Kegg Pathway: Clavulanic acid biosynthesis

Biochemistry. 2009 Oct 20; 48(41): 9912-20
Kalp M, Bethel CR, Bonomo RA, Carey PR

Extended-spectrum beta-lactamases (ESBLs) are derivatives of enzymes such as SHV-1 and TEM-1 that have undergone site-specific mutations that enable them to hydrolyze, and thus inactivate, oxyimino-cephalosporins, such as cefotaxime and ceftazidime. X-ray crystallographic data provide an explanation for this in that the mutations bring about an expansion of the binding pocket by moving a beta-strand that forms part of the active site wall. Another characteristic of ESBLs that has remained enigmatic is the fact that they are "hypersusceptible" to inhibition by the mechanism-based inactivators tazobactam, sulbactam, and Clavulanic acid. Here, we provide a rationale for this "hypersusceptibility" based on a comparative analysis of the intermediates formed by these compounds with wild-type (WT) SHV-1 beta-lactamase and its ESBL variants SHV-2 and SHV-5, which carry the G238S and G238S/E240K substitutions, respectively. A Raman spectroscopic analysis of the reactions in single crystals shows that, compared to WT, the SHV-2 and SHV-5 variants have relatively higher populations of the stable trans-enamine intermediate over the less stable and more easily hydrolyzable cis-enamine and imine co-intermediates. In solution, SHV-2 and SHV-5 also form larger populations of an enamine species compared to SHV-1 as detected by stopped-flow kinetic experiments under single-turnover conditions. Moreover, a simple Raman band shape analysis predicts that the trans-enamine intermediates themselves in SHV-2 and SHV-5 are held in more stable, rigid conformations compared to their trans-enamine analogues in WT SHV-1. As a result of this stabilization, more of the trans-enamine intermediate is formed, which subsequently lowers the K(I) values of the mechanism-based inhibitors up to 50-fold in SHV-2 and SHV-5.

Pak J Biol Sci. 2009 May 1; 12(9): 712-6
Karou SD, Ilboudo IP, Nadembega WM, Ameyapoh Y, Ouermi D, Pignatelli S, Pietra V, Traore AS, de Souza C, Simpore J

The present study aimed to ascertain for the current situation of antimicrobial resistance of major urinary tract bacteria in Saint Camille Medical Centre. During two consecutive years, 794 urine specimens were analyzed for microorganism isolation and identification. The microorganisms were identified by conventional methods used in the centre and antimicrobial assays were performed by the NCCLS agar disk diffusion. Pathogenic microorganism's isolation was attempted for 89.04% samples. Escherichia coli (32.76%) was the most frequently isolated microorganism followed by Staphylococcus aureus (22.74%) and Klebsiella pneumoniae (10.45%). The antimicrobial screenings revealed very high antimicrobial resistance, to beta-lactams. The resistance rates recorded with E. coli were 76.64, 74.01, 25 and 74.34% for ampicillin, amoxicillin amoxicillin/Clavulanic acid and trimethoprime-sulfamethoxazole, respectively. Microorganisms were still susceptible to quinolones however, attention should be paid, because, the resistance rate already reached 10% for nalidixic acid and ciprofloxacin. Periodic performance of prevalence studies is a useful tool to know the current situation of microorganisms and their resistance patterns in an institution and it helps to access the emergence and the spread of antibiotic resistance.

J Gen Appl Microbiol. 2009 Jun; 55(3): 207-16
Cheng J, Wang Q, Chen Y, Ye Y, Li H, Li X, Li JB

