Antimicrobial resistance in hospital-acquired gram-negative bacterial infections

Bismuth Phosphinates in Bi-Nanocellulose Composites and their Efficacy towards Multi-Drug Resistant Bacteria

A series of poorly soluble phenyl bis-phosphinato bismuth(III) complexes [BiPh(OP(=O)R¹ R² )₂ ] (R¹ =R² =Ph; R¹ =R² =p-OMePh; R¹ =R² =m-NO₂ Ph; R¹ =Ph, R² =H; R¹ =R² =Me) have been synthesised and characterised, and shown to have effective antibacterial activity against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE). The bismuth complexes were incorporated into microfibrillated (nano-) cellulose generating a bismuth-cellulose composite as paper sheets. Antibacterial evaluation indicates that the Bi-cellulose materials have analogous or greater activity against Gram positive bacteria when compared with commercial silver based additives: silver sulfadiazine loaded at 0.43 wt % into nanocellulose produces a 10 mm zone of inhibition on the surface of agar plates containing S. aureus whereas [BiPh(OP(=O)Ph₂ )₂ ] loaded at 0.34 wt % produces an 18 mm zone of inhibition. These phenyl bis-phosphinato bismuth(III) complexes show potential to be applied in materials in healthcare facilities, to inhibit the growth of bacteria capable of causing serious disease.

Role of Peptidylarginine Deiminase 4 in Neutrophil Extracellular Trap Formation and Host Defense during Klebsiella pneumoniae-Induced Pneumonia-Derived Sepsis

Peptidylarginine deiminase 4 (PAD4) catalyzes citrullination of histones, an important step for neutrophil extracellular trap (NET) formation. We aimed to determine the role of PAD4 during pneumonia. Markers of NET formation were measured in lavage fluid from airways of critically ill patients. NET formation and host defense were studied during pneumonia-derived sepsis caused by Klebsiella pneumoniae in PAD4^+/+ and PAD4^-/- mice. Patients with pneumosepsis, compared with those with nonpulmonary disease, showed increased citrullinated histone 3 (CitH3) levels in their airways and a trend toward elevated levels of NET markers cell-free DNA and nucleosomes. During murine pneumosepsis, CitH3 levels were increased in the lungs of PAD4^+/+ but not of PAD4^-/- mice. Combined light and electron microscopy showed NET-like structures surrounding Klebsiella in areas of CitH3 staining in the lung; however, these were also seen in PAD4^-/- mice with absent CitH3 lung staining. Moreover, cell-free DNA and nucleosome levels were mostly similar in both groups. Moreover, Klebsiella and LPS could still induce NETosis in PAD4^-/- neutrophils. Both groups showed largely similar bacterial growth, lung inflammation, and organ injury. In conclusion, these data argue against a major role for PAD4 in NET formation, host defense, or organ injury during pneumonia-derived sepsis.

High Prevalence and Endemicity of Multidrug Resistant Acinetobacter spp. in Intensive Care Unit of a Tertiary Care Hospital, Varanasi, India

The increasing emergence of Acinetobacter spp. with healthcare associated infections (HCAI) in intensive care units (ICU) is alarming. This study was a laboratory-based audit to determine the prevalence of Acinetobacter spp. associated with HCAI in the adult ICU of a tertiary care hospital in Varanasi, north India, with special reference to antimicrobial resistance and resistance determinants over a period of 5 years. A total of 993 cases of HCAI were analyzed. Isolates were characterized as multidrug resistance and extended drug resistance (MDR/XDR) based on antimicrobial susceptibility records. Few (100) randomly selected isolates of Acinetobacter baumannii (A. baumannii) were tested for imipenem, meropenem, and polymyxin B susceptibility by minimum inhibitory concentration (MIC) and for the presence of class A and B carbapenemases by multiplex PCR. Active surveillance of ICU environment was also performed. High prevalence of Acinetobacter related hospital acquired pneumonia (HAP) with significant resistance to imipenem (p<0.05) and 88.02% MDR and 61.97% XDR was detected along with persistence in the ICU environment. The isolates harbored bla_IMP (89%), bla_VIM (51%), bla_NDM-1 (34%), and bla_OXA-23-like (93%) genes. Specific interventional measures should be adopted to control these imipenem resistant Acinetobacter spp. which have attained the level of endemicity in our ICU setup.

