Pathogens resistant to antimicrobial agents: epidemiology, molecular mechanisms, and clinical management

Augmenting Antimicrobial Resistance Surveillance: Rapid Detection of β-Lactamase-Expressing Drug-Resistant Bacteria through Sensitized Luminescence on a Paper-Supported Hydrogel

The emergence of antimicrobial resistance (AMR) in pathogenic bacteria, expedited by the overuse and misuse of antibiotics, necessitates the development of a rapid and pan-territorially accessible diagnostic protocol for resistant bacterial infections, which would not only enable judicious prescription of drugs, leading to infection control but also augment AMR surveillance. In this study, we introduce for the first time a "turn-on" terbium (Tb3+) photoluminescence assay supported on a paper-based platform for rapid point-of-care (POC) detection of β-lactamase (BL)-producing bacteria. We strategically conjugated biphenyl-4-carboxylic acid (BCA), a potent Tb3+ sensitizer, with cephalosporin to engineer a BL substrate CCS, where the energy transfer to terbium is arrested. However, BL, a major resistance element produced by bacteria resistant to β-lactam antibiotics, triggers a spontaneous release of BCA, empowering terbium sensitization within a supramolecular scaffold supported on paper. The remarkable optical response facilitates quick assessment with a binary answer, and the time-gated signal acquisition ensues improved sensitivity with a detection limit as low as 0.1 mU/mL. Furthermore, to ensure accessibility, particularly in resource-limited areas, we have developed an in loco imaging device as an affordable alternative to high-end instruments. The integration of the assay with the device readily identified the BL-associated drug-resistant strains in the mimic urinary tract infection samples within 2 h, demonstrating its excellent potential for in-field translation. We believe that this rapid paper-based POC assay, coupled with the in loco device, can be deployed anywhere, especially in developing regions, and will enable extensive surveillance on antibiotic-resistant infections.

Effects of Silybum marianum L. Seed Extracts on Multi Drug Resistant (MDR) Bacteria

Wound infections became a great challenge, especially after the emergence of bacterial resistance to commonly used antibiotics. Medicinal plants can be the source of alternative antibacterial agents effective against multi drug resistant (MDR) bacteria. This research aimed to evaluate the effectiveness of different Silybum marianum seed extracts in fighting MDR bacteria that infect wounds. First, thirty purified bacterial cultures obtained from superficial, infected wounds were subjected to antibiotic sensitivity tests. The selected MDR isolates were then used to test the antimicrobial effects of different S. marianum seed extracts. The most potent extract was evaluated for its impact on the ultrastructure of the cells of sensitive bacterial isolates using transmission electron microscopy (TEM). The bioactive ingredients of this extract were analyzed by means of gas chromatography-mass spectroscopy (GC-MS). Then, in-silico absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties were predicted for the main components. The results indicated that four out of 30 bacterial isolates were considered MDR bacteria. Primary morphological features of colonies, secondary (automatic) identification using the Biomerieux Vitek 2 System, and 16S rRNA sequencing of the four isolates confirmed that they represent Staphylococcus aureus, Stenotrophomonas maltophilia, Klebsiella pneumoniae, and Escherichia coli. Among different extracts of S. marianum seeds, ethanol extract showed the strongest inhibitory effect on both Gram-positive and Gram-negative bacteria, with minimum inhibitory concentration (MIC) values between 9.375 and 1.172 mg/mL. However, at concentrations four times higher, this extract was unable to kill bacterial cells, indicating that it had a bacteriostatic effect on the tested MDR strains. TEM revealed denaturation and distorted cell ultrastructure in S. aureus and S. maltophilia after exposure to ethanol extract. In addition, GC-MS analysis of the ethanol extract identified nine compounds known to have important biological activities, and ADMET analysis showed good drug-likeness for two of these compounds. Consequently, S. marianum seeds could be a good source of alternative bacteriostatic agents effective against MDR bacterial strains that cause wound infections.

Human Hair Keratin-Based Hydrogels in Regenerative Medicine: Current Status and Future Directions

Regenerative medicine (RM) is a multidisciplinary field that utilizes the inherent regenerative potential of human cells to generate functionally and physiologically acceptable human cells, tissues, and organs in vivo or ex vivo. An appropriate biomaterial scaffold with desired physicochemical properties constitutes an important component of a successful RM approach. Among various forms of biomaterials explored until the present day, hydrogels have emerged as a versatile candidate for tissue engineering and regenerative medicine (TERM) applications such as scaffolds for spatial patterning and delivering therapeutic agents, or substrates to enhance cell growth, differentiation, and migration. Although hydrogels can be prepared from a variety of synthetic polymers as well as biopolymers, the latter are preferred for their inherent biocompatibility. Specifically, keratins are fibrous proteins that have been recently explored for constructing hydrogels useful for RM purposes. The present review discusses the suitability of keratin-based biomaterials in RM, with a particular focus on human hair keratin hydrogels and their use in various RM applications.

Effect of Microwave and Ultrasound-Assisted Extraction on the Phytochemical and In Vitro Biological Properties of Willow (Salix alba) Bark Aqueous and Ethanolic Extracts

White willow (Salix alba) is a medicinal plant used in folk medicine. In this study, aqueous and ethanolic willow bark extracts were obtained via ultrasonic-assisted extraction (UAE) and microwave-assisted extraction (MAE), and analyzed regarding their phytochemical (total phenolics, phenolic acids, flavonoids, and tannins) content and in vitro biological properties (antibacterial and antifungal activity, acetylcholinesterase AChE inhibitory activity and anti-inflammatory effects). The highest phenolic, tannin, and flavonoid contents were found for willow bark extracts obtained via microwave-assisted extraction using ethanol as a solvent (SA-ME). The polyphenol load of all MAE and UAE extracts was higher when conventional solid-liquid extraction was applied (ρ < 0.05). The antioxidant capacities were stronger for microwave-assisted ethanolic extracts, with the lowest IC₅₀ values of 12 μg/mL for DPPH^• and a value of 16 μg/mL for ABTS•+, whereas the conventional extraction had the highest IC₅₀ values (22 μg/mL and 28 μg/mL, respectively). Willow bark extract showed antibacterial activity against Gram-positive bacteria S. aureus and P. aeruginosa. AChE inhibitory activity was dependent on the extraction method and solvent used, and the highest inhibition among samples was observed for SA-ME. Taken altogether, our findings suggest that willow (Salix alba) bark extract obtained via ethanolic microwave-assisted extraction is a phytochemical-rich resource with in vitro, anti-inflammatory, and AchE inhibitory properties and, therefore, potential multiple medicinal end-uses.

Do Anti-Biofilm Antibiotics Have a Place in the Treatment of Diabetic Foot Osteomyelitis?

The choice of antibiotic regimens for use in patients presenting with diabetic foot osteomyelitis and their duration differs according to the situation. Antibiotics play a more important role in the medical option where no infected bone has been resected, while their role is reduced but not negligible in the case of surgical options. Some studies have reported the presence of biofilm structures in bone samples taken from patients with diabetic foot osteomyelitis, which raises the question of the place of anti-biofilm antibiotic regimens in this setting. During the last two decades, clinical studies have suggested a potential benefit for anti-biofilm antibiotics, mainly rifampicin against staphylococci and fluoroquinolones against gram-negative bacilli. However, no data from randomized controlled studies have been reported so far. The present work provides a summary of the available data on the question of the place of anti-biofilm antibiotics for the treatment of diabetic foot osteomyelitis, but also the potential limitations of such treatments.

