Detection of expanded-spectrum β-lactamases in Gram-negative bacteria in the 21st century

Collateral Changes in Cell Physiology Associated with ADC-7 β-Lactamase Expression in Acinetobacter baumannii

The ADC (AmpC) β-lactamase is universally present in the Acinetobacter baumannii chromosome, suggesting it may have a yet-to-be-identified cellular function. Using peptidoglycan composition analysis, we show that overexpressing the ADC-7 β-lactamase in A. baumannii drives changes consistent with altered l,d-transpeptidase activity. Based on this, we tested whether cells overexpressing ADC-7 would exhibit new vulnerabilities. As proof of principle, a screen of transposon insertions revealed that an insertion in the distal 3' end of canB, encoding carbonic anhydrase, resulted in a significant loss of viability when the adc-7 gene was overexpressed. A canB deletion mutant exhibited a more pronounced loss of viability than the transposon insertion, and this became amplified when cells overexpressed ADC-7. Interestingly, overexpression of the OXA-23 or TEM-1 β-lactamases also led to a pronounced loss of viability in cells with reduced carbonic anhydrase activity. In addition, we demonstrate that reduced CanB activity led to increased sensitivity to peptidoglycan synthesis inhibitors and to the carbonic anhydrase inhibitor ethoxzolamide. Furthermore, this strain exhibited a synergistic interaction with the peptidoglycan inhibitor fosfomycin and ethoxzolamide. Our results highlight the impact of ADC-7 overexpression on cell physiology and reveal that the essential carbonic anhydrase CanB may represent a novel target for antimicrobial agents that would exhibit increased potency against β-lactamase-overexpressing A. baumannii. IMPORTANCE Acinetobacter baumannii has become resistant to all classes of antibiotics, with β-lactam resistance responsible for the majority of treatment failures. New classes of antimicrobials are needed to treat this high-priority pathogen. This study had uncovered a new genetic vulnerability in β-lactamase-expressing A. baumannii, where reduced carbonic anhydrase activity becomes lethal. Inhibitors of carbonic anhydrase could represent a new method for treating A. baumannii infections.

Detection of Extended-Spectrum β-Lactamases (ESBLs) and AmpC in Class A and Class B Carbapenemase-Producing Enterobacterales

In carbapenemase-producing Enterobacterales (CPE) additional β-lactam resistance mechanisms such as extended-spectrum-β-lactamases (ESBL) and/or AmpC-β-lactamases are generally difficult to detect by phenotypical methods. Recently, a modified version of the CLSI ESBL confirmatory combination disc diffusion (CDD) test, which involves the addition of boronic acid and EDTA on discs containing ESBL and AmpC substrates ± inhibitors, has been proposed for the detection of ESBL in class A and class B CPE. Here, the performance of the modified CDD test was evaluated using 121 genotypically characterized class A and class B CPE. Also, the effectiveness of the NG-Test CTX-M-MULTI lateral flow immunoassay was evaluated for ESBL detection. For class A CPE (n = 47), the modified CDD method exhibited an equal specificity (95.7%) and a higher sensitivity (100%) compared to the standard method (91.7%). The CTX-M-MULTI test detected ESBL in all CTX-M-type ESBL producers (n = 23), whereas it was negative for all CTX-M-type ESBL-negative isolates (n = 24). For class B CPE (n = 71), the modified method significantly improved both sensitivity (95%) and specificity (100%) in detecting ESBL compared to the standard method (17.5% sensitivity and 83.9% specificity). In comparison, the CTX-M-MULTI led to identification of ESBL in all CTX-M-ESBL-producers (n = 39) and no false-positive signal was generated with the CTX-M-type-ESBL-negative isolates (n = 30). Furthermore, the modified CDD improved the robustness of the method for AmpC detection (inconclusive results were produced in 53/57 and 10/57 cases with the standard and modified method, respectively), although the sensitivity of the test was poor (23.5%). Here, we propose a practical and cost-effective approach combining the modified CDD and the CTX-M-MULTI test for detection of ESBL and/or AmpC in class A and B CPE. IMPORTANCE Antimicrobial resistance is a growing public health threat of broad concern worldwide. Timely detection of antibiotic resistance mechanisms can help to monitor and to curb the spread of resistant bacteria within the hospital setting as well as in the environment. In this work we report an accurate and affordable method to phenotypically identify difficult-to-detect resistance determinants in highly resistant (carbapenemase-producing) bacteria. This method may be implemented in any diagnostic microbiology lab and may reduce the underreporting of relevant resistance mechanisms.

