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Streptococcal infection in a regional burns centre and a plastic surgery unit
Journal of Ilospital
Infection (1984) 5, 63 69
Streptococcal
M. Whitby, University
* Department
infection in a regional burns and a plastic surgery unit
J. D. Sleigh,
W. Reid, * I. McGregor*
Ihpurtment of Ih+riology, of Suvger>l, Hoval Infirmary,
+ Streptococcus
Royal.
centre
and G. Colman-jInfirmavy,
Glasgoz0
Glasgow and Plastic Surgery Unit, Cann-iesburn Hospital, Glasgow Reference Unit, Ikision of IIospital Infection, Central Public Health Laboratory, Colindule
Summary: An outbreak of infection due to group A streptococci of M-type 49 involved first a regional burns centre followed by spread to the intensive care ward of the plastic surgery unit in an associated hospital. Eleven patients and two staff were involved: two of the infected patients developed septicaemia. Serological tests demonstrated marked antibody response to LISAase B(ADB) and there were lesser reactions to other extracellular streptococcal products. Screening of patients and staff identified the likely source of the epidemic which was rapidly controlled by penicillin prophylaxis and other measures.
Introduction Infection with Streptococcus pyogenes was a serious and virtually inevitable complication of burns until the 1940s (Cruickshank, 1935). Since then, there has been a dramatic reduction in such infections following the pioneering work of Colcbrook (Colebrook, Duncan and Ross, 1948) who introduced aseptic methods for patient management and advocated the use of antimicrobial prophylaxis. Only occasional epidemics are now recorded in burns units (Wormald, 1970; Watson and Dowsett, 1976). ‘I’his paper describes an outbreak with a virulent and highly communicable group A streptococcus which led to colonization and infection of patients in a regional burns centre. ‘l’ransfer of an infected patient from the centre introduced the streptococcus into the intensive care area of the associated plastic surgery unit, and this was followed by the spread of infection to other patients.
The units
involved
The regional burns centre for the West of Scotland is situated within Glasgow Royal Infirmary. The building, which is not purpose built, accommodates 19 patients in single cubicles and open four-bedded wards. There is no special ventilation system apart from an extraction fan in the
M. Whitby
64
et al.
room used for changing dressings. The patients are encouraged to mix freely in an endeavour to minimize the psychological disturbances which commonly follow severe burns. Burns in adults and children arc treated routinely with local antimicrobials, usually chlorhexidine and silver sulphadiazine. Hacteriological swabs from the burns of all patients in the unit are taken at weekly intervals. Patients from whom streptococci of Groups-A, C or G are recovered are given a short course of either oral penicillin or erythromycin. With this exception, oral or parenteral antibiotics arc administered only to patients thought to have a systemic infection. The major plastic surgery unit for the West of Scotland is at Canniesburn Hospital, some 6 miles from the Royal Infirmary. It shares medical staff with the burns unit. ‘l’he unit has an 11-bedded ward reserved for patients requiring intensive postoperative care and this area consists of three single cubicles and two four-bedded wards. The
outbreak
The number of patients per week in the burns unit from whom group A streptococci were isolated during the period September 1982 to April 1983 is shown in Figure 1. It should be noted that it is often difficult, if not impossible, to distinguish between colonization and infection of a burn with a group A streptococcus or, indeed, with other bacteria. In late November 1982, the number of colonized patients detected by routine screening rose sharply and the consultant surgeon noted that skin grafts in two of his patients (AR, CL, ‘I’able I) had failed. Roth grafts had clinical features suggestive of failure due to streptococcal infection and this
IO
Sept/Oct
I
Nov/Dec
I
Jan/Feb
1982
Figure strain;
1. Streptococcal u, not typed.
isolations
from routine
I
Mar/Apr
I
1983
burns screening.
n , M49 strain; 3, not X145)
Streptococci Table
I. Paticvts
Patients and staff .~.. Burns unit Patients AI3 CL SD RF
~-
in Burns
mtd stczjjf infected
Age
or colonized
Weeks since admission
with
Site of isolation
Surgery
Group
240 80 50 800
800 700 1600 2000
5 12 512 128 256
30
140
2000
2.56
: 2.5
220 50 200
5600 5 00 1200
512 1024
160
400
236
80 220
x00 6400
128 2048
50
600
128
180
230
256
Stafr WMCC
24
-
‘I’hroat
53 21
<1
-
76
Blood Blood Wound ‘I’hroat ‘I’hroat Throat
-
WI>
OF
12 8 43 5
2 26 3 25
Plastic unit
( 7’14 M49
AI-IT (SR<128
3x 78 10 51
2
A streptococci
Serology* ADB (SR<400) .~-
ANP SW nr,
i
6.5
Units
Hut-n AS0 (“w) (SK<200 ~-..