Antimicrobial Resistance of Salmonella Strains Isolated from Human, Wild Boar, and Environmental Samples in 2018-2020 in the Northwest of Italy

Antimicrobial resistance is one of the most challenging public health problems worldwide, and integrated surveillance is a key aspect in a One Health control strategy. Additionally, Salmonella is the second most common zoonosis in Europe. We aimed to investigate the circulation of Salmonella strains and their related antimicrobial resistance in human, environmental, and wild boar samples from the northwest of Italy, from 2018 to 2020, to obtain a more comprehensive epidemiological picture. Salmonella Typhimurium 1,4,[5],12:i:-, S. Veneziana and S. Newport were the most common serotypes occurring in humans, the environment, and wild boar, respectively. Antimicrobial resistance was rather common in Salmonella isolates, with those from human displaying the highest degree of resistance against sulfadiazine−sulfamerazine−sulfamethazine (>90% of resistance). Moreover, resistance against azithromycin were exclusively observed in environmental samples, while only 7.7% (95% CI = 1.6−20.8) of wild boar isolates experienced resistance against trimethoprim−sulfamethoxazole. Multidrug resistance concurrently involved up to seven antimicrobial classes in human isolates, including third-generation cephalosporins and fluoroquinolones. Salmonella Typhimurium in humans and serotypes Goldcoast and Rissen from environmental sources showed the highest levels of resistance. This study shows diverse antimicrobial resistance patterns in Salmonella strains isolated from different sources and gives a broad picture of antimicrobial resistance spread in wild animals, humans, and the environment.

Antimicrobial Resistance: The 'Other' Pandemic! : Based on 9th Dr. I. C. Verma Excellence Award for Young Pediatricians Delivered as Oration on 19th Sept. 2021

Antimicrobial resistance is projected to kill 10 million people by 2050. The biggest driver of antimicrobial resistance is excessive/unrestricted use of antimicrobials in humans and animals. Antimicrobial resistance is a problem in all types of pathogens including bacteria, mycobacteria, viruses, fungi, and parasites both globally and India and in both adults and children. The areas of greatest concern for India is the epidemic of MDR and XDR tuberculosis and resistance in gram-negative pathogens. The alarming rate of extended spectrum beta lactamase (ESBL) production in Enterobacteriales in both community and health care-associated infections is driving carbapenem use. Rates of carbapenem resistance are now significantly high in health care-associated gram negative pathogens with associated high mortality rates. The key solution to this antimicrobial resistance crisis needs participation of all stakeholders and lies in promoting rational antimicrobial therapy.

Advances in pharmacotherapy for diabetic foot osteomyelitis

Introduction: The diagnosis of diabetic foot osteomyelitis (DFO) is usually clinical. Its severity is related to the location and depth of the lesion, and the presence of necrosis or gangrene. The aetiology of diabetic foot osteomyelitis (DFO) is usually polymicrobial, and DFO is often associated with chronic or recurring ulceration.Areas covered: We built on the  International Working Group on the Diabetic Foot (IWGDF) guidelines on the management of diabetic foot infection, providing an outline of the current and new concepts in pharmacotherapy in DFO. We assess future strategies in both medical, surgical and combination management of DFO.Expert opinion: Surgical removal of infected bone is considered as the standard treatment, but a medical approach of certain selected situations has now proven efficacy in selected patients. The combination of new modalities in local antibiotic delivery may provide better long-term solutions and more lasting remission and avoid the disadvantages of prolonged systemic antibiotics.

From the Farms to the Dining Table: The Distribution and Molecular Characteristics of Antibiotic-Resistant Enterococcus spp. in Intensive Pig Farming in South Africa

Foodborne pathogens, including antibiotic-resistant species, constitute a severe menace to food safety globally, especially food animals. Identifying points of concern that need immediate mitigation measures to prevent these bacteria from reaching households requires a broad understanding of these pathogens’ spread along the food production chain. We investigated the distribution, antibiotic susceptibility, molecular characterization and clonality of Enterococcus spp. in an intensive pig production continuum in South Africa, using the farm-to-fork approach. Enterococcus spp. were isolated from 452 samples obtained along the pig farm-to-fork continuum (farm, transport, abattoir, and retail meat) using the IDEXX Enterolert^®/Quanti-Tray^® 2000 system. Pure colonies were obtained on selective media and confirmed by real-time PCR, targeting genus- and species-specific genes. The susceptibility to antibiotics was determined by the Kirby–Bauer disk diffusion method against 16 antibiotics recommended by the WHO-AGISAR using EUCAST guidelines. Selected antibiotic resistance and virulence genes were detected by real-time PCR. Clonal relatedness between isolates across the continuum was evaluated by REP-PCR. A total of 284 isolates, consisting of 79.2% E. faecalis, 6.7% E. faecium, 2.5% E. casseliflavus, 0.4% E. gallinarum, and 11.2% other Enterococcus spp., were collected along the farm-to-fork continuum. The isolates were most resistant to sulfamethoxazole-trimethoprim (78.8%) and least resistant to levofloxacin (5.6%). No resistance was observed to vancomycin, teicoplanin, tigecycline and linezolid. E. faecium displayed 44.4% resistance to quinupristin-dalfopristin. Also, 78% of the isolates were multidrug-resistant. Phenotypic resistance to tetracycline, aminoglycosides, and macrolides was corroborated by the presence of the tetM, aph(3′)-IIIa, and ermB genes in 99.1%, 96.1%, and 88.3% of the isolates, respectively. The most detected virulence gene was gelE. Clonality revealed that E. faecalis isolates belonged to diverse clones along the continuum with major REP-types, mainly isolates from the same sampling source but different sampling rounds (on the farm). E. faecium isolates revealed a less diverse profile. The results suggest that intensive pig farming could serve as a reservoir of antibiotic-resistant bacteria that could be transmitted to occupationally exposed workers via direct contact with animals or consumers through animal products/food. This highlights the need for more robust guidelines for antibiotic use in intensive farming practices and the necessity of including Enterococcus spp. as an indicator in antibiotic resistance surveillance systems in food animals.

An evidence based narrative review on treatment of diabetic foot osteomyelitis

OBJECTIVE

The diagnosis of diabetic food infection is usually clinical, and its severity is related to location and depth of the lesion, and the presence of necrosis or gangrene. Osteomyelitis of the foot and ankle can be extremely debilitating, and, in the preantibiotic era acute staphylococcal osteomyelitis carried a mortality rate of 50%. The microbiology of diabetic foot osteomyelitis (DFO) is usually polymicrobial. Indeed, gram-negative and gram-positive bacilli can be identified using molecular techniques applied to bone biopsies compared to conventional techniques. The aim of the present study is to report a complete overview regarding medical and surgical management of diabetic foot osteomyelitis (DFO) in combination or alone.

MATERIALS AND METHODS

We performed a search in PubMed and Scopus electronic databases (up to January 2019) of articles assessing the epidemiology, diagnostic strategy and pharmacological treatment of diabetic foot infection. In the search strategy, we used various combinations of the following key terms: infection, orthopaedic, diabetic foot, management, DFO.

