Il contributo del Microbiologo Clinico alla sorveglianza delle IO Giovanni P. Gesu S.C. Microbiologia e Virologia A.O. Ospedale Niguarda Ca’ Granda Milano Verona, 25 maggio 2005

Trend di Resistenza Batterica Il contributo del Microbiologo Clinico alla sorveglianza delle IO Trend di Resistenza Batterica A continuous shift toward more resistant strains of bacteria has been reported for several decades. Concern has focused on MRSA, VRE, ESBLs, fluoroquinolone-resistant Pseudomonas aeruginosa, and fluconazole-resistant Candida spp.100,101 These pathogens have become the leading causes of NIs, particularly in ICUs where most were found to have a certain specificity according to the type of ICU.13,102,103 The predominant pathogens reported in the ICUs participating in the NNIS and in European countries are coagulase-negative staphylococci (CoNS), S aureus, P aeruginosa, entercococci, and Candida spp (Table 6).16,35,37,60,104 NNIS System Am J Infect Control 2004; 32:470-85

Ruolo del Laboratorio di Microbiologia Individuazione di Epidemie di IO Ricerca di microrganismi multi-resistenti Supporto ai clinici su Disinfezione Sterilizzazione Procedure di isolamento Utilizzo razionale di antibiotici

Acinetobacter - Resistenza naturale Il contributo del Microbiologo Clinico alla sorveglianza delle IO Acinetobacter - Resistenza naturale fos AMX TIC CF MOX CTX MA FOX IPM AMC TCC PIP CFS CAZ ATM cip 2.3 Resistenza naturale Le specie di Acinetobacter producono una beta-lattamasi cromosomica, molto probabilmente di classe C, non inibita dal clavulanato, che idrolizza preferenzialmente le cefalosporine di prima generazione, ma che non ha attività sulle penicilline e la piperacillina. Per questa ragione, Acinetobacter è naturalmente resistente alla cefalotina mentre la ticarcillina è attiva.

Acinetobacter - Resistenza acquisita Il contributo del Microbiologo Clinico alla sorveglianza delle IO Acinetobacter - Resistenza acquisita fos AMX TIC CF MOX CTX MA FOX IPM AMC TCC PIP CFS CAZ ATM cip 2.4 Resistenza acquisita La resistenza ai beta-lattamici in Acinetobacter è complessa e pone spesso seri problemi in quanto risulta frequentemente dalla produzione simultanea di enzimi differenti. Sono stati caratterizzati alcuni isolati di Acinetobacter baumanii resistenti alla maggior parte dei beta-lattamici (eccetto Ceftazidime e Imipenem). Questi ceppi producevano 3 beta-lattamasi differenti: una cefalosporinasi cromosomica, una beta-lattamasi TEM-1 ed un enzima di tipo OXA denominato OXA-21 e situato su un integrone.

Acinetobacter – Resistenza a Imipenem Il contributo del Microbiologo Clinico alla sorveglianza delle IO Acinetobacter – Resistenza a Imipenem fos AMX TIC CF MOX CTX MA FOX IPM AMC TCC PIP tet x4 CAZ ATM cip 2.4.2 Resistenza all'Imipenem Può essere non enzimatica. In questi casi deriva da modificazioni delle PBP che determinano una diminuzione dell'affinità all'Imipenem. Più recentemente è stata descritta una beta-lattamasi di tipo OXA in un ceppo di Acinetobacter baumanii resistente all'Imipenem e che produceva due enzimi: Una cefalosporinasi cromosomica con pI > 9.2, e Un enzima con pI 6.3 che idrolizzava le isossazolil-penicilline e l'Imipenem con una attività elevata (inibita dagli ioni Cloro ma non dal clavulanato nè dall'EDTA). L'enzima era caratterizzato inoltre da una significativa attività idrolitica sulle cefalosporine di terza generazione

Il contributo del Microbiologo Clinico alla sorveglianza delle IO Introduction of the Vitek GNS-506 susceptibility testing cards in the Hippokration General Hospital, Thessaloniki, Greece, resulted in an apparently high prevalence of imipenem-resistant Acinetobacter baumannii. When 35 of these isolates were further tested by disk diffusion, broth microdilution, and agar dilution assays, 32 were imipenem sensitive by all tests and three were sensitive or intermediate, depending on the method. The pseudoresistant acinetobacters did not form a genetically homogeneous group. It is suggested that the detection of imipenem-resistant A. baumannii isolates by this system should be confirmed by an additional susceptibility test. Tsakris A et al. J Clin Microbiol 2000; 38:3505