Temporal trends and patterns in antimicrobial-resistant Gram-negative bacteria implicated in intensive care unit-acquired infections: A cohort-based surveillance study in Istanbul, Turkey

OBJECTIVES

This study assessed trends and patterns in antimicrobial-resistant intensive care unit (ICU)-acquired infections caused by Gram-negative bacteria (GNB) in Istanbul, Turkey.

METHODS

Bacterial culture and antimicrobial susceptibility data were collected for all GNB causing nosocomial infections in five adult ICUs of a large university hospital in 2012-2015. Multiresistance patterns were categorised as multidrug-resistant (MDR), extensively drug-resistant (XDR) and pandrug-resistant (PDR). Temporal patterns and trends were assessed using regression analyses.

RESULTS

Of 991 pathogenic GNB recorded, the most frequent were Acinetobacter baumannii (35.3%), Klebsiella spp. (26.7%), Pseudomonas aeruginosa (18.1%) and Escherichia coli (6.7%). The overall infection rate decreased by 41% from 18.4 to 10.9 cases per 1000 patient-days in 2012 compared with 2015 (P<0.001), mostly representing decreases in bloodstream infections and pneumonias by A. baumannii and P. aeruginosa. The XDR proportion in A. baumannii increased from 52.4% in 2012 to 71.7% in 2015, but only one isolate was colistin-resistant. Multiresistance patterns remained stable in Klebsiella, with overall XDR and possible PDR proportions of 14.3% and 1.9%, respectively. A back-to-susceptibility trend was noted for P. aeruginosa in which the non-MDR proportion increased from 53.3% in 2012 to 70.6% in 2015. Moreover, 87.9% of E. coli and 39.5% of Enterobacter isolates were MDR, but none was XDR.

CONCLUSIONS

Antimicrobial resistance patterns in pathogenic GNB continuously change over time and may not reflect single-agent resistance trends. The proportionate amount of antimicrobial-resistant GNB may persist despite overall decreasing infection rates. Timely regional surveillance data are thus imperative for optimal infection control.

Predator Versus Pathogen: How Does Predatory Bdellovibrio bacteriovorus Interface with the Challenges of Killing Gram-Negative Pathogens in a Host Setting?

Bdellovibrio bacteriovorus is a small deltaproteobacterial predator that has evolved to invade, reseal, kill, and digest other gram-negative bacteria in soils and water environments. It has a broad host range and kills many antibiotic-resistant, clinical pathogens in vitro, a potentially useful capability if it could be translated to a clinical setting. We review relevant mechanisms of B. bacteriovorus predation and the physiological properties that would influence its survival in a mammalian host. Bacterial pathogens increasingly display conventional antibiotic resistance by expressing and varying surface and soluble biomolecules. Predators coevolved alongside prey bacteria and so encode diverse predatory enzymes that are hard for pathogens to resist by simple mutation. Predators do not replicate outside pathogens and thus express few transport proteins and thus few surface epitopes for host immune recognition. We explain these features, relating them to the potential of predatory bacteria as cellular medicines.

Antibacterial naphthoquinone derivatives targeting resistant strain Gram-negative bacteria in biofilms

