MOLECULAR EPIDEMIOLOGY OF PENICILLIN-RESISTANT PNEUMOCOCCI ISOLATED IN NAIROBI, KENYA

A total of 26% of the pneumococci isolated from an outpatient clinic i n Nairobi, Kenya, during 1991 to 1992 had intermediate levels of penic illin resistance. Gene fingerprinting and DNA sequencing were used to distinguish the penicillin-binding protein (PBP) 1A, 2B, and 2X genes in 23 resistant isolates. Isolates were grouped into those that had id entical forms of each of the three PBP genes (fingerprint groups) and those that had identical rRNA gene restriction patterns (ribotypes). B oth methods divided the isolates into 11 groups. In a few cases, horiz ontal gene transfer appeared to have distributed an identical altered PBP gene into different pneumococcal lineages. Eight isolates were ind istinguishable by ribotyping or multilocus enzyme electrophoresis and contained identical PBP 1A genes. Although these isolates were therefo re members of the same clone, they were divided into two fingerprint g roups which contained different PBP 2X and 2B genes. Presumably, membe rs of this clone have acquired different altered PBP 2X and 2B genes o n two separate occasions. One of these fingerprint groups contained is olates of serotype 14, whereas the other contained isolates of both se rotypes 14 and 7. The identification of isolates in the latter group t hat are identical by all criteria, except serotype, implies the occurr ence of a change in serotype. The predominant serotypes of the penicil lin-resistant pneumococci from Nairobi were serotypes 14 and 19. In bo th cases, isolates of the same serotype which required the same MIC of penicillin were not members of a single clone, indicating that identi ty of serotype and MIC are not sufficient criteria for defining clones of resistant pneumococci even when the bacteria are isolated from a s ingle clinic.