Il contributo del Microbiologo Clinico alla sorveglianza delle IO Susceptibility of Pseudomonas aeruginosa from Lower Respiratory Tract Specimens Blandino G. et al Intl J Antimicrob Ag 2004 24:515   Francia Germania Italia Spagna Canada USA Amikacina 68.1 91.7 80.8 96.9 81.2 85.8 Cefepime 54.5 76.6 61.2 70.1 64.5 70.7 Ceftazidime 70.9 79.8 59.4 73.4 74.7 71.5 Ciprofloxacina 57.3 66 57.8 71.2 63 61 Gentamicina 42.4 72.1 53.3 65.8 67 67.1 Imipenem 69.8 70.8 63.1 71.4 77.6 74 Pipera/Tazo 71.3 88.9 81.9 80.2 88.7 84.9 Wenzel RP et al AAC 2003; 47:3089–3098 Susceptibilities of gram-negative bacteria isolated from lower respiratory tract specimens of hospitalized patients in four European countries, Canada, and the United States to antimicrobialsa Wenzel RP et al. AAC 2003; 47:3089

Il contributo del Microbiologo Clinico alla sorveglianza delle IO Organism Resistance Rates (%) P value 2001 2002 2003 MRSA All isolates 79.9 78.8 79.6 0.86 First isolate 70.2 65.7 64.1 0.006 CTX-R Kl. pneumoniae 47.7 64.6 48.4 0.46 32.1 45.5 29.2 0.13 IMI-R Ac. baumanni 30.9 11.1 5.3 < 0.0001 19.9 8.1 3.8 JOURNAL OF CLINICAL MICROBIOLOGY, Oct. 2004, p. 4776–4779 Vol. 42, We compared trends of annual resistance rates calculated from results for all isolates and for the first isolate of Staphylococcus aureus, Klebsiella pneumoniae, and Acinetobacter baumannii per patient over a 3-year period from 2001 through 2003. Antimicrobial susceptibility results of inpatients were extracted from a computerized database. Annual resistance rates of a species were calculated by two methods: from results for all isolates, even those from patients with multiple isolates in a given year and from results for the first isolate from a patient in a given year, regardless of susceptibility profile or specimen type. Rates of methicillin-resistant S. aureus (MRSA) did not differ among all isolates (79.9, 78.8 and 79.6%; P 0.86), but decreased for the first isolate per patient (70.2, 65.7, and 64.1%; P 0.006) over time. Annual duplication rates of methicillin-susceptible S. aureus (MSSA) decreased (39.6, 37.6, and 31.7%; P 0.01), but those of MRSA increased significantly (64.3, 67.8, and 68.9%; P 0.004). Rates of cefotaxime-resistant K. pneumoniae did not differ over time by either method, and rates of imipenem-resistant A. baumannii decreased over time by both methods. Duplication rates did not differ for either susceptible or resistant isolates of K. pneumoniae and A. baumannii. The trends in MRSA rate differed by the two methods because of the different proportion of duplicate isolates per year. MRSA rates might be increasingly overestimated for all isolates. These results suggest that the method of calculating results for the first isolate per patient may remove the effect of duplication, allowing the simple and unambiguous analysis of cumulative susceptibility rates. Lee S-O et al. J Clin Microbiol 2004; 42:4776-4779

Ruolo del Laboratorio di Microbiologia Prelievi Ambientali e Colture per Controllo Infezioni quali campioni in quali situazioni Investigazione di Epidemie quali mezzi/strumenti Tipizzazione Epidemiologica degli Isolati quali aboratori di riferimento

Caratterizzazioni Fenotipiche per Uso Epidemiologico Tipizzazione di Proteus spp. Slime-test per Staphylococcus Emolisi sinergica (=) ()

