Multidrug-resistant Pseudomonas Aeruginosa Strains Research Articles

The impact of multi-drug resistant Pseudomonas aeruginosa infections on acute pancreatitis patients

IntroductionAcute pancreatitis (AP) accounts for a high proportion of digestive diseases worldwide and has a high risk of infection. Pseudomonas aeruginosa, a common pathogen of hospital infections, has been observed to increase the resistance rate to several antibiotics, causing difficulties in treatments. Our study aims to investigate the impact of the multi-drug resistant Pseudomonas aeruginosa (MDR-PA) infections on AP patients.MethodsAt two Chinese tertiary referral centers for AP patients infected with MDR-PA, a retrospective case-control study with a 1:2 case-control ratio was performed. Comparisons were preformed between with/without MDR-PA infections and different drug-resistance of MDR-PA infections patients, respectively. Independent risk factors of overall mortality were assessed via univariate and multivariate binary logistic regression analyses, and the distribution and antibiotic resistant rates of strains were described.ResultsMortality in AP patients with MDR-PA infections was significantly higher than in those without MDR-PA infections (7 (30.4%) vs. 4 (8.7%), P = 0.048). The rate of prophylactic use of carbapenem for 3 days (0 vs. 50%, P = 0.019) and the incidence rate of multiple organ failure (MOF) (0 vs. 57.1%, P = 0.018) were remarkably higher in the carbapenem-resistant Pseudomonas aeruginosa group compared with the carbapenem-sensitive Pseudomonas aeruginosa group. In the multivariate analysis, the severe categories of AP (OR = 13.624, 95% CIs = 1.567–118.491, P = 0.018) and MDR-PA infections (OR = 4.788, 95% CIs = 1.107–20.709, P = 0.036) were independent risk factors for mortality. The resistance rates of MDR-PA strains were low for amikacin (7.4%), tobramycin (3.7%), and gentamicin (18.5%). The resistance rates of MDR-PA strains to imipenem and meropenem were up to, 51.9% and 55.6%, respectively.ConclusionIn AP patients, severe categories of AP and MDR-PA infections were both independent risk factors for mortality. Inappropriate use of carbapenem antibiotics and MOF were related to carbapenem-resistant Pseudomonas aeruginosa infections. Amikacin, tobramycin, and gentamicin are recommended for the treatment of AP patients with MDR-PA infections.

Biochemical Characteristics and Antibiograms of Methicillin-Resistant Staphylococcus aureus and Multi-Drug Resistant Pseudomonas aeruginosa Isolated from Skin Wounds of Patients in a Tertiary-Level Hospital in Enugu, Nigeria

Infections by antibiotic-resistant pathogens are known to be the most challenging factor that can impair wound healing. Early detection and effective diagnosis contribute to appropriate therapeutic interventions, which significantly lead to successful treatment outcomes in non-healing wounds. The aim of this study was to identify and evaluate resistance patterns as well as characteristics of Methicillin Resistant Staphylococcus aureus (MRSA) and Multi-drug Resistant Pseudomonas aeruginosa (MDR-PA) isolated from skin wounds of patients in the National Orthopaedic Hospital, Enugu, Nigeria. Cultural and biochemical characterizations of the isolates were, therefore, carried out. Results of the biochemical tests confirmed the presence of Staphylococcus aureus and Pseudomonas aeruginosa isolates. Antibiotic disk diffusion method was adopted for antimicrobial susceptibility tests (ASTs) on the isolates. Based on inhibition zone diameters obtained, various degrees of resistance (50 ‒ 100 %) as well as susceptibility (40 ‒ 70 %) of the organisms were recorded against the test antibiotics. This showed that there was high prevalence of MRSA and MDR-PA strains among the wound pathogens in that part of the country. From the findings, it could be inferred that the occurrence of multi-drug resistant pathogens would contribute significantly to poor clinical responses to wound treatments with antibiotics.

