Methicillin-resistant <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> bacteraemia and mortality in a teaching hospital

Methicillin-resistant Staphylococcus aureus (MRSA) is responsible for more than 40% of S. aureus bacteraemias in the UK and is associated with considerable morbidity and mortality. This retrospective audit examined the epidemiology of MRSA bacteraemia (MRSAB) at our institution, where the MRSAB rate has been high. A retrospective case note review was undertaken of all patients dying within 90 days of an episode of MRSAB during a 12-month period. A clinical panel classified deaths as having MRSAB as the main cause, contributing cause or having no bearing on the death. Sixty-two patients had one or more episodes of MRSAB and 30 died within 90 days. The mean age of those dying was 72 (43–96) years and of those surviving was 57 (21–87) years. MRSAB was judged to be the main or contributing cause of death in 24 cases, giving an associated mortality of 39%. All-cause mortality at 7, 30 and 90 days was 19, 40 and 48%, respectively. We investigated the minimum inhibitory contribution (MIC) to vancomycin for 79 MRSAB isolates, of which 70.8% of isolates had an MIC value of 2 mg/l. None of the isolates expressed heteroresistance to vancomycin. Five out of seven patients in whom MRSAB was the main cause of death had community onset of infection. It is unlikely that efforts to reduce delays in delivering effective antimicrobial therapy will have a major impact on mortality. Efforts to reduce the burden of MRSAB should focus on the primary prevention of bacteraemia.     

Methicillin-resistant <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> with <Emphasis Type="Italic">mecC</Emphasis>: a description of 45 human cases in southern Sweden

In 2011, a novel mecA gene homologue, mecC, was reported in isolates from both humans and dairy cattle. The epidemiology of mecC methicillin-resistant Staphylococcus aureus (MRSA) in humans is not yet well known. In this retrospective study, we present the epidemiology of human clinical cases with mecC MRSA detected in the southern part of Sweden during the period 2005–2014. A total of 45 patients with an isolate positive for mecC MRSA were included in the study. Twenty-six isolates were found before 2012 and were retrospectively tested for mecC. Nineteen isolates were detected in 2012–2014 through routine testing. Culture results, resistance patterns, Panton–Valentine leukocidin (PVL) genes, and spa types were collected from the Clinical Microbiology Laboratory. Epidemiological data were received from the database at the Regional Centre for Communicable Disease Control and the patient’s medical files. The majority of the patients with mecC MRSA were of Swedish origin, had underlying diseases, and lived in rural areas. The median age was 60 years. Of the mecC MRSA, 76 % belonged to spa types t373 and t843. The median minimum inhibitory concentration (MIC) value for oxacillin was 16 mg/L (1–64 mg/L) and only one isolate was resistant to other classes of antibiotics. The most common type of infection was skin and soft tissue infections, most often in an existing skin lesion. The patients with mecC MRSA were colonized for a short time and gave rise to few secondary cases. mecC MRSA in our region appears to have a domestic origin and mainly affects patients with underlying diseases or patients with an existing skin lesion. Our data indicate that it could be a poor colonizer.     

Rapid diagnosis of<Emphasis Type="Italic"> Staphylococcus aureus</Emphasis> bacteremia using <Emphasis Type="Italic">S. aureus</Emphasis> PNA FISH

In the study presented here, the performance of the S. aureus PNA FISH assay was evaluated using 285 blood cultures (from 104 patients) that had gram-positive cocci resembling staphylococci on Gram stain. The new molecular test is based on a fluorescence in situ hybridization assay using peptide nucleic acid probes targeting Staphylococcus aureus 16S rRNA and is designed for the rapid identification of Staphylococcus aureus directly from positive blood cultures. The sensitivity, specificity, and positive and negative predictive values of the S. aureus PNA FISH for the rapid identification of Staphylococcus aureus directly from positive blood culture bottles were 100, 99.4, 99.2 and 100%, respectively.     

