Changing bacteriology of adult community-acquired lung abscess in Taiwan: Klebsiella pneumoniae versus anaerobes

Aetiology of Adult Community-Acquired Lung Abscess in Hong Kong

BACKGROUND AND OBJECTIVE

Knowing the pattern of pathogens in community-acquired lung abscess (CALA) is important in the choice of initial empiric antibiotics. Early studies established the anaerobes as the predominant pathogen, followed by aerobic streptococci and aerobic Gram-negative bacilli. However, recent reports indicated that Klebsiella pneumoniae and aerobic streptococci predominated.

METHODS

We performed a retrospective study on CALA cases from all public hospitals in Hong Kong over a nine-year period. Only cases with uncontaminated specimens sent for bacterial culture were included. Cases caused by mycobacteria and fungi were excluded.

RESULTS

There were 606 eligible subjects-episodes. Mean age of subjects was 57.7 years and male to female ratio was 3.3:1. Two hundred and thirty-two subjects had at least one positive bacterial culture, with a total of 338 pathogens isolated. Anaerobes were the predominant pathogen group with 103 isolates (30.5% of total). This was followed by aerobic streptococci (90, 26.6%), aerobic Gram-negative bacilli (67, 19.8%), and Staphylococcus aureus (56, 16.6%). Isolation of Staphylococcus aureus was closely linked to intravenous drug abuse, while isolation of Klebsiella pneumoniae (28 cases) was related to extrapulmonary abscesses, particularly of the liver. There were 14 cases of Pseudomonas aeruginosa with underlying chronic lung disease and major organ failure being risk factors.

CONCLUSION

Anaerobes and aerobic streptococci appear to be the major pathogens for primary CALA. Secondary lung abscess caused by haematogenous spread is commonly attributable to Staphylococcus aureus or Klebsiella pneumoniae. Choice of empiric antibiotics should take these into consideration together with local patterns of antibiotic resistance.

Heterogeneity in clinical patterns of adult lung abscess patients: an 8-year retrospective study in a tertiary hospital

BACKGROUND

The widespread use of broad-spectrum antibiotics has led to changes in both the microbiological and clinical characteristics of lung abscesses. It is necessary to re-evaluate the bacterial spectrum associated with these infections. As a novel method for pathogen detection, metagenomic next-generation sequencing (mNGS) is increasingly being applied in clinical practice. There is limited research evaluating the use of mNGS in patients with lung abscesses.

METHODS

A retrospective analysis was conducted on patients with lung abscess who were hospitalized between July 2015 and July 2023 at a teaching hospital in China. Patients who underwent both computerized tomography (CT) imaging and conventional pathogen testing were included in the study. The efficacy of pathogen detection using conventional methods was compared with that of mNGS. Additionally, the clinical and radiological features were analyzed to provide a comprehensive understanding of the disease patterns.

RESULTS

A total of 782 patients with lung abscess were included in the study and hematogenous abscess accounting for 7.16% (56/782) of cases. The overall hospital mortality rate was 1.53%. The mean age of the patients with lung abscess was 60 years, with a male predominance (80.2%). A significant proportion of patients had comorbid conditions, including diabetes (29.7%) and cardiovascular disease (18.2%). Lung abscesses were predominantly located in the right lung, and pleural effusion was more commonly observed in the deceased group. The detection rate of pathogen via conventional test was lower at 41.8% (327/782). Among patients with positive mNGS results, only 51.9% had pathogens identified through conventional testing methods. Klebsiella pneumoniae was the most frequently detected pathogen by conventional culture, while mNGS identified was Parvimonas micra. Infections caused solely by anaerobic bacteria or facultative anaerobes were associated with shorter hospital stays. Patient infected with Gram-negative bacilli (GNB) had a higher proportion of liver abscesses (11.8%).

CONCLUSION

Compared to conventional testing methods, mNGS demonstrates superior performance in detecting anaerobic and facultative anaerobic bacteria. The low detection rate of conventional tests may result in an underestimation of the clinical significance of anaerobic bacteria infections. In patients with lung abscess caused by GNB, hematogenous dissemination, liver abscess and diabetes were more commonly observed and these patients tended to have longer hospital stays.

Identification and prioritization of novel therapeutic candidates against glutamate racemase from Klebsiella pneumoniae

BACKGROUND

Klebsiella pneumoniae, a gram-negative bacterium in the Enterobacteriaceae family, is non-motile, encapsulated, and a major cause of nosocomial infections, particularly in intensive care units. The bacterium possesses a thick polysaccharide capsule and fimbriae, which contribute to its virulence, resistance to phagocytosis, and attachment to host cells. The bacterium has developed serious resistance to most antibiotics currently in use.

OBJECTIVE

This study aims to investigate the structural properties of MurI (glutamate racemase) from Klebsiella pneumoniae and to identify potential candidate inhibitors against the protein, which will help in the development of new strategies to combat the infections related to MDR strains of Klebsiella pneumoniae.

METHODS

The 3D structure of the protein was modelled using SWISS-MODEL, which utilizes the homology modelling technique. After refinement, the structure was subjected to virtual high throughput screening on the TACC server using Enamine AC collection. The obtained molecules were then put through various screening parameters to obtain promising lead candidates, and the selected molecules were then subjected to MD simulations. The data obtained from MD simulations was then assessed with the help of different global dynamics analyses. The protein-ligand complexes were also subjected to MM/PBSA-based binding free energy calculation using the g_mmpbsa program.

RESULTS

The screening parameters employed on the molecules obtained via virtual screening from the TACC server revealed that Z1542321346 and Z2356864560 out of four molecules have better potential to act as potential inhibitors for MurI protein. The binding free energy values, which came out to be -27.26±3.06 kcal/mol and -29.53±4.29 kcal/mol for Z1542321346 and Z2356864560 molecules, respectively, favoured these molecules in terms of inhibition potential towards targeted protein.

CONCLUSION

The investigation of MurI via computational approach and the subsequent analysis of potential inhibitors can pave the way for developing new therapeutic strategies to combat the infections and antibiotic resistance of Klebsiella pneumoniae. This study could significantly help the medical fraternity in the treatment of infections caused by this multidrug-resistant pathogen.

Virulence profile of carbapenem-resistant Klebsiella pneumoniae strains by an in vivo model of Galleria mellonella

Klebsiella pneumoniae is a significant healthcare-associated pathogen, notable for its diverse virulence and antibiotic resistance profiles. This study aimed to characterize the genotypic and phenotypic diversity of K. pneumoniae isolates and evaluate their virulence using the Galleria mellonella model. Biomass production, metabolic activity, capsule formation, and siderophore production were assessed in 27 K. pneumoniae isolates from hospital-associated infections. Lethality curves were generated using the G. mellonella model, with survival monitored hourly from 16 to 48 hours. The most common sequence types (ST) identified were the high-risk clones ST307 (N = 10), ST512 (N = 8), ST101 (N = 7), and ST661 (N = 2). These STs were associated with distinct K-locus, including KL102, KL107, KL17, and KL39. Most isolates belonged to the O2afg locus (N = 18), with the K. pneumoniae carbapenemase genotype detected in 96.3% of strains. None of the isolates were classified as hypervirulent. Phenotypically, ST661 exhibited the highest biomass production despite showing similar metabolic activity to other STs. A positive correlation was observed between biomass and siderophore production, while capsule production was inversely correlated with biomass. In the G. mellonella model, ST661 demonstrated the highest virulence, resulting in 100% mortality by 48 hours, compared to survival rates of 21.4% for ST101, 38.0% for ST307, and 31.2% for ST512. These findings underscore the pathogenic potential of ST661 isolates with enhanced biofilm production. The G. mellonella model may serve as an effective in vivo system for evaluating the virulence of emerging K. pneumoniae lineages.IMPORTANCEWe demonstrate that the Galleria mellonella model is a useful tool to analyze the virulence of carbapenem-resistant Klebsiella pneumoniae strains. Our findings highlight the pathogenicity of carbapenem-resistant K pneumoniae isolates, particularly the role of the ST661 that, despite being a rare lineage, harbors the blaVIM gene and is associated with high biofilm production and the highest mortality rates.

