Antimicrobial resistance: factors and outcomes

Burden of severe infections due to carbapenem-resistant pathogens in intensive care unit

Intensive care units (ICU) for various reasons, including the increasing age of admitted patients, comorbidities, and increasingly complex surgical procedures (e.g., transplants), have become "the epicenter" of nosocomial infections, these are characterized by the presence of multidrug-resistant organisms (MDROs) as the cause of infection. Therefore, the perfect match of fragile patients and MDROs, as the cause of infection, makes ICU mortality very high. Furthermore, carbapenems were considered for years as last-resort antibiotics for the treatment of infections caused by MDROs; unfortunately, nowadays carbapenem resistance, mainly among Gram-negative pathogens, is a matter of the highest concern for worldwide public health. This comprehensive review aims to outline the problem from the intensivist's perspective, focusing on the new definition and epidemiology of the most common carbapenem-resistant MDROs (Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacterales) to emphasize the importance of the problem that must be permeating clinicians dealing with these diseases.

Occurrence and Multidrug Resistance in Strains of Listeria monocytogenes Recovered from the Anaerobic Co-Digestion Sludge Contained in a Single Stage Steel Biodigester: Implications for Antimicrobial Stewardship

L. monocytogenes is a zoonotic foodborne pathogen with inherent adaptability to tolerate environmental and physiological stresses, thereby causing severe disease outbreaks. Antibiotic resistant foodborne pathogens are a challenge to the food industry. A total of 18 samples were pooled from a bio-digester co-digesting swine manure/pinewood sawdust, and evaluated for the occurrence of bacterium plus total viable counts using the spread plate method. The recovered bacterial isolates were presumptively identified by growth on selective medium and confirmed by biochemical characterisation, leading to the isolation of 43 L. monocytogenes. The isolates were characterized based on their susceptibility to antibiotics via the Kirby-Bauer disc diffusion technique against a panel of 14 antibiotics. Equally, the multiple antibiotic resistance (MAR) index was calculated, and MAR phenotypes generated. The bacterial counts were between 102 and104 cfu/mL. Complete susceptibility (100%) was demonstrated to ampicillin, gentamicin and sulfamethoxazole, which are the drugs of choice in the treatment of listeriosis. In addition, intermediate sensitivity occurred at 25.58% to cefotaxime, and the highest resistance (51.16%) was exhibited against nalidixic acid. The MAR index ranged from 0 to 0.71. Overall, 41.86% of the Listeria isolates displayed multidrug resistance, with 18 different MAR phenotypes, demonstrating CIP, E, C, TET, AUG, S, CTX, NA, AML, NI as the greatest MAR phenotype. It can be concluded that the isolates yielding MAR > 0.2 originated from the farm, where antibiotics had been in routine use. Therefore, strict monitoring of antibiotics use in the farm is crucial to mitigate further increase in antibiotic resistance amongst these bacterial isolates.

High Carriage of Extended-Spectrum, Beta Lactamase-Producing, and Colistin-Resistant Enterobacteriaceae in Tibetan Outpatients with Diarrhea

Antibiotic-resistant bacteria (ARB) and antibiotic-resistance genes (ARGs) have been detected in human-impacted habitats, especially in densely populated cities. The Qinghai–Tibet Plateau is located far from the heavily populated regions of China, and Tibetan residents have distinct dietary habits and gut microbes. Antibiotic-resistance monitoring in the Tibetan population is rare. Here, we collected stool samples from Tibetan outpatients with diarrhea. From 59 samples, 48 antibiotic-resistant Enterobacteriaceae isolates were obtained, including 19 extended-spectrum beta lactamase (ESBL)-producing isolates from 16 patients and 29 polymyxin-resistant isolates from 22 patients. Either ESBL or mcr genes were found in 17 Escherichia coli isolates, approximately 58.8% of which were multidrug-resistant, and ten incompatible plasmid types were found. The gene bla_CTX-M was a common genotype in the ESBL-producing E. coli isolates. Four E. coli isolates contained mcr-1. The same mcr-1-carrying plasmid was found in distinct E. coli isolates obtained from the same sample, thus confirming horizontal transmission of mcr-1 between bacteria. Genomic clustering of E. coli isolates obtained from Lhasa, with strains from other regions providing evidence of clone spreading. Our results reveal a strong presence of ARB and ARGs in Tibetan outpatients with diarrhea, implying that ARB and ARGs should be monitored in the Tibetan population.