Characterization of antibiotic resistance profiles in Pseudomonas aeruginosa isolates from burn patients

ObjectiveTo investigate the prevalence of multidrug-resistant (MDR) Pseudomonas aeruginosa (PA) producing extended-spectrum beta-lactamases (ESBLs) and metallo-beta-lactamases (MBLs) in burn patients in Algeria. MethodsBetween April 2016 and October 2019, 47 non-redundant isolates of PA were collected from 47 burn patients admitted to the Department of Burns at the Military Hospital of Algiers in Algeria. Antibiotic susceptibility testing was performed by agar diffusion and the Phoenix automated method. Resistance genes were identified by PCR, and molecular typing of isolates was carried out by enterobacterial repetitive intergenic consensus (ERIC) sequences-polymerase chain reaction (PCR). ResultsAmong the 47 non-redundant MDR PA strains isolated, 59.57% were phenotypically ESBLs-positive, and 100% were phenotypically MBL-positive. The ESBL-positive isolates were subsequently screened for six groups of bla genes encoding ESBL-type enzymes, namely blaCTX-M2, blaPER, blaTEM, blaSHV, blaVEB, and blaGES. Out of the 28 ESBL-producing strains, 23 (82.14%) were blaCTX-M2 positive; 18 (38.29%) were blaPER positive, and 16 (34.04%) were blaTEM positive, while 5 (17.9%) were co-harboring blaCTX-M2, blaTEM, and blaPER genes. The blaSHV, blaVEB, and blaGES genes were not detected in any of the ESBL positive isolates. Since all isolates were MBL-positive, all 47 strains were screened for the blaNDM-1, blaIMP, blaVIM genes that produce MBLs; however, none of these genes were detected. Additional screening for the oprD gene demonstrated that 45 (95.74%) of the isolates were positive for this gene. Finally, ERIC PCR revealed 11 distinct PA clones among the blaCTX-M2 positive strains. ConclusionThis is the first study to report the presence of CTX-M2-producing PA in the North Africa region and the first to detect blaCTX-M2-positive and blaPER-positive PA clinical isolates in Algeria, therefore demonstrating the spread of such MDR strains to this part of the world. Identification of bacterial genotypic alterations that confer antibiotic resistance is critical in determining the most effective antimicrobial strategies to be employed. Therefore, our findings could potentially facilitate clinical decision making regarding the antibiotics of choice for the treatment of burn patients that suffer from PA infections in Algeria.

840. First Report of Pseudomonas aeruginosa Isolates Harboring the CTX-M2 and PER genes in Algeria

BackgroundDespite significant improvements in burn care, multidrug-resistant (MDR) Pseudomonas aeruginosa (PA) remains one of the most common causes of life-threatening infections in patients suffering from thermal injuries. The objective of this study is to investigate the prevalence of MDR PA producing Extended-Spectrum Beta-lactamases (ESBLs) and metallo-beta-lactamases (MBLs) in burn patients in Algeria.MethodsBetween April 2016 and October 2019, 47 non-redundant isolates of PA were collected from 47 burn patients admitted to the Department of Burns at the Military Hospital of Algiers in Algeria. Antibiotic susceptibility testing was performed by agar diffusion and the Phoenix automated method. Resistance genes were identified by PCR, and molecular typing of isolates was carried out by enterobacterial repetitive intergenic consensus (ERIC) sequences-polymerase chain reaction (PCR).ResultsAmong the 47 non-redundant MDR PA strains isolated, 59.57% were phenotypically ESBLs-positive, and 100% were phenotypically MBL-positive. The ESBL-positive isolates were subsequently screened for five groups of bla genes encoding ESBL-type enzymes, namely CTX-M2, PER, TEM, SHV, VEB, and GES. Out of the 28 ESBL-producing strains, 23 (82.14%) were CTX-M2 positive; 18 (38.29%) were PER positive, and 16 (34.04%) were TEM positive, while 5 (17.9%) were co-harboring CTX-M2, TEM, and PER genes. The SHV, VEB, and GES genes were not detected in any of the ESBL positive isolates. Since all isolates were MBL-positive, all 47 strains were screened for the NDM-1, IMP, VIM genes that produce MBLs; however, none of these genes were detected. Additional screening for the OprD gene demonstrated that 45 (95.74%) of the isolates were positive for this gene. Finally, ERIC PCR revealed 6 distinct PA clones among the CTX-M2 positive strains.Table 1: Occurrence of beta-lactamase genes in relation to the antimicrobial susceptibility profiles of the PA isolates. ConclusionThis is the first report of CTX-M2-producing PA in the North Africa region and the first to detect CTX-M2-positive and PER-positive PA clinical isolates in Algeria, therefore demonstrating the spread of such MDR strains in this part of the world. Identification of genotypic alterations that confer antibiotic resistance is critical in determining effective antimicrobial strategies. Hence, these findings could potentially guide antibiotic choice decisions.World map with countries where PER- and CTX-M2-postive Pseudomonas aeruginosa isolates have been reported. Disclosures All Authors: No reported disclosures

Cathelicidin-Derived Synthetic Peptide Improves Therapeutic Potential of Vancomycin Against Pseudomonas aeruginosa.