A Rare Case of Giant Gangrenous Lung Abscess

Gangrenous lung abscess (LA) is a limited form of lung gangrene. Although its frequency has decreased dramatically in recent years, it occupies an important place in clinical practice. Delaying its diagnosis or incorrect treatment leads to a risk to the patient's life. Timely diagnostics and treatment reduce morbidity and mortality rates. А 68-year-old woman who underwent a right upper bilobectomy for a gangrenous LA is presented. The case is considered in the context of the prolonged therapeutic course and the need for surgical treatment.

Nonalcoholic Fatty Liver Disease Increases the Risk of Lung Abscess: Findings from a Nationwide Cohort Study

Objectives: This study aimed to investigate the association between nonalcoholic fatty liver disease (NAFLD), assessed by the Fatty Liver Index (FLI), and the occurrence of lung abscess within a large population-based cohort. Method: We conducted a nationwide retrospective study using data from 367,930 subjects who underwent National Health check-ups between 2009 and 2018. Cox proportional hazards regression was performed to evaluate the association between the FLI and the incidence of lung abscess and community-acquired pneumonia (CAP) after adjusting for age, sex, and relevant covariates. Results: Among the study population, 455 (0.12%) and 44,934 (12.2%) patients were diagnosed with lung abscesses and CAP, respectively. The cumulative incidence of lung abscess was higher in individuals with elevated FLI values (FLI < 30, 0.10%; 30 ≤ FLI < 60, 0.16%; FLI ≥ 60, 0.18%; p < 0.001), whereas the incidence of CAP decreased across FLI groups (FLI < 30, 12.4%; 30 ≤ FLI < 60, 12.3%; FLI ≥ 60, 11.0%; p < 0.001). After adjusting for covariates, the risk of lung abscess significantly increased in the 30 ≤ FLI < 60 (Hazard ratio (HR) = 1.26; 95% confidence interval (CI), 0.95-1.68; p = 0.115) and the FLI ≥ 60 (HR = 1.67; 95% CI, 1.37-2.29; p < 0.001) groups, although the risk of CAP was relatively small in both groups (30 ≤ FLI < 60; HR = 1.06; 95% CI, 1.03-1.09; p < 0.001) (FLI ≥ 60; HR = 1.13; 95% CI, 1.08-1.12; p < 0.001). Conclusions: Our study provides compelling evidence supporting a potential link between NAFLD, as measured by FLI, and the incidence of lung abscess. These findings suggest the importance of vigilant monitoring of respiratory health in patients with NAFLD and emphasise the need for early detection of possible complications.

Impact of nitric oxide donors on capsule, biofilm and resistance profiles of Klebsiella pneumoniae

Klebsiella pneumoniae is considered to be a critical public health threat due to its ability to cause fatal, multi-drug-resistant infections in the bloodstream and key organs. The polysaccharide-based capsule layer that shields K. pneumoniae from clearance via innate immunity is a prominent virulence factor. K. pneumoniae also forms biofilms on biotic and abiotic surfaces. These biofilms significantly reduce penetration by, and antibacterial activity from, traditional antibiotics. Nitric oxide (NO), an endogenous molecule involved in the innate immune system, is equally effective at eradicating bacteria but without engendering resistance. This study investigated the effects of NO-releasing small molecules capable of diverse release kinetics on the capsule and biofilm formation characteristics of multiple K. pneumoniae strains. The use of NO donors with moderate and extended NO-release properties (i.e., half-life >1.8 h) inhibited bacterial growth. Additionally, treatment with NO decreased capsule mucoviscosity in K. pneumoniae strains that normally exhibit hypermucoviscosity. The NO donors were also effective against K. pneumoniae biofilms at the same minimum biocidal concentrations that eliminated planktonic bacteria, while meropenem showed little antibacterial action in the same experiments. These results represent the first account of exogenous NO affecting biomarkers involved in K. pneumoniae infections, and may therefore inform future development of NO-based therapeutics for treating such infections.

Macrophage-depleted young mice are beneficial in vivo models to assess the translocation of Klebsiella pneumonia from the gastrointestinal tract to the liver in the elderly

Pathobionts are commensal intestinal microbiota capable of causing systemic infections under specific conditions, such as environmental changes or aging. However, it is unclear how pathobionts are recognized by the intestinal mucosal immune system under physiological conditions. This study demonstrates that the gut pathobiont Klebsiella pneumoniae causes injury to the epithelium and translocates to the liver in specific pathogen-free mice treated with clodronate-liposomes that depleted macrophages. In the clodronate-liposome-treated mice, indigenous classical K. pneumoniae (cKp) with non-K1/K2 capsular serotypes were isolated from the liver, indicating that gut commensal cKp translocated from the gastrointestinal tract to the liver due to the depletion of intestinal macrophages. Oral inoculation of isolated cKp to clodronate-liposome-treated mice significantly reduced the survival rates compared to that of non-treated mice. Our findings demonstrate that intestinal mucosal macrophages play a pivotal role in sensing commensal cKp and suppressing their translocation to the liver. This study demonstrates that clodronate-liposome-treated mouse models are effective for screening and evaluating drugs that prevent the translocation of cKp to the liver, providing new insights into the development of preventive protocols against K. pneumoniae infection.

Phage-antibiotic synergy suppresses resistance emergence of Klebsiella pneumoniae by altering the evolutionary fitness

Phage-antibiotic synergy (PAS) represents a superior treatment strategy for pathogen infections with less probability of resistance development. Here, we aim to understand the molecular mechanism by which PAS suppresses resistance in terms of population evolution. A novel hypervirulent Klebsiella pneumoniae (KP) phage H5 was genetically and structurally characterized. The combination of H5 and ceftazidime (CAZ) showed a robust synergistic effect in suppressing resistance emergence. Single-cell Raman analysis showed that the phage-CAZ combination suppressed bacterial metabolic activities, contrasting with the upregulation observed with phage alone. The altered population evolutionary trajectory was found to be responsible for the contrasting metabolic activities under different selective pressures, resulting in pleiotropic effects. A pre-existing wcaJ point mutation (wcaJG949A) was exclusively selected by H5, conferring a fitness advantage and up-regulated activity of carbohydrate metabolism, but also causing a trade-off between phage resistance and collateral sensitivity to CAZ. The wcaJ point mutation was counter-selected by H5-CAZ, inducing various mutations in galU that imposed evolutionary disadvantages with higher fitness costs, and suppressed carbohydrate metabolic activity. H5 and H5-CAZ treatments resulted in opposite effects on the transcriptional activity of the phosphotransferase system and the ascorbate and aldarate metabolism pathway, suggesting potential targets for phage resistance suppression. Our study reveals a novel mechanism of resistance suppression by PAS, highlighting how the complexity of bacterial adaptation to selective pressures drives treatment outcomes.

IMPORTANCE

Phage-antibiotic synergy (PAS) has been recently proposed as a superior strategy for the treatment of multidrug-resistant pathogens to effectively reduce bacterial load and slow down both phage and antibiotic resistance. However, the underlying mechanisms of resistance suppression by PAS have been poorly and rarely been studied. In this study, we tried to understand how PAS suppresses the emergence of resistance using a hypervirulent Klebsiella pneumoniae (KP) strain and a novel phage H5 in combination with ceftazidime (CAZ) as a model. Our study reveals a novel mechanism by which PAS drives altered evolutionary trajectory of bacterial populations, leading to suppressed emergence of resistance. The findings advance our understanding of how PAS suppresses the emergence of resistance, and are imperative for optimizing the efficacy of phage-antibiotic therapy to further improve clinical outcomes.

Inconsistencies in the Indian Guidelines for the Prescription of Antibiotics for Critically Ill Patients

The recently formulated guidelines by Khilnani GC et al. for the prescription of antibiotics for critically ill patients present an extensive compilation of evidence and recommendations. Despite their comprehensive nature, several inconsistencies need addressing. In this commentary, we delve into some of these discrepancies in the order in which they appeared in the guidelines, starting with the misrepresentation of "nonbronchoscopic bronchoalveolar lavage (BAL)" and "mini BAL" as different techniques when they are, in fact, identical. Secondly, the Centers for Disease Control and Prevention (CDC) in the year 2013 replaced the older, unreliable ventilator-associated pneumonia (VAP) definition with ventilator-associated events (VAE). This new VAE definition eliminates subjectivity in pneumonia diagnosis by focusing on objective criteria for ventilator support changes, avoiding dependence on potentially inaccurate chest X-rays and inconsistent medical record keeping. Thus, using the term VAP in the Indian guidelines seems regressive. Furthermore, the recommendation for routine anaerobic coverage in aspiration pneumonia is outdated and unsupported by current evidence. Lastly, while endorsing multiplex polymerase chain reaction (PCR) for pathogen identification, the guidelines fail to adequately address its limitations and the risk of overdiagnosis.