Burn Burn Burn Burn sose; throat Burn Burn Burn Throat
AMCI,
22 29 40 48
and Plastic
t)
surgery
Staff
AMP
19
*SR - normal levels; AS0 = antistreptolysin
titre; AI>R = DSAase;
Al II 7 hyaluronidase.
was confirmed by culture. Within the next 48 h, two patients in the intensive care area of the plastic surgery unit became clinically septicaemic shortly after extensive head and neck surgery. Group A streptococci were isolated from blood cultures of both patients. ‘l’hese observations suggested a possible streptococcal epidemic with cross-infection between the hospitals. Investigations
and plan
of control
A meeting of senior clinical, nursing and bacteriology staff was arranged the following measures were immediately implemented.
and
(i) All patients in both units had swabs taken from nose, throat and burn or wound site. (ii) All medical and nursing staff of both units had swabs taken from the nose and throat. So staff member recalled either a recent sore throat or a septic skin lesion. (iii) All staff and all patients (except those with septicaemia) from whom group A streptococci were isolated were given a single dose of crystalline
66
M. Whitby
et al.
penicillin G (1 mega unit) intramuscularly followed by a 10 day course of oral penicillin V (2 g per day). (iv) Carriers among the staff were excluded from duty until they had completed their antibiotic treatment and bacteriological swabs failed to yield group A streptococci. (v) The burns centre could not be closed to emergency admissions so that inpatients, from whom group A streptococci were not isolated were given prophylactic oral penicillin V (2 g per day) or, if hypersensitive to penicillin, erythromycin (2 g per day), both for 5 days. ‘l’his policy was extended to newly admitted patients for the following 5 weeks. (vi) So new patients were admitted to the intensive care ward of the plastic surgery unit which was closed for 10 days. The two septicacmic patients in the unit were treated with a 10 day course of intravenous crystalline penicillin G (12 mega units/day). All group A streptococci isolated were typed at the Streptococcus Reference Cnit, Division of I Iospital Infection, Central Public Health Laboratory, Colindale. Sera were also examined there for antibodies to streptolysin 0 (ASO), DXAase II (ADR) and hyaluronidase (AI-IT). Although with movements of patients or staff, spread outside the units was possible, there was no evidence of streptococcal infection elsewhere in either hospital and more widespread screening measures were not thought appropriate. Results
A total of 11 patients and two staff, in either the burns centre or the intensive care area of the plastic surgery unit, were infected with or carried the epidemic strain (T14/M49jC)F+). ‘Ihey are listed in ‘I’able I. In the week before the outbreak, two of the patients (RF and ‘I’J- -later shown to be carriers of the epidemic strain) were admitted to the burns unit. Either patient could have introduced the streptococcus into the unit, and certainly TJ appeared responsible for the later spread of the organism to the plastic surgery unit. ‘Ihis young man was in the burns unit for 3 days, undergoing pm-operative angiography, before his transfer to the plastic surgery unit for resection of a maxillary fibro-haemangioma. Neither patient (i.e. TJ nor RF) had symptoms or signs of either pharyngitis or septic skin lesions. Of the eight patients in the burns unit from whom the M-type 49 group A streptococcus was isolated, only the two ‘graft failures’ (CI,, AR) showed any clinical evidence of infection. Each of the three patients in the plastic surgery unit were nursed in the same four-bedded cubicle of the intensive care area. Roth the index case (TJ) and another patient (WF) who was recovering from a recent radical cervical lymph node resection for recurrent melanoma patient (WD) developed septicaemia. II owever, the third postoperative
Streptococci
in Burns
and
Plastic
Surgery
Units
67
showed only bacteriological evidence of pharyngeal colonization: he had no wound sepsis. Levels of antibody to extracellular streptococcal products were determined in all 13 affected staff and patients using blood taken 4-S weeks after initial isolation of the group A streptococci (Table I). In all eight burns unit patients, the ADB titre was raised-markedly so in seven patients (Table I). Seven of the eight patients also had raised AIIT titres, but the AS0 levels were normal except in two patients in whom they were minimally elevated. Patient RF was unusual in that the AS0 titre was markedly raised. However, this may have resulted from a subclinical pharyngitis in this patient who, in addition to having his burns colonized with the type 49 strain, also had his nasopharynx colonized with a second streptococcal strain (1’8/25/Impl9/M - lOI;-). Environmental investigation by swabbing and settle plates failed, in both units, to isolate any group A streptococci. I;igure 1 shows the level of streptococcal colonization in burns patients before the outbreak, during the period of prophylaxis and for 3 months thereafter. Although the number of positive cultures has declined since the epidemic, eight of the 11 streptococci isolated in the last 3 months have been identified as M type 49. There has been no clinical evidence of streptococcal disease in any patient during this period. Discussion