RESULTS

This article discusses the definition, epidemiology, microbiological assessment, clinical evaluation, pharmacological and surgical management and a comparison between them, of DFO. After the initial literature search and removal of duplicate records, a total of 756 potentially relevant citations were identified. After a further screening and according to the inclusion criteria, a total of 65 articles were included in the present review.

CONCLUSION

The association of antibiotic and surgical therapy seems to be more effective compared to each one alone. The lack of comparison studies and randomized controlled trials makes it difficult to give information about the efficacy of the different management therapies.

Treatment options for diabetic foot osteomyelitis

INTRODUCTION

Diabetic foot osteomyelitis therapeutical options are based on antibiotic therapy and surgical resection of the infected bone(s). Surgical and medical approaches of patients suffering from a diabetic foot osteomyelitis do not oppose but are complementary and need to be discussed as a tailored manner. Areas covered: The aim of the present article is to discuss data issued from the most recent guidelines of the Infectious Diseases Society of America and the International Working Group on the Diabetic Foot on the management of the diabetic foot infection and from a search in the current literature using the terms diabetic foot osteomyelitis and treatment/therapy/therapeutical in both PubMed and Medline, restricted to the last five years. Expert opinion: Surgical removal of the entire infected bone(s) has been considered in the past as the standard treatment but medical approach of these patients has now proven efficacy in selected situations. The current emergence of bacteria, especially among Gram negative rods, resistant to almost all the available antibiotics gradually augments the complexity of the management of these patients and is likely to decrease the place of the medical approach and to worsen the outcome of these infections in the next future.

Cloacael Carriage and Multidrug Resistance Escherichia coli O157:H7 from Poultry Farms, Eastern Ethiopia

A cross-sectional study was carried out to determine antimicrobial drug resistance patterns of E. coli O157:H7 isolates and estimate the level of the pathogen. A total of 194 cloacae swab samples were collected randomly in two poultry farms. Standard cultural, biochemical, and serological (latex agglutination) methods were used to isolate E. coli O157:H7. The isolates were subjected to antimicrobial susceptibility testing using disc diffusion method. Out of 194 cloacae samples examined, 13.4% (n = 26) were found to be positive for E. coli O157:H7. The finding indicated differences in E. coli O157:H7 infection among the different risk factors. Chicken from Adele Poultry Farm showed higher E. coli O157:H7 infection (OR = 3.89) than Haramaya University poultry farm and young birds had more infection (OR = 4.62) than adult birds. Of the total 14 antimicrobials included in the panel of study, the susceptibility results were varied with 96.15% and 0% E. coli O157:H7 isolates expressing resistance to erythromycin, clindamycin, spectinomycin, and ciprofloxacin, respectively. Multidrug resistance to more than two antimicrobial agents was detected in 24 (92.30%) of the isolates. The study showed high presence of antimicrobial resistant isolates of E. coli O157:H7. Further study is required to better understand the ecology and evolution of bacterial resistance to antimicrobial agents.

Where Sepsis and Antimicrobial Resistance Countermeasures Converge

The United Nations General Assembly debate on antimicrobial resistance (AMR) recognizes the global significance of AMR. Much work needs to be done on technology capability and capacity to convert the strategic intent of the debate into operational plans and tangible outcomes. Enhancement of the biomedical science–clinician interface requires better exploitation of systems biology tools for in-laboratory and point of care methods that detect sepsis and characterize AMR. These need to link sepsis and AMR data with responsive, real-time surveillance. We propose an AMR sepsis register, similar in concept to a cancer registry, to aid coordination of AMR countermeasures.

Isolation of Enterobacter aerogenes carrying blaTEM-1 and blaKPC-3 genes recovered from a hospital Intensive Care Unit

Enterobacter aerogenes has recently emerged as an important hospital pathogen. In this study, we showed the emergence of E. aerogenes isolates carrying the blaKPC gene in patients colonized by carbapenem-resistant Klebsiella pneumoniae strains. Two multiresistant E. aerogenes isolates were recovered from bronchial aspirates of two patients hospitalized in the Intensive Care Unit at the "Santa Maria della Scaletta" Hospital, Imola. The antimicrobial susceptibility test showed the high resistance to carbapenems and double-disk synergy test confirmed the phenotype of KPC and AmpC production. Other investigation revealed that ESBL and blaKPC genes were carried on the conjugative pKpQIL plasmid. This is a relevant report in Italy that describes a nosocomial infection due to the production of KPC beta-lactamases by an E. aerogenes isolate in patients previously colonized by K. pneumoniae carbapenem-resistant. In conclusion, it's necessary a continuous monitoring of multidrug-resistant strains for the detection of any KPC-producing bacteria that could expand the circulation of carbapenem-resistant pathogens.

Ertapenem resistance in 2 tertiary-care hospitals: Microbiology, epidemiology, and risk factors

INTRODUCTION

Carbapenems resistance is a growing phenomenon and a threat to public health because of the reduced therapeutic options for resistant infections.

METHODS

A retrospective case-control study was conducted in 2 tertiary-care hospitals in Medellín, Colombia. Fifty patients infected with ertapenem-resistant enterobacteriaceae were compared with a control group consisting of 100 patients with infections caused by ertapenem susceptible enterobacteriaceae. A multivariate logistic regression model was used to identify factors that best explain ertapenem-resistant enterobacteriaceae infections.

RESULTS

The factors associated with ertapenem-resistant enterobacteriaceae infections were prior exposure to carbapenems (adjusted OR 3.43; 95% IC 1.08-10.87) and prior exposure to cefepime (adjusted OR 6.46; 95% IC 1.08-38.38).

CONCLUSION

Prior exposure to antibiotics is the factor that best explains the ertapenem-resistant enterobacteriaceae infection in this population, highlighting the importance of antimicrobial stewardship programs in hospitals.

Antimicrobial resistance: a global multifaceted phenomenon

Antimicrobial resistance (AMR) is one of the most serious global public health threats in this century. The first World Health Organization (WHO) Global report on surveillance of AMR, published in April 2014, collected for the first time data from national and international surveillance networks, showing the extent of this phenomenon in many parts of the world and also the presence of large gaps in the existing surveillance. In this review, we focus on antibacterial resistance (ABR), which represents at the moment the major problem, both for the high rates of resistance observed in bacteria that cause common infections and for the complexity of the consequences of ABR. We describe the health and economic impact of ABR, the principal risk factors for its emergence and, in particular, we illustrate the highlights of four antibiotic-resistant pathogens of global concern - Staphylococcus aureus, Klebsiella pneumoniae, non-typhoidal Salmonella and Mycobacterium tuberculosis - for whom we report resistance data worldwide. Measures to control the emergence and the spread of ABR are presented.

