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THE JOURNAL OF PREVENTIVE MEDICINE
CULTURAL AND BIOCHEMICAL CHARACTERISTICS
OF ACINETOBACTER SPP. STRAINS ISOLATED
FROM HOSPITAL UNITS
Sofia Constantiniu, Angela Romaniuc, Luminiţa Smaranda Iancu, Raluca Filimon, Iuliana Taraşi
Institute of Public Health Iaşi, Romania
Abstract. The A. baumanii and A. lwoffii strains, isolated from clinical and environment samples in hospital units, were investigated from the biochemical characteristics and their susceptibility to antimicrobial agent points of view. The nonfermenter, Gram-negative coccobacilli were classified in A. baumanii and A. lwoffii species on the basis of the catalase positive, oxidase negative, nonmotility, the fermentative/oxidative test and utilization of nutritive substrates. The percentages of susceptibility to antimicrobial agents varied according to the class of antimicrobial drugs. Only 16.6% of strains were sensitive to ampicillin, 25% to ceftriaxone, ceftazidime, gentamicin and kanamycin. Most of the strains were sensitive to ciprofloxacin and to imipenem (83.3% and 91.6% respectively). Key-words: Acinetobacter , strains, biochemical characteristics, susceptibility, antibiotics
Rezumat. Tulpini de A. baumanii şi A. lwoffii , izolate din probe clinice şi probe din mediul ambiant din unităţi spitaliceşti, au fost investigate privind comportamentul biochimic şi sensibilitatea la agenţi antimicrobieni. Tulpinile de cocobacili Gram-negativi, nonfermentativi, au fost identificate ca A. baumanii şi A. lwoffii pe baza testelor catalază pozitivă, oxidaza negativă, imobilitate, testul oxidare/fermentare pe mediul Hugh-Leifson şi activitatea pe diferite substraturi nutritive. Testarea sensibilităţii la substanţe antimicrobiene a evidenţiat procentaje variabile de sensibilitate/rezistenţă, în funcţie de clasele de antibiotice. Numai 16,6% din tulpini au fost sensibile la ampicilină, 25% sensibile la ceftriaxonă, ceftazidim, gentamicină şi kanamicină. 83.3% şi 91.6% dintre tulpini au fost sensibile la ciprofloxacin şi, respectiv la imipenem. Cuvinte cheie: Acinetobacter , tulpini, caractere biochimice, sensibilitate, antibiotice
INTRODUCTION Bacteria classified as members of the genus Acinetobacter have suffered a long history of taxonomic changes. The genus Acinetobacter is now defined as including gram-negative coccobacilli, with a DNA G+C content of 39 to 47 mol%, that are strictly aerobic, nonmotile, catalase positive and oxidase negative (1,2). Studies have revealed that the genus consists
of at least 12 DNA hybridization groups which are known as genospecies. Genospecies 1 is the type species A. calcoaceticus and is isolated from soil. Genospecies 2 is A. baumanii and includes those isolates previously referred to as A. calcoaceticus var. anitratus being the most prevalent ones in human clinical species (2,3). Genospecies 4, 5, 6, 7 and 8 are named A. haemolyticus , A. junii , A. johnsonii ,
Sofia Constantiniu, Angela Romaniuc, Luminiţa Smaranda Iancu, Raluca Filimon, Iuliana Taraşi
A_. lwoffii_ respectively. Genospecies 3, 6, 9, 10, 11 and 12 are unnamed (2). In the book of R. Weyant et al., 1996, Acinetobacter group was divided into 16 genomospecies (3). Acinetobacter species play a significant role in the colonization and infection of inpatients. They have been involved in a variety of nosocomial infections, including bacteremia, urinary tract infection and secondary meningitis. The main role as agent of nosocomial pneumonia, particularly ventilator-associated pneumonia was confined to hospital intensive care units. Some rare cases of community- acquired infections caused by Acinetobacter sp. have been reported. A propensity to tolerate drying and resistance to multiple classes of antibiotics are the key factors in enabling the organism to survive and spread in the nosocomial environment (1-7). In general, the treatment of infections with Acinetobacter sp. is often extremely difficult because of the widespread resistance to the major
groups of antibiotics of these species (1, 8-14). The aim of our paper was to present the cultural and biochemical characteristics and the sensitivity to antimicrobial agents of some Acinetobacter strains which were isolated in our laboratory in the period of 2001-2004.
MATERIAL AND METHODS A number of 24 Gram-negative strains, nonfermentative coccobacilli, were tested in order to be taxonomic framed. These strains were isolated from clinical and environmental specimens (table 1). A. baumanii was isolated from skin ( strains) and cordon (1 strain) of new- born in two large maternities from north-eastern of Romania, nasal swabs of adult patients (2 strains) in dialysis sections, the hand swabs of hospital workers (2 strains) and hospital environment (swabs on surfaces of different machines, wash-hand basins, floors, tables , UV lamps) (8 strains).