How to cite this article

Raj N, Nath SS, Singh V, Agarwal J. Inconsistencies in the Indian Guidelines for the Prescription of Antibiotics for Critically Ill Patients. Indian J Crit Care Med 2024;28(10):908-911.

Guidelines for Antibiotics Prescription in Critically Ill Patients

How to cite this article: Khilnani GC, Tiwari P, Mittal S, Kulkarni AP, Chaudhry D, Zirpe KG, et al. Guidelines for Antibiotics Prescription in Critically Ill Patients. Indian J Crit Care Med 2024;28(S2):S104-S216.

Molecular detection of Class 1, 2, and 3 integrons in hypervirulent and classic Klebsiella pneumoniae isolates: A cross-sectional study

Background and Aims

The "hypervirulent" variant of Klebsiella pneumoniae (hvKp) is an emerging pathogen that cause life-threatening infection. The present study was conducted to identify the prevalence of hvKp and to investigate the presence class 1, 2, and 3 integrons in these isolates.

Methods

A cross-sectional study was conducted at three teaching hospitals, Ahvaz, South-west of Iran, from January 1, 2019 to December 31, 2020. Samples were collected from inpatients and included only the first samples collected from each patient. K. pneumoniae strains were isolated from different specimens using biochemical test and confirmed by targeting 16S-23S rDNA internal transcribed spacer. HvKp isolates were recovered using string test and were further characterized by detection virulence-associated genes (rmpA, iucA, and magA). Antibiotic susceptibility patterns of isolates were determined using the disc diffusion method. Isolates were screened for presence the integron genes (intI, intII, and intIII) and repetitive element sequence-based polymerase chain reaction (PCR) performed to determine strain relatedness. SPSS version 22 was used for the data analysis.

Results

Seventy-one (77%) of isolates showed multidrug-resistant (MDR) phenotype. HvKP accounted for 14% (13/92) of cKp isolated from blood (46%) and urinary tract infection (38%), and the great majority of them (61.5%; 8/13) exhibited MDR phenotype. Using the PCR assay, 29 of 92 isolates (31.5%) were found to have positive results for the presence of IntI. Three of the IntI-positive strains were hvKP. Class 2 integron was present in 8/92 cKp isolates. Integron Class 2 was found to coexist with Class 1 integron in 3/8 isolates. All integron-positive isolates (IntI and/or IntII) were resistant to at least three different classes of antibiotics and showed MDR phenotype. No Class 3 integrons were detected among the isolates.

Conclusion

The results of our study revealed that considering the role of integrons in facilitating the acquisition and dissemination of resistance genes among bacteria, monitoring the emergence of hvKp, emphasizing on the mechanism of antimicrobial resistance, can prevent from the spread of carbapenemase-producing hvKp strains.

Klebsiella pneumoniae DedA family proteins have redundant roles in divalent cation homeostasis and resistance to phagocytosis

The DedA superfamily is a highly conserved family of membrane proteins. Deletion of Escherichia coli yqjA and yghB, encoding related DedA family proteins, results in sensitivity to elevated temperature, antibiotics, and alkaline pH. The human pathogen Klebsiella pneumoniae possesses genes encoding DedA family proteins with >90% amino acid identity to E. coli YqjA and YghB. We hypothesized that the deletion of K. pneumoniae yqjA and yghB will impact its physiology and may reduce its virulence. The K. pneumoniae ΔyqjA ΔyghB mutant (strain VT101) displayed a growth defect at 42°C and alkaline pH sensitivity, not unlike its E. coli counterpart. However, VT101 retained mostly wild-type resistance to antibiotics. We found VT101 was sensitive to the chelating agent EDTA, the anionic detergent SDS, and agents capable of alkalizing the bacterial cytoplasm such as bicarbonate or chloroquine. We could restore growth at alkaline pH and at elevated temperature by addition of 0.5-2 mM Ca2+ or Mg2+ to the culture media. VT101 displayed a slower uptake of calcium, which was dependent upon calcium channel activity. VT201, with similar deletions as VT101 but derived from a virulent K. pneumoniae strain, was highly susceptible to phagocytosis by alveolar macrophages and displayed a defect in the production of capsule. These findings suggest divalent cation homeostasis and virulence are interlinked by common functions of the DedA family.IMPORTANCEKlebsiella pneumoniae is a dangerous human pathogen. The DedA protein family is found in all bacteria and is a membrane transporter often required for virulence and antibiotic resistance. K. pneumoniae possesses homologs of E. coli YqjA and YghB, with 60% amino acid identity and redundant functions, which we have previously shown to be required for tolerance to biocides and alkaline pH. A K. pneumoniae strain lacking yqjA and yghB was found to be sensitive to alkaline pH, elevated temperature, and EDTA/SDS and displayed a defect in calcium uptake. Sensitivity to these conditions was reversed by addition of calcium or magnesium to the growth medium. Introduction of ΔyqjA and ΔyghB mutations into virulent K. pneumoniae resulted in the loss of capsule, increased phagocytosis by macrophages, and a partial loss of virulence. These results show that targeting the Klebsiella DedA family results in impaired divalent cation transport and, in turn, loss of virulence.

Therapeutical strategies in cavitary legionnaires' disease, two cases from the field and a systematic review

BACKGROUND

Legionnaires' Disease (LD) rarely evolves into pulmonary abscesses. The current systematic review has been designed to explore therapeutical strategies in pulmonary cavitary LD.

METHODS

A research strategy was developed and applied to the databases Embase, Pubmed, and Web of Science from the 1st of January 2000 to the 1st of November 2022. Original articles, case series, case reports, and guidelines written in English, French, German, Italian, and Dutch were considered. Furthermore, medical records of patients treated at the University Hospital UZ Brussel for LD cavitary pneumonia, between the 1st of January 2016 to the 1st of January 2022, were reviewed.

RESULTS

Two patients were found by the UZ Brussel's medical records investigation. Through the literature review, 23 reports describing 29 patients, and seven guidelines were identified. The overall evidence level was low.

RESULT OF SYNTHESIS (CASE REPORTS)

The median age was 48 years and 65% were male. A polymicrobial infection was detected in 11 patients (44%) with other aerobic bacteria being the most commonly found. At diagnosis, 52% of patients received combination therapy, and fluoroquinolones were the preferred antimicrobial class. Anaerobic coverage was neglected in 33% of patients.

RESULT OF SYNTHESIS (GUIDELINES)

Three guidelines favor monotherapy with fluoroquinolones or macrolides, while one suggested an antimicrobial combination in case of severe LD. Four guidelines recommended anaerobic coverage in case of lung abscesses.

CONCLUSION

To date, the evidence supporting cavitary LD treatment is low. Monotherapy lowers toxicity and might be as effective as combination therapy. Finally, anaerobes should not be neglected.

Epidemiology of extended-spectrum β-lactamases in Enterobacterales in Taiwan for over two decades

The emergence of antimicrobial resistance among microorganisms is a serious public health concern, and extended-spectrum β-lactamases (ESBL)-producing Enterobacterales is one of the major concerns among antibiotic-resistant bacteria. Although the prevalence of ESBL in Enterobacterales has been increasing with time, the prevalence of ESBL could differ according to the species, hospital allocation, sources of infections, nosocomial or community acquisitions, and geographic regions. Therefore, we conducted a comprehensive review of the epidemiology of ESBL-producing Enterobacterales in Taiwan. Overall, the rates of ESBL producers are higher in northern regions than in other parts of Taiwan. In addition, the genotypes of ESBL vary according to different Enterobacterales. SHV-type ESBLs (SHV-5 and SHV-12) were the major types of Enterobacter cloacae complex, but Serratia marcescens, Proteus mirabilis, Escherichia coli, and Klebsiella pneumoniae were more likely to possess CTX-M-type ESBLs (CTX-M-3 and CTX-M-14). Moreover, a clonal sequence type of O25b-ST131 has been emerging among urinary or bloodstream E. coli isolates in the community in Taiwan, and this clone was potentially associated with virulence, ESBL (CTX-M-15) production, ciprofloxacin resistance, and mortality. Finally, the evolution of the genetic traits of the ESBL-producing Enterobacterales isolates helps us confirm the interhospital and intrahospital clonal dissemination in several regions of Taiwan. In conclusion, continuous surveillance in the investigation of ESBL production among Enterobacterales is needed to establish its long-term epidemiology.

