Risk factors for occurrence and 30-day mortality for carbapenem-resistant Acinetobacter baumannii bacteremia in an intensive care unit

To assess the risk factors for carbapenem-resistant Acinetobacter baumannii (CRAB) bacteremia and for 30-day mortality in patients with CRAB bacteremia in the intensive care unit (ICU), we conducted a retrospective study in the ICU at Severance Hospital in Korea from January 2008 to December 2009. Patients who acquired CRAB bacteremia in the ICU were enrolled as the case group and patients whose specimens of blood culture, sputum/endotracheal aspirate and urine revealed no AB were enrolled as controls. The case group comprised 106 patients and 205 patients were included as controls. Risk factors independently associated with CRAB bacteremia included prior chemotherapy or radiotherapy treatment (Odds ratio [OR], 3.6; P = 0.003), recent central venous catheter insertion (OR, 5.7; P < 0.001) or abdominal drainage insertion (OR, 21.9; P = 0.004), the number of antibiotics treated with (OR, 1.3; P = 0.016), and respiratory failure in the ICU (OR, 2.5; P = 0.035). The 30-day mortality was 79.8%. Renal failure during ICU stay was independently associated with 30-day mortality (OR, 3.7; P = 0.047). It is important to minimize invasive procedures, and to restrict excessive use of antibiotics, especially in immunocompromised patients, in order to prevent the development of CRAB bacteremia. Greater concern for CRAB bacteremia patients is needed when renal failure develops during ICU stay.

Multidrug-resistant Pseudomonas aeruginosa outbreaks in two hospitals: association with contaminated hospital waste-water systems

BACKGROUND

Multidrug-resistant Pseudomonas aeruginosa (MDR-P) expressing VIM-metallo-beta-lactamase is an emerging infection control problem. The source of many such infections is unclear, though there are reports of hospital outbreaks of P. aeruginosa related to environmental contamination, including tap water.

AIM

We describe two outbreaks of MDR-P, sensitive only to colistin, in order to highlight the potential for hospital waste-water systems to harbour this organism.

METHODS

The outbreaks were investigated by a combination of descriptive epidemiology, inspection and microbiological sampling of the environment, and molecular strain typing.

FINDINGS

The outbreaks occurred in two English hospitals; each involved a distinct genotype of MDR-P. One outbreak was hospital-wide, involving 85 patients, and the other was limited to four cases in one specialized medical unit. Extensive environmental sampling in each outbreak yielded MDR-P only from the waste-water systems. Inspection of the environment and estates records revealed many factors that may have contributed to contamination of clinical areas, including faulty sink, shower and toilet design, clean items stored near sluices, and frequent blockages and leaks from waste pipes. Blockages were due to paper towels, patient wipes, or improper use of bedpan macerators. Control measures included replacing sinks and toilets with easier-to-clean models less prone to splashback, educating staff to reduce blockages and inappropriate storage, reviewing cleaning protocols, and reducing shower flow rates to reduce flooding. These measures were followed by significant reductions in cases.

CONCLUSION

The outbreaks highlight the potential of hospital waste systems to act as a reservoir of MDR-P and other nosocomial pathogens.

Changing epidemiology of Clostridium difficile infection following the introduction of a national ribotyping-based surveillance scheme in England

BACKGROUND

Marked increases in Clostridium difficile infection (CDI) incidence, driven by epidemic strain spread, is a global phenomenon.

METHODS

The Clostridium difficile Ribotyping Network (CDRN) was established in 2007 as part of enhanced CDI surveillance in England, to facilitate the recognition and control of epidemic strains. We report on changes in CDI epidemiology in England in the first 3 years of CDRN.

RESULTS

CDRN received 12,603 fecal specimens, comprising significantly (P < .05) increasing numbers and proportions of national CDI cases in 2007-2008 (n = 2109, 3.8%), 2008-2009 (n = 4774, 13.2%), and 2009-2010 (n = 5720, 22.3%). The C. difficile recovery rate was 90%, yielding 11,294 isolates for ribotyping. Rates of 9 of the 10 most common ribotypes changed significantly (P < .05) during 2007-2010. Clostridium difficile ribotype 027 predominated, but decreased markedly from 55% to 36% and 21% in 2007-2008, 2008-2009, and 2009-2010, respectively. The largest regional variations in prevalence occurred for ribotypes 027, 002, 015, and 078. Cephalosporin and fluoroquinolone use in CDI cases was reported significantly (P < .05) less frequently during 2007-2010. Mortality data were subject to potential reporting bias, but there was a significant decrease in CDI-associated deaths during 2007-2010, which may have been due to multiple factors, including reduced prevalence of ribotype 027.

CONCLUSIONS

Access to C. difficile ribotyping was associated with significant changes in the prevalence of epidemic strains, especially ribotype 027. These changes coincided with markedly reduced CDI incidence and related mortality in England. CDI control programs should include prospective access to C. difficile typing and analysis of risk factors for CDI and outcomes.

Investigation of Acinetobacter baumannii resistance to carbapenems in Marseille hospitals, south of France: a transition from an epidemic to an endemic situation

Carbapenem-resistant Acinetobacter baumannii infections are a worldwide endemic nosocomial threat. Between December 2010 and April 2011, an increase of carbapenem-resistant A. baumannii infections occurred in several Marseille University Hospitals. The aim of this study was to investigate the increase of carbapenem-resistant A. baumannii infections and to characterize the mechanisms of carbapenem resistance. The increase was detected by a homemade computer surveillance program, known as EPIMIC, that monitors antibiotic resistance profiles on a weekly basis. During this period, positive samples of carbapenem-resistant A. baumannii were retrieved from patients hospitalized in different units. Genotyping of the isolates was performed using pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST), and carbapenemase gene analyses were performed to detect the presence of carbapenemases and to determine the relationships of the isolates. Carbapenem-resistant A. baumannii were isolated in a total of 11 patients who were hospitalized in different hospitals units. We identified the presence of the bla(OXA23-like) carbapenemase-encoding gene in all of the isolates and found four major PFGE groups and different MLST groups. These results demonstrate a current evolution in the A. baumannii epidemiology in Marseille with a switch from an epidemic situation to an endemic situation and with several circulating clones.

Old agent, new experience: colistin use in the paediatric Intensive Care Unit--a multicentre study

Nosocomial infections caused by multidrug-resistant (MDR) microorganisms are a common problem around the world, especially in Intensive Care Units. The aim of this study was to investigate the efficacy and safety of colistin therapy in paediatric patients with severe nosocomial infections caused by MDR Gram-negative bacteria. There were 87 episodes in 79 paediatric Intensive Care Unit patients in five different hospitals; each patient was treated intravenously with colistin and evaluated. Of the 79 patients, 54.4% were male and the median age was 30 months. The most commonly isolated microorganism was Acinetobacter baumannii, the most common isolation site was tracheal aspirate fluid and the most common type of infection was ventilator-associated pneumonia. The mean colistin dose in patients without renal failure was 5.4 ± 0.6 mg/kg/day, the mean therapy duration was 17.2 ± 8.4 days and the favourable outcome rate was 83.9%. Serious side effects were seen in four patient episodes (4.6%) during therapy; two patients suffered renal failure and the others had convulsive seizures. Other patients tolerated the drug well. The infection-related mortality rate was 11.5% and the probability of death within the first 9 days of treatment was 10 times higher than after the first 9 days. In conclusion, this study suggests that colistin is effective in the treatment of severe nosocomial infections caused by MDR Gram-negative bacteria and is generally well tolerated by patients, even after relatively long-term use.