This study reports phenotypic and molecular characterization of a novel CTX-M beta-lactamase carried by two Klebsiella pneumoniae isolates collected from two hospitals in China. Conjugation experiment, Southern hybridization, susceptibility testing, isoelectric focusing, PCR, and sequencing techniques as well as clone, expression, purification and kinetics were carried out to describe the characterization of the novel CTX-M-type enzyme. The analyses of plasmid profiling and pulsed-field gel electrophoresis of the novel enzyme were performed to investigate epidemiology. The PCR products had 967 nucleotides and a novel CTX-M enzyme with a pI of 8.5 was implicated in this resistance: CTX-M-72. Two strains exhibited a Clavulanic acid-inhibited substrate profile that included extended-spectrum cephalosporins. The amino acid sequence of the CTX-M-72 beta-lactamase differed from that of the CTX-M-3 beta-lactamase by the Arg-->Gly change at position 164. The novel enzyme was susceptible to ceftazidime, the same response being observed for other CTX-M enzymes. The substrates of the beta-lactamase were also characterized. Furthermore, two resistant genes of clinical strains were closely related. The emergence of a novel CTX-M-type extended-spectrum beta-lactamase was rarely described in other areas. This study illustrated the importance of molecular surveillance in tracking CTX-M-producing strains in large teaching hospitals, suggested the horizontal transfer of plasmid-borne bla(CTX-M) genes contributed to the dissemination of CTX-M enzymes in hospital environments, and emphasized the need for epidemiological monitoring.

Metab Eng. 2009 Jul-Sep; 11(4-5): 310-8
Xiang SH, Li J, Yin H, Zheng JT, Yang X, Wang HB, Luo JL, Bai H, Yang KQ

A reporter-guided mutant selection (RGMS) method has been developed wherein reporters are used to facilitate selection of target over-expressing mutants. It was applied to improve Clavulanic acid (CA) production in Streptomyces clavuligerus. In a single-reporter design, the transcriptional activator ccaR of CA biosynthesis was chosen as the over-expressing target, and neo (resistance to kanamycin) as the reporter; 51% of the selected mutants produced higher CA titer than the starting strain. To reduce the high false positive rate of single-reporter method, a double-reporter RGMS vector was configured, in which an xylE-neo double-reporter cassette was used to monitor ccaR expression; 90% of mutants selected by the modified method showed improvement in CA titer. Double-reporter RGMS is the most efficient tool for mutant selection reported to date and is also an alternative method for target over-expression. The mutants obtained by RGMS showed great genetic diversity that could be further exploited in inverse metabolic engineering.

J Infect. 2009 Aug; 59(2): 95-103
Ko WC, Hsueh PR

OBJECTIVES: The Study for Monitoring Antimicrobial Resistance Trends (SMART) was intended to reveal the evolving profiles of antimicrobial resistance among Gram-negative pathogens causing intra-abdominal infections (IAIs). METHODS: Aerobic and facultatively anaerobic Gram-negative isolates were prospectively collected from patients with IAIs in the Asia/Pacific region between 2002 and 2006. Only clinically significant isolates were included for susceptibility tests by the microdilution method. Phenotypic identification of extended-spectrum beta-lactamase (ESBL) production was performed on Escherichia coli, Klebsiella spp. and Enterobacter spp., with the measurements of MICs of cefepime alone and in the presence of Clavulanic acid. RESULTS: Of 7239 Gram-negative isolates, Enterobacteriaceae accounted for the majority (81.5%), and the three major species were E. coli (42.5%), Klebsiella pneumoniae (15.7%) and Pseudomonas aeruginosa (9.6%). The susceptibility rates of Enterobacteriaceae isolates to cephalosporins decreased, in parallel with the fact that the prevalence of ESBLs increased from 13% in 2002 to 28% in 2006. Among E. coli isolates, the proportion of isolates producing an ESBL varied greatly between countries, ranging from 38.6% in China to 1.2% in New Zealand, and ciprofloxacin susceptibility rate from 41.6% in China to 95.8% in New Zealand. Carbapenems and amikacin were in vitro active against more than 95% of Enterobacteriaceae isolates. CONCLUSIONS: Antimicrobial resistance was frequently present among Gram-negative isolates from IAIs in the Asia/Pacific region. During the study period, there were increasing resistant rates of E. coli isolates to cephalosporins, but wide variations existed among countries. Regular updates of treatment guidelines for this region are necessary for empiric antimicrobial therapy.

