ALEKSANDRA PRESEČKI STANKO

BRANKA BEDENIĆ

DIJANA VARDA BRKIĆ

SANJA PLEŠKO

VESNA TRIPKOVIĆ

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       SIGNA VITAE    |    13Acinetobacter baumannii microbiological and phenotypic characteristics of isolates from Intensive Care Unit of the Department of Internal Medicine at the University Hospital Centre in Zagreb over a four-year periodDIJANA VARDA BRKIĆ1 , ALEKSANDRA PRESEČKI STANKO1, SANJA PLEŠKO1, VESNA TRIPKOVIĆ1,  BRANKA BEDENIĆ1,21 Department of Clinical and Molecular Microbiology, University Hospital Centre Zagreb, Kišpatićeva 12, Zagreb, Croatia2 School of Medicine, University of Zagreb, Zagreb, CroatiaCorresponding author:  Dijana Varda BrkićClinical Department for Clinical and Molecular Microbiology, University Hospital Centre Zagreb, Kišpatićeva 12Phone: 01 23 67 318Fax: 01 23 67 393E-mail: dijanavb098@gmail.com ABSTRACT Acinetobacter baumannii is an opportun-istic nosocomial pathogen and one of the six most important multidrug-resistant microorganisms in intensive care units (ICU). The aim of this study was to determine the prevalence of antimicrobial resistant A. baumannii strains in ICU. We analysed antibiotic susceptibility of A. baumannii isolates collected in University Hospital Centre Zagreb over a four-year period (2011-2014) based on the hospital computer system data (BIS). The data were interpreted according to Clinical and Lab-oratory Standards Institute criteria.All strains from 2014 were found to be resistant to meropenem, which is a sig-nificant increase when compared to 1.4% in 2011 and 81.8% in 2012. The resistance rate to imipenem increased to 95.8% in 2014 from 91.4% in 2011 and 81.8% in 2012. Colistin resistance, confirmed by E test, was found only in one strain in 2013. The resistance rates of other antimicrobial agents were as follows: ampicillin/sulbac-tam 8.6% and 73.9%, netilmicin 70.6% and 83.3%, gentamicin 48.6% and 91.7%, ami-kacin 82.4% and 80.0% and ciprofloxacin 100% and 100% in 2011 and 2014 respec-tively.Our data confirmed a multidrug-resist-ance phenotype in Acinetobacter bauman-nii strains isolated in ICU at the Clinical Hospital Centre, with a significant increase in resistance rates between 2011 and 2014 against certain antimicrobial agents in-cluding ampicilin/sulbactam and carbap-enems. Key words: Acinetobacter baumannii, mul-tidrug resistance, extensively drug resist-ance, nosocomial pathogenINTRODUCTIONAcinetobacter spp. are glucose non-fer-menting, non-motile, catalase positive, and oxidase negative aerobic gram-neg-ative cocobacilli. (1) The most important species in human medicine is Acinetobac-ter baumannii. It is nowadays the leading causative agent of health care associated infections and is often called Gram-neg-ative MRSA. (2) Health care associated infections tend to occur in debilitated pa-tients in intensive care units (both children and adults) and among residents of long-term care facilities (particulary facilities caring for ventilator-dependent patients). Additional risk factors include recent sur-gery, central vascular catheterization, tra-cheostomy, mechanical ventilation, enteral feedings, and treatment with third genera-tion cephalosporin, fluoroquinolones, or carbapenem antibiotics. (1,3) It has a great capacity of acquiring resistance traits and spreading within the hospital environ-ment. Many factors contributed to the vir-ulence of Acinetobacter species: survival in dry and iron-deficient conditions for a long period of time, the production of a polysaccharide capsule that works with the cell wall liposaccharide to prevent com-plement activation. The capsule prevents phagocytosis and enables the survival of bacteria in the blood. Colonisation in the lung is facilitated by the ability of Acineto-bacter to adhere to human bronchial epi-thelial cells using fimbriae. (4) In addition, the colonization of environmental surfaces is promoted by adhesion via pili and the subsequent formation of biofilm. Most A. baumannii isolates are highly resistant to most antibiotics available in clinical prac-tice due to intrinsic and acquired resist-ance mechanisms. A number of resistance mechanisms to many classes of antibiotics are known to exist in A. baumanni, includ-ing β-lactamases production (particu-larly carbapenemases), upregulated efflux pumps, production of aminoglycoside-modifying enzymes, permeability defects and the alteration of target sites. (1) The spread of multidrug resistance determi-nants in A. baumannii occurs by conjuga-tion, transposon acquisition or integron mobilization to gain clusters of genes en-coding resistance to several antibiotics families.