Multidrug-Resistant Acinetobacter baumannii in Jordan

Background: Acinetobacter baumannii is a common cause of multi-drug (MDR)-resistant infections worldwide. The epidemiological and molecular characteristics of MDR-A. baumannii in Jordan is not known. Methods: A. baumannii isolates were collected from 2010 to 2020 from three tertiary hospitals in Jordan. Demographic and clinical data, isolates information, antibiotic susceptibility patterns, phenotypic, and molecular characterization of carbapenem resistance genes were performed. Results: A total of 622 A. baumannii isolates were collected during the study period. Most isolates were from males, aged 18−60 years, Jordanian, from infected wounds, and were patients in surgery or critical care units. Among patients from whom A. baumannii was isolated, associated risk factors for MDR were adults over 60, males, critically ill patients and infected wounds (OR 4.14, 2.45, 10, 7, respectively, p < 0.0001). Incidence rates from 2010 to 2015 showed a slight increase in MDR (3.75/1000 to 4.46/1000). Resistance patterns indicated high resistance for most cephalosporins, carbapenems, and fluoroquinolones, moderate resistance for trimethoprim/sulfamethoxazole and ampicillin/sulbactam, low resistance for aminoglycosides and tetracyclines, while colistin and tigecycline, have the lowest resistance rates. 76.8% of A. baumannii isolates were MDR and 99.2% were carbapenem-resistant. All isolates were positive for the OXA-51 gene (100%), 98.5% were positive for the OXA-23 gene, 26.6% for the VIM gene, while KPC and IMP genes were almost not detected (0% and 0.8% respectively). Conclusions: This is the first large, multicentric, prolonged study that provides insights into A. baumannii infections in Jordan. Attention to patients at higher risk is important for early identification. Colistin and tigecycline were the most effective antimicrobials.

Virulence factors, antibiotic resistance patterns, and molecular types of clinical isolates of Klebsiella Pneumoniae

BACKGROUND

Klebsiella pneumoniae is armed with a wide range of antibiotic resistance mechanisms that mostly challenge effective treatment. The aims of the current study were to identify the clinical strains of K. pneumoniaealso to determine their phenotypes and molecular characterization related to antimicrobial resistance and virulence genes.

RESEARCH DESIGN AND METHODS

In this investigation, clinical specimens from different hospitals located in Tehran, Iran, were collected during a nine-month period (December 2018 to August 2019). The K. pneumoniae strains were isolated and identified through standard microbial and biochemical assays. Additionally, disk diffusion, combined disk, Modified Hodge Test (MHT) and PCR were performed for antibiotic resistance and virulence gene analysis, respectively.

RESULTS

Eighty-four isolates of K. pneumoniae were subjected to the study. According to the combined disk and modified Hodge test results, 27 (52%) and 15 pathotypes (62.5%) out of resistant strains of isolated K. pneumoniae were detected as ESBL and KPC producers. The virulence genes of mrkD (94%) and magA (11%) were the highest and lowest among isolates, respectively.

CONCLUSIONS

The high prevalence of antibiotic resistance and virulence genes in conjunction with a significant relationship between the strains revealed a high pathogenic capacity of the isolated pathotypes of K. pneumoniae.

Prevalence of OXA-Type β-Lactamase Genes among Carbapenem-Resistant Acinetobacter baumannii Clinical Isolates in Thailand

Carbapenem-resistant Acinetobacter baumannii (CRAB) is a critical health concern for the treatment of infectious diseases. The aim of this study was to investigate the molecular epidemiology of CRAB emphasizing the presence of oxacillinase (OXA)-type β-lactamase-encoding genes, one of the most important carbapenem resistance mechanisms. In this study, a total of 183 non-repetitive CRAB isolates collected from 11 tertiary care hospitals across Thailand were investigated. As a result, the blaoxa-51-like gene, an intrinsic enzyme marker, was detected in all clinical isolates. The blaoxa-23-like gene was presented in the majority of isolates (68.31%). In contrast, the prevalence rates of blaoxa-40/24-like and blaoxa-58-like gene occurrences in CRAB isolates were only 4.92% and 1.09%, respectively. All isolates were resistant to carbapenems, with 100% resistance to imipenem, followed by meropenem (98.91%) and doripenem (94.54%). Most isolates showed high resistance rates to ciprofloxacin (97.81%), ceftazidime (96.72%), gentamicin (91.26%), and amikacin (80.87%). Interestingly, colistin was found to be a potential drug of choice due to the high susceptibility of the tested isolates to this antimicrobial (87.98%). Most CRAB isolates in Thailand were of ST2 lineage, but some belonged to ST25, ST98, ST129, ST164, ST215, ST338, and ST745. Further studies to monitor the spread of carbapenem-resistant OXA-type β-lactamase genes from A. baumannii in hospital settings are warranted.

