Human Campylobacter spp. infections in Italy.

PURPOSE: Campylobacter is a frequent cause of enteric infections with common antimicrobial resistance issues. The most recent reports of campylobacteriosis in Italy include data from 2013 to 2016. We aimed to provide national epidemiological and microbiological data on human Campylobacter infections in Italy during the period 2017-2021. METHODS: Data was collected from 19 Hospitals in 13 Italian Regions. Bacterial identification was performed by mass spectrometry. Antibiograms were determined with Etest or Kirby-Bauer (EUCAST criteria). RESULTS: In total, 5419 isolations of Campylobacter spp. were performed. The most common species were C. jejuni (n = 4535, 83.7%), followed by C. coli (n = 732, 13.5%) and C. fetus (n = 34, 0.6%). The mean age of patients was 34.61 years and 57.1% were males. Outpatients accounted for 54% of the cases detected. Campylobacter were isolated from faeces in 97.3% of cases and in 2.7% from blood. C. fetus was mostly isolated from blood (88.2% of cases). We tested for antimicrobial susceptibility 4627 isolates (85.4%). Resistance to ciprofloxacin and tetracyclines was 75.5% and 54.8%, respectively; resistance to erythromycin was 4.8%; clarithromycin 2% and azithromycin 2%. 50% of C. jejuni and C. coli were resistant to ≥ 2 antibiotics. Over the study period, resistance to ciprofloxacin and tetracyclines significantly decreased (p < 0.005), while resistance to macrolides remained stable. CONCLUSION: Campylobacter resistance to fluoroquinolones and tetracyclines in Italy is decreasing but is still high, while macrolides retain good activity.

New Antimicrobials for Gram-Positive Sustained Infections: A Comprehensive Guide for Clinicians.

Antibiotic resistance is a public health problem with increasingly alarming data being reported. Gram-positive bacteria are among the protagonists of severe nosocomial and community infections. The objective of this review is to conduct an extensive examination of emerging treatments for Gram-positive infections including ceftobiprole, ceftaroline, dalbavancin, oritavancin, omadacycline, tedizolid, and delafloxacin. From a methodological standpoint, a comprehensive analysis on clinical trials, molecular structure, mechanism of action, microbiological targeting, clinical use, pharmacokinetic/pharmacodynamic features, and potential for therapeutic drug monitoring will be addressed. Each antibiotic paragraph is divided into specialized microbiological, clinical, and pharmacological sections, including detailed and appropriate tables. A better understanding of the latest promising advances in the field of therapeutic options could lead to the development of a better approach in managing antimicrobial therapy for multidrug-resistant Gram-positive pathogens, which increasingly needs to be better stratified and targeted.

Diagnosis and management of infections caused by multidrug-resistant bacteria: guideline endorsed by the Italian Society of Infection and Tropical Diseases (SIMIT), the Italian Society of Anti-Infective Therapy (SITA), the Italian Group for Antimicrobial Stewardship (GISA), the Italian Association of Clinical Microbiologists (AMCLI) and the Italian Society of Microbiology (SIM).

Management of patients with infections caused by multidrug-resistant organisms is challenging and requires a multidisciplinary approach to achieve successful clinical outcomes. The aim of this paper is to provide recommendations for the diagnosis and optimal management of these infections, with a focus on targeted antibiotic therapy. The document was produced by a panel of experts nominated by the five endorsing Italian societies, namely the Italian Association of Clinical Microbiologists (AMCLI), the Italian Group for Antimicrobial Stewardship (GISA), the Italian Society of Microbiology (SIM), the Italian Society of Infectious and Tropical Diseases (SIMIT) and the Italian Society of Anti-Infective Therapy (SITA). Population, Intervention, Comparison and Outcomes (PICO) questions about microbiological diagnosis, pharmacological strategies and targeted antibiotic therapy were addressed for the following pathogens: carbapenem-resistant Enterobacterales; carbapenem-resistant Pseudomonas aeruginosa; carbapenem-resistant Acinetobacter baumannii; and methicillin-resistant Staphylococcus aureus. A systematic review of the literature published from January 2011 to November 2020 was guided by the PICO strategy. As data from randomised controlled trials (RCTs) were expected to be limited, observational studies were also reviewed. The certainty of evidence was classified using the GRADE approach. Recommendations were classified as strong or conditional. Detailed recommendations were formulated for each pathogen. The majority of available RCTs have serious risk of bias, and many observational studies have several limitations, including small sample size, retrospective design and presence of confounders. Thus, some recommendations are based on low or very-low certainty of evidence. Importantly, these recommendations should be continually updated to reflect emerging evidence from clinical studies and real-world experience.