The aims of this study were the planning, synthesis and in vitro evaluation of 2-hydroxy-3-phenylsulfanylmethyl-[1,4]-naphthoquinones against Gram-negative and Gram-positive strains, searching for potential lead compounds against bacterial biofilm formation. A series of 12 new analogs of 2-hydroxy-3-phenylsulfanylmethyl-[1,4]-naphthoquinones were synthesized by adding a thiol and different substituents to a ο-quinone methide using microwave irradiation. The compounds were tested against Gram-positive (Enterococcus faecalis ATCC 29212, Staphylococcus aureus ATCC 25923, S. simulans ATCC 27851, S. epidermidis ATCC 12228 and a hospital Methicillin-resistant S. aureus (MRSA) strain), as well as Gram-negative (Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, P. aeruginosa ATCC 15442, Proteus mirabilis ATCC 15290, Serratia marcescens ATCC 14756, Klebsiella pneumoniae ATCC 4352 and Enterobacter cloacae ATCC 23355) strains, using the disk diffusion method. Ten compounds showed activity mainly against Gram-negative strains with a minimal inhibitory concentration (MIC = 4-64 μg/mL) within the Clinical and Laboratory Standards Institute (CLSI) levels. The biofilm inhibition data showed compounds, 9e, 9f, 9j and 9k, are anti-biofilm molecules when used in sub-MIC concentrations against P. aeruginosa ATCC 15442 strain. Compound (9j) inhibited biofilm formation up to 63.4% with a better profile than ciprofloxacin, which is not able to prevent biofilm formation effectively. The reduction of P. aeruginosa ATCC 15442 mature biofilms was also observed for 9e and 9k. The structure modification applied in the series resulted in 12 new naphthoquinones with antimicrobial activity against Gram-negative bacteria strains (E. coli ATCC 25922, P. aeruginosa ATCC 27853 and ATCC 15442). Four compounds decreased P. aeruginosa biofilm formation effectively.

Attaching NorA efflux pump inhibitors to methylene blue enhances antimicrobial photodynamic inactivation of Escherichia coli and Acinetobacter baumannii in vitro and in vivo

Resistance of bacteria to antibiotics is a public health concern worldwide due to the increasing failure of standard antibiotic therapies. Antimicrobial photodynamic inactivation (aPDI) is a promising non-antibiotic alternative for treating localized bacterial infections that uses non-toxic photosensitizers and harmless visible light to produce reactive oxygen species and kill microbes. Phenothiazinium photosensitizers like methylene blue (MB) and toluidine blue O are hydrophobic cations that are naturally expelled from bacterial cells by multidrug efflux pumps, which reduces their effectiveness. We recently reported the discovery of a NorA efflux pump inhibitor-methylene blue (EPI-MB) hybrid compound INF55-(Ac)en-MB that shows enhanced photodynamic inactivation of the Gram-positive bacterium methicillin-resistant Staphylococcus aureus (MRSA) relative to MB, both in vitro and in vivo. Here, we report the surprising observation that INF55-(Ac)en-MB and two related hybrids bearing the NorA efflux pump inhibitors INF55 and INF271 also show enhanced aPDI activity in vitro (relative to MB) against the Gram-negative bacteria Escherichia coli and Acinetobacter baumannii, despite neither species expressing the NorA pump. Two of the hybrids showed superior effects to MB in murine aPDI infection models. The findings motivate wider exploration of aPDI with EPI-MB hybrids against Gram-negative pathogens and more detailed studies into the molecular mechanisms underpinning their activity.

Comprehensive volatile metabolic fingerprinting of bacterial and fungal pathogen groups

The identification of pathogen-specific volatile metabolic 'fingerprints' could lead to the rapid identification of disease-causing organisms either directly from ex vivo patient bio-specimens or from in vitro cultures. In the present study, we have evaluated the volatile metabolites produced by 100 clinical isolates belonging to ten distinct pathogen groups that, in aggregate, account for 90% of bloodstream infections, 90% of urinary tract infections, and 80% of infections encountered in the intensive care unit setting. Headspace volatile metabolites produced in vitro were concentrated using headspace solid-phase microextraction and analyzed via two-dimensional gas chromatography time-of-flight mass spectrometry (HS-SPME-GC×GC-TOFMS). A total of 811 volatile metabolites were detected across all samples, of which 203 were: (1) detected in 9 or 10 (of 10) isolates belonging to one or more pathogen groups, and (2) significantly more abundant in cultures relative to sterile media. Network analysis revealed a distinct metabolic fingerprint associated with each pathogen group, and analysis via Random Forest using leave-one-out cross-validation resulted in a 95% accuracy for the differentiation between groups. The present findings support the results of prior studies that have reported on the differential production of volatile metabolites across pathogenic bacteria and fungi, and provide additional insight through the inclusion of pathogen groups that have seldom been studied previously, including Acinetobacter spp., coagulase-negative Staphylococcus, and Proteus mirabilis, as well as the utilization of HS-SPME-GC×GC-TOFMS for improved sensitivity and resolution relative to traditional gas chromatography-based techniques.