Chemotherapy. 2009; 55(4): 293-7
Koksal F, Ak K, Kucukbasmaci O, Samasti M

Between January 2001 and September 2006, a total of 459 Escherichia coli and 226 Klebsiella pneumoniae strains were isolated from blood samples of patients with bacteremia who were hospitalized at the Istanbul University Cerrahpasa Medical Faculty. Blood cultures were analyzed with the Bactec 9120 system (Becton Dickinson, USA). Antimicrobic resistance of the E. coli or K. pneumoniae strains was determined by the disk diffusion method according to the Clinical and Laboratory Standards Institute criteria. Extended spectrum beta-lactamase (ESBL) production was examined with the double-disk synergy test. The percentage of ESBL was 40% (182/459) for E. coli and 49% (111/226) for K. pneumoniae. ESBL-producing E. coli and K. pneumoniae were highly resistant to trimethoprim/sulfamethoxazole (60 and 40.5%), amoxicillin/Clavulanic acid (56.5 and 48.6%), ciprofloxacin (57.6 and 35%) and gentamicin (38 and 40.5%), respectively; however, lower resistance rates were found for amikacin (19.7 and 16%) and piperacillin/tazobactam (29.6 and 24%). None of the strains were resistant to imipenem. Our data indicated that prevalence of ESBL-producing E. coli and K. pneumoniae strains isolated from blood cultures is high and antimicrobial resistance increases. Considerable effort should be made to decrease the ESBL-positive organisms.

Antimicrob Agents Chemother. 2009 Aug; 53(8): 3357-64
Griggs DJ, Peake L, Johnson MM, Ghori S, Mott A, Piddock LJ

Fifty-two percent of 1,288 poultry isolates of campylobacters were ampicillin resistant, and resistance was more common among Campylobacter coli isolates (67.4%) than among Campylobacter jejuni isolates (47.5%). Production of beta-lactamase was typically associated with resistance to ampicillin, amoxicillin (amoxicilline), penicillin, and ticarcillin. Regardless of beta-lactamase production, all isolates were resistant to piperacillin (MICs >or= 256 microg/ml), and most were resistant to carbenicillin, cloxacillin, and cephalosporins. Of all ampicillin-resistant campylobacters tested, 91% (347/380) carried the bla(OXA-61) gene, and 77% (136/175) of those tested with nitrocefin produced a beta-lactamase, presumably OXA-61. The isoelectric point (pI) of OXA-61 was 8.7, and the molecular mass was 31.0 kDa. Insertional inactivation of bla(OXA-61) in C. jejuni NCTC 11168 and two ampicillin-resistant isolates resulted in increased susceptibility to ampicillin, co-amoxiclav (amoxicillin and Clavulanic acid), penicillin, carbenicillin, oxacillin, and piperacillin, but the effects on MICs of cephalosporins and imipenem were negligible. Some C. jejuni isolates that lacked bla(OXA-61) produced a beta-lactamase, CjBla2, with a pI of 9.2 and molecular mass of 32.4 kDa. Mass spectrometry confirmed that the most prevalent beta-lactamase was the product of bla(OXA-61), but CjBla2 was not identified. OXA-61 is prevalent among Campylobacter spp. of veterinary origin and is similar to the beta-lactamase previously reported in human isolates. Production of OXA-61 was associated with resistance to penams but not cephalosporins. Co-amoxiclav remained active against all isolates tested.

Assay Drug Dev Technol. 2009 Apr; 7(2): 170-9
Sanchez PA, Toney JH, Thomas JD, Berger JM