Diagnostic tools for bacterial infections in travellers: Current and future options

International travel has increased dramatically over the past 50 years, and travel destinations have diversified. Although physicians are more familiar with the panel of aetiological agents responsible for illnesses of returning travellers, thanks to regular epidemiological studies, the spectrum of pathogens potentially encountered in various travel destinations is nevertheless increasing. In addition, the wide array of approaches currently available and addressed in this paper could render the procedures for microbiological analyses increasingly complex. As the time to result is crucial to adequately manage patients, modern approaches have been developed to shorten diagnosis delays. The syndromic approach, which consists of simultaneously testing a wide panel of microorganisms, substantially increases the diagnostic yield with significant time savings, particularly when coupled with point-of-care laboratories. The tools commonly used for this purpose are immunochromatographic tests, mainly targeting bacterial antigens, and multiplex real-time PCR. The emergence of next-generation sequencing technologies, which enable random amplification of genetic material of any microbe present in a clinical specimen, provides further exciting perspectives in the diagnosis of infectious diseases.

Phenotypic and Genotypic Prevalence of Extended-Spectrum β-Lactamase-Producing Escherichia coli: A Systematic Review and Meta-Analysis in Iran

Background: Despite the existence of discrete and varied studies regarding extended-spectrum β-lactamase-producing Escherichia coli (ESBL-EC) in Iran, a comprehensive analysis on the prevalence of ESBL-EC has not yet been carried out. The current study analyzed published data regarding ESBL-EC in different regions of Iran to gain insight into this significant subject. Methods: A meta-analysis was performed using Comprehensive Meta-Analysis Software (version 2.2; Biostat) to determine the prevalence of ESBL-EC in Iran. A web-based search was conducted in electronic databases, including PubMed, Scopus, and Web of Sciences. The eligibility of articles published between 2008 and 2018 was assessed, and relevant data were extracted for statistical analysis. A random-effects model was used based on the heterogeneity test. Publication bias was determined using Begg's rank correlation and Egger's weighted regression methods. Results: Among 31,135 studies examined, 61 met inclusion criteria and were included for review. Iran's overall pooled proportion of ESBL-EC was 43.2% (confidence interval [95% CI] 39.2-47.3), and the overall heterogeneity (I²) between studies was significantly high (93.5%, p = 0.00). The most prevalent of ESBLs in E. coli was CTX-M and TEM, with prevalence of 31.2% (95% CI 25.4-37.6), 27.6% (95% CI 22.7-33.2), respectively. Conclusion: The available studies show a high rate of ESBL-EC in Iran. This result highlights a need for appropriate and rapid methods for estimating ESBL infection, which can help our understanding of the actual epidemiology of ESBL and provide protocols for the prevention and control of infection.

Detection of a novel clone of Acinetobacter baumannii isolated from a dog with otitis externa

In this study, the isolation of Acinetobacter baumannii in a dog with clinical bilateral otitis externa is described. Moreover, to investigate the zoonotic potential of the isolate, microbiological examinations on the family members were performed. An A. baumanniistrain was isolated from nasal swab in one of the dog owners. The identity of bacterial strains, either from dog and owner, was confirmed by phenotypic and molecular typing (wgMLST). Furthermore, to assess the pathogenic potential of the isolates a deep characterization of virulence and antibiotic resistance genes was done by Whole Genome Sequencing (WGS). Finally, the susceptibility towards a wide panel of antimicrobials was investigated. In our knowledge, this is the first recorded case of A. baumanniiisolation from canine auricular swabs in Italy. And interestingly, this study underlines the possible spread of this microorganism from human to animal.

