16 mg/L; two of these had given a zone size of 14 mm and one had a zone size of 16 mm. However, all of the 91 isolates had an MIC ≤8 mg/L when determined by Etest and would therefore have been considered as susceptible by this method (see Figure 1b). The control sample E. coli NCTC 10418 produced zone diameters and MICs for Etest and Vitek 2 that were all within the acceptable target range of 18 –31 mm and 2 mg/L, respectively. The results of this study suggest that E. coli resistance to co-amoxiclav is being over-reported by the change in zone diameter breakpoint advocated in the current BSAC guidelines. E. coli is the predominant cause of community and nosoco- mial urinary tract infection (UTI). Co-amoxiclav is often recom- mended as second-line treatment of uncomplicated lower UTIs that are resistant to trimethoprim and nitrofurantoin; the third- line treatment may be a fluoroquinolone. A likely consequence of misreporting false resistance to co-amoxiclav is the unneces- sary prescribing of cephalosporin and/or fluoroquinolone antibio- tics, both of which are associated with an increased risk of Clostridium difficile-associated diarrhoea 3,4 and may also lead to the selection of extended-spectrum b-lactamase-producing coliforms. 5,6 This study highlights the importance of rigorous validation of changes to susceptibility testing guidelines, not least because of the potential adverse effect on efforts to ensure good antibiotic stewardship. Funding This study was carried out as part of our routine work. Transparency declarations None to declare. References 1 BSAC. BSAC Methods for Antimicrobial Susceptibility Testing Version 10.2 May 2011. http://www.bsac.org.uk/Resources/BSAC/Version%20%2010. 2%202011%20final%20May%202011.pdf (21 November 2011, date last accessed). 2 BSAC. Use of Gradient Tests for Determination of MICs by BSAC Methodology. http://www.bsac.org.uk/Resources/BSAC/Use%20of% 20gradient%20tests.pdf (21 November 2011, date last accessed). 3 Talpaert MJ, Gopal Rao G, Cooper BS et al. Impact of guidelines and enhanced antibiotic stewardship on reducing broad-spectrum antibiotic usage and its effect on incidence of Clostridium difficile infection. J Antimicrob Chemother 2011; 66: 2168–74. 4 Owens RC, Donskey CJ, Gaynes RP et al. Antimicrobial-associated risk factors for Clostridium difficile infection. Clin Infect Dis 2008; 46 Suppl 1: S19–31. 5 Troughton JA, Millar G, Smyth ET et al. Ciprofloxacin use and susceptibility of Gram-negative organisms to quinolone and non-quinolone antibiotics. J Antimicrob Chemother 2011; 66: 2152–8. 6 Van der Starre WE, van Nieuwkoop C, Paltansing S et al. Risk factors for fluoroquinolone-resistant Escherichia coli in adults with community-onset febrile urinary tract infection. J Antimicrob Chemother 2011; 66: 650–6. J Antimicrob Chemother 2012 doi:10.1093/jac/dks053 Advance Access publication 14 February 2012 Use of therapeutic drug monitoring to treat Elizabethkingia meningoseptica meningitis and bacteraemia in an adult Elizabeth A. Neuner 1 *, Christine L. Ahrens 1 , Joseph J. Groszek 2 , Carlos Isada 3 , Michael A. Vogelbaum 4 , William H. Fissell 5 and Adarsh Bhimraj 3 1 Department of Pharmacy, Cleveland Clinic, 9500 Euclid Avenue, Hb105, Cleveland, OH 44195, USA; 2 Department of Biomedical Engineering, Cleveland Clinic, 9500 Euclid Avenue, ND20, Cleveland, OH 44195, USA; 3 Department of Infectious Disease, Cleveland Clinic, 9500 Euclid Avenue, G21, Cleveland, OH 44195, USA; 4 Brain Tumor and Neuro-Oncology Center, Cleveland Clinic, 9500 Euclid Avenue, ND40, Cleveland, OH 44195, USA; 5 Department of Nephrology and Hypertension, Glickman Urological and Kidney Institute, Cleveland Clinic, 9500 Euclid Avenue, Q7, Cleveland, OH 44195, USA *Corresponding author. E-mail: neunere@ccf.org Keywords: pharmacokinetics, central nervous system, cerebral spinal fluid penetration Sir, Elizabethkingia meningoseptica, formerly Chryseobacterium meningosepticum, is a non-fermentative Gram-negative bacterium and rare cause of nosocomial meningitis in adults. 1,2 Selection of appropriate therapy is difficult due to inherent resistance. We report a case of E. meningoseptica meningitis and bacteraemia in which therapeutic drug monitoring (TDM) allowed optimization of pharmacokinetic and pharmacodynamic targets and microbiological cure. A 73-year-old patient, previously treated with craniofacial irradiation for nasopharyngeal carcinoma, had a progressive decline in cognitive function and magnetic resonance imaging showed radiation-induced encephalomalacia with a new large right frontal cyst with mass effect in the right frontal lobe. The patient was admitted for open fenestration of the intracranial cyst. Dexamethasone was initiated post-craniotomy as standard of care for reduction of swelling. On post-operative day (POD) 3 the patient developed lethargy, fever and neck stiffness. The patient underwent a lumbar punc- ture, which showed cerebral spinal fluid (CSF) pleocytosis (1572 cells/mm 3 ) with neutrophilic predominance (87%), increased protein (253 mg/dL) and slight hypoglycorrhachia (54 mg/dL). Gram staining of CSF and blood revealed Gram- negative bacteria. The patient developed septic shock and empir- ical meropenem was initiated. The use of norepinephrine was required intermittently for 48 h for blood pressure support but the patient never suffered any renal or hepatic impairment. On POD 6 the organism was identified as E. meningoseptica. Because of clinical deterioration, antibiotics were empirically switched to piperacillin/tazobactam, rifampicin and vancomycin. Blood cultures from POD 6 also grew E. meningoseptica. The Research letters 1558