Defining the Relationship Between Phenotypic and Genotypic Resistance Profiles of Multidrug-Resistant Enterobacterial Clinical Isolates

Fluoroquinolones and aminoglycosides offer effective therapy for extended-spectrum beta-lactamase (ESBL)-producing enterobacterial infections, but their usefulness is threatened by increasing resistant strains.

OBJECTIVE

This study was conducted to demonstrate the phenotypic outcomes of the coexistence of genetic determinants mediating resistance to extended-spectrum cephalosporins and quinolones in enterobacterial isolates collected from patients with health-care-associated infections in Egypt.

METHODS

ESBL phenotype was determined using double-disk synergy test (DDST). The PCR technique was used to detect the presence of the genes mediating quinolone resistance (qnr and aac(6')-Ib-cr) and coexistence with ESBL genes. We also examined the association between the genetic makeup of the isolates and their resistance profiles including effect on MIC results.

RESULTS

Phenotypically ESBLs were detected in 60-82% of the enterobacterial isolates. ESBL, qnr and aac(6')-Ib-cr genes were detected with the following percentages in Citrobacter isolates (69%, 69%, and 43%, respectively), E.coli isolates (65%, 70%, and 45%, respectively), Enterobacter isolates (56%, 67%, and 33%, respectively), and finally Klebsiella isolates (42%, 66%, and 25%, respectively). The coexistence of these multiresistant genetic elements significantly increased the MIC values of the tested antibiotics from different classes.

CONCLUSION

We suggest using blaTEM, blaCTX-M-15, qnr, and aac(6')-Ib-cr genes for better and faster prediction of suitable antibiotic therapy with effective doses against ESBL-producing isolates harboring plasmid-mediated quinolone resistance (PMQR) determinants. Amikacin, meropenem, gentamicin, and imipenem seem to be better choices of treatment for such life-threatening infections, because of their remaining highest activity.

Interleukin-36γ and IL-36 receptor signaling mediate impaired host immunity and lung injury in cytotoxic Pseudomonas aeruginosa pulmonary infection: Role of prostaglandin E2

Pseudomonas aeruginosa is a Gram-negative pathogen that can lead to severe infection associated with lung injury and high mortality. The interleukin (IL)-36 cytokines (IL-36α, IL-36β and IL-36γ) are newly described IL-1 like family cytokines that promote inflammatory response via binding to the IL-36 receptor (IL-36R). Here we investigated the functional role of IL-36 cytokines in the modulating of innate immune response against P. aeruginosa pulmonary infection. The intratracheal administration of flagellated cytotoxic P. aeruginosa (ATCC 19660) upregulated IL-36α and IL-36γ, but not IL-36β, in the lungs. IL-36α and IL-36γ were expressed in pulmonary macrophages (PMs) and alveolar epithelial cells in response to P. aeruginosa in vitro. Mortality after bacterial challenge in IL-36 receptor deficient (IL-36R-/-) mice and IL-36γ deficient (IL-36γ-/-) mice, but not IL-36α deficient mice, was significantly lower than that of wild type mice. Decreased mortality in IL-36R-/- mice and IL-36γ-/- mice was associated with reduction in bacterial burden in the alveolar space, bacterial dissemination, production of inflammatory cytokines and lung injury, without changes in lung leukocyte influx. Interestingly, IL-36γ enhanced the production of prostaglandin E2 (PGE2) during P. aeruginosa infection in vivo and in vitro. Treatment of PMs with recombinant IL-36γ resulted in impaired bacterial killing via PGE2 and its receptor; EP2. P. aeruginosa infected EP2 deficient mice or WT mice treated with a COX-2-specific inhibitor showed decreased bacterial burden and dissemination, but no change in lung injury. Finally, we observed an increase in IL-36γ, but not IL-36α, in the airspace and plasma of patients with P. aeruginosa-induced acute respiratory distress syndrome. Thus, IL-36γ and its receptor signal not only impaired bacterial clearance in a possible PGE2 dependent fashion but also mediated lung injury during P. aeruginosa infection.