Liver abscess complicated with multiple organ invasive infection caused by hematogenous disseminated hypervirulent Klebsiella pneumoniae: A case report

Hypervirulent Klebsiella pneumoniae (hvKp) causes increasing infections in healthy individuals from the community. In severe cases, it can cause multiple organ infection with invasive metastasis of blood sources, seriously threatening the patients' life. Rapid and accurate diagnosis of the pathogen becomes the key to timely antibiotic treatment to improve the prognosis. This article reports a case of liver abscess complicated with multiple organ invasive infection caused by hematogenous-disseminated hvKp. K. pneumoniae was identified by culture and metagenomic next-generation sequencing (mNGS) using blood and liver abscess drainage fluid. The isolates from the two samples were subsequently identified with high homology (99.999%) by whole genome sequencing. In addition, multiple virulence genes were detected in the two isolates and the string test was positive, indicating hvKp with hypermucoviscosity phenotype. Multiple antibiotic treatments were given. The conditions of the patient were stable but the temperature remained high. Surgical drainage treatment was performed, and the patient's body temperature immediately dropped to normal. He finally recovered after 6 months of follow-up. mNGS using body fluids can facilitate the rapid diagnosis of pathogens. For hvKp infection, choosing a better antibiotic therapy and receiving surgical drainage can significantly improve the prognosis of the patient.

The making of hypervirulent Klebsiella pneumoniae

Klebsiella pneumoniae is a notorious bacterium in clinical practice. Virulence, carbapenem-resistance and their convergence among K. pneumoniae are extensively discussed in this article. Hypervirulent K. pneumoniae (HvKP) has spread from the Asian Pacific Rim to the world, inducing various invasive infections, such as pyogenic liver abscess, endophthalmitis, and meningitis. Furthermore, HvKP has acquired more and more drug resistance. Among multidrug-resistant HvKP, hypervirulent carbapenem-resistant K. pneumoniae (Hv-CRKP), and carbapenem-resistant hypervirulent K. pneumoniae (CR-HvKP) are both devastating for their extreme drug resistance and virulence. The hypervirulence of HvKP is primarily attributed to hypercapsule, macromolecular exopolysaccharides, or excessive siderophores, although it has many other factors, for example, lipopolysaccharides, fimbriae, and porins. In contrast with classical determination of HvKP, that is, animal lethality test, molecular determination could be an optional and practical method after improvement. HvKP, including Hv-CRKP and CR-HvKP, has been progressing. R-M and CRISPR-Cas systems may play pivotal roles in such evolutions. Hv-CRKP and CR-HvKP, in particular the former, should be of severe concern due to their being more and more prevalent.

Community-Acquired Pneumonia: Postpandemic, Not Post-COVID-19

The coronavirus disease 2019 (COVID-19) pandemic upended our approach to imaging community-acquired pneumonia, and this will alter our diagnostic algorithms for years to come. In light of these changes, it is worthwhile to consider several postpandemic scenarios of community-acquired pneumonia: (1) patient with pneumonia and recent positive COVID-19 testing; (2) patient with air space opacities and history of prior COVID-19 pneumonia (weeks earlier); (3) multifocal pneumonia with negative or unknown COVID-19 status; and (4) lobar or sublobar pneumonia with negative or unknown COVID-19 status. In the setting of positive COVID-19 testing and typical radiologic findings, the diagnosis of COVID-19 pneumonia is generally secure. The diagnosis prompts vigilance for thromboembolic disease acutely and, in severely ill patients, for invasive fungal disease. Persistent or recurrent air space opacities following COVID-19 infection may more often represent organizing pneumonia than secondary infection. When COVID-19 status is unknown or negative, widespread airway-centric disease suggests infection with mycoplasma, Haemophilus influenzae, or several respiratory viruses. Necrotizing pneumonia favors infection with pneumococcus, Staphylococcus, Klebsiella, and anaerobes. Lobar or sublobar pneumonia will continue to suggest the diagnosis of pneumococcus or consideration of other pathogens in the setting of local outbreaks. A positive COVID-19 test accompanied by these imaging patterns may suggest coinfection with one of the above pathogens, or when the prevalence of COVID-19 is very low, a false positive COVID-19 test. Clinicians may still proceed with testing for COVID-19 when radiologic patterns are atypical for COVID-19, dependent on the patient's exposure history and the local epidemiology of the virus.

Nosocomial dissemination of hypervirulent Klebsiella pneumoniae with high-risk clones among children in Shanghai

Objectives

Although hypervirulent Klebsiella pneumoniae (hvKp) is an increasing public health problem, there remains limited epidemiological information regarding hvKp infections in children. Here, we conducted a clinical, molecular and phenotypic surveillance of hvKp strains in a pediatric population.

Methods

Non-repetitive K. pneumoniae (Kp) strains consecutively collected during 2019-2020 were screened for hypervirulence genes (prmpA, prmpA2, iucA, iroB, and peg344) using PCR. Positive strains were further characterized by four phenotypic assays (string test, serum killing assay, siderophore production, Galleria mellonella lethality assay), followed by murine sepsis model to determine virulence in vitro and in vivo. Also, capsular types, sequence types, plasmid replicon types, antimicrobial resistance determinants and susceptibility were analyzed.

Results

A total of 352 isolates were collected, wherein 83 (23.6%) were hypervirulence genes-positive Kp (hgKp). A significant increase in KPC-2-producing KL47-ST11 among hgKp strains was observed, from 5.3% (1/19) in 2019 to 67.6% (25/37) in 2020 (P<.0001), suggesting the potential dissemination of the hybrid virulence and carbapenem-resistance encoding plasmid among children. Further, hgKp isolates were classified into hvKp (n = 27) and hgKp-low virulence (hgKp-Lv) (n = 56) based on virulence phenotypic assays. In hvKp, diverse genetic clones were observed and K1-ST23 or K2-ST25 strains with sensitivity to multiple antibiotics were prevalent (25.9%, 7/27). Compared with hgKp-Lv, hvKp infection had a higher propensity to involve severe pneumonia (22.2% vs. 12.5%) in elder children and significant higher mortality in mice (P = 0.0086). Additionally, either hvKp or hgKp-Lv infections were mostly healthcare-associated and hospital-acquired (74.1% vs. 91.9%).

Conclusions

These data suggest that K1-ST23 and K2-ST25 are high-risk clones of hvKp, and the genetic convergence of virulence and carbapenem-resistance is increasing among children. Control measures are needed to prevent the dissemination in clinical settings.

Pyogenic liver abscess-caused Klebsiella pneumoniae in a tertiary hospital in China in 2017: implication of hypervirulent carbapenem-resistant strains

Background

To investigate the epidemiology of Klebsiella pneumoniae (K. pneumoniae) inducing pyogenic liver abscess (PLA) in east China and the role of hypervirulent carbapenem-resistant K. pneumoniae (Hv-CRKP).

Methods

Forty-three K. pneumoniae strains were collected from 43 patients with PLA at Hangzhou, China in 2017. Antimicrobial susceptibility tests, string test, multilocus sequence typing, pulsed-field gel electrophoresis, mobile genetic elements typing, regular PCR and sequencing, and Galleria mellonella (G. mellonella) lethality test were used to elucidate the epidemiology. Clinical data were collected.

Results

K. pneumoniae strains with serotypes K1 and K2 accounted for 69.8%, which shared 46.5% and 23.3% respectively. K. pneumoniae strains with clonal group 23 were predominant with a rate of 34.9%. Such antimicrobials showed susceptible rates over 80.0%: cefuroxime, cefotaxime, gentamycin, ticarcillin/clavulanate, ceftazidime, cefoperazone/tazobactam, cefepime, aztreonam, imipenem, meropenem, amikacin, tobramycin, ciprofloxacin, levofloxacin, doxycycline, minocycline, tigecycline, chloramphenicol, and trimethoprim-sulfamethoxazole. PFGE dendrogram showed 29 clusters for the 43 K. pneumoniae strains. Three Hv-CRKP strains were confirmed by G. mellonella lethality test, showing a constituent ratio of 7.0% (3/43). Totally three deaths were found, presenting a rate of 7.0% (3/43). The three died patients were all infected with Hv-CRKP.