Antibiotic-resistant bacteria continue to threaten human health through multiple mechanisms, including hydrolytic inactivation of beta-lactam antibiotics by metallo-beta-lactamases (MBLs). The SPM-1 enzyme, originally identified from a Pseudomonas aeruginosa clinical isolate, is a Class B beta-lactamase responsible for resistance in bacteria against antibiotics such as penicillins, cephalosporins, and carbapenems. Unlike Class A, C, and D beta-lactamases, which employ a serine residue in their active site, Class B enzymes possess one or two Zn atoms in the active site that play both a structural and catalytic role. A beta-lactamase inhibitor with co-administration of a beta-lactam antibiotic has proven to be an effective treatment against antibiotic-resistant bacteria whose resistance is due to serine-based beta-lactamases (e.g., amoxicillin/Clavulanic acid). A similar clinical approach has not yet been developed for resistant bacteria possessing MBLs. The identification and development of specific and effective MBL inhibitors to combat this resistance could extend the utility of currently prescribed antibiotics such as cephalosporins and carbapenems. To discover MBL inhibitors, compound libraries are screened typically by enzymatic hydrolysis of a chromogenic substrate such as nitrocefin monitored by absorbance. Spectrophotometric assays, while valuable, lack the sensitivity and selectivity to screen natural product extract libraries because of the strongly absorbing nature of some extracts and the dilute concentrations of active components. An assay is described herein that monitors the SPM-1-catalyzed hydrolysis of penicillin G by high-performance (high-pressure) liquid chromatography-electrospray mass spectroscopy, which permits investigations with greater sensitivity and selectivity allowing the screening of natural product extracts for inhibitors of MBLs.

Ann Hepatol. 2009 Apr-Jun; 8(2): 134-40
El-Sherbiny GA, Taye A, Abdel-Raheem IT

Incidence of hepatotoxicity caused by the broad spectrum antibiotic combination amoxicillin-Clavulanic acid (Co-amoxyclav) has been increasingly recognized and the mechanism of this toxicity remains undefined. On the other hand, Ursodeoxycholic acid (UDCA) has been suggested as efficient antioxidant therapy in various liver diseases. Therefore, the present study was designed to elucidate the possible role of oxidative stress in hepatotoxicity induced by Co-amoxyclav and the putative protective role of UDCA in rats. Effects of amoxicillin (Amox; 50 mg/kg, orally, 21 d) or Clavulanic acid (Clav; 10 mg/kg, orally, 21 d) and their combined administration on the biochemical liver parameters, reduced glutathione (GSH), lipid peroxidation measured as hepatic malondialdehyde (MDA) levels. In addition, myeloperoxidase (MPO) activity and reactive oxygen species (ROS) production in liver homogenate were also evaluated. On the other hand, the protective effects of pretreatment with UDCA (20 mg/kg, orally, 21 d) on these parameters were also evaluated. Our results show that pretreatment with UDCA reduced the liver parameters that were enhanced by single or combined administration of Amox and/or Clav such as serum activities of alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and serum bilirubin levels. Moreover, pretreatment with UDCA normalized the GSH level and inhibited the elevation in hepatic MDA concentration. The enhanced MPO activity and ROS production in liver homogenate of rats treated with Clav or Co-amoxyclav were also normalized by UDCA pretreatment. In conclusion, the present data suggest that UDCA acts as effective hepatoprotective agent against liver dysfunction caused by Co-amoxyclav and this effect is related to its antioxidant properties.

J Med Microbiol. 2009 Jul; 58(Pt 7): 963-4
Deptuła A, Kruszyńska E, Mikucka A, Gospodarek E, Olszewski K, Kruczyński J, Matewski D

Clostridium difficile is a well-known cause of hospital-acquired infection such as antibiotic associated diarrhoea or pseudomembranous colitis. Extraintestinal infections caused by this pathogen are described rarely. A case of post-traumatic wound infection caused by C. difficile in an immunocompetent, young and otherwise healthy trauma patient is reported. A 31-year-old female, a car accident victim, was admitted to hospital because of polytrauma. After open reduction and internal fixation of a supracondylar femoral fracture by means of the dynamic condylar screw (DCS) system, a purulent fistula occurred. Microbiological examination of the pus revealed C. difficile as the single aetiological factor of this infection. Empirical antibiotic treatment with cefazoline and metronidazole had been administered right after the surgery, but was found to be ineffective. The strain isolated from the patient was sensitive to most antimicrobials except for clindamycin, and amoxicillin/Clavulanic acid was chosen for the guided therapy. Such treatment combined with the removal of the DCS system produced a desirable effect.

