A comparison of microbiology and demographics among patients with healthcare-associated, hospital-acquired, and ventilator-associated pneumonia: a retrospective analysis of 1184 patients from a large, international study

Efficacy and safety of different polymyxin-containing regimens for the treatment of pneumonia caused by multidrug-resistant gram-negative bacteria: a systematic review and network meta-analysis

BACKGROUND

The optimal administration of polymyxins for treating multidrug-resistant gram-negative bacterial (MDR-GNB) pneumonia remains unclear. This study aimed to systematically assess the efficacy and safety of three polymyxin-containing regimens by conducting a comprehensive network meta-analysis.

METHODS

We comprehensively searched nine databases. Overall mortality was the primary outcome, whereas the secondary outcomes encompassed microbial eradication rate, clinical success, acute kidney injury, and incidence of bronchospasm. Extracted study data were analyzed by pairwise and network meta-analyses. Version 2 of the Cochrane risk-of-bias tool and the Risk of Bias in Nonrandomized Studies of Interventions (ROBINS-I) assessment tool were used to assess the risk of bias in randomized trials and cohort studies, respectively.

RESULTS

This study included 19 observational studies and 3 randomized controlled trials (RCTs), encompassing 3318 patients. Six studies with high risk of bias were excluded from the primary analysis. In the pairwise meta-analysis, compared to the intravenous (IV) polymyxin-containing regimen, the intravenous plus inhaled (IV + IH) polymyxin-containing regimen showed a significant decrease in overall mortality, while no statistically significant difference was found in the inhaled (IH) polymyxin-containing regimen. The network meta-analysis indicated that the IV + IH polymyxin-containing regimen had significantly lower overall mortality (OR 0.67; 95% confidence interval [CI] 0.50-0.88), higher clinical success rate (OR 1.90; 95% CI 1.20-3.00), better microbial eradication rate (OR 2.70; 95% CI 1.90-3.90) than the IV polymyxin-containing regimen, and significantly better microbial eradication rate when compared with the IH polymyxin-containing regimen (OR 2.30; 95% CI 1.30-4.20). Furthermore, compared with IV + IH and IV polymyxin-containing regimens, the IH polymyxin-containing regimen showed a significant reduction in acute kidney injury.

CONCLUSIONS

Our study indicates that among the three administration regimens, the IV + IH polymyxin-containing regimen may be the most effective for treating MDR-GNB pneumonia, with a significantly lower overall mortality compared to the IV regimen and a considerably higher microbial eradication rate compared to the IH regimen. The IH regimen may be considered superior to the IV regimen due to its substantially lower incidence of acute kidney injury, even though the reduction in overall mortality was not significant.

In search of the best method to detect carriage of carbapenem-resistant Pseudomonas aeruginosa in humans: a systematic review

BACKGROUND

Detection of carbapenem-resistant Pseudomonas aeruginosa (CR-PA) in humans is important to prevent transmission. However, the most optimal culture method to detect CR-PA is unknown. This systematic review aims to determine which culture method is most sensitive and which culture methods are used to detect CR-PA in humans. Second, to establish the most feasible culture method taking into account the turnaround time (TAT), and third, to provide an overview of the sampling sites used to detect carriage.

METHODS

We systematically searched the electronic databases Embase, Medline Ovid, Cochrane, Scopus, CINAHL, and Web of Science until January 27, 2023. All diagnostic accuracy studies comparing two or more culture methods to detect CR-PA and recent outbreak or surveillance reports on CR-PA carriage or infection in humans, which describe culture methods and their results, were eligible for inclusion. We used QUADAS-2 guideline for diagnostic accuracy studies and the STROBE or ORION guideline for outbreak-surveillance studies to assess the risk of bias.

RESULTS

Six diagnostic accuracy studies were included. An enrichment broth was found to increase the detection of CR-PA. Using an enrichment broth extended the TAT by 18-24 h, yet selective media could reduce the TAT by 24 h compared to routine media. In total, 124 outbreak-surveillance studies were included, of which 17 studies with surveillance samples and 116 studies with clinical samples. In outbreak-surveillance studies with surveillance samples, perianal, rectal swabs or stools were the most common sampling site/specimen (13/17, 76%). A large variety was observed in whether and which kind of enrichment broth and selective media were used.

CONCLUSIONS

We found a benefit of using an enrichment step prior to inoculation of the material onto selective media for the detection of CR-PA. More research is needed to determine the most sensitive sampling site and culture method.

TRAIL REGISTRATION

This study was registered in the PROSPERO International prospective register of systematic reviews (registration number: CRD42020207390, http://www.crd.york.ac.uk/PROSPERO/display_record.asp?ID=CRD42020207390 ).

Extensively drug-resistant Pseudomonas aeruginosa: clinical features and treatment with ceftazidime/avibactam and ceftolozane/tazobactam in a tertiary care university hospital center in Portugal - A cross-sectional and retrospective observational study

Introduction

Extensively drug-resistant Pseudomonas aeruginosa (XDR-PA) is a growing concern due to its increasing incidence, limited therapeutic options, limited data on the optimal treatment, and high mortality rates. The study aimed to characterize the population, the outcome and the microbiological characteristics of XDR-PA identified in a Portuguese university hospital center.

Methods

All XDR-PA isolates between January 2019 and December 2021 were identified. XDR-PA was defined as resistance to piperacillin-tazobactam, third and fourth generation cephalosporins, carbapenems, aminoglycosides and fluoroquinolones. A retrospective analysis of the medical records was performed.

Results

One hundred seventy-eight individual episodes among 130 patients with XDR-PA detection were identified. The most common sources of infection were respiratory (32%) and urinary tracts (30%), although skin and soft tissue infections (18%) and primary bacteremia (14%) were also prevalent. Colonization was admitted in 64 cases. Several patients had risk factors for complicated infections, most notably immunosuppression, structural lung abnormalities, major surgery, hemodialysis or foreign intravascular or urinary devices. XDR-PA identification was more frequent in male patients with an average age of 64.3 ± 17.5 years. One non-susceptibility to colistin was reported. Only 12.4% were susceptible to aztreonam. Ceftazidime-avibactam (CZA) was susceptible in 71.5% of the tested isolates. Ceftolozane-tazobactam (C/T) was susceptible in 77.5% of the tested isolates. Antibiotic regimens with XDR-PA coverage were reserved for patients with declared infection, except to cystic fibrosis. The most frequently administered antibiotics were colistin (41 cases), CZA (39 cases), and C/T (16 cases). When combination therapy was used, CZA plus colistin was preferred. The global mortality rate among infected patients was 35.1%, significantly higher in those with hematologic malignancy (50.0%, p < 0.05), followed by the ones with bacteremia (44.4%, p < 0.05) and those medicated with colistin (39.0%, p < 0.05), especially the ones with respiratory infections (60.0%). Among patients treated with CZA or C/T, the mortality rate seemed to be lower.

Discussion

XDR-PA infections can be severe and difficult to treat, with a high mortality rate. Even though colistin seems to be a viable option, it is likely less safe and efficient than CZA and C/T. To the best of the authors' knowledge, this is the first description of the clinical infection characteristics and treatment of XDR-PA in Portugal.

Increased ompW and ompA expression and higher virulence of Acinetobacter baumannii persister cells

BACKGROUND

Acinetobacter baumannii is one of the main causes of healthcare-associated infections that threaten public health, and carbapenems, such as meropenem, have been a therapeutic option for these infections. Therapeutic failure is mainly due to the antimicrobial resistance of A. baumannii, as well as the presence of persister cells. Persisters constitute a fraction of the bacterial population that present a transient phenotype capable of tolerating supra-lethal concentrations of antibiotics. Some proteins have been suggested to be involved in the onset and/or maintenance of this phenotype. Thus, we investigated the mRNA levels of the adeB (AdeABC efflux pump component), ompA, and ompW (outer membrane proteins) in A. baumannii cells before and after exposure to meropenem.

RESULTS

We found a significant increase (p-value < 0.05) in the expression of ompA (> 5.5-fold) and ompW (> 10.5-fold) in persisters. However, adeB did not show significantly different expression levels when comparing treated and untreated cells. Therefore, we suggest that these outer membrane proteins, especially OmpW, could be part of the mechanism of A. baumannii persisters to deal with the presence of high doses of meropenem. We also observed in the Galleria mellonella larvae model that persister cells are more virulent than regular ones, as evidenced by their LD₅₀ values.

CONCLUSIONS

Taken together, these data contribute to the understanding of the phenotypic features of A. baumannii persisters and their relation to virulence, as well as highlight OmpW and OmpA as potential targets for drug development against A. baumannii persisters.