Multicenter prospective study on the prevalence of colistin resistance in Escherichia coli: relevance of mcr-1-positive clinical isolates in Lombardy, Northern Italy.

BACKGROUND: The emergence of the plasmid-mediated colistin resistance mechanism in Escherichia coli has raised concern among public health experts as colistin is a last-line antimicrobial resort. The primary aim of the study was to investigate the prevalence of this resistance trait in E. coli isolates circulating in the Lombardy region, Northern Italy. The presence of mcr-type genes and their genetic relationship were also studied. MATERIALS AND METHODS: A prospective study was performed during a 4-month period (May to August, 2016) in six acute care Hospitals. Consecutive nonduplicate clinical isolates of E. coli from any type of clinical specimen, with the exception of rectal swabs, were included in the study. Isolates that exhibited MIC values for colistin >2 mg/L were further investigated. Bacterial identification was obtained by matrix-assisted laser desorption ionization-time of flight mass spectrometry. Amplification of mcr-type genes (-1 to -5 variants) and microarray analysis were accomplished. Repetitive sequence-based PCR (Rep-PCR) and multilocus sequence typing (MLST) analysis were used for genotyping. RESULTS: Overall, 3,902 consecutive E. coli isolates (2,342 from outpatients, 1,560 from inpatients) were evaluated during the study period. Of them, 18/3,902 (0.5%), collected from 4/6 centers, showed resistance to colistin. These isolates were mostly obtained from urine of both outpatients (n=12) and inpatients (n=6). Colistin MIC values ranged from 4 to 8 mg/L. The mcr-1 gene was detected in 10/18 isolates (7 from outpatients, 3 from inpatients). Rep-PCR and MLST analysis revealed the presence of nine different clusters. Further mcr-type genes were not detected. CONCLUSION: Resistance to colistin in E. coli clinical isolates appears low in our geographic area. With regard to mcr-1-positive isolates, they accounted for approximately 50% of colistin-resistant E. coli isolates, thus representing a relevant resistance mechanism in this context. Although overall limited, the presence of mcr-1 determinant in our region should not be ignored and great concern should be given to the continuous surveillance.

Emergence of Invasive Haemophilus influenzae Type A Disease in Italy.

We report on the first detection of 2 cases of invasive Haemophilus influenzae type a (Hia) disease in Italy. The cases were sustained by the same Hia "strain" belonging to the ST23 clone that has previously been reported only outside Europe. The emergence of invasive Hia disease is of concern.

[Strongyloidiasis in nephrologic patients]. / Strongiloidosi: la cenerentola delle parassitosi. due casi emblematici in pazienti nefrologici.

Strongyloides stercoralis is a nematode causing strongyloidiasis, more frequent in immigrants and in travelers coming from tropical and subtropical areas. Infection is usually asymptomatic, frequently associated with eosinophilia. Immunocompromised patients are at high risk of developing hyperinfection syndrome (HI) or dissemination (SD), life threatening complications. Diagnosis of strongyloidiasis is firstly based on larvae isolation in stool samples; specific therapy involves the use of ivermectin as first choice and albendazole as second choice. We describe two cases of strongyloidiasis. The first one is a disseminated strongyloidiasis occurred in an Ecuadorian male on corticosteroid therapy for nephrotic syndrome due to focal segmental glomerulosclerosis, successfully treated with ivermectin; the second one involves another Ecuadorian male affected by acute kidney failure and nephrotic syndrome in IgA nephropathy with a diagnosis of chronic strongyloidiasis performed before starting the immunosuppressive treatment. The timing of treatment with ivermectin has allowed the complete eradication of the parasite before starting steroid and mycophenolate mofetil therapy, preventing the occurrence of a disseminated infection. Epidemiological data show us how strongyloidiasis is rising at our latitude because of increased number of migrants and travelers coming from endemic areas. So we must always exclude asymptomatic strongyloidiasis before prescribing a steroid or immunosuppressive therapy, in order to avoid developement of disseminated and often fatal disease.