Antimicrobial Activity of Ceftazidime-Avibactam Tested against Multidrug-Resistant Enterobacteriaceae and Pseudomonas aeruginosa Isolates from U.S. Medical Centers, 2013 to 2016

The in vitro activity of ceftazidime-avibactam and many comparator agents was determined against various resistant subsets of organisms selected among 36,380 Enterobacteriaceae and 7,868 Pseudomonas aeruginosa isolates. The isolates were consecutively collected from 94 U.S. hospitals, and all isolates were tested for susceptibility by reference broth microdilution methods in a central monitoring laboratory (JMI Laboratories). Enterobacteriaceae isolates resistant to carbapenems (CRE) and/or ceftazidime-avibactam (MIC ≥ 16 μg/ml) were evaluated for the presence of genes encoding extended-spectrum β-lactamases and carbapenemases. Ceftazidime-avibactam inhibited >99.9% of all Enterobacteriaceae at the susceptible breakpoint of ≤8 μg/ml and was active against multidrug-resistant (MDR; n = 2,953; MIC50/90, 0.25/1 μg/ml; 99.2% susceptible), extensively drug-resistant (XDR; n = 448; MIC50/90, 0.5/2 μg/ml; 97.8% susceptible), and CRE (n = 513; MIC50/90, 0.5/2 μg/ml; 97.5% susceptible) isolates. Only 82.2% of MDR Enterobacteriaceae (n = 2,953) and 64.2% of ceftriaxone-nonsusceptible Klebsiella pneumoniae (n = 1,063) isolates were meropenem susceptible. Among Enterobacter cloacae (22.2% ceftazidime nonsusceptible), 99.8% of the isolates, including 99.3% of the ceftazidime-nonsusceptible isolates, were ceftazidime-avibactam susceptible. Only 23 of 36,380 Enterobacteriaceae (0.06%) isolates were ceftazidime-avibactam nonsusceptible, including 9 metallo-β-lactamase producers and 2 KPC-producing strains with porin alteration; the remaining 12 strains showed negative results for all β-lactamases tested. Ceftazidime-avibactam showed potent activity against P. aeruginosa (MIC50/90, 2/4 μg/ml; 97.1% susceptible), including MDR (MIC50/90, 4/16 μg/ml; 86.5% susceptible) isolates, and inhibited 71.8% of isolates nonsusceptible to meropenem, piperacillin-tazobactam, and ceftazidime (n = 628). In summary, ceftazidime-avibactam demonstrated potent activity against a large collection (n = 44,248) of contemporary Gram-negative bacilli isolated from U.S. patients, including organisms resistant to most currently available agents, such as CRE and meropenem-nonsusceptible P. aeruginosa.

Strengthening infection prevention and control and systematic surveillance of healthcare associated infections in India

Establishing and expanding government led networks to strengthen infection prevention and control and healthcare associated infection surveillance are essential to effectively tackle antimicrobial resistance. Soumya Swaminathan and colleagues discuss the progress in India

Measuring and modelling the response of Klebsiella pneumoniae KPC prey to Bdellovibrio bacteriovorus predation, in human serum and defined buffer