Efficacy and safety of intravenous combined with aerosolised polymyxin versus intravenous polymyxin alone in the treatment of multidrug-resistant gram-negative bacterial pneumonia: A systematic review and meta-analysis

Background

Previous studies have questioned the efficacy and safety of intravenous combined with aerosolised (IV + AS) polymyxin versus intravenous (IV) polymyxin alone in the treatment of patients with multidrug-resistant gram-negative bacterial (MDR-GNB) pneumonia. Therefore, we conducted a meta-analysis to evaluate the efficacy and safety of IV + AS polymyxin in the treatment of MDR-GNB pneumonia.

Methods

We identified all relevant studies by searching the PubMed, EMBASE and Cochrane library databases from their inception to May 31, 2022. All included studies were evaluated using the Newcastle Ottawa scale (NOS) checklist. The summary relative risk (RR) and 95% confidence interval (CI) were used to determine the outcome differences between the IV + AS and the IV groups. Subgroup analysis was performed based on population, polymyxin dose and kinds of polymyxin.

Results

A total of 16 studies were included in the meta-analysis. The IV + AS group had lower mortality (RR = 0.86, 95% CI: 0.77-0.97, P = 0.01) than the IV group. Subgroup analysis revealed that IV + AS polymyxin could reduce mortality only when used in low doses. Simultaneously, the IV + AS group outperformed the IV group in terms of clinical response rate, clinical cure rate, microbiological eradication and duration of mechanical ventilation. The duration of hospitalisation and the incidence of nephrotoxicity did not differ significantly between the two groups.

Conclusions

IV + AS polymyxin is beneficial in the treatment of MDR-GNB pneumonia. It could lower patient mortality and improve clinical and microbial outcomes without increasing the risk of nephrotoxicity. However, retrospective analysis in the majority of studies and heterogeneity between studies implies that our findings must be interpreted carefully.

Association between histo-blood group antigens and Pseudomonas aeruginosa-associated diarrheal diseases

BACKGROUND

Pseudomonas aeruginosa is not a common enteric pathogen. The association between human histo-blood group antigens (HBGAs) and P. aeruginosa enteric infection has not yet been studied.

METHODS

We collected stool samples from healthy children under 2 years of age for P. aeruginosa gut colonization rate. Saliva samples were collected from patients with P. aeruginosa-associated diarrheal diseases and normal healthy children. Genomic DNA was extracted from saliva samples for ABO blood group typing and FUT2 genotyping. Lewis phenotype was detected using ELISA assay.

RESULTS

A total of 85 patients with P. aeruginosa-associated diarrheal diseases and 105 healthy children were enrolled for collecting saliva specimens. The stool colonization rate was 5/101 (5%) in healthy children, 4/58 (6.9%) in infants, and 1/43 (2.3%) in children 1-2 years old, respectively. Blood group A was more frequent in patients with P. aeruginosa-associated diarrheal diseases 24/77 (31.2%) than in healthy children 18/102 (17.6%) (P = 0.035). All patients and healthy children were secretor positive. The distribution of weak-secretor genotype Se³⁸⁵/Se³⁸⁵ was 23/84 (27.4%) in patients with P. aeruginosa-associated diarrheal diseases and 17/104 (16.3%) in healthy children, respectively (P = 0.06). Patients with P. aeruginosa-associated diarrheal diseases had a higher percentage of Le^a+b+ phenotype 25/81 (30.9%) than healthy children 17/105 (16.2%) (P = 0.018). There was no association between ABO or secretor or Lewis status with the clinical severity of P. aeruginosa-associated diarrheal diseases.

CONCLUSION

Infants had a higher gut P. aeruginosa colonization rate than children. Children with blood group A and Le^a+b+ phenotype are prone to P. aeruginosa-associated diarrheal diseases.

A 600 mg of fixed-dose linezolid in renally impaired patients versus 15 mg/kg intermittent dose-optimized vancomycin in renally non-impaired patients: A single centre retrospective analysis for adult patients with hospital-acquired pneumonia due to methicillin-resistant Staphylococcus aureus

OBJECTIVES

Both linezolid and vancomycin are approved by USFDA and IDSA guidelines for the management of nosocomial pneumonia due to methicillin-resistant Staphylococcus aureus (MRSA) in clinical practice. Baseline creatinine clearance is the criterion for prescribing vancomycin or linezolid for hospital-acquired pneumonia in our institution. However, patients with renal function impairment are far more difficult to manage in intensive care. Thus, the objectives of the study were to compare the clinical efficacy and safety of 600 mg of fixed-dose linezolid with intermittent dose-optimised vancomycin in hospital-acquired pneumonia due to MRSA and to evaluate parameters of clinical cure.

METHODS

Analysis of a review of patients' charts. Patients with creatinine clearance <80 ml/min received 600 mg linezolid/12 h (n = 139, LN cohort), and patients with creatinine clearance ≥80 ml/min received intravenous 15 mg/kg vancomycin/12 h for 1-2 weeks consecutively or 3 weeks in case of bacteremia (n = 152, VC cohort) for management of hospital-acquired pneumonia due to MRSA.

RESULTS

A 59% of patients from the LN cohort and 47% of patients from the VC cohort were clinically cured. Administration of systemic steroids (p = 0.0412) and ≥ 80 ml/min creatinine clearance (p = 0.0498) were the independent parameters for the clinical cure of patients. Nephrotoxicity was higher among patients of the VC cohort than the LN cohort (p = 0.0464). Treatment failed in 41% of patients from the LN cohort and in 53% of patients from the VC cohort (p = 0.0200).

CONCLUSIONS

A 600 mg of fixed-dose linezolid is an ideal alternative to intermittent dose-optimised vancomycin for better clinical outcomes for patients with hospital-acquired pneumonia due to MRSA, especially for patients with renal impairment.

An assessment of burden of hospital-acquired pneumonia among abdominal surgical patients in tertiary university hospital in Serbia: A matched nested case-control study

Background

In the population of abdominal surgical patients hospital-acquired pneumonia (HAP) significantly increases morbidity and mortality.

Patients and methods

Through regular hospital surveillance of patients who received abdominal operations, we identified postoperative HAP from 2007 to 2019. In an initial nested case-control study, every surgical patient with HAP was compared with three control patients without HAP. Control patients were matched to the cases by age, gender, the American Society of Anesthesiologists score, and type of surgical operation. Also, the patients with HAP, who died were compared with those who survived.

Results

Multivariate logistic regression analysis (MLRA) revealed that other postoperative infections, length of intensive care unit stay, use of H2RA, use of PPI/ H2RA, multiple transfusion, and use of vancomycin in surgical prophylaxis were independent RFs for occurrence of HAP. Also, MLRA identified that age, lenght of hospital stay, use of mechanical ventilation and ceftriaxone in HAP therapy were indepedenttly associated with poor outcome of HAP. All Acinetobacter baumannii isolates were resistant to aminoglycoside antimicrobial agents and showed carbapenem resistance. The most frequently used antibiotics in patients with HAP and without HAP were vancomycin and metronidazole, respectively.

Conclusion

Our study provided an insight into the burden of HAP in abdominal surgical patients, and highlighted several priority areas and targets for quality improvement.

Time Series Genomics of Pseudomonas aeruginosa Reveals the Emergence of a Hypermutator Phenotype and Within-Host Evolution in Clinical Inpatients

Pseudomonas aeruginosa, a common opportunistic pathogen, is one of the leading etiological agents of nosocomial infections. Many previous studies have reported the nosocomial transmission and epidemiology of P. aeruginosa infections. However, longitudinal studies regarding the dynamics of P. aeruginosa colonization and infection in health care settings are limited. We obtained longitudinal samples from aged patients with prolonged intensive care unit (ICU) stays (~4 to 19 months). P. aeruginosa was isolated from 71 samples obtained from seven patients and characterized by whole-genome sequencing. The P. aeruginosa isolates were assigned to 10 clonal complexes, and turnover of main clones was observed in sequential sputum samples from two patients. By comparing intraclonal genomic diversities, we identified two clones that had significantly higher numbers of single nucleotide polymorphisms and variations in homopolymeric sequences than the other clones, indicating a hypermutator phenotype. These hypermutator clones were associated with mutations T147I/G521S and P27L in the MutL protein, and their mutation rates were estimated to be 3.20 × 10-5 and 6.59 × 10-5 per year per nucleotide, respectively. We also identified 24 recurrently mutated genes that exhibited intraclonal diversity in two or more clones. Notably, one recurrent mutation, S698F in FptA, was observed in four clones. These findings suggest that convergent microevolution and adaption of P. aeruginosa occur in long-term ICU patients. IMPORTANCE Pseudomonas aeruginosa is a predominant opportunistic pathogen that causes nosocomial infections. Inappropriate empirical therapy can lead to prolonged hospital stays and increased mortality. In our study of sequential P. aeruginosa isolates from inpatients, high intrahost diversity was observed, including switching of clones and the emergence of a hypermutator phenotype. Recurrently mutated genes also suggested that convergent microevolution and adaption of P. aeruginosa occur in inpatients, and genomic diversity is associated with differences in multiple-drug-resistance profiles. Taken together, our findings highlight the importance of longitudinal surveillance of nosocomial P. aeruginosa clones.