Development of a vaccine against <Emphasis Type="Italic">Staphylococcus aureus</Emphasis>

A vaccine to prevent infections caused by Staphylococcus aureus would have a tremendously beneficial impact on public health. In contrast to typical encapsulated bacterial pathogens, such as Streptococcus pneumoniae, H. influenzae, and Neisseria meningitides, the capsule of S. aureus is not clearly linked to strain virulence in vivo. Furthermore, it is not clear that natural infection caused by S. aureus induces a protective humoral immune response, as does infection caused by typical encapsulated bacteria. Finally, pure B cell or antibody deficiency, in either animal models or in patients, does not predispose to more frequent or more severe S. aureus infections, as it does for infections caused by typical encapsulated bacteria. Rather, primary immune mechanisms necessary for protection against S. aureus infections include professional phagocytes and T lymphocytes (Th17 cells, in particular) which upregulate phagocytic activity. Thus, it is not clear whether an antibody-mediated neutralization of S. aureus virulence factors should be the goal of vaccination. Rather, the selection of antigenic targets which induce potent T cell immune responses that react to the broadest possible array of S. aureus strains should be the focus of antigen selection. Of particular promise is the potential to select antigens which induce both humoral and T cell-mediated immunity in order to generate immune synergy against S. aureus infections. A single-antigen vaccine may achieve this immune synergy. However, multivalent antigens may be more likely to induce both humoral and T cell immunity and to induce protection against a broader array of S. aureus isolates. A number of candidate vaccines are in development, raising the promise that effective vaccines against S. aureus will become available in the not-so-distant future. Possible development programs for such vaccines are discussed.     

Recurrent necrotizing fasciitis caused by methicillin-resistant <Emphasis Type="Italic">Staphylococcus aureus</Emphasis>

Reported here is a rare case of recurrent necrotizing fasciitis due to methicillin-resistant Staphylococcus aureus (MRSA). A 46-year-old female with poorly controlled diabetes and chronic ingestion of steroid-containing medications was admitted for treatment of necrotizing fasciitis of the right thigh. Three months following hospital discharge she was readmitted with necrotizing fasciitis of the left hand. On both occasions, MRSA was isolated from tissue cultures obtained during surgical debridement. Patients who develop necrotizing fasciitis are predisposed to severe soft tissue infections due to associated comorbid conditions such as diabetes mellitus. Recurrent soft tissue infection in a patient with previous MRSA-related necrotizing fasciitis should therefore be treated with a high index of suspicion.     

CC398 <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> subpopulations in Belgian patients

Studies based on genome-wide single nucleotide polymorphisms (SNPs) supported the existence of two subpopulations in clonal complex (CC) 398 Staphylococcus aureus: an ancestral human-adapted clade (HC) and an animal-associated clade (AC). In this study, we have investigated the occurrence of genetic markers that allow discrimination of these subpopulations among CC398 isolates collected during 2014 to 2016 from human patients in Belgium. A collection of isolates was investigated by means of spa-typing and 16S-mecA-nuc PCR. CC398 isolates were classified as belonging to the human or the animal clade by using a canonical SNPs PCR and further studied by antimicrobial susceptibility and the presence of toxins, immune evasion cluster (IEC), and resistance genes. A total of 124 (7.8%) human isolates belonged to CC398. They were grouped into HC (n?=?58) or AC (n?=?66). The genes erm(T), pvl, chp, and scn were predominantly found in HC-CC398, while AC-CC398 isolates carried more frequently than the mecA, erm(C), tet(K), tet(M), and tet(L) genes. Different combinations of gene profiles were observed according to the clade. CC398 isolates from Belgian patients belonged to different subpopulations including typical HC and AC-isolates. Few HC-strains with mecA and AC-isolates harboring IEC were found. CC398 isolates from Belgian patients belonged to different subpopulations including typical HC and AC-isolates, as well as new emerging subpopulations that underline the ability of this lineage to acquire resistance and virulence genes. Further research is needed to evaluate the emergence of these subpopulations in the clinical setting.     

