Catheter-related bacteremia and multidrug-resistant Acinetobacter Iwoffii.

To the Editor: Acinetobacter species are ubiquitous in the environment. In recent years, some species, particularly A. baumannii, have emerged as important nosocomial pathogens because of their persistence in the hospital environment and broad antimicrobial drug resistance patterns (1,2). They are often associated with clinical illness including bacteremia, pneumonia, meningitis, peritonitis, endocarditis, and infections of the urinary tract and skin (3). These conditions are more frequently found in immunocompromised patients, in those admitted to intensive care units, or in those who have intravenous catheters, and those who are receiving mechanical ventilation (4,5).

The role of A. baumannii in nosocomial infections has been documented (2), but the clinical effect of other Acinetobacter species has not been investigated. A. lwoffii (formerly A. calcoaceticus var. lwoffii) is a commensal organism of human skin, oropharynx, and perineum that shows tropism for urinary tract mucosa (6). Few cases of A. lwoffii bacteremia have been reported (3,5-7). We report a 4-year (2002-2005) retrospective study of 10 patients with A. lwoffii bacteremia admitted to a 600-bed teaching hospital in central Italy.

All 10 patients were immunocompromised; 8 had used an intravascular catheter (peripheral or central) and 2 had used a urinary catheter. Blood cultures of the patients were analyzed with the BacT/ALERT 3D system (bioMerieux, Marcy l'Etoile, France). Isolates were identified as A. lwoffii by using the Vitek 2 system and the API 20NE system (both from bioMerieux).

Susceptibilities of 10 A. lwoffii isolates to 18 antimicrobial drugs were determined by the broth microdilution method, according to Clinical and Laboratory Standards Institute (CLSI, formerly NCCLS) guidelines (8). The drugs tested were amikacin, ampicillin-sulbactam, aztreonam, cefepime, cefotaxime, ceftazidime, ceftriaxone, ciprofloxacin, gentamicin, imipenem, levofloxacin, meropenem, ofloxacin, piperacillin, piperacillintazobactam, tetracycline, tobramycin, and trimethoprim-sulfamethoxazole. MIC was defined as the lowest drug concentration that prevented visible bacterial growth. Interpretative criteria for each drug tested were as in CLSI guidelines (8). A. lwoffii resistant to [greater than or equal to] 4 classes of drugs were defined as multidrug-resistant (MDR) isolates.

A. lwoffii isolates were genotyped by pulsed-field gel electrophoresis (PFGE) to determine their epidemiologic relatedness. Chromosomal DNA was digested with Sinai (9) and analyzed with a CHEF DR II apparatus (Bio-Rad Laboratories, Hercules, CA, USA). PFGE patterns were classified as identical, similar (differed by 1-3 bands), or distinct (differed by >4 bands) (10).

Among the 10 A. lwoffii isolates, 6 were susceptible to all drugs except cephalosporins (cefepime, cefotaxime, ceftazidime, and ceftriaxone) and aztreonam. The other 4 isolates were MDR: 3 were susceptible only to imipenem (MICs 1-4 [micro]g/mL), meropenem (MICs 1-2 [micro]g/mL), and amikacin (MICs 2-4 [micro]g/mL). The fourth MDR strain was susceptible to imipenem (MIC 2 [micro]g/mL), meropenem (MIC 2 [microg/mL), amikacin (MIC 4 [micro]g/mL), and ciprofloxacin (MIC 1 [micro]g/mL). Seven antimicrobial drug resistance profiles were detected (Table).

Macrorestriction analysis of the A. lwoffii isolates identified 8 distinct PFGE types. Two MDR strains (strains 2 and 3 in the Table), which were isolated from patients in different wards, and 2 non-MDR strains (strains 8 and 9), which were isolated from patients in the same ward, had similar PFGE pattems and identical resistance phenotypes. These findings suggest nosocomial transmission. Nine of the 10 patients survived after catheter removal or treatment with appropriate antimicrobial drugs. These results confirm that catheter-related A. Iwoffii bacteremia in immunocompromised hosts is associated with a low risk for death (4,6).

This study identified A. lwoffii MDR strains that cause bacteremia in immunocompromised catheterized patients. Our data are consistent with those of previous reports on the role of catheters as the principal source of A. lwoffii infections.

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References

(1.) Murray CK, Hospenthal DR. Treatment of multidrug resistant Acinetobacter. Curr Opin Infect Dis. 2005;18:502-6.

(2.) Bergogne-Berezin E, Towner KJ. Acinetobacter spp. as nosocomial pathogens: microbiological, clinical, and epidemiological features. Clin Microbiol Rev. 1996;9:148-65.

(3.) Valero C, Garcia-Palomo JD, Matorras P, Fernandez-Mazarrasa C, Gonzales-Fernandez C, Farinas MC. Acinetobacter bacteraemia in a teaching hospital, 1989-1998. Eur J Intern Med. 2001;12: 425-9.