Analisi Ambientale dell’Ospedale Acqua dell’Ospedale per Legionella Liquidi per Emodialisi Colture Test per Endotossina Colture dell’Aria per Funghi Superfici Ambientali Superfici di Dispositivi Medicali

Il contributo del Microbiologo Clinico alla sorveglianza delle IO NOTE. For hospital A, the total no. of patients was 218; the total no. of patient-days was 1,271,715; and the total no. of patients per 100,000 patient-days was 17.1. For hospital B, the totals were 71, 875,730, and 8.2, respectively. Data on patient-days were obtained from the budget offices of each institution; these data exclude maternity and pediatric patients and newborns. a Study year begins on the first day of the month that the first (hospital A) or second (hospital B) patient with a VRE blood isolate was identified at each institution. The 4 isolates from 1 patient identified in 1990 at hospital A were excluded from this comparison. Totale Pazienti con Batteriemia: 218 Totale giorni-paziente 1.271.715 Tot. pazienti per 100.000 gg/paz.: 17.1 Totale Pazienti con Batteriemia: 71 Totale giorni-paziente 875.730 Tot. pazienti per 100.000 gg/paz.: 8.2 Clinical Infectious Diseases 2003; 37:921–8

Sorveglianza e Clonalità dei VRE Il contributo del Microbiologo Clinico alla sorveglianza delle IO Sorveglianza e Clonalità dei VRE 218 batteriemie 75% delle BSI da VRE 71 batteriemie The impact of active surveillance of patients at risk for infection with vancomycin-resistant enterococci (VRE) was examined, and VRE bacteremia rates and the degree of VRE clonality in 2 similar neighboring hospitals were compared. Hospital A did not routinely screen patients for VRE rectal colonization; hospital B actively screened high-risk patients. Retrospective observations were made over the course of 6 years, beginning when initial VRE bloodstream isolates were recovered at each institution. The rate of VRE bacteremia was 2.1-fold higher at hospital A, and the majority of hospital A isolates were clonally related: 4 clones were responsible for infection in >75% of patients with VRE bacteremia, and isolates from 30% of patients were from the most common clone. The 4 most common clones at hospital B were responsible for infection in 37% of patients, and isolates from 14.5% of patients were from the most common clone. Lower VRE bacteremia rates and a more polyclonal population, representing less horizontal transmission, may result from routine screening of patients who are at risk for VRE and prompt contact isolation of colonized individuals. 37% delle BSI da VRE Price CS et al. CID 2003; 37:921

PFGE patterns of VRE from blood Il contributo del Microbiologo Clinico alla sorveglianza delle IO PFGE patterns of VRE from blood Figure 2. PFGE patterns of representative vancomycin-resistant enterococcal blood isolates from patients at hospital B. Lane 1, 48.5-kb l DNA molecular weight ladder; lanes 2–14, strains F302 (type RR0), F98 (type EE1), F106 (type GG0), EF1 (type A0), EF2 (type B0), EF46 (type C0), EF161 (type G0), EF251 (type H0), EF293 (type I0), EF318 (type J0), EF405 (type K0), EF587 (type N0), and EF1099 (type Q1), respectively; and lane 15, 48.5-kb l molecular weight ladder.

Procedure Diagnostiche Speciali Colture di Sorveglianza per Pazienti Immunocompromessi Dispositivi Intravascolari Prodotti della Banca del Sangue Siti Chirurgici Ortopedici Colture Quantitative del Contenuto dell’Intestino Tenue

Mani del Personale Sanitario Frequenza di Colonizzazione Il contributo del Microbiologo Clinico alla sorveglianza delle IO Mani del Personale Sanitario Frequenza di Colonizzazione Staphylococcus aureus 10.5-78.3% Carica batterica fino a 24 x106 cellule Tasso di colonizzazione Medici  36% Infermieri  18% MRSA fino al 16.9% VRE fino al 41% Sopravvivenza Mani Ambiente S. aureus  150 minuti 7 mesi VRE  60 minuti 4 mesi Frequency of colonized hands. Colonization of health care workers’ hands with S. aureus has been described to range between 10.5 and 78.3% (Table 1). Up to 24,000,000 cells can be found per hand (33). The colonization rate with S. aureus was higher among doctors (36%) than among nurses (18%), as was the bacterial density of S. aureus on the hands (21 and 5%, respectively, with more than 1,000 CFU per hand) (101). The carrier rate may be up to 28% if the health care worker contacts patients with an atopic dermatitis which is colonized by S. aureus (608, 609). MRSA has been isolated from the hands of up to 16.9% of health care workers. VRE can be found on the hands of up to 41% of health care workers (Table 1).

