Treating infections caused by carbapenemase-producing Enterobacteriaceae.

Carbapenemase-producing Enterobacteriaceae (CPE) have spread worldwide, causing serious infections with increasing frequency. CPE are resistant to almost all available antibiotics, complicating therapy and limiting treatment options. Mortality rates associated with CPE infections are unacceptably high, indicating that the current therapeutic approaches are inadequate and must be revised. Here, we review 20 clinical studies (including those describing the largest cohorts of CPE-infected patients) that provided the necessary information regarding isolate and patient characteristics and treatment schemes, as well as a clear assessment of outcome. The data summarized here indicate that treatment with a single in vitro active agent resulted in mortality rates not significantly different from that observed in patients treated with no active therapy, whereas combination therapy with two or more in vitro active agents was superior to monotherapy, providing a clear survival benefit (mortality rate, 27.4% vs. 38.7%; p <0.001). The lowest mortality rate (18.8%) was observed in patients treated with carbapenem-containing combinations.

Carbapenemases in Klebsiella pneumoniae and other Enterobacteriaceae: an evolving crisis of global dimensions.

SUMMARY: The spread of Enterobacteriaceae, primarily Klebsiella pneumoniae, producing KPC, VIM, IMP, and NDM carbapenemases, is causing an unprecedented public health crisis. Carbapenemase-producing enterobacteria (CPE) infect mainly hospitalized patients but also have been spreading in long-term care facilities. Given their multidrug resistance, therapeutic options are limited and, as discussed here, should be reevaluated and optimized. Based on susceptibility data, colistin and tigecycline are commonly used to treat CPE infections. Nevertheless, a review of the literature revealed high failure rates in cases of monotherapy with these drugs, whilst monotherapy with either a carbapenem or an aminoglycoside appeared to be more effective. Combination therapies not including carbapenems were comparable to aminoglycoside and carbapenem monotherapies. Higher success rates have been achieved with carbapenem-containing combinations. Pharmacodynamic simulations and experimental infections indicate that modification of the current patterns of carbapenem use against CPE warrants further attention. Epidemiological data, though fragmentary in many countries, indicate CPE foci and transmission routes, to some extent, whilst also underlining the lack of international collaborative systems that could react promptly and effectively. Fortunately, there are sound studies showing successful containment of CPE by bundles of measures, among which the most important are active surveillance cultures, separation of carriers, and assignment of dedicated nursing staff.

Carbapenemase-producing Klebsiella pneumoniae: (when) might we still consider treating with carbapenems?

Infections caused by carbapenemase-producing Klebsiella pneumoniae (CPKP) are increasing in frequency worldwide. CPKP isolates exhibit extensive drug resistance phenotypes, complicate therapy, and limit treatment options. Although CPKP isolates are often highly resistant to carbapenems, a proportion of these have relatively low MICs for carbapenems, raising the question of whether this class of agents has any therapeutic potential against CPKP infections. Results from animal studies and patient outcome data indicate that carbapenems retain meaningful in vitro activity against CPKP isolates with carbapenem MICs of ≤ 4 mg/L. Accumulating clinical experience also suggests that the therapeutic efficacy of carbapenems against CPKP isolates with MICs of ≤ 4 mg/L is enhanced when these agents are administered in combination with another active antibiotic. The results of human pharmacokinetic/pharmacodynamic studies are in line with the above observations; it is highly probable that a high-dose/prolonged-infusion regimen of a carbapenem would attain a time above the MIC value of 50% for CPKP isolates with MICs up to 4 mg/L, ensuring acceptable drug exposure and favourable treatment outcome. The analyses summarized in this review support the notion that carbapenems have their place in the treatment of CPKP infections and that the currently proposed EUCAST clinical breakpoints could direct physicians in making treatment decisions.

Serum bactericidal activity of three different dosing regimens of colistin with implications for optimum clinical use.

Although colistin methanesulfonate (CMS) has been used extensively in critically ill patients infected with multidrug-resistant organisms, the optimum dosing regimen remains to be determined. Herein, we examined the pharmacokinetics of three different dosing regimens of CMS, 3 million units every 8 h (regimen A), 4.5 million units every 12 h (regimen B), 9 million units every 24 h (regimen C) and evaluated the bactericidal activity of serum containing various concentrations of colistin against Pseudomonas aeruginosa with a minimum inhibitory concentration (MIC) of 1 microg/ml. the means +/- SE serum C(max )of colistin for regimens A, B, and C were 3.34+/-0.35, 2.98+/-0.27, and 5.63+/-0.87 microg/ml, respectively. All serum samples containing colistin >4 microg/ml (serum concentration/MIC >4) eliminated P. aeruginosa whereas only 40% of samples containing colistin <4 microg/ml resulted in complete bacterial killing. these findings indicate that the currently used dosing regimens might not provide the most effective therapy with CMS and justify administering larger dosages in longer intervals.