Until the late 197Os, M type 49 was very uncommon in the UK. However, it is, at present, the most common serotype in recent outbreaks recorded in meat workers (Morris, 1981), a psychiatric hospital (Sicholls, 1983) and a farming community (Barnham, 1983). It is one of a limited range of serotypes capable of colonizing and infecting both skin and nasopharynx. The fact that eight of the 11 streptococci isolated from burns unit patients in the 3 months following the end of antibiotic prophylaxis are of the epidemic strain, suggests that type M49 streptococcus has become resident in the burns unit. Either the strain has persisted in the unit or, alternatively, been reintroduced after penicillin administration was stopped. However, we have been unable to detect an environmental reservoir. Tf one exists, it may have been present during the period of penicillin prophylaxis or even before the epidemic. The antibody response to streptococcal infection and colonization in burns patients has not been extensively studied. Widdowson and Wormald (1981) investigated a group of 33 patients whose burns were either colonized or infected with streptococci. ‘l’hey reported a marked response in ADB levels but much lower titres for AS0 and AHT. Our own patients show a similar serological pattern, though the reasons for the differential response of ASO, AHT and AI1B remain unclear. Denny, Perry and Wannamaker (1957) demonstrated that early antibiotic treatment reduced AS0 and type-specific
68
M. Whitby
et al.
antibody formation after streptococcal infection. Although all of our burns patients were treated with prolonged oral penicillin, in every case, growth of the initial isolate of streptococci was profuse, and, in such a situation, it is unlikely that subsequent chemotherapy had much influence on antibody response. It is interesting that, of the four individuals, two staff (WMcC, AMP) and two patients (DD, WD), with nasopharyngeal carriage of M-type 49, only the two patients showed a significant ADH titre and neither showed the expected concomitant AS0 titre rise. ‘I’he oftrepeated explanation of poor AS0 response in skin infection is that cholesterol and skin lipids depress antigenicity of streptolysin-0, but this does not hold in throat infections (Kaplan and Wannamaker, 1976). In all our patients and staff, blood for serology was collected 4-5 weeks after the isolation of streptococci when the AS0 response could have been expected to be maximal. ‘rhe possible strategies for control of this outbreak were limited by our inability to restrict admissions to the Regional Burns Centre or to isolate individual patients. Similarly, it is difficult for a plastic surgery unit treating patients for malignancy particularly of the head and neck, to function without an intensive care area. In this situation, identification and treatment of carriers together with mass prophylaxis of other patients seemed a logical approach. It has been suggested that penicillin is inappropriate for the eradication of streptococci from burns because of the P-lactamase produced by the associated flora (I,owbury et al., 1982) but this did not prove a problem in any of our patients. Although asymptomatic nasop,haryngeal carriers arc unlikely to be a significant source of infection, it was felt prudent to treat all carriers and to exclude them from ward duties until bacteriological clearance had been confirmed. Since an environmental reservoir of the streptococcus could not be demonstrated, no specific terminal disinfection (apart from routine domestic cleaning) was carried out. Others (Watson and Dowsett, 1976), however, have advocated terminal disinfection in similar situations. We believe our experience has confirmed the usefulness of routine screening swabs from lesions and would advocate their use in every patient in a burns unit, on admission, and then at weekly intervals. A change in the level of colonization is a matter of concern and an indication for further investigation. Isolation of patients and restriction of admission are important control measures but they are often impractical in a large outbreak, particularly if a highly specialized ward is involved. Rapid identification of carriers, who should be treated promptly, together with short term mass prophylaxis of other susceptible patients appears to be an effective alternative. While streptococcal infection is now uncommon in burns units, once established, its potential for epidemic spread should never be forgotten.