Role of Host and Bacterial Lipids in Pseudomonas aeruginosa Respiratory Infections

The opportunistic pathogen Pseudomonas aeruginosa is one of the most common agents of respiratory infections and has been associated with high morbidity and mortality rates. The ability of P. aeruginosa to cause severe respiratory infections results from the coordinated action of a variety of virulence factors that promote bacterial persistence in the lungs. Several of these P. aeruginosa virulence mechanisms are mediated by bacterial lipids, mainly lipopolysaccharide, rhamnolipid, and outer membrane vesicles. Other mechanisms arise from the activity of P. aeruginosa enzymes, particularly ExoU, phospholipase C, and lipoxygenase A, which modulate host lipid signaling pathways. Moreover, host phospholipases, such as cPLA2α and sPLA2, are also activated during the infectious process and play important roles in P. aeruginosa pathogenesis. These mechanisms affect key points of the P. aeruginosa-host interaction, such as: i) biofilm formation that contributes to bacterial colonization and survival, ii) invasion of tissue barriers that allows bacterial dissemination, iii) modulation of inflammatory responses, and iv) escape from host defenses. In this mini-review, we present the lipid-based mechanism that interferes with the establishment of P. aeruginosa in the lungs and discuss how bacterial and host lipids can impact the outcome of P. aeruginosa respiratory infections.

Preexisting Trichinella spiralis infection attenuates the severity of Pseudomonas aeruginosa-induced pneumonia

Background

A range of helminth species involve the migration of developing larvae through the lung and establish chronic infections in the host that include potent immune regulatory effects. Trichinella spiralis is one of the most successful parasitic symbiotes. After released by intestinal female adult worms, newborn larvae of T. spiralis travel through the circulatory system to the lung and finally reach skeletal muscle cells. As unique inflammation modulator of intracellular parasitism, T. spiralis shows improved responses to autoimmune disease and viral pulmonary inflammation by exerting immunomodulatory effects on innate and adaptive immune cells.

Methodology/Principal findings

C57BL/6 mice were divided into four groups: uninfected; helminth- T. spiralis infected; P. aeruginosa infected; and co-infected. Mice infected with T. spiralis were incubated for 6 weeks, followed by P. aeruginosa intranasal inoculation. Bronchial alveolar lavage fluid, blood and lung samples were analyzed. We found that T. spiralis induced Th2 response in the mouse lung tissue, increased lung CD4⁺ T cells, GATA3, IL-4, IL-5 and IL-13 expression. Pre-existing T. spiralis infection decreased lung neutrophil recruitment, inflammatory mediator IL-1β and IL-6 expression and chemokine CXCL1 and CXCL2 release during P. aeruginosa- pneumonia. Furthermore, T. spiralis co-infected mice exhibited significantly more eosinophils at 6 hours following P. aeruginosa infection, ameliorated pulmonary inflammation and improved survival in P. aeruginosa pneumonia.

Conclusions

These findings indicate that a prior infection with T. spiralis ameliorates experimental pulmonary inflammation and improves survival in P. aeruginosa pneumonia through a Th2-type response with eosinophils.

Helminth infections elicit type 2 immunity, which influences host immune responses to additional threats, such as allergens, metabolic disease and other pathogens. Pseudomonas aeruginosa is one of the most common gram-negative pathogens causing pneumonia in immunocompromised patients. The mortality rate of ventilator associated pneumonia caused by P. aeruginosa is higher than that due to other pathogens. Trichinella spiralis is a zoonotic nematode of intracellular parasitism that infects a wide range of vertebrate hosts, including humans. There is a lung migratory phase in the life cycle of T. spiralis. In this study, we found that T. spiralis induced Th2 response in the mouse lung tissue. T. spiralis co-infected mice exhibited significantly more eosinophils and less neutrophils at 6 hours following P. aeruginosa infection, ameliorated pulmonary inflammation and improved survival in P. aeruginosa pneumonia. These findings suggest a pre-existing chronic helminth with a lung migration phase infection promotes the survival of bacterial airway co-infected host.

Microbiology, empiric therapy and its impact on the outcomes of nonventilated hospital-acquired, ventilated hospital-acquired, and ventilator-associated bacterial pneumonia in the United States, 2014-2019

OBJECTIVE

To explore whether microbiology profiles and the impact of inappropriate empiric treatment differ in the setting of hospital-acquired bacterial pneumonia that requires subsequent mechanical ventilation (vHABP) versus one that does not (nvHABP) versus ventilator-associated bacterial pneumonia (VABP).

DESIGN

Multicenter retrospective cohort study within Premier Research database, 2014-2019.

METHODS

We identified cases based on a previously published International Classification of Disease, Ninth Revision/Tenth Revision Clinical Modification (ICD-9/ICD-10-CM) algorithm, and we compared the 3 groups with respect to the bacterial pathogens isolated from their blood, sputum, or lower airway samples, and their respective rates of exposure to inappropriate empiric treatment. Using regression modeling we computed the effect of inappropriate empiric treatment on outcomes.

RESULTS

Among 17,819 patients who met enrollment criteria, 26.5% had nvHABP, 25.6% vHAPB, and 47.9% VABP. S. aureus (majority methicillin-susceptible) was the most frequently isolated organism, followed P. aeruginosa, K. pneumoniae, and E. coli with variations across the conditions. Rates of carbapenem resistance were highest in VABP (9.1%) and to third-generation cephalosporins in vHABP (14.9%). Patients with nvHABP were most likely to receive inappropriate empiric treatment (8.5%). Although inappropriate empiric treatment was associated with an increase in adjusted postinfection-onset hospital length of stay (2.3 days) and cost ($12,142), its greatest magnitude was in the nvHABP group (4.9 days, $13,147).

CONCLUSIONS

Substantial microbiologic differences exist among populations who suffer nvHABP, vHABP, and VABP, and inappropriate empiric treatment significantly worsens utilization outcomes. Given the moderate rates of carbapenem resistance and third-generation cephalosporin resistance, all patients require empiric coverage for a range of bacteria, including those targeting extended-spectrum β-lactamase and carbapenem resistance where appropriate.

Infections Due to Acinetobacter baumannii-calcoaceticus Complex: Escalation of Antimicrobial Resistance and Evolving Treatment Options

Bacteria within the genus Acinetobacter (principally A. baumannii-calcoaceticus complex [ABC]) are gram-negative coccobacilli that most often cause infections in nosocomial settings. Community-acquired infections are rare, but may occur in patients with comorbidities, advanced age, diabetes mellitus, chronic lung or renal disease, malignancy, or impaired immunity. Most common sites of infections include blood stream, skin/soft-tissue/surgical wounds, ventilator-associated pneumonia, orthopaedic or neurosurgical procedures, and urinary tract. Acinetobacter species are intrinsically resistant to multiple antimicrobials, and have a remarkable ability to acquire new resistance determinants via plasmids, transposons, integrons, and resistance islands. Since the 1990s, antimicrobial resistance (AMR) has escalated dramatically among ABC. Global spread of multidrug-resistant (MDR)-ABC strains reflects dissemination of a few clones between hospitals, geographic regions, and continents; excessive antibiotic use amplifies this spread. Many isolates are resistant to all antimicrobials except colistimethate sodium and tetracyclines (minocycline or tigecycline); some infections are untreatable with existing antimicrobial agents. AMR poses a serious threat to effectively treat or prevent ABC infections. Strategies to curtail environmental colonization with MDR-ABC require aggressive infection-control efforts and cohorting of infected patients. Thoughtful antibiotic strategies are essential to limit the spread of MDR-ABC. Optimal therapy will likely require combination antimicrobial therapy with existing antibiotics as well as development of novel antibiotic classes.

Emergence of blaNDM-1 and blaVIM producing Gram-negative bacilli in ventilator-associated pneumonia at AMR Surveillance Regional Reference Laboratory in India

INTRODUCTION

Ventilator-associated pneumonia (VAP) may be a life threatening nosocomial infection encountered in intensive care units. Currently the emergence of carbapenem-resistant Gram-negative pathogens has become worrisome threat worldwide.

MATERIAL AND METHODS

Endotracheal aspirates samples were collected from patients who were under mechanical ventilation for > 48 h. The bacterial isolates were identified by MALDI-TOF-MS and antibiotic susceptibility testing performed. All carbapenem resistant isolates were tested by Modified Hodge test (MHT), modified carbapenem inactivation method (mCIM), and EDTA-CIM (eCIM) and PCR were performed to detect blaIMP, blaVIM and blaNDM producing MBL genes.

