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Annual Update in Intensive Care and Emergency Medicine 2011

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activity of BAL 30376 aga<strong>in</strong>st various Gram-negative bacteria. MICs were<br />

observed <strong>in</strong> a range of e 0.06–4 mg/l, <strong>in</strong>clud<strong>in</strong>g most carbapenem-resistant<br />

stra<strong>in</strong>s. Higher MICs were observed for a few stra<strong>in</strong>s of Ac<strong>in</strong>etobacter spp., Enterobacter<br />

spp. <strong>and</strong> P. aerug<strong>in</strong>osa.<br />

Tricyclic carbapenem <strong>in</strong>hibitors<br />

LK-157 is a tricyclic carbapenem <strong>in</strong>hibitor of ser<strong>in</strong>e β-lactamases [24]. LK-157<br />

decreased the MICs of aztreonam, ceftazidime, <strong>and</strong> cefuroxime for B. fragilis <strong>and</strong><br />

awiderangeofβ-lactamases-produc<strong>in</strong>g Enterobacteriaceae members. However,<br />

LK-157 did not affect the MICs of aztreonam, ceftazidime or cefuroxime aga<strong>in</strong>st<br />

CTX-M produc<strong>in</strong>g members of Enterobacteriaceae [24].<br />

Oxapenems<br />

Four β-lactamase <strong>in</strong>hibitors, members of the oxapenems, are be<strong>in</strong>g developed<br />

(AM-112 – AM-115) <strong>and</strong> express activity aga<strong>in</strong>st class A, C, <strong>and</strong> D enzymes [30].<br />

AM-114 <strong>and</strong> AM-115 displayed the most potent activity aga<strong>in</strong>st class A enzymes,<br />

comparable to that of clavulanic acid. Activity aga<strong>in</strong>st class C <strong>and</strong> class D<br />

enzymes was similar to that of AM-112 <strong>and</strong> AM-113 <strong>and</strong> was superior to that of<br />

clavulanic acid. A synergistic activity of ceftazidime with the oxapenems was<br />

demonstrated aga<strong>in</strong>st SHV- <strong>and</strong> TEM-produc<strong>in</strong>g E. coli. Enhancedactivityof<br />

oxapenems <strong>in</strong> comb<strong>in</strong>ation with ceftazidime was also noted aga<strong>in</strong>st Pseudomonas<br />

stra<strong>in</strong>s <strong>and</strong> MRSA [31].<br />

Inhibitors with no �-lactam Structure<br />

NXL104<br />

NXL104 is a non-β-lactam compound which <strong>in</strong>hibits β-lactamases through the<br />

formation of a stable covalent carbamoyl l<strong>in</strong>kage. In comb<strong>in</strong>ation with ceftazidime<br />

<strong>and</strong> cefotaxime aga<strong>in</strong>st Enetrobacteriaceae produc<strong>in</strong>g CTX-M ESBLs, it<br />

showed a 4 to 8000-fold potentiation of the cephalospor<strong>in</strong>s, with MIC values e 1<br />

for all organisms irrespective of CTX-M type [24]. Aga<strong>in</strong>st P99, NXL104 showed<br />

a stronger <strong>in</strong>hibition than tazobactam, whereas clavulanic acid was <strong>in</strong>active.<br />

Another study showed that comb<strong>in</strong>ation with NXL104 restored the activity of ceftazidime<br />

<strong>and</strong> cefotaxime aga<strong>in</strong>st isolates produc<strong>in</strong>g class A carbapenemases [24].<br />

NXL104/ceftazidime comb<strong>in</strong>ation is currently undergo<strong>in</strong>g Phase II cl<strong>in</strong>ical trials<br />

<strong>in</strong> patients admitted for complicated <strong>in</strong>tra-abdom<strong>in</strong>al <strong>and</strong> complicated ur<strong>in</strong>ary<br />

tract <strong>in</strong>fections [32].<br />

Maleic acid derivates<br />

ME1071, previously known as CP3242, is a metallo β-lactamase <strong>in</strong>hibitor that<br />

competitively <strong>in</strong>hibits IMP-1 <strong>and</strong> VIM-2. It significantly lowered the MICs of biapenem<br />

<strong>in</strong> a concentration-dependent manner aga<strong>in</strong>st MBL-produc<strong>in</strong>g P. aerug<strong>in</strong>osa.<br />

MIC lower<strong>in</strong>g by ME1071 was also shown for IMP- or VIM-produc<strong>in</strong>g E.<br />

coli, S. marcescens, A. baumanii <strong>and</strong> K. pneumoniae [24].<br />

New Cephalospor<strong>in</strong>s<br />

New Treatment Options aga<strong>in</strong>st Gram-negative Organisms 507<br />

New cephalospor<strong>in</strong>s are very resistant to penicill<strong>in</strong>ases <strong>and</strong> two of them have<br />

demonstrated anti-methicill<strong>in</strong> resistant S. aureus (MRSA) activity <strong>in</strong> animal mod-<br />

XII

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