Conclusions

K1 and K2 are the leading serotypes of K. pneumoniae causing PLA, which show highly divergent genetic backgrounds. Aminoglycosides, Generation 2^nd to 4^th cephalosporins, β-lactamase/β-lactamase inhibitors, carbapenems, fluoroquinolones are empirical choices. Hv-CRKP may confer an urgent challenge in the future.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07648-0.

Management of Pulmonary Hydatidosis and Lung Abscess in Low-Resource Settings

In the modern era, infections of the lung are typically managed medically. However, all pulmonary hydatid cysts require surgery with rare exceptions, and bacterial abscesses require surgery if they are complicated, resistant to treatment, and/or large. Surgical treatment of these pulmonary conditions requires clinical knowledge of tests for causative organisms, perioperative antimicrobial therapies, options for surgical management, and postoperative care.

Diagnostic performance of the metagenomic next-generation sequencing in lung biopsy tissues in patients suspected of having a local pulmonary infection

Purpose

This study aims to evaluate the diagnostic application and performance of the metagenomic next-generation sequencing (mNGS) in patients suspected of local pulmonary infection by comparing it to the traditional pathogen detection methods in lung tissue specimens obtained by a computerized tomography-guided biopsy (CT-guided biopsy).

Methods

We retrospectively reviewed patients, admitted to the First Affiliated Hospital of Wenzhou Medical University, China from May 2018 to December 2020, who were suspected of local pulmonary infection. All cases received a CT-guided lung biopsy, tissue samples were sent both for conventional examinations (CE) and mNGS tests. The sensitivity and specificity of the two diagnostic approaches were compared.

Results

106 patients enrolled, 76 patients were diagnosed with a pulmonary infection. Among 49 patients with identified pathogens, CE confirmed pathogenic infections in 32 cases. Mycobacterium spp. and fungi accounted for 37.5% (12/32) and 28.1% (9/32), respectively, with bacteria 34.4% (11/32). The mNGS examination detected extra pathogenic microorganisms in 22 patients that were consistent with the patients' clinical and radiographic pictures. The sensitivity of mNGS was 53.9% vs. 42.1% for the CE, while the specificity was 56.7% versus 96.7%. For detection rate, mNGS was significantly superior to CE in bacterial (96.3% vs. 40.7%, p < 0.05), and mixed infections (100% vs. 50%, p < 0.05), but inferior to CE in fungal (60% vs. 90%, p > 0.05) and Mycobacterium spp. infections (66.7% vs. 100%, p > 0.05) with no significant difference. Among 31 cases diagnosed with lung abscess, the diagnostic performance of the detection rate was 67.7% (21/31) in favour of mNGS compared to 29.0% (9/31) for CE (p < 0.05). Most polymicrobial infections were induced by anaerobic species that coexisted with Streptococcus constellatus. And Klebsiella pneumoniae was the most common isolated monomicrobial infection.

Conclusions

The most commonly detected causative pathogens for local pulmonary infections were bacteria, Mycobacterium spp. and fungi. Compared with the CE, the advantages of mNGS in the pathogens detection lie in the discovery of bacterial and mixed infections, as well as in the detection of lung abscess. Conversely, mNGS is not good enough to be recommendable for the detection of Mycobacterium spp. and fungi.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-022-01912-4.

Molecular detection of respiratory pathogens in community-acquired pneumonia involving adults

BACKGROUND

Community-acquired pneumonia (CAP) causes substantial morbidity and mortality in adults worldwide. The etiology of CAP often remains uncertain, and therapy is empirical. Thus, there is still room for improvement in the diagnosis of pneumonia.

METHODS

Adults aged >20 years who presented at the outpatient or emergency departments of Linkou and Keelung Chang Gung Memorial Hospital with CAP were prospectively included between November 2016 and December 2018. We collected respiratory specimens for culture and molecular testing and calculated the incidence rates of CAP according to pathogens.

RESULTS

Of 212 hospitalized adult patients with CAP, 69.3% were male, and the median age of the patients was 67.8 years. Bacterial pathogens were detected in 106 (50%) patients, viruses in 77 (36.3%), and fungal pathogens in 1 patient (0.5%). The overall detection rate (culture and molecular testing method) was 70.7% (n = 150). Traditional microbial culture yielded positive results in 36.7% (n = 78), molecular testing in 61.3% (n = 130). The most common pathogens were influenza (16.1%), followed by Klebsiella pneumoniae (14.1%), Pseudomonas aeruginosa (13.6%), human rhinovirus (11.8%), and Streptococcus pneumoniae (9.9%). Multiple pathogen co-infections accounted for 28.7% (n = 61), of which co-infection with K. pneumoniae and human rhinovirus comprised the largest proportion.

CONCLUSIONS

Molecular diagnostic testing could detect 23.6% more pathogens than traditional culture techniques. However, despite the current diagnostic tests, there is still the possibility that no pathogen was detected.

A 45-Year-Old Man With Acute Chest Pain, Fever, and Dyspnea After Tooth Extraction

CASE PRESENTATION

A 45-year-old Japanese man underwent wisdom tooth extraction. He developed right chest pain 2 days later, followed by continuous fever with dyspnea 2 weeks after the tooth extraction, and then came to our hospital. He complained of cough and purulent sputum.

The molecular characteristics, clinical manifestations, 44 and risk factors of hypervirulent Klebsiella pneumoniae infections in a large teaching hospital in southwest China

Hypervirulent Klebsiella pneumoniae (hvKp) has been globally disseminated recently, especially in Asia. The purpose of this study was to identify the molecular characteristics, clinical manifestations, and clinical risk factors of hvKp infections among patients in a large teaching hospital. A retrospective study was conducted in 123 patients infected with K. pneumoniae at the Affiliated Hospital of Southwest Medical University (Luzhou, China) from October 2016 to November 2018. An isolate that positive for both PCR amplification of aerobactin gene and Galleria mellonella infection model was defined as hvKp. Overall, 43.1% (53/123) of K. pneumoniae isolates were hvKp. String tests were performed on all isolates, and MLSTs of all hvKp were conducted. The K1 ST23 isolates were the dominant clone of hvKp (35.8%). Univariate analysis revealed the following risk factors for hvKp: hepatic abscess (OR = 41.818 [95% CI, 5.379-335.086]), bacteremia (OR = 19.94 [95% CI, 5.565-71.446]), metastatic spread (OR = 19.938 [95% CI, 6.344-62.654]), CRP (OR = 1.008 [95% CI, 1.001-1.015]), nitroimidazole treatment (OR = 7.907 [95% CI, 1.652-37.843]), diabetes (OR = 3.067 [95% CI, 1.38-6.817]), and admission to positive culture interval (OR = 3.636 [95% CI, 1.524-8.678]). Moreover, Multivariate analysis implicated hepatic abscess (OR = 74.332 [95% CI, 3.121-1769.588]), bacteremia (OR = 28.388 [95% CI, 3.039-264.200]), and metastatic spread (OR = 19.391 [95% CI, 3.633-103.498]) as independent risk factors for hvKp infections. Thirteen of twenty-one tested antibiotics were founded resistance to non-hvKp, which is significantly greater than hvKp. Importantly, the ESBL-hvKp and MDR-hvKp were responsible for 7.5% and 15.1% in the hvKp group, respectively.

Primary lung abscess due to multidrug-resistant Klebsiella pneumoniae

Primary lung abscess as a complication of necrotising community-acquired pneumonia due to multidrug-resistant (MDR) Klebsiella pneumoniae is rare. A 63-year-old man with a medical history of type 2 diabetes mellitus and chronic kidney disease was diagnosed with lung abscess due to MDR Klebsiella pneumoniae, a rare organism as a causative agent for community-acquired pneumonia. This unusual case revealed therapeutic challenges faced owing to factors such as drug-resistant pathogen, longer duration of antibiotics required for lung abscess and the chronic kidney status of the patient limiting the dosage of antibiotics. The clinical nuggets discussed in this case might pave the way in the future for management guidelines to be formulated in optimising the selection and duration of therapy for lung abscesses with MDR aetiology and in early recognition of this rare but dreaded entity.

Percutaneous transthoracic catheter drainage for lung abscess: a systematic review and meta-analysis

OBJECTIVES

To evaluate the outcomes of patients receiving image-guided percutaneous catheter drainage (PCD) for lung abscesses in terms of treatment success, major complications, and mortality as well as the predictors of those outcomes.