Streptococci
in Burns
and
Plastic
Surgery
Units
69
References Barnham, XI. (1983). Streptocaccal infection in an arable farming community. Comm~~nicahle Diseases Report 83(12), 3. Colebrook., L., Duncan, J. M. & Ross, W. I’. D. (1948). The control of infection in burns. Imzcet 1, 893-895. Cruikshank, R. (1935). Th e h‘dc t erial infection of burns.~ozrrnal of Pathology and E’actwiolqqy 41, 267 271. Denny, 1;. W., Perry, W. D. & Wannamaker, 1,. W. (1957). Type specific streptococcal antibody. Journal of Clinical Imestigation 36, 1092-l 099. Kaplan, E. L. & Wannamaker, L. W. (1976). Suppression of the antistreptolysin 0 response by cholesterol and lipid extracts of rabbit skin. Journal of Experimental Medicine 144, 754 767. I,owhury, E. J. L., Ayliffe, <;. A. J., <;eddes, A. M. & Williams, J. I>. (1982). In Control of ITospitul Irlfection p. 250. Chapman and Hall, London. Morris, C. A. (1981). Group A streptococcal infections in meat workers. Comnzrnicahle Diseases Report 82(16), 4. Sicholls, M. W. S. (.1983). Streptococcal infection in a psychiatric hospital. Communicable Diseases Report 83(01), 4. Watson, J. & Dowsett, R. G. (1976). Streptococcal and staphylococcal infection in a burns and plastic surgery unit. Communicable IAseases Report 76(74), 3. Widdowson, J. I’. & Wormald, I’. J. (1981). Streptococcal antibodies in patients with burn injuries. ‘Journal of Hygiene, Cambridge 86, 265 -273. Wormald, I’. J. (1970). The effect of a changed environment on bacterial colonization in an established burns ccntrc. ~ooz~mal of Hygiene, Cambridge 68, 633 645.
Infection (1984) 5, 63 69
Streptococcal
M. Whitby, University
* Department
infection in a regional burns and a plastic surgery unit
J. D. Sleigh,
W. Reid, * I. McGregor*
Ihpurtment of Ih+riology, of Suvger>l, Hoval Infirmary,
+ Streptococcus
Royal.
centre
and G. Colman-jInfirmavy,
Glasgoz0
Glasgow and Plastic Surgery Unit, Cann-iesburn Hospital, Glasgow Reference Unit, Ikision of IIospital Infection, Central Public Health Laboratory, Colindule
Summary: An outbreak of infection due to group A streptococci of M-type 49 involved first a regional burns centre followed by spread to the intensive care ward of the plastic surgery unit in an associated hospital. Eleven patients and two staff were involved: two of the infected patients developed septicaemia. Serological tests demonstrated marked antibody response to LISAase B(ADB) and there were lesser reactions to other extracellular streptococcal products. Screening of patients and staff identified the likely source of the epidemic which was rapidly controlled by penicillin prophylaxis and other measures.
Introduction Infection with Streptococcus pyogenes was a serious and virtually inevitable complication of burns until the 1940s (Cruickshank, 1935). Since then, there has been a dramatic reduction in such infections following the pioneering work of Colcbrook (Colebrook, Duncan and Ross, 1948) who introduced aseptic methods for patient management and advocated the use of antimicrobial prophylaxis. Only occasional epidemics are now recorded in burns units (Wormald, 1970; Watson and Dowsett, 1976). ‘I’his paper describes an outbreak with a virulent and highly communicable group A streptococcus which led to colonization and infection of patients in a regional burns centre. ‘l’ransfer of an infected patient from the centre introduced the streptococcus into the intensive care area of the associated plastic surgery unit, and this was followed by the spread of infection to other patients.