Evaluation of brilliance CRE agar for the detection of carbapenem-resistant gram-negative bacteria.

The aim of this work was to evaluate the performance of the new chromogenic medium BrillianceTM CREAgar (Thermo Fisher Scientific) for determining the limit of detection of carbapenem-resistant enterobacteria (CRE). A total of 70 clinical isolates were studied. Of these, 30 were well-characterized CRE, including Klebsiella pneumoniae strains producing KPC-, VIM-, and OXA-type enzymes, VIM-positive Enterobacter cloacae and Escherichia coli, NDM-positive E. coli, and enterobacterial isolates characterized by porin loss associated with ESBL production or AmpC hyperproduction. Ten carbapenem-resistant non-fermentative isolates were also included as well as 30 carbapenem-susceptible isolates. Carbapenem-resistant strains were inoculated at three different concentrations onto Brilliance CRE Agar (from 1.5x101 CFU/ml up to 1.5x104 CFU/ml) whereas carbapenem-susceptible isolates were inoculated at a concentration of 1.5x102 CFU/ml. The medium sustained the growth of carbapenem-resistant isolates, showing detection limits from 1.5x101 CFU/ml (in 31/40 cases) to 1.5x104 CFU/ml. No growth was observed with carbapenem-sensitive control strains. Our results indicate that the Brilliance CRE Agar allows the growth of carbapenem-resistant isolates with low detection limits and could represent a useful screening medium for both enterobacteria and non-fermentative Gram-negative strains resistant to carbapenems.

Emergence and spread of a multidrug-resistant Acinetobacter baumannii clone producing both the carbapenemase OXA-23 and the 16S rRNA methylase ArmA.

Acinetobacter baumannii is a Gram-negative organism reported worldwide as a cause of health-care-associated infections, particularly in intensive care units (ICUs). The aim of this study is to describe the emergence and spread of carbapenem-resistant A. baumannii (CRAB) isolates in hospitalized patients. From March to November 2009, multidrug-resistant CRAB isolates were obtained from 21 patients hospitalized in different wards (mostly ICUs). Antimicrobial susceptibility was determined by using the Etest method. Carbapenem and aminoglycoside resistance determinants were studied by PCR and sequencing. Genetic relatedness was investigated by pulsed-field gel electrophoresis and multiplex PCR identification of sequence groups. Clinical records of patients were examined retrospectively. CRAB isolates were consistently resistant to multiple drugs including fluoroquinolones and aminoglycosides, whereas they retained a susceptibility to colistin. Molecular analysis revealed that 19 of the 21 CRAB isolates belonged to a single clone producing both the carbapenemase OXA-23 and the 16S rRNA methylase ArmA. Based on clinical data, the patients included in the study were classified as infected (n=13) or colonized (n=8). Colistin alone or in combination with ampicillin-sulbactam was administered to 11 of the 13 infected patients. A complete or partial response was obtained in eight cases, whereas a failure to respond was observed in one patient and a relapse was observed in two patients. An A. baumannii clone producing both OXA-23 and ArmA has been identified as an emerging and rapidly spreading pathogen. To our knowledge, this is the first report of the ArmA enzyme in A. baumannii in Italy and is the first report of hospital dissemination of A. baumannii carrying both bla(OXA-23) and armA genes.

Antifungal susceptibility of invasive yeast isolates in Italy: the GISIA3 study in critically ill patients.