Low genetic diversity of the intrinsic OXA-51-like class D carbapenemases among Acinetobacter baumannii clinical isolates in Greece.

This study examined the geographical distribution and diversity of the intrinsic OXA-51-like class D carbapenemases among Acinetobacter baumannii clones recovered in three major Greek regions from 2000 to 2005. The blaOXA-66 allele was exclusively detected among clonally distinct A. baumannii isolates recovered in the regions of Thessaloniki and Larissa. This sequence was also the most widespread among A. baumannii isolates in Athens, while less frequent were blaOXA-69 and blaOXA-65 alleles. These findings highlight the high prevalence of a specific blaOXA-51-like allele in Greece, possibly indicating that our A. baumannii clones might have originated from a common ancestor. However, the possibility that blaOXA-51-like variants, with blaOXA-66 predominating, are widely disseminated among several unrelated A. baumannii strains cannot be excluded.

The influence of local instillation of fusidic acid on the development of microbial complications after lung resection.

The efficacy of local instillation of fusidic acid in the prevention of post-surgical microbial complications during various types of lung resection was studied. Four hundred ninety two consecutive patients who underwent 504 thoracotomies for non-small cell lung carcinoma during April 1998-May 2004 were reviewed. The 290 patients of the first period who underwent 298 thoracotomies received a chemoprophylactic regimen of intravenous cefuroxime while the 202 patients of the second period who underwent 206 thoracotomies were additionally treated with fusidic acid, irrigated with local instillation into the pleural space, for the prevention of postoperative septic complications. Patients were followed postoperatively for development of septic complications (empyema and bronchopleural fistula) as well as of pneumonia and wound infection. Seventeen patients (5.7%) of the first period developed empyema and 13 fistula (4.4%), whereas only 2 patients (1.0%) of the second period developed empyema and fistula (OR = 5.876; 95% CI, 1.343- 25.716; P = 0.008 and OR = 4.193; 95% CI, 1.003-20.130; P = 0.034, respectively). Cases of pneumonia decreased, but not significantly, from 21 (7.0%) during the first period to 9 (4.4%) during the second period (OR = 1.613; 95% CI, 0.724-3.593; P = 0.257) while cases of wound infection decreased significantly from 19 (6.4%) to 2 (1.0%) (OR = 6.567; 95% CI, 1.513-28.510; P = 0.003). During the first period 23 pathogens were found from cases of empyema and 73 pathogens from cases of pneumonia and wound infection, whereas during the second period 3 and 18 pathogens were respectively found (OR = 5.3; 95% CI, 1.570-17.888; P = 0.003, and OR = 2.804; 95% CI, 1.628-4.838; P <0.001, respectively). These results indicate that local instillation of fusidic acid in the pleural space prior to lung resection seems effective in reducing the rate of septic complications as well as of wound infections.

Outbreak of multiple clones of imipenem-resistant Acinetobacter baumannii isolates expressing OXA-58 carbapenemase in an intensive care unit.

OBJECTIVES: To investigate the resistance mechanisms and the genetic relationship of imipenem-resistant Acinetobacter baumannii isolates recovered in the intensive care unit (ICU) of a tertiary care hospital. METHODS: Imipenem-resistant A. baumannii clinical and environmental isolates were collected in the ICU of the Red Cross General Hospital, Athens, Greece between March and October 2002. The isolates were tested by Etest MBL, PCR, RT-PCR and sequencing for carbapenemase-encoding genes, PFGE and synergy experiments using meropenem and the efflux pump inhibitor carbonyl cyanide chlorophenylhydrazone. RESULTS: During the study period, 15 clinical and two environmental imipenem-resistant (MIC 8 to >128 mg/L) A. baumannii isolates were recovered. PFGE showed six different clones that included both clinical and environmental isolates. All 17 isolates were negative by Etest MBL and PCR for genes bla(IMP), bla(VIM), bla(SPM), bla(OXA-23-like) and bla(OXA-24-like). Genes bla(OXA-51-like) and bla(OXA-58-like) were amplified from 15 and 14 isolates, respectively. Sequencing of bla(OXA-51-like) amplicons identified bla(OXA-66) (nine cases) and bla(OXA-69) (six cases), whereas bla(OXA-58-like) sequences were classical bla(OXA-58). Reverse transcriptase-PCR showed that bla(OXA-51-like) genes were expressed in 12 and bla(OXA-58) in 10 isolates; in these isolates, inhibition of OXA enzymes by 200 mM of NaCl reduced carbapenem MICs by up to 4-fold. Overexpression of proton-gradient dependent efflux pumps did not contribute to carbapenem resistance in any isolate. Similarly, although AmpC expression was demonstrated in eight isolates, inhibition of AmpC with cloxacillin did not reduce the MICs of carbapenems significantly. CONCLUSIONS: These findings indicate wide dissemination of OXA-58 carbapenemase, which contributes, at least partially, to the imipenem resistance of unrelated A. baumannii isolates in our ICU.