The units
involved
The regional burns centre for the West of Scotland is situated within Glasgow Royal Infirmary. The building, which is not purpose built, accommodates 19 patients in single cubicles and open four-bedded wards. There is no special ventilation system apart from an extraction fan in the
M. Whitby
64
et al.
room used for changing dressings. The patients are encouraged to mix freely in an endeavour to minimize the psychological disturbances which commonly follow severe burns. Burns in adults and children arc treated routinely with local antimicrobials, usually chlorhexidine and silver sulphadiazine. Hacteriological swabs from the burns of all patients in the unit are taken at weekly intervals. Patients from whom streptococci of Groups-A, C or G are recovered are given a short course of either oral penicillin or erythromycin. With this exception, oral or parenteral antibiotics arc administered only to patients thought to have a systemic infection. The major plastic surgery unit for the West of Scotland is at Canniesburn Hospital, some 6 miles from the Royal Infirmary. It shares medical staff with the burns unit. ‘l’he unit has an 11-bedded ward reserved for patients requiring intensive postoperative care and this area consists of three single cubicles and two four-bedded wards. The
outbreak
The number of patients per week in the burns unit from whom group A streptococci were isolated during the period September 1982 to April 1983 is shown in Figure 1. It should be noted that it is often difficult, if not impossible, to distinguish between colonization and infection of a burn with a group A streptococcus or, indeed, with other bacteria. In late November 1982, the number of colonized patients detected by routine screening rose sharply and the consultant surgeon noted that skin grafts in two of his patients (AR, CL, ‘I’able I) had failed. Roth grafts had clinical features suggestive of failure due to streptococcal infection and this
IO
Sept/Oct
I
Nov/Dec
I
Jan/Feb
1982
Figure strain;
1. Streptococcal u, not typed.
isolations
from routine
I
Mar/Apr
I
1983
burns screening.
n , M49 strain; 3, not X145)
Streptococci Table
I. Paticvts
Patients and staff .~.. Burns unit Patients AI3 CL SD RF
~-
in Burns
mtd stczjjf infected
Age
or colonized
Weeks since admission
with
Site of isolation
Surgery
Group
240 80 50 800
800 700 1600 2000
5 12 512 128 256
30
140
2000
2.56
: 2.5
220 50 200
5600 5 00 1200
512 1024
160
400
236
80 220
x00 6400
128 2048
50
600
128
180
230
256
Stafr WMCC
24
-
‘I’hroat
53 21
<1
-
76
Blood Blood Wound ‘I’hroat ‘I’hroat Throat
-
WI>
OF
12 8 43 5
2 26 3 25
Plastic unit
( 7’14 M49
AI-IT (SR<128
3x 78 10 51
2
A streptococci
Serology* ADB (SR<400) .~-
ANP SW nr,
i
6.5
Units
Hut-n AS0 (“w) (SK<200 ~-..
Burn Burn Burn Burn sose; throat Burn Burn Burn Throat
AMCI,
22 29 40 48
and Plastic
t)
surgery
Staff
AMP
19
*SR - normal levels; AS0 = antistreptolysin
titre; AI>R = DSAase;
Al II 7 hyaluronidase.
was confirmed by culture. Within the next 48 h, two patients in the intensive care area of the plastic surgery unit became clinically septicaemic shortly after extensive head and neck surgery. Group A streptococci were isolated from blood cultures of both patients. ‘l’hese observations suggested a possible streptococcal epidemic with cross-infection between the hospitals. Investigations
and plan
of control
A meeting of senior clinical, nursing and bacteriology staff was arranged the following measures were immediately implemented.
and
(i) All patients in both units had swabs taken from nose, throat and burn or wound site. (ii) All medical and nursing staff of both units had swabs taken from the nose and throat. So staff member recalled either a recent sore throat or a septic skin lesion. (iii) All staff and all patients (except those with septicaemia) from whom group A streptococci were isolated were given a single dose of crystalline
66
M. Whitby
et al.