RESULTS

VAP occurred in 172/353(48.7%), 23.3% had early-onset VAP and 76.7% had late-onset VAP. Males (69.2%) were found to suffer more from VAP. Prior antibiotic therapy, CPI>6, prior surgery and tracheostomy were associated with VAP. The mortality in VAP (58.1%) contrasted with non-VAP (40%). 99/169 (58.6%) Gram-negative isolates were resistant to carbapenems. Acinetobacter baumannii, Pseudomonas aeruginosa and Klebsiella pneumoniae were common pathogens found in late onset VAP, whereas K. pneumoniae, A. baumannii and Staphylococcus aureus were common in early onset VAP. The PCR results detected blaNDM in 37/172(21.5%) and blaVIM in 30/172(17.4%); 15/172(8.7%) isolates carried both genes.

CONCLUSION

The blaNDM-1 and blaVIM genes are the main antibiotic-resistance genes that induce resistance patterns to carbapenems in VAP, highlighting CRE strains of potential public health concern and therapeutic challenge. Diagnostic laboratories in India must get on high caution for early MBL detection as it may limit the wide dispersal of MBL genes.

A Subgroup of Patients With Hospital-acquired Pneumonia Do Not Require Broad-spectrum Gram-negative Antimicrobial Coverage

Among 200 patients developing hospital-acquired pneumonia (HAP) outside the intensive care unit, 61% were treated empirically without broad-spectrum Gram-negative coverage, with clinical cure in 69.7%. Lower disease severity markers (systemic inflammatory response syndrome, hypoxia, tachypnoea, neutrophilia) and the absence of diabetes mellitus and prior doxycycline treatment (but not the time to HAP onset) identified patients not requiring broad-spectrum Gram-negative coverage.

Multiresistant Bacterial Pathogens Causing Bacterial Pneumonia and Analyses of Potential Risk Factors from Northeast Ethiopia

BACKGROUND

Pneumonia is the most common cause of morbidity and mortality in developing countries, mostly caused by different species of bacterial pathogens. Hence, patient management needs awareness of the pathogens and antimicrobial susceptibility testing (AST). This study was aimed to assess the type of bacterial isolates and their antimicrobial susceptibility patterns among pneumonia suspected patients at Dessie Referral Hospital, Northeast Ethiopia. Potential risk factors were also assessed to apply preventive measures accordingly.

MATERIALS AND METHODS

A cross-sectional study design was employed among pneumonia suspected patients from February to April 2020 at Dessie Referral Hospital. Sociodemographic characteristics and associated risk factors were collected using a pretested questionnaire, and clinical data were extracted by reviewing medical records. Sputum specimens were collected and inoculated into chocolate agar, blood agar, mannitol salt agar, and MacConkey agar which are then incubated at 35°C or 37°C for 24-48 hours. Bacterial species were identified based on Gram stain, colony characteristics, and biochemical techniques. The data were entered in to Epi-Info version 7.1.5 and analyzed with SPSS software version 20. p value <0.05 at 95% CI was considered as statistically significant.

RESULTS

A total of 406 sputum specimens were collected and cultured, among which 157 (38.7%) were positive for different bacterial pathogens. The predominant pathogens were Klebsiella pneumoniae (28.0%), Streptococcus pneumoniae (24.8%), Staphylococcus aureus (18.5%), and Pseudomonas aeruginosa (14.0%). Majority of the isolates exhibited resistance to ampicillin with 81.5% followed by penicillin with 75.9% and amoxicillin-clavulanate with 61.2%. Multivariable logistic regression showed a significant association of culture positivity with older age (AOR = 2.43, CI: 1.12-5.28, p value = 0.025), cigarette smoking (AOR = 4.67, CI: 2.39-9.20, p value <0.001), and alcohol use (AOR = 5.58, CI: 3.14-9.92, p value <0.001). Resistance to ampicillin and penicillin was associated with repeated prescription and use.

CONCLUSIONS

This study found high prevalence of bacterial pneumonia in the study area, and high rate of bacterial resistance was observed in ampicillin, penicillin, and amoxicillin-clavulanate. Repeated prescriptions and use of antimicrobials were significantly independent factors of bacterial resistance. Therefore, patient management needs identification of bacteria by routine culture with antimicrobial susceptibility testing.

Trimethoprim-sulfamethoxazole as de-escalation in ventilator-associated pneumonia: a cohort study subanalysis

Purpose

This is a subanalysis of a previous study which compared the effectiveness of trimetoprim-sulfametoxazole (TMP-SMX) with all other regimens for treatment of ventilator-associated pneumonia (VAP). Aim of the current study was to focus on the effectiveness of a strategy based on TMP-SMX as de-escalation from β-lactam including regimens.

Methods

Retrospective cohort study including patients who were hospitalized for VAP from 2011 to 2019. Patients were distributed in two groups: NO SWITCH TO TMP-SMX group, including patients who received β-lactams for all treatment duration, and SWITCH TO TMP-SMX group, which included patients who switched to TMP-SMX from a β-lactam including regimen after microbiology diagnosis. Three clinical outcomes were analyzed: mortality at 30 days from the start of the antibiotic treatment (T30), mortality at the end of treatment (EoT), and acquisition of multidrug-resistant bacteria during hospitalization in intensive care unit.

Results

Overall, 70 patients were included in the current study, 32/70 (45.7%) in NO SWITCH TO TMP-SMX group and 38/70 (54.3%) in SWITCH TO TMP-SMX group, 37/70 (52.8%) had been already included in the previous study. No significant differences in clinical outcomes and patient’s characteristics were found when the two groups were compared.

Conclusions

De-escalation to TMP-SMX for VAP treatment was not associated with higher mortality at EoT and T30 than standard treatment with β-lactam. Monotherapy with TMP-SMX as de-escalation from broad-spectrum empirical regimens is a β-lactam sparing strategy worthy to be further investigated in either multicenter cohort studies or randomized clinical trials.

Microbiology of Ventilator-associated Pneumonia in a Tertiary Care Cancer Hospital

Background

Ventilator-associated pneumonia (VAP) is an important cause of healthcare-associated infections, resulting in prolonged hospitalization with increased morbidity and mortality. Knowledge of predominant local pathogens and their antimicrobial susceptibility patterns helps in selection of appropriate initial antibiotic therapy in these critical cases.

Aim and objective

The aim and objective of this study is to characterize the microbiology and antimicrobial susceptibility patterns of VAP isolates in a tertiary cancer center.

Materials and methods

This is a 4-year qualitative observational study carried out at a tertiary care cancer hospital in Mumbai. All nondirect bronchoalveolar lavage specimens from patients with a clinical suspicion of VAP sent from the critical care unit to the department of microbiology were processed as per standard laboratory procedures. All isolates were identified to species level and an antimicrobial susceptibility testing was performed by the Kirby–Bauer disk diffusion method and/or the VITEK 2 automated identification and susceptibility system, according to Clinical and Laboratory Standards Institute guidelines.

Results

The study comprised 1,074 patients: 710 (66.10%) men and 364 (33.90%) women. A total of 827 bacterial isolates were obtained with 780 (94.32%) gram-negative organisms and 47 (5.68%) gram-positive organisms; of which Acinetobacter baumannii (38.7%), Pseudomonas aeruginosa (17.5%), and Klebsiella pneumoniae (16.6%) were the commonest. Of gram-negative bacilli, multidrug-resistant organisms constituted 87.50% and were susceptible to colistin.

Conclusions

VAP is associated with pathogens, such as A. baumannii, P. aeruginosa, and K. pneumoniae in our setting. High rates of resistance to aminoglycosides, β-lactam-β-lactamase inhibitor combinations, and carbapenems were noted.

How to cite this article

Sangale A, Bhat V, Kelkar R, Biswas S. Microbiology of Ventilator-associated Pneumonia in a Tertiary Care Cancer Hospital. Indian J Crit Care Med 2021;25(4):421–428.

Update of the treatment of nosocomial pneumonia in the ICU

In accordance with the recommendations of, amongst others, the Surviving Sepsis Campaign and the recently published European treatment guidelines for hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP), in the event of a patient with such infections, empirical antibiotic treatment must be appropriate and administered as early as possible. The aim of this manuscript is to update treatment protocols by reviewing recently published studies on the treatment of nosocomial pneumonia in the critically ill patients that require invasive respiratory support and patients with HAP from hospital wards that require invasive mechanical ventilation. An interdisciplinary group of experts, comprising specialists in anaesthesia and resuscitation and in intensive care medicine, updated the epidemiology and antimicrobial resistance and established clinical management priorities based on patients' risk factors. Implementation of rapid diagnostic microbiological techniques available and the new antibiotics recently added to the therapeutic arsenal has been reviewed and updated. After analysis of the categories outlined, some recommendations were suggested, and an algorithm to update empirical and targeted treatment in critically ill patients has also been designed. These aspects are key to improve VAP outcomes because of the severity of patients and possible acquisition of multidrug-resistant organisms (MDROs).

