance study (CANWARD) tested 2,943 urinary culture pathogens for antimicrobial susceptibilities according to Clinical and Laboratory Standards Institute guidelines. The most frequently isolated urinary pathogens were as follows (number of isolates, percentage of all isolates): Escherichia coli (1,581, 54%), enterococci (410, 14%), Klebsiella pneumoniae (274, 9%), Proteus mirabilis (122, 4%), Pseudomonas aeruginosa (100, 3%), and Staphylococcus aureus (80, 3%). The rates of susceptibility to trimethoprim-sulfamethoxazole (SXT) were 78, 86, 84, and 93%, respectively, for E. coli, K. pneumoniae, P. mirabilis, and S. aureus. The rates of susceptibility to nitrofurantoin were 96, 97, 33, and 100%, respectively, for E. coli, enterococci, K. pneumoniae, and S. aureus. The rates of susceptibility to ciprofloxacin were 81, 40, 86, 81, 66, and 41%, respectively, for E. coli, enterococci, K. pneumoniae, P. mirabilis, P. aeruginosa, and S. aureus. Statistical analysis of resistance rates (resistant plus intermediate isolates) by year for E. coli over the 3-year study period demonstrated that increased resistance rates occurred only for amoxicillin-clavulanate (from 1.8 to 6.6%; P < 0.001) and for SXT (from 18.6 to 24.3%; P = 0.02). For isolates of E. coli, in a multivariate logistic regression model, hospital location was independently associated with resistance to ciprofloxacin (P = 0.026) with higher rates of resistance observed in inpatient areas (medical, surgical, and intensive care unit wards). Increased age was also associated with resistance to ciprofloxacin (P < 0.001) and with resistance to two or more commonly prescribed oral agents (amoxicillin-clavulanate, ciprofloxacin, nitrofurantoin, and SXT) (P = 0.005). We conclude that frequently prescribed empirical agents for urinary tract infections, such as SXT and ciprofloxacin, demonstrate lowered in vitro susceptibilities when tested against recent clinical isolates.

Activity of BAL30376 (monobactam BAL19764 + BAL29880 + clavulanate) versus Gram-negative bacteria with characterized resistance mechanisms.

BACKGROUND: BAL30376 combines the siderophore monobactam BAL19764 (Syn/PTX 2416) with the bridged monobactam BAL29880 to inhibit AmpC enzymes and with clavulanate to inhibit extended-spectrum ß-lactamases (ESBLs). We tested BAL30376 and its components versus isolates and laboratory strains of Enterobacteriaceae and non-fermenters. METHODS: MICs were determined on Mueller-Hinton agar supplemented with 2,2'-bipyridyl to chelate Fe(3+) and induce TonB-mediated uptake. RESULTS: Unprotected BAL19764 had MICs  ≤  1 mg/L for most cephalosporin-susceptible Enterobacteriaceae, but values for a few isolates ranged up to 8 mg/L; its MICs were substantially raised for isolates with AmpC ß-lactamases and ESBLs. Those of BAL30376 were ≤ 1 mg/L for 84% of ESBL producers and ≤ 4 mg/L for 85% of AmpC producers, excluding isolates with exceptional impermeability. Laboratory transformants with metallo- or OXA-48 carbapenemases were susceptible to unprotected BAL19764, but many clinical isolates with these enzymes were resistant, probably having additional mechanisms; BAL30376, by contrast, was active at 4 mg/L versus 31/35 metallo-ß-lactamase producers and 14/19 with OXA-48, although those with KPC carbapenemases were resistant. AmpC-mediated resistance to BAL19764 in Pseudomonas aeruginosa was overcome by BAL30376, as was that due to PER-1 enzyme; but MICs > 16 mg/L were frequent for cystic fibrosis isolates. Many Burkholderia cepacia and carbapenemase-producing Acinetobacter baumannii were susceptible to BAL19764 and BAL30376 at ≤ 4 mg/L, but others were highly resistant, with MICs  ≥  128 mg/L. CONCLUSIONS: BAL30376 overcomes most AmpC-, ESBL- and carbapenemase-mediated resistance in Enterobacteriaceae, though strains with KPC carbapenemases are resistant. It was active against many problem non-fermenters, though resistance was common in P. aeruginosa from cystic fibrosis. Raised MICs for some isolates were independent of ß-lactamase.

Impact of restricted amoxicillin/clavulanic acid use on Escherichia coli resistance--antibiotic DU90% profiles with bacterial resistance rates: a visual presentation.

High use of amoxicillin/clavulanic acid (AMC) at the University Hospital Osijek (Croatia) contributed to high rates of resistance in Enterobacteriaceae, in particular Escherichia coli (50%). Thus, in order to decrease bacterial resistance, AMC use was restricted. We present results of the restriction on resistance amongst antibiotics accounting for 90% of antibiotic use [drug utilisation 90% (DU90%)]. Data were analysed on antibiotic use and microbiological susceptibility of E. coli during two 9-month periods, before and after the restriction of AMC use. Drug use was presented as numbers of defined daily doses (DDDs) and DDDs/100 bed-days. Resistance of E. coli to antibiotics was presented as percentages of isolated strains in the DU90% segment. Use of AMC was 16 DDDs/100 bed-days or 30% of all antibiotics before the intervention. Use of AMC fell to 2 DDDs/100 bed-days or 4% after the intervention, and resistance of E. coli fell from 37% to 11%. In conclusion, restricted use of AMC resulted in a significant decrease of E. coli resistance. DU90% resistance profiles are simple and useful tools in highlighting problems in antibiotic use and resistance but may also be useful in long-term follow-up of antibiotic policy.

In vitro evaluation of a new cefixime-clavulanic acid combination for gram-negative bacteria.

The study was conducted to evaluate a new cefixime-clavulanic acid combination for in vitro susceptibility towards gram-negative bacteria. A total of 220 isolates of Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeroginosa, Acinetobacter spp, Salmonella enterica serovar Typhi and Salmonella enterica serovar Typhimurium were included in the study. The isolates were tested for susceptibility towards the new combination antimicrobial molecule cefixime with clavulanic acid by disk diffusion and Epsilometer strip (E-strip) Minimum Inhibitary Concentration (MIC) method. Of the 101 E. coli and K. pneumoniae isolates, 62.4% were found to be extended spectrum beta-lactamase (ESBL) producers. Almost half of these were from the community and 55.6% were hospital isolates. Of the ESBL isolates, 19% were AmpC (cephalosporinases that are poorly inhibited by beta lactamase inhibitor) producers while the remaining 81% were non AmpC ESBL producers. The AmpC producers were resistant to both cefixime and the combination, while the non-AmpC producers were sensitive to the combination. The addition of clavulanate to cefixime did not improve the sensitivities of P. aeruginosa and Acinetobacter isolates. There were no ESBL isolates among the S. Typhi isolates, all of which were sensitive to cefixime. Of the S. Typhimurium, 88.9% were ESBL producers and all of these were resistant to cefixime but sensitive to the combination. The combination of cefixime with clavulanic acid offers the advantage of oral administration and appears to be a viable option for the treatment of uncomplicated community acquired infections caused by non-AmpC ESBL producing gram-negative bacteria.