penicillin G (1 mega unit) intramuscularly followed by a 10 day course of oral penicillin V (2 g per day). (iv) Carriers among the staff were excluded from duty until they had completed their antibiotic treatment and bacteriological swabs failed to yield group A streptococci. (v) The burns centre could not be closed to emergency admissions so that inpatients, from whom group A streptococci were not isolated were given prophylactic oral penicillin V (2 g per day) or, if hypersensitive to penicillin, erythromycin (2 g per day), both for 5 days. ‘l’his policy was extended to newly admitted patients for the following 5 weeks. (vi) So new patients were admitted to the intensive care ward of the plastic surgery unit which was closed for 10 days. The two septicacmic patients in the unit were treated with a 10 day course of intravenous crystalline penicillin G (12 mega units/day). All group A streptococci isolated were typed at the Streptococcus Reference Cnit, Division of I Iospital Infection, Central Public Health Laboratory, Colindale. Sera were also examined there for antibodies to streptolysin 0 (ASO), DXAase II (ADR) and hyaluronidase (AI-IT). Although with movements of patients or staff, spread outside the units was possible, there was no evidence of streptococcal infection elsewhere in either hospital and more widespread screening measures were not thought appropriate. Results
A total of 11 patients and two staff, in either the burns centre or the intensive care area of the plastic surgery unit, were infected with or carried the epidemic strain (T14/M49jC)F+). ‘Ihey are listed in ‘I’able I. In the week before the outbreak, two of the patients (RF and ‘I’J- -later shown to be carriers of the epidemic strain) were admitted to the burns unit. Either patient could have introduced the streptococcus into the unit, and certainly TJ appeared responsible for the later spread of the organism to the plastic surgery unit. ‘Ihis young man was in the burns unit for 3 days, undergoing pm-operative angiography, before his transfer to the plastic surgery unit for resection of a maxillary fibro-haemangioma. Neither patient (i.e. TJ nor RF) had symptoms or signs of either pharyngitis or septic skin lesions. Of the eight patients in the burns unit from whom the M-type 49 group A streptococcus was isolated, only the two ‘graft failures’ (CI,, AR) showed any clinical evidence of infection. Each of the three patients in the plastic surgery unit were nursed in the same four-bedded cubicle of the intensive care area. Roth the index case (TJ) and another patient (WF) who was recovering from a recent radical cervical lymph node resection for recurrent melanoma patient (WD) developed septicaemia. II owever, the third postoperative
Streptococci
in Burns
and
Plastic
Surgery
Units
67
showed only bacteriological evidence of pharyngeal colonization: he had no wound sepsis. Levels of antibody to extracellular streptococcal products were determined in all 13 affected staff and patients using blood taken 4-S weeks after initial isolation of the group A streptococci (Table I). In all eight burns unit patients, the ADB titre was raised-markedly so in seven patients (Table I). Seven of the eight patients also had raised AIIT titres, but the AS0 levels were normal except in two patients in whom they were minimally elevated. Patient RF was unusual in that the AS0 titre was markedly raised. However, this may have resulted from a subclinical pharyngitis in this patient who, in addition to having his burns colonized with the type 49 strain, also had his nasopharynx colonized with a second streptococcal strain (1’8/25/Impl9/M - lOI;-). Environmental investigation by swabbing and settle plates failed, in both units, to isolate any group A streptococci. I;igure 1 shows the level of streptococcal colonization in burns patients before the outbreak, during the period of prophylaxis and for 3 months thereafter. Although the number of positive cultures has declined since the epidemic, eight of the 11 streptococci isolated in the last 3 months have been identified as M type 49. There has been no clinical evidence of streptococcal disease in any patient during this period. Discussion
Until the late 197Os, M type 49 was very uncommon in the UK. However, it is, at present, the most common serotype in recent outbreaks recorded in meat workers (Morris, 1981), a psychiatric hospital (Sicholls, 1983) and a farming community (Barnham, 1983). It is one of a limited range of serotypes capable of colonizing and infecting both skin and nasopharynx. The fact that eight of the 11 streptococci isolated from burns unit patients in the 3 months following the end of antibiotic prophylaxis are of the epidemic strain, suggests that type M49 streptococcus has become resident in the burns unit. Either the strain has persisted in the unit or, alternatively, been reintroduced after penicillin administration was stopped. However, we have been unable to detect an environmental reservoir. Tf one exists, it may have been present during the period of penicillin prophylaxis or even before the epidemic. The antibody response to streptococcal infection and colonization in burns patients has not been extensively studied. Widdowson and Wormald (1981) investigated a group of 33 patients whose burns were either colonized or infected with streptococci. ‘l’hey reported a marked response in ADB levels but much lower titres for AS0 and AHT. Our own patients show a similar serological pattern, though the reasons for the differential response of ASO, AHT and AI1B remain unclear. Denny, Perry and Wannamaker (1957) demonstrated that early antibiotic treatment reduced AS0 and type-specific
68
M. Whitby
et al.