Pseudomonas aeruginosa (PA) is the leading cause of corneal blindness worldwide. A constant increase in multi-drug resistant PA strains have heightened the challenge of effectively managing corneal infections with conventional antibiotics. Antimicrobial peptides are promising antibiotic analogs with a unique mode of action. Cathelicidin-derived shorter peptides (FK13 and FK16) have previously been shown to kill a range of pathogens in both in vitro and in vivo systems. Here, our aim was to exploit the potential of FK13 or FK16 to enhance the anti-Pseudomonas activity of vancomycin, which normally has low clinical efficacy against PA. Our results have demonstrated that FK16 is more potent than FK13 against different PA strains including a clinical isolate from a patient’s ocular surface. FK16 was shown to enhance the membrane permeability of PAO1 at sub-inhibitory concentrations. Moreover, FK16 at lower concentrations was shown to increase the antibacterial susceptibility of vancomycin against PA strains up to eightfold. The bactericidal synergism between FK16 and vancomycin was shown to be stable in the presence of physiological tear salt concentration and did not cause toxic effects on the human corneal epithelial cells and human red blood cells. Our results have revealed that sub-inhibitory concentration of FK16 could augment the antimicrobial effects of vancomycin against PA. It is anticipated that the future exploitation of the peptide design approach may enhance the effectiveness of FK16 and its application as an adjuvant to antibiotic therapy for the treatment of multi-drug resistant infections.

Anti-bacterial activity of mutant chensinin-1 peptide against multidrug-resistant Pseudomonas aeruginosa and its effects on biofilm-associated gene expression.

Nosocomial infections with Pseudomonas aeruginosa (PA) are difficult to treat due to the low outer membrane permeability of the bacterium and the development of resistance. In the present study, the anti-microbial peptide (AMP) mutant chensinin-1 (MC1) was revealed to exhibit anti-bacterial activity against a multidrug-resistant PA (MRPA) strain in vitro, and the minimum inhibitory concentration was 25 µM, which was 4-fold higher than that of the native strain. MC1 was able to disrupt the integrity of the cytoplasmic membrane in the native PA strain and MRPA and had a similar membrane depolarization ability in these strains, but the outer membrane permeability of MRPA cells was lower than that of native PA cells, as determined by a 1-N-phenylnaphthylamine assay. In addition, the abundance of the gene Psl encoding for biofilm-associated polysaccharides was detected using Congo red, and a high concentration of MC1 inhibited the formation of MRPA biofilms. Furthermore, the expression levels of biofilm-associated genes affected by the AMP, MC1, were quantified by polymerase chain reaction analysis. The results indicated that MC1 induced biofilm inhibition by downregulating the relative expression of specific biofilm polysaccharide-associated genes, including pelA, algD and pslA. The present results indicated that the AMP MC1 may be an effective antibiotic against MRPA strains.

Differential Effect of Newly Isolated Phages Belonging to PB1-Like, phiKZ-Like and LUZ24-Like Viruses against Multi-Drug Resistant Pseudomonas aeruginosa under Varying Growth Conditions.

In this study, we characterize three phages (SL1 SL2, and SL4), isolated from hospital sewage with lytic activity against clinical isolates of multi-drug resistant Pseudomonas aeruginosa (MDR-PA). The host spectrum ranged from 41% to 54%, with all three phages together covering 79% of all tested clinical isolates. Genome analysis revealed that SL1 (65,849 bp, 91 open reading frames ORFs) belongs to PB1-like viruses, SL2 (279,696 bp, 354 ORFs) to phiKZ-like viruses and SL4 (44,194 bp, 65 ORFs) to LUZ24-like viruses. Planktonic cells of four of five selected MDR-PA strains were suppressed by at least one phage with multiplicities of infection (MOIs) ranging from 1 to 10−6 for 16 h without apparent regrowth of bacterial populations. While SL2 was most potent in suppressing planktonic cultures the strongest anti-biofilm activity was observed with SL4. Phages were able to rescue bacteria-infected wax moth larvae (Galleria melonella) for 24 h, whereby highest survival rates (90%) were observed with SL1. Except for the biofilm experiments, the effect of a cocktail with all three phages was comparable to the action of the best phage alone; hence, there are no synergistic but also no antagonistic effects among phages. The use of a cocktail with these phages is therefore expedient for increasing host range and minimizing the development of phage resistance.