Lipophilic Ga Complex with Broad-Spectrum Antimicrobial Activity and the Ability to Overcome Gallium Resistance in both Pseudomonas aeruginosa and Staphylococcus aureus

Antibiotic resistance (AR) necessitates the discovery of new antimicrobials with alternative mechanisms of action to those employed by conventional antibiotics. One such strategy utilizes Ga³⁺ to target iron metabolism, a critical process for survival. Still, Ga-based therapies are generally ineffective against Gram-positive bacteria and promote Ga resistance. In response to these drawbacks, we report a lipophilic Ga complex, [Ga₂L₃(bpy)₂] (L = 2,2'-bis(3-hydroxy-1,4-naphthoquinone; bpy = 2,2'-bipyridine)), effective against drug-resistant Pseudomonas aeruginosa (DRPA; minimum inhibitory concentration, MIC = 10 μM = 14.8 μg/mL) and methicillin-resistant Staphylococcus aureus (MRSA, MIC = 100 μM = 148 μg/mL) without iron-limited conditions. Importantly, [Ga₂L₃(bpy)₂] shows noticeably delayed and decreased resistance in both MRSA and DRPA, with only 8× MIC in DRPA and none in MRSA after 30 passages. This is likely due to the dual mode of action afforded by Ga (disruption of iron metabolism) and the ligand (reactive oxygen species production). Overall, [Ga₂L₃(bpy)₂] demonstrates the utility of lipophilic metal complexes with multiple modes of action in combatting AR in Gram-positive and Gram-negative bacteria.

Bacteriostatic and Bactericidal Activities of Camel Lactoferrins Against Salmonella enterica Serovar Typhi

Lactoferrin is an iron-binding glycoprotein present in various secretions (e.g., milk, tears, saliva, pancreatic juice), which performs multiple functions, with one of them being the antimicrobial defense. Purified camel lactoferrins (cLfs) from different Saudi camel clans, as well as human and bovine lactoferrins (hLf or bLf) were tested as antimicrobial agents against Salmonella enterica serovar Typhi (S. Typhi). All cLfs showed superior antibacterial potentials relative to hLf or bLf, while there was no noticeable difference in the antimicrobial capabilities between the cLfs from different camel clans. We observed synergy between the inhibitory activities of Lfs and antibiotics against bacterial growth. Expression of numerous bacterial proteins was affected by the treatment with Lf and its combinations, giving insight into the molecular mechanisms of the Lf action. Furthermore, several bacterial proteins were shown to interact with cLf-biotin. Scanning and transmission electron microscopy revealed the presence of obvious extracellular and intracellular changes after S. Typhi treatment by antibiotic (carbenicillin) or cLf alone, and in combination. The effects of antibiotics and Lf were synergistic, supporting the potential of the use of Lf-antibiotic combinations.

Predictive factors for sepsis by carbapenem resistant Gram-negative bacilli in adult critical patients in Rio de Janeiro: a case-case-control design in a prospective cohort study

Background

Studies have investigated risk factors for infections by specific species of carbapenem-resistant Gram-negative bacilli (CR-GNB), but few considered the group of GNB species and most of them were performed in the setting of bacteremia or hospital infection. This study was implemented to identify risk factors for sepsis by CR- and carbapenem-susceptible (CS) GNB in intensive care unit (ICU) patients to improve management strategies for CR-GNB sepsis.

Methods

We developed a case-case-control study from a prospective cohort of patients with systemic inflammatory response syndrome (SIRS), sepsis-2 or sepsis-3 criteria in which blood and other sample cultures were collected and antimicrobial therapy was instituted, in an adult clinical-surgical ICU, at tertiary public hospital in Rio de Janeiro, from August 2015 through March 2017.

Results

Among the total of 629 ICU admissions followed by 7797 patient-days, after applying inclusion and exclusion criteria we identified 184 patients who developed recurrent or single hospital-acquired sepsis. More than 90% of all evaluable cases of sepsis and 87% of control group fulfilled the modified sepsis-3 definition. Non-fermenting bacilli and ventilator-associated pneumonia predominated as etiology and source of CR-GNB sepsis. While Enterobacteriaceae and intra-abdominal surgical site plus urinary-tract infections prevailed in CS-GNB than CR-GNB sepsis. Carbapenemase production was estimated in 76% of CR-GNB isolates. Multivariate logistic regression analysis revealed previous infection (mostly hospital-acquired bacterial infection or sepsis) (OR = 4.28; 95% CI 1.77–10.35), mechanical ventilation (OR = 4.21; 95% CI 1.17–15.18), carbapenem use (OR = 3.42; 95% CI 1.37–8.52) and length of hospital stay (OR = 1.03; 95% CI 1.01–1.05) as independent risk factors for sepsis by CR-GNB. While ICU readmission (OR = 6.92; 95% CI 1.72–27.78) and nosocomial diarrhea (OR = 5.32; 95% CI 1.07–26.45) were factors associated with CS-GNB sepsis.