An overview of ceftolozane sulfate + tazobactam for treating hospital acquired pneumonia

INTRODUCTION

Ceftolozane-tazobactam is a combination of a new cephalosporin, with activity similar to that of ceftazidime, and a known inhibitor of beta-lactamases. This compound shows excellent activity against most gram-negative organisms causative of hospital-acquired pneumonia (HAP) or ventilator-acquired pneumonia (VAP), including extended spectrum beta-lactamase (ESBL)-producing Enterobacterales and multidrug-resistant (MDR) Pseudomonas aeruginosa.

AREAS COVERED

This article reviews the spectrum of activity, the main pharmacokinetic and pharmacodynamic characteristics and the clinical efficacy and safety of ceftolozane-tazobactam in the treatment of HAP/VAP in adult patients.

EXPERT OPINION

The results of a randomized clinical trial have demonstrated an efficacy and safety profile of ceftolozane-tazobactam similar to that of its comparator for the treatment of patients with HAP/VAP. Several retrospective studies have shown good efficacy of the drug for the treatment of respiratory infections caused by MDR P. aeruginosa. The use of this drug may be incorporated as a new therapeutic option for the treatment of patients with HAP/VAP in a carbapenem-saving setting or as a therapeutic alternative with a better safety profile than other therapeutic options in patients with infections caused by MDR P. aeruginosa.

A live auxotrophic vaccine confers mucosal immunity and protection against lethal pneumonia caused by Pseudomonas aeruginosa

Pseudomonas aeruginosa is one of the leading causes of nosocomial pneumonia and its associated mortality. Moreover, extensively drug-resistant high-risk clones are globally widespread, presenting a major challenge to the healthcare systems. Despite this, no vaccine is available against this high-concerning pathogen. Here we tested immunogenicity and protective efficacy of an experimental live vaccine against P. aeruginosa pneumonia, consisting of an auxotrophic strain which lacks the key enzyme involved in D-glutamate biosynthesis, a structural component of the bacterial cell wall. As the amounts of free D-glutamate in vivo are trace substances in most cases, blockage of the cell wall synthesis occurs, compromising the growth of this strain, but not its immunogenic properties. Indeed, when delivered intranasally, this vaccine stimulated production of systemic and mucosal antibodies, induced effector memory, central memory and IL-17A-producing CD4⁺ T cells, and recruited neutrophils and mononuclear phagocytes into the airway mucosa. A significant improvement in mice survival after lung infection caused by ExoU-producing PAO1 and PA14 strains was observed. Nearly one third of the mice infected with the XDR high-risk clone ST235 were also protected. These findings highlight the potential of this vaccine for the control of acute pneumonia caused by this bacterial pathogen.

Pseudomonas aeruginosa is an opportunistic bacterium and one of the most common causes of healthcare-associated diseases, including acute pneumonia, causing high mortality within immunocompromised hosts. Most of these infections are strikingly difficult to treat using conventional antibiotic therapies, since this microorganism displays high intrinsic resistance to a wide range of antibiotics. Moreover, to date, no vaccine is available for prevention. Here we used a mutated bacterial strain, which is unable to replicate in vivo and to cause disease, as a live vaccine against acute pneumonia caused by this pathogen. When applied intranasally, this vaccine induced immunity both at local and distant body sites, activating immune cells which were recruited into the airway mucosa. This evoked immune response reduced the number of non-surviving mice after infection with two cytotoxic P. aeruginosa strains causing acute lung infection. Some protection was also observed against an internationally disseminated cytotoxic strain. These data indicate that this is a promising vaccine candidate against P. aeruginosa-pneumonia.

MexAB-OprM Efflux Pump of Pseudomonas aeruginosa Offers Resistance to Carvacrol: A Herbal Antimicrobial Agent

Carvacrol is a herbal antimicrobial agent with in vitro activity against several bacterial pathogens. However, multidrug resistant strains of Pseudomonas aeruginosa are resistant to herbal antimicrobial compounds including carvacrol. Resistance of P. aeruginosa to carvacrol is not well studied. This study was aimed to identify the gene(s) associated with carvacrol resistance, thus to understand its mechanisms in P. aeruginosa. A herbal drug resistant strain was isolated from a hospital environment. Carvacrol sensitive mutant was generated using transposon mutagenesis. The inactivated gene in the mutant was identified as mexA, which is part of the mexAB-oprM operon. Inactivation of the mexA gene resulted in a >31-fold reduction in MIC of carvacrol, whereas a >80-fold reduction was observed in the presence of drug efflux inhibitor phenylalanine-arginine β-naphthylamide (PAβN). The parental herbal-resistant strain was completely killed within 3 h of incubation in the presence of carvacrol and PAβN. The mexA inactivation did not affect the resistance to other herbal compounds used. The results demonstrate that resistance to carvacrol in P. aeruginosa is mediated by the MexAB-OprM efflux pump.

Rational approach in the management of Pseudomonas aeruginosa infections

PURPOSE OF REVIEW

This review details the management of Pseudomonas aeruginosa infections covering both current and future treatment options that are and may be available for the clinicians.

RECENT FINDINGS

Pseudomonas aeruginosa infections are a great concern in hospital-acquired infections with very limited therapeutic options. The increasing antibiotic resistance has led to a need for different treatment choices that range from the use of new antibiotics to new nonantibiotic alternative agents to kill or disarm the pathogen.

SUMMARY

New molecules such as ceftolozane-tazobactam, ceftazidime-avibactam, and imipenem-relebactam have shown an adequate activity against P. aeruginosa, especially against multidrug resistance strains. Other nonantibiotic alternative treatments, such as antibodies, bacteriocins or phage therapy, have shown promising results, but future clinical studies are needed.

Microbial cause of ICU-acquired pneumonia: hospital-acquired pneumonia versus ventilator-associated pneumonia

PURPOSE OF REVIEW

Successful treatment of patients with hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP) remains a difficult and complex undertaking. Better knowledge of the pathogens involved in that setting may allow reassessment of our current modalities of therapy and definition of better protocols.

RECENT FINDINGS

Microorganisms responsible for HAP/VAP differ according to geographic areas, ICU patients' specific characteristics, durations of hospital and ICU stays before onset of the disease, and risk factors for MDR pathogens. However, a number of studies have shown that Gram-negative bacilli (GNB) - particularly Pseudomonas aeruginosa and Enterobacteriaceae - cause many of the respiratory infections in this setting, with minimal differences between HAP and VAP, indicating that the cause depends more on the underlying clinical condition of patients rather than previous intubation.

SUMMARY

When selecting initial antimicrobial therapy in patients with HAP/VAP, more attention should be paid to individual risk factors for MDR pathogens, severity of the clinical situation, and the local epidemiology than to the type of pneumonia.

Trimetoprim-sulfametoxazole in ventilator-associated pneumonia: a cohort study

To evaluate the effectiveness of trimetoprim-sulfametoxazole (TMP-SMX) for treatment of ventilator-associated pneumonia (VAP). A retrospective cohort study including patients with VAP from 2011 to 2017. Two groups were analysed: TMP-SMX group, including patients who had received TMP-SMX (as first-line and as de-escalation), and No-TMP-SMX group, including patients who had not received TMP-SMX treatment. Primary clinical outcome was mortality at 30 days from starting the antibiotic treatment (T30). Secondary outcomes were mortality at end of treatment (EoT), day survival at T30, and acquisition of multidrug-resistant bacteria during hospitalization in intensive care unit. Eighty cases of VAP were included and devised into two groups: No-TMP-SMX (31/80; 39%) and TMP-SMX (49/80; 61%). Univariate analysis showed no significant differences were found when the TMP-SMX group was compared with the No-TMP-SMX group, except for frequency of male gender (p = 0.025). No significant statistical correlations between mortality at T30 and individual factors were detected by the multivariate model. No cases of either severe allergy or Clostridium difficile disease were reported in the TMP-SMX and No-TMP-SMX groups. TMP-SMX treatment was not associated with higher mortality at EoT and T30 in comparison with the No-TMP-SMX group. TMP-SMX had a good safety profile, in terms of ecology (acquisition of MDR bacteria and Clostridium difficile disease) and clinical management (no allergy events).

Chemical pharmacotherapy for hospital-acquired pneumonia in the elderly

INTRODUCTION

Hospital-acquired pneumonia (HAP) is a potentially serious infection that primarily affects older patients. The number of patients affected by multidrug-resistant (MDR) bacteria is increasing, including infection from strains of Staphylococcus aureus, Enterobacteriaceae, and Pseudomonas aeruginosa.