Aspirati Endotracheali di Sorveglianza (gennaio – aprile 2005)

Aspirati Endotracheali di Sorveglianza (gennaio – aprile 2005) A.O. Ospedale Niguarda Ca’ Granda

Valutazione Aspirati Endotracheali di Sorveglianza (gennaio – aprile 2005) A.O. Ospedale Niguarda Ca’ Granda

“Search and Destroy” Individuazione Selettiva dai Siti Colonizzati in Pazienti Staff dell’Ospedale Ambiente per Stafilococchi Oxacillina-Resistenti Enterococchi Vancomicina-Resistenti

Il contributo del Microbiologo Clinico alla sorveglianza delle IO 26/758 = 3.4% colonizzati da MRSA 5 = 19%  infezione da MRSA 137/667 = 21% colonizzati da MSSA p < 0.01 2 = 1.5%  infezione da MSSA Infezione in colonizzato da MRSA vs MSSA RR 13; 95% CI, 2.7-64 Infezione in non colonizzato da MRSA vs MSSA RR 9.5; 95% CI, 3.6-25 12/394 studiati acquisiscono MRSA 4 = 25%  infezione da MRSA 13/394 acquisiscono MSSA p < 0.01 3 = 2.0%  infezione da MSSA Background. Asymptomatic colonization with methicillin-resistant Staphylococcus aureus (MRSA) has been described as a risk factor for subsequent MRSA infection. MRSA is an important nosocomial pathogen but has currently been reported in patients without typical risk factors for nosocomial acquisition. This study was designed to evaluate the impact of asymptomatic nares MRSA colonization on the development of subsequent MRSA infection. The incidence of MRSA infection was examined in patients with and patients without MRSA or methicillin-susceptible S. aureus (MSSA) colonization at admission to the hospital and in those who developed colonization during hospitalization. Methods. Patients admitted to 5 representative hospital units were prospectively evaluated. Nares samples were obtained for culture at admission and during hospitalization. Laboratory culture results were monitored to identify all MRSA infections that occurred during the study period and 1 year thereafter. Results. Of the 758 patients who had cultures of nares samples performed at admission, 3.4% were colonized with MRSA, and 21% were colonized with MSSA. A total of 19% of patients with MRSA colonization at admission and 25% who acquired MRSA colonization during hospitalization developed infection with MRSA, compared with 1.5% and 2.0% of patients colonized with MSSA (P < .01) and uncolonized (P < .01), respectively, at admission. MRSA colonization at admission increased the risk of subsequent MRSA infection, compared with MSSA colonization (relative risk [RR], 13; 95% confidence interval [CI], 2.7–64) or no staphylococcal colonization (RR, 9.5; 95% CI, 3.6–25) at admission. Acquisition of MRSA colonization also increased the risk for subsequent MRSA infection, compared with no acquisition (RR, 12; 95% CI, 4.0–38). Conclusion. MRSA colonization of nares, either present at admission to the hospital or acquired during hospitalization, increases the risk for MRSA infection. Identifying MRSA colonization at admission could target a high-risk population that may benefit from interventions to decrease the risk for subsequent MRSA infection. Infezione dopo acquisizione di MRSA RR 12; 95% CI, 4.0-38 Davis KA et al. Clin Infect Dis 2004; 39:776–82