Conclusions

The investigation of recurrent and not only bacteremic episodes of sepsis was the differential of this study. The results are in agreement with the basic information in the literature. This may help improve management strategies and future studies on sepsis by CR-GNB.

Antibiotic Use in the Intensive Care Unit: Optimization and De-Escalation

Appropriate antimicrobial therapy is essential to ensuring positive patient outcomes. Inappropriate or suboptimal utilization of antibiotics can lead to increased length of stay, multidrug-resistant infections, and mortality. Critically ill intensive care patients, particularly those with severe sepsis and septic shock, are at risk of antibiotic failure and secondary infections associated with incorrect antibiotic use. Through the initiation of active empiric antibiotic therapy based upon local susceptibilities, daily evaluation of signs and symptoms of infection and narrowing of antibiotic therapy when feasible, providers can streamline the treatment of common intensive care unit (ICU) infections. Optimizing antibiotic dosing through prolonged infusions can be beneficial in intensive care populations with altered pharmacokinetics. Antimicrobial stewardship teams can assist ICU providers in managing and implementing these tactics. This review will discuss the current literature on antibiotic use in the ICU applying antimicrobial stewardship strategies. Based upon the most recent evidence, ICUs would benefit from employing empiric guidelines for antibiotic use, collecting appropriate specimens and implementing molecular diagnostics, optimizing the dosing of antibiotics, and reducing the duration of total therapy. These strategies for antibiotic use have the potential to enhance patient care while preventing adverse outcomes.

Antimicrobial resistance in clinical Escherichia coli isolates from poultry and livestock, China

Poultry and livestock are the most important reservoirs for pathogenic Escherichia coli and use of antimicrobials in animal farming is considered the most important factor promoting the emergence, selection and dissemination of antimicrobial-resistant microorganisms. The aim of our study was to investigate antimicrobial resistance in E. coli isolated from food animals in Jiangsu, China. The disc diffusion method was used to determine susceptibility to 18 antimicrobial agents in 862 clinical isolates collected from chickens, ducks, pigs, and cows between 2004 and 2012. Overall, 94% of the isolates showed resistance to at least one drug with 83% being resistance to at least three different classes of antimicrobials. The isolates from the different species were most commonly resistant to tetracycline, nalidixic acid, sulfamethoxazole, trimethoprim/sulfamethoxazole and ampicillin, and showed increasing resistance to amikacin, aztreonam, ceftazidime, cefotaxime, chloramphenicol, ciprofloxacin. They were least resistant to amoxicillin/clavulanic acid (3.4%) and ertapenem (0.2%). MDR was most common in isolates from ducks (44/44, 100%), followed by chickens (568/644, 88.2%), pigs (93/113, 82.3%) and cows (13/61, 21.3%). Our finding that clinical E. coli isolates from poultry and livestock are commonly resistant to multiple antibiotics should alert public health and veterinary authorities to limit and rationalize antimicrobial use in China.

Detection of multidrug resistant (MDR) bacteria in untreated waste water disposals of hospitals in Dhaka City, Bangladesh

BACKGROUND

Emergence of MDR bacteria is a global problem and a major burden for treatment of various infectious diseases. This study was performed to detect antibiotic resistant bacteria in untreated hospital waste.

METHOD

Waste water samples were collected from sewerage disposal points of two renowned hospital of Dhaka city and a total of 59 Escherichia coli and 29 Klebsiella pneumonia isolates were isolated. Antibiotic susceptibility were measured by disc diffusion method.

RESULTS

Resistance among E. coli and K. pneumoniae to 10 frequently used antibiotic tested were respectively as follows: cefotaxime (CTX) 48 and 45%; ceftazidime (CAZ) 40 and 38%; ampicillin (AMP) 71 and 100%; streptomycin (S) 50 and 34%; sulfamethoxazole-trimethoprim (SXT) 58 and 28%; ciprofloxacin (CIP) 71 and 48%; kanamycin (K) 38 and 10%; chloramphenicol (C) 28 and 10%; gentamycin (CN) 19 and 16% and imipenem (IPM) 12 and 7%. Results also demonstrate that the sites that were at the disposal point of hospital waste have higher degree of resistance. High degree of resistance was observed when 23 high-resistant E. coli isolates were further tested with 15 additional antibiotics.

CONCLUSION

This study revealed a significant rise of MDR bacteria in the hospital waste and underscore necessity of hospital waste treatment.

Antibiotic resistance patterns of microorganisms isolated from nephrology and kidney transplant wards of a referral academic hospital

OBJECTIVE

Antibiotic use pattern and emergence of resistant bacteria are major concerns in clinical settings. This study aimed to detect common bacteria and their antibiotic sensitivity patterns in nephrology and kidney transplant wards.