Biochem Biophys Res Commun. 2009 Aug 7; 385(4): 512-7
Caines ME, Sorensen JL, Schofield CJ

N(2)-(2-Carboxyethyl)arginine synthase (CEAS), an unusual thiamin diphosphate (ThDP)-dependent enzyme, catalyses the committed step in the biosynthesis of the b-lactamase inhibitor Clavulanic acid in Streptomyces clavuligerus. Crystal structures of tetrameric CEAS-ThDP in complex with the substrate analogues 5-guanidinovaleric acid (GVA) and tartrate, and a structure reflecting a possible enol(ate)-ThDP reaction intermediate are described. The structures suggest overlapping binding sites for the substrates D-glyceraldehyde-3-phosphate (D-G3P) and L-arginine, and are consistent with the proposed CEAS mechanism in which D-G3P binds at the active site and reacts to form an alpha,beta-unsaturated intermediate,which subsequently undergoes (1,4)-Michael addition with the alpha-amino group of L-arginine. Additional solution studies are presented which probe the amino acid substrate tolerance of CEAS, providing further insight into the L-arginine binding site. These findings may facilitate the engineering of CEAS towards the synthesis of alternative beta-amino acid products.

ChemMedChem. 2009 Jul; 4(7): 1051-3
Holzgrabe U

The Great White Plague: Mycobacterium tuberculosis, the bacteria causing tuberculosis, is a continuing threat to global health through the emergence of resistant strains and the lack of novel therapeutic agents. Recently reported results on this important work are highlighted.

Pol J Vet Sci. 2009; 12(1): 9-13
Kizerwetter-Swida M, Chrobak D, Rzewuska M, Binek M

We have evaluated 102 Staphylococcus intermedius isolates of canine origin for susceptibility to antimicrobial primary agents, i.e. penicillin, amoxicillin, amoxicillin with Clavulanic acid, cefuroxime, trimethoprim/sulfonamides, neomycin, streptomycin, gentamicin, norfloxacin, tetracycline, vancomycin, erythromycin and secondary agents, i.e., chloramphenicol, ciprofloxacin, lincomycin, teicoplanin, rifampicin, imipenem, mupirocin. Antimicrobial sensitivity was examined using the disk diffusion method and performed according to NCCLS quidelines. Methicillin resistance was detected using the disk diffusion method with oxacillin, and the occurrence of mecA gene was detected by PCR. Resistance to streptomycin, penicillin, amoxicillin, neomycin, followed by tetracycline was predominant. From 14 mecA-positive strains, 12 were multidrug-resitant, and the remaining two showed atypical susceptibility. One strain resistant to oxacillin in the disc diffusion method was mecA-negative, suggesting a different mechanism of resistance. Our results indicate that the emergence of S. intermedius resistance to methicillin may be underestimated. In case of clinical multidrug-resitant S. intermedius isolates, resistance to methicillin should be considered.

J Med Microbiol. 2009 Jun; 58(Pt 6): 774-8
Fisher MA, Stamper PD, Hujer KM, Love Z, Croft A, Cohen S, Bonomo RA, Carroll KC, Petti CA

Phenotypic identification of AmpC, KPC and extended-spectrum beta-lactamases (ESBLs) among members of the Enterobacteriaceae remains challenging. This study compared the Phoenix Automated Microbiology System (BD Diagnostics) with the Clinical and Laboratory Standards Institute confirmatory method to identify ESBL production among 200 Escherichia coli and Klebsiella pneumoniae clinical isolates. The Phoenix system misclassified nearly half of the isolates as ESBL-positive, requiring manual testing for confirmation. Inclusion of aztreonam +/- Clavulanic acid (CA) and cefpodoxime +/- CA in the testing algorithm increased the ESBL detection rate by 6 %. Boronic acid-based screening identified 24 isolates as AmpC(+), but in a subset of genotypically characterized isolates, appeared to have a high false-positivity rate. PCR screening revealed eight KPC(+) isolates, all of which tested as ESBL(+) or ESBL(+) AmpC(+) by phenotypic methods, but half were reported as carbapenem-susceptible by the Phoenix system. Overall, these results indicate that laboratories should use the Phoenix ESBL results only as an initial screen followed by confirmation with an alternative method.