Table 1. Acinetobacter strains isolated from hospital environment samples
Species Clinical samples
Environmental samples Total
Acinetobacter baumanii^9 8
Acinetobacter lwoffii 3 4 7
Total 12 12 24
Sofia Constantiniu, Angela Romaniuc, Luminiţa Smaranda Iancu, Raluca Filimon, Iuliana Taraşi
Table 2. The biochemical characteristics of Acinetobacter sp. strains
Test, substrate A.baumanii (n=17)
A.lwoffii (n=7) Morphology Motility Fermentative or oxidative Catalase Oxidase Growth on MacConkey agar SS agar Acid from: Glucose Xylose Mannitol Sucrose Galactose Manose Rhamnose Lactose Maltose Esculin hydrolisis TSI acid: Slant Butt H 2 S: on TSI Simmons citrate Urea,Christensen Nitrate reduction Methyl red Voges-Proskauer
coccobacilli nonmotile O + - + V + + - - + + + + V - - - - + V - - -
coccobacilli nonmotile NO + - + V - - - - - - - - - - - - - V - - - -
Key reactions: O= oxidative; NO = nonoxidizer; + = positive reaction;
- = negative reactions; V= variable reactions.
Groups 1, 2, 3 and 13 TU have an extremely close relationship and are referred to some groups as the A. calcoaceticus – A. baumanii complex (1). Recent genetic studies have identified at least 16 separate Acinetobacter genomospecies. Table 3 shows some data concerning classification of Acinetobacter species and their characteristics. The information on
cellular fatty acid composition facilitates the classification of this group of bacteria (3). A. baumanii is the Acinetobacter genomic species of greatest clinical importance. Suspicion of infection can be revealed by repeated isolation of another genomic species, especially if clinical symptoms are also present (1-4).
CULTURAL AND BIOCHEMICAL CHARACTERISTICS OF Acinetobacter spp.
Table 3. Some common characteristics of Acinetobacter genomospecies (Weyant S.R. et al., 1996) Growth Genomospeciesnumber Proposedname Reference strain a oxidation Glucoseb Hemolysis Gelatin temp(°C) 37 41 44 Genomospecies 1 A.calcoaceticus ATCC23055 + - - + - - Genomospecies 2 A.baumanii ATCC19606 95 - - + + + Genomospecies 3 ATCC17922 + - - + + - Genomospecies 13 + - - + + 50 Genomospecies 10 ATCC17924 + - - + - - Genomospecies 14 and 13 +^ +^75 25 -^ - Genomospecies 15 50 - - + 50 - Genomospecies 14 + + + + - - Genomospecies 4 A.haemolyticum ATCC 17906 52 + 96 + - - Genomospecies 6 ATCC17979 66 + + + - - Genomospecies 12 A.radioresistensc^ ATCC43998 33 - - + - - Genomospecies 5 A.junii ATCC17908 - - - + 90 - Genomospecies 7 A.johnsonii ATCC17909 - - - - - - Genomospecies 8 A.lwoffii ATCC15309 - - - + - - Genomospecies 9 ATCC9957 - - - + - - Genomospecies 11 ATCC11171 - - - + - - Genomospecies 15 - + + + - - Genomospecies 16 - + + + - - Genomospecies 17 - + + + - - a = Type strain; b = numbers represent percentage of positives as reported by authors; c = this name was proposed by Nishimura et al., 1989; + and – represent 100% positive and 100% negative.
Susceptibility of the studied Acinetobacter strains to antimicrobial agents was ranged between 16.6% for AMP and 91.6% for IMP (fig. 1). Percentages of 20.8% of the strains were sensitive to CF, 25% to CTX, CAZ, GE and KA, and 41.6% to CH and TM, 66.6% to TE. Most of the strains were sensitive to CIP and IMP (83.3 % and 91.6% respectively). Other studies have shown a larger resistance of Acinetobacter sp. strains. More recently, the resistance to multiple antibiotics and to IMP has been increasingly. High resistance
percentages of A. baumanii strains to IMP were reported by Joshi et al., and Taneja et al. (29% and 36.4% respectively). Bayuga et al., reported 45% multiresistant A. baumanii strains and Joshi et al. showed that 75% of the isolates were multidrug resistant and more than 70% were lactamases- producers (9-16). It is very important to test the susceptibility of A. baumanii strains to antibiotics due to special properties of these species for rapid developing multiple anti-microbial resistances (1, 9-16).
CULTURAL AND BIOCHEMICAL CHARACTERISTICS OF Acinetobacter spp.
The percentages of susceptibility to antimicrobial agents varied depending on the class of antimicrobial drugs. Only 16.6% of strains were sensitive to AMP, 20.8% to CF, 25% to CTX, CAZ, GE and KA, and 41.6% to CH and TM. A higher percentage of the strains were sensitive to TE (66.6%). Most of the strains were sensitive to CIP and to IMP (83.3% and 91.6%). It is very important to test the susceptibility of A. baumanii strains to antibiotics because of the special property of these species in developing rapid multiple resistances to antimicrobial agents.
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