Adhesive behaviour and virulence of coagulase negative staphylococci isolated from Italian cheeses

Coagulase-negative staphylococci (CoNS) belong to saprophytic microbiota on the skin and mucous membranes of warm-blooded animals and humans, but are also isolated from foodstuffs such as meat, cheese, and milk. In other circumstances, some CoNS can act as pathogens. Thus the presence of CoNS may not be an immediate danger to public health, but can become a risk factor. In particular antibiotic-resistant genes could be transferred to other potentially pathogenic microorganisms. Furthermore, CoNS are known to be strong biofilm producers and this is also a risk factor for public health. The aim of the present work was to determine the genotypic and phenotypic profiles of 106 CoNS belonging to four different species isolated from five different Italian cheeses for the presence of some adhesion and virulence features. In order to verify a possible correlation between the formation of biofilm and staphylococcal virulence factors, we checked the presence of adhesin genes by PCR and we investigated the ability of these strains to make biofilm at different temperatures. Furthermore, in some conditions, we analyzed surface proteins and autolytic pattern of selected strains. In conclusion, we checked the presence of norA and mecA genes responsible for fluoroquinolones and methicillin resistance, respectively. We found resistant genes in a proportion of the food isolates in amounts of 9.4% (mecA) and 5.7% (norA). These data support the importance to continuously examine the microbiota not only for the creation of a database but also to safeguard public health.

Ciprofloxacin-Loaded Keratin Hydrogels Prevent Pseudomonas aeruginosa Infection and Support Healing in a Porcine Full-Thickness Excisional Wound

Objective: Cutaneous wound infection can lead to impaired healing, multiple surgical procedures, and increased hospitalization time. We tested the effectiveness of keratin-based hydrogels (termed "keratose") loaded with ciprofloxacin to inhibit infection and support healing when topically administered to porcine excision wounds infected with Pseudomonas aeruginosa. Approach: Using a porcine excisional wound model, 10 mm full-thickness wounds were inoculated with 10⁶ colony-forming units of P. aeruginosa and treated on days 1 and 3 postinoculation with ciprofloxacin-loaded keratose hydrogels. Bacteria enumeration and wound healing were assessed on days 3, 7, and 11 postinjury. Results: Ciprofloxacin-loaded keratose hydrogels reduced the amount of P. aeruginosa in the wound bed by 99.9% compared with untreated wounds on days 3, 7, and 11 postinjury. Ciprofloxacin-loaded keratose hydrogels displayed decreased wound contraction and reepithelialization at day 7 postinjury. By day 11, wounds treated with ciprofloxacin-keratose hydrogels contained collagen-rich granulation tissue and myofibroblasts. Wounds treated with ciprofloxacin-loaded keratose hydrogels exhibited a transient increase in macrophages in the wound bed at day 7 postinjury that subsided by day 11. Innovation: Current therapies for wound infection include systemic antibiotics, which could lead to antibiotic resistance, and topical antimicrobial treatments, which require multiple applications and can delay healing. Here, we show that ciprofloxacin-loaded keratose hydrogels inhibit cutaneous wound infection without interfering with key aspects of the healing process including granulation tissue deposition and remodeling. Conclusions: Ciprofloxacin-loaded keratose hydrogels have the potential to serve as a point-of-injury antibiotic therapy that prevents infection and supports healing following cutaneous injury.

Isolation and molecular characterization of Salmonella spp. from chevon and chicken meat collected from different districts of Chhattisgarh, India

AIM

The aim was to assess the prevalence of Salmonella in raw chevon and chicken meat sold in the retail meat shops situated in and around Durg, Rajnandgaon, Dhamtari, Raipur, and Bilaspur districts of Chhattisgarh. Studies were also conducted to find out the antibiotic resistance in Salmonella isolates.

MATERIALS AND METHODS

A total of 400 samples comprising of 200 chevon meat and 200 chicken meat samples were processed for isolation of Salmonella and all isolates were further confirmed on the basis of cultural and biochemical characters and by targeting invA gene of Salmonella. All Salmonella isolates were also examined for their antimicrobial drug susceptibility/resistance pattern against commonly used antibiotics.

RESULTS

Out of 400 samples, the prevalence of Salmonella in chevon and chicken meat was found 9% and 7% respectively, with an overall prevalence of 8%. Polymerase chain reaction targeting invA gene of Salmonella showed positive result with 31 isolates. All 32 Salmonella isolates were found to be highly sensitive to ciprofloxacin while 96.87%, 96.87% and 93.75% were sensitive to gentamicin, imipenem, and ceftazidime, respectively. 93.75% and 59.37% isolates were resistant to erythromycin and oxytetracycline, respectively. Out of 32, 14 isolates had multiple antibiotic resistance index equal to or more than 0.2.

CONCLUSION

Salmonella in chevon and chicken meat samples is prevailing in the areas of sampling due to poor hygienic conditions and also demonstrated the varied spectrum of antimicrobial resistance, including several multiple drug resistance phenotypes. Therefore, the present study emphasizes the need for continued surveillance of zoonotic foodborne pathogens including antimicrobial-resistant variants throughout the food production chain.

Six-week versus twelve-week antibiotic therapy for nonsurgically treated diabetic foot osteomyelitis: a multicenter open-label controlled randomized study

OBJECTIVE

Little is known about the optimal duration of antibiotic therapy for diabetic foot osteomyelitis (DFO). This study sought to compare the effectiveness of 6 versus 12 weeks of antibiotic therapy in patients with DFO treated nonsurgically (i.e., antibiotics alone).

RESEARCH DESIGN AND METHODS

This was a prospective randomized trial comparing 6- versus 12-week duration of antibiotic treatment. Remission of osteomyelitis during the monitoring period was defined as complete and persistent (>4 weeks) healing of the wound (if present initially), absence of recurrent infection at the initial site or that of adjacent rays, and no need for surgical bone resection or amputation at the end of a follow-up period of at least 12 months after completion of antibiotic treatment.

RESULTS

Forty patients followed at five French general hospitals were randomized between January 2007 and January 2009, with 20 treated for 6 weeks and 20 treated for 12 weeks with antibiotics. The two groups were comparable for all variables recorded at inclusion in the study. Remission was obtained in 26 (65%) patients, with no significant differences between patients treated for 6 versus 12 weeks (12/20 vs. 14/20, respectively; P = 0.50). We did not identify any significant parameters associated with patient outcome. Fewer patients treated for 6 weeks experienced gastrointestinal adverse events related to antimicrobial therapy compared with patients treated for 12 weeks (respectively, 15 vs. 45%; P = 0.04).

CONCLUSIONS

The present multicenter prospective randomized study provides data suggesting that 6-week duration of antibiotic therapy may be sufficient in patients with DFO for whom nonsurgical treatment is considered.

In vitro and in vivo synergistic interaction of substituted chalcone derivatives with norfloxacin against methicillin resistant Staphylococcus aureus

The present investigation shows that certain substituted chalcone derivatives diminish the escalation of bacterial cellsviainhibiting bacterial efflux pump and exhibit a synergistic interaction with norfloxacin.

Difficult Situations Managing Diabetic Foot. Evidences and Personal Views

Both medical and surgical approaches have been shown to be effective in the treatment of patients with diabetic foot osteomyelitis (DFO). In patients with risk factors of bad outcome such as major bone destruction, concomitant acute infections requiring drainage, problems in limb perfusion, highly resistant bacteria, and contraindication for or patient refusal of prolonged antibiotic therapy, the choice of surgery does not require further discussion. On the contrary, modest changes of bone on imaging assessment and no limiting factors as described above make medical treatment an attractive option for patients with DFO provided the rules of antibiotic treatment of chronic osteomyelitis are respected. The key question may not be to oppose surgery and medical treatment but to identify patients who need surgery and those who do not. There is currently no classification or score system that may allow physician to decide whether medical or surgical approach is best adapted to a given patient, and so both experience and skill of the multidisciplinary team appear paramount for guiding the choice of the best adapted (“tailored”) strategy in a given patient. In this regard, it would be interesting to compare surgical and medical approaches for DFO that apparently may benefit from one or another (ie, bone lesions seen on plain radiographs of the foot but without bone fragmentation or multiple sites of osteomyelitis, no contraindication to prolonged antibiotic therapy, and location of bone involvement that may allow conservative surgery). Given the current available data on the therapeutic options of DFO, it appears that surgery for those patients is obviously not an old-fashioned option.