Biochemistry. 2009 Jun 2; 48(21): 4557-66
Drawz SM, Bethel CR, Hujer KM, Hurless KN, Distler AM, Caselli E, Prati F, Bonomo RA

Inhibitor-resistant class A beta-lactamases of the TEM and SHV families that arise by single amino acid substitutions are a significant threat to the efficacy of beta-lactam/beta-lactamase inhibitor combinations. To better understand the basis of the inhibitor-resistant phenotype in SHV, we performed mutagenesis to examine the role of a second-shell residue, Asn276. Of the 19 variants expressed in Escherichia coli, only the Asn276Asp enzyme demonstrated reduced susceptibility to ampicillin/clavulanate (MIC increased from 50/2 --> 50/8 microg/mL) while maintaining high-level resistance to ampicillin (MIC = 8192 microg/mL). Steady-state kinetic analyses of Asn276Asp revealed slightly diminished k(cat)/K(m) for all substrates tested. In contrast, we observed a 5-fold increase in K(i) for clavulanate (7.4 +/- 0.9 microM for Asn276Asp vs 1.4 +/- 0.2 microM for SHV-1) and a 40% reduction in k(inact)/K(I) (0.013 +/- 0.002 microM(-1 )s(-1) for Asn276Asp vs 0.021 +/- 0.004 microM(-1) s(-1) for SHV-1). Timed electrospray ionization mass spectrometry of clavulanate-inhibited SHV-1 and SHV Asn276Asp showed nearly identical mass adducts, arguing for a similar pathway of inactivation. Molecular modeling shows that novel electrostatic interactions are formed between Arg244Neta2 and both 276AspOdelta1 and Odelta2; these new forces restrict the spatial position of Arg244, a residue important in the recognition of the C(3)/C(4) carboxylate of beta-lactam substrates and inhibitors. Testing the functional consequences of this interaction, we noted considerable free energy costs (+DeltaDeltaG) for substrates and inhibitors. A rigid carbapenem (meropenem) was most affected by the Asn276Asp substitution (46-fold increase in K(i) vs SHV-1). We conclude that residue 276 is an important second-shell residue in class A beta-lactamase-mediated resistance to substrates and inhibitors, and only Asn is able to precisely modulate the conformational flexibility of Arg244 required for successful evolution in nature.

Southeast Asian J Trop Med Public Health. 2009 Jan; 40(1): 131-9
Rawat D, Hasan AS, Capoor MR, Sarma S, Nair D, Deb M, Pillai P, Aggarwal P

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.

Rev Esp Quimioter. 2009 Mar; 22(1): 25-9
Hernández MS, García JA, Muñoz JL

In vitro activity of fosfomycin, compared with other antibiotics used for urinary tract infections (UTI), against extended spectrum beta-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae clinical isolates obtained from UTIs, was determined. The activity of fosfomycin, co-trimoxazole, ciprofloxacin, nitrofurantoin, amoxicillin/Clavulanic acid and gentamicin against 71 ESBL-producing E. coli clinical isolates and 13 ESBL-producing K. pneumoniae clinical isolates obtained from UTI was studied by the agar-dilution method or E-test. E. coli isolates produced mainly CTX-M type ESBL (76.1%), especially CTX-M 14 (56.3%). K. pneumoniae isolates produced most predominantly SHV-type ESBL (92.3%), mainly SHV-2 (76.9%). Gentamicin (4.4%), fosfomycin (5.6%) and nitrofurantoin (5.6%) showed the lowest resistance proportions against E. coli. Co-trimoxazole and ciprofloxacin (7.7%) showed the lowest resistance proportions against K. pneumoniae.