Epidemiological study of Enterobacteriaceae resistance to colistin in Sfax (Tunisia)

OBJECTIVES

The authors had for aim to monitor Enterobacteriaceae resistance to colistin, during 6 years (2005-2010), and to study the epidemiology of Enterobacteriaceae resistant strains isolated in the Sfax region (Tunisia).

DESIGN

This retrospective study was carried out in the microbiology laboratory, at the Habib Bourguiba teaching hospital in Sfax. All strains of colistin resistant Enterobacteriaceae isolated from patients were studied.

RESULTS

One hundred and twenty one strains of colistin resistant Enterobacteriaceae were isolated from 93 patients. Klebsiella pneumoniae was the most frequent species (60.2%), followed by Enterobacter cloacae (26.9%), and Escherichia coli (12.9%). Thirteen strains (E. cloacae) were heteroresistant to colistin. Eighty one isolates (87.1%) were resistant to third generation cephalosporins. The rate of resistance to colistin ranged from 0.09% for E. coli to 1.2% for K. pneumoniae, and 1.5% for E. cloacae. A progressively increasing colistin resistance was observed for K. pneumoniae. Most resistant strains were isolated from urine in the urology department. Previous exposure to colistin was reported in 59.2% of patients. Pulsed field gel electrophoresis typing revealed different clones.

CONCLUSIONS

Colistin resistance in Enterobacteriaceae is a worrying phenomenon in Sfax. It is related to polyclonal diffusion. Continuous epidemiological monitoring and a rational use of colistin are necessary to limit the spreading of these colistin resistant strains and to maintain this antibiotic's effectiveness.

Structures of Helicobacter pylori shikimate kinase reveal a selective inhibitor-induced-fit mechanism

Shikimate kinase (SK), which catalyzes the specific phosphorylation of the 3-hydroxyl group of shikimic acid in the presence of ATP, is the enzyme in the fifth step of the shikimate pathway for biosynthesis of aromatic amino acids. This pathway is present in bacteria, fungi, and plants but absent in mammals and therefore represents an attractive target pathway for the development of new antimicrobial agents, herbicides, and antiparasitic agents. Here we investigated the detailed structure–activity relationship of SK from Helicobacter pylori (HpSK). Site-directed mutagenesis and isothermal titration calorimetry studies revealed critical conserved residues (D33, F48, R57, R116, and R132) that interact with shikimate and are therefore involved in catalysis. Crystal structures of HpSK·SO₄, R57A, and HpSK•shikimate-3-phosphate•ADP show a characteristic three-layer architecture and a conformationally elastic region consisting of F48, R57, R116, and R132, occupied by shikimate. The structure of the inhibitor complex, E114A•162535, was also determined, which revealed a dramatic shift in the elastic LID region and resulted in conformational locking into a distinctive form. These results reveal considerable insight into the active-site chemistry of SKs and a selective inhibitor-induced-fit mechanism.

Outcome of ventilator-associated pneumonia due to multidrug-resistant Acinetobacter baumannii and Pseudomonas aeruginosa treated with aerosolized colistin in neonates: a retrospective chart review

Multidrug-resistant (MDR) gram-negative bacteria-related nosocomial infections and ventilator-associated pneumonia (VAP) presents an emerging challenge to clinicians. Older antimicrobial agents such as colistin have become life-saving drugs because of the susceptibility of these pathogens. We report our experience with aerosolized colistin in two preterm and one term neonate with Acinetobacter baumannii and Pseudomonas aeruginosa-related VAP who were unresponsiveness to previous antimicrobial treatment. All pathogens were isolated from tracheal aspirate. We used 5 mg/kg (base activity) aerosolized colistin methanesulfonate sodium in every 12 h as an adjunctive therapy for VAP. VAP was treated by 14, 14, and 16-day courses of aerosolized colistin in these patients, respectively. No adverse effect such as nephrotoxicity or neurotoxicity was observed. We found that aerosolized colistin was tolerable and safe, and it may be an adjunctive treatment option for MDR gram-negative bacterial VAP in neonates. Further studies are needed to determine appropriate doses for aerosolized colistin and its eligibility as an alternative treatment choice in newborns.

In vitro antibacterial activity of the ceftazidime-avibactam (NXL104) combination against Pseudomonas aeruginosa clinical isolates

The β-lactamase inhibitor avibactam (NXL104) displays potent inhibition of both class A and C enzymes. The in vitro antibacterial activity of the combination ceftazidime-avibactam was evaluated against a clinical panel of Pseudomonas aeruginosa isolates. Avibactam offered efficient protection from hydrolysis since 94% of isolates were susceptible to ceftazidime when combined with 4 μg/ml avibactam, compared with 65% susceptible to ceftazidime alone. Ceftazidime-avibactam also demonstrated better antipseudomonal activity than imipenem (82% susceptibility), a common reference treatment.

Infections, bacterial resistance, and antimicrobial stewardship: the emerging role of hospitalists

The care of patients with serious infections both within and outside healthcare settings is increasingly complicated by the high prevalence of resistant or multidrug-resistant (MDR) pathogens. Moreover, infections caused by MDR versus susceptible bacteria or other pathogens are associated with significantly higher mortality, length of hospital stay, and healthcare costs. Antimicrobial misuse or overuse is the primary driver for development of antimicrobial resistance, suggesting that better use of antimicrobials will translate into improved patient outcomes, more efficient use of hospital resources, and lowered healthcare costs. Antimicrobial stewardship refers to the various practices and procedures utilized to optimize antimicrobial use. The primary goal of antimicrobial stewardship is to improve patient outcomes and lower antimicrobial resistance and other unintended consequences of antimicrobial therapy. Secondary goals are to reduce length of hospital stays and healthcare-related costs. Hospitalists are increasingly involved in the care of hospitalized patients throughout the United States. Expertise in managing conditions requiring hospitalization, and experience in quality improvement across a wide range of clinical conditions, make hospitalists well positioned to participate in the development and implementation of hospital-based antimicrobial stewardship programs designed to improve patient outcomes, reduce antimicrobial resistance, and provide more efficient and lower-cost hospital care.

