Drug Resistant Streptococcus pneumoniae (DRSP) in the Maltese Islands

Robert Cassar BSc (Hons), MSc Assistant Principal Medical Laboratory Scientist, Bacteriology Laboratory, Department of Pathology, St. Luke‘s Hospital, Gwardamangia, Malta Email: [email protected] Abstract The DRSP prevalence rate for the Maltese Islands was investigated. Consecutive samples were obtained, both from adults and children, from September 2000 through April 2002. Penicillin-intermediately-resistant isolates amounted to 27%, erythromycin-resistant isolates 31%, and clindamycin-resistant isolates 19%. The oxacillin disk was found to be an effective screening method for the detection of penicillin resistance. An association was found in patients who had DRSP, as well as diabetes and/ or cardiovascular disease. Finally, an investigation of the local antibiotic consumptions over the period 1997-2000, for the National Health Service was conducted. The highest consumption rates were obtained with co-amoxiclav, amoxicillin, erythromycin, cephalexin and ciprofloxacin. The results obtained here call for more judicious use of antibiotics. In addition, the setting up of a local DRSP surveillance unit is mandatory. Moreover, the use of molecular techniques to investigate specific genes, such as ermAM and mefE associated with macrolide-resistance, should be introduced as part of investigational laboratory work. Introduction The first report of acquired bacterial resistance, according to LP Garrod, dates back to 1937, when a Royal Navy surgeoncommander, TF Crean, observed a number of refractory cases of gonorrhoea in a group of patients treated with the sulphonamide, sulphanilamide (Prontosil). Selection of bacterial resistance started on a global scale in the early 1940s, when the first penicillins were introduced in clinical practice. Alexander Tomasz described the first penicillin-resistant pneumococcal isolate, (capsular type 4), isolated from the throat of a healthy 3-year-old boy in the village of Anguganak, New Guinea, with a population of 507, on April 15, 1969. However, in 1967, Hansman and Bullen described a patient in Sydney, with hypogammaglobulinemia and bronchiectasis, in whom a strain of pneumococcus (Type 23) that was relatively insensitive to penicillin, was isolated from the sputum. Resistance to ß-lactams in the pneumococcus is mediated via an intrinsic alteration of high molecular weight penicillinbinding proteins (PBPs). Cephalosporin resistance is due to alterations in PBP1a and 2x. Resistance mechanisms to macrolide, lincosamide (e.g. clindamycin) and streptograminB (MLS B ) antibiotics mainly involve: a) Target site modification (encoded by ermAM), conferring broad cross-resistance to MLS B antibiotics and/or b) Active efflux pump alteration (encoded by mefE). This type of resistance is confined to structurally-related antibiotics only.