Curr Opin Allergy Clin Immunol. 2009 Apr; 9(2): 151-3
Pawankar R, Zernotti ME

PURPOSE OF REVIEW: Rhinosinusitis is a common condition in children. The association between rhinosinusitis and asthma is supported by strong epidemiological and pathogenic evidence. Moreover, a close relationship between sinusitis and asthma severity has also been reported. This study shows the new findings in this strong relationship. RECENT FINDINGS: The profile of inflammatory cells and inflammatory mediators seen in both conditions bears considerable similarity, especially in both diseases with a relevant role played by eosinophils. SUMMARY: Severe asthma is uncommon in childhood, but there is compelling evidence showing that the most severe asthma is closely associated to upper respiratory illness, especially rhinosinusitis. Treatment of chronic rhinosinusitis, medical or surgical or both, benefits concomitant asthma and has been shown to reduce the severity of asthma.

Antimicrob Agents Chemother. 2009 Jun; 53(6): 2569-78
Landersdorfer CB, Kinzig M, Bulitta JB, Hennig FF, Holzgrabe U, Sörgel F, Gusinde J

Amoxicillin (amoxicilline)-Clavulanic acid has promising activity against pathogens that cause bone infections. We present the first evaluation of the bone penetration of a beta-lactam by population pharmacokinetics and pharmacodynamic profiling via Monte Carlo simulations. Twenty uninfected patients undergoing total hip replacement received a single intravenous infusion of 2,000 mg/200 mg amoxicillin-Clavulanic acid before surgery. Blood and bone specimens were collected. Bone samples were pulverized under liquid nitrogen with a cryogenic mill, including an internal standard. The drug concentrations in serum and total bone were analyzed by liquid chromatography-tandem mass spectrometry. We used NONMEM and S-ADAPT for population pharmacokinetic analysis and a target time of the non-protein-bound drug concentration above the MIC for > or = 50% of the dosing interval for near-maximal bactericidal activity in serum. The median of the ratio of the area under the curve (AUC) for bone/AUC for serum was 20% (10th to 90th percentile for between-subject variability [variability], 16 to 25%) in cortical bone and 18% (variability, 11 to 29%) in cancellous bone for amoxicillin and 15% (variability, 11 to 21%) in cortical bone and 10% (variability, 5.1 to 21%) in cancellous bone for Clavulanic acid. Analysis in S-ADAPT yielded similar results. The equilibration half-lives between serum and bone were 12 min for amoxicillin and 14 min for Clavulanic acid. For a 30-min infusion of 2,000 mg/200 mg amoxicillin-Clavulanic acid every 4 h, amoxicillin achieved robust (> or = 90%) probabilities of target attainment (PTAs) for MICs of < or = 12 mg/liter in serum and 2 to 3 mg/liter in bone and population PTAs above 95% against methicillin-susceptible Staphylococcus aureus in bone and serum. The AUC of amoxicillin-Clavulanic acid was 5 to 10 times lower in bone than in serum, and amoxicillin-Clavulanic acid achieved a rapid equilibrium and favorable population PTAs against pathogens commonly encountered in bone infections.

J Vet Pharmacol Ther. 2009 Apr; 32(2): 137-45
Gasthuys F, De Boever S, Schauvliege S, Reyns T, Levet T, Cornillie P, Casteleyn C, De Backer P, Croubels S

The reliability of a silicone double-lumen catheter implanted into the external jugular vein and tunnelled towards the neck region was investigated in eight pigs. Surgery was uneventful without interference with the normal homoeostasis during 8 days. After injection of amoxicillin/Clavulanic acid through the distal port of the catheter, analysis of drug components in the simultaneous blood samples obtained by the proximal port and a Venoject system were comparable in one pig. Histological control of the catheterized jugular veins pointed to an acceptable tissue reaction while bacteriological examination of the tip of the catheters was negative in only three animals. A moulding of the intestinal veins was made in a pig cadaver to determine the optimal length of insertion of a silicone portal catheter from the splenic vein towards the portal vein. Surgery was straightforward in four pigs whereby the catheter was exteriorized towards the back region. No complications were encountered during and after surgery for 9 days. The technique of a double-lumen catheter placed into the jugular vein and a transsplenic portal catheter is a useful tool for the study of the pharmacokinetics and also the first-pass effect of drugs in experimental pigs.