BACKGROUND: Yeasts are a common cause of invasive fungal infections in critically ill patients. Antifungal susceptibility testing results of clinically significant fungal strains are of interest to physicians, enabling them to adopt appropriate strategies for empiric and prophylactic therapies. We investigated the antifungal susceptibility of yeasts isolated over a 2-year period from hospitalised patients with invasive yeast infections. METHODS: 638 yeasts were isolated from the blood, central venous catheters and sterile fluids of 578 patients on general and surgical intensive care units and surgical wards. Etest strips and Sensititre panels were used to test the susceptibility of the isolates to amphotericin B, anidulafungin, caspofungin, fluconazole, itraconazole, posaconazole and voriconazole in 13 laboratories centres (LC) and two co-ordinating centres (CC). The Clinical and Laboratory Standards Institute (CLSI) reference broth microdilution method was used at the CCs for comparison. RESULTS: Etest and Sensititre (LC/CC) MIC90 values were, respectively: amphotericin B 0.5/0.38, 1/1 mg/L; anidulafungin 2/1.5 and 1/1 mg/L; caspofungin 1/0.75 and 0.5/0.5 mg/L; fluconazole 12/8 and 16/16 mg/L; itraconazole 1/1.5, 0.5/0.5 mg/L; posaconazole 0.5 mg/L and voriconazole 0.25 mg/L for all. The overall MIC90 values were influenced by the reduced susceptibility of Candida parapsilosis isolates to echinocandins and a reduced or lack of susceptibility of Candida glabrata and Candida krusei to azoles, in particular fluconazole and itraconazole. Comparison of the LC and CC results showed good Essential Agreement (90.3% for Etest and 92.9% for Sensititre), and even higher Categorical Agreement (93.9% for Etest and 96% for Sensititre); differences were observed according to the species, method, and antifungal drug. No cross-resistance between echinocandins and triazoles was detected. CONCLUSIONS: Our data confirm the different antifungal susceptibility patterns among species, and highlight the need to perform antifungal susceptibility testing of clinically relevant yeasts. With the exception of a few species (e.g. C. glabrata for azoles and C. parapsilosis for echinocandins), the findings of our study suggest that two of the most widely used commercial methods (Etest and Sensititre) provide valid and reproducible results.

Prevalence and epidemiology of microbial pathogens causing bloodstream infections: results of the OASIS multicenter study.

Beginning on April 2007, a prospective multicenter study was performed to investigate prevalence and epidemiology of microbial pathogens causing bloodstream infections (BSIs). Twenty microbiology laboratories participated to the survey over a 1-year period. A total of 11,638 episodes of BSI occurred in 11 202 patients, with 8.5% (n=985) of episodes being polymicrobial. Of 12 781 causative organisms, aerobic Gram-negative bacteria were 47.4% (n=6058), whereas Gram-positives accounted for 43.9% (n=5608). The remaining organisms included fungal species (n=924, 7.2%) and anaerobes (n=191, 1.5%). The most prevalent agents were Escherichia coli (21.7%), Staphylococcus aureus (14.9%), Staphylococcus epidermidis (8.2%), Pseudomonas aeruginosa (7.0%), and Enterococcus faecalis (6.3%). Isolates recovered from patients admitted to medical, surgical, and intensive care units accounted for 62.9%, 17.7%, and 19.4% of cases, respectively. BSIs were classified as hospital-acquired in 67.2% of cases. Compared with previous studies, our data show an increasing role of Gram-negative bacteria among both hospital- and community-acquired blood isolates.

Spread of multidrug-resistant Proteus mirabilis isolates producing an AmpC-type beta-lactamase: epidemiology and clinical management.

A remarkable increase in Proteus mirabilis strains producing acquired AmpC-type beta-lactamases (CBLs) has been observed at Ospedale di Circolo e Fondazione Macchi (Varese, Italy) over the last few years. The epidemiology and treatment outcome of infections associated with this unprecedented spread are reported. From 2004-2006, 2070 P. mirabilis isolates were investigated. Extended-spectrum beta-lactamases (ESBLs) and CBL resistance determinants were identified by gene amplification and direct sequencing. Clonal relatedness was evaluated by macrorestriction analysis. Overall, 43 CBL-positive isolates were obtained from hospitalised (n=22) and non-hospitalised (n=21) patients (median age 78.8 years). The prevalence of CBL-positive isolates increased from 0.3% in 2004 to 4.6% in 2006, whereas that of ESBL-positive isolates remained constant (ca. 10%). CBL-positive isolates were multidrug-resistant and carried the CMY-16 determinant. All but two isolates were genetically identical or closely related. Retrospective analysis of clinical records revealed that the majority of CMY-16-positive isolates were associated with urinary tract infections. Treatment with amikacin or carbapenems was consistently effective, whereas piperacillin/tazobactam produced a clinical response in seven of nine cases. This is the first report of a rapid spread of CBL-positive P. mirabilis strains endowed with remarkable antimicrobial resistance. Practical methods for CBL detection are needed for the appropriate management of related infections.