Class 2 integrons dissemination among multidrug resistance (MDR) clones of Acinetobacter baumannii

Acinetobacter baumannii has emerged as a serious problem in the hospital environment at a global scale. Previous results from our laboratory showed a high frequency of class 2 integrons in A. baumannii strains from Argentina regarding the low rate of this element in A. baumannii isolates from the rest of the world. To reveal the current epidemiology of class 2 integrons, a molecular surveillance analyzing 78 multidrug resistant (MDR) A. baumannii isolates from Argentina and Uruguay was performed, exposing the presence of class 2 integron in the 36.61% of the isolates. Class 2 integron characterization showed that the typical Tn7::In2-7 array was present in 26 out of 27 intI2 positive isolates. All intI2 positive isolates contained at least one of the Tn7 transposition genes. In addition, we identified that 18 intI2 positive isolates possessed the Tn7::In2-7 within the attTn7 site. The molecular typing evidenced that clones I and IV that do not belong to widespread European clones I and II were found among the intI2 positive isolates. Our results exposed the widely dissemination of class 2 integron among MDR A. baumannii isolates from Argentina and Uruguay, also showing the persistence of two novel clones in our region, which could explain in part the high frequency of class 2 integron found in our region.

Activity of pyocin S2 against Pseudomonas aeruginosa biofilms

In cystic fibrosis patients, chronic lung infection with Pseudomonas aeruginosa and the associated decline in lung function are the major cause of mortality. In this report, we show that pyocin S2 displays potent activity against P. aeruginosa biofilms, thus representing a potentially improved therapeutic option. Using an invertebrate model of P. aeruginosa infection, we also show that pyocin S2 is highly active in vivo.

Prospective multicenter study of the impact of carbapenem resistance on mortality in Pseudomonas aeruginosa bloodstream infections

The impact of antimicrobial resistance on clinical outcomes is the subject of ongoing investigations, although uncertainty remains about its contribution to mortality. We investigated the impact of carbapenem resistance on mortality in Pseudomonas aeruginosa bacteremia in a prospective multicenter (10 teaching hospitals) observational study of patients with monomicrobial bacteremia followed up for 30 days after the onset of bacteremia. The adjusted influence of carbapenem resistance on mortality was studied by using Cox regression analysis. Of 632 episodes, 487 (77%) were caused by carbapenem-susceptible P. aeruginosa (CSPA) isolates, and 145 (23%) were caused by carbapenem-resistant P. aeruginosa (CRPA) isolates. The median incidence density of nosocomial CRPA bacteremia was 2.3 episodes per 100,000 patient-days (95% confidence interval [CI], 1.9 to 2.8). The regression demonstrated a time-dependent effect of carbapenem resistance on mortality as well as a significant interaction with the Charlson index: the deleterious effect of carbapenem resistance on mortality decreased with higher Charlson index scores. The impact of resistance on mortality was statistically significant only from the fifth day after the onset of the bacteremia, reaching its peak values at day 30 (adjusted hazard ratio for a Charlson score of 0 at day 30, 9.9 [95% CI, 3.3 to 29.4]; adjusted hazard ratio for a Charlson score of 5 at day 30, 2.6 [95% CI, 0.8 to 8]). This study clarifies the relationship between carbapenem resistance and mortality in patients with P. aeruginosa bacteremia. Although resistance was associated with a higher risk of mortality, the study suggested that this deleterious effect may not be as great during the first days of the bacteremia or in the presence of comorbidities.

Colistin therapy in critically ill patients with chronic renal failure and its effect on development of renal dysfunction

Recently, colistin has become a salvage therapy in the treatment of serious Intensive Care Unit infections owing to the emergence of extensively drug-resistant (XDR) bacterial isolates. This study aimed to show the effectiveness of colistin in critically ill patients with renal failure. A prospective case-control study of 94 patients admitted to medical intensive care units of a university hospital from December 2008 to June 2010 was conducted. All patients had infections with XDR Acinetobacter baumannii or Pseudomonas aeruginosa and received colistin. Cases comprised 39 patients with chronic renal failure (CRF) and controls were other patients without CRF. Apart from the male dominancy in the CRF group, there was no statistical difference between the two groups regarding demographic characteristics, Acute Physiology and Chronic Health Evaluation (APACHE) II score, and site and type of infection. In patients who completed colistin therapy, bacteriological cure was seen in 87% of patients with CRF and 95% of patients without CRF (P=0.890). Mortality in patients with CRF was similar to that in patients without CRF (44% and 42%, respectively) (P=0.999). Nephrotoxicity developed in 23.6% of patients in the control group. Concomitant nephrotoxic agents and total defined daily dose of colistin did not affect the development of nephrotoxicity. The mortality rate was 38% in patients with nephrotoxicity, similar to the mortality rate in patients without nephrotoxicity (36%) (P=0.999). In conclusion, in critically ill patients with CRF, colistin therapy, although used at a reduced dosage, was as effective as in patients without CRF.

Emergence of resistance to carbapenems in Acinetobacter baumannii in Europe: clinical impact and therapeutic options

Despite having a reputation of low virulence, Acinetobacter baumannii is an emerging multidrug-resistant (MDR) pathogen responsible for community- and hospital-acquired infections that are difficult to control and treat. Interest in this pathogen emerged about one decade ago because of its natural MDR phenotype, its capability of acquiring new mechanisms of resistance and the existence of nosocomial outbreaks. Recent advances in molecular biology, including full genome sequencing of several A. baumannii isolates, has led to the discovery of the extraordinary plasticity of their genomes, which is linked to their great propensity to adapt to any environment, including hospitals. In this context, as well as the increasing antimicrobial resistance amongst A. baumannii isolates to the last-line antibiotics carbapenems and colistin, therapeutic options are very limited or absent in some cases of infections with pandrug-resistant bacteria. However, a large proportion of patients may be colonised by such MDR bacteria without any sign of infection, leading to a recurrent question for clinicians as to whether antibiotic treatment should be given and will be effective in the presence of resistance mechanisms. The worldwide emergence of A. baumannii strains resistant to colistin is worrying and the increasing use of colistin to treat infections caused by MDR bacteria will inevitably increase the recovery rate of colistin-resistant isolates in the future. Current knowledge about A. baumannii, including biological and epidemiological aspects as well as resistance to antibiotics and antibiotic therapy, are reviewed in this article, in addition to therapeutic recommendations.