Dalbavancin reduces biofilms of methicillin-resistant <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> (MRSA) and methicillin-resistant <Emphasis Type="Italic">Staphylococcus epidermidis</Emphasis> (MRSE)

Activity of dalbavancin against methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus epidermidis (MRSE) in biofilm was investigated and the microbicidal biofilm concentrations (MBC) were determined. Biofilms obtained from ten MRSA and ten MRSE bloodstream isolates, collected from patients in the General Hospital of Vienna between 2012 and 2015, were incubated with dalbavancin in trypticase soy broth (TSB) in serial dilution from 0.0625 mg/l to 256 mg/l using a microtiter plate biofilm model. The plates were incubated for 24 h at 37 ° C and 50% humidity. Biofilms were fixed with 2.5% glutaraldehyde and stained with crystal violet. Subsequently the optical density (OD₆₂₀) was used to measure the MBC, defined as the concentration of dalbavancin leading to a 50% reduction of biofilm. MBC for MRSA was 1 mg/l–4 mg/l (minimal inhibitory concentrations (MIC) 0.0312 mg/l–0.064 mg/l). MBC for MRSE was 2 mg/l–16 mg/l (MIC 0.023 mg/l–0.0625 mg/l). Dalbavancin successfully reduced MRSA and MRSE in biofilms, and therefore provides a promising option for the treatment of biofilm-associated infections.     

The remarkably multifunctional fibronectin binding proteins of <Emphasis Type="Italic">Staphylococcus aureus</Emphasis>

Staphylococcus aureus expresses two distinct but closely related multifunctional cell wall-anchored (CWA) proteins that bind to the host glycoprotein fibronectin. The fibronectin binding proteins FnBPA and FnBPB comprise two distinct domains. The C-terminal domain comprises a tandem array of repeats that bind to the N-terminal type I modules of fibronectin by the tandem β-zipper mechanism. This causes allosteric activation of a cryptic integrin binding domain, allowing fibronectin to act as a bridge between bacterial cells and the α₅β₁ integrin on host cells, triggering bacterial uptake by endocytosis. Variants of FnBPA with polymorphisms in fibronectin binding repeats (FnBRs) that increase affinity for the ligand are associated with strains that infect cardiac devices and cause endocarditis, suggesting that binding affinity is particularly important in intravascular infections. The N-terminal A domains of FnBPA and FnBPB have diverged into seven antigenically distinct isoforms. Each binds fibrinogen by the ‘dock, lock and latch’ mechanism characteristic of clumping factor A. However, FnBPs can also bind to elastin, which is probably important in adhesion to connective tissue in vivo. In addition, they can capture plasminogen from plasma, which can be activated to plasmin by host and bacterial plasminogen activators. The bacterial cells become armed with a host protease which destroys opsonins, contributing to immune evasion and promotes spreading during skin infection. Finally, some methicillin-resistant S. aureus (MRSA) strains form biofilm that depends on the elaboration of FnBPs rather than polysaccharide. The A domains of the FnBPs can interact homophilically, allowing cells to bind together as the biofilm accumulates.     

Risk factors for long-term mortality of <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> bacteremia

Staphylococcus aureus bacteremia (SAB) is a fatal disease. We aimed to describe risk factors for long-term mortality with SAB. We analyzed data from a retrospectively collected database including 1,692 patients with SAB. We considered variables of infection and background conditions for the analysis of long-term survival. The Kaplan–Meier procedure was used for analysis of long-term survival. Variables significantly associated with mortality were analyzed using a Cox regression model. We included 1,692 patients in the analysis. Patients were followed for up to 22 years. Within one year, 62% of patients died and within 5 years 72% died. A total of 82% of patients aged 65 years and older died within 5 years. Independent predictors of long-term mortality were older age (Hazard ratio 1.029, 95% confidence interval 1.022–1.036), female gender (HR 1.302, 95% CI 1.118–1.517), pneumonia or primary/ unknown source of infection (HR 1.441, 95% CI 1.230–1.689), dementia (HR 1.234, 95% CI 1.004–1.516), higher Charlson score (HR 1.155, 95% CI 1.115–1.196), shock at onset (HR 1.776, 95% CI 1.430–2.207) and arrival to hospitalization from an institution (HR 1.319, 95% CI 1.095–1.563). Long-term survival of patients older than 65 years and of women with SAB is severely curtailed.     