antibody formation after streptococcal infection. Although all of our burns patients were treated with prolonged oral penicillin, in every case, growth of the initial isolate of streptococci was profuse, and, in such a situation, it is unlikely that subsequent chemotherapy had much influence on antibody response. It is interesting that, of the four individuals, two staff (WMcC, AMP) and two patients (DD, WD), with nasopharyngeal carriage of M-type 49, only the two patients showed a significant ADH titre and neither showed the expected concomitant AS0 titre rise. ‘I’he oftrepeated explanation of poor AS0 response in skin infection is that cholesterol and skin lipids depress antigenicity of streptolysin-0, but this does not hold in throat infections (Kaplan and Wannamaker, 1976). In all our patients and staff, blood for serology was collected 4-5 weeks after the isolation of streptococci when the AS0 response could have been expected to be maximal. ‘rhe possible strategies for control of this outbreak were limited by our inability to restrict admissions to the Regional Burns Centre or to isolate individual patients. Similarly, it is difficult for a plastic surgery unit treating patients for malignancy particularly of the head and neck, to function without an intensive care area. In this situation, identification and treatment of carriers together with mass prophylaxis of other patients seemed a logical approach. It has been suggested that penicillin is inappropriate for the eradication of streptococci from burns because of the P-lactamase produced by the associated flora (I,owbury et al., 1982) but this did not prove a problem in any of our patients. Although asymptomatic nasop,haryngeal carriers arc unlikely to be a significant source of infection, it was felt prudent to treat all carriers and to exclude them from ward duties until bacteriological clearance had been confirmed. Since an environmental reservoir of the streptococcus could not be demonstrated, no specific terminal disinfection (apart from routine domestic cleaning) was carried out. Others (Watson and Dowsett, 1976), however, have advocated terminal disinfection in similar situations. We believe our experience has confirmed the usefulness of routine screening swabs from lesions and would advocate their use in every patient in a burns unit, on admission, and then at weekly intervals. A change in the level of colonization is a matter of concern and an indication for further investigation. Isolation of patients and restriction of admission are important control measures but they are often impractical in a large outbreak, particularly if a highly specialized ward is involved. Rapid identification of carriers, who should be treated promptly, together with short term mass prophylaxis of other susceptible patients appears to be an effective alternative. While streptococcal infection is now uncommon in burns units, once established, its potential for epidemic spread should never be forgotten.
Streptococci
in Burns
and
Plastic
Surgery
Units
69
References Barnham, XI. (1983). Streptocaccal infection in an arable farming community. Comm~~nicahle Diseases Report 83(12), 3. Colebrook., L., Duncan, J. M. & Ross, W. I’. D. (1948). The control of infection in burns. Imzcet 1, 893-895. Cruikshank, R. (1935). Th e h‘dc t erial infection of burns.~ozrrnal of Pathology and E’actwiolqqy 41, 267 271. Denny, 1;. W., Perry, W. D. & Wannamaker, 1,. W. (1957). Type specific streptococcal antibody. Journal of Clinical Imestigation 36, 1092-l 099. Kaplan, E. L. & Wannamaker, L. W. (1976). Suppression of the antistreptolysin 0 response by cholesterol and lipid extracts of rabbit skin. Journal of Experimental Medicine 144, 754 767. I,owhury, E. J. L., Ayliffe, <;. A. J., <;eddes, A. M. & Williams, J. I>. (1982). In Control of ITospitul Irlfection p. 250. Chapman and Hall, London. Morris, C. A. (1981). Group A streptococcal infections in meat workers. Comnzrnicahle Diseases Report 82(16), 4. Sicholls, M. W. S. (.1983). Streptococcal infection in a psychiatric hospital. Communicable Diseases Report 83(01), 4. Watson, J. & Dowsett, R. G. (1976). Streptococcal and staphylococcal infection in a burns and plastic surgery unit. Communicable IAseases Report 76(74), 3. Widdowson, J. I’. & Wormald, I’. J. (1981). Streptococcal antibodies in patients with burn injuries. ‘Journal of Hygiene, Cambridge 86, 265 -273. Wormald, I’. J. (1970). The effect of a changed environment on bacterial colonization in an established burns ccntrc. ~ooz~mal of Hygiene, Cambridge 68, 633 645.