METHODS

This 1-year, observational study was performed in the nephrology and kidney transplant wards of Imam Khomeini Hospital Complex, Tehran, Iran. All patients treated with antimicrobial agents for confirmed or suspected infections were included. Their demographic, clinical, and laboratory data (including biological media used for microbial culture, growth organisms, and antibiograms) were collected. Adherence of antimicrobial regimen to standard guidelines was also assessed.

FINDINGS

About half of the patients received antibiotic. The most common infecting bacteria were Escherichia coli followed by Enterococcus sp. and Staphylococcus aureus. E. coli showed high rate of sensitivity to carbapenems and nitrofurantoin and high rate of resistance to co-trimoxazole and ciprofloxacin. Enterococcus sp. in both wards had high rate of resistance to ampicillin and were all sensitive to linezolid. Unlike to the nephrology ward, more than 50% of Enterococcus sp. from kidney transplant ward was resistant to vancomycin. The most common type of S. aureus in this nephrology ward was methicillin-resistant S. aureus (MRSA). Most commonly-prescribed antibiotics were carbapenems followed by vancomycin, ciprofloxacin, and ceftriaxone. Antibiotic regimens were 75% and 83%, 85% and 91%, and 80% and 87% compatible with international guidelines in antibiotic types, dosages, and treatment durations, respectively, in nephrology and kidney transplant wards, respectively.

CONCLUSION

MRSA, fluoroquinolone-resistant E. coli, and vancomycin resistant Enterococcus species are major threats in nephrology and kidney transplant wards. Most commonly-prescribed antibiotics were carbapenems that necessitate providing internal guidelines by the teamwork of clinical pharmacist, infectious disease specialists, and nephrologists to avoid the widespread use of broad-spectrum antibiotics.

Development of Antibiotic Resistance during Simulated Treatment of Pseudomonas aeruginosa in Chemostats

During treatment of infections with antibiotics in critically ill patients in the intensive care resistance often develops. This study aims to establish whether under those conditions this resistance can develop de novo or that genetic exchange between bacteria is by necessity involved. Chemostat cultures of Pseudomonas aeruginosa were exposed to treatment regimes with ceftazidime and meropenem that simulated conditions expected in patient plasma. Development of antibiotic resistance was monitored and mutations in resistance genes were searched for by sequencing PCR products. Even at the highest concentrations that can be expected in patients, sufficient bacteria survived in clumps of filamentous cells to recover and grow out after 3 to 5 days. At the end of a 7 days simulated treatment, the minimal inhibitory concentration (MIC) had increased by a factor between 10 and 10,000 depending on the antibiotic and the treatment protocol. The fitness costs of resistance were minimal. In the resistant strains, only three mutations were observed in genes associated with beta-lactam resistance. The development of resistance often observed during patient treatment can be explained by de novo acquisition of resistance and genetic exchange of resistance genes is not by necessity involved. As far as conclusions based on an in vitro study using P. aeruginosa and only two antibiotics can be generalized, it seems that development of resistance can be minimized by treating with antibiotics in the highest concentration the patient can endure for the shortest time needed to eliminate the infection.

Antimicrobial resistance pattern of Gram-positive bacteria during three consecutive years at the nephrology ward of a tertiary referral hospital in Shiraz, Southwest Iran

Objective:

The aim of the present study was to determine the pattern of antimicrobial resistance of Gram-positive bacteria during three consecutive years at the nephrology ward of Namazi Hospital in Shiraz, Southwest of Iran.

Methods:

During a 3-year period from 2013 to 2015, data of all biological samples of hospitalized patients at the adult nephrology ward of Namazi Hospital were sent to the central laboratory for identification of Gram-positive microorganisms and subsequently, their antimicrobial susceptibility testing by Kirby–Bauer disc diffusion method were analyzed in a retrospective manner.

Findings:

Coagulase-negative Staphylococci (CONS) (38.5%), Staphylococcus aureus (25.4%), and Enterococcus spp. (23.8%) were the most common isolated Gram-positive bacteria from all biological samples. All Enterococcus spp. isolates within the 3 years were resistant to oxacillin. The rate of vancomycin-resistant enterococci (VRE) increased from 40.63% in 2013 to 72.73% in 2015. Enterococcus spp. resistance rates to aminoglycosides during 3 years were above 85%. The frequencies of oxacillin-resistant S. aureus (ORSA) in 2013, 2014, and 2015 were 95.24%, 80.95%, and 36.36%, respectively. Two out of 11 (6.67%) S. aureus isolates were resistant to vancomycin. More than 90% of CONS were sensitive to vancomycin within the study period. The frequency of gentamicin-resistant CONS ranged from 40% to 57.14%.