In worldwide conditions of increasingly antibiotic-resistant hospital infections, it is important to research alternative therapies. Bdellovibrio bacteriovorus bacteria naturally prey on Gram-negative pathogens, including antibiotic-resistant strains and so B. bacteriovorus have been proposed as "living antibiotics" to combat antimicrobially-resistant pathogens. Predator-prey interactions are complex and can be altered by environmental components. To be effective B. bacteriovorus predation needs to work in human body fluids such as serum where predation dynamics may differ to that studied in laboratory media. Here we combine mathematical modelling and lab experimentation to investigate the predation of an important carbapenem-resistant human pathogen, Klebsiella pneumoniae, by B. bacteriovorus in human serum versus buffer. We show experimentally that B. bacteriovorus is able to reduce prey numbers in each environment, on different timescales. Our mathematical model captures the underlying dynamics of the experimentation, including an initial predation-delay at the predator-prey-serum interface. Our research shows differences between predation in buffer and serum and highlights both the potential and limitations of B. bacteriovorus acting therapeutically against K. pneumoniae in serum, informing future research into the medicinal behaviours and dosing of this living antibacterial.

Analysis of distribution and antibiotic resistance of pathogens isolated from the paediatric population in Shenmu Hospital from 2011-2015

Objective

This study aimed to investigate the epidemiology and changes in antibacterial susceptibility of children in Shenmu City, northern Shaanxi, and provide a basis for rational drug use.

Methods

The distribution and drug resistance pattern of pathogenic bacteria isolated from children were retrospectively analysed.

Results

A total of 573 strains of pathogens were cultivated. A total of 201 (35.07%) strains of Gram-positive cocci and 183 (31.93%) strains of Gram-negative cocci were detected. A total of 189 (32.98%) strains of fungi were detected. The resistance rate of Staphylococcus to penicillin was 100% and that to erythromycin was 90.69%. There were varying degrees of resistance to other drugs, but no single strain had vancomycin resistance. Gram-negative bacilli were generally resistant to ampicillin, but had low resistance to the combined preparation of enzyme inhibitors, quinolones, and aminoglycosides, and were highly sensitive to imipenem and meropenem.

Conclusion

Gram-negative bacilli are the main pathogens of bacterial infection in the paediatric ward. Strengthening clinical monitoring of bacterial distribution in paediatric clinical isolates and understanding changes in drug resistance are important for guiding the rational use of antibiotics. These measures could also prevent emergence and spreading of resistant strains.

High burden of antimicrobial resistance among gram negative bacteria causing healthcare associated infections in a critical care unit of Nepal

Background

Healthcare associated infections (HCAI) and antimicrobial resistance are principal threats to the patients of intensive care units and are the major determining factors for patient outcome. They are associated with increased morbidity, mortality, excess hospitalization and financial costs. The present study is an attempt to investigate the spectrum and antimicrobial resistance of bacterial isolates involved in healthcare associated infections (HCAI) in the patients of a critical care unit at a tertiary care university hospital in Kathmandu, Nepal.

Methods

A laboratory based study was conducted over the period of 15 months (January 2014 to March 2015) among the patients of intensive care unit of Tribhuvan University Teaching Hospital, Kathmandu, Nepal. Clinical specimens from patients with suspected healthcare-associated infection were processed and bacterial isolates were identified with standard microbiological methods. Antimicrobial susceptibilities of the isolated strains were determined according to the CLSI guidelines and β-lactamases (ESBL, AmpC, MBL and KPC) were detected by various phenotypic tests.

Results

One hundred and forty nine clinical specimens received from 135 patients suspected of HCAI (out of 491 patients) were found with significant bacterial growth. Specimens were from patients suspected of hospital-acquired pneumonia (16%, 79/491), bloodstream infections (5.7%, 28/491), surgical site infections (4.7%, 23/491), and urinary tract infections (3.9%, 19/491). Acinetobacter spp., Klebsiella spp., Escherichia coli and Burkholderia cepacia were the leading bacterial pathogens. Extremely high level of drug resistance (95.8%) along with the production of β-lactamases (ESBL; 43.7%, AmpC; 27.5%), MBL; 50.2% and KPC; 4.2%) was observed among Gram negative bacterial isolates.

