Increasing penicillin resistance in pneumococci isolated from cerebrospinal fluid samples: Fifteen-year experience from a teaching hospital

Journal of Microbiology and Infectious Diseases / JMID 2014; 4 (4): 136-140 doi: 10.5799/ahinjs.02.2014.04.0156 RESE ARCH ARTICLE Increasing penicillin resistance in pneumococci isolated from cerebrospinal fluid samples: Fifteen-year experience from a teaching hospital Filiz Pehlivanoğlu, Gönül Şengöz, Sevtap Gürsoy Department of Clinical Microbiology and Infectious Diseases, Haseki Training and Research Hospital, Istanbul, Turkey. ABSTRACT Objective: There have been prominent changes in evaluation of resistance patterns of pneumococci and breakpoint values in recent years. We aimed to investigate the penicillin sensitivity of pneumococcal strains isolated from the cerebrospinal fluid specimens between the years 1997-2011 in our hospital and determine the MIC values under the light of these changes. Methods: Identification of pneumococci was made with conventional methods in patients with meningitis. MIC values for penicillin G were investigated by E test method in all strains. MIC values of pneumococci strains were evaluated according to values determined by CLSI for meningitis isolates in 2008. Results: A total of 57 strains were investigated in this study. The MIC range for penicillin was 0.016 - 0.75 μg/ml in S. pneumoniae strains. Seventy five percent of the strains were sensitive and eight strains (14%) had resistance. MIC50 value was sensitive, and a MIC90 value was resistant. The first resistant strain was detected in 2000, and three strains were resistant in the last year. When examined over the years increased resistance was 5.3% in the first five-year period seems to be 28.6% in the last five-year period. Conclusions: Knowledge on penicillin resistance patterns and surveillance is very important in the empirical treatment in pneumococcal meningitis. J Microbiol Infect Dis 2014; 4(4): 136-140 Key words: S. pneumoniae, penicillin resistance, CSF, breakpoint. BOS’tan izole edilen pnömokok suşlarında penisilin direncinin artışı: Bir eğitim hastanesinden 15 yıllık tecrübe ÖZET Amaç: Son yıllarda pnömokok bakterilerine direncin değerlendirilmesinde ve eşik değerlerinde büyük değişimler meydana geldi. Bu değişimler ışığında hastanemizde 1997-2011 yıllarında beyin omurilik sıvısı (BOS) örneklerinden izole edilen pnömokok suşlarında penisilin duyarlılıklarındaki değişimin araştırılması amaçlandı. Yöntemler: Tümü menenjitli hastalardan izole edilen pnömokokların tanımlamaları konvansiyonel yöntemlerle yapıldı. Tüm suşlarda penisilin G için MİK değerleri E test yöntemiyle araştırıldı. 2008 yılından itibaren pnömokoklarda penisilin MİK sınır değerleri, CLSI rehberine göre BOS izolatlarında ≤0,06 μg/ml duyarlı ve ≥0,12 μg/ml dirençli olarak değiştirildi. Bulgular: Çalışmanın kapsadığı dönemde toplam 57 suş araştırmaya dahil edildi. S. pneumoniae suşlarında, penisilin için MİK aralığı 0,016-0,75 μg/ml arasında bulundu. Suşların %75’i duyarlı, sekizi (%14) dirençli olarak tespit edildi. MİK50 değeri duyarlı, MİK90 değeri ise dirençli olarak saptandı. İlk dirençli suş 2000 yılında saptanırken son yıl ise suşların üçü dirençli bulundu. Yıllar içinde direnç artışı irdelendiğinde ilk beş yıllık periyotta %5,3 iken son beş yıllık periyotta %28,6 olduğu görülmektedir. Sonuç: Pnömokok menenjitlerinde penisilin direncinin bilinmesi ve takip edilmesi ampirik tedavi açısından büyük önem taşımaktadır. Anahtar kelimeler: S. pneumoniae, penisilin direnci, BOS, sınır değer. Correspondence: Filiz Pehlivanoğlu, Department of Clinical Microbiology and Infectious Diseases, Haseki Training and Research Hospital, İstanbul, Turkey Email: Received: 15 February 2014, Accepted: 30 November 2014 Copyright © Journal of Microbiology and Infectious Diseases 2014, All rights reserved Pehlivanoğlu F, et al. Penicillin resistance in pneumococci INTRODUCTION Streptococcus pneumoniae which was first described in 1880, is still an important cause of mortality and morbidity globally. Pneumococcal meningitis is a severe form of meningitis with devastating sequela and frequent recurrences, as well as being a high-risk disease particularly for patients with diabetes or other diseases that weaken the immune system, with a mortality that is nearly equal to that in the pre-antibiotic era.1 Although introduction of penicillin into clinical practice opened a new epoch in the treatment of diseases caused by S. pneumoniae, the first resistant isolate was reported in 1967, and other reports of resistant strains followed this from all around the world.2 Until 1980, this resistance was both rare and moderate without clinical failure in penicillin treatment. The epidemics in 1980s with resistant S. pneumoniae strains and high-levels of resistance with clinical treatment failures brought this issue into the light once again. Especially the high levels of resistance detected in some regions of the world have brought attentions to these severe, life-threatening infections. Great changes have occurred in resistance patterns of pneumococci and break point values in recent years. MIC values of S. pneumoniae strains isolated from the cerebrospinal fluid (CSF) in the last 15 years were evaluated according to new criteria in the present study. METHODS Penicillin resistance of S. pneumonia was evaluated retrospectively in Haseki Training and Research Hospital between 1997 and 2011. CSF samples 137 were cultured in blood culture test tubes (BacT Alert BioMerieux, France) and chocolate agar culture media and incubated at 37°C in 5% CO2 containing incubator overnight. Identification of the colonies were done according to colony morphology, Gram staining and optochin sensitivity. Colonies with lancet-shaped Gram-positive cocci, causing α-hemolysis at 5% sheep blood agar culture media, sensitive to optochin and dissolving in bile were considered as S. pneumoniae. MIC values for penicillin were determined with E test (AB Biodisk, Solna, Sweden). These MIC values were re-evaluated according to new criteria determined by Clinical and Laboratory Standards Institute (CLSI) for meningitis isolates (≤0.06 μg/ml sensitive and ≥0.12 μg/ml resistant) in 2008.3 RESULTS A total of 57 pneumococci were isolated from CSF samples in the Microbiology Laboratory. The yearly distribution of S. pneumoniae isolates are shown in Figure 1. Two peaks of isolated pneumococci strains, one in 2000 and the other in 2002 are observed. MIC range for penicillin was determined as 0.016-0.75 μg/ml (Table 1). Eight strains were resistant to penicillin (14%) and 44 strains (77.1%) were sensitive (Figure 1). Five strains (8.7%) were between the ranges for sensitive and resistant. The first resistant strain was isolated in the year 2000. A MIC90 value of 0.19 μg/ml was found and a MIC50 value of 0,016 μg/ml was detected in all isolates. When examined over the years increased resistance was 5.3% in the first five-year period seems to be 28.6% in the last five-year period (Figure 2). Figure 1. Yearly distribution of total and resistant S. pneumoniae strains iso (...truncated)