Conclusion:

The rates of ORSA, VRE, and aminoglycoside-resistant CONS as well as Enterococcus spp. in our clinical setting were considerably high and concerning. These may be due to the failure or lack of infection control activities and antimicrobial selection pressure.

Risk Factor Analysis in Clinical Isolates of ESBL and MBL (Including NDM-1) Producing Escherichia coli and Klebsiella Species in a Tertiary Care Hospital

BACKGROUND

Extended-spectrum β-lactamase (ESBL) and metallo-β-lactamase (MBL) producing Gram negative organisms are emerging as a worldwide public health concern.

AIM

To elucidate risk factors for infection with ESBL and MBL (also NDM-1) producing E. coli and Klebsiella spp.

MATERIALS AND METHODS

A prospective observational study was conducted from November 2010 to March 2012. ESBL production was detected using ESBL E-test, MBL by MBL E-test and NDM-1 by polymerase chain reaction (PCR). Risk factors analysed includes age, sex, clinical specimen, type of infection, duration of hospital stay prior to collection of sample, admitting ward, antimicrobial susceptibility, previous antibiotics used, co-morbid illnesses like diabetes mellitus, immunodeficiency, low birth weight, respiratory/neurological/cardiac/haematological/liver diseases, malignancy, urinary or central venous catheter, ventilatory support, surgical procedures and dialysis.

STATISTICAL ANALYSIS

z-test or Fisher's exact test.

RESULTS

E. coli - ESBL producing isolates E. coli revealed female preponderance, equal incidence of hospital and community acquired infections, mostly from surgical wards, isolated from urine, age group among females >20-30 years and among males >28 days-1 year. They showed high resistance to cephalosporins, monobactam, penicillin but low resistance to carbapenems and aminoglycosides. Co-morbid conditions observed were surgery, urinary catheterisation, haematological disease, ventilatory support, diabetes mellitus and neurological disease. MBL producing strains were mainly from females, surgical wards, (including both NDM-1 isolates), hospital acquired infections, isolated from body fluids (NDM-1 positive), female genital tract specimen and urine (one NDM-1 positive). NDM-1 positive isolates belonged to age groups >5-10 year and >0-28 days and underwent surgery and urinary catheterisation. Klebsiella spp.- ESBL producing isolates showed female preponderance, hospital acquired infections, from surgical wards, high resistance levels to cephalosporins, fluoroquinolones, monobactam, but low levels to carbapenems, among males isolated from pus in age group >0-28 days and >28 days -1 year and among females from urine in >20-30 years, no significant difference when correlated with risk factors. MBL (NDM-1) producing isolates were mainly from females with age range 0 days to 70 years, mainly admitted to ICU/postoperative wards with urinary catheter in-situ, ventilatory support, surgery, diabetes mellitus, haematological and neurological disease.

CONCLUSION

Risk factors for infections due to ESBL and MBL producing Gram Negative Bacteria (GNB) should be clearly identified to reduce their spread and to optimise antibiotic use.

Multidrug-Resistant Organisms: Considerations in Antibiotic Selection and Administration

Managing infections caused by multidrug-resistant organisms is a significant clinical challenge. Multidrug-resistant organisms' treatment is complicated in the pediatric population because of the lack of primary data, treatment guidelines, rapidly changing pharmacokinetic/pharmacodynamic parameters, and fewer approved antibiotic indications and dosing guidance. Treatment decisions must incorporate available pediatric data, clinical experience, and careful extrapolation from adult data while considering the unique challenges faced by children with complicated infections.

Multi-drug resistant gram negative infections and use of intravenous polymyxin B in critically ill children of developing country: retrospective cohort study

Background

Patients in pediatric intensive care Units (PICU) are susceptible to infections with antibiotic resistant organisms which increase the morbidity, mortality and cost of care.

To describe the clinical characteristics and mortality in patients with Multi-Drug Resistant (MDR) gram negative organisms. We also report safety of Polymyxin B use in these patients.

Methods

Files of patients admitted in PICU of Aga Khan University Hospital, from January 2010 to December 2011, one month to 15 years of age were reviewed. Demographic and clinical features of patients with MDR gram negative infections, antibiotic susceptibility pattern of isolates, discharge disposition and adverse effects of Polymyxin B were recorded.

