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Year : 2004  |  Volume : 22  |  Issue : 1  |  Page : 51--53

Neonatal outbreak of salmonella worthington in a general hospital

VA Muley, SS Pol, VB Dohe, RP Nagdawane, VP Arjunwadkar, DP Pandit, RS Bharadwaj 
 Department of Microbiology, BJ Medical College, Pune - 411 001, Maharashtra, India

Correspondence Address:
V A Muley
Department of Microbiology, BJ Medical College, Pune - 411 001, Maharashtra


This is a report of an outbreak of Salmonella worthington in neonates at Sassoon General Hospitals, Pune, which occurred during August and September 2000. A total of 148 blood, 4 CSF and 6 stool specimens were received from neonates admitted to the hospital. Salmonella worthington could be isolated from 17 clinical specimens [15 blood (10.8%), 1 CSF (25%) and 1 stool (16.6%) sample]. Environmental swabs were also processed. An attempt was made to detect carriers in health care personnel. However, no source or carrier of Salmonella worthington in the hospital environment could be identified. Intensive cleaning measures and fumigation were undertaken. All these measures succeeded in aborting the outbreak.

How to cite this article:
Muley V A, Pol S S, Dohe V B, Nagdawane R P, Arjunwadkar V P, Pandit D P, Bharadwaj R S. Neonatal outbreak of salmonella worthington in a general hospital.Indian J Med Microbiol 2004;22:51-53

How to cite this URL:
Muley V A, Pol S S, Dohe V B, Nagdawane R P, Arjunwadkar V P, Pandit D P, Bharadwaj R S. Neonatal outbreak of salmonella worthington in a general hospital. Indian J Med Microbiol [serial online] 2004 [cited 2020 Dec 1 ];22:51-53
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Full Text

Non-typhoidal salmonellae (NTS) are primary pathogens of lower animals (e.g. poultry, cows, pigs, birds, sheep etc.). They are the principal source of non-typhoid salmonellosis in humans. These bacteria usually cause infections in the first month of life often presenting as septicaemia, meningitis or deep seated pyogenic infections.[1] Various serotypes reported from neonatal infection are Salmonella typhimurium, S.anatum, S.newport, S.seftenberg etc.[2] These infections are usually transmitted from one child to the other in a neonatal nursery either from the environment or by a health care worker who may be a carrier.3 These carriers may intermittently excrete strains of Salmonella in their faeces several months after infection without any symptoms of disease.[3]

This report describes an outbreak of Salmonella worthington in a general hospital, Pune during August and September 2000.

 Materials and methods

The outbreak occurred between 1st August and 30th September 2000 in the neonatal intensive care unit and labour ward side room. One hundred and forty-eight blood, four CSF and six stool specimens from neonates were received during this period. In the laboratory, all samples were processed by standard protocol.4 Blood and CSF samples were plated on blood agar, chocolate agar, and MacConkey's agar. Stool samples were plated on Wilson and Blair medium. The colonies obtained were identified as NTS by standard biochemical tests.[4] The antibiotic sensitivity testing of all the isolates was performed by Kirby-Bauer method.[5] All isolates showed agglutination with Salmonella polyvalent O antisera. For further serotype determination isolates were submitted to the National reference center for Salmonella and Escherichia at Central Research Institute, Kasauli.

On realization that we had an outbreak in the neonates, the hospital infection control committee was informed and samples from the labour ward side room and the neonatal intensive care unit were collected. A total of 34 environmental samples were processed including swabs from baby incubators, baby cots, trays and baby linen. Suction machines, soap, water and milk in all these areas were also sampled. Mothers of all babies and all the staff handling the neonates were screened for their carrier status. All samples were processed by standard technique.[4]


The first case was reported on 1st August with high-grade fever, refusal to feeds and lethargy. Over the next two months, other neonates were infected. Salmonellae could be isolated from 17 clinical specimens [15 blood, 1 CSF and 1 stool sample] from 16 neonates. In our laboratory they were diagnosed as NTS. These isolates were confirmed to be Salmonella worthington (antigenic structure 13,23:z:l,w) at the reference center. All infected babies presented clinically with septicaemia. In addition, one had meningitis and another had gastroenteritis. In the baby with meningitis, Salmonella worthington could be isolated from blood as well as from CSF.

All these babies were in the age group of 1-10 days. 81.3% of infected babies had low birth weight and 31.2% babies were preterm babies. Out of these, 10 babies (62.5%) expired within 3-4 days after admission to the neonatal ICU.

The sensitivity pattern of all the isolates was similar. All the 17 strains of S.worthington were sensitive only to amikacin and ciprofloxacin and resistant to amoxycillin, cefotaxime, chloramphenicol, gentamicin and norfloxacin. No source of Salmonella could be traced in the environment. No carriers were detected amongst the nurses, doctors, and baby handlers from neonatal ICU and labour room nursery.


S.worthington is an unusual isolate having antigenic structure 13,23:z:1,w. It belongs to serogroup G. It was isolated for the first time in 1937 from animals. Since then it has been isolated from other animal and human sources.[6] Newborn babies, especially premature, appear to be more susceptible than the population at large. In Africa, S.worthington has been reported as an agent of nosocomial infections in the labour room and nurseries for premature babies.[1] S.worthington is responsible for causing the outbreaks in neonatal nurseries because the neonates are immuno-compromised and the close proximity with each other facilitates the spread of infection. The first documented outbreak with this organism is in 1976 from Hong Kong where 18 neonates were involved.[7] Table summarizes the reported neonatal outbreaks caused by S. worthington.

In the present outbreak, 10 out of 16 babies died within 3 to 4 days of admission, mortality being 62.5%. S.worthington seems to be associated with high mortality as seen in other reported outbreaks from India, mortality ranging from 50 to 85.7% [Table]. The multi-drug resistance of the isolates could have accounted for high mortality in the present outbreak. Multi-drug resistant S.worthinngton strains have been reported by Mahajan et al from Mumbai.[6]

Low birth weight babies are particularly susceptible to overwhelming bacterial infection.[10] In the present outbreak 81.3% babies, were having low birth weights though only five babies were preterm.

The present outbreak of salmonellosis raised some important questions about infective dose, mode of transmission, and the exact source of origin of this organism. [Table] enlists the various sources of origin of infection in documented outbreaks. However, no source could be traced in the present outbreak inspite of considerable effort.

Intensive cleaning measures were instituted and fumigation of the neonatal intensive care unit was undertaken. The staff directly handling the babies was given an antibiotic therapy for treating undetected carriers and rotation of staff was also undertaken. With the institution of these measures, the outbreak was controlled.

To prevent such outbreaks in neonatal nurseries it is important to enforce the hand washing and restriction of visitors. Since neonatal nurseries are prone to high mortality, this is an area where ongoing microbiological surveillance should be instituted.


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