Antibiotic-Induced, Increased Conjugative Transfer Is Common to Diverse Naturally Occurring ESBL Plasmids in Escherichia coli

Previously, we showed that cefotaxime (CTX) exposure increases conjugative transfer of a bla CTX-M- 1 encoding IncI1 plasmid (IncI1/pST49/CTX-M-1) in Escherichia coli in a SOS-independent manner. This study aimed at investigating whether the observation was unique for that plasmid/strain/antibiotic combination or whether antibiotic-induced plasmid transfer (PT) is a more general phenomenon among plasmids in E. coli. Whole genome sequences of 25 E. coli strains were analyzed to identify different extended spectrum beta-lactamases (ESBL) plasmids enabling selection of a diverse collection of plasmids. Experiments were performed following exposure of these strains to 1/2 minimal inhibitory concentration (MIC) of CTX, ampicillin (AMP), or ciprofloxacin (CIP) before conjugation experiments. The frequency of PT was measured and compared to that of donors not exposed to antibiotics. Reverse-transcribed-quantitative real time polymerase chain reaction (RT-qPCR) was used to measure mRNA levels of five PT genes and two SOS response genes in donors exposed to antibiotics. The PT of eight strains (30.8% of strains tested) with IncI1/pST7/CTX-M-1, IncI1/pST49/CTX-M-1, IncI1/pST3/CTX-M-1, IncI1/pST293/CTX-M-1, IncI1/pST295/CTX-M-1, IncI1/pST16/CTX-M-55, and IncFII/CTX-M-14 (n = 2) plasmids was significantly increased following antibiotic exposure. CTX increased PT in all of these eight strain/plasmid combinations, AMP and CIP increased the PT in six and three strains, respectively. RT-qPCR showed that PT genes were up-regulated in the presence of the three antibiotics, whereas SOS-response genes were up-regulated only following CIP exposure. Our findings reveal that antibiotics can increase PT in E. coli strains with various ESBL plasmids. Thus, antibiotic-induced conjugative transfer of ESBL plasmids appears to be a common phenomenon in E. coli, having important implications for assessing the risks of antibiotic use.

Rapid Detection of Extended-Spectrum β-Lactamases (ESBL) and AmpC β-Lactamases in Enterobacterales: Development of a Screening Panel Using the MALDI-TOF MS-Based Direct-on-Target Microdroplet Growth Assay

Introduction: Antibiotic resistant bacteria are a growing concern worldwide. Extended-spectrum β-lactamases (ESBL) represent the most common resistance mechanism of Gram-negative bacteria against β-lactams, underlining the need for adequate diagnostic methods that provide reliable information in the shortest time possible. AmpC, a less prevalent but increasingly relevant class of β-lactamases, pose an additional challenge as their detection is complex. Here, we present an ESBL and AmpC screening panel employing the MALDI-TOF MS-based direct-on-target microdroplet growth assay (DOT-MGA). Materials and Methods: Four reference strains recommended by the European Committee on Antimicrobial Susceptibility Testing (EUCAST) were used to develop the panel, which was further validated on 50 clinical Enterobacterales isolates resistant to third generation cephalosporins. The panel relies on the synergistic effect between ESBL and/or AmpC β-lactamase inhibitors and cephalosporins, which indicates β-lactamase production. Microdroplets containing the tested microorganism, cephalosporins in different concentrations and inhibitors were pipetted onto an MBT Biotarget and incubated for 3 or 4 h at 35 ± 1°C. Afterward, the liquid medium was removed and the material adhered to the spots was analyzed by MALDI-TOF MS. Synergy was detected by determining and comparing the minimum inhibitory concentrations of the tested cephalosporins with and without β-lactamase inhibitors. Data were interpreted following a diagnostic algorithm proposed by EUCAST in order to establish a final diagnosis. In comparison, PCR, broth microdilution (BMD) and combination disk tests (CDT) were performed. Results: Compared to the PCR results, the following positive and negative percent agreement values (PPA/NPA) were obtained for each resistance mechanism: ESBL, 94.44/100%; AmpC, 94.44/93.75% and ESBL+AmpC, 100/100%. These results, obtained after 4 h of incubation, were comparable with those of BMD and showed a higher accuracy than CDT. Discussion: We propose a novel phenotypic method for detection of ESBL and AmpC β-lactamases in Enterobacterales that provides reliable results in a short time, representing a promising alternative to the diagnostic techniques currently available. This easy-to-perform approach has potential for being implemented in routine laboratories, contributing to the further diversification of mass spectrometry technology into other fields such as antibiotic resistance testing.