INF-NOS - Microrganismi Isolati

Il contributo del Microbiologo Clinico alla sorveglianza delle IO 94 pazienti sorvegliati con colture per lieviti  1126 colture 36 colonizzati e/o infetti da lieviti  167 colture (15%) POS 30 pazienti POS per Candida albicans 122 isolati genotipizzati  Nessuna correlazione tra pazienti diversi La colonizzazione da C. albicans è di derivazione ENDOGENA To evaluate the colonization of Candida species and the importance of cross-contamination with Candida albicans, we prospectively screened clinical specimens obtained from surgical patients in the intensive care unit (ICU) who had a high risk of yeast colonization. Genotyping of C. albicans was performed using microsatellite markers. Thirty-six of 94 patients acquired nosocomial yeast colonization and/or infection. A total of 1126 specimens were cultured, 167 (15%) of which yielded yeasts. All 122 isolates of C. albicans recovered from the 30 C. albicans–positive patients were genotyped. Twenty-four different genotypes were identified. No genotype was systematically associated with a specific room or time. Isolates recovered from different body sites of patients at different times had identical genotypes. Acquisition of C. albicans in the surgical ICU seems to be mainly endogenous. Microsatellite markers should also be developed for typing non-albicans Candida species to learn whether their epidemiology differs from that of C. albicans. Clinical Infectious Diseases 2002; 35:1477–83

Il contributo del Microbiologo Clinico alla sorveglianza delle IO Clinical Infectious Diseases 2005;40 (15 June) Background. The prevalence of multidrug resistance (MDR) among gram-negative bacilli is rapidly increasing. Quantification of the prevalence and the common antimicrobial coresistance patterns of MDR gram-negative bacilli (MDR-GNB) isolates recovered from patients at hospital admission, as well as identification of patients with a high risk of harboring MDR-GNB, would have important implications for patient care. Methods. Over a 6-year period, patients who harbored MDR-GNB (i.e., patients who had MDR-GNB isolates recovered from clinical cultures within the first 48 h after hospital admission) were identified. “MDR-GNB isolates” were defined as Pseudomonas aeruginosa, Escherichia coli, Enterobacter cloacae, and Klebsiella species isolates with resistance to at least 3 antimicrobial groups. A case-control study was performed to determine the independent risk factors for harboring MDR-GNB at hospital admission. Results. Between 1998 and 2003, the prevalence of MDR-GNB isolates recovered from patients at hospital admission increased significantly for all isolate species ( ), with the exception of P. aeruginosa( P ! .001 ( Pp.09). Of 464 MDR-GNB isolates, 12%, 35%, and 53% of isolates were coresistant to 5, 4, and 3 antimicrobial groups, respectively. Multivariable analysis identified age 65 years (odds ratio [OR], 2.8; 95% confidence interval [CI], 1.1–7.4; P ! .04), prior exposure to antibiotics for 14 days (OR, 8.7; 95% CI, 2.5 –30; P ! .001), and prior residence in a long-term care facility (OR, 3.5; 95% CI, 1.3–9.4; P ! .01) as independent risk factors for harboring MDR-GNB at hospital admission. Conclusion. A substantial number of patients harbor MDR-GNB at hospital admission. Identification of common coresistance patterns among MDR-GNB isolates may assist in the selection of empirical antimicrobial therapy for patients with a high risk of harboring MDR-GNB. Figure 1. Prevalence of isolates of multidrug-resistant gram-negative bacilli recovered within the first 48 h after admission to the hospital, by species. Only 1 isolate per patient per year was included in the study. Pop-Vicas AE et al. Clin Infect Dis 2005;40 (15 June)

Il contributo del Microbiologo Clinico alla sorveglianza delle IO ... even control measures able to repeatedly prevent sustained outbreaks in the short-term can result in long-term control failure resulting from gradual increases in the community reservoir Methicillin-resistant Staphylococcus aureus (MRSA) represents a serious threat to the health of hospitalized patients. Attempts to reduce the spread of MRSA have largely depended on hospital hygiene and patient isolation. These measures have met with mixed success: although some countries have almost eliminated MRSA or remained largely free of the organism, others have seen substantial increases despite rigorous control policies. We use a mathematical model to show how these increases can be explained by considering both hospital and community reservoirs of MRSA colonization. We show how the timing of the intervention, the level of resource provision, and chance combine to determine whether control measures succeed or fail. We find that even control measures able to repeatedly prevent sustained outbreaks in the short-term can result in long-term control failure resulting from gradual increases in the community reservoir. If resources do not scale with MRSA prevalence, isolation policies can fail ‘‘catastrophically.’’ If resources do not scale with MRSA prevalence, isolation policies can fail ‘‘catastrophically’’ Cooper BS et al. PNAS 2004; 101:10223–10228