<Emphasis Type="Italic">Staphylococcus aureus</Emphasis> colonization related to severity of hand eczema

Knowledge on Staphylococcus aureus colonization rates and epidemiology in hand eczema is limited. The aim of this study was to clarify some of these issues. Samples were collected by the “glove juice” method from the hands of 59 patients with chronic hand eczema and 24 healthy individuals. Swab samples were taken from anterior nares and throat from 43 of the 59 patients and all healthy individuals. S. aureus were spa typed and analysed by DNA-microarray-based genotyping. The extent of the eczema was evaluated by the hand eczema extent score (HEES). The colonization rate was higher on the hands of hand eczema patients (69 %) compared to healthy individuals (21 %, p?<?0.001). This was also seen for bacterial density (p?=?0.002). Patients with severe hand eczema (HEES?≥?13) had a significantly higher S. aureus density on their hands compared to those with milder eczema (HEES?=?1 to 12, p?=?0.004). There was no difference between patients and healthy individuals regarding colonization rates in anterior nares or throat. spa typing and DNA-microarray-based genotyping indicated certain types more prone to colonize eczematous skin. Simultaneous colonization, in one individual, with S. aureus of different types, was identified in 60–85 % of the study subjects. The colonization rate and density indicate a need for effective treatment of eczema and may have an impact on infection control in healthcare.     

Methicillin-resistant versus methicillin-sensitive <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> infective endocarditis

The incidence of methicillin-resistant Staphylococcus aureus (MRSA) infective endocarditis (IE) is increasing. This study compared clinical characteristics and mortality in patients with methicillin-sensitive S. aureus (MSSA) IE versus MRSA IE, based on a prospectively collected series of 72 consecutive patients with definite S. aureus IE according to the modified Duke criteria between June 2000 and December 2006. Sixteen of 72 IE patients (22%) were caused by MRSA. Nosocomial origin, surgical site infection, surgery in the previous 6 months, the presence of a catheter and persistent bacteremia were significantly associated with MRSA. MSSA patients had significantly more unknown origin of bacteremia and experienced a significantly higher rate of major embolism than MRSA patients. MSSA patients underwent more frequently combined surgical and antimicrobial therapy, and MRSA patients were treated more frequently with antimicrobial therapy due to a contraindication to surgery. The 6-month mortality was higher in patients with MRSA than MSSA. In the MSSA group treated with antimicrobial therapy without an indication to surgery, all patients survived, and in the combined surgical and antimicrobial group 29% died. The mortality in MRSA patients was lowest if combined surgical and antimicrobial therapy was performed. Both in MSSA and MRSA patients with antimicrobial therapy due to a contraindication to surgery, the mortality was extremely high. These data suggest that in S. aureus IE patients with a nosocomial origin, the presence of a catheter or recent surgery, initial therapy should include antimicrobial agents active against MRSA. Antimicrobial therapy alone with close monitoring of the therapeutic effect and signs of complicated course is an acceptable approach in selected patients with MSSA IE. Denial of surgery because of local or general factors in patients that meet criteria for surgical intervention in acute IE is prognostically ominous.     

Low occurrence of the new species <Emphasis Type="Italic">Staphylococcus argenteus</Emphasis> in a <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> collection of human isolates from Belgium

Staphylococcus argenteus is a novel Staphylococcus species closely related to Staphylococcus aureus that has been recently described. In this study, we investigated the proportion and the characteristics of S. argenteus recovered from humans in Belgium. S. aureus. human isolates collected in Belgium from 2006 to 2015 (n?=?1,903) were retrospectively characterised via the presence of non-pigmented colonies on chocolate agar, spa typing and rpoB sequencing to determine if some of them were in fact S. argenteus. Out of 73 strains non-pigmented on chocolate plates, 3 isolates (0.16 %) showed rpoB sequences, in addition to spa and sequence types (ST2250/t5787, ST2250/t6675, ST3240/t6675), related to S. argenteus. Two of them were methicillin-resistant, harbouring a SCCmec type IV. The three S. argenteus isolates carried genes (sak, scn) of the immune evasion cluster. This first Belgian nationwide analysis showed a low occurrence of S. argenteus. Further studies should be conducted to identify the distribution range and the clinical impact of this new species.     