AREAS COVERED

This article focuses specifically on HAP, excluding patients afflicted by ventilator-associated pneumonia (VAP). The pathogenesis and clinical features of HAP in the elderly are discussed as well as specific drug pharmacokinetic and pharmacodynamic considerations in elderly patients. The current recommended guidelines for the management of HAP are also discussed. Finally, the authors provide evidence on the empirical therapy used for the treatment of HAP and widely consider specific-pathogen treatment of HAP in elderly patients.

EXPERT OPINION

In patients not at risk of MDR organism infection, antibiotics including piperacillin-tazobactam, cefepime, carbapenems or fluorquinolones are recommended. However, the emergence of MDR organisms as causal agents of HAP makes it necessary to accurately assess risk factors to these pathogens and revise our knowledge on specific antimicrobial susceptibility patterns from each institution. The authors believe that broader-spectrum empiric antibiotic therapies that target P. aeruginosa and methicillin-resistant S. aureus are best recommended in elderly patients at risk of HAP infection by MDR strains.

A prognostic score for the resolution of bacteremia by Gram-negative bacteria resistant to carbapenems

The management of bacteremia by carbapenem-resistant Gram-negative bacteria (CRGNB) necessitates a surrogate marker for response to treatment. We developed a prognostic score of bacteremia resolution using a test and a validation cohort. In the test cohort, five protein biomarkers were measured in serial daily serum samples from 39 patients with ventilator-associated pneumonia (VAP) and CRGNB bacteremia. Receiver operator characteristic curves were designed to identify cut-off of over-time changes that were associated with more than 80% specificity for resolution of bacteremia. The developed score was validated in a cohort of 24 patients mostly with primary bacteremia by carbapenem-resistant enterobacteria (CRE). Among the five tested biomarkers, only procalcitonin (PCT) was associated with resolution of bacteremia. More precisely, resolved bacteremia was considered if at least one of three situations occurred: (a) PCT on day 2 was decreased more than 30% and PCT on day 4 was below 0.5 ng/ml; (b) PCT on day 4 was decreased more than 40% and PCT on day 4 was below 0.5 ng/ml; and (c) PCT on day 2 was decreased more than 30% and PCT on day 4 was decreased more than 40%. Sensitivity, specificity, and positive and negative predictive values of the score were 66.7%, 83.3%, 90.0%, and 52.6% respectively. This score was fully validated (p values of comparison between the cohorts 0.623). The developed score is highly predictive of resolution of bacteremia by CRGNB. A prospective clinical study is mandatory to validate the results.

Expression and Significance of Th17 and Treg Cells in Pulmonary Infections with Gram-Negative Bacteria

The aim of this study was to investigate the expression and significance of T helper type 17 (Th17) and regulatory T (Treg) cells in severe pulmonary infection with gram-negative bacteria (GNB). The peripheral venous blood (PVB) and bronchoalveolar lavage fluid (BALF) were collected from patients receiving mechanical ventilation in the intensive care unit (ICU) owing to: (1) pulmonary GNB infection (group I) and (2) nonpulmonary infection (group NI). Patients from the two groups were matched based on their Acute Physiology and Chronic Health Evaluation II (APACHE II) scores and were recruited in the same period. The levels of Th17 and Treg cells in the PVB and BALF were measured by flow cytometry. (1) The levels of Th17 and Treg cells in the PVB and BALF of the infection group (I) were significantly higher than those of the noninfection group (NI) (p < 0.01), and the levels decreased significantly after treatment (p < 0.01). (2) The Treg/Th17 cell ratio in the PVB and BALF of group I was significantly lower than those of group NI and after treatment (p < 0.01). (3) The levels of Th17 and Treg cells in the PVB and BALF could not predict the 28-day mortality (p > 0.05). The expression of Th17 and Treg cells was abnormal in patients with severe pulmonary GNB infection. Our data suggest an overactive immune response in the early stages of inflammation, but the levels of Treg and Th17 cells failed to predict the 28-day mortality.

Using ROS as a Second Messenger, NADPH Oxidase 2 Mediates Macrophage Senescence via Interaction with NF-κB during Pseudomonas aeruginosa Infection

Pseudomonas aeruginosa (PA) is one of the most prevalent pathogens that cause nosocomial infection in critical patients. However, the mechanisms underlying macrophage growth status and functional changes during PA infection are yet unknown. In the present study, NADPH oxidase, gp91^phox (NOX2) mediated macrophage to senescence in a PAO1 colony-dependent manner. gp91^phox might regulate the senescence process through mutual interaction with the NF-κB pathway. During infection, the overexpression or downregulation of gp91^phox in macrophage could affect the nuclear activity of NF-κB p65, while the downregulation of NF-κB p65 led to a suppressed expression of gp91^phox. Reactive oxygen species (ROS) served as the second messenger between both molecules as the ROS inhibitor, N-acetylcysteine (NAC), could partially restore these changes. Consequently, the level of ROS and inflammatory cytokines, including IL-6 and TNFα, elevated during PAO1 infection, and their production altered as a result of the genetic manipulation of gp91^phox and NF-κB p65, as well as NAC treatment. Also, the senescent phenotypes, SA-β-gal staining and p16^ink4a, changed after genetic manipulation with gp91^phox and NF-κB p65 and NAC treatment. The capacity of phagocytosis in macrophages was decreased during senescence. In conclusion, PA directs the macrophage towards senescence, and senescent macrophages exhibit a decreased ability of phagocytosis. This process of senescence was regulated by the interactions between NADPH oxidase gp91^phox and NF-κB p65 via ROS as a second messenger.

Nosocomial pneumonia: Search for an empiric and effective antibiotic regimen in high burden tertiary care centre

The clinical practice guidelines on nosocomial pneumonia recommends an empirical regimen that would work in 95% of the patients based on the local antibiogram. The aim of the study was development of an antibiogram for guiding empiric therapy in settings with high prevalence of multi-drug resistant organisms. A retrospective review of electronic health records (e-hospital portal) was done to analyze all respiratory isolates from patients admitted in medical wards and intensive care unit between May 2016 and May 2017. The samples included brocho-alveolar lavage (BAL), mini broncho-alveolar lavage (mini-BAL) and endotracheal aspirate. The sensitivity pattern (combined and individual) of all bacterial isolates were analysed for commonly used antibiotics and their combinations. Out of the 269 isolates, the most common organisms were Pseudomonas aeruginosa (125, 46%), Acinetobacter baumanni (74, 27%) and Klebsiella pneumoniae (50, 19%). Cefoperazone-sulbactam (43%) had the best sensitivity pattern overall. Cefoperazone-sulbactam plus amikacin (56%) was the combination with the best combined sensitivity overall. There is a high prevalence of resistance in the commonly implicated organisms to the available antibiotics. There is an urgent need for implementation of effective anti-microbial stewardship programmes and development of newer antimicrobials.

Healthcare-Associated Pneumonia and Hospital-Acquired Pneumonia: Bacterial Aetiology, Antibiotic Resistance and Treatment Outcomes: A Study From North India

BACKGROUND

Data regarding the comparative profiling of HCAP and HAP from developing countries like India are scant. We set out to address the microbial aetiology, antibiotic resistance and treatment outcomes in patients with HCAP and HAP.

METHODS

318 consenting patients with HCAP (n = 165, aged 16-90 years; median 60 years; 97 males) or HAP (n = 153; aged 16-85 years; median 45 years; 92 males) presenting to a tertiary care hospital in North India from 2013 to 2015 were prospectively recruited for the study. Data on patient characteristics, microbial aetiology, APACHE II scores, treatment outcomes and mortality were studied. Clinical outcomes were compared with various possible predictors employing logistic regression analysis.

RESULTS

Patients in HCAP had more comorbidity. Escherichia coli (30, 18%) and Acinetobacter baumannii (62, 41%) were the most commonly isolated bacteria in HCAP and HAP, respectively. Multidrug-resistant bacteria were isolated more frequently in HCAP, only because the incidence of extensively drug-resistant bacteria was markedly high in HAP (p = 0.00). The mean APACHE II score was lower in HCAP (17.55 ± 6.406, range 30) compared to HAP (19.74 ± 8.843, range 37; p = 0.013). The length of stay ≥ 5 days (p = 0.036) and in-hospital mortality was higher in HAP group (p = 0.002). The most reliable predictors of in-hospital mortality in HCAP and HAP were APACHE II score ≥ 17 (OR = 14, p = 0.00; HAP: OR = 10.8, p = 0.00), and septic shock (OR = 4.5, p = 0.00; HAP: OR = 6.9, p = 0.00).

CONCLUSION

The patient characteristics in HCAP, treatment outcomes, bacterial aetiology, and a higher incidence of antibiotic-resistant bacteria, suggest that HCAP although not as severe as HAP, can be grouped as a separate third entity.

