HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Orafu, C. Articles by Hopkins, M. Search for Related Content PubMed PubMed Citation Articles by Orafu, C. Articles by Hopkins, M.

Perianal Versus Anorectal Specimens: Is There a Difference in Group B Streptococcal Detection?

From the Department of Obstetrics and Gynecology, Aultman Hospital, Canton, Ohio; and Northeastern Ohio Universities College of Medicine, Rootstown, Ohio.

Address reprint requests to: Michael Hopkins, MD, Aultman Hospital, Department of Obstetrics and Gynecology, 2600 Sixth Street, Canton, OH 44710; E-mail: bschmaltz{at}aultman.com.

	ABSTRACT

TOP ABSTRACT MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
OBJECTIVE: To investigate whether specimens obtained from the perianal area have a Group B streptococcal culture detection rate similar to anorectal specimens.

METHODS: This is a prospective cohort study at a tertiary care university-affiliated teaching hospital. A total of 136 pregnant women between 33 and 40 weeks’ gestation were recruited. Three samples for Group B streptococcal culture detection were obtained from each subject in the following order: perianal sample, vaginoperianal sample, and an anorectal sample. The women were asked to rank their pain or discomfort with obtaining the anorectal sample. The vaginoperianal specimen is the standard sample obtained from antepartum patients in this clinic, and, therefore, it serves as the control.

RESULTS: Of the 136 subjects, 26.5% of the control, vagino-perianal samples were positive for Group B streptococcal culture. In comparison, 27.2% of the anorectal specimens and 28.7% of the perianal specimens were positive for Group B streptococcal culture. There was no statistically significant difference in the detection of Group B streptococcal culture among the three sample sites. Evaluation of the pain experienced with an anorectal sampling showed that 68% of subjects ranked their pain between mild to moderate, and 5% noted severe pain.

CONCLUSION: The Group B streptococcal detection rate was not different among the three sampling sites. Therefore, pregnant women do not need to be subjected to the additional pain of anorectal sampling to detect Group B Streptococcus.

Group B streptococcal infections are a leading cause of neonatal mortality and morbidity. Group B streptococcal sepsis affects approximately two to three of every 1000 newborns. Research done in the 1980s demonstrated that antibiotic prophylaxis given to mothers colonized with Group B Streptococcus was effective in preventing newborn infections.¹ In 1994, the Centers for Disease Control and Prevention prepared draft guidelines for Group B streptococcal prophylaxis. By 1996, consensus guidelines were issued by the ACOG, the American Academy of Pediatrics, and the Centers for Disease Control and Prevention. These guidelines recommended that practicing physicians use either a screening-based or risk-based approach to select patients for antibiotic prophylaxis during labor.² Studies indicate that 10–30% of pregnant women are colonized with Group B Streptococcus in the gastrointestinal or genital tract³ and that colonization is transient with women often becoming recolonized with a different serotype.⁴

Multiple studies have shown an increased detection rate of Group B streptococcal carriers when obtaining samples from both vaginal and anorectal sites as opposed to obtaining samples from either site alone.^4–6 A MEDLINE enquiry for the years 1996–2000 using the search words "Group B Streptococcus," "pregnancy," "neonatal infections," and "Streptococcus" revealed no studies that addressed the detection rate of Group B Streptococcus using perianal samples. A vaginal sample is obtained from the lower third of the vagina. An anorectal sample is taken from the perianal surface going through the anal sphincter and entering the rectum. A perianal sample is obtained from the perianal surface only; neither the anal sphincter nor the rectum is entered.

All of the pregnant women in our community hospital obstetric clinic are currently screened for Group B Streptococcus by obtaining both vaginal and perianal samples. Obtaining anorectal samples is perceived by the physicians as well as the nurses working in the clinic as being very painful and uncomfortable for the patient. We use the Centers for Disease Control and Prevention screening protocol for Group B streptococcal prophylaxis. This prospective cohort study was designed to address three questions:

1. Is there any difference in the detection rate of Group B Streptococcus in pregnant women using perianal cultures compared with anorectal cultures?
   
2. What is the perceived discomfort associated with anorectal sampling?
   
3. Are there any demographic or behavioral variables that are associated with a higher Group B streptococcal carrier status in our patient population?
   