Control of Multidrug-Resistant Pseudomonas aeruginosa in Allogeneic Hematopoietic Stem Cell Transplant Recipients by a Novel Bundle Including Remodeling of Sanitary and Water Supply Systems.

Infections by multidrug-resistant Pseudomonas aeruginosa (MDRPa) are an important cause of morbidity and mortality in patients after allogeneic hematopoietic stem cell transplantation (HSCT). Humid environments can serve as a reservoir and source of infection by this pathogen. To minimize the risk of infection from these reservoirs, we performed extensive remodeling of sanitation and water installations as the focus of our hygiene bundle. During the reconstruction of our transplantation unit (April 2011-April 2014) we implemented several technical modifications to reduce environmental contamination by and subsequent spreading of MDRPa, including a newly designed shower drain, disinfecting siphons underneath the sinks, and rimless toilets. During a 3-year study period (2012-2014), we tracked the number of patients affected by MDRPa (colonized and/or infected) and the outcome of infected patients, and monitored the environmental occurrence of this pathogen. We further performed whole-genome sequencing of nosocomial MDRPa strains to evaluate genotypic relationships between isolates. Whereas 31 (9.2%; 18 colonized, 13 infected) patients were affected in 2012 and 2013, the number decreased to 3 in 2014 (17%; 3 colonized, 0 infected). Lethality by MDRPa similarly decreased from 3.6% to 0%. Environmental detection of MDRPa decreased in toilets from 18.9% in 2012-2013 to 6.1% in the following year and from 8.1% to 3.0%, respectively, in shower outlets. Whole-genome sequencing showed close relationships between environmental and patient-derived isolates. Hospital construction measures aimed at controlling environmental contamination by and spread of MDRPa are effective at minimizing the risk of highly lethal MDRPa infections.

Enhancement of antimicrobial activity by liposomal oleic acid-loaded antibiotics for the treatment of multidrug-resistant Pseudomonas aeruginosa

In this study, we examined the efficacy of liposomal oleic acid-based antibiotic formulations on 32 strains of multidrug-resistant Pseudomonas aeruginosa (MDRPa). The average size of liposomes were 93.12 ± 2.3 nm holding a negative zeta potential at −57.3 ± 0.89. Liposomal antibiotic formulations were tested against 32 MDRPa strains isolated from burn wounds and urine samples, which exhibited an MIC of ≤8 μg/mL, whereas MIC of free antibiotics ranged from 32 to >1024 μg/mL. The results clearly indicate that the liposomes composed of naturally occurring oleic acid, could be used therapeutically either alone or in combination with antibiotics to effectively treat P. aeruginosa infections.

Multidrug-resistant Pseudomonas aeruginosa infections pose growing threat to health care–associated infection control in the hospitals of Southern China: A case-control surveillance study

Multidrug-resistant Pseudomonas aeruginosa (MDRPA) is one of the most common agents among health care-associated infections. There is a lack of data on the clinical features of MDRPA from Southern China. A case-control surveillance study of P aeruginosa was conducted based on surveillance from July 2008-December 2012, in 5 hospitals of Guangzhou, China. Data were analyzed by univariate analysis and multivariate logistic regression using Stata 13 (StataCorp, College Station, TX). Of the 348 P aeruginosa strains, the prevalence of MDRPA was 54%, and it has increased over time. Isolates of P aeruginosa showed increased resistance to most antimicrobials during this time period. Independent risk factors were tracheal intubation insertion (odds ratio [OR], 2.21; 95% confidence interval [CI], 1.16-4.23; P = .02) and use of carbapenem (odds ratio [OR], 3.36; 95% confidence interval [CI], 1.75-6.47; P < .01). The distribution of MDRPA infections was uneven among the 5 hospitals (P = .01). Being infected with MDRPA strains resulted in longer duration of hospitalization (39 vs 24 days) and higher mortality (49% vs 20%). The infections of MDRPA were severe issues. More stringent measures should be applied for those with independent predictors of MDRPA infections because they may induce adverse clinical outcomes.

Clinical outcomes of multidrug resistant pseudomonas aeruginosa infection and the relationship with type III secretion system in patients with diabetic foot.