(5)SIGNA VITAE 2015; 10(SUPPL 1): 13-1514   |  SIGNA VITAEThe aim was to analyze the prevalence and antibiotic sensitivity patterns of Acineto-bacter baumannii isolates from patients hospitalized at the Department for Inten-sive Care Medicine, University Hospital Centre Zagreb. The number and the type of microbiological specimens with A. bau-mannii were determined as well.  MATERIAL AND METHODSThe data are based on a retrospective study conducted between 1 January 2011 and 31 December 2014. The data were collected from the hospital computer system (BIS). Only one isolate per patient was included in the study. Antibiotic susceptibility was determined according to EUCAST guide-lines (European Committee on Antimicro-bial Susceptibility Testing). The general pa-rameters of ICU (number of beds, number of patients and the total number of bacte-riological results) were used to calculate the resistance rates and the proportion of A. baumannii in the total number of posi-tive bacteriological results. RESULTSThe Department for Intensive Care Medi-cine has 12 beds. The total number of pa-tients hospitalized in the department in the study period (2011-2014) was as follows: 589, 590, 590, 562 , while the number of patients  with A. baumannii isolates was 50, 20, 47, 37 in 2011, 2012, 2013 and 2014 respectively (table 1.). The largest number of A. baumannii isolates originated from respiratory tract specimens (tracheal as-pirate, BAL, minilavate) during the whole four-year study period (figure 1).Resistance rates for meropenem ranged from 81.8 % (2012) to 100% (2014). Simi-larly, imipenem showed the resistance rate which increased from 81.8% in 2011 to 95.8% in 2014. The highest increase of the resistance rate was observed for ampicilin/sulbactam from 8.6% in 2012 to 73.9% in 2014 and for gentamicin with the range from 48.6% in 2011 to 91.7%. in 2014. No resistance rate to colistin was observed, except for one single strain (figure 2). The resistance rates to amikacin and cipro-floxacin did not change during the study period. Figure 1. The proportion of A. baumannii isolates from various clinical samplesBlood c.= Blood culture, i.v. cat.= intravascular catether samplesResp. s. = respiratory samples, Surv. c.= surveillancy culture, UC= urine culture Figure 2. Percentage of  A. baumannii strains resistant to various antibiotics over a four year period (2011-2014)AMI=amikacinCIP= ciprofloxacin, COL=colistin, GEN= gentamicin, IMI= imipenem, MEM= meropenem, NET=netilmicin, SAM=ampicilin/sulbactam, DISCUSSIONIn our study A. baumannii was isolated in 9-17.2 % of all bacteriological specimens, which is comparable to Prashanth et al. with 10% Acinetobacter isolates (6), Path-wardhan et al. with 13-23% (7) and Purti et al. with 11.96% .(8) The most common site for A. baumannii infection is the respira-tory tract and the most common manifes-tation is VAP (9). This is in concordance with the high number of isolates from the respiratory tract and blood cultures in our study. The ability of Acinetobacter strains to adhere to the surface is an important mechanism in pathogenicity. It frequently causes infections associated with medi-cal devices, e.g. vascular catheters. Bio-film formation is a well-known virulence mechanism in such infections. (10) This explains a high number of strains from vascular catheter swabs and lavates. Analysis of susceptibility patterns showed that most isolates do not have only the multidrug-resistant phenotype (MDR) but also extensively drug-resistant