Interplay between mutational and horizontally acquired resistance mechanisms and its association with carbapenem resistance amongst extensively drug-resistant Pseudomonas aeruginosa (XDR-PA)

Between 2003 and 2009, the prevalence of extensively drug-resistant Pseudomonas aeruginosa (XDR-PA) increased significantly in northern Taiwan from 1.0% to 2.1%. Molecular methods were used to investigate the genetic relatedness and carbapenem resistance mechanisms of a collection of 203 non-repetitive XDR-PA isolates available for study. Using pulsed-field gel electrophoresis (PFGE), 52 genotypes were observed; one predominant genotype (pulsotype 1) was found in 57.6% of the isolates. Polymerase chain reaction (PCR), sequencing and quantitative reverse-transcriptase PCR analyses demonstrated that one horizontally acquired mechanism [metallo-β-lactamase (MBL) genes] and two mutational mechanisms (efflux and porins) accounted for the carbapenem resistance. The most predominant horizontally acquired mechanism was carriage of bla_VIM-3, which was found in 61.1% of isolates. Decreased expression of oprD was the most prevalent mutational mechanism and was found in 70.0% of the XDR-PA isolates, whereas overexpression of mexA was found in 27.6% of the isolates. The highlight of this study was the discovery of statistically significant relationships between certain horizontally acquired and mutational resistance mechanisms and their contribution to carbapenem susceptibility. MBL-producers expressed significantly lower MexAB and higher OprD than non-MBL-producers. Amongst isolates without an acquired β-lactamase gene, oprD expression was significantly reduced, whilst expression of efflux pumps was increased. Reduced OprD expression alone or the production of VIM-type MBLs showed similar contributions to a low to intermediate MIC₅₀ (minimum inhibitory concentration for 50% of the organisms) for carbapenems. Isolates with reduced OprD expression that simultaneously harboured bla_VIM exhibited high levels of resistance to carbapenems, which implied that these two mechanisms had a synergistic effect on the MICs.

When and how to cover for resistant gram-negative bacilli in severe sepsis and septic shock

In the 80s and 90s, increasing antibiotic resistance was met by the introduction of new effective agents with broader antibacterial spectra for the empirical treatment of severe infections. In recent years, however, few novel antimicrobials have been developed, and this has critically weakened our strength in the fight against resistant bacteria, especially Gram-negative bacilli. It has been well proven that mortality increases if initial empirical antibiotic treatment for severe infection is inappropriate due to resistance of the pathogen. Physicians are already faced with the increasing challenge of untreatable or almost untreatable Gram-negative infections due to antibiotic resistance. Empirical treatment with broader spectra and high antibiotic pressure both in- and outside hospital is the driving force behind resistance. Since new efficient drugs against Gram-negative bacilli will not be available for some time, the best we can do to stop infections caused by multidrug-resistant bacteria is to improve infection control and choice of antibiotics, which should be based on surveillance of local antibiotic consumption and resistance. We must learn more about the revived antibacterial agents colistin and fosfomycin, and the few next generation Gram-negative antibiotics that have been developed. The aim of this review is to give an update on present therapeutic options in the fight against multidrug-resistant Gram-negative bacteria.

Antimicrobial susceptibility of global inpatient urinary tract isolates of Escherichia coli: results from the Study for Monitoring Antimicrobial Resistance Trends (SMART) program: 2009-2010

Escherichia coli is the most important uropathogen. The Study for Monitoring Antimicrobial Resistance Trends program collected 1643 E. coli isolates in 2009-2010 from urinary tract infection (UTI) specimens of hospitalized patients in countries worldwide. Ertapenem and imipenem were the most active agents tested, inhibiting >98% of all E. coli phenotypes. Overall, 17.9% of isolates were extended-spectrum beta-lactamase (ESBL) producers. The highest ESBL rate was from the Asia/Pacific region (27.7%). Amikacin and piperacillin-tazobactam achieved 90% inhibition levels only for ESBL-negative isolates. Ciprofloxacin and levofloxacin were not effective for ESBL-positive isolates, with only 14.6% and 15.9% susceptible, respectively. These observations highlight the need for continued monitoring of susceptibility of E. coli isolated from hospitalized patients with UTIs.

Antibiotic policy

There is a clear association between antibiotic use and resistance both on individual and population levels. In the European Union, countries with large antibiotic consumption have higher resistance rates. Antibiotic resistance leads to failed treatments, prolonged hospitalisations, increased costs and deaths. With few new antibiotics in the Research & Development pipeline, prudent antibiotic use is the only option to delay the development of resistance. Antibiotic policy consists of prescribing strategies to optimise the indication, selection, dosing, route of administration, duration and timing of antibiotic therapy to maximise clinical cure or prevention of infection whilst limiting the unintended consequences of antibiotic use, including toxicity and selection of resistant microorganisms. A secondary goal is to reduce healthcare costs without adversely affecting the quality of care. The purpose of this paper is to provide the evidence base of prudent antibiotic policy. Special emphasis is placed on urinary tract infections. The value and support of antibiotic committees, guidelines, ID consultants and/or antimicrobial stewardship teams to prolong the efficacy of available antibiotics will be discussed.

Antibiotic acyldepsipeptides activate ClpP peptidase to degrade the cell division protein FtsZ

The worldwide spread of antibiotic-resistant bacteria has lent urgency to the search for antibiotics with new modes of action that are devoid of preexisting cross-resistances. We previously described a unique class of acyldepsipeptides (ADEPs) that exerts prominent antibacterial activity against Gram-positive pathogens including streptococci, enterococci, as well as multidrug-resistant Staphylococcus aureus. Here, we report that ADEP prevents cell division in Gram-positive bacteria and induces strong filamentation of rod-shaped Bacillus subtilis and swelling of coccoid S. aureus and Streptococcus pneumoniae. It emerged that ADEP treatment inhibits septum formation at the stage of Z-ring assembly, and that central cell division proteins delocalize from midcell positions. Using in vivo and in vitro studies, we show that the inhibition of Z-ring formation is a consequence of the proteolytic degradation of the essential cell division protein FtsZ. ADEP switches the bacterial ClpP peptidase from a regulated to an uncontrolled protease, and it turned out that FtsZ is particularly prone to degradation by the ADEP-ClpP complex. By preventing cell division, ADEP inhibits a vital cellular process of bacteria that is not targeted by any therapeutically applied antibiotic so far. Their unique multifaceted mechanism of action and antibacterial potency makes them promising lead structures for future antibiotic development.

Emergence and clonal dissemination of carbapenem-hydrolysing OXA-58-producing Acinetobacter baumannii isolates in Bolivia

Acinetobacter baumannii is an emerging multidrug-resistant pathogen and very little information is available regarding its imipenem resistance in Latin American countries such as Bolivia. This study investigated the antimicrobial resistance profile of 46 clinical strains from different hospitals in Cochabamba, Bolivia, from March 2008 to July 2009, and the presence of carbapenemases as a mechanism of resistance to imipenem. Isolates were obtained from 46 patients (one isolate per patient; 30 males,16 females) with an age range of 1 day to 84 years, and were collected from different sample types, the majority from respiratory tract infections (17) and wounds (13). Resistance to imipenem was detected in 15 isolates collected from different hospitals of the city. These isolates grouped into the same genotype, named A, and were resistant to all antibiotics tested including imipenem, with susceptibility only to colistin. Experiments to detect carbapenemases revealed the presence of the OXA-58 carbapenemase. Further analysis revealed the location of the bla(OXA-58) gene on a 40 kb plasmid. To our knowledge, this is the first report of carbapenem resistance in A. baumannii isolates from Bolivia that is conferred by the OXA-58 carbapenemase. The presence of this gene in a multidrug-resistant clone and its location within a plasmid is of great concern with regard to the spread of carbapenem-resistant A. baumannii in the hospital environment in Bolivia.