The objective was to analyze the clinical outcomes of multidrug resistant Pseudomonas aeruginosa (MDRPA) infection and determine the relationship between type III secretion system (TTSS) and MDRPA in diabetic foot (DF) patients. A total of 117 patients infected with P aeruginosa were recruited and grouped into MDRPA and non-MDRPA group according to antimicrobial susceptibility testing. TTSS genes were detected by polymerase chain reaction (PCR). Potential risk factors for MDRPA infection were examined using univariate and multivariate analyses. Clinical outcomes were compared on the basis of MDRPA or TTSS virulence gene. Previous antibiotic therapy, previous hospitalization and osteomyelitis were associated with MDRPA infection. MDRPA group had a higher amputation/toe rate (32.6% vs 16.2%) and lower healing rate (20.9% vs 41.9%) than non-MDRPA group (P = .032). A significantly higher proportion of exoU was present in MDRPA group (75.0% vs 25.0%, P < .05) than non-MDRPA group. Patients infected with exoU isolates had a lower healing rate and higher amputation/toe rate (25.0% vs 65.2%, 33.3% vs 8.7%, P < .05) than infected with exoS isolates. The exoU gene was predominance among MDRPA strains. The poor clinical outcomes of MDRPA infection in patients with DF were attributable to exoU gene.

Pseudomonas aeruginosa Ventilator-associated Pneumonia. Predictive Factors of Treatment Failure

The predictive factors of treatment failure for ventilator-associated pneumonia (VAP) caused by Pseudomonas aeruginosa (PA) remain uncertain. To describe PA-VAP recurrence prognosis and to identify associated risk factors in a large cohort of intensive care unit patients with PA-VAP. From the multicenter OUTCOMEREA database (1997-2011), PA-VAP onset and recurrence were recorded. All suspected cases of VAP were confirmed by a positive quantitative culture of a respiratory sample. Multidrug-resistant PA strains were defined by the resistance to two antibiotics among piperacillin, ceftazidime, imipenem, colistine, and fluoroquinolones (FQ). An extensively resistant PA was defined by resistance to piperacillin, ceftazidime, imipenem, and FQ. A treatment failure was defined as a PA-VAP recurrence or by the death occurrence. A total of 314 patients presented 393 PA-VAP. Failure occurred for 112 of them, including 79 recurrences. Susceptible, multidrug resistant, and extensively resistant PA represented 53.7%, 32%, and 14.3% of the samples, respectively. Factors associated with treatment failure were age (P = 0.02); presence of at least one chronic illness (P = 0.02); limitation of life support (P = 0.0004); a high Sepsis-Related Organ Failure Assessment score (P < 0.0001); PA bacteremia (P = 0.003); and previous use of FQ before the first PA-VAP (P = 0.0007). The failure risk was not influenced by the strain resistance profile or by the biantibiotic treatment, but decreased in case of VAP treatment that includes FQ (subdistribution hazard ratio, 0.5 [0.3-0.7]; P = 0.0006). However, the strain resistance profile slowed down the intensive care unit discharge hazard (subdistribution hazard ratio, 0.6 [0.4-1.0]; P = 0.048). Neither resistance profile nor biantibiotic therapy decreased the risk of PA-VAP treatment failure. However, the profile of PA resistance prolonged the length of stay. Better evaluation of the potential benefit of an initial treatment containing FQ requires further randomized trials.

In vitro and in vivo properties of a fully human IgG1 monoclonal antibody that combats multidrug resistant Pseudomonas aeruginosa

The development of an anti-bacterial drug in the form of a monoclonal antibody (mAb) targeting an exposed virulence factor, represents an innovative therapeutic strategy. Consequently, a fully human IgG1 mAb (LST-007) targeting Pseudomonas aeruginosa (PA) flagellin type b was recombinantly expressed and characterized in vitro and in an infection model driven by a multidrug resistant (MDR) PA strain. LST-007 demonstrated a highly specific binding towards whole PA bacteria harboring flagellin type b and its recombinant counterpart, with a KD of 7.4×10−10 M. In bioactivity assays, LST-007 or titers of Cmax sera derived from pharmacokinetic studies, markedly attenuated PA motility in an equipotent manner. In vivo, parenteral LST-007 (20 mg/kg) given as a single or double-dosing paradigm post-infection, afforded survival (up to 75% at Day 7) in a lethal model of pneumonia driven by the intratracheal (i.t.) instillation of an LD80 of the MDR PA isolate. This protective effect was markedly superior to that of imipenem (30% survival at Day 7) and totally devoid with an irrelevant, human isotype mAb. These data lay credence that LST-007 may be a valuable adjunct to the limited list of anti-bacterials that can tackle MDR PA strains, thereby warranting its continued development for eventual clinical evaluation.