(4.) Crowe M, Ispahani P, Humphreys H, Kelley T, Winter R. Bacteraemia in the adult intensive care unit of a teaching hospital in Nottingham, UK, 1985-1996. Eur J Clin Microbiol Infect Dis. 1998;17:377-84.

(5.) Seifert H, Strate A, Schulze A, Pulverer G. Vascular catheter-related bloodstream infection due to Acinetobacter johnsonii (formerly Acinetobacter calcoaceticus var. lwoffii): report of 13 cases. Clin Infect Dis. 1993;17:632-6.

(6.) Ku SC, Hsueh PR, Yang PC, Luh KT. Clinical and microbiological characteristics of bacteremia caused by Acinetobacter lwoffii. Eur J Clin Microbiol Infect Dis. 2000;19:501-5.

(7.) Domingo P, Munoz R, Frontera G, Pericas R, Martinez E. Community-acquired pneumonia due to Acinetobacter lwoffii in a patient infected with the human immunodeficiency virus. Clin Infect Dis. 1995;20: 205-6.

(8.) Clinical and Laboratory Standards Institute (CLSI). Performance standards for antimicrobial susceptibility testing: 15th informational supplement. CLSI/NCCLS M100-S15. Wayne (PA): The Institute; 2005.

(9.) Prashanth K, Badrinath S. Epidemiological investigation of nosocomial Acinetobacter infections using arbitrarily primed PCR and pulse field gel electrophoresis. Indian J Med Res. 2005;122:408-18.

(10.) Tenover FC, Arbeit RD, Goering RV, Mickelsen PA, Murray BE, Persing DH, et al. Interpreting chromosomal DNA restriction patterns produced by pulsed-field gel electrophoresis: criteria for bacterial strain typing. J Clin Microbiol. 1995;33:2233-9.

Address for correspondence: Antonio Carraturo, Laboratorio di Microbiologia, Ospedale Santa Maria Goretti, Azienda Unita Sanitaria Locale di Latina, Via Canova, 04100 Latina, Italy; email: [e-mail]

Luciano Tega, * Katia Raieta, ([dagger]) Donatella Ottaviani, ([dagger]) Gian Luigi Russo, ([dagger]) Giovanni Blanco, * and Antonio Carraturo *

* Ospedale Santa Maria Goretti, Latina, Italy; ([dagger]) lstituto di Scienze dell'Alimentazione, Avellino, Italy; and ([dagger]) stituto Zooprofilattico Sperimentale dell'Umbria e delle Marche, Ancona, Italy

Table. Antimicrobial drug susceptibility and pulsed-field gel
electrophoresis (PFGE) patterns of 10 Acinetobacter Iwoffii
strains, Italy, 2002-2005

                                     Drug ([dagger])

No.   Source *   AS   PI   PT   CE   CT   CA   CF   AT   CI   LE   OF

1     ICU        R    R    R    R    R    R    R    R    R    R    R
2     ICU        R    R    R    R    R    R    R    R    R    R    R
3     OW         R    R    R    R    R    R    R    R    R    R    R
4     ICU        R    R    R    R    R    R    R    R    S    R    R
5     ICU        S    S    R    S    S    R    R    R    R    R    R
6     ICU        R    S    S    S    R    R    R    S    S    S    S
7     UW         S    S    S    R    R    R    R    R    S    S    S
8     ICU        S    R    S    R    R    S    R    R    S    S    S
9     ICU        S    R    S    R    R    S    R    R    S    S    S
10    MW         S    S    S    S    S    R    S    R    S    R    R

                         Drug ([dagger])

No.   Source *   GM   TM   AM   TC   IP   MP   TS   Antibiotype   PFGE

1     ICU        R    R    S    R    S    S    R    a             A
2     ICU        R    R    S    R    S    S    R    a             B
3     OW         R    R    S    R    S    S    R    a             B
4     ICU        R    R    S    R    S    S    R    b             C
5     ICU        S    S    S    S    S    S    S    c             D
6     ICU        R    R    S    S    S    S    S    d             E
7     UW         S    S    S    R    S    S    S    e             F
8     ICU        S    S    S    S    S    S    R    f             o
9     ICU        S    S    S    S    S    S    R    f             G
10    MW         R    S    R    S    S    S    S    g             H

* ICU, intensive care unit; OW, orthopedic ward; UW, urologic
ward; MW, medical ward.

([dagger]) AS, ampicillin-sulbactam; PI, piperacillin;
PT, piperacillin-tazobactam; CE, cefopime; CT, cefotaxamine;
CA, ceftazidime; CF, ceftriaxone; AT, azteonam; CI, ciprofloxacin;
LE, levofloxacin; OF, ofloxacin; GM, gentamicin; TM, tobramycin;
AM, amikacin; TC, tetracycline; IP, imipenem; MP, meropenem;
TS, trimethoprim-sulfamethoxazole; R, resistant; S, suceptible.