due to gram-negative bacilli.
The resistance of the Enterobacteriaceae to carbapenems is generally rare but may be mediated by the combination of outer membrane protein deficiency coupled with the production of beta-lactamases. Rates of resistance to Ertapenem are generally higher than to Imipenem or Meropenem. In view of the comments above, serious infections due to the Enterobacteriaceae family should be managed with a beta-lactam or quinolone antibiotic, which is active in vitro against the infecting organism. An important caveat is that ESBL-producing organisms may appear susceptible to third-generation cephalosporins (Ceftazidime, Cefotaxime, or Ceftriaxone) or Cefepime, yet be functionally resistant to these agents (Paterson H, D.L. Ko, W.
C. Von Gottberg, A. et al., 2001) high clinical failure rates are observed when Cephalosporins are used to treat bacteremia or pneumonia due to ESBL-producing Klebsiella species or, more rarely, ESBL-producing. Carbapenems (imipenem or meropenem) are the antibiotics of choice for serious infections due to ESBL producers (Paterson, D.L., 2000). Polymyxins or tigecycline may be used for infections that are resistant to carbapenems.
A second important finding to reemphasize is that third-generation cephalosporins are associated with a significant risk for relapse of infection when used to treat AmpC-producing organisms, such as Enterobacter species. Again, carbapenems or quinolones are the most reliable agents against Enterobacter species, Serratia species, or Citrobacter species. There is no evidence that combination therapy improves outcome or reduces the advent of resistance of the Enterobacteriaceae family (Chow, J.W. Fine, M.J.
Shlaes, D.M. et al., 1991).Metronidazole is available as tablets (200, 400 mg) 2.8.2 ESBL (Extended Spectrum Beta-Lactamase)Spectrum? Good effect against Enterobacteriaceae (E.
coli, Klebsiella, Enterobacter), excellent effect against Enterococci.2.8.3 Resistance to ?-lactamases Certain bacteria produce drug-destroying ?-lactamases (penicillinases), which, upon coming in contact with the ?-lactam ring that is common to all penicillins, open it and terminate the antibacterial activity.2.8.
4 Plasmid-Mediated ?-lactam Resistance ESBL-producing Enterobacteriaceae–molecular features and dissemination After the first description of ESBLs in Germany in 1983 (Knothe, H., et al., 1983) a large number of plasmid-mediated ?-lactamases has been detected. Several different schemes have been used for the classification of ?-lactamases. The classification proposed by Giske et al. in 2009 (Giske, C.
G., et al., 2009) is the most frequently used in Sweden and Norway. Class of ESBL Ambler class Enzymes Phenotypic test Areas of endemicity 109-111 ESBLA A CTX-M, TEM/SHV-ESBL Inhibited by clavulanic acid Worldwide ESBLM C Plasmid-AmpC, mostly CMY Inhibited by cloxacillin A KPC Synergy with boronic acid Greece, Italy, Israel, Northern America, China ESBLCARBA B NDM, IMP Synergy with EDTA Indian subcontinent, the Balkans, the Middle East VIM Greece D OXA-48 None available, temocillin R Northern Africa, the Middle East Table 2: Classification of ESBL enzymes and areas of endemicityIn initial reports, the TEM- (Temoneira) and SHV- (Sulfhydryl variable) enzymes dominated, mainly in . The number of TEM and SHV variants is now more than 220 and 190 respectively (www.
lahey.org/Studies/). CTX-M- (Cefotaximase- enzymes were rare until the end of the 1980s. The CTX-M ?-lactamases now exceed 170 different types (www.lahey.
org/Studies/), and can be divided into five groups based on their amino acid identities: CTX-M-1, CTX-M-2, CTX-M-8, CTX-M-9, and CTX-M-25. CTX-M-15 belongs to the CTX-M-1 group and is the most common enzyme both globally and in Sweden (Brolund, A., et al., 2014). At first, most dissemination was associated with , but with the CTX-M enzymes, ESBL-producing enzymes were more commonly introduced in . This promoted rapid dissemination in the community and also made the EPE become an increasing problem in common community-acquired infection such as UTIs (Pitout, J.D. and K.
B. Laupland, 2008). In 2007, the year that mandatory laboratory reporting of EPE was introduced in Sweden; almost 2100 new EPE-cases were detected. Since then