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GROUP G STREPTOCOCCI

THE introduction of coagglutination and latex

agglutination grouping reagents, by facilitating identificationof beta-haemolytic streptococci, may have contributed togreater awareness of the lesser beta-haemolytic streptococcalpathogens such as groups C and G. Group G streptococcioccur as part of the normal flora of the skin and upperrespiratory, gastrointestinal, and female genital tracts, andinfections are often associated with these sites. As early as1935 Lancefield and Hare2 recognised their ability to causepuerperal sepsis. Since then they have been associated with awide range of infections in all age groups.Although group B streptococci are the main streptococcal

pathogens of the newborn, group G streptococci can producea similar pattern of disease, with respiratory distress,bacteraemia, and hypotension. 3,4 The organisms are acquiredfrom the mother’s genital tract and infection is associatedwith prolonged rupture of membranes. Little is known aboutthe prevalence of group G streptococcal carriage in pregnantwomen.

Lam and BayerS have reviewed their own and others’experience of serious adult group G streptococcal sepsis.Bacteraemia, endocarditis, and septic arthritis appear to bethe most common infections Beta-haemolytic streptococcicause infective endocarditis far less often than do alpha-haemolytic streptococci, but group G streptococci seem tocause most of these cases.7,8 Group G streptococcalendocarditis is a disease of the middle aged and elderly,usually involving mitral or aortic valves.One interesting feature of group G streptococcal

endocarditis and arthritis is the discrepancy that often existsbetween in-vitro antibiotic sensitivity and the clinical

response to chemotherapy. Standard antibiotic sensitivitytests (disc diffusion or minimum inhibitory concentrations)measure bacterial inhibition. These show group G

streptococci to be sensitive to both beta-lactam antibiotics andto the alternatives, such as vancomycin, erythromycin, andclindamycin, that must be considered in cases of penicillinallergy. With more stringent tests of bactericidal function, amore complex pattern emerges. Group G streptococci arerelatively resistant to killing by erythromycin and

clindamycin.4 Noble et al9 described tolerance to both

benzylpenicillin and vancomycin with a minimum

bactericidal/inhibitory ratio of 32 or more. Rolston andothers were unable to confirm this,’° but Lam and BayerS didshow poor killing of high numbers of stationary-phaseorganisms by benzylpenicillin. This could be relevant toinfective endocarditis. Where patients do not respond to highdose therapy with a suitable beta-lactam antibiotic such asbenzylpenicillin, combination therapy with an

1. Barnham M. The gut as a source of the hemolytic streptococci causing infection insurgery of the intestinal and biliary tracts. J Infect 1983, 6: 129-39.

2. Lancefield RC, Hare R. The serological differentiation of pathogenic and non-pathogenic streptococci from parturient women. J Exp Med 1935; 61: 335-49.

3 Baker CJ. Unusual occurence of neonatal septicemia due to group G streptococcus.Pediatrics 1974, 53: 568-69.

4 Ancona RJ, Thompson TR, Ferrieri P Group G streptococcal pneumonia and sepsis ina newborn infant. J Clin Microbiol 1979, 10: 758-59.

5. Lam K, Bayer AS Serious infections due to group B streptococci. Report of 15 caseswith in vitro-in vivo correlations. Am J Med 1983; 75: 561-70.

6 Nakata MM, Silvers JH, George WL Group G streptococcal arthritis. Arch Intern Med1983, 143: 1328-30.

7. Parker MT, Ball LC. Streptococci and aerococci associated with systemic infection inman J Med Microbiol 1976, 9: 275-302.

8 Blair DC, Martin DB Beta hemolytic streptococcal endocarditis: predominance ofnon-group A organisms. Am J Med Sci 1978, 276: 269-75

9 Noble JT, Tyburski MB, Burman M, Greenspan J, Tenenbaum MJ. Antimicrobialtolerance in group G streptococci. Lancet 1980; ii: 982.

10. Rolston KV, LeFrock JL, Schell RF Activity of nine antimicrobial agents againstLancefield group C and group G streptococci. Antimicrob Agents Chemother 1982;22: 930-32.

aminoglycoside should be considered. Where for some reasonbeta-lactam agents cannot be used, vancomycin is probablythe most suitable alternative.

In addition to causing serious infections in individualsgroup G streptococci can occasionally cause outbreaks ofinfection. Hitherto there has been no typing system for theinvestigation of these outbreaks. Work in progress at theCentral Public Health Laboratory, Colindale, has shownconsiderable success with a typing scheme based on T proteinantigens present on the cell surface.

VACUUM VERSUS FORCEPS

IN current British obstetric practice about one in ten

cephalic vaginal deliveries is completed with instruments.Obstetric forceps are usually employed. Considerable force ispossible. Good anaesthesia is required and the operator mustbe patient and restrained if the risk of serious trauma tomother or baby is to be avoided. The alternative instrument isthe vacuum extractor or ventouse. Much less force is possibleand a near-natural delivery can often be achieved. Its use isacknowledged to entail less risk of serious trauma to themother but there are doubts about its efficacy in posteriorpositions of the occiput and the speed with which delivery ispossible in cases of fetal distress. The baby is always bornwith an unsightly lump on its head, and haematomaformation is more likely if there has been previous fetal scalpblood sampling 1 or scalp electrode application.2Furthermore, the cases of intracranial haemorrhage, cerebralirritation, and scalp laceration reported by Huntingford3with first-stage use of the vacuum extractor over 20 years agoare still not forgotten.Vacca et al4 have published the results of the first British

randomised comparison of "an intention to deliver with thevacuum extractor" with "an intention to deliver with

forceps" in the second stage of labour. The gentler nature ofvacuum extraction for the mother is confirmed: maternal

trauma, use of analgesia, and blood loss at delivery were sig-nificantly less than with forceps delivery, especially whenthere was a malposition of the occiput. Possibly because of theuse of Bird’s occipito-posterior vacuum cups the failure ratewas only 13%. Vacuum extraction was quicker than forcepsdelivery in cases with fetal distress. The failed forceps ratewas 10%. Readiness to accept failure may have contributed tothe virtual absence of serious neonatal morbidity in bothgroups of 152 patients. Only mild neonatal jaundice wassignificantly more common after vacuum extraction.

Fundoscopy and ultrasonic scanning for intracranial

haemorrhage were not included in the examination of thenewborn. The more experienced obstetricians left 72% ofvacuum extractions to the least experienced doctors whileundertaking 60% of forceps deliveries themselves. Thinkwhat the results might have been had this distribution of casesbeen the other way round. British obstetricians shouldexamine how much of their preference for forceps delivery isdue to tradition and training and whether they have givenvacuum extraction all the credit it deserves.

1. Roberts IF, Store M. Fetal haemorrhage: Complications of vacuum extractor after fetalblood sampling. Am J Obstet Gynecol 1978; 132: 109.

2 D’Souza SW, Black P, MacFarlane T, Richards B. Fetal scalp damage and neonataljaundice: A risk of routine fetal scalp electrode monitoring. J Obstet Gynaecol 1982,2: 161-64

3 Huntingford PJ. The vacuum extractor in the treatment of delay in the first stage oflabour Lancet 1961, ii 1054-57.

4. Vacca A, Grant A, Wyatt G, Chalmers I Portsmouth operative delivery trial Br JObstet Gynaecol 1983, 90: 1107-12

5. Bird GC The importance of flexion in vacuum extraction delivery. Br J ObstetGynaecol 1976, 83: 194-200.