Conclusion

Healthcare associated infections are very common in our ICU. Gram negative bacterial pathogens are major culprits associated with these infections and there is alarming state of drug resistance among these isolates. Continuous surveillance and establishment of preventive and control measures of healthcare associated infections are urgently needed in our setting.

Synthesis and antimicrobial evaluation of promising 7-arylamino-5,8-dioxo-5,8-dihydroisoquinoline-4-carboxylates and their halogenated amino compounds for treating Gram-negative bacterial infections

In this work we described the synthesis and antimicrobial evaluation of 7-arylamino-5,8-dioxo-5,8-dihydroisoquinoline-4-carboxylates derivatives that exhibited remarkable activity against two Gram-negative strains of clinical importance.

Polydopamine Hollow Nanoparticle Functionalized with N-diazeniumdiolates as a Nitric Oxide Delivery Carrier for Antibacterial Therapy

A biocompatible nitric oxide (NO) delivery nanoplatform, whose structure is a hollow nanoparticle composed of polydopamine backbone and diazeniumdiolates functional groups, is developed for antibacterial therapy. This platform liberates high NO quantitis and exerts the antibacterial activity with excellent biocompatibility thus being promising for treating bacterial infections.

Time trends in the aetiology of prosthetic joint infections: a multicentre cohort study

It is important to know the spectrum of the microbial aetiology of prosthetic joint infections (PJIs) to guide empiric treatment and establish antimicrobial prophylaxis in joint replacements. There are no available data based on large contemporary patient cohorts. We sought to characterize the causative pathogens of PJIs and to evaluate trends in the microbial aetiology. We hypothesized that the frequency of antimicrobial-resistant organisms in PJIs has increased in the recent years. We performed a cohort study in 19 hospitals in Spain, from 2003 to 2012. For each 2-year period (2003-2004 to 2011-2012), the incidence of microorganisms causing PJIs and multidrug-resistant bacteria was assessed. Temporal trends over the study period were evaluated. We included 2524 consecutive adult patients with a diagnosis of PJI. A microbiological diagnosis was obtained for 2288 cases (90.6%). Staphylococci were the most common cause of infection (1492, 65.2%). However, a statistically significant rising linear trend was observed for the proportion of infections caused by Gram-negative bacilli, mainly due to the increase in the last 2-year period (25% in 2003-2004, 33.3% in 2011-2012; p 0.024 for trend). No particular species contributed disproportionally to this overall increase. The percentage of multidrug-resistant bacteria PJIs increased from 9.3% in 2003-2004 to 15.8% in 2011-2012 (p 0.008), mainly because of the significant rise in multidrug-resistant Gram-negative bacilli (from 5.3% in 2003-2004 to 8.2% in 2011-2012; p 0.032). The observed trends have important implications for the management of PJIs and prophylaxis in joint replacements.

Identification of Genes Coding Aminoglycoside Modifying Enzymes in E. coli of UTI Patients in India

This study is to probe the pattern of antibiotic resistance against aminoglycosides and its mechanism in E. coli obtained from patients from Chennai, India. Isolation and identification of pathogens were done on MacConkey agar. Antimicrobial sensitivity testing was done by disc diffusion test. The identification of genes encoding aminoglycoside modifying enzymes was done by Polymerase Chain Reaction (PCR). Out of 98 isolates, 71 (72.45%) isolates were identified as E. coli and the remaining 27 (27.55%) as other bacteria. Disc diffusion method results showed a resistance level of 72.15% for streptomycin, 73.4% for gentamicin, 63.26% for neomycin, 57.14% for tobramycin, 47.9% for netilmicin, and 8.16% for amikacin in E. coli. PCR screening showed the presence of four genes, namely, rrs, aacC2, aacA-aphD, and aphA3, in their plasmid DNA. The results point towards the novel mechanism of drug resistance in E. coli from UTI patients in India as they confirm the presence of genes encoding enzymes that cause resistance to aminoglycoside drugs. This could be an alarm for drug prescription to UTI patients.