Cloning, expression, and enzymatic activity of Acinetobacter baumannii and Klebsiella pneumoniae acetyl-coenzyme A carboxylases

Pathogenic Gram-negative bacteria are a major public health concern because they are causative agents of life-threatening hospital-acquired infections. Due to the increasing rates of resistance to available antibiotics, there is an urgent need to develop new drugs. Acetyl-coenzyme A carboxylase (ACCase) is a promising target for the development of novel antibiotics. We describe here the expression, purification, and enzymatic activity of recombinant ACCases from two clinically relevant Gram-negative pathogens, Acinetobacter baumannii and Klebsiella pneumoniae. Recombinant ACCase subunits (AccAD, AccB, and AccC) were expressed and purified, and the holoenzymes were reconstituted. ACCase enzyme activity was monitored by direct detection of malonyl-coenzyme A (malonyl-CoA) formation by liquid chromatography tandem mass spectrometry (LC-MS/MS). Steady-state kinetics experiments showed similar k(cat) and K(M) values for both enzymes. In addition, similar IC(50) values were observed for inhibition of both enzymes by a previously reported ACCase inhibitor. To provide a higher throughput assay suitable for inhibitor screening, we developed and validated a luminescence-based ACCase assay that monitors ATP depletion. Finally, we established an enzyme activity assay for the isolated AccAD (carboxyltransferase) subunit, which is useful for determining whether novel ACCase inhibitors inhibit the biotin carboxylase or carboxyltransferase site of ACCase. The methods described here could be applied toward the identification and characterization of novel inhibitors.

Rapid control of a hospital-wide outbreak caused by extensively drug-resistant OXA-72-producing Acinetobacter baumannii

Extensively drug-resistant Acinetobacter baumannii (XDRAb) emerges as an important pathogen of health care-associated infections and outbreaks worldwide. During January and February 2006, there was a hospital-wide outbreak of XDRAb at a medical center in Taiwan. Without limiting the usage of carbapenems or the closure of any ward, this outbreak was effectively controlled. We investigated the molecular epidemiology and reported the infection control experiences. XDRAb is defined as A baumannii that is resistant to multiple antibiotics but susceptible to tigecycline and polymyxin B. During the outbreak, the clinical and environmental XDRAb isolates were collected and studied by antimicrobial susceptibility testing, pulsed-field gel electrophoresis, and polymerase chain reaction for Verona integron-encoded metallo-beta-lactamases, imipenemases, and oxacillinases (OXA). Our measures to control the outbreak included private room isolation of patients until there were three successive negative cultures, reinforcement of contact precautions, daily environmental cleansing with room-dedicated cleaning tools and sodium hypochlorite, and careful auditing of adherence. During the outbreak, 32 clinical XDRAb isolates came from 13 patients who were hospitalized in four intensive care units and three wards. Most (7 of 13, 53.8%) cases were associated with a surgical intensive care unit. The results from pulsed-field gel electrophoresis study indicated that all isolates were of one genotype. All 32 isolates harbored ISAba1-bla(OxA-51-like) and bla(OxA-72) genes. After this outbreak till August 2010, further incidences of XDRAb were sporadic cases of XDRAb with different clones and did not reach the level of outbreak. To our knowledge, this is the first reported hospital-wide outbreak caused by OXA-72 carbapenemase-producing A baumannii in the Asia-Pacific region, with successful and sustained control. Although the source or vehicle of the outbreak was not identified, our results suggest that a hospital-wide outbreak can be successfully managed with strict infection control measures, and that the limitation of the use of carbapenems and closure of wards may not be necessary.

The laboratory diagnosis of Pseudomonas aeruginosa that produce metallo-β-lactamases in a Dutch tertiary care centre

BACKGROUND

The laboratory detection of Pseudomonas aeruginosa that produce metallo-β-lactamases (MBLs) is not well defined in regions with a low prevalence of these enzymes. We report a study that developed ethylenediaminetetraacetic acid (EDTA) disk screen tests using doripenem, imipenem and meropenem and investigated the prevalence of these enzymes among clinical isolates of imipenem-resistant P. aeruginosa in Rotterdam during 2008-2009.

METHODS

Using strains with well-characterized β-lactamases and the Clinical and Laboratory Standards Institute (CLSI) disk methodology similar to extended-spectrum β-lactamase (ESBL) detection, inhibition zone diameters were determined in tests with doripenem, imipenem, and meropenem, alone and in combination with 370 μg of EDTA. These tests were compared with the MBL E-test. A positive test was a ≥5 mm increase in zone diameter in the presence of EDTA.

RESULTS

The imipenem EDTA disk screen test showed a sensitivity of 100% and a specificity of 90% in 96 recent clinical isolates. Imipenem in combination with doripenem performed better than imipenem alone, meropenem, and the MBL E-test (sensitivity of 100%; specificity of 95%). The majority of clinical isolates were isolated from patient respiratory specimens. Of the 96 imipenem-resistant P. aeruginosa isolated, 35 (36%) were positive for bla(VIM) genes.

CONCLUSIONS

The EDTA imipenem/doripenem disk test showed accurate and reproducible results with excellent sensitivity and specificity. It is simple to perform and interpret and can be easily introduced into the workflow of a clinical laboratory to screen for MBLs in imipenem-resistant P. aeruginosa. Due to its high specificity the test is also suitable for regions with a low prevalence of these enzymes.

Critical shortage of new antibiotics in development against multidrug-resistant bacteria-Time to react is now

Two commercial databases (Pharmaprojects and Adis Insight R&D) were queried for antibacterial agents in clinical development. Particular attention was given to antibacterial agents for systemic administration. For each agent, reviewers were requested to indicate whether its spectrum of activity covered a set of selected multidrug-resistant bacteria, and whether it had a new mechanism of action or a new target. In addition, PubMed was searched for antibacterial agents in development that appeared in review articles. Out of 90 agents that were considered to fulfil the inclusion criteria for the analysis, 66 were new active substances. Fifteen of these could be systemically administered and were assessed as acting via a new or possibly new mechanism of action or on a new or possibly new target. Out of these, 12 agents were assessed as having documented in vitro activity against antibiotic-resistant Gram-positive bacteria and only four had documented in vitro activity against antibiotic-resistant Gram-negative bacteria. Of these four, two acted on new or possibly new targets and, crucially, none acted via new mechanisms of action. There is an urgent need to address the lack of effective treatments to meet the increasing public health burden caused by multidrug-resistant bacteria, in particular against Gram-negative bacteria.