	MATERIALS AND METHODS

TOP ABSTRACT MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Our hospital is a tertiary care university-affiliated teaching hospital with approximately 2500 deliveries per year. Between December 1999 and February 2001, 200 pregnant women attending the clinic between 33 and 40 weeks’ gestation were invited to participate in the study. Four patients declined because of time constraints, one patient declined for religious reasons, and three patients declined for unspecified reasons. Fifty-six patients declined because of concern over pain with anorectal cultures, and this represents 28% of all patients invited to participate. A total of 136 patients were in the study group. Three samples were obtained from all subjects. Five obstetric-gynecology residents and one nurse practitioner at our teaching hospital obstetric clinic participated in obtaining the cultures for the study. All clinicians were oriented to the study, and collection techniques were standardized.

The perianal sample was the first sample obtained. It was obtained from the perianal surface only; neither the anal sphincter nor the rectum was entered. The second sample obtained was the vaginoperianal sample. This was a sample from the vagina and from the perianal area. It was obtained using two different swab tips. Both swabs were placed in the same transport media. The final sample was the anorectal sample. The vaginoperianal region is the standard site for obtaining samples for Group B streptococcal detection in our obstetric clinic antepartum patients. Therefore, samples obtained from this site served as the control for this study.

All samples were sent to our hospital-based microbiology laboratory in Modified Stewart Transport Media (Becton Dickinson Microbiology Systems, Cockeysville, MD). They were then placed on LIM Broth Media (Becton Dickinson Microbiology Systems), a selective broth medium (medium that enhances the growth of Group B Streptococcus better than agar medium and is supplemented with antibiotics to inhibit the growth of organisms other than Group B Streptococcus). The laboratory staff was blinded to the site from which the sample was obtained.

The clinician obtaining the cultures verbally administrated a 14-question survey. Demographic, personal hygiene, as well as pain perception questions were read to the subjects and the subjects’ answers recorded by the interviewer.

Power analysis was done with SamplePower 1.0 (SPSS Inc., Chicago, IL). Before the study, a power analysis indicating a sample size of 115 would have a power of 80% to yield a statistically significant result ( = 0.05) if 15% of the pairs showed a positive culture for the control method of specimen collection only and 30% of the pairs showed a positive culture for the anorectal or perianal method of specimen collection only. Statistical analyses were done with SYSTAT 9 (SPSS Inc., Chicago, IL). McNemar test for paired proportions was used to test the relationship between the three methods of specimen collection and whether or not the specimen tested positive or negative. The McNemar test is a modification of the ² test that takes into account the matching of samples. The ordinary ² assumes independence of sampling and cannot be used when samples are matched. The McNemar test is used for two related measures on the same sample or situations where each individual measurement in one sample can be paired with a particular measurement in the other sample.

The Aultman Health Foundation Human Research Review Board approved the subjects’ rights aspects of the study. Written informed consent was obtained from all subjects. All procedures were in accordance with the ethical standards for human experimentation established by the Declaration of Helsinki.

	RESULTS

TOP ABSTRACT MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Our population consisted of younger women with 98% being under the age of 40 and 65% between 20 and 29 years. The majority of patients were of lower parity with 39% being nulliparous and 32% being primiparous. Single women were 74% of our study group. There was little ethnic diversity with 73% being white, 25% black, and 2% from other ethnic groups. Smokers made up 44% of our study population. Ninety-eight percent of the patients completed their education to at least the ninth grade.

The comparison of the Group B streptococcal detection rates from the three sampling sites is presented in Table 1. There were no statistically significant differences in Group B streptococcal detection rate for the three sites of specimen collection. For the samples from the vaginoperianal region, 26.5% (95% confidence interval [CI] 18.2, 35.7) were found to be positive for Group B Streptococcus. Likewise, 27.2% (95% CI 18.8, 36.5) of the samples from the anorectal region and 28.7% (95% CI 20.1, 38.0) of the samples from the perianal region tested positive for Group B Streptococcus.

Table 2 presents the Group B streptococcal detection rate associated with certain risk factors. The number of positive Group B streptococcal samples was standardized and expressed as the percent Group B streptococcal positive specimens with the corresponding 95% CI. The Group B streptococcal detection rate was not significantly associated with ethnic background, marital status, smoking status, age, or education level. Data on the detection rate of Group B Streptococcus for behaviors associated with Group B streptococcal disease are also presented in Table 2. Perineal hygiene and its possible effects on Group B streptococcal detection was examined. Subjects were asked what material they used to clean their perineum with after bowel movements, as well as what direction they wiped their perineum after urination and bowel movement. The number of times a subject had sexual intercourse in the past 2 weeks before obtaining cultures was also assessed. For these behaviors, the Group B streptococcal detection rate was not significantly associated with the kind of hygiene products used for wiping after a bowel movement, the direction of wiping after urination or a bowel movement, or coital frequency.