METHODS

Embase and OVID-MEDLINE databases were searched to identify studies on lung abscesses treated with PCD that had extractable outcomes. The outcomes were pooled using a random-intercept logistic regression model. Multivariate Firth's bias-reduced penalised-likelihood logistic regression analyses were performed to identify predictors of treatment success and complications. Methodological quality was assessed by summing scores of binary responses to items regarding selection, ascertainment of exposure and outcome, causality of follow-up duration, and reporting.

RESULTS

From 26 studies with acceptable methodological quality (median score, 4; range, 3-5), 194 patients were included. The pooled rates of treatment success and major complications were 86.5% (95% confidence interval [CI], 78.5-91.8%; I² = 23%) and 8.1% (95% CI, 4.1-15.3%; I² = 26%), respectively. Four patients eventually died from uncontrolled lung abscesses (pooled rate, 1.5%; 95% CI, 0.2-11.1%; I² = 36%). Malignancy-related abscess (odds ratio [OR], 0.129; 95% CI, 0.024-0.724; p = .022) and the occurrence of a major complication (OR, 0.065; 95% CI, 0.02-0.193; p < .001) were significant predictors of treatment failure. Traversing normal lung parenchyma was the only significant risk factor for major complications (OR, 27.69; 95% CI, 7.196-123.603; p < .001).

CONCLUSION

PCD under imaging guidance was effective for lung abscess treatment, with a low complication rate. Traversal of normal lung parenchyma was the sole risk factor for complications, and malignancy-related abscesses and the occurrence of major complications were predictors of treatment failure.

KEY POINTS

• The pooled treatment success rate of PCD for lung abscess was reasonably high (86.5%); malignancy-related abscesses and the occurrence of a major complication were predictors of treatment failure. • The pooled rate of percutaneous transthoracic catheter drainage-related major complications was 8.1% and traversing normal lung parenchyma by the catheter was the only risk factor. • The pooled mortality rate from uncontrolled lung abscesses with percutaneous transthoracic catheter drainage was low.

[Management of Adult Community-Acquired Pneumonia and Prevention - Update 2021 - Guideline of the German Respiratory Society (DGP), the Paul-Ehrlich-Society for Chemotherapy (PEG), the German Society for Infectious Diseases (DGI), the German Society of Medical Intensive Care and Emergency Medicine (DGIIN), the German Viological Society (DGV), the Competence Network CAPNETZ, the German College of General Practitioneers and Family Physicians (DEGAM), the German Society for Geriatric Medicine (DGG), the German Palliative Society (DGP), the Austrian Society of Pneumology Society (ÖGP), the Austrian Society for Infectious and Tropical Diseases (ÖGIT), the Swiss Respiratory Society (SGP) and the Swiss Society for Infectious Diseases Society (SSI)]

The present guideline provides a new and updated concept of the management of adult patients with community-acquired pneumonia. It replaces the previous guideline dating from 2016.The guideline was worked out and agreed on following the standards of methodology of a S3-guideline. This includes a systematic literature search and grading, a structured discussion of recommendations supported by the literature as well as the declaration and assessment of potential conflicts of interests.The guideline has a focus on specific clinical circumstances, an update on severity assessment, and includes recommendations for an individualized selection of antimicrobial treatment.The recommendations aim at the same time at a structured assessment of risk for adverse outcome as well as an early determination of treatment goals in order to reduce mortality in patients with curative treatment goal and to provide palliation for patients with treatment restrictions.

Pyogenic lung abscess in an infectious disease unit: a 20-year retrospective study

Background:

Pyogenic lung abscesses are rare and poorly described infections. This study aimed to describe their prognostic factors.

Methods:

We retrospectively included all patients hospitalized between 1 January 1998 and 1 June 2018, with an International Classification of Diseases, version 10 (IDC-10) diagnosis of pyogenic lung abscess, from the Diamm based medical records (Micro6, Nancy, France). Parasitic, fungal, or mycobacterial lung abscesses were excluded.

Results:

A total of 64 patients were included. Abscesses were associated with immunosuppression in 28 patients, including HIV infection and immunosuppressive therapy for eight and 12 patients, respectively. Bacterial identification was obtained for 36 patients. Nine patients (14%) developed lung abscesses after hematogenous dissemination. They differed from bronchogenic abscesses by their younger age (p = 0.03), the absence of smoking or emphysema (p = 0.05), Staphylococcus aureus (p = 0.001) or Streptococcus spp. (p = 0.05) isolation, and the smaller size of their abscess (p = 0.02). Overall, evolution was marked by radiological sequelae (46.9%), relapse (12.5%), and death (4.8%). Radiological sequelae occurred more frequently during the course of bronchogenic abscesses (p = 0.02), particularly when they spontaneously discharged (p = 0.04). Relapses were more frequent in patients with emphysema (p = 0.04) and when Haemophilus influenzae was isolated (p = 0.04). In multivariate analysis, poor outcomes, including death, sequelae, and relapse occurred more frequently in patients who had bronchogenic abscess (p = 0.02), and in those who received antibiotics during less than 6 weeks (p = 0.05).

Conclusion:

A duration of antibiotic treatment of less than 6 weeks and bronchogenic presentation were globally associated with poor outcome of pyogenic lung abscesses. These data should be considered when proposing guidelines for the care of pyogenic lung abscesses.

The reviews of this paper are available via the supplemental material section.

[Management of Lung Abscess - Diagnostics and Treatment]

Lung abscess is a localized infectious pus-filled cavity of the lung tissue by viral, bacterial, mycotic or parasitic pathogens. Currently, there are different classifications, which are based primarily on the genesis and duration of symptoms. Important steps for diagnosis are in addition to clinical examination, laboratory and chest X-ray especially bronchoscopy with microbiological examinations and computed tomography. Treatment of lung abscesses continues to be a domain of conservative antibiotic therapy. The vast majority of cases can be cured with this. Interventional procedures such as transthoracic or endobronchial abscess drainage with subsequent irrigation can effectively support the healing process. Thoracic surgery is particularly important in cases of failure of conservative and interventional therapy as well as secondary abscesses on the basis of a lung carcinoma. Mostly anatomical resections are required. Alternatively, VAC therapy (vacuum-assisted closure therapy) may be considered in seriously ill, old, immunosuppressed, and multimorbid patients with complicated abscesses (e.g. perforation in the pleural cavity and sero-pneumothorax).

AmpR Increases the Virulence of Carbapenem-Resistant Klebsiella pneumoniae by Regulating the Initial Step of Capsule Synthesis

Background

Non-hypermucoviscous carbapenem-resistant Klebsiella pneumoniae with enhanced virulence lacking hvKP-specific virulence factors is uncommon, and the virulence mechanisms of this organism are not understood.

Methods

Following a retrospective study of carbapenem-resistant K. pneumoniae based on core genome multilocus sequence typing (cgMLST), isolates that caused high mortality were investigated with a genome-wide association study (GWAS), proteome analysis and an animal model.

Results

The subclone of sequence type 11 (ST11) K. pneumoniae, which belongs to complex type 3176 (CT3176) and K-locus 47 (KL47), was highlighted due to the high mortality of infected patients. GWAS analysis showed that transcriptional regulatory gene ampR was associated with the CT3176 isolates. In a mouse model, the mortality, bacterial load and pathological changes of mice infected with ampR-carrying isolates were distinct from those infected with ampR-null isolates. The ampR gene that enhances the virulence of the non-hypermucoviscous KL47 strain was unable to enhance the virulence of hypermucoviscous KL1 strain. Proteome analysis showed that the expression of WcaJ in the ampR⁺ isolates was significantly higher than that in the ampR⁻ isolates. Quantification of capsular polysaccharide confirmed that more capsule polysaccharide was produced by ampR⁺ and ampR-complementary strains compared to ampR⁻ strains. It is suggested that the enhancement of the initial stage of capsule synthesis may be the cause of the enhanced virulence of these non-hypermucoviscous ST11 carbapenem-resistant K. pneumoniae isolates.

Conclusion

Non-hypermucoviscous ST11 carbapenem-resistant K. pneumoniae with enhanced virulence warrants continued surveillance and investigation.

