Epidemiological survey of penicillinase- producing neisseria gonorrhoeae (PPNG) in Zimbabwe

Abstract

The study involved an investigation into the plasmid types which confer resistance to penicillin in N. gonorrhoeae in Zimbabwe, and to determine the most occurring plasmid associated with PPNG. Specimens were collected from patients presenting with urethral discharge at chosen hospitals and clinics in Zimbabwe. These were then cultured on selective Thayer-Martin (TM) media. Presumptive gonococci were subjected to Gram stain, oxidase and carbohydrate fermentation tests. Beta-lactamase activity of the isolates was assessed by using commercial intralactam strips. Antibiotic sensitivity tests were done using discs incorporated with penicillin G, augmentin, erythromycin and tetracycline. Plasmid DNA was isolated using an alkaline selective denaturation technique that destroys chromosomal DNA whilst retaining small covalently closed DNA molecules. The DNA so obtained was checked for size, homogeneity and purity using agarose gel electrophoresis. The plasmid profiles were used to ascertain the most prevalent plasmid type which conferred resistance to penicillin in N. gonorrhoeae isolates. Four hundred and thirty six isolates of N. gonorrhoeae were isolated from the 865 specimens collected. Of these isolates 147 (34%) were R plasmid bearing. All beta-lactamase producing strains were resistant to penicillin G. In addition, seven non-beta-lactamase producing strains were also resistant to penicillin G, possibly indicating chromosomal resistance. Plasmid analyses indicated that of the 147 strains tested, 144 (98%) harboured the 2.6 Md cryptic plasmid, 56 (38%) the 3.2 Md plasmid, 66 (45%) the 4.5 Md plasmid. The 24.5 Md transfer plasmid existed in 61 (41%) of the strains. Eight isolates harboured both the 3.2 and 4.5 Md plasmids. The study demonstrated that resistance to penicillin in N. gonorrhoeae in Zimbabwe is equally confered by both the 3.2 Md and 4.5 Md plasmids.