[Available carbapenems: Properties and differences]

Carbapenems are β-lactam antibiotics endowed with a broader spectrum, activity and resistance to β-lactamases than other β-lactams. Due to their qualities, these antibiotics are crucial in empirical therapy, in the monotherapy of several severe hospital-acquired infections -and even that of some community-acquired infections- as well as in the directed therapy of infections due to multiresistant Gram-negative bacteria. All the available carbapenems have a similar spectrum, although there are significant differences in their antimicrobial activity, which in the long run determines the clinical indications of each carbapenem. The spectrum of ertapenem does not cover eminently nosocomial pathogens such as Pseudomonas aeruginosa and Acinetobacter spp., and hence this antibiotic is indicated in community-acquired infections requiring hospital treatment. In contrast, doripenem shows greater intrinsic activity than other carbapenems in extended spectrum beta-lactamase-producing enterobacteria and AmpC P. aeruginosa, Acinetobacter spp. and other non-fermentative and anaerobic microorganisms. Additionally, like the remaining carbapenems, doripenem has adequate pharmacokinetic characteristics and a favorable safety profile.

High mortality rates among solid organ transplant recipients infected with extensively drug-resistant Acinetobacter baumannii: using in vitro antibiotic combination testing to identify the combination of a carbapenem and colistin as an effective treatment regimen

Extensively drug-resistant (XDR) Acinetobacter baumannii infections caused 91% (10/11) mortality in transplant recipients. Isolates were colistin-susceptible initially, but susceptibility decreased during therapy in 40% (4/10). We tested antibiotic combinations against XDR Acinetobacter in vitro and demonstrated positive interactions for carbapenem-colistin. Subsequently, 80% (4/5) of transplant patients were treated successfully with carbepenem-colistin regimens.

[Carbapenemases in enterobacteriaceae]

Carbapenem-hydrolyzing beta-lactamases are the most powerful mechanism of resistance to carbapenems. Carbapenemases have been reported extensively worldwide now in Enterobacteriaceae. Carbapenemases of the KPC type have been reported first from the USA in Klebsiella pneumoniae, then worldwide with a marked endemicity in Israel and Greece. Metallo-enzymes (VIM, IMP…) have been also reported internationnaly with high prevalence in Southern Europe and Asia. OXA-48 which is one of the latest carbapenemases reported differs structurally from the other carbapenemases and have been identified mostly from Mediterranean countries. These carbapenemase genes are mostly plasmid located in K. pneumoniae from nosocomial origin. They have been also identified as a source of community-acquired infections. Carbapenemase producers are also multidrug resistant explaining the difficulty to treat infections. Detection of infected patients and carriers remain difficult which may explain an underlying spread with dramatic therapeutic consequences.

Antimicrobial stewardship for inpatient facilities

Antibiotic stewardship aims to improve patient care and reduce unwanted consequences of antimicrobial overuse or misuse, including lowered efficacy, emergence of antimicrobial resistance, development of secondary infections, adverse drug reactions, increased length of hospital stay, and additional healthcare costs. Recent guidelines make specific recommendations for the development of institutional programs to enhance antimicrobial stewardship. Optimally, such programs should be comprehensive, multidisciplinary, supported by hospital and medical staff leadership, and should employ evidence-based strategies that best fit local needs and resources. An infectious diseases physician and clinical pharmacist with infectious diseases training are recommended as core members of the multidisciplinary team, although a hospitalist with interest (and perhaps additional training) in antimicrobial therapy may be able to fill the void. Program directors and core members should be compensated for their time. Principal proactive strategies--with evidence supporting their consideration--include prospective audits, with intervention and feedback, formulary restriction, and preauthorization. Other strategies include persistent one-on-one education, guidelines adapted to local needs, and informatics to support clinical decision making. Intervention goals are to prevent unnecessary antimicrobial starts, to streamline or de-escalate therapy early in its course, and to convert from parenteral to oral therapy, optimize dosing, and ensure the appropriate length of therapy. Most community hospitals, if sufficiently resourced, should be able to implement a successful antimicrobial stewardship program. Evidence suggests that good antimicrobial stewardship can lead to less overall and inappropriate antimicrobial use, lower drug-related costs, reductions in Clostridium difficile-associated disease, and, in some studies, less emergence of antimicrobial resistance.

Safety in treatment of ventilator-associated pneumonia due to extensive drug-resistant Acinetobacter baumannii with aerosolized colistin in neonates: a preliminary report

BACKGROUND

Infections caused by extensive drug-resistant Acinetobacter baumannii (XDR-AB) have been increasingly observed and are associated with a high mortality rate. We present our experience using aerosolized colistin for the treatment of ventilator-associated pneumonia (VAP) due to XDR-AB in neonates.

METHODS

The clinical data of neonates who received aerosolized 4 mg per kg of colistin base twice daily as an adjunctive therapy for VAP caused by XDR-AB between July 2008 and September 2009 were retrospectively reviewed. The outcomes were compared with the neonates with VAP from XDR-AB in October 2006-September 2007 who did not receive aerosolized colistin.

RESULTS

During the study period, eight neonates (three preterm and five term neonates) with VAP caused by XDR-AB received aerosolized colistin. All isolated pathogens from the tracheobronchial specimens of the eight patients were XDR-AB susceptible to colistin only. Six patients received aerosolized colistin without concomitant intravenous colistin. All children were cured with eradication of XDR-AB from respiratory secretions. Seven patients survived and were discharged from the hospital, and one died from bacterial sepsis unrelated to the VAP episode. There were no clinical or laboratory adverse events related to aerosolized colistin. Compared to the seven neonates in the earlier period, the neonates who received aerosolized colistin had higher birth weight and gestational age, and lower mortality rate (13% vs. 71%, P=0.04).

CONCLUSIONS

Aerosolized colistin may be a useful adjunctive therapy in VAP due to XDR-AB. The use of aerosolized colistin in neonates should be investigated in a larger controlled study.

Clonal diversity of nosocomial epidemic Acinetobacter baumannii strains isolated in Spain

Acinetobacter baumannii is one of the major pathogens involved in nosocomial outbreaks. The clonal diversity of 729 epidemic strains isolated from 19 Spanish hospitals (mainly from intensive care units) was analyzed over an 11-year period. Pulsed-field gel electrophoresis (PFGE) identified 58 PFGE types that were subjected to susceptibility testing, rpoB gene sequencing, and multilocus sequence typing (MLST). All PFGE types were multidrug resistant; colistin was the only agent to which all pathogens were susceptible. The 58 PFGE types were grouped into 16 clones based on their genetic similarity (cutoff of 80%). These clones were distributed into one major cluster (cluster D), three medium clusters (clusters A, B, and C), and three minor clusters (clusters E, F, and G). The rpoB gene sequencing and MLST results reflected a clonal distribution, in agreement with the PFGE results. The MLST sequence types (STs) (and their percent distributions) were as follows: ST-2 (47.5%), ST-3 (5.1%), ST-15 (1.7%), ST-32 (1.7%), ST-79 (13.6%), ST-80 (20.3%), and ST-81 (10.2%). ST-79, ST-80, and ST-81 and the alleles cpn60-26 and recA29 are described for the first time. International clones I, II, and III were represented by ST-81, ST-2, and ST-3, respectively. ST-79 and ST-80 could be novel emerging clones. This work confirms PFGE and MLST to be complementary tools in clonality studies. Here PFGE was able to demonstrate the monoclonal pattern of most outbreaks, the inter- and intrahospital transmission of bacteria, and their endemic persistence in some wards. MLST allowed the temporal evolution and spatial distribution of Spanish clones to be monitored and permitted international comparisons to be made.