Innate and adaptive immune responses against <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> skin infections

Staphylococcus aureus is an important human pathogen that is responsible for the vast majority of bacterial skin and soft tissue infections in humans. S. aureus can also become more invasive and cause life-threatening infections such as bacteremia, pneumonia, abscesses of various organs, meningitis, osteomyelitis, endocarditis, and sepsis. These infections represent a major public health threat due to the enormous numbers of these infections and the widespread emergence of methicillin-resistant S. aureus (MRSA) strains. MSRA is endemic in hospitals worldwide and is rapidly spreading throughout the normal human population in the community. The increasing frequency of MRSA infections has complicated treatment as these strains are more virulent and are increasingly becoming resistant to multiple different classes of antibiotics. The important role of the immune response against S. aureus infections cannot be overemphasized as humans with certain genetic and acquired immunodeficiency disorders are at an increased risk for infection. Understanding the cutaneous immune responses against S. aureus is essential as most of these infections occur or originate from a site of infection or colonization of the skin and mucosa. This review will summarize the innate immune responses against S. aureus skin infections, including antimicrobial peptides that have direct antimicrobial activity against S. aureus as well as pattern recognition receptors and proinflammatory cytokines that promote neutrophil abscess formation in the skin, which is required for bacterial clearance. Finally, we will discuss the recent discoveries involving IL-17-mediated responses, which provide a key link between cutaneous innate and adaptive immune responses against S. aureus skin infections.     

Infant colonization by <Emphasis Type="Italic">Staphylococcus aureus</Emphasis>: role of maternal carriage

Infant colonization by Staphylococcus aureus has not been adequately investigated. In this study, we aimed to define determinants associated with the carriage of S. aureus in early infancy. Serial nasal swabs were collected from 128 infants and their mothers at months 0, 6, and 12 postpartum. S. aureus isolates were characterized by pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), spa typing, and the presence of chromosomal mecA and of Panton–Valentine leukocidin (PVL) genes. S. aureus was isolated in 17.7% and 15.7% of swabs from infants and mothers, respectively. Carriage rates were higher in infants with carrier mothers, non-smoking mothers, and many siblings. Persistent carriage rates were higher in infants with carrier or non-smoking mothers. S. aureus typing revealed identical strains in 10/15 investigated infant–mother pairs. Among 19 investigated S. aureus isolates from infants, ten harbored mecA and two harbored PVL genes, and these determinants were concomitantly present in isolates from mothers. Resistance to methicillin was 43.6% among all isolates from infants. In conclusion, isolates from infants were commonly identical to isolates from their mothers, pointing to a principal role of maternal carriage in S. aureus colonization in infants.     

Metal ion acquisition in <Emphasis Type="Italic">Staphylococcus aureus</Emphasis>: overcoming nutritional immunity

Transition metals are essential nutrients to virtually all forms of life, including bacterial pathogens. In Staphylococcus aureus, metal ions participate in diverse biochemical processes such as metabolism, DNA synthesis, regulation of virulence factors, and defense against oxidative stress. As an innate immune response to bacterial infection, vertebrate hosts sequester transition metals in a process that has been termed “nutritional immunity.” To successfully infect vertebrates, S. aureus must overcome host sequestration of these critical nutrients. The objective of this review is to outline the current knowledge of staphylococcal metal ion acquisition systems, as well as to define the host mechanisms of nutritional immunity during staphylococcal infection.     

Identification of bacteriophage types and their carriage in <Emphasis Type="Italic">Staphylococcus aureus</Emphasis>

Summary. Conserved genomic sequences distinctive of Staphylococcus aureus phage types 3A, 11, 77, 187 and Twort, representative of phage serogroups A, B, F, L and D, were identified and characterized. PCR primers designed for the above sequences were used for development of a multiplex PCR assay which enabled us not only to classify all phages of the International Typing Set plus 16 additional phages, but also to detect prophages in S. aureus genomes. One to four different prophages were unambiguously detected in experimentally lysogenized S. aureus strains, and substantial variation in prophage content was found in 176 S. aureus clinical strains of different provenance. In addition, by using a comparative genomics approach, all the prophages in the S. aureus genomes sequenced to date could be revealed and classified.     