Results

A total of 44.8/1000(36/803) admitted patients developed MDR gram negative infections, of which 47.2%(17/36) were male, with mean age of 3.4 yrs(+/−4.16). Acinetobacter Species (25.5%) was the most frequently isolated MDR organisms followed by Klebsiella Pneumoniae (17%). Sensitivity of isolates was 100% to Polymyxin B, followed by Imipenem (50%), and piperacillin/tazobactem (45%). The crude mortality rate of patients with MDR gram negative infections was 44.4% (16/36). Fourteen of 36 patients received Polymyxin B and 57.1%; (8/14) of them were cured. Nephrotoxicity was observed in 21.4% (3/14) cases, none of the patients showed signs of neuropathy.

Conclusion

Our study highlights high rates of Carbapenem resistant gram negative isolates, leading to increasing use of Polymyxin B as the only drug to combat against these critically ill children. Therefore, we emphasizeon Stewardship of Antibiotics and continuous surveillance system as strategies in overall management of these critically ill children.

Integrated information visualization to support decision making for use of antibiotics in intensive care: design and usability evaluation

Overuse of antibiotics is a critical problem in intensive care today. The situation is further complicated by the extremely data-intensive environment with clinical data presented in distributed, often stand-alone information systems. To access and interpret all data is a complex and time-consuming technical and cognitive challenge. We propose a holistic integrated visualization in the form of a patient overview to support physicians in decision making for use of antibiotics at intensive care units. Special emphasis is put on analysis of work processes to identify information needs, the development of a visualization tool based on an integrated data model, and usability testing of the tool in combination with an eye-tracking technology. The visualization tool was highly rated in terms of user performance and preferences, and the analysis of users' visual patterns showed that different types of data visualization may benefit specialist and resident intensive care physicians depending on the task to be performed. A highly interactive tool for integrated information visualization could potentially increase the understanding of a patient's infection status and ultimately enhance decision making for the use of antibiotics.

Prevalence of tet genes mediating tetracycline resistance in Escherichia coli clinical isolates in Osun State, Nigeria

The occurrence of tetracycline resistance determinants in 203 Escherichia coli isolates recovered from clinical samples at three different hospitals in Nigeria between June 2009 and May 2010 was investigated. The isolates were subjected to standard procedures. Antibiotic susceptibility to a panel of eight antibiotics was also performed, and resistance genes were detected with the polymerase chain reaction (PCR) technique. One hundred and six E. coli isolates (52.2%) were obtained at LAUTECH Teaching Hospital Osogbo, 85 (41.9%) from OAUTHC Ile Ife and 12 (5.9%) from Osun State Hospital Asubiaro Osogbo. Result of the disk diffusion antibiotic susceptibility test showed 96.1% isolates to be resistant to ampicillin, 77.8% to tetracycline, 37.9% to cotrimoxazole, 38.4% to nalidixic acid, 20.7% to ofloxacin, 17.7% to ceftriaxone, 11.8% to gentamycin, and 2% to nitrofurantoin. One hundred and sixty two (79.9%) isolates had minimum inhibitory concentration (MIC) of tetracycline ≥ 128 μg/ml. The polymerase chain reaction (PCR) detected tetA gene in 89 (43.8%) isolates, tetB gene in 65 (32.0%), and both tetA and tetB genes in 9 (4.4%) isolates. The study demonstrated a relatively high level of gene mediated antibiotic resistance to tetracycline and other antibiotics in E. coli clinical isolates in Southwest region of Nigeria.

Investigating the impact of bisphosphonates and structurally related compounds on bacteria containing conjugative plasmids

Bacterial plasmids propagate through microbial populations via the directed process of conjugative plasmid transfer (CPT). Because conjugative plasmids often encode antibiotic resistance genes and virulence factors, several approaches to inhibit CPT have been described. Bisphosphonates and structurally related compounds (BSRCs) were previously reported to disrupt conjugative transfer of the F (fertility) plasmid in Escherichia coli. We have further investigated the effect of these compounds on the transfer of two additional conjugative plasmids, pCU1 and R100, between E. coli cells. The impact of BSRCs on E. coli survival and plasmid transfer was found to be dependent on the plasmid type, the length of time the E. coli were exposed to the compounds, and the ratio of plasmid donor to plasmid recipient cells. Therefore, these data indicate that BSRCs produce a range of effects on the conjugative transfer of bacterial plasmids in E. coli. Since their impact appears to be plasmid type-dependent, BSRCs are unlikely to be applicable as broad inhibitors of antibiotic resistance propagation.