Spectrum and patterns of antimicrobial resistance of uropathogens isolated from a sample of hospitalised Lebanese patients with urinary tract infections

A retrospective study was carried out to assess the current distribution and antimicrobial susceptibility patterns of uropathogens isolated from patients with community-acquired (CA) or hospital-acquired (HA) urinary tract infections (UTIs) who were admitted to the largest governmental hospital in Beirut City (Lebanon) in 2009-2012. Overall, 292 uropathogens were isolated. Enterobacteriaceae constituted 81% of the isolated uropathogens, with Escherichia coli, Klebsiella pneumoniae and Proteus mirabilis being the most reported species. Moreover, 37% of the isolated uropathogens produced extended-spectrum β-lactamases (ESBLs). ESBL-producing strains were more prevalent in CA-UTIs than in HA-UTIs. In the CA-UTI group, ESBL-producing strains were more prevalent in older patients (age >60 years), male patients and patients with diabetes mellitus, urinary catheterisation and benign prostatic hyperplasia. Uropathogens isolated from CA-UTI and HA-UTI had similar resistance patterns. The highest resistance rates were found for ampicillin, amoxicillin/clavulanic acid, trimethoprim/sulfamethoxazole and ciprofloxacin. Imipenem, nitrofurantoin and piperacillin/tazobactam showed good overall activity against the isolated uropathogens. Of the isolated non-ESBL-producing E. coli, 29% were found to be multidrug-resistant. These data suggest that there is an urgent need to implement a national policy regulating the use of antibiotics, notably in the community, in order to limit the widespread increase in antimicrobial resistance.

Ceftaroline fosamil for the treatment of acute bacterial skin and skin structure infections

Skin infections have traditionally been classified by the US FDA as uncomplicated and complicated. In August 2010, the FDA released a new guidance document for the development of drugs to treat acute bacterial skin and skin structure infections (ABSSSI) and this was updated in 2013. Several new issues were addressed and henceforth skin infections in clinical trials were termed ABSSSI. In the USA, the annual prevalence of methicillin-resistant Staphylococcus aureus-related skin infections have continuously increased from 32.7% in 1998 to 53.8% in 2007. Ceftaroline fosamil is the only cephalosporin approved in the USA for monotherapy treatment of ABSSSI including infections caused by methicillin-resistant S. aureus. The efficacy of ceftaroline fosamil was shown in the CANVAS clinical trials. The CANVAS Day-3 analyses met an earlier, primary efficacy time point requested by the FDA. Ceftaroline has minimal drug-drug interactions, is well tolerated and possesses the safety profile associated with the cephalosporin class.

Clinical impact of extended-spectrum β-lactamase-producing Enterobacteriaceae in patients with biliary tract infection

BACKGROUND

Clinical outcomes associated with Gram-negative bacterial isolates with extended spectrum beta-lactamase (ESBL) in patients with biliary tract infection are largely unknown. The objective of the present study was to compare the demographics, risk factors, and clinical outcomes between patients with biliary tract infection caused by ESBL-producing and non-producing Klebsiella pneumoniae and Escherichia coli.

METHODS

Between February 2005 and August 2010, we collected 159 cases with biliary tract infection caused by K. pneumoniae and E. coli identified by blood or bile cultures obtained before endoscopic or surgical treatment performed at our institution. We also retrospectively collected the data of patients' demographic characteristics, co-morbid conditions, antimicrobial therapy, and clinical outcomes.

RESULTS

Among the 159 strains isolated, 21 strains (13.2 %) were positive for phenotypical ESBL-test. Sepsis was more common in ESBL-positive strains, but did not reach statistical significance (23.8 % for ESBL-positive strains and 9.4 % for ESBL-negative strains, P = 0.066). Thirty-day mortality was significantly higher in ESBL-positive strains (3/21, 14.3 %) compared to ESBL-negative strains (4/138, 2.9 %, P = 0.049). However, there were no significant differences in overall survival between ESBL-positive and ESBL-negative strains. By multivariate analysis, inadequate antimicrobial therapy (HR 4.06, 95 % CI 1.08-16.46, P = 0.049) and sepsis (HR 6.54, 95 % CI 1.26-33.85, P = 0.025) were independent and significant predictors of 30-day mortality.

CONCLUSION

ESBL status of bacterial isolates for patients with biliary tract infection caused by K. pneumoniae and E. coli has clinical impact, especially on the short-term outcomes of those patients.

Antibiotic Resistance Mechanisms in the Intensive Care Unit

Antibiotic resistance is increasingly recognised as a major threat to global health, with few new antimicrobial agents in development. The intensive care unit provides a unique environment for the growth and spread of drug-resistant organisms. Knowledge of the pathogenesis and mechanisms of resistance of drug-resistant organisms provides a conceptual framework which underpins the clinical manifestation of infections caused by these organisms, and is crucial for the intensivist to understand. Particular importance lies in the prevention of infection and the control of drug-resistant pathogens. The major resistance mechanisms of these organisms will be highlighted, focusing on specific gram-positive (meticillin-resistant Staphylococcus aureus and glycopeptide-resistant Enterococci), gram-negative ( Pseudomonas aeruginosa, Acinetobacter baumannii and multi-drug resistant Enterobacteriaceae) organisms, and then placed in historical and clinical context.

Evaluation of silver-containing activated carbon fiber for wound healing study: In vitro and in vivo

Silver has antiseptic properties, anti-inflammatory properties, and is a broad-spectrum antibiotic for multidrug-resistant strains of bacteria. The commercially available product, Silverlon®, is a silver-plated three-dimensional polyamide fabric with a high silver concentration of 546 mg/100 cm(2). Thus, fibroblast cell growth is affected when exposed to the Silverlon® treated cell medium. Our study produced an activated carbon fiber wound dressing that incorporated various silver concentrations (in cooperation of Bio-Medical Carbon Technology) to examine antimicrobial properties and determine fibroblast cell viability upon exposure to the silver impregnated dressing material as compared to other commercially available products such as calcium alginate dressing, Sorbalgon®, and silver-polyamide fabric dressing, Silverlon®. The silver impregnated activated carbon fiber dressing induced less damage to fibroblast cells compared to the effect produced by Silverlon® and exhibited similar antibacterial abilities in vitro. An in vivo analysis showed that various silver concentrations impregnated activated carbon fiber dressings promoted tissue reconstruction for wound healing in rats with Pseudomonas aeruginosa infected wounds.