phenotype (XDR). Proportion of XDR A. bauman-nii in total number of MDR A. baumannii increased from 24% and 5% in 2011 and 2012 to 40% and 70.2 % in 2013 and 2014. A similar proportion of XDR A. bauman-nii of 72.4 % was reported in the study byMetan et al. at the bone marrow clinic. (11) The proportion of isolates resistant to carbapenems (imipenem, meropenem) in our ICU reached the peak level in 2014 (100% resistant to meropenem, 95% to imipenem). Guven et al. reported in their study from 2011 the resistance rate to car-bapenems of 98.9%, also in ICU. (12) The hospital in general demonstrated in 2014. a smaller resistance rate to carbapenems of 87.8%, compared to ICU. On the national level, there was also an increase from 23% in 2009 to 80% in 2013 in Croatia. (13) Clinical studies showed higher mortal-ity rates of patients infected with carbap-enem-resistant strains compared to those infected with carbapenem-susceptible strains. (14, 15) An alarming increase of the resistance rate was reported for ampici-lin/sulbactam from 8.6% in 2012 to 73.9% in 2014 in ICU. In the hospital in general the resistance rate for ampicillin/sulbac-tam was 64%, while in the whole country the rate was 26%. No resistance to colistin was observed except in one single strain. At the University Hospital Centre the re-sistance rate for colistin was 1.6%, which is slightly higher than at the national level in Croatia (1%). The first study on carbap-enem resistance in A. baumannii at the University Hospital Centre Zagreb dem-onstrated the emergence of OXA-72 beta-lactamase belonging to OXA-24-like group among isolates from 2008. (16) CONCLUSIONThe total number of A. baumannii in ICU was similar in each year during the study period, but the increase of resistance rates and the increased proportion of XDR A. baumannii compared to the total number of A. baumannii were observed. The increase of resistance rates to carbapenem and am-picillin/sulbactam is worrisome. Early iden-tification, effective strategies to control the use of antibiotics and continuous surveil-lance and enforcement of specific infection control measures are strongly emphasized.       SIGNA VITAE    |    15Table 1. Epidemiological  parameters in ICUParameter 2011. 2012. 2013. 2014.The number of patients with A. baumannii isolat 50 20 47 37 Number/1000 bo  days ( ‰) 15,7 6,8 17,2 13,06Number of microbiological specimens with A.baumannii isolate 69 48 96 62% of total bacteriological specimens 13,5 9 17,2 11,2REFERENCES1. Feng Lin M, Yu Lan C. Antimicrobial resistance in Acinetobacter baumannii: From bench to bedside. World  J  Clin Cases. 2014; 2(12):787-814.2. Falagas ME, Bliziotis IA, Siempos II. Attributable mortality of Acinetobacter baumannii infections in critically ill patients: A sys-tematic review of matched cohort and case-control studies. Crit Care. 2006;10: R48.3. Dijkshoorn L, Nemec A, Seifert H. An increasing threat in hospitals: Multidrug-resistant Acinetobacter baumannii. Nat Rev Mi-crobiol. 2007;5:939-951.4. Lee  JC, Koerten H, van den Broek P, et al. Adherence of Acinetobacter baumannii strains to human bronchial epithelial cells. Res Microbiol. 2006;157:360.5. Esterly J, Richardson CL, Eltoukhy NS, Qi C, Scheetz MH. Genetic Mechanisms of Antimicrobial Resistance of Acinetobacter baumannii. Ann Pharmacother. 2011.6. Prashanth K, Badrinath S. Nosocomial infections due to Acinetobacter species: Clinical findings, risk and prognostic factors. In-dian J Med Microbiol. 2006;24:39-44.7. Patwardhan RB, Dhakephalkar PK, Niphadkar KB, Chopade BA. 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Acinetobacter baumannii microbiological and phenotypic characteristics of isolates from Intensive Care Unit of the Department of Internal Medicine at the University Hospital Centre in Zagreb over a four-year period

Acinetobacter baumannii microbiological and phenotypic characteristics of isolates from Intensive Care Unit of the Department of Internal Medicine at the University Hospital Centre in Zagreb over a four-year period

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