Aspiration pneumonia and pneumonitis: a spectrum of infectious/noninfectious diseases affecting the lung

PURPOSE OF REVIEW

Our purpose is to describe aspiration pneumonia/pneumonitis as a spectrum of infectious/noninfectious diseases affecting the lung. We summarize diagnosis, risk factors, treatment, and strategies for prevention of aspiration.

RECENT FINDINGS

Aspiration is present in normal individuals, and disease manifestation depends on the chemical characteristics, frequency, and volume of inoculum. Anaerobes, though present, are no longer the predominant microbes isolated in aspiration pneumonia. Targets for preventing aspiration including improved oral hygiene and positional feeding have had mixed results. Patients diagnosed by clinicians with aspiration pneumonia experience greater morbidity and mortality than patients with community-acquired pneumonia.

SUMMARY

Aspiration pneumonia and pneumonitis are part of the pneumonia continuum and share similarities in pathophysiology, microbiology, and treatment. Modern microbiology demonstrates that the lung is not sterile, and isolates in aspiration pneumonia frequently include aerobes or mixed cultures. Treatment for aspiration pneumonia should include antibiotic coverage for oral anaerobes, aerobes associated with community-acquired pneumonia, and resistant organisms depending on appropriate clinical context. Additional studies targeting prevention of aspiration and investigating the increased morbidity and mortality associated with aspiration pneumonia are warranted.

Fluid-filled Cystic Lesions of the Lungs

A pulmonary cyst usually refers to an air-filled space with a smooth, thin wall. Fluid-filled cystic lesions of the lungs include a range of etiologies such as true cysts, congenital malformations, infections, and benign and malignant neoplasms. With relatively little solid component, these lesions often have similar imaging appearances to one another. This article focuses on key imaging features and clinical characteristics that can be used to narrow the differential diagnosis.

Comparison between Patients with Chest Infection due to Klebsiella spp. and Streptococcus pneumoniae

Objective In Japan, the aging demographic structure is becoming pronounced, and the full-blown graying of society appears not far off, which indicates an increasing population that will require healthcare contact. Klebsiella spp. are major pathogens in healthcare-associated infections, and their importance is increasing. The aim of this study was to clarify the characteristics of Klebsiella spp. chest infections by evaluating the differences in the characteristics of chest infections caused by Klebsiella spp. and pneumoniae. Methods We conducted a retrospective study of consecutive patients hospitalized with pneumonia, lung abscess/necrotizing pneumonia, and empyema due to Klebsiella spp. and S. pneumoniae for 15 years at our institution in Saitama, Japan. Patients Patients with chest infections due to Klebsiella spp. (K group, n=76) and S. pneumoniae (S group, n=446) were included. Results The K group more frequently was male, older, coinfected by Pseudomonas aeruginosa, and had diabetes mellitus, a history of upper digestive system surgery, alcohol drinking habit, a smoking habit, and an impaired premorbid performance status than the S group. The percentages of lung abscesses or necrotizing pneumonia (31.6% vs. 0.9%) and empyema without pulmonary parenchymal shadow (3.9% vs. 0.7%) were higher in the K group than those in the S group. Severity on admission and mortality did not differ between the groups; however, patients in the K group required a longer duration of antibiotics administration and hospital stay than those in the S group. Conclusion Klebsiella spp. chest infections have some marked characteristics when compared with pneumococcal infections, and our results serve to differentiate Klebsiella spp. infection from pneumococcal infection.

Antibiotic instillation for a chronic lung abscess

Introduction

Antibiotic treatment of lung abscesses fails in 10-20% of cases and require surgery, however, some are unsuitable for resection. Alternative options carry significant morbidity.

Case report

A 47 year old man with inoperable non-small cell lung cancer developed a lung abscess following definitive radiotherapy. Initial antibiotic therapy was successful, however four years later his symptoms recurred. Despite multiple courses his symptoms recurred despite long-term antibiotics. Immediately following a diagnostic aspiration, ceftriaxone and metronidazole were instilled into the abscess with subsequent clinical and radiological resolution.

Discussion

Lung abscesses are an uncommon complication of radiotherapy. Antibiotic therapy can fail for a number of reasons. Although instillation of antibiotics has not been described in the management of lung abscesses, the direct application of antifungals for aspergillomas is well documented and case series report success in other abscess sites.

Conclusion

Direct antibiotic instillation following lung abscess aspiration adds minimal risk and is potentially curative.

A Malaysian ex-smoker with cough, breathlessness and nonresolving bronchospasm

Repeated noisy breathing may be a tricky feature of lung infection. Recognising classical features in radiographs and CT scans may help in the diagnosis of severe lung infection and the start of life-saving treatment. http://bit.ly/2lQwe5y.

A community-acquired lung abscess attributable to odontogenic flora

A lung abscess is an infectious pulmonary disease characterized by pus-filled cavity formation and often an air-fluid level. In this article, we described an indolent community-acquired lung abscess suspected as a tumor previously. A 56-year-old male presented with cough and expectoration for 2 months and hemoptysis for 2 weeks. His physical examinations, whole blood count and C-reactive protein level were normal. The chest computed tomography (CT) scan showed a 40×38×39 mm high-density mass in the right upper pulmonary lobe, with irregular borders. The pathology of a CT-guided percutaneous needle aspiration biopsy showed numerous inflammatory cells and bacteria infiltration without tumor lesions. Bacteriological detection of lung tissue revealed the cause was odontogenic flora. A next-generation sequencing demonstrated the etiologic correlation between lung abscess and periodontitis. After a 2-month pathogen-directed oral antibiotics therapy combined with chlorhexidine gargle oral care, this patient showed a remarkable improvement. Periodontitis can be a cause of a lung abscess, which would be taken into account in the treatment regimes preventing infectious recurrence.

Hypervirulent Klebsiella pneumoniae

Hypervirulent K. pneumoniae (hvKp) is an evolving pathotype that is more virulent than classical K. pneumoniae (cKp). hvKp usually infects individuals from the community, who are often healthy. Infections are more common in the Asian Pacific Rim but are occurring globally. hvKp infection frequently presents at multiple sites or subsequently metastatically spreads, often requiring source control. hvKp has an increased ability to cause central nervous system infection and endophthalmitis, which require rapid recognition and site-specific treatment. The genetic factors that confer hvKp's hypervirulent phenotype are present on a large virulence plasmid and perhaps integrative conjugal elements. Increased capsule production and aerobactin production are established hvKp-specific virulence factors. Similar to cKp, hvKp strains are becoming increasingly resistant to antimicrobials via acquisition of mobile elements carrying resistance determinants, and new hvKp strains emerge when extensively drug-resistant cKp strains acquire hvKp-specific virulence determinants, resulting in nosocomial infection. Presently, clinical laboratories are unable to differentiate cKp from hvKp, but recently, several biomarkers and quantitative siderophore production have been shown to accurately predict hvKp strains, which could lead to the development of a diagnostic test for use by clinical laboratories for optimal patient care and for use in epidemiologic surveillance and research studies.

[Lung abscess: Diagnosis and management]

Lung abscesses are necrotic cavitary lesions of the lung parenchyma. They are usually caused by anaerobic bacteria or mixed flora and typically occur after aspiration. Primary lung abscesses occur in previously healthy patients with no underlying medical disorders and are usually solitary. Secondary lung abscesses occur in patients with underlying or predisposing conditions and may be multiple. The initial diagnosis is usually made by chest radiography showing a lung cavity with an air-fluid level. Typically, the cavity wall is thick and irregular, and a surrounding pulmonary infiltrate is often present. The differential diagnosis of pulmonary cavitation is wide, including different types of possible infections, neoplasia and malformations of the bronchial tree. Management is usually based on prolonged antibiotic treatment. Failure of conservative management, manifested by the persistence of sepsis and/or other abscess complications, may necessitate drainage with invasive techniques (percutaneous, endoscopic or surgical) or open surgical removal of the lung lesion in patients with good performance status and sufficient respiratory reserve.

Antibiotic treatment for pneumonia complicating stroke: Recommendations from the pneumonia in stroke consensus (PISCES) group

Purpose

The microbiological aetiology of pneumonia complicating stroke is poorly characterised. In this second Pneumonia in Stroke ConsEnsuS statement, we propose a standardised approach to empirical antibiotic therapy in pneumonia complicating stroke, based on likely microbiological aetiology, to improve antibiotic stewardship.