Identification of coagulase-negative Staphylococci by using the BD phoenix system in the low-inoculum mode.

The new "low-inoculum" mode of the Phoenix system was evaluated to identify clinical coagulase-negative staphylococci. API ID32 Staph panels were used as comparators, and discrepancies were resolved by 16S rRNA and tuf gene analysis. The system correctly identified 90.5% of isolates, with a mean time of 10.2 h. Accuracy was satisfactory for Staphylococcus epidermidis, S. saprophyticus, and S. haemolyticus.

Drug susceptibility testing of clinical isolates of streptococci and enterococci by the Phoenix automated microbiology system.

BACKGROUND: Drug resistance is an emerging problem among streptococcal and enterococcal species. Automated diagnostic systems for species identification and antimicrobial susceptibility testing (AST) have become recently available. We evaluated drug susceptibility of clinical isolates of streptococci and enterococci using the recent Phoenix system (BD, Sparks, MD). Diagnostic tools included the new SMIC/ID-2 panel for streptococci, and the PMIC/ID-14 for enterococci. Two-hundred and fifty isolates have been investigated: beta-hemolytic streptococci (n = 65), Streptococcus pneumoniae (n = 50), viridans group streptococci (n = 32), Enterococcus faecium (n = 40), Enterococcus faecalis (n = 43), other catalase-negative cocci (n = 20). When needed, species ID was determined using molecular methods. Test bacterial strains were chosen among those carrying clinically-relevant resistance determinants (penicillin, macrolides, fluoroquinolones, glycopeptides). AST results of the Phoenix system were compared to minimal inhibitory concentration (MIC) values measured by the Etest method (AB Biodisk, Solna, Sweden). RESULTS: Streptococci: essential agreement (EA) and categorical agreement (CA) were 91.9% and 98.8%, respectively. Major (ME) and minor errors (mE) accounted for 0.1% and 1.1% of isolates, respectively. No very major errors (VME) were produced. Enterococci: EA was 97%, CA 96%. Small numbers of VME (0.9%), ME (1.4%) and mE (2.8%) were obtained. Overall, EA and CA rates for most drugs were above 90% for both genera. A few VME were found: a) teicoplanin and high-level streptomycin for E. faecalis, b) high-level gentamicin for E. faecium. The mean time to results (+/- SD) was 11.8 +/- 0.9 h, with minor differences between streptococci and enterococci. CONCLUSION: The Phoenix system emerged as an effective tool for quantitative AST. Panels based on dilution tests provided rapid and accurate MIC values with regard to clinically-relevant streptococcal and enterococcal species.

Use of the Phoenix automated system for identification of Streptococcus and Enterococcus spp.

The Phoenix system (Becton Dickinson Diagnostic Systems, Sparks, MD) was evaluated for identification (ID) to the species level of streptococci and enterococci. Two hundred clinical isolates were investigated: beta-hemolytic streptococci (n = 50), Streptococcus pneumoniae organisms (n = 46), viridans group streptococci (n = 31), Enterococcus faecium (n = 36), Enterococcus faecalis (n = 25), and other catalase-negative cocci (n = 12). The API system (bioMérieux, Marcy l'Etoile, France) was used as a comparator. Molecular methods (sequencing of 16S rRNA and zwf and gki genes and ddl gene amplification) were used to investigate discordant results. Upon resolution of discrepancies, correct species ID was achieved by the Phoenix system for 121/129 (93.8%) streptococci and 63/70 (90.0%) enterococci. Excellent results were obtained for S. pneumoniae (45/45) and beta-hemolytic streptococci (49/50). With regard to viridans streptococci, the accuracy of the Phoenix system was 83.9%. Among the latter organisms, the best performance was obtained with isolates of the Streptococcus sanguinis group and Streptococcus anginosus group; problems were instead encountered with the Streptococcus mitis group. Four E. faecium and three E. faecalis isolates were misidentified as Enterococcus casseliflavus/Enterococcus gallinarum or Enterococcus durans. Thus, these isolates were identified only at the genus level. Compared with commercially available systems, the Phoenix system appears a reliable diagnostic tool for identifying clinically relevant streptococci and enterococci. The SMIC/ID-2 panel proved particularly effective for beta-hemolytic streptococci and pneumococci.