Incidence and potential risk factors for hospital-acquired pneumonia in an emergency department of surgery

Objective

Hospital-acquired pneumonia (HAP) is associated with high mortality and is the second most common nosocomial infection. The aim of this study was to calculate the incidence and to identify potential risk factors for HAP in an emergency ward for surgical patients admitted because of acute abdomen or trauma.

Design

A structured review of medical records was conducted. Patients diagnosed with pneumonia >48 h after admittance, were compared with a randomly chosen age-matched reference group. Ten variables judged as potential risk factors for HAP were studied in 90 patients.

Setting

An emergency ward for surgical patients with acute abdomen or trauma at an Univerity hospital in Sweden.

Participants

A total of 90 patients with HAP and 120 age-matched controls were included.

Main Outcome Measures

Risk factors for HAP in patients at a surgical clinic.

Results

Of a total of 10 335 admitted patients, during 4.5 years the hospital stay was longer than 48 h in 4961 patients. Of these 90 (1.8%) fulfilled the strict criteria for HAP. Potential risk factors were suspected or verified aspiration (odds ratio (OR): 23.9) that was 2-fold higher than immobilization (OR: 11.2). Further, chronic pulmonary obstructive disease (COPD)/asthma, abdominal surgery and gastric retention/vomiting were risk factors for HAP.

Conclusion

Verified or suspected aspiration was the dominating risk factor for HAP but also immobilization was frequently associated with HAP. Various established preventive measures should be implemented in the nursing care to reduce the frequency of HAP.

Pseudomonas aeruginosa-associated Diarrheal Diseases in Children

BACKGROUND

The gastrointestinal tract is not the common infection site of Pseudomonas aeruginosa. The role of P. aeruginosa as a causative agent for diarrhea in children without preexisting disease is controversial.

METHODS

From 2003 to 2012, we reviewed the records of 259 diarrheal patients less than 5 years of age whose stool culture grew P. aeruginosa. Virulence phenotypes of bacterial isolates were determined in vitro, including cytotoxicity, penetration and adherence to epithelial cells.

RESULTS

The presence of P. aeruginosa in children with diarrhea less than 5 years old is 0.91%. P. aeruginosa-associated diarrheal diseases were classified into 4 groups: Shanghai fever (enteric infection and sepsis) (5%), P. aeruginosa enterocolitis (15%), P. aeruginosa-related diarrhea (19%) and antibiotic-associated diarrhea (43%). The remaining patients had coinfection with other pathogens (18%). Shanghai fever was the most severe enteric disease with invasive infection and complications. The clinical features of P. aeruginosa enterocolitis were prolonged fever with bloody or mucoid diarrhea mimicking bacterial enterocolitis. The clinical features of P. aeruginosa-related diarrhea and antibiotic-associated diarrhea were similar to viral or toxin-mediated diarrhea. Compared with other P. aeruginosa-associated diarrheal diseases, patients with Shanghai fever were younger, usually infants, and the characteristic laboratory findings included leukopenia, thrombocytopenia, high C-reactive protein, hyponatremia and hyperglycemia. Except for Shanghai fever, antibiotic treatment is not recommended. Isolates from Shanghai fever were more cytotoxic and adherent than isolates from uncomplicated diarrheal patients.

CONCLUSIONS

P. aeruginosa could be an enteric pathogen even in healthy children. Young age and highly virulent bacterial strains were risk factors for Shanghai fever.

Antibiotic resistance & pathogen profile in ventilator-associated pneumonia in a tertiary care hospital in India

Background & objectives:

Ventilator-associated pneumonia (VAP) is an important hospital-acquired infection with substantial mortality. Only a few studies are available from India addressing the microbiological aspects of VAP, which have been done with small study populations. This study was carried out in the intensive care units (ICUs) of a tertiary care hospital to assess the profile of pathogens and to determine the pattern of antimicrobial resistance.

Methods:

This was a retrospective study of clinically suspected cases of VAP. Over a three year period, a total of 247 cases in 2011, 297 in 2012 and 303 in 2013 admitted in ICUs on mechanical ventilation with clinical evidence of VAP were included in our study. The endotracheal aspirate samples from these suspected cases were subjected to quantitative culture technique, and colony count of ≥10⁵ colony forming units/ml was considered significant. Antimicrobial susceptibility test for the isolates was done.

Results:

VAP rates of 44.1, 43.8 and 26.3 were seen in 2011, 2012 and 2013, respectively. In all the three years, non-fermentative Gram-negative bacilli were the predominant organisms, followed by Pseudomonas spp. and Klebsiella spp. Staphylococcus aureus exhibited a downwards trend in prevalence from 50.0 per cent in 2011 to 34.9 per cent in 2013. An increase in vancomycin-resistant enterococci was seen from 4.3 per cent in 2012 to 8.3 per cent in 2013, while methicillin resistance amongst the S. aureus crossed the 50 per cent mark in 2013. An increasing trend in resistance was shown by Pseudomonas spp. for piperacillin-tazobactam (PTZ), amikacin and imipenem (IPM). For the non-fermenters, resistance frequency remained very high except for IPM (33.1%) and polymyxin-B (2.4%).

Interpretation & conclusions:

Our findings show VAP as an important problem in the ICU setting. The incidence of multidrug-resistant pathogens was on the rise. The resistance pattern of these pathogens can help an institution to formulate effective antimicrobial policy. To have a comprehensive pan-India picture, multicentric studies are needed.

Comparison of the BD MAX MRSA XT to the Cepheid™ Xpert® MRSA assay for the molecular detection of methicillin-resistant Staphylococcus aureus from nasal swabs

INTRODUCTION

Variation in MRSA genotypes may affect the sensitivity of molecular assays to detect this organism.

METHODS

We compared 2 commonly used screening assays, the Cepheid™ Xpert® MRSA and the BD MAX™ MRSA XT on consecutively obtained nasal swabs from 479 subjects. Specimens giving discordant results were subjected to additional microbiologic and molecular testing.

RESULTS

Six hundred forty-two (97.6%) of the 658 test results were concordant. Of the 16 discordant results from 12 subjects, additional results suggested that 9 (60%) of the 15 MRSA XT assays were likely correct, and 6 (40%) of the 15 Xpert® assays were likely correct. One discordant result could not be resolved. A mecA dropout and novel mec right-extremity junction (MREJ) sites led to false-positive and negative results by Xpert®.

CONCLUSION

While both assays performed well, continued vigilance is needed to monitor for Staphylococcus aureus with novel MREJ sites, mecA dropouts, and mecC, leading to inaccurate results in screening assays.

SIRT1‑mediated regulation of oxidative stress induced by Pseudomonas aeruginosa lipopolysaccharides in human alveolar epithelial cells

Sirtuin1 (SIRT1) is an NAD+‑dependent deacetylase that exhibits multiple biological functions, including cell differentiation inhibition, transcription regulation, cell cycle regulation and anti‑apoptosis. Lipopolysaccharides (LPS) are crucial virulence factors produced by Pseudomonas aeruginosa and serve an important role in adjusting the interactions between the host and the pathogen. However, the effect of SIRT1 in the regulation of LPS‑induced A459 human alveolar epithelial cells (AECs) oxidative stress remains unclear. The cellular reactive oxygen species (ROS) production was examined in A549 cells that were supplemented with LPS. Relative cell signaling pathway proteins were further investigated by western blot analysis. It was identified that LPS downregulated SIRT1 expression, however, upregulated ROS generation, which was associated with the increase of nuclear factor (NF)‑κB and acetyl‑NF‑κB. Activation of SIRT1 by resveratrol significantly reversed the effects of LPS on A549 cells. By contrast, inhibition of SIRT1 by nicotinamide had the opposite effects that enhance cell ROS production. Thus, the results indicated that SIRT1 serves an important role in the regulation of oxidative stress induced by LPS in human AECs.

Fitness Cost of Fluoroquinolone Resistance in Clinical Isolates of Pseudomonas aeruginosa Differs by Type III Secretion Genotype

Fluoroquinolone (FQ) resistance is highly prevalent among clinical strains of Pseudomonas aeruginosa, limiting treatment options. We have reported previously that highly virulent strains containing the exoU gene of the type III secretion system are more likely to be FQ-resistant than strains containing the exoS gene, as well as more likely to acquire resistance-conferring mutations in gyrA/B and parC/E. We hypothesize that FQ-resistance imposes a lower fitness cost on exoU compared to exoS strains, thus allowing for better adaptation to the FQ-rich clinical environment. We created isogenic mutants containing a common FQ-resistance conferring point mutation in parC from three exoU to three exoS clinical isolates and tested fitness in vitro using head-to-head competition assays. The mutation differentially affected fitness in the exoU and exoS strains tested. While the addition of the parC mutation dramatically increased fitness in one of the exoU strains leaving the other two unaffected, all three exoS strains displayed a general decrease in fitness. In addition, we found that exoU strains may be able to compensate for the fitness costs associated with the mutation through better regulation of supercoiling compared to the exoS strains. These results may provide a biological explanation for the observed predominance of the virulent exoU genotype in FQ-resistant clinical subpopulations and represent the first investigation into potential differences in fitness costs of FQ-resistance that are linked to the virulence genotype of P. aeruginosa. Understanding the fitness costs of antibiotic resistance and possibilities of compensation for these costs is essential for the rational development of strategies to combat the problem of antibiotic resistance.