Confronting multidrug-resistant Acinetobacter baumannii: a review

Multidrug-resistant Acinetobacter baumannii (MDR-AB) infections are difficult to treat owing to the extremely limited armamentarium. The present review reports all available treatment options against MDR-AB, including single molecules, combination schemes, and alternative modes of antimicrobial administration. Additionally, a group of recently reported peptides with anti-MDR-AB activity is described.

Multidrug-resistant Gram-negative bacteria: how to treat and for how long

The emergence of multidrug-resistant (MDR) Gram-negative bacilli creates a big problem for the treatment of nosocomial infections. As the pharmaceutical pipeline wanes, the only therapeutic options are two revived antibacterials (colistin and fosfomycin), a newer one (tigecycline) and an early-phase neoglycoside (ACHN-490). Polymyxins, known since 1947, are mostly represented by polymyxin E (colistin), which has recently gained a principal position in the management of the most difficult-to-treat MDR Gram-negative pathogens -Pseudomonas aeruginosa, Acinetobacter baumannii and Klebsiella pneumoniae. However, despite promising therapeutic results in 59-75% of cases, the reported studies share common drawbacks, i.e. the absence of a control group, their retrospective nature, variable dosing and duration of therapy, simultaneous administration of other antibiotics in >70% and a lack of resistance development monitoring. The necessity for well-designed prospective clinical trials is therefore urgent. Fosfomycin is active in vitro against MDR Enterobacteriaceae, including a high proportion of P. aeruginosa; however, clinical experience is lacking with the parenteral formulation in MDR infection and on the best combinations to prevent resistance development. Tigecycline, which is active against MDR Enterobacteriaceae and A. baumannii, has shown satisfactory clinical experience. However, dosage adjustment is required because of low blood levels. ACHN-490, which has promising in vitro activity against MDR K. pneumoniae, is still in early phase II trials in urinary tract infections. Meanwhile, the strict application of infection control measures is the cornerstone of nosocomial infection prevention, and antibiotic stewardship, exemplified by appropriate duration of therapy and de-escalation policies, should not be overlooked.

Characterization of clonal strains of Pseudomonas aeruginosa isolated from cystic fibrosis patients in Ontario, Canada

Pseudomonas aeruginosa is an opportunistic pathogen that can form biofilms in the lungs and airways of cystic fibrosis (CF) patients, resulting in chronic endobronchial infection. Two clonal strains of P. aeruginosa, named type A and type B, have recently been identified and have been found to infect more than 20% of CF patients in Ontario, Canada. In this study, 4 type A and 4 type B isolates retrieved from 8 CF patients in Ontario, Canada, were characterized. All 8 isolates grew well in rich medium and formed biofilms in vitro. Antibiotic resistance profiles of bacteria grown in biofilms and planktonic culture were studied via minimal bactericidal concentration assays for tobramycin, gentamicin, and ciprofloxacin. Compared to laboratory strains of P. aeruginosa, all 8 isolates showed increased resistance to all antibiotics studied in both biofilm and planktonic assays. Gene expression analysis of mexX, representing the MexXY-OprM efflux pump, and mexA, representing MexAB-OprM, revealed that these genes were up-regulated in the 8 clinical isolates. These results suggest clonal type A and type B isolates of P. aeruginosa isolated from CF patients in Ontario, Canada, show a multidrug resistance pattern that can be partially explained as being due to the increased expression of common antibiotic efflux systems.

Antimicrobial susceptibility of intra-abdominal gram-negative bacilli from Europe: SMART Europe 2008

As part of the worldwide Study for Monitoring Antimicrobial Resistance Trends (SMART), a total of 3,030 clinical isolates of gram-negative bacilli from intra-abdominal infections were collected from 43 hospital centres from 13 European countries during 2008. Of 51 species, the most commonly isolated species were Escherichia coli (49.3%), followed by Klebsiella pneumoniae (10.5%) and Pseudomonas aeruginosa (8.6%). Respectively, 17.9%, 11.6%, 5.5% and 4.5% of K. pneumoniae, E. coli, Proteus mirabilis and K. oxytoca were extended-spectrum beta-lactamase (ESBL)-positive. All isolates were tested using a panel of 12 antimicrobial agents, and susceptibilities were determined using European Committee on Antimicrobial Susceptibility Testing (EUCAST) clinical breakpoints. The most active agents against the study isolates (including those producing ESBLs) were amikacin, ertapenem and imipenem. Overall, with the exception of the carbapenems, most agents exhibited dramatically reduced susceptibilities against ESBL-positive and multi-drug-resistant isolates.

Postgenomic strategies in antibacterial drug discovery

During the last decade the field of antibacterial drug discovery has changed in many aspects including bacterial organisms of primary interest, discovery strategies applied and pharmaceutical companies involved. Target-based high-throughput screening had been disappointingly unsuccessful for antibiotic research. Understanding of this lack of success has increased substantially and the lessons learned refer to characteristics of targets, screening libraries and screening strategies. The ‘genomics’ approach was replaced by a diverse array of discovery strategies, for example, searching for new natural product leads among previously abandoned compounds or new microbial sources, screening for synthetic inhibitors by targeted approaches including structure-based design and analyses of focused libraries and designing resistance-breaking properties into antibiotics of established classes. Furthermore, alternative treatment options are being pursued including anti-virulence strategies and immunotherapeutic approaches. This article summarizes the lessons learned from the genomics era and describes discovery strategies resulting from that knowledge.

Changes in the incidences of multidrug-resistant and extensively drug-resistant organisms isolated in a military medical center

BACKGROUND

Multidrug-resistant (MDR) Acinetobacter baumannii and Pseudomonas aeruginosa have emerged as the causes of nosocomial infections in critically ill patients.

OBJECTIVE

To characterize the incidence of these MDR bacteria over time in the military healthcare system, comparing isolates recovered from overseas combat casualties with isolates recovered from local military and civilian patients.

METHODS

Retrospective electronic records review of culture and/or susceptibility testing results of patients admitted to a military level I trauma center in San Antonio, Texas, during the period from January 2001 through December 2008. Multidrug resistance was defined as the first isolated organism resistant to 3 or more classes of antimicrobial agents.

RESULTS

Over time, the percentage of MDR A. baumannii isolates increased from 4% to 55%, whereas the percentage of MDR P. aeruginosa isolates increased from 2% to 8%. Respiratory tract specimens had a higher percentage of MDR A. baumannii isolates (49%), compared with specimens obtained from blood (30%), wound sites (24%), or urine (19%). No difference in the percentages of MDR P. aeruginosa isolates was observed with regard to source of specimen. The percentage of MDR A. baumannii isolates recovered was higher among patients who had been deployed overseas (52%) than among local patients (20%). When isolates recovered from patients in the burn intensive care unit (53% of MDR A. baumannii isolates) were removed from analysis, the percentage of MDR A. baumannii isolates decreased from 38% to 30% while the percentage of MDR P. aeruginosa isolates remained unaffected.