	DISCUSSION

TOP ABSTRACT MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Our study failed to detect a difference in the Group B streptococcal positive rate between perianal and anorectal specimens. Our study supports the hypothesis that in obstetric patients, perianal cultures for Group B Streptococcus are a reasonable alternative to anorectal cultures for the detection of asymptomatic Group B streptococcal carriage.

Patients perceive obtaining anorectal specimens as uncomfortable and will avoid them if possible. This is demonstrated by high subject pain scores associated with obtaining anorectal specimens as well as the high number of eligible patients who declined to participate in our study because of the fear of perceived discomfort from obtaining anorectal specimens. Based on our study, pregnant women in our population do not need to be subjected to the discomforts of anorectal cultures to optimize Group B streptococcal detection. Another interesting finding in our study is that neither the number of sexual encounters nor the different methods of perineal hygiene were found to be contributing factors in Group B streptococcal detection.

In our population, there were no demographic characteristics found that placed patients at a greater risk for Group B streptococcal carriage. Previous studies have found black race, sexual activity, age less than 21, and low parity⁷ to be risk factors for higher Group B streptococcal carriage. We showed no population difference with regard to these published risk factors. This may be one of the limiting constraints of our smaller sample size.

In conclusion, Group B streptococcal infections continue to be a leading cause of neonatal mortality and morbidity. Adherence to the 1996 consensus guidelines has greatly decreased the incidence of neonatal Group B streptococcal sepsis across the United States. We have shown that in our community hospital obstetric clinic population, perianal cultures are just as effective as anorectal cultures in screening for Group B streptococcal carriage. Further studies are needed to determine if this also applies to other populations.

	Footnotes

 
Financial support was provided by the Aultman Health Foundation.

PII S0029-7844(02)01979-8

Received October 10, 2001. Received in revised form January 17, 2002. Accepted February 7, 2002.

	REFERENCES

TOP ABSTRACT MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
1. Boyer KM, Gotoff SP. Prevention of early onset neonatal group B streptococcal disease with selective intrapartum chemoprophylaxis. N Engl J Med 1986;314:1665–9.[Abstract]

2. Centers for Disease Control and Prevention. Prevention of group B streptococcal disease. A public health perspective. MMWR 1996;45(RR-7):1–24.[Medline]

3. Schuchat A, Wenger JD. Epidemiology of group B streptococcal disease. Risk factors, prevention strategies and vaccine development. Epidemiol Rev 1994;16:374–403.[Free Full Text]

4. Hoogkamp-Korstanje JA, Gerards LJ, Cats BP. Maternal carriage and neonatal acquisition of group B streptococci. J Infect Dis 1982;145:800–3.[Medline]

5. Dillon HC, Gray E, Pass MA, Gray BM. Anorectal and vaginal carriage of group B streptococci during pregnancy. J Infect Dis 1982;145:794–9.[Medline]

6. Quinlan JD, Hill DA, Maxwell BD, Boone S, Hoover F, Lense J. The necessity of both anorectal and vaginal cultures for group B streptococcus screening during pregnancy. J Fam Pract 2000;49:447–8.[Medline]

7. McKenna DS, Iams JD. Group B streptococcal infections. Sem Perinatol 1998;22:267–76.

This article has been cited by other articles:

				M. A. Turrentine and M. M. Ramirez Recurrence of Group B Streptococci Colonization in Subsequent Pregnancy Obstet. Gynecol., August 1, 2008; 112(2): 259 - 264. [Abstract] [Full Text] [PDF]

				W. E. Jamie, R. K. Edwards, and P. Duff Vaginal-Perianal Compared With Vaginal-Rectal Cultures for Identification of Group B Streptococci Obstet. Gynecol., November 1, 2004; 104(5): 1058 - 1061. [Abstract] [Full Text] [PDF]

				R. S. Gibbs, S. Schrag, and A. Schuchat Perinatal Infections Due to Group B Streptococci Obstet. Gynecol., November 1, 2004; 104(5): 1062 - 1076. [Abstract] [Full Text] [PDF]

				S. M. Hansen and U. B. S. Sorensen Method for Quantitative Detection and Presumptive Identification of Group B Streptococci on Primary Plating J. Clin. Microbiol., April 1, 2003; 41(4): 1399 - 1403. [Abstract] [Full Text] [PDF]

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Orafu, C. Articles by Hopkins, M. Search for Related Content PubMed PubMed Citation Articles by Orafu, C. Articles by Hopkins, M.