Nosocomial Gram-positive antimicrobial susceptibility pattern at a referral teaching hospital in Tehran, Iran

Aims: The aim of the study was to evaluate epidemiology and susceptibility patterns of nosocomial Gram-positive infections in a referral teaching hospital. Methods: Over a 1 year period, Gram-positive microorganisms isolated from specimens of hospitalized patients with documented nosocomial infection underwent antimicrobial susceptibility testing using the disk diffusion test. In addition, possible risk factors for developing multidrug-resistant bacteria were evaluated. Results: During the study period, a total of 137 nosocomial infections were detected. Staphylococcus aureus was the most frequently isolated microorganism (56.2%), followed by Enterococcus spp. (21.9%) and Staphylococcus epidermidis (15.3%). All S. aureus strains were sensitive to vancomycin, teicoplanin, linezolid and chloramphenicol. More than 50% of enterococci strains were resistant to vancomycin and teicoplanin. Possible risk factors for multidrug resistance among isolated pathogens were history of antibiotic use and intubation of patient for mechanical ventilation. Conclusion: This study showed high rates of antimicrobial resistance among nosocomial Gram-positive pathogens, complicating antibiotic therapy and its outcomes.

Original submitted 26 March 2012; Revised submitted 27 April 2012

Interpreting culture and susceptibility data in critical care: perks and pitfalls

PROBLEM

The need for immediate, effective antimicrobial therapy in the critical care patient must be tempered by approaches which simultaneously minimize emergence of antimicrobial resistance. Ideally, therapy will successfully resolve clinical signs of infection, while eradicating infecting pathogens such that the risk of resistance is avoided. Increasing limitations associated with empirical antimicrobial choices direct the need for culture and susceptibility data as a basis of therapy. Even so, such in vitro data should be utilized within its limitations.

OBJECTIVES

To demonstrate the attributes and limitations of patient and population culture and susceptibility (pharmacodynamic) data in the selection of antimicrobial drugs and to demonstrate the design of individualized dosing regimens based on integration of pharmacodynamic (PD) and pharmacokinetic (PK) data.

DIAGNOSIS

Limitations in culture and susceptibility testing begin with sample collection and continue through drug selection and dose design. Among the challenges in interpretation is discrimination between pathogens and commensals. Properly collected samples are critical for generation of data relevant to the patient's infection. Data are presented as minimum inhibitory concentrations (MICs). The MIC facilitate selection of the most appropriate drug, particularly when considered in the context of antimicrobial concentrations achieved in the patient at a chosen dose. Integration of MIC data with key PK data yields the C(max):MIC important to efficacy of concentration-dependent drugs and T>MIC, which guides use of time-dependent drugs. These indices are then used to design dosing regimens that are more likely to kill all infecting pathogens. In the absence of patient MIC data, population data (eg, MIC(90)) may serve as a reasonable surrogate.

CONCLUSIONS

Properly collected, performed, and interpreted culture and susceptibility data are increasingly important in the selection of and design of dosing regimens for antimicrobial drugs. Integration of PK and PD data as modified by host and microbial factors supports a hit hard, exit fast approach to therapy that will facilitate efficacy while minimizing resistance.

Pharmacokinetic and pharmacodynamic parameters of antimicrobials: potential for providing dosing regimens that are less vulnerable to resistance

Whereas infections caused by multidrug-resistant micro-organisms are increasing worldwide, there are few new molecules, especially ones that are active against Gram-negative strains. There are extensive data showing that the administration of antimicrobials according to pharmacokinetic/pharmacodynamic parameters improves the possibility of a positive clinical outcome, particularly in severely ill patients. Evidence is growing that when pharmacokinetic/pharmacodynamic parameters are used to target not only clinical cure but also eradication, the spread of resistance will also be contained. The present paper summarizes the most relevant papers published in this field and provides some suggestions for dosing regimens that can be adopted in the clinical setting to limit the spread of resistance.

Management of antibiotic resistance in the intensive care unit setting

Over the past few decades, an alarming increase of infections caused by antibiotic-resistant pathogens, including methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus species, carbapenem-resistant Pseudomonas aeruginosa, extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella spp., and multidrug-resistant Acinetobacter spp., has been observed, particularly in intensive care units. For clinicians, the rising resistance rate observed in nosocomial pathogens, when coupled with the lack of effective antimicrobials, represents the real challenge in the therapeutic management of critically ill patients. The contribution of clinicians in minimizing the increasing trend of resistance is represented by reduction of the patients' exposure to antibiotics, which reduces the resistance-selecting pressure, and by avoiding unnecessary antibiotic treatments. Recent issues on strategies to minimize resistance development and to appropriately manage critically ill patients with infections caused by multidrug-resistant organisms in the intensive care unit setting are discussed in this article.