Humoral immune consequences of <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> ST239-associated bacteremia

The humoral immune responses against 46 different staphylococcal antigens in 27 bacteremia patients infected by clonally related methicillin-resistant Staphylococcus aureus (MRSA) strains of a single sequence type (ST) 239 were investigated. A group of non-infected patients (n = 31) hospitalized for different reasons served as controls. All strains were confirmed as ST 239 by S. aureus and mecA-specific PCR, spa, and multi-locus sequence typing (MLST). In each bacteremia patient, a unique pattern of S. aureus antigen-specific immune responses after infection was observed. Antibody levels among bacteremia patients were significantly higher than controls for HlgB (P = 0.001), LukD (P = 0.009), LukF (P = 0.0001), SEA (P = 0.0001), SEB (P = 0.011), SEC (P = 0.010), SEQ (P = 0.049), IsaA (P = 0.043), IsdA (P = 0.038), IsdH (P = 0.01), SdrD (P = 0.001), SdrE (P = 0.046), EsxA (P = 0.0001), and SA0104 (P = 0.0001). On the other hand, the antibody levels were significantly higher among controls for SSL3 (P = 0.009), SSL9 (P = 0.002), and SSL10 (P = 0.007) when the IgG level on the day of infection was compared with that measured on the day of admission. Diversity was observed in the immune response against the antigens. However, a set of antigens (IsaA, IsdA, IsdH, SdrD, and HlgB) triggered a similar type of immune response in different individuals. We suggest that these antigens could be considered when developing a multi-component (passive) vaccine. SEA and/or its specific antibodies seem to play a critical role during ST239 MRSA bacteremia and SEA-targeted therapy may be a strategy to be considered.     

Clinical features and treatment outcomes of vancomycin-intermediate <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> (VISA) and heteroresistant vancomycin-intermediate <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> (hVISA) in a tertiary care institution in Singapore

This retrospective case–control study was undertaken to review the clinical features associated with heteroresistant vancomycin-intermediate Staphylococcus aureus (hVISA) and vancomycin-intermediate S. aureus (VISA) infections and the local impact they have on clinical outcome. Compared with vancomycin-susceptible S. aureus (n = 30), hVISA and VISA infections (n = 10) are found to be associated with a longer period of prior glycopeptide use (P = 0.01), bone/joint (P < 0.01) and prosthetic infections (P = 0.04), as well as treatment failure, as evidenced by longer bacteremic (P < 0.01) and culture positivity (P < 0.01) periods. This was observed to have resulted in longer hospital length of stay (P < 0.01) and total antibiotic therapy duration (P = 0.01). There was, however, no significant difference in the overall patient mortality or the hospitalization cost (P = 0.12) in both groups. Clinicians should be cognizant of the association between hVISA/VISA with high bacterial load deep-seated infections. We recommend targeted and even universal screening for hVISA/VISA in methicillin-resistant S. aureus (MRSA) infections.     

<Emphasis Type="Italic">Staphylococcus aureus</Emphasis> and <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> co-infection is associated with cystic fibrosis-related diabetes and poor clinical outcomes

Cystic fibrosis-related diabetes (CFRD) patients suffer from accelerated rates of pulmonary decline compared to cystic fibrosis (CF) patients with normal glucose tolerance (NGT). However, the mechanisms underlying this difference are unknown. While CFRD is associated with increased respiratory infections, a link between infection and enhanced pulmonary dysfunction remains unclear. The development of glucose intolerance is spectral, resulting in impaired glucose tolerance (IGT) prior to the diagnosis of CFRD. Inclusion of IGT patients within the NGT group may diminish the ability to identify correlations with CFRD. With this in mind, this study aimed to determine if the association between CFRD and respiratory infections is correlated with pulmonary decline. Respiratory cultures from 234 CF patients with confirmed diagnosis of NGT or CFRD were analyzed to measure rates of infection, focusing on the two most prevalent bacteria in CF, Staphylococcus aureus and Pseudomonas aeruginosa. Infection status was correlated with pulmonary function and confounding clinical variables including age, gender, blood glucose levels, and CF transmembrane conductance regulator (CFTR) phenotype were considered in multivariate analyses. CFRD patients, particularly those with extremely high blood glucose levels, were more likely than NGT patients to be co-infected with S. aureus and P. aeruginosa, compared to infection with only one pathogen. Co-infection was associated with decreased lung function and increased frequency of pulmonary exacerbations, even after adjustment for confounding variables. Alterations in the microbial community composition, as opposed to the presence of a single pathogen, may account for greater pulmonary decline in CFRD patients.