Impact of cefepime therapy on mortality among patients with bloodstream infections caused by extended-spectrum-β-lactamase-producing Klebsiella pneumoniae and Escherichia coli

Extended-spectrum-β-lactamase (ESBL)-producing pathogens are associated with extensive morbidity and mortality and rising health care costs. Scant data exist on the impact of antimicrobial therapy on clinical outcomes in patients with ESBL bloodstream infections (BSI), and no large studies have examined the impact of cefepime therapy. A retrospective 3-year study was performed at the Detroit Medical Center on adult patients with BSI due to ESBL-producing Klebsiella pneumoniae or Escherichia coli. Data were collected from the medical records of study patients at five hospitals between January 2005 and December 2007. Multivariate analysis was performed using logistic regression. One hundred forty-five patients with BSI due to ESBL-producing pathogens, including K. pneumoniae (83%) and E. coli (16.5%), were studied. The mean age of the patients was 66 years. Fifty-one percent of the patients were female, and 79.3% were African-American. Fifty-three patients (37%) died in the hospital, and 92 survived to discharge. In bivariate analysis, the variables associated with mortality (P < 0.05) were presence of a rapidly fatal condition at the time of admission, use of gentamicin as a consolidative therapeutic agent, and presence of one or more of the following prior to culture date: mechanical ventilation, stay in the intensive care unit (ICU), and presence of a central venous catheter. In multivariate analysis, the predictors of in-hospital mortality included stay in the intensive care unit (odds ratio [OR], 2.17; 95% confidence interval [CI], 0.98 to 4.78), presence of a central-line catheter prior to positive culture (OR, 2.33; 95% CI, 0.77 to 7.03), presence of a rapidly fatal condition at the time of admission (OR, 5.13; 95% CI, 2.13 to 12.39), and recent prior hospitalization (OR, 1.92; 95% CI, 0.83 to 4.09). When carbapenems were added as empirical therapy to the predictor model, there was a trend between empirical carbapenem therapy and decreased mortality (OR, 0.61; 95% CI, 0.26 to 1.50). When added to the model, receipt of empirical cefepime alone (n = 43) was associated with increased mortality, although this association did not reach statistical significance (OR, 1.66; 95% CI, 0.71 to 3.87). The median length of hospital stay was shorter for patients receiving empirical cefepime than for those receiving empirical or consolidated carbapenem therapy. In multivariate analysis, empirical therapy with cefepime for BSI due to an ESBL-producing pathogen was associated with a trend toward an increased mortality risk and empirical carbapenem therapy was associated with a trend toward decreased mortality risk.

Optimizing antimicrobial therapy in sepsis and septic shock

Every patient with sepsis and septic shock must be evaluated thoroughly at presentation before the initiation of antibiotic therapy. However, in most situations, an abridged initial assessment focusing on critical diagnostic and management planning elements is sufficient. Intravenous antibiotics should be administered as early as possible, and always within the first hour of recognizing severe sepsis and septic shock. Broad-spectrum antibiotics must be selected with one or more agents active against likely bacterial or fungal pathogens and with good penetration into the presumed source. Antimicrobial therapy should be reevaluated daily to optimize efficacy, prevent resistance, avoid toxicity, and minimize costs. Consider combination therapy in Pseudomonas infections, and combination empiric therapy in neutropenic patients. Combination therapy should be continued for no more than 3 to 5 days and de-escalation should occur following availability of susceptibilities. The duration of antibiotic therapy typically is limited to 7 to 10 days; longer duration is considered if response is slow, if there is inadequate surgical source control, or in the case of immunologic deficiencies. Antimicrobial therapy should be stopped if infection is not considered the etiologic factor for a shock state.

Temporal trends in Enterobacter species bloodstream infection: a population-based study from 1998-2007

Enterobacter species are the fourth most common cause of Gram-negative bloodstream infection (BSI). We examined temporal changes and seasonal variation in the incidence rate of Enterobacter spp. BSI, estimated 28-day and 1-year mortality, and determined in vitro antimicrobial resistance rates of Enterobacter spp. bloodstream isolates in Olmsted County, Minnesota, from 1 January 1998 to 31 December 2007. Multivariable Poisson regression was used to examine temporal changes and seasonal variation in incidence rate and Kaplan-Meier method was used to estimate 28-day and 1-year mortality. The median age of patients with Enterobacter spp. BSI was 58 years and 53% were female. The overall age- and gender-adjusted incidence rate of Enterobacter spp. BSI was 3.3 per 100,000 person-years (95% CI 2.3-4.4). There was a linear trend of increasing incidence rate from 0.8 (95% CI 0-1.9) to 6.2 (95% CI 3.0-9.3) per 100,000 person-years between 1998 and 2007 (p 0.002). There was no significant difference in the incidence rate of Enterobacter spp. BSI during the warmest 4 months compared to the remainder of the year (incidence rate ratio 1.06; 95% CI 0.47-2.01). The overall 28-day and 1-year mortality rates of Enterobacter spp. BSI were 21% (95% CI 8-34%) and 38% (95% CI 22-53%), respectively. Up to 13% of Enterobacter spp. bloodstream isolates were resistant to third-generation cephalosporins. To our knowledge, this is the first population-based study to describe the epidemiology and outcome of Enterobacter spp. BSI. The increase in incidence rate of Enterobacter spp. BSI over the past decade, coupled with its associated antimicrobial resistance, dictate the need for further investigation of this syndrome.

Extended-spectrum β-lactamases of Escherichia coli and Klebsiella pneumoniae screened by the VITEK 2 system

The VITEK 2 automated system (bioMérieux) is one of the most widely used instruments in clinical microbiology laboratories for the identification and evaluation of the susceptibility profiles of bacteria including the detection of extended-spectrum β-lactamases (ESBLs) produced by Escherichia coli, Klebsiella pneumoniae and Klebsiella oxytoca. Currently, the Clinical and Laboratory Standards Institute recommends the use of ESBL confirmatory tests in addition to standard susceptibility testing. In order to evaluate the accuracy of VITEK 2-positive results regarding clinical isolates of E. coli (n = 110) and K. pneumoniae (n = 72), four additional ESBL detection systems were compared: the Phoenix Automated Microbiology System (BD Diagnostic Systems) and the MicroScan WalkAway-96 System (Dade Behring), and two manual systems as confirmatory tests, the Etest (AB Biodisk) and double disc diffusion (DDS) test. Epidemiological data regarding the tested strains were also collected and their susceptibility phenotypes were determined. The four methods resulted in concordant results for 126 of the 182 strains. However, the different tests displayed distinct results: the VITEK 2 system was in disagreement in 23.9 % of cases with DDS, in 15.3 % with Etest, in 23 % with the MicroScan WalkAway-96 System and in 23.6 % with the Phoenix Automated Microbiology System. Epidemiological data indicated that the majority of ESBL-positive E. coli strains were isolated from patients admitted to internal medicine wards (72.7 %), whilst K. pneumoniae ESBL-positive isolates were equally distributed between internal medicine wards (45.8 %) and intensive care units (45.8 %). Most of these strains were isolated from urine. In contrast to ESBL-negative isolates, the ESBL-positive strains displayed multiple drug resistance, namely to quinolones, aminoglycosides and trimethoprim-sulfamethoxazole. No significant resistance to carbapenems was detected. Overall, this study demonstrates the need for a confirmatory test following positive ESBL detection with the VITEK 2 system (panel AST-037), which appears to yield a large number of false-positive results.

