Repetitive Extragenic Palindromic Polymerase Chain Research Articles

Fecal and oral shedding of Helicobacter pylori from healthy infected adults.

Helicobacter pylori commonly infects humans; however, its mode of transmission remains unknown. To determine how humans-the primary host for H pylori-shed the organism into the environment. Controlled clinical experimental study conducted from February through December 1998. Clinical research unit of a hospital in northern California. Sixteen asymptomatic H pylori-infected and 10 uninfected adults. A cathartic (sodium phosphate) and an emetic (ipecac) were given to all infected subjects and an emetic was given to 1 uninfected subject. Confirmed H pylori isolates cultured from stool, air, or saliva before and after catharsis and emesis and from vomitus during emesis. Isolates were fingerprinted using repetitive extragenic palindromic (REP) polymerase chain reaction and species identity was confirmed by sequencing the 16s ribosomal RNA gene. All vomitus samples from infected subjects grew H pylori, often in high quantities. Air sampled during vomiting grew H pylori from 6 (37.5%) of the 16 subjects. Saliva before and after emesis grew low quantities of H pylori in 3 (18.8%) and 9 (56.3%) subjects, respectively. No normal stools and only 22 (21.8%) of 101 induced stools grew the organism, although 7 (50.0%) of 14 subjects had at least 1 positive culture (2 stool culture samples were contaminated by fungus and were not included). Fingerprints of isolates within subjects were identical to one another but differed among subjects. No samples from uninfected subjects yielded H pylori. Helicobacter pylori can be cultivated uniformly from vomitus and, occasionally, from saliva and cathartic stools. The organism is potentially transmissible during episodes of gastrointestinal tract illness, particularly with vomiting.

When should healthcare workers be screened for methicillin-resistant Staphylococcus aureus?

The role of screening of healthcare workers (HCWs) in the control of methicillin-resistant Staphylococcus aureus (MRSA) is controversial. It is recommended in guidelines by expert groups in both North America and the United Kingdom, although the role of MRSA carriage by HCWs in outbreaks is not clearly defined. The present report describes the spread of a distinct strain of MRSA to patients by a single HCW on three separate occasions over 27 months. The isolates from this HCW and patient contacts were shown to be indistinguishable by antibiogram and repetitive extragenic palindromic polymerase chain reaction (REP/PCR); none were typeable by lytic phage-typing. Throat carriage of the MRSA probably recurred in this HCW, despite attempts to eradicate it on three occasions. Over the same period, nine other small clusters were seen in the Oxford Hospital Group, involving 66 patients and 22 HCWs colonized, or occasionally infected, with a variety of MRSA strains. In none of these instances could HCWs be implicated in the initiation of an outbreak. The advantages of a screening policy include the determination of the full extent of MRSA-colonization and work exclusion; the disadvantages include detection of transient nasal carriage, disruption of staff routine and stigmatization. Screening of HCWs can be a valuable tool in the control of MRSA outbreaks but it should be used selectively. This strategy remains an important part of a control programme.

Characterization of Streptococcus pneumoniae from human immunodeficiency virus--seropositive patients with acute and recurrent pneumonia.

Thirty-two isolates of clinically significant Streptococcus pneumoniae from 11 human immunodeficiency virus (HIV)-seropositive patients with single or multiple episodes of pneumonia were characterized by antibiotic susceptibility testing, serotyping, ribotyping, and repetitive extragenic palindromic polymerase chain reaction (REP-PCR). The isolates comprised 10 serotypes, 12 ribotyping patterns, and 12 REP-PCR patterns. There was close but not absolute correlation between techniques. By combining these characterization methods, 14 strains were identified. Five strains were found in > 1 patient, suggesting their frequent occurrence in this population. Two isolates of different serotype from 1 patient were highly related by ribotyping and REP-PCR, suggesting possible in vivo serotype change. Acute infection was associated with single strains or coinfection by distinct strains. Recurrent pneumonia was identified as relapse with the same strain or reinfection with new strains. The molecular characterization of pneumonococci from HIV-seropositive persons refines our understanding of pneumonococcal infection in these patients.