Highly selective and wash-free visualization of resistant bacteria with a relebactam-derived fluorogenic probe

An unprecedented relebactam-based fluorogenic probe is reported for the wash-free imaging of resistant bacteria.

Short communication: Extended-spectrum AmpC-producing Escherichia coli from milk and feces in dairy farms in Brazil

The AmpC enzyme is normally expressed constitutively in Escherichia coli, and its overproduction confers resistance to cefoxitin. A newly reported AmpC, the extended-spectrum AmpC (ESAC), is related to resistance to cefepime, a fourth-generation cephalosporin. This enzyme presents more flexibility in the active site due to insertions, replacements, and deletions on AA sequences. Many isolates producing ESAC were reported in human clinical isolates, but E. coli ESAC producers were reported in animals only in France. The animal E. coli strains can produce this enzyme and possibly disseminate it to human and production environments. In our study, 3 strains of E. coli from milk and feces bovine samples, collected in Rio de Janeiro, Brazil, were suspected to produce ESAC. After excluding other mechanisms of resistance, the gene was sequenced to verify ESAC characteristics. These strains presented replacement of AA in omega and R2 loops, suggesting ESAC production. This is the first report to study ESAC E. coli in dairy farms in Brazil.

Resistant Gram-Negative Bacteria and Diagnostic Point-of-Care Options for the Field Setting during Military Operations

The spread of multidrug-resistant bacteria in resource-poor settings affects the military medical service in case of deployments of soldiers to war and crisis zones. Patients with war injuries are prone to colonization or infection with multidrug-resistant bacteria. Resistant Gram-negative bacteria play a dominant role in military wound infections. Problematic hygiene conditions on deployment facilitate exposition of soldiers with subsequent colonization. Although colonizing strains are frequently cleared from their hosts after returning from deployment, transmission to close contacts of the soldiers in the home country cannot be excluded and therapeutic options are reduced if colonization progresses to invasive infection. Since sophisticated culture-based diagnostic approaches are typically not available in the field setting on deployment, molecular rapid diagnostic test systems are an option for transmission control if the locally prevalent molecular resistance mechanisms are known. Efforts for global resistance surveillance can contribute to better understanding of resistance distribution and spread at deployment sites. This review summarizes experience of the military medical services with multidrug resistance on deployment and with the influx of resistant strains to the home country and discusses potential use of available molecular rapid test systems as an option for the field setting.

Management of infections caused by extended-spectrum β-lactamase-producing Enterobacteriaceae: current evidence and future prospects

INTRODUCTION

The spread of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae has become a major public health threat worldwide. Area covered: A thorough systematic literature review describing the current evidence and future prospects of therapeutic options for infections caused by ESBL-producing Enterobacteriaceae. Expert commentary: The methods of detecting ESBLs have been evolving. The Clinical and Laboratory Standards Institute and the European Committee on Antimicrobial Susceptibility Testing lowered the MIC breakpoints of cephalosporins against ESBL-producing Enterobacteriaceae in 2010. Phenotypic testing for ESBLs is no longer recommended. Instead, the selection of appropriate antimicrobial agents largely depends on the report of minimum inhibitory concentrations (MICs). To date, therapeutic options for these multidrug-resistant organisms remain limited. The clinical efficacy of piperacillin/tazobactam and cefepime on in vitro-susceptible ESBL-producing Enterobacteriaceae remains a concern. Many studies found an in vitro-in vivo discordance based on current breakpoints. Carbapenems are the most reliable antibiotics for severe infections caused by ESBL-producing Enterobacteriaceae. However, their overuse has led to a serious problem of increasing drug resistance. Recently, ceftolozane/tazobactam and ceftazidime/avibactam have been approved for the treatment of complicated urinary tract infections and complicated intra-abdominal infections. The introduction of these new β-lactam/β-lactamase inhibitor combinations offers new carbapenem-sparing options for the treatment of ESBL infections.

A multi-centre prospective evaluation of the Check-Direct ESBL Screen for BD MAX as a rapid molecular screening method for extended-spectrum beta-lactamase-producing Enterobacteriaceae rectal carriage

OBJECTIVE

A multiplex extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-E) quantitative polymerase chain reaction (qPCR), performed directly on rectal swabs, was compared with a culture-based protocol to study the discrepancies between the two methods, and identify existing challenges to apply this assay in routine clinical practice. The secondary objective was to assess the performance of the qPCR.