Design and synthesis of anti-MRSA benzimidazolylbenzene-sulfonamides. QSAR studies for prediction of antibacterial activity

A series of benzimidazolylbenzenesulfonamide compounds containing electron-releasing and electron-withdrawing substituents were synthesized and tested for their in vitro antibacterial activity. Two BZS compounds showed strong antibacterial activity against methicillin-resistant Staphylococcus aureus and Bacillus subtilis. Quantitative studies of their structure-activity relationship using a simple linear regression analysis were applied to explore the correlation between the biological activity and the charges on acidic hydrogen atoms in the synthesized compounds.

Common complications in the surgical intensive care unit

Surgical and trauma intensive care units provide the facilities, resources, and personnel needed to care for patients who have been severely injured, present with acute surgical emergencies, require prolonged and complex elective surgical procedures, or have severe underlying medical conditions. Correcting the immediately evident physiologic derangement is only the first step in the care of these patients, because in many cases their prognosis and ultimate outcome will depend on whether additional insults accrued during their intensive care unit and hospital stay will prevent them from a full recovery. The nature, number, and complexity of the interventions used to provide advanced support requires a unique attention to the concept of patient safety, particularly when the population involved is that most vulnerable to injury and with the least amount of physiologic reserve to recover from it. The medical community, the public, and even regulatory agencies have focused on specific preventable complications that are common in surgical and injured patients, such as medical errors, healthcare-associated infections, and venous thromboembolism. Enough scientific knowledge has been obtained through well-conducted clinical trials to generate detailed evidence-based guidelines for the prevention and management of some of these pathologies, but still there are outstanding questions in terms of the applicability of the recommendations to the critically ill. In addition to clinical and technical expertise, performance improvement and quality monitoring activities provide direction for system solutions required to properly address many complications that are not provider specific.

Clinical and economic outcomes associated with community-acquired intra-abdominal infections caused by extended spectrum beta-lactamase (ESBL) producing bacteria in China

BACKGROUND

To compare clinical and economic outcomes in patients with community-acquired intra-abdominal infection (IAI) due to extended spectrum beta-lactamase (ESBL) producing (ESBL-positive) bacteria versus non-ESBL-producing (ESBL-negative) bacteria in China.

METHODS

This was a retrospective chart review study of patients hospitalized with community-acquired IAI due to ESBL-positive or ESBL-negative infections caused by Escherichia coli or Klebsiella spp. Data were collected from six hospitals in China that participated in the Study for Monitoring Antibiotic Resistance Trends (SMART) during 2006-2007. Outcomes included clinical response at discharge and following first-line antibiotic, number of antibiotic agents and classes, duration of hospitalization, and overall hospitalization and intravenous antibiotic costs.

RESULTS

Of the 85 patients included in the study, 32 (37.6%) had ESBL-positive and 53 (62.4%) had ESBL-negative infections; E. coli was responsible for 77.6% of infections. Infection resolved at discharge in 30 (93.8%) ESBL-positive and 48 (90.6%) ESBL-negative patients (P = NS). Fewer ESBL-positive patients achieved complete response following first-line antibiotics (56.3% versus 83.0%; P = 0.01). ESBL-positive patients required longer antibiotic treatment, more antibiotics, longer hospitalization (24.3 versus 14.6 days; 1.67-fold ratio; P = 0.001), and incurred higher hospitalization costs ( yen24,604 vs. yen13,788; $3604 vs. $2020; 1.78-fold ratio; P < 0.001).

CONCLUSIONS

Patients with ESBL-positive infection had similar resolution rates at discharge compared to those with ESBL-negative infection, despite poorer first-line antibiotic response. However, ESBL-positive infection led to significantly greater hospitalization cost and intravenous antibiotic cost, and longer hospital stay.

Optimizing antimicrobial therapy in sepsis and septic shock

This article reviews principles in the rational use of antibiotics in sepsis and septic shock and presents evidence-based recommendations for optimal antibiotic therapy. Every patient with sepsis and septic shock must be evaluated at presentation before the initiation of antibiotic therapy. However, in most situations, an abridged initial assessment focusing on critical diagnostic and management planning elements is sufficient. Intravenous antibiotics should be administered as early as possible, and always within the first hour of recognizing severe sepsis and septic shock. Broad-spectrum antibiotics must be selected with one or more agents active against likely bacterial or fungal pathogens and with good penetration into the presumed source. Antimicrobial therapy should be reevaluated daily to optimize efficacy, prevent resistance, avoid toxicity, and minimize costs. Consider combination therapy in Pseudomonas infections, and combination empiric therapy in neutropenic patients. Combination therapy should be continued for no more than 3 to 5 days and deescalation should occur following availability of susceptibilities. The duration of antibiotic therapy typically is limited to 7 to 10 days; longer duration is considered if response is slow, if there is inadequate surgical source control, or in the case of immunologic deficiencies. Antimicrobial therapy should be stopped if infection is not considered the etiologic factor for a shock state.

Addition of rifampin to standard therapy for treatment of native valve infective endocarditis caused by Staphylococcus aureus

Staphylococcus aureus is a common cause of native valve infective endocarditis (IE). Rifampin is often added to traditional therapy for the management of serious S. aureus infections. There are no large, prospective studies documenting the safety and efficacy of adjunctive therapy with rifampin for treatment of native valve S. aureus IE. We reviewed all cases of definite native valve S. aureus IE confirmed by modified Duke criteria in a large urban hospital between 1 January 2004 and 31 December 2005. A retrospective cohort analysis was used to assess the impact of the addition of rifampin to standard therapy. There were 42 cases of S. aureus IE treated with the addition of rifampin and 42 controls. Cases received a median of 20 days of rifampin (range, 14 to 48 days). Rifampin-resistant S. aureus isolates developed in nine cases who received rifampin before clearance of bacteremia (56%), while significant hepatic transaminase elevations also occurred in nine cases, all of whom had hepatitis C infection. Unrecognized significant drug-drug interactions with rifampin occurred frequently (52%). Cases were more likely to have a longer duration of bacteremia (5.2 versus 2.1 days; P < 0.001) and were less likely to survive (79% versus 95%; P = 0.048) than controls. Our results suggest that the potential for hepatotoxicity, drug-drug interactions, and the emergence of resistant S. aureus isolates warrants a careful risk-benefit assessment before adding rifampin to standard antibiotic treatment of native valve S. aureus IE until further clinical studies are performed.

The risk of infection after nasal colonization with Staphylococcus aureus

PURPOSE

Nasal, axillary, or inguinal colonization with Staphylococcus aureus generally precedes invasive infection. Some studies have found that colonization with methicillin-resistant S. aureus (MRSA) poses a greater risk of clinical infection than colonization with methicillin-susceptible S. aureus (MSSA). However, the magnitude of risk is unclear.

METHODS

We undertook a systematic review to provide an overall estimate of the risk of infection following colonization with MRSA compared with colonization by MSSA. Ten observational studies, with a total of 1170 patients, were identified that provided data on both MSSA and MRSA colonization and infection. A random-effects model was used to obtain pooled estimates of the odds ratio and 95% confidence interval.

RESULTS

Overall, colonization by MRSA was associated with a 4-fold increase in the risk of infection (odds ratio 4.08, 95% confidence interval, 2.10-7.44). Studies differed in the choice of patient population, severity of illness, and frequency of sampling to detect colonization.