CONCLUSION

The percentage of MDR A. baumannii isolates increased in this facility among combat casualties and among local patients, which indicates nosocomial transmission; however, there was no significant increase in the percentage of MDR P. aeruginosa isolates. Isolated changes in the MDR pathogens within a facility can occur. Possible interventions to limit the spread of these organisms could include implementing aggressive infection control practices, controlling antibiotic use, and using active culture surveillance.

Prevalence of antimicrobial resistance among gram-negative isolates in an adult intensive care unit at a tertiary care center in Saudi Arabia

BACKGROUND AND OBJECTIVES

Patients in the ICU have encountered an increasing emergence and spread of antibiotic-resistant pathogens. We examined patterns of antimicrobial susceptibility in gram-negative isolates to commonly used drugs in an adult ICU at a tertiary care hospital in Riyadh, Saudi Arabia.

METHODS

A retrospective study was carried out of gram-negative isolates from the adult ICU of King Fahad National Guard Hospital (KFNGH) between 2004 and 2009. Organisms were identified and tested by an automated identification and susceptibility system, and the antibiotic susceptibility testing was confirmed by the disk diffusion method.

RESULTS

The most frequently isolated organism was Acinetobacter baumannii, followed by Pseudomonas aeruginosa, Escherichia coli, Klebsiella pnemoniae, Stenotrophomonas maltophilia, and Enterobacter. Antibiotic susceptibility patterns significantly declined in many organisms, especially A baumannii, E coli, S marcescens, and Enterobacter. A baumannii susceptibility was significantly decreased to imipenem (55% to 10%), meropenem (33% to 10%), ciprofloxacin (22% to 10%), and amikacin (12% to 6%). E coli susceptibility was markedly decreased (from 75% to 50% or less) to cefuroxime, ceftazidime, cefotaxime, and cefepime. S marcescens susceptibility was markedly decreased to cefotaxime (100% to 32%), ceftazidime (100% to 35%), and cefepime (100% to 66%). Enterobacter susceptibility was markedly decreased to ceftazidime (34% to 5%), cefotaxime (34% to 6%), and pipracillin-tazobactam (51% to 35%). Respiratory samples were the most frequently indicative of multidrug-resistant pathogens (63%), followed by urinary samples (57%).

CONCLUSION

Antimicrobial resistance is an emerging problem in the KFNGH ICU, justifying new more stringent antibiotic prescription guidelines. Continuous monitoring of antimicrobial susceptibility and strict adherence to infection prevention guidelines are essential to eliminate major outbreaks in the future.

Managing antimicrobial resistance in intensive care units

The challenges in managing patients with infection in the intensive care unit are increased in an era where there are dwindling antimicrobial choices for multidrug-resistant pathogens. Clinicians in the intensive care unit must balance between choosing appropriate antimicrobial treatment for patients with suspected infection and utilizing antimicrobials in a judicious fashion. Improving antimicrobial utilization is a critical component to reducing antimicrobial resistance. Although providing effective antimicrobial therapy and improving antimicrobial utilization may seem to be competing goals, there are effective strategies to accomplish both. Antimicrobial stewardship programs provide an organized way to implement these strategies and can enhance the intensive care unit physician's success in improving patient outcomes and combating antimicrobial resistance in the intensive care unit.

Colistin administration to pediatric and neonatal patients

Emergence of multidrug-resistant Gram-negative nosocomial pathogens has led to resurgence of colistin use. Safety and efficacy data regarding colistin use in pediatric patients are sparse, while optimal dosage has not been defined. We present a case series of neonates and children without cystic fibrosis treated with various doses of colistin intravenously. The records of patients who received colistin in a tertiary-care hospital from January 2007 to March 2009 were reviewed. Thirteen patients (median age 5 years, range 22 days to 14 years) received 19 courses of colistin as treatment of pneumonia, central nervous system infection, bacteremia, or complicated soft tissue infection. The isolated pathogens were Acinetobacter baumannii, Enterobacter cloacae, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia. Daily dose of colistin (colistimethate) ranged between 40,000 and 225,000 IU/kg. Duration of administration ranged from 1 to 133 days. Other antimicrobials were co-administered in 18/19 courses. Increase of serum creatinine in one patient was associated with co-administration of colistin and gentamicin. Sixteen of 19 courses had a favorable outcome, and only two of the three deaths were infection-related. Colistin intravenous administration appears well tolerated even at higher than previously recommended doses and of prolonged duration.

Antibiotic discovery in the twenty-first century: current trends and future perspectives

New antibiotics are necessary to treat microbial pathogens that are becoming increasingly resistant to available treatment. Despite the medical need, the number of newly approved drugs continues to decline. We offer an overview of the pipeline for new antibiotics at different stages, from compounds in clinical development to newly discovered chemical classes. Consistent with historical data, the majority of antibiotics under clinical development are natural products or derivatives thereof. However, many of them also represent improved variants of marketed compounds, with the consequent risk of being only partially effective against the prevailing resistance mechanisms. In the discovery arena, instead, compounds with promising activities have been obtained from microbial sources and from chemical modification of antibiotic classes other than those in clinical use. Furthermore, new natural product scaffolds have also been discovered by ingenious screening programs. After providing selected examples, we offer our view on the future of antibiotic discovery.

Activity of topical antimicrobial agents against multidrug-resistant bacteria recovered from burn patients

BACKGROUND

Topical antimicrobials are employed for prophylaxis and treatment of burn wound infections despite no established susceptibility breakpoints, which are becoming vital in an era of multidrug-resistant (MDR) bacteria. We compared two methods of determining topical antimicrobial susceptibilities.

METHODS

Isolates of Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus (MRSA), extended spectrum beta-lactamase (ESBL) producing Klebsiella pneumoniae, and Acinetobacter baumanii-calcoaceticus (ABC) from burn patients were tested using broth microdilution and agar well diffusion to determine minimum inhibitory concentrations (MICs) and zones of inhibition (ZI). Isolates had systemic antibiotic resistance and clonality determined. MDR included resistance to antibiotics in three or more classes.

RESULTS

We assessed 22 ESBL-producing K. pneumoniae, 20 ABC (75% MDR), 20 P. aeruginosa (45% MDR), and 20 MRSA isolates. The most active agents were mupirocin for MRSA and mafenide acetate for the gram-negatives with moderate MICs/ZI found with silver sulfadiazene, silver nitrate, and honey. MDR and non-MDR isolates had similar topical resistance. There was no clonality associated with resistance patterns.

CONCLUSION

Despite several methods to test bacteria for topical susceptibility, no defined breakpoints exist and standards need to be established. We recommend continuing to use silver products for prophylaxis against gram-negatives and mafenide acetate for treatment, and mupirocin for MRSA.