MATERIALS AND METHODS

In two Dutch teaching hospitals, 573 rectal swabs were collected prospectively. Culture with additional testing with the Check-MDR CT103XL (Check-Points) was compared with the Check-Direct ESBL Screen for BD MAX (Check-Points), which detects the presence of the ESBL gene families CTX-M1, CTX-M2, CTX-M9 and SHV2/5-ESBL. The culture-based protocol (with Brilliance agar) was considered as the gold standard to assess the performance of the qPCR.

RESULTS

Of the 573 rectal swabs, 74 (12.9%) were culture-positive. Eighty-four (14.7%) were qPCR-positive. There were eight culture-positive/qPCR-negative discrepancies and 18 culture-negative/qPCR-positive discrepancies. Sensitivity and specificity of qPCR vs culture were 87.7% [95% confidence interval (CI) 79.7-95.7] and 96.3% (95% CI 94.6-98.0), respectively.

CONCLUSION

The Check-Direct ESBL Screen for the BD MAX is an easy-to-perform, quick molecular diagnostic test with the potential to significantly speed up screening for rectal ESBL-E carriage. Discrepancies were observed between the culture-based protocol and the qPCR in 4.5% of tested samples. Existing challenges for implementing qPCR are its limited sensitivity, the need for thorough knowledge of the local ESBL-E genes, and interpretation of culture-negative but qPCR-positive samples. It is believed that the limited sensitivity of qPCR could be optimized by including bla_TEM as a molecular target, and improving the limit of detection.

More Pathogenicity or Just More Pathogens?-On the Interpretation Problem of Multiple Pathogen Detections with Diagnostic Multiplex Assays

Modern molecular diagnostic approaches in the diagnostic microbiological laboratory like real-time quantitative polymerase chain reaction (qPCR) have led to a considerable increase of diagnostic sensitivity. They usually outperform the diagnostic sensitivity of culture-based approaches. Culture-based diagnostics were found to be insufficiently sensitive for the assessment of the composition of biofilms in chronic wounds and poorly standardized for screenings for enteric colonization with multi-drug resistant bacteria. However, the increased sensitivity of qPCR causes interpretative challenges regarding the attribution of etiological relevance to individual pathogen species in case of multiple detections of facultative pathogenic microorganisms in primarily non-sterile sample materials. This is particularly the case in high-endemicity settings, where continuous exposition to respective microorganisms leads to immunological adaptation and semi-resistance while considerable disease would result in case of exposition of a non-adapted population. While biofilms in chronic wounds show higher pathogenic potential in case of multi-species composition, detection of multiple pathogens in respiratory samples is much more difficult to interpret and asymptomatic enteric colonization with facultative pathogenic microorganisms is frequently observed in high endemicity settings. For respiratory samples and stool samples, cycle-threshold-value-based semi-quantitative interpretation of qPCR results has been suggested. Etiological relevance is assumed if cycle-threshold values are low, suggesting high pathogen loads. Although the procedure is challenged by lacking standardization and methodical issues, first evaluations have led to promising results. Future studies should aim at generally acceptable quantitative cut-off values to allow discrimination of asymptomatic colonization from clinically relevant infection.

Should the patients colonized with extended-spectrum beta-lactamase-producing Gram-negative bacilli (E-GNB) coming to hospital from the community with pneumonia get anti-E-GNB active empirical treatment?

Extended-spectrum beta-lactamases are responsible for resistance of Gram-negative bacilli to several beta-lactam antibiotics, including those prescribed for treatment pneumonia. To evaluate the importance of colonization with E-GNB for the choice of empirical treatment we performed a retrospective case-control study including 156 patients, hospitalized for treatment of pneumonia from 2009 through 2013. Empirical treatment success and in-hospital survival were significantly lower in patients colonized with E-GNB compared to non-colonized (p = 0.002, p = 0.035). When comparing subgroups of colonized patients, treatment success was significantly lower in patients who were colonized with E-GNB resistant to empirical antibiotic (p = 0.010), but not in those colonized by E-GNB susceptible to empirically given antibiotic (p = 0.104). Difference in in-hospital mortality was insignificant in both subgroups (p = 0.056, p = 0.331). The results of study suggest that an anti-E-GNB active antibiotic should be used for empirical treatment of pneumonia in E-GNB colonized patients.