CONCLUSION

Further research is needed to identify effective methods for sustained eradication of MRSA carriage to reduce the high risk of subsequent infection.

Successive emergence of extended-spectrum beta-lactamase-producing and carbapenemase-producing Enterobacter aerogenes isolates in a university hospital

Sixty-two clinical isolates of Enterobacter aerogenes resistant to expanded-spectrum cephalosporins were collected between July 2003 and May 2005. Among these isolates, 23 (37.1%) were imipenem (IPM) susceptible, and 39 (62.9%) were IPM insusceptible, of which 89.7% (35/39) were resistant and 10.3% (4/39) were intermediate. Isolate genotypes were compared by pulsed-field gel electrophoresis. Of 62 isolates, 48 belonged to epidemic pulsotype A (77.4%). This pulsotype included 37.5% and 58.4% of beta-lactam phenotypes b and a, respectively. Nine isolates (14.5%) belonged to pulsotype E, which included 22.3% and 77.7% of phenotypes b and a, respectively. The beta-lactamases with pIs of 5.4, 6.5, 8.2, and 8.2 corresponded to extended-spectrum beta-lactamases (ESBLs) TEM-20, TEM-24, SHV-5, and SHV-12, respectively. Of 39 IPM-insusceptible E. aerogenes isolates, 26 (66.6%) were determined to be metallo-beta-lactamase producers, by using a phenotypic method. Of these isolates, 24 harbored a bla(IMP-1) gene encoding a protein with a pI of >9.5, and two carried the bla(VIM-2) gene encoding a protein with a pI of 5.3, corresponding to beta-lactamases IMP-1 and VIM-2, respectively. The remaining 13 (33.4%) isolates were negative for the bla(IMP-1) and bla(VIM-2) genes but showed an alteration of their outer membrane proteins (OMPs). Ten of these isolates produced the two possible OMPs (32 and 42 kDa), with IPM MICs between 8 and 32 microg/ml, and three others produced only a 32-kDa OMP with IPM MICs >32 microg/ml. This work demonstrates that, in addition to resistance to expanded-spectrum cephalosporins, IPM resistance can occur in ESBL-producing E. aerogenes isolates by carbapenemase production or by the loss of porin in the outer membrane.

Extended spectrum beta-lactamase producing Enterobacteriaceae in Lebanese ICU patients: epidemiology and patterns of resistance

Our study aims to investigate and describe the epidemiology of the intestinal carriage of ESBL-PS in intensive care units of five Lebanese hospitals and to analyze the potential risk factors for the acquisition of these strains. At the same time, we intend to determine the patterns of susceptibility of these strains, exploring therefore the availability of alternative treatment. One thousand, four hundred forty-two fecal samples were collected between January 1, 2003 and March 31, 2003 from 378 patients admitted to the ICUs of five Lebanese tertiary care general hospitals located in different areas of Lebanon. ESBL production was detected by the double disk synergy test and antibiotic susceptibility of ESBL-producing strains as well as minimum inhibitory concentrations were determined. A paired case-control study was undertaken to identify risk factors for carriage of ESBL-PS. One hundred eighteen strains isolated from 72 subjects were identified as ESBL producers, including 95 (80.5%) E. coli, 16 (13.6%) Klebsiella pneumoniae, and 7 (5.6%) Enterobacter cloacae. A higher rate of multiple ESBL-PS carriage was described among these acquisition cases (21 double carriages and 3 triple carriages of ESBL-PS compared to only 1 double carriage of ESBL-PS at admission). In general, similar trends of susceptibility were observed in the different hospitals. As expected, the lowest MIC was observed with imipenem for all E. coli, Klebsiella, and Enterobacter isolates. Ciprofloxacin, followed by trimethoprim-sulfamethoxazole seem to be associated with the lowest susceptibility. In vitro susceptibility to cefoxitin for all isolates was 74.6%; more resistance was associated to ceftazidime (90.7%) than to cefotaxime (69.7%). Our data agree with other national and international reports showing the increase in ESBL-PS carriage in ICU patients. They demonstrate the endemic character of this carriage in Lebanese hospitals and the important risk factors including immunosuppression and evidence of ESBL infection. The highly resistant profile of ESBL-PS to antimicrobial agents available for treatment reflects the severity of this issue. The significance of this study resides in the direct correlation between our results and the nationwide increase in multi-drug resistant bacteria and the continuous change in bacterial resistance epidemiology. Our data may have an important impact on infection control policies in hospitals and on treatment of infectious diseases.

Antimicrobial Resistance in Salmonella and Escherichia coli Isolated from Commercial Shell Eggs

The development of antimicrobial resistance in bacteria has become a global problem. Isolates of Salmonella and Escherichia coli recovered from shell egg samples, collected at 3 commercial plants, were analyzed for resistance to 16 antimicrobial agents (n=990). Eggs were sampled by rinsing in a saline solution. Pooled samples were preenriched in buffered peptone water and then selectively isolated using standard broths and agars. Salmonella-positive isolates were serogrouped immunologically before being serotyped. Enterobacteriaceae were enumerated from individual samples using violet red bile glucose agar plates. Escherichia coli were identified biochemically from presumptive Enterobacteriaceae isolates. Salmonella and generic E. coli antimicrobial-susceptibility testing was conducted using a semiautomated broth microdilution system. More resistance was observed in the Salmonella isolates (n=41) than in the E. coli isolates (n=194). Salmonella Typhimurium was the most prevalent (69.0%) serotype and demonstrated the greatest multiple resistance. Salmonella Kentucky, the least prevalent (5.0%) serotype recovered, was the most susceptible. Although 34.1% of the Salmonella serotypes were susceptible to all antimicrobial agents, 60.1% were resistant to 11 or more compounds. Many Salmonella isolates exhibited resistance to tetracycline (63.4%), nalidixic acid (63.4%), and streptomycin (61.0%). Most E. coli isolates (73.2%) were susceptible to all antimicrobial drugs. Many E. coli isolates exhibited resistance to tetracycline (29.9%), streptomycin (6.2%), and gentamicin (3.1%). Only 1% of the E. coli isolates were resistant to 4 antimicrobial agents. These data indicate that shell eggs can harbor resistant foodborne and commensal bacteria; among Salmonella isolates, resistance was serotype-dependent.

Use of a program-specific website to disseminate surveillance data obtained from the Meropenem Yearly Susceptibility Test Information Collection (MYSTIC) Study

The Meropenem Yearly Susceptibility Test Information Collection (MYSTIC) Program is a multicenter, longitudinal surveillance study initiated in 1997 that compares the activity of meropenem and comparator antimicrobials in centers that are actively prescribing meropenem. Antimicrobial surveillance programs, such as MYSTIC, provide important information on the emergence of bacterial resistance and the nature of the underlying mechanisms in different geographical regions. Data concerning these mechanisms and patterns of antimicrobial resistance allow the implementation of changes in antimicrobial prescribing practices and infection control interventions. Therefore, it is important that data from surveillance programs be analyzed and accessible to clinicians within reasonable, clinically useful, intervals. In this article, the use of a website designed to disseminate data collected from the MYSTIC program is described. This web-based program allows specific surveillance data to be examined in a timely manner and can assist the clinician when choosing the most appropriate antibiotic for the situation encountered and hopefully maximize successful clinical outcomes.