Structural plasticity and distinct drug-binding modes of LfrR, a mycobacterial efflux pump regulator

The TetR-like transcriptional repressor LfrR controls the expression of the gene encoding the Mycobacterium smegmatis efflux pump LfrA, which actively extrudes fluoroquinolones, cationic dyes, and anthracyclines from the cell and promotes intrinsic antibiotic resistance. The crystal structure of the apoprotein form of the repressor reveals a structurally asymmetric homodimer exhibiting local unfolding and a blocked drug-binding site, emphasizing the significant conformational plasticity of the protein necessary for DNA and multidrug recognition. Crystallographic and calorimetric studies of LfrR-drug complexes further confirm the intrinsic flexibility of the homodimer, which provides a dynamic mechanism to broaden multidrug binding specificity and may be a general property of transcriptional repressors regulating microbial efflux pump expression.

Decision support systems for antibiotic prescribing

PURPOSE OF REVIEW

To explore recent developments in computerized evidence-based guidelines and decision support systems that have been designed to improve the effectiveness and efficiency of antibiotic prescribing.

RECENT FINDINGS

The most frequently utilized decision support systems are electronic guidelines and protocols, especially for empirical selection of antibiotics. The majority of decision support systems result in improvement in clinical performance and, in at least half of the published trials, in patient outcomes. Despite the reported successes of individual applications, the safety of electronic prescribing systems in routine practice has been identified recently as an issue of potential concern. Bioinformatics-assisted prescribing may contribute to reducing the complexities of prescribing combinations of antimicrobials in the era of multidrug resistance.

SUMMARY

The reemerging interest in prescribing decision support reflects the recent change in emphasis from support for diagnostic decisions towards support for patient management and from systems targeting a broad range of clinical diagnoses to task specific and condition-specific decision aids.

Therapeutic applications of tigecycline in the management of complicated skin and skin structure infections

Complicated skin and skin structure infections encompass a diverse range of diseases frequently caused by Gram-positive pathogens, and most commonly by Staphylococcus aureus and Streptococcus pyogenes. Treatment of these infections represents a growing clinical challenge as increases in multi-drug-resistant organisms and cross-resistance to antimicrobial therapy have made empiric therapeutic choices more difficult, particularly for patients with known risk factors or who are immunocompromised. Complicating this issue has been the relative lack of new agents with antimicrobial potency against prevalent resistant species such as meticillin resistant S. aureus (MRSA). Tigecycline, a novel glycylcycline, is a broad-spectrum antibiotic with potent microbiological activity against the wide variety of organisms implicated in the aetiology of complicated skin and skin structure infections. Recent phase III clinical data confirm previous observations on the safety and efficacy of tigecycline for the treatment of complicated skin and skin structure infections. Tigecycline was shown to be non-inferior to combination vancomycin-aztreonam regimens and exhibited high clinical success rates. MIC(90) values for tigecycline were uniformly low for both susceptible and resistant pathogens. Adverse events were similar in incidence for both patient populations, with nausea and vomiting reported more frequently with tigecycline treated patients while rash and elevated liver transaminases were most commonly observed in the vancomycin-aztreonam treatment group. Tigecycline helps to address the urgent need for new antimicrobial agents to combat the emergence of multi-drug-resistant Gram-positive pathogens. Current clinical, microbiological and safety data support the use of tigecycline as a valuable therapeutic option in the treatment of complicated skin and skin structure infections.

Galanin message-associated peptide suppresses growth and the budded-to-hyphal-form transition of Candida albicans

The expression of the mRNA encoding galanin message-associated peptide (GMAP) in human keratinocytes is upregulated by lipopolysaccharides and exposure to Candida albicans. GMAP has growth-inhibiting activity against C. albicans and inhibits the budded-to-hyphal-form transition, establishing GMAP as a possible new component of the innate immune system.

Surgical critical care: from old boundaries to new frontiers

The surgical specialty of critical care has evolved into a field where the surgeon manages complex medical and surgical problems in critically ill patients. As a specialty, surgical critical care began when acutely ill surgical patients were placed in a designated area within a hospital to facilitate the delivery of medical care. As technology evolved to allow for development of increasingly intricate and sophisticated adjuncts to care, there has been recognition of the importance of physician availability and continuity of care as key factors in improving patient outcomes. Guidelines and protocols have been established to ensure quality improvement and are essential to licensing by state and national agencies. The modern ICU team provides continuous daily care to the patient in close communication with the primary operating physician. While the ultimate responsibility befalls the primary physician who performed the preoperative evaluation and operative procedure, the intensivist is expected to establish and enforce protocols, guidelines and patient care pathways for the critical care unit. It is difficult to imagine modern surgical ICU care without the surgical critical care specialist at the helm.

Antimicrobial resistance in critical care

Patients presenting with active infections or at increased risk for infections pose a significant challenge in critical care nursing. It is important for critical care nurses to use effective antimicrobial strategies in patient management to reduce the potential development of antimicrobial resistance. They should be involved actively in promoting patient management through development of research-based nursing guidelines and protocols.