Drug sensitivity patterns of streptococcus pneumoniae in the Maltese islands

Abstract

Streptococcus pneumoniae is the most common cause of community-acquired respiratory tract infections such as otitis media, sinusitis and pneumonia. Globally, pneumococcal diseases account for 1 to 2 million deaths annually in both extremes of age (in children less than 5 years and in adults over 60 years). Pneumococcal septicaemia is a major cause of infant mortality in developing countries, where it causes approximately 25% of all preventable deaths in children under the age of 5 and more than 1.2 million infant deaths per year. In countries that have a high prevalence of HIV-1 infection, there has been a significant increase in the rate of pneumococcal pneumonia and associated bacteraemia, and this increase has been most marked in young adults (Kadioglu, Weiser, & Paton, 2008). Streptococcus pneumoniae is supposed to be a very sensitive organism to routine antibiotics especially to penicillins. However, with the isolation of the first clinically significant penicillin-resistant pneumococcus in 1967, many studies from different parts of the world have reported an increasing emergence of this penicillin-resistant pneumococcus. At present there are not only reports of resistant strains of Str. pneumoniae to the beta-Iactam group of antibiotics, but there is also an emergence of multidrug-resistant strains (Chawla, Gurung, Mukhopadhya, & Bairy, 2010). According to EARSS statistics, in 2008, the highest levels of penicillin-non-susceptible Str. pneumoniae strains were found in Bosnia Herzegovina (55%), followed by Malta (47%) and Cyprus (43%). The highest levels of macrolide resistant Str. pneumoniae were found in Poland (50%), followed by Malta (35%) and Hungary (32%). These findings were quite alarming since they stated that the Maltese Islands have the secondhighest, drug-resistant Str. pneumoniae strains in Europe. In a study conducted by Micallef et al. in Malta, in 2002, a total of 74 Str. pneumoniae strains were tested for their sensitivity to penicillin, erythromycin, clindamycin, ceftriaxone and vancomycin. Thirty seven (50%) of the isolates were resistant to one or more of the antibiotics tested. Intermediate resistance to penicillin was seen in 20 (27%) of the isolates (fully penicillin-resistant isolates were not seen) while erythromycin resistance was detected in 31 % (4% intermediately, 27% fully resistant). Fourteen of the 23 erythromycin-resistant isolates were also fully resistant to c1indamycin. Resistance to ceftriaxone and vancomycin was not observed. The objective of this study was to review the susceptibility patterns of Str. pneumoniae through the testing of stored cultures for sensitivity of penicillin, erythromycin, clindamycin, ceftriaxone and vancomycin using Etests®. Thus, Str. pneumoniae sensitivity patterns could be characterized over a period from 2008 till 2010 and compared to previous data obtained from the study made by Micallef et. al. in Malta and other data obtained from European countries. This data builds a useful sensitivity profile of established antibiotics to Str. pneumoniae. Out of the 119 isolates of Str. pneumoniae tested in 2010, 5.04% (6/119) were totally resistant to penicillin, 21.01 % (25/119) were totally resistant to erythromycin and 15.97% (19/119) were totally resistant to c1indamycin. 10.08% of the isolates were intermediate to ceftriaxone - no totally resistant isolates to ceftriaxone were obtained. All isolates were totally sensitive to vancomycin. Multi-drug resistant (Le. resistance to penicillin, erythromycin and clindamycin) isolates accounted for 24.37% (20/119) of all pneumococci isolates. More importantly, a general shift towards the more resistant Mean Inhibitory Concentration (MIC) values was observed when a comparison was made between the study performed by Micallef et. al. in 2002 and this study performed in 2010. Thus, one can observe that Streptococcus pneumoniae in the Maltese Islands, has become more resistant in the past eight years. Increasing emergence of the resistant strains of Str. pneumoniae in the Maltese community set up, requires continuous monitoring and a restricted use of antibiotics to keep a check on its resistance pattern, for an effective treatment plan. In addition, vaccination schedules should be implemented to protect those at higher risks of contacting pneumococcal infections.