CTX-M-type extended-spectrum beta-lactamases in Italy: molecular epidemiology of an emerging countrywide problem.

A nationwide survey of extended-spectrum beta-lactamase (ESBL) production among Enterobacteriaceae, carried out in 2003, showed that CTX-M-type enzymes have achieved a sizeable prevalence among ESBL producers in Italy, mostly in Escherichia coli and, to a lesser extent, in Klebsiella pneumoniae. In this work, we report on the molecular epidemiology of the CTX-M-producing isolates from that survey and on the mechanisms of dissemination of these emerging resistance determinants. The CTX-M-producing isolates were detected in 10 of the 11 participating centers distributed across the Italian national territory, although at remarkably variable rates in different centers (1.2 to 49.5% of the ESBL producers). All CTX-M determinants were of group 1, with CTX-M-15 and CTX-M-1 being the most prevalent variants (60% and 35%, respectively) and CTX-M-32 carried by a minority (5%) of isolates. Each variant was detected both in E. coli and in K. pneumoniae. Genotyping of the CTX-M-producing isolates by random amplification of polymorphic DNA revealed a notable diversity, especially among those producing CTX-M-1, while clonal expansion was evident with some CTX-M-15-producing strains. Mating experiments revealed a higher overall transferability of bla(CTX-M-1) and bla(CTX-M-32) than of bla(CTX-M-15). Coresistance to quinolones and aminoglycosides was overall higher with the CTX-M-15-producing isolates. The present results indicate that CTX-M-producing strains are now widespread across the Italian territory and underscore the emerging role of these ESBL determinants in the European setting. They also reveal notable differences in the dissemination mechanisms of genes encoding different CTX-M variants of the same lineage.

Failure of levofloxacin treatment in community-acquired pneumococcal pneumonia.

BACKGROUND: Streptococcus pneumoniae is the leading cause of community-acquired pneumonia (CAP). High global incidence of macrolide and penicillin resistance has been reported, whereas fluoroquinolone resistance is uncommon. Current guidelines for suspected CAP in patients with co-morbidity factors and recent antibiotic therapy recommend initial empiric therapy using one fluoroquinolone or one macrolide associated to other drugs (amoxicillin, amoxicillin/clavulanate, broad-spectrum cephalosporins). Resistance to fluoroquinolones is determined by efflux mechanisms and/or mutations in the parC and parE genes coding for topoisomerase IV and/or gyrA and gyrB genes coding for DNA gyrase. No clinical cases due to fluoroquinolone-resistant S. pneumoniae strains have been yet reported from Italy. CASE PRESENTATION: A 72-year-old patient with long history of chronic obstructive pulmonary disease and multiple fluoroquinolone treatments for recurrent lower respiratory tract infections developed fever, increased sputum production, and dyspnea. He was treated with oral levofloxacin (500 mg bid). Three days later, because of acute respiratory insufficiency, the patient was hospitalized. Levofloxacin treatment was supplemented with piperacillin/tazobactam. Microbiological tests detected a S. pneumoniae strain intermediate to penicillin (MIC, 1 mg/L) and resistant to macrolides (MIC >256 mg/L) and fluoroquinolones (MIC >32 mg/L). Point mutations were detected in gyrA (Ser81-Phe), parE (Ile460-Val), and parC gene (Ser79-Phe; Lys137-Asn). Complete clinical response followed treatment with piperacillin/tazobactam. CONCLUSION: This is the first Italian case of community-acquired pneumonia due to a fluoroquinolone-resistant S. pneumoniae isolate where treatment failure of levofloxacin was documented. Molecular analysis showed a group of mutations that have not yet been reported from Italy and has been detected only twice in Europe. Treatment with piperacillin/tazobactam appears an effective means to inhibit fluoroquinolone-resistant strains of S. pneumoniae causing community-acquired pneumonia in seriously ill patients.