Evolution of antibiotic resistance of non-typhoidal salmonellae in Greece during 1990-97.

Susceptibility to 15 antibiotics was determined in 1548 non-typhoidal salmonella strains isolated in Greece from l990 to l997. The overall prevalence of resistance of both Salmonella enterica serotype Enteritidis and Salmonella enterica serotype Typhimurium increased during the first years of the study. A decrease was observed from 1996, especially for S. Enteritidis, which showed the highest overall antibiotic resistance. S. Typhimurium was the serotype with the highest multiresistance to antibiotics. The rest of the serotypes had very low resistance prevalence compared with both S. Enteritidis and Typhimurium serotypes.

Epidemiology of antibiotic resistance of human nontyphoidal salmonellae in Greece during an 8-year period (1990-1997).

The susceptibility patterns of 1027 nontyphoidal Salmonella strains of human origin, isolated in Greece between 1990 and 1997, were determined by broth microdilution. From 1990 to 1995, the overall incindence of resistance for both Salmonella enteritidis and S. typhimurium increased. From 1996 onwards, a decrease was observed, which was more evident for S. enteritidis. Regarding the other examined serotypes a substantial proportion of resistant isolates was found only for S. Virhow and S.

Evolution of antibiotic resistance of non-typhoidal salmonellae in Greece during 1990-97.

Susceptibility to 15 antibiotics was determined in 1548 non-typhoidal salmonella strains isolated in Greece from l990 to l997. The overall prevalence of resistance of both Salmonella enterica serotype Enteritidis and Salmonella enterica serotype Typhimurium increased during the first years of the study. A decrease was observed from 1996, especially for S. Enteritidis, which showed the highest overall antibiotic resistance. S. Typhimurium was the serotype with the highest multiresistance to antibiotics. The rest of the serotypes had very low resistance prevalence compared with both S. Enteritidis and Typhimurium serotypes.

Multiple clones within multidrug-resistant Salmonella enterica serotype Typhimurium phage type DT104. The Greek Nontyphoidal Salmonella Study Group.

Six distinct clones were present among Greek multidrug-resistant Salmonella enterica serotype Typhimurium phage type DT104, since isolates belonging to resistance phenotypes including the ACSSuT (ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline) core could be distinguished with respect to their pulsed-field gel electrophoresis patterns, int1 integron structures, and presence or absence of antibiotic resistance genes ant(3'')-Ia, pse-1, and tem-1.

Outbreak of Salmonella gastroenteritis among attendees of a restaurant opening in Grece, June 1998.

Until recently the system for reporting infectious diseases in Greece was inadequate, but a new laboratory reporting system was introduced in 1998, in which collaborating laboratories throughout Greece report each week by e-mail or fax using standard form

Two novel plasmid-mediated cefotaxime-hydrolyzing beta-lactamases (CTX-M-5 and CTX-M-6) from Salmonella typhimurium.

Two novel plasmid-mediated beta-lactamases (CTX-M-5 and CTX-M-6) produced by Salmonella typhimurium clinical strains were characterized. The enzymes exhibited a pI of 8.4, hydrolyzed oxyimino-beta-lactams and were susceptible to mechanism-based beta-lactamase inhibitors. The respective bla genes were cloned and sequenced. The deduced amino acid sequences showed a high degree of homology with those of the previously described plasmid class A CTX-M-type enzymes and appeared related to the chromosomal beta-lactamases of Klebsiella oxytoca.

Molecular epidemiology of antibiotic resistance of Salmonella enteritidis during a 7-year period in Greece.

A significant increase in the frequency of isolation of Salmonella enteritidis has been observed during recent years in Greece, parallelled by an increasing rate of resistance of this organism to antibiotics. A substantial proportion of ampicillin- and doxycycline-resistant isolates exhibited cross-resistance to drugs of other classes, such as sulfonamides and streptomycin. Isolates of human origin were overall less resistant than those of animal or food-feed origin. Indeed, strains associated with animal infections were characterized by the highest rates of resistance to several antibiotics. These phenotypic data were correlated with genotypic information concerning two distinct populations: isolates from all sources that were resistant only to ampicillin, the drug toward which resistance rates were highest, and a control group of sensitive isolates. Ampicillin resistance was due to a 34-MDa conjugative plasmid. DNA fingerprinting by macrorestriction of genomic DNA revealed two types, A and B, common to both ampicillin-resistant and -sensitive strains, with 80 to 90% of strains being of type A. However, a third type, C, was specific for the sensitive population, representing 17% of those strains. Therefore, although the majority of resistant isolates were genetically related to sensitive ones, there existed a susceptible clone which had not acquired any resistance traits.