Multidrug resistant and sensitive strains of Pseudomonas aeruginosa: Establishing clonal relationship by Pulsed Field Gel Electrophoresis and in vitro antibiotic synergy testing by E test

Background: The emergence of multidrug resistant Pseudomonas aeruginosa (MDRPA) as one of the leading nosocomial pathogens imposes a serious health threat due to limited antibiotic options. In this study, a sample of clonally distinct MDRPA and sensitive strains of Pseudomonas aeruginosa (SSPA) were tested against various antibiotics combinations to establish synergistic activity against these strains. Methods: A total of 39 retrospectively collected MDRPA strains isolated over three years with a particular antibiogram (sensitive to colistin but resistant to ceftazidime, cefepime, cefoperazone, cefoperazone/sulbactam , ciprofloxacin, imipenem, meropenem, piperacillin, piperacillintazobactam, gentamicin, netilmicin, with varying susceptibility to amikacin) and 19 SSPA collected prospectively were genotyped using Spe1 DNA macrorestriction analysis and pulsedfield gel electrophoresis (PFGE). The strains were from different patients from various sites (blood, tissue, fluid, catheter tip, bronchiol alveolar lavage (BAL), urine, sputum, swab, tracheal secretion and nasal swab). Clonal relatedness was determined at �85% level of similarity and grouped into different clusters. A representative strain from each cluster was tested against 10 different paired combinations of various antimicrobials (�-lactams, quinolone, aminoglycoside, tigecycline, rifampicin and colistin) to establish synergistic activity against these strains using the investigational E test fixed ratio method. Results: There were 46 distinct clones out of a total of 58 MDRPA and SSPA resolved by PFGE from which 10 clonally distinct strains (8 MDRPA and 2 SSPA strains) were selected for synergy testing. The antibiotic combination which most frequently demonstrated synergy was cefepime with amikacin (4/10 strains). Other synergistic combinations were aztreonam with either ceftazidime or cefepime, and meropenem with ciprofloxacin (3/10 strains respectively), ceftazidime with either ciprofloxacin or amikacin (2/10 strains respectively) and imipenem with ciprofloxacin (1/10 strains). The combination of ceftazidime with amikacin was antagonistic in 1/10 strains. The other antibiotics combinations were either additive or indifferent. Conclusion: PFGE was a useful and discriminative molecular subtyping tool to establish clonal relatedness among strains. Results of antimicrobial synergy testing indicate that although certain combinations may act synergistically, it was still strain dependent. These preliminary findings require further confirmation with testing of a larger number of isolates.

Multiresistant Pseudomonal Respiratory Infection in Intensive Care Unit Patients

In Brief The objective of this review is to describe intensive care unit (ICU)-acquired infections caused by multidrug-resistant Pseudomonas aeruginosa (MDRPA). P aeruginosa is a saprophytic microorganism characterized by its natural resistance to many β-lactam antibiotics. In addition, it readily acquires resistance to most or even all antipseudomonal agents, defining MDRPA strains. These strains are responsible for nosocomial outbreaks or sporadic, not epidemiologically linked cases. They are encountered worldwide but their proportions depend on the criteria defining them. According to US data, 16% of isolates are resistant to ≥3 of the core antipseudomonal antimicrobials. Ventilator-associated pneumonia is one of the main MDRPA infections in the ICU. Recent previous use of antibiotics with high antipseudomonal activity is a key factor for the emergence of MDRPA. MDRPA infections occur in critically ill patients with multiple comorbidities after long periods of hospitalization. When other severity factors are taken into account and when the initial treatment is appropriate, MDRPA strains are probably no more pathogenic than drug-susceptible strains, as suggested by equivalent mortality rates. The treatment of patients with MDRPA pulmonary infection is a difficult challenge, and some therapeutic modalities, such as aerosolized colistin, warrant evaluation. A strict antibiotic prescription policy and hygiene measures are the cornerstones of prevention. Multidrug-resistant Pseudomonas aeruginosa is one more warning sign of spreading antimicrobial resistance. These strains are responsible for nosocomial pneumonia in critically ill ICU patients. Among risk factors, previous use of broad-spectrum antibiotics appears to be a key factor. Therapeutic approaches and preventive measures are reviewed.