M-CSF Mediates Host Defense during Bacterial Pneumonia by Promoting the Survival of Lung and Liver Mononuclear Phagocytes

Gram-negative bacterial pneumonia is a common and dangerous infection with diminishing treatment options due to increasing antibiotic resistance among causal pathogens. The mononuclear phagocyte system is a heterogeneous group of leukocytes composed of tissue-resident macrophages, dendritic cells, and monocyte-derived cells that are critical in defense against pneumonia, but mechanisms that regulate their maintenance and function during infection are poorly defined. M-CSF has myriad effects on mononuclear phagocytes but its role in pneumonia is unknown. We therefore tested the hypothesis that M-CSF is required for mononuclear phagocyte-mediated host defenses during bacterial pneumonia in a murine model of infection. Genetic deletion or immunoneutralization of M-CSF resulted in reduced survival, increased bacterial burden, and greater lung injury. M-CSF was necessary for the expansion of lung mononuclear phagocytes during infection but did not affect the number of bone marrow or blood monocytes, proliferation of precursors, or recruitment of leukocytes to the lungs. In contrast, M-CSF was essential to survival and antimicrobial functions of both lung and liver mononuclear phagocytes during pneumonia, and its absence resulted in bacterial dissemination to the liver and hepatic necrosis. We conclude that M-CSF is critical to host defenses against bacterial pneumonia by mediating survival and antimicrobial functions of mononuclear phagocytes in the lungs and liver.

Specific Gene Loci of Clinical Pseudomonas putida Isolates

Pseudomonas putida are ubiquitous inhabitants of soils and clinical isolates of this species have been seldom described. Clinical isolates show significant variability in their ability to cause damage to hosts because some of them are able to modulate the host’s immune response. In the current study, comparisons between the genomes of different clinical and environmental strains of P. putida were done to identify genetic clusters shared by clinical isolates that are not present in environmental isolates. We show that in clinical strains specific genes are mostly present on transposons, and that this set of genes exhibit high identity with genes found in pathogens and opportunistic pathogens. The set of genes prevalent in P. putida clinical isolates, and absent in environmental isolates, are related with survival under oxidative stress conditions, resistance against biocides, amino acid metabolism and toxin/antitoxin (TA) systems. This set of functions have influence in colonization and survival within human tissues, since they avoid host immune response or enhance stress resistance. An in depth bioinformatic analysis was also carried out to identify genetic clusters that are exclusive to each of the clinical isolates and that correlate with phenotypical differences between them, a secretion system type III-like was found in one of these clinical strains, a determinant of pathogenicity in Gram-negative bacteria.

Burkholderia Sepsis in Children as a Hospital-Acquired Infection

PURPOSE

Hospital-acquired Burkholderia cepacia (B. cepacia) infection are not commonly recorded in patients without underlying lung disease, such as cystic fibrosis and chronic granulomatous disease. However, in 2014, B. cepacia appeared more frequently in pediatric blood samples than in any other year. In order to access this situation, we analyzed the clinical characteristics of B. cepacia infections in pediatric patients at our hospital.

MATERIALS AND METHODS

We conducted a retrospective study of blood isolates of B. cepacia taken at our hospital between January 2004 and December 2014. Patient clinical data were obtained by retrospective review of electronic medical records. We constructed a dendrogram for B. cepacia isolates from two children and five adult patients.

RESULTS

A total of 14 pediatric patients and 69 adult patients were identified as having B. cepacia bacteremia. In 2014, higher rates of B. cepacia bacteremia were observed in children. Most of them required Intensive Care Unit (ICU) care (12/14). In eleven children, sputum cultures were examined, and five of these children had the same strain of B. cepacia that grew out from their blood samples. Antibiotics were administered based on antibiotic sensitivity results. Four children expired despite treatment. Compared to children, there were no demonstrative differences in adults, except for history of ICU care.

CONCLUSION

Although there were not many pediatric cases at our hospital, awareness of colonization through hospital-acquired infection and effective therapy for infection of B. cepacia is needed, as it can cause mortality and morbidity.