Methods

Systematic literature searches of multiple databases were undertaken. An evidence review and a round of consensus consultation were completed prior to a final multi-disciplinary consensus meeting in September 2017, held in Barcelona, Spain. Consensus was approached using a modified Delphi technique and defined a priori as 75% agreement between the consensus group members.Findings: No randomised trials to guide antibiotic treatment of pneumonia complicating stroke were identified. Consensus was reached for the following: (1) Stroke-associated pneumonia may be caused by organisms associated with either community-acquired or hospital-acquired pneumonia; (2) Treatment for early stroke-associated pneumonia (<72 h of stroke onset) should cover community-acquired pneumonia organisms; (3) Treatment for late stroke-associated pneumonia (≥72 h and within seven days of stroke onset) should cover community-acquired pneumonia organisms plus coliforms +/- Pseudomonas spp. if risk factors; (4) No additional antimicrobial cover is required for patients with dysphagia or aspiration; (5) Pneumonia occurring after seven days from stroke onset should be treated as for hospital-acquired pneumonia; (6) Treatment should continue for at least seven days for each of these scenarios.

Discussion

Consensus recommendations for antibiotic treatment of the spectrum of pneumonia complicating stroke are proposed. However, there was limited evidence available to formulate consensus on choice of specific antibiotic class for pneumonia complicating stroke.

Conclusion

Further studies are required to inform evidence-based treatment of stroke-associated pneumonia including randomised trials of antibiotics and validation of candidate biomarkers.

Unusual case of a giant lung abscess initially misdiagnosed and treated as an empyema

We report the case of a 66-year-old man with dental infection who presented to our emergency department complaining of a 3-month medical history of chest pain and productive cough, in association with malaise, fever, weight loss and anaemia. His chest radiograph showed a nearly total opacification of the right hemithorax and chest ultrasound findings were suggestive of empyema, subsequently confirmed by a chest CT. The patient started appropriate treatment. A follow-up chest CT performed to rule out bronchopleural fistula revealed a large lung abscess. The patient had the final diagnosis of a giant lung abscess, which was initially thought to be an empyema because of the clinical and radiologic similarities with this entity. The initial misdiagnosis led to prompt percutaneous drainage of the lung abscess in addition to antibiotherapy and respiratory physiotherapy with a good final outcome, which suggests the efficacy of this approach in similar cases.

Logistic regression analysis of clinical and computed tomography features of pulmonary abscesses and risk factors for pulmonary abscess-related empyema

OBJECTIVES

This study was conducted to investigate the risk factors for pulmonary abscess-related empyema by investigating the clinical characteristics and chest computed tomography imaging features of patients with pulmonary abscesses.

METHODS

We retrospectively analyzed the chest computed tomography findings and clinical features of 101 cases of pulmonary abscess, including 25 cases with empyema (the experimental group) and 76 cases with no empyema (the control group). The potential risk factors for pulmonary abscess-related empyema were compared between the groups by using univariate and multivariate logistic regression analyses.

RESULTS

The incidence of pulmonary abscess-related empyema was 24.8% (25/101). Univariate analysis showed that male gender, diabetes, pleuritic symptoms, white blood cells >10×109/L, albumin level <25 g/L, and positive sputum cultures were potential clinical-related risk factors and that an abscess >5 cm in diameter and transpulmonary fissure abscesses were potential computed tomography imaging-related risk factors for pulmonary abscess-related empyema. Multivariate logistic regression analysis showed that transpulmonary fissure abscesses (odds ratio=9.102, p=0.003), diabetes (odds ratio=9.066, p=0.003), an abscess >5 cm in diameter (odds ratio=8.998, p=0.002), and pleuritic symptoms (odds ratio=5.395, p=0.015) were independent risk factors for pulmonary abscess-related empyema.

CONCLUSIONS

Transpulmonary fissure abscesses, diabetes, giant pulmonary abscesses, and pleuritic symptoms increased the risk of empyema among patients with pulmonary abscesses.

The Transbronchial Drainage of a Lung Abscess Using Endobronchial Ultrasonography with a Modified Guide Sheath

Lung abscess is usually treated with long-term antibiotic therapy. Due to the lack of a safe and easy drainage technique, drainage is only applied in refractory cases. We herein describe three cases in which drainage was successfully performed by endobronchial ultrasonography using a modified guide sheath. This procedure may have advantages in the detection of causative pathogens and early infection source control, and may therefore lead to the appropriate selection of antibiotics and reduce the duration of antibiotic therapy.

Clinical, Radiological and Bacteriological Profile of Lung Abscess - An Observational Hospital Based Study

BACKGROUND:

The incidence of lung abscess acquired in the community is unknown, but this is a common clinical problem encountered in developing countries. The incidence of lung abscess was high in the pre-antibiotic era but the advent of susceptible antibiotics it has reduced with an equal fall in mortality to 8.7%. With the emerging antibiotic resistance and change in the trends of bacteriological profile causing lung abscess, it is the need of time to reevaluate lung abscess.

AIM:

The study aimed to determine the clinical, radiological and bacteriological profile of lung abscess.

MATERIAL AND METHOD:

The study was a non-randomized prospective observational study conducted in the department of pulmonary medicine for 18 months. In the study, patients > 15 years of age with clinical features of lung abscess were recruited and were subjected to chest X-ray, routine blood test. Sputum gram stain and culture, as well as antibiotic sensitivity according to the organism, were evaluated. Reports of all investigations along with patient characteristics and risk factors were analysed statistically using SPSS 20.0.

RESULTS:

Forty-six cases of lung abscess were included, and the majority of patients were found to be adults with a mean age of 42.9 years with a male to female ratio of 6.6:1. The most common predisposing factor was an unhygienic oral cavity in 28% of cases with alcohol ingestion being the most important risk factor in 22% of cases. The most common organism found in lung abscess cases was Klebsiella pneumoniae, and they were sensitive to ceftazidime.

CONCLUSION:

Our study shows that Klebsiella pneumoniae should be considered an important pathogen in community-acquired lung abscesses.

Endogenous Endophthalmitis Caused by Carbapenem-Resistant Hypervirulent Klebsiella Pneumoniae: A Case Report and Literature Review

Purpose: To report a rare case of endogenous endophthalmitis caused by carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKP). Methods: A retrospective chart review was conducted. The isolates were characterized by hypermucoviscosity, resistance genes, virulence genes, and multilocus sequence typing. Results: A 47-year-old diabetic woman acquired carbapenem-resistant K. pneumoniae (CRKP) nosocomial pneumonia. Metastatic endophthalmitis occurred in the right eye a week after the occurrence of CRKP bloodstream infection (BSI). Visual acuity decreased to light perception within 3 days. Although vitrectomy relieved ocular pain, endophthalmitis deteriorated due to uncontrollable BSI, and developed to corneal perforation. The strains isolated from bronchoalveolar lavage fluid, blood, and intraocular pus originated from the same clone. The pathogen was hypermucoviscous, belonged to sequence type 11, harbored resistance genes bla_KPC-2, bla_TEM, bla_SHV, rmtB, and virulence genes rmpA2, iucABCD, iroBCD. Conclusions: Endogenous endophthalmitis caused by CR-hvKP has emerged, which is a treatment challenge for both ophthalmologists and physicians.

An unusual case of lung abscess secondary to round pneumonia caused by recurrent Klebsiella pneumoniae strain and the role of occult metastases tumor

Round pneumonia is an uncommon form of community-acquired pneumonia usually found in children. To this date, there has been no report on local pulmonary complications in this entity in adult patients. The present study reports a case of a 77-year-old male with lung abscess secondary to round pneumonia caused by recurrent Klebsiella pneumoniae infection accompanied by occult metastases tumor. Occult metastases may have played an important role in leading to cavity as in this present case. Further investigation regarding the relationship between recurrent infection and metastases is needed.

Lung abscess caused by Streptococcus pneumoniae serotype 6B

Lung abscess has been considered to be a rare complication of pneumococcal infection, and most cases are reported to be Streptococcus pneumoniae serotype 3. A 67-year-old man presented with fever and was diagnosed to have lung abscess caused by S. pneumoniae serotype 6B. The minimal inhibitory concentration (MIC) of penicillin for the isolate was 1 μg/mL. He was treated with high-dose intravenous sulbactam/ampicillin as definitive therapy based on susceptibility testing for S. pneumoniae and recovered successfully without surgical intervention. S. pneumoniae serotype 6B can cause lung abscess.