title: Molecular characterization of penicillin non-susceptible Streptococcus pneumoniae isolated before and after pneumococcal conjugate vaccine implementation in Casablanca, Morocco.
abstract: BACKGROUND
  Streptococcus pneumoniae is a major cause of morbidity and mortality worldwide, especially among children and the elderly. The ability to effectively treat pneumococcal infection has been compromised due to the acquisition of antibiotic resistance, particularly to β-lactam drugs. This study aimed to describe the prevalence and molecular evolution of penicillin non-susceptible S. pneumoniae (PNSP) isolated from invasive diseases before and after pneumococcal conjugate vaccine implementation in Casablanca, Morocco.
  
  
  METHODS
  Isolates were obtained from the Microbiology Laboratory of Ibn Rochd University Hospital Centre of Casablanca. Serogrouping was done by Pneumotest Kit and serotyping by the Quellung capsular swelling. Antibiotic susceptibility pattern was determined by disk diffusion and E-test methods. The PNSP were analyzed by pulsed-field gel electrophoresis (PFGE) and by genotyping of pbp1a, pbp2b, and pbp2x genes.
  
  
  RESULTS
  A total of 361 S. pneumoniae isolates were collected from 2007 to 2014. Of these isolates, 58.7% were obtained before vaccination (2007-2010) and 41.3% after vaccination (2011-2014). Of the 361 isolates, 80 were PNSP (22.2%). Generally, the proportion of PNSP between pre- and post-vaccination periods were 31 and 13% (p = 0.009), respectively. The proportion of PNSP isolated from pediatric and adult (age > 14 years) patients decreased from 34.5 to 22.9% (p = 0.1) and from 17.7 to 10.2% (p = 0.1) before and after vaccine implementation, respectively. The leading serotypes of PNSP were 14 (33 vs. 57%) and 19A (18 vs. 14%) before and after vaccination among children. For adults, serotypes 19A (53%) and 23F (24%) were the dominant serotypes in the pre-vaccination period, while serotype 14 (22%) was the most prevalent after vaccination. There were 21 pbp genotypes in the pre-vaccination period vs. 12 for post-vaccination period. PFGE clustering showed six clusters of PNSP grouped into three clusters specific to pre-vaccination period (clusters I, II and III), two clusters specific to post-period (clusters V and VI) and a cluster (IV) that contained clones belonging to the two periods of vaccination.
  
  
  CONCLUSIONS
  Our observations demonstrate a high degree of genetic diversity among PNSP. Genetic clustering among PNSP strains showed that they spread mainly by a restricted number of PNSP clones with vaccine serotypes. PFGE clustering combined with pbp genotyping revealed that vaccination can change the population structure of PNSP.
authors.affiliation: Laboratoire de Microbiologie, Faculté de Médecine et de Pharmacie, Hassan II University of Casablanca, B.P 5696, Casablanca, Morocco. diawaraidris@gmail.com.|Service de Microbiologie, CHU Ibn Rochd, B.P 2698, Casablanca, Morocco. diawaraidris@gmail.com.
authors.forename: Idrissa
authors.initials: I
authors.lastname: Diawara
authors.affiliation: Laboratoire Polyvalent en Recherche et Développement, département de Biologie-Géologie, Faculté polydisciplinaire, Université Sultan Moulay Slimane, Beni Mellal, Morocco.
authors.forename: Abouddihaj
authors.initials: A
authors.lastname: Barguigua
authors.affiliation: Laboratoire de Microbiologie, Faculté de Médecine et de Pharmacie, Hassan II University of Casablanca, B.P 5696, Casablanca, Morocco.|Service de Microbiologie, CHU Ibn Rochd, B.P 2698, Casablanca, Morocco.
authors.forename: Khalid
authors.initials: K
authors.lastname: Katfy
authors.affiliation: Laboratoire de Microbiologie, Faculté de Médecine et de Pharmacie, Hassan II University of Casablanca, B.P 5696, Casablanca, Morocco.|Molecular Bacteriology Laboratory, Institut Pasteur du Maroc, Casablanca, Morocco.
authors.forename: Kaotar
authors.initials: K
authors.lastname: Nayme
authors.affiliation: Laboratoire de Microbiologie, Faculté de Médecine et de Pharmacie, Hassan II University of Casablanca, B.P 5696, Casablanca, Morocco.|Service de Microbiologie, CHU Ibn Rochd, B.P 2698, Casablanca, Morocco.
authors.forename: Houria
authors.initials: H
authors.lastname: Belabbes
authors.affiliation: Molecular Bacteriology Laboratory, Institut Pasteur du Maroc, Casablanca, Morocco.
authors.forename: Mohammed
authors.initials: M
authors.lastname: Timinouni
authors.affiliation: Laboratoire de Microbiologie, Faculté de Médecine et de Pharmacie, Hassan II University of Casablanca, B.P 5696, Casablanca, Morocco.|Service de Microbiologie, CHU Ibn Rochd, B.P 2698, Casablanca, Morocco.
authors.forename: Khalid
authors.initials: K
authors.lastname: Zerouali
authors.affiliation: Laboratoire de Microbiologie, Faculté de Médecine et de Pharmacie, Hassan II University of Casablanca, B.P 5696, Casablanca, Morocco.|Service de Microbiologie, CHU Ibn Rochd, B.P 2698, Casablanca, Morocco.
authors.forename: Naima
authors.initials: N
authors.lastname: Elmdaghri
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D044822:Biodiversity; D002648:Child; D002675:Child, Preschool; D005260:Female; D005838:Genotype; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D009018:Morocco / Q000453:epidemiology; D010406:Penicillins / Q000494:pharmacology; D011008:Pneumococcal Infections / Q000453:epidemiology / Q000382:microbiology*; D022242:Pneumococcal Vaccines / Q000276:immunology*; D065288:Serogroup; D013296:Streptococcus pneumoniae / Q000145:classification* / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D018074:Vaccines, Conjugate / Q000276:immunology; D055815:Young Adult; D018440:beta-Lactam Resistance
chemical_list: D000900:Anti-Bacterial Agents; D010406:Penicillins; D022242:Pneumococcal Vaccines; D018074:Vaccines, Conjugate
keywords: Antibiotic resistance; Invasive pneumococcal disease; PFGE; Penicillin-binding proteins; Serotypes; Streptococcus pneumoniae; β-lactams