Inhaled Antibiotics for Gram-Negative Respiratory Infections

Gram-negative organisms comprise a large portion of the pathogens responsible for lower respiratory tract infections, especially those that are nosocomially acquired, and the rate of antibiotic resistance among these organisms continues to rise. Systemically administered antibiotics used to treat these infections often have poor penetration into the lung parenchyma and narrow therapeutic windows between efficacy and toxicity. The use of inhaled antibiotics allows for maximization of target site concentrations and optimization of pharmacokinetic/pharmacodynamic indices while minimizing systemic exposure and toxicity. This review is a comprehensive discussion of formulation and drug delivery aspects, in vitro and microbiological considerations, pharmacokinetics, and clinical outcomes with inhaled antibiotics as they apply to disease states other than cystic fibrosis. In reviewing the literature surrounding the use of inhaled antibiotics, we also highlight the complexities related to this route of administration and the shortcomings in the available evidence. The lack of novel anti-Gram-negative antibiotics in the developmental pipeline will encourage the innovative use of our existing agents, and the inhaled route is one that deserves to be further studied and adopted in the clinical arena.

Clinical predictors and microbiology of ventilator-associated pneumonia in the intensive care unit: a retrospective analysis in six Italian hospitals

The purpose of this study was to assess the main clinical predictors and microbiological features of ventilator-associated pneumonia (VAP) in the Intensive Care Unit (ICU) environment. This work is a retrospective analysis over one year from September 2010 to September 2011. Patients' risk factors, causes of admission, comorbidities and respiratory specimens collected in six Italian ICUs were reviewed. Incidence and case fatality rate of VAP were evaluated. After stratification for VAP development, univariate and multivariate analyses were performed to assess the impact of patients' conditions on the onset of this infection. A total of 1,647 ICU patients (pts) were considered. Overall, 115 patients (6.9 %) experienced at least one episode of VAP. The incidence rate for VAP was 5.82/1,000 pts-days, with a case fatality rate of 44.3 %. Multivariate analysis showed that admission for neurological disorders (aIRR 4.12, CI 1.24-13.68, p = 0.02) and emergency referral to ICU from other hospitals (aIRR 2.11, CI 1.03-4.31, p = 0.04) were associated with higher risk of VAP, whereas a tendency to a higher risk of infection was detected for admission due to respiratory disease, cardiac disease, trauma and for having obesity or renal failure. A total of 372 microbiological isolates from respiratory specimens were collected in VAP patients. The most common species were Klebsiella pneumoniae, Acinetobacter baumannii and Pseudomonas aeruginosa, showing high resistance rates to carbapenems. Neurological disorders and emergency referral at the admission into the ICU are significantly associated with the onset of VAP. A high incidence of multi-drug resistant Gram- species was detected in the respiratory specimens.

Clinical metagenomics for the management of hospital- and healthcare-acquired pneumonia

The increasing burden of multidrug-resistant bacteria affects the management of several infections. In order to prescribe adequate antibiotics, clinicians facing severe infections such as hospital-acquired pneumonia (HAP) need to promptly identify the pathogens and know their antibiotic susceptibility profiles (AST), which with conventional microbiology currently requires 24 and 48 h, respectively. Clinical metagenomics, based on whole genome sequencing of clinical samples, could improve the diagnosis of HAP, however, many obstacles remain to be overcome, namely the turn-around time, the quantification of pathogens, the choice of antibiotic resistance determinants (ARDs), the inference of the AST from metagenomic data and the linkage between ARDs and their host. Here, we propose to tackle those issues in a bottom-up, clinically driven approach.

Innate Immune Signaling Activated by MDR Bacteria in the Airway

Health care-associated bacterial pneumonias due to multiple-drug resistant (MDR) pathogens are an important public health problem and are major causes of morbidity and mortality worldwide. In addition to antimicrobial resistance, these organisms have adapted to the milieu of the human airway and have acquired resistance to the innate immune clearance mechanisms that normally prevent pneumonia. Given the limited efficacy of antibiotics, bacterial clearance from the airway requires an effective immune response. Understanding how specific airway pathogens initiate and regulate innate immune signaling, and whether this response is excessive, leading to host-induced pathology may guide future immunomodulatory therapy. We will focus on three of the most important causes of health care-associated pneumonia, Staphylococcus aureus, Pseudomonas aeruginosa, and Klebsiella pneumoniae, and review the mechanisms through which an inappropriate or damaging innate immune response is stimulated, as well as describe how airway pathogens cause persistent infection by evading immune activation.

Current and Future Considerations for the Treatment of Hospital-Acquired Pneumonia

Hospital-acquired pneumonia (HAP) and health-care-associated pneumonia (HCAP) are leading causes of death, morbidity, and resource utilization in hospitalized patients, and are associated with a broad range of Gram-positive and Gram-negative pathogens. Here, we discuss the different definitions of HAP and HCAP, review current guidelines regarding the treatment of these conditions, highlight the shortcomings of current therapeutic options, and discuss new antibiotic treatments. To optimize therapeutic outcomes in patients with HAP/HCAP, initial antimicrobial treatment must be appropriate and should be given as soon as possible; inappropriate or delayed therapy greatly increases morbidity and mortality. Selection of the most appropriate antimicrobial agent depends on the causative pathogen(s); initial broad-spectrum therapy is commonly recommended and should cover all pathogens that may be present. Treatment selection should also take into consideration the following factors: knowledge of underlying local risk factors for antimicrobial resistance, disease staging, and risk factors related to specific pathogens such as Pseudomonas aeruginosa, Acinetobacter spp., and methicillin-resistant Staphylococcus aureus (MRSA). Guidelines consistently emphasize the importance of treating HAP and HCAP with early and appropriate broad-spectrum antibiotics, and recent developments in this field have resulted in the availability of several additional treatment options. Telavancin shows potent activity against Gram-positive bacteria including MRSA and can be administered once daily; it was approved in the USA and European Union for the treatment of HAP after demonstrating non-inferiority to vancomycin. Ceftobiprole medocaril exhibits rapid antimicrobial activity against a broad range of both Gram-positive and Gram-negative pathogens, including MRSA. It was approved for the treatment of HAP (excluding ventilator-associated pneumonia) and community-acquired pneumonia in Europe in 2013. These new treatments may offer effective alternative therapeutic options for the management of HAP.

FUNDING

Basilea Pharmaceutica Ltd., Basel, Switzerland.

Pseudomonas aeruginosa nosocomial pneumonia: impact of pneumonia classification

OBJECTIVE

To describe and compare the mortality associated with nosocomial pneumonia due to Pseudomonas aeruginosa (Pa-NP) according to pneumonia classification (community-onset pneumonia [COP], hospital-acquired pneumonia [(HAP], and ventilator-associated pneumonia [VAP]).

DESIGN

We conducted a retrospective cohort study of adults with Pa-NP. We compared mortality for Pa-NP among patients with COP, HAP, and VAP and used logistic regression to identify risk factors for hospital mortality and inappropriate initial antibiotic therapy (IIAT).

SETTING

Twelve acute care hospitals in 5 countries (United States, 3; France, 2; Germany, 2; Italy, 2; and Spain, 3).

PATIENTS/PARTICIPANTS

A total of 742 patients with Pa-NP.

RESULTS

Hospital mortality was greater for those with VAP (41.9%) and HAP (40.1%) compared with COP (24.5%) (P<.001). In multivariate analyses, independent predictors of hospital mortality differed by pneumonia classification (COP: need for mechanical ventilation and intensive care; HAP: multidrug-resistant isolate; VAP: IIAT, increasing age, increasing Charlson comorbidity score, bacteremia, and use of vasopressors). Presence of multidrug resistance was identified as an independent predictor of IIAT for patients with COP and HAP, whereas recent antibiotic administration was protective in patients with VAP.

CONCLUSIONS

Among patients with Pa-NP, pneumonia classification identified patients with different risks for hospital mortality. Specific risk factors for hospital mortality also differed by pneumonia classification and multidrug resistance appeared to be an important risk factor for IIAT. These findings suggest that pneumonia classification for P. aeruginosa identifies patients with different mortality risks and specific risk factors for outcome and IIAT.