Dissemination of CTX-M-type extended-spectrum beta-lactamase genes to unusual hosts.

A Citrobacter amalonaticus and a Morganella morganii producing the CTX-M-1 extended-spectrum beta-lactamase (ESBL) were isolated from an area where this enzyme is now widespread in Escherichia coli. This is the first report of CTX-M-1 in the former species. In both cases the ESBL determinant was possibly acquired by these unusual hosts in vivo, after coinfection with E. coli strains carrying conjugative plasmids encoding CTX-M-1.

Proteus mirabilis bloodstream infections: risk factors and treatment outcome related to the expression of extended-spectrum beta-lactamases.

Bloodstream infection (BSI) due to Proteus mirabilis strains is a relatively uncommon clinical entity, and its significance has received little attention. This study was initiated to evaluate risk factors and treatment outcome of BSI episodes due to P. mirabilis producing extended-spectrum beta-lactamases (ESBLs). Twenty-five BSI episodes caused by P. mirabilis occurred at our hospital (Ospedale di Circolo e Fondazione Macchi, Varese, Italy) over a 7.5-year period. Phenotypic and molecular methods were used to assess ESBL production. Clinical records of BSI patients were examined retrospectively. Demographic data, underlying diseases (according to McCabe and Jackson classification and Charlson weighted index), risk factors, and treatment outcome were investigated by comparing cases due to ESBL-positive strains to cases due to ESBL-negative strains. Eleven isolates were found to express ESBLs (TEM-52 or TEM-92). The remaining 14 isolates were ESBL negative and were uniformly susceptible to extended-spectrum cephalosporins and monobactams. Comparison of the two groups showed that previous hospitalization in a nursing home (P = 0.04) and use of bladder catheter (P = 0.01) were significant risk factors for infections due to ESBL-positive strains. In addition, cases due to ESBL-positive strains showed a significantly higher mortality attributable to BSI (P = 0.04). BSI cases due to ESBL-negative isolates uniformly responded to therapy, whereas 5/11 cases due to ESBL-positive isolates failed to respond (P < 0.01). Use of carbapenems was associated with complete response independently of ESBL production. Therapeutic failure and mortality may occur in BSI episodes caused by ESBL-positive P. mirabilis isolates. Thus, recognition of ESBL-positive strains appears to be critical for the clinical management of patients with systemic P. mirabilis infections.

Evolution of CTX-M-type beta-lactamases in isolates of Escherichia coli infecting hospital and community patients.

Escherichia coli isolates collected at our Institution from 1999 to 2003 (n=20,258) were studied to evaluate the production of CTX-M-type extended-spectrum beta-lactamases (ESBL). Isolates suspected of producing CTX-M enzymes were analyzed by the double-disk synergy test, hybridization with specific probes, PCR and direct DNA sequencing. Overall, 53 ESBL-positive isolates were found to carry CTX-M-type genes (blaCTX-M-1, n=51; blaCTX-M-15, n=2). The isolation of CTX-M-positive strains increased from 1 per year (1999) to 26 per year (2003). The first isolate carrying the blaCTX-M-15 gene appeared in 2003 and was obtained from a patient previously treated with ceftazidime. CTX-M-positive isolates were characterized by multi-drug resistance and were obtained both from inpatients (n=29) and outpatients (n=24). Most patients were over 60-year-old (n=45), had underlying chronic diseases (n=32), and had been hospitalized more than once (n=33). Strains were frequently isolated from the urinary tract, often after recurrent infections. Our study demonstrates that CTX-M-producing isolates are increasing among E. coli strains. Adequate laboratory detection may help in choosing appropriate treatment and in limiting the spread of this resistance trait.