Carbapenem-resistant Acinetobacter baumannii producing the carbapenemase OXA-23 in Tunisia

To analyze the mechanisms of resistance to carbapenems among imipenem resistant A. baumannii recovered from different wards at Charles Nicolle Hospital. From January to December 2007, 50 carbapenem-resistant A. baumannii isolates were recovered from hospitalized patients. MICs were performed by agar dilution method and interpreted according to CLSI guidelines. Metallo-beta-lactamase production was evaluated using imipenem-EDTA disk synergy test. PCR and DNA sequencing targeting blaOXA genes were performed and pulsed field gel electrophoresis was used for epidemiologic study. Most of the isolates were obtained from patients hospitalized in surgery [62%] and Intensive Care Units [22%]. All strains showed high level of resistance to ticarcillin [MIC50 > 2048micro g/ml], ticarcillin-clavulanic acid [MIC50 >1024micro g/ml], aztreonam [MIC50 = 512micro g/ml], ceftazidim [MIC50 = 512micro g/ml], imipenem [MIC50 = 512micro g/ml], meropenem [MIC50 =128micro g/ml] and cefepime [MIC50 = 256micro g/ml]. Metallo-beta-lactamase production was negative for all isolates. The co-existence of blaOXA-51-like/ blaOXA-23-like was detected in 82% [n= 41]. The genes blaOXA- 24-like and blaOXA-58-like were not found in any isolate. All isolates harboured a blaOXA-51-like gene. Sequencing confirmed the presence of blaOXA-23 and blaOXA-69 genes. Eight distinct patterns were observed [A: 41 isolates, B: 1 isolate, C: 1 isolate, D: 1 isolate, E: 1 isolate, F: 2 isolates, G: 1 isolate, H: 2 isolates]. Production of OXA-23 was the important mechanism of resistance to carbapenem among A. baumannii. Strengthening of prevention measures are required to control further spread of carbapenemases in Tunisia

Hospital acquired outbreak of methicillin-resistant staphylococcus aureus infection initiated by a health care worker

Methicillin-resistant Staphylococcus aureus [MRSA] has become an increasingly important pathogen leading to hospital acquired infections. This study was done to confirm an outbreak of MRSA suspected at Charles Nicolle Hospital. From 26 April to 11 June 2002, six patients hospitalized in the dermatologic ward at Charles Nicolle hospital of Tunisia have developed infections caused by MRSA. An investigation of the outbreak has been detected a nasal carriage nurse. This carrier received topical mupirocin treatment to decolonize the anterior nares and the outbreak was stopped without further incident. Typing of the MRSA strains by pulsed field gel electrophoresis demonstrated the same pulsotype shared by all isolates showing that MRSA isolates belonged to a single clonal type responsible of outbreak. Colonized nurse was the source of MRSA dissemination. This report illustrates the risk of nosocomial outbreak linked to cares delivered by the staff personnel. More sensibilisation and the respect of strict hygienic measures should be emphasized

[Spread of multidrug resistant acinetobacter baumannii in a teaching hospital]

A. baumannii is an important opportunistic pathogen widely distributed in the hospital environment and responsible for a variety of nosocomial infections especially in patients from intensive care units. We describe an outbreak of Acinetobacter baumannii [16 stains] in 3 intensive care units [I, II, III] at Charles Nicolle hospital of Tunis over a 5 month period [March to July 2005]. The antimicrobial susceptibility was determined by disc diffusion test and the genetic relatedness of isolates was done by Random Amplified Polymorphic DNA [RAPD] analysis. Two strains not related to the outbreak were used for the discrimination of the technique. Samples were collected from blood [44%], materials [31%], pus [6.5%], urines [6.5%] and respiratory tract [12.5%]. Antibiotic resistance pattern showed 2 different profiles. However, molecular typing of isolates revealed 3 distinct profiles [A, B, C] represented respectively by 8, 7 and one isolates. The major profile was the profile A found in 5 patients and in materials. It was appeared firstly in intensive care unit I. then in the 2 other units [II and Ill]. The profile B was observed also in the 3 units. However, the profile C was found in one patient in unit I. These data emphasize the need for active surveillance for multidrug-resistant Acinetobacter baumannii